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This is the quickest and simplest way to make coffee just the problem is coffee beans for your coffee machines must be ground just minutes before you use them because some of the flavors dry off very quickly and diminish the final product. In other words, having the beans ground at the store is not a viable option for taste.

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In order to make coffee the bean have to be grounded before using them. Following are few options.

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Self Cleaning If the self clean light begins to flash when the coffeemaker is turned on, it is telling you that the calcium buildup is interfering with the functioning of your coffeemaker and the flavor of your coffee. To clean, fill the water reservoir to capacity with a mixture of ¹/³ white vinegar and ²/³ water. Press the Self Clean button. When the self clean light glows, turn the coffeemaker on by pressing the flip switch to On. The self clean light will shine steadily. The coffeemaker is now in self clean mode. One cycle should be sufficient  to adequately clean the coffeemaker. When the cycle is completed and the five beeps sound, the coffeemaker will shut off. Turn the coffeemaker on to see if the self clean  light continues to fl ash. If it does, turn it off and then repeat the cleaning procedure with a fresh solution of vinegar and water. If the self clean light no longer flashes, turn the coffeemaker off and then run one cycle of fresh cold water through the unit before using the unit again to brew coffee. Notes on the Self Clean Function Pressing the Self Clean button cancels all other settings. If it is pressed accidentally, press it again to return the coffeemaker to all its previous settings. Pressing On/Off will also exit the self clean mode and turn the coffeemaker off.

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Cuisinart Coffee Maker Self Clean Feature

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Coffee tasting bitter lately? Give coffee buildup a big send-off with this quick, easy method for cleaning a coffee maker and carafe with vinegar and water. You'll be enjoying a fresh, delicious cup of java before you know it.

By Jan Soults Walker

Your coffee maker might not be as clean as you think. Some of the warning signs of a dirty coffee maker are clear: Oily sludge and mineral buildup eventually form on your coffee maker and pot, creating stains, gumming up the brewing process, and producing bitter-tasting brew. But the germs and bacteria you can't see might pose an even bigger problem. One study by NSF International cites coffee makers as the fifth germiest place in your home, with half of the reservoirs tested containing yeast and mold. These organisms can cause allergic reactions or even infections, so without proper cleaning, your coffee maker could make you sick.

The good news is that you can learn how to clean a coffee pot to look sparkling and (nearly) new in just a few easy steps. Here's how to clean your classic drip-style coffee maker with just vinegar and water.

We'll also show you how to descale a Keurig coffee maker -it's the same materials, just a slightly different process. No matter which kind of coffee maker you have, you'll need to set aside a little time to allow the vinegar to work, so don't do it right before hosting any coffee-loving guests.

How to Clean a Coffee Maker

What You Need

Step 1: Mix Vinegar and Water

To clean your coffee maker, begin by filling the reservoir with a mixture of half white distilled vinegar and half water. You can increase the ratio of vinegar to water if your coffee maker has a particularly nasty case of buildup. The vinegar not only sanitizes the coffee maker and carafe, but it will also dissolve any accrued mineral deposits.

Step 2: Brew and Soak

Position a filter in the basket, and turn the brewer on. About halfway through brewing, turn the coffee maker off, and allow the remaining vinegar solution to soak in the carafe and the reservoir for about 30 to 60 minutes, depending on how much buildup you need to clear away.

Step 3: Finish Cycle and Clean

Turn the coffee maker back on and allow it to complete the brewing cycle. Toss the paper filter, if there is one, and pour out the vinegar solution.

Now you can flush the vinegar scent and taste from the coffee maker. Fill the reservoir with fresh water, put a filter in the basket, turn the coffee maker on, and let it complete the brewing cycle. Remove the filter, pour out the water, and repeat with clean water for a second cycle. Wipe down your coffee maker and coffee pot with a clean cloth.

How to Clean a Keurig Coffee Maker

Don't worry; cleaning your Keurig coffee maker isn't any more complicated than a traditional drip-pot version. Just as with a standard coffee maker, distilled white vinegar and water are your go-to Keurig cleaning solution.

What You Need

Keurig coffee maker

Dish liquid detergent

Towel

White distilled vinegar

Water

Empty mug

Step 1: Wash Keurig Exterior

Before you begin to unclog or descale your coffee machine, you should give the exterior a good scrubbing. The reservoir, drip tray and its cover, and the holder and funnel may be washed in the dishwasher. However, do not put the reservoir lid in the dishwasher. Alternately, place them in a sink filled with hot water and about 1 tsp. of liquid dish detergent. Let them soak 15 minutes, then rinse well and towel dry.

Step 2: Clean Keurig Interior

While the removable parts are washing or soaking, take a clean toothbrush and gently brush out any stuck coffee grinds in the K-Cup holder. While you're in there, use a damp cloth to remove any buildup. Finish the job by wiping the exterior with a cloth dampened with an all-purpose cleaner.

If you notice any limescale deposits (white crusty buildup), simply soak part of your cloth in white vinegar, apply it to the affected area, and let soak for a few minutes. Wipe again and the white marks should disappear before your eyes. Finish by re-assembling the Keurig coffee maker.

Step 3: Run Vinegar Solution

Before you start cleaning a Keurig coffee maker, make sure it has no pods in it. Place a large empty mug on the tray. Empty any water from the reservoir and remove the water filter if you have one. Refill the reservoir to the maximum line with a solution of distilled vinegar and water in a 1:1 ratio. Turn your Keurig on, select the largest cup setting, and allow the vinegar solution to run through the machine as many times as it takes for "More/Add Water" to come on. Dump out the hot liquid from the mug in a sink after each brew.

Step 4: Let Sit and Rinse Reservoir

Let the Keurig coffee maker sit for at least 30 minutes. When time's up, take out the reservoir and rinse it with water to get rid of any vinegar residue. You may have to rinse a few times.

Step 5: Run with Water

Repeat Step 1 but with plain water to rinse out the vinegar from the machine. Again, place an empty mug on the drip tray. Pour water into the reservoir up to the maximum fill line. Use the largest cup setting and allow the water to run through the machine as many times as it takes for it to empty. Now you have a clean Keurig all ready to go for your next morning brew!

Step 6: Use a Descaling Solution (Optional)

If the mineral buildup in your coffee maker is particularly heavy or taste doesn't improve, repeat the process with a manufacturer-approved descaling solution. Keurig recommends descaling every 3-6 months for best results.

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How to Clean Your Coffee Maker (And Why You Should Do It More Often)

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Coffee tasting bitter lately? Give coffee buildup a big send-off with this quick, easy method for cleaning a coffee maker and carafe with vinegar and water. You'll be enjoying a fresh, delicious cup of java before you know it. By Jan Soults Walker Your coffee maker might not be as clean as you think.

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It is cheapest and simplest

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A quantum dot display is a display device that uses quantum dots (QD), semiconductor nanocrystals which can produce pure monochromatic red, green, and blue light.

Photo-emissive quantum dot particles are used in a QD layer which uses the blue light from a backlight to emit pure basic colors which improve display brightness and color gamut by reducing light losses and color crosstalk in RGB LCD color filters, replacing traditional colored photoresists in RGB LCD color filters. This technology is used in LED-backlit LCDs, though it is applicable to other display technologies which use color filters, such as blue/UV OLED or MicroLED. LED-backlit LCDs are the main application of quantum dots, where they are used to offer an alternative to OLED displays.

Electro-emissive or electroluminiscent quantum dot displays are an experimental type of display based on quantum-dot light-emitting diodes (QD-LED; also EL-QLED, ELQD, QDEL). These displays are similar to active-matrix organic light-emitting diode (AMOLED) and MicroLED displays, in that light would be produced directly in each pixel by applying electric current to inorganic nano-particles. QD-LED displays could support large, flexible displays and would not degrade as readily as OLEDs, making them good candidates for flat-panel TV screens, digital cameras, mobile phones and handheld game consoles.

As of 2019, all commercial products, such as LCD TVs using quantum dots and branded as QLED, use photo-emissive particles. Electro-emissive QD-LED TVs exist in laboratories only, although Samsung is working to release Electro-emissive QDLED displays "in the near future", while others doubt that such QDLED displays will ever become mainstream.

Emissive quantum dot displays can achieve the same contrast as OLED and MicroLED displays with "perfect" black levels in the off state. Quantum Dot displays are capable of displaying wider color gamuts than OLEDs with some devices approaching full coverage of the BT.2020 color gamut.

The idea of using quantum dots as a light source emerged in the 1990s. Early applications included imaging using QD infrared photodetectors, light emitting diodes and single-color light emitting devices. Starting in the early 2000s, scientists started to realize the potential of developing quantum dots for light sources and displays.

QDs are either photo-emissive ( photoluminescent) or electro-emissive ( electroluminescent) allowing them to be readily incorporated into new emissive display architectures. Quantum dots naturally produce monochromatic light, so they are more efficient than white light sources when color filtered and allow more saturated colors that reach nearly 100% of Rec. 2020 color gamut.

A widespread practical application is using quantum dot enhancement film (QDEF) layer to improve the LED backlighting in LCD TVs. Light from a blue LED backlight is converted by QDs to relatively pure red and green, so that this combination of blue, green and red light incurs less blue-green crosstalk and light absorption in the color filters after the LCD screen, thereby increasing useful light throughput and providing a better color gamut.

The first manufacturer shipping TVs of this kind was Sony in 2013 as Triluminos, Sony's trademark for the technology. At the Consumer Electronics Show 2015, Samsung Electronics, LG Electronics, TCL Corporation and Sony showed QD-enhanced LED-backlighting of LCD TVs. At the CES 2017, Samsung rebranded their 'SUHD' TVs as 'QLED'; later in April 2017, Samsung formed the QLED Alliance with Hisense and TCL to produce and market QD-enhanced TVs.

Quantum dot on glass (QDOG) replaces QD film with a thin QD layer coated on top of the light-guide plate (LGP), reducing costs and improving efficiency.

Traditional white LED backlights that use blue LEDs with on-chip or on-rail red-green QD structures are being researched, though high operating temperatures negatively affect their lifespan.

QD color filter/converter (QDCF/QDCC) LED-backlit LCDs would use QD film or ink-printed QD layer with red/green sub-pixel patterned (i.e. aligned to precisely match the red and green subpixels) quantum dots to produce pure red/green light; blue subpixels can be transparent to pass through the pure blue LED backlight, or can be made with blue patterned quantum dots in case of UV-LED backlight. This configuration effectively replaces passive color filters, which incur substantial losses by filtering out 2/3 of passing light, with photo-emissive QD structures, improving power efficiency and/or peak brightness, and enhancing color purity. Because quantum dots depolarize the light, output polarizer (the analyzer) needs to be moved behind the color filter and embedded in-cell of the LCD glass; this would improve viewing angles as well. In-cell arrangement of the analyzer and/or the polarizer would also reduce depolarization effects in the LC layer, increasing contrast ratio. To reduce self-excitement of QD film and to improve efficiency, the ambient light can be blocked using traditional color filters, and reflective polarizers can direct light from QD filters towards the viewer. As only blue or UV light passes through the liquid crystal layer, it can be made thinner, resulting in faster pixel response times.

Nanosys made presentations of their photo-emissive color filter technology during 2017; commercial products were expected by 2019, though in-cell polarizer remained a major challenge. As of December 2019, issues with in-cell polarizer remain unresolved and no LCDs with QD color filters appeared on the market.

QD color filters/converters can be used with OLED or micro-LED panels, improving their efficiency and color gamut. QD-OLED panels with blue emitters and red-green color filters are researched by Samsung and TCL; as of May 2019, Samsung intends to start production in 2021. In October 2019, Samsung Display announced an investment of $10.8 billion in both research and production, with the aim to convert all their 8G panel factories to QD-OLED production during 2019-2025.

AMQLED displays will use electroluminescent QD nanoparticles functioning as Quantum-dot-based LEDs (QD-LEDs or QLEDs) arranged in an active matrix array. Rather than requiring a separate LED backlight for illumination and TFT LCD to control the brightness of color primaries, these QLED displays would natively control the light emitted by individual color subpixels, greatly reducing pixel response times by eliminating the liquid crystal layer. This technology has also been called true QLED display, and Electroluminescent quantum dots (ELQD, QDLE, EL-QLED).

The structure of a QD-LED is similar to the basic design of an OLED. The major difference is that the light emitting devices are quantum dots, such as cadmium selenide (CdSe) nanocrystals. A layer of quantum dots is sandwiched between layers of electron-transporting and hole-transporting organic materials. An applied electric field causes electrons and holes to move into the quantum dot layer, where they are captured in the quantum dot and recombine, emitting photons. The demonstrated color gamut from QD-LEDs exceeds the performance of both LCD and OLED display technologies.

Mass production of active-matrix QLED displays using ink-jet printing is expected to begin in 2020-2021. InP ( indium phosphide) ink-jet solutions are being researched by Nanosys, Nanoco, Nanophotonica, OSRAM OLED, Fraunhofer IAP, and Seoul National University, among others. As of 2019, InP based materials are still not yet ready for commercial production due to limited lifetime.

Performance of QDs is determined by the size and/or composition of the QD structures. Unlike simple atomic structures, a quantum dot structure has the unusual property that energy levels are strongly dependent on the structure's size. For example, CdSe quantum dot light emission can be tuned from red (5 nm diameter) to the violet region (1.5 nm dot). The physical reason for QD coloration is the quantum confinement effect and is directly related to their energy levels. The bandgap energy that determines the energy (and hence color) of the fluorescent light is inversely proportional to the square of the size of quantum dot. Larger QDs have more energy levels that are more closely spaced, allowing the QD to emit (or absorb) photons of lower energy (redder color). In other words, the emitted photon energy increases as the dot size decreases, because greater energy is required to confine the semiconductor excitation to a smaller volume.

Newer quantum dot structures employ indium instead of cadmium, as the latter is not exempted for use in lighting by the European Commission RoHS directive, and also because of cadmium's toxicity.

QD-LEDs are characterized by pure and saturated emission colors with narrow bandwidth, with FWHM ( full width at half maximum) in the range of 20-40 nm. Their emission wavelength is easily tuned by changing the size of the quantum dots. Moreover, QD-LED offer high color purity and durability combined with the efficiency, flexibility, and low processing cost of comparable organic light-emitting devices. QD-LED structure can be tuned over the entire visible wavelength range from 460 nm (blue) to 650 nm (red) (the human eye can detect light from 380 to 750 nm). The emission wavelengths have been continuously extended to UV and NIR range by tailoring the chemical composition of the QDs and device structure.

Quantum dots are solution processable and suitable for wet processing techniques. The two major fabrication techniques for QD-LED are called phase separation and contact-printing.

Phase separation is suitable for forming large-area ordered QD monolayers. A single QD layer is formed by spin casting a mixed solution of QD and an organic semiconductor such as TPD (N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine). This process simultaneously yields QD monolayers self-assembled into hexagonally close-packed arrays and places this monolayer on top of a co-deposited contact. During solvent drying, the QDs phase separate from the organic under-layer material (TPD) and rise towards the film's surface. The resulting QD structure is affected by many parameters: solution concentration, solvent ration, QD size distribution and QD aspect ratio. Also important is QD solution and organic solvent purity.

Although phase separation is relatively simple, it is not suitable for display device applications. Since spin-casting does not allow lateral patterning of different sized QDs (RGB), phase separation cannot create a multi-color QD-LED. Moreover, it is not ideal to have an organic under-layer material for a QD-LED; an organic under-layer must be homogeneous, a constraint which limits the number of applicable device designs.

The contact printing process for forming QD thin films is a solvent-free water-based suspension method, which is simple and cost efficient with high throughput. During the process, the device structure is not exposed to solvents. Since charge transport layers in QD-LED structures are solvent-sensitive organic thin films, avoiding solvent during the process is a major benefit. This method can produce RGB patterned electroluminescent structures with 1000 ppi (pixels-per-inch) resolution.

The overall process of contact printing:

Polydimethylsiloxane (PDMS) is molded using a silicon master.

Top side of resulting PDMS stamp is coated with a thin film of Parylene-c, a chemical-vapor deposited (CVD) aromatic organic polymer.

Parylene-c coated stamp is inked via spin-casting of a solution of colloidal QDs suspended in an organic solvent.[contradictory ]

After the solvent evaporates, the formed QD monolayer is transferred to the substrate by contact printing.

The array of quantum dots is manufactured by self-assembly in a process known as spin casting: a solution of quantum dots in an organic material is poured onto a substrate, which is then set spinning to spread the solution evenly.

Contact printing allows fabrication of multi-color QD-LEDs. A QD-LED was fabricated with an emissive layer consisting of 25- µm wide stripes of red, green and blue QD monolayers. Contact printing methods also minimize the amount of QD required, reducing costs.

Nanocrystal displays would render as much as a 30% increase in the visible spectrum, while using 30 to 50% less power than LCDs, in large part because nanocrystal displays wouldn't need backlighting. QD LEDs are 50-100 times brighter than CRT and LC displays, emitting 40,000 nits ( cd/m ²). QDs are dispersable in both aqueous and non-aqueous solvents, which provides for printable and flexible displays of all sizes, including large area TVs. QDs can be inorganic, offering the potential for improved lifetimes compared to OLED (however, since many parts of QD-LED are often made of organic materials, further development is required to improve the functional lifetime.) In addition to OLED displays, pick-and-place microLED displays are emerging as competing technologies to nanocrystal displays. Samsung has developed a method for making self-emissive quantum dot diodes with a lifetime of 1 million hours.

Other advantages include better saturated green colors, manufacturability on polymers, thinner display and the use of the same material to generate different colors.

One disadvantage is that blue quantum dots require highly precise timing control during the reaction, because blue quantum dots are just slightly above the minimum size. Since sunlight contains roughly equal luminosities of red, green and blue across the entire spectrum, a display also needs to produce roughly equal luminosities of red, green and blue to achieve pure white as defined by CIE Standard Illuminant D65. However, the blue component in the display can have relatively lower color purity and/or precision ( dynamic range) in comparison to green and red, because the human eye is three to five times less sensitive to blue in daylight conditions according to CIE luminosity function.

1. ^ "Quantum Dot Electroluminescence". evidenttech.com. Archived from the original on 16 December 2009.

2. ^ Society for Information Display, Digest of Technical Papers (9 April 2019). "Next‐Generation Display Technology: Quantum‐Dot LEDs". doi:10.1002/sdtp.10276.

3. ^ "Display - Nanoco Technologies". www.nanocotechnologies.com. Archived from the original on 23 March 2014.

4. ^ "SONY ANNOUNCES 2013 BRAVIA TVS | Sony". 8 March 2013. Archived from the original on 8 March 2013.

5. https://nccavs-usergroups.avs.org/wp-content/uploads/TFUG2017/TFUG917-1-Hartlove-Rev1.pdf

6. ^ Seth Coe; Wing-Keung Woo; Moungi Bawendi; Vladimir Bulovic (2002). "Electroluminescence from single monolayers of nanocrystals in molecular organic devices". Nature. 420 (6917): 800-803. Bibcode:2002Natur.420..800C. doi:10.1038/nature01217. PMID 12490945. S2CID 4426602.

7. ^ Kwak, Jeonghun; Lim, Jaehoon; Park, Myeongjin; Lee, Seonghoon; Char, Kookheon; Lee, Changhee (10 June 2015). "High-Power Genuine Ultraviolet Light-Emitting Diodes Based On Colloidal Nanocrystal Quantum Dots". Nano Letters. 15 (6): 3793-3799. Bibcode:2015NanoL..15.3793K. doi:10.1021/acs.nanolett.5b00392. ISSN 1530-6984. PMID 25961530.

8. ^ Coe-Sullivan, Seth; Steckel, Jonathan S.; Woo, Wing-Keung; Bawendi, Moungi G.; et al. (2005). "Large-Area Ordered Quantum Dot Monolayers via Phase Separation During Spin-Casting" (PDF). Advanced Functional Materials. 15 (7): 1117-1124. doi:10.1002/adfm.200400468. Archived from the original (PDF) on 13 May 2016.

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A quantum dot display is a display device that uses quantum dots (QD), semiconductor nanocrystals which can produce pure monochromatic red, green, and blue light.

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A plasma display panel (PDP) is a type of flat panel display that uses small cells containing plasma: ionized gas that responds to electric fields. Plasma televisions were the first large (over 32 inches diagonal) flat panel displays to be released to the public.

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Horizontal IPS

H-IPS

2007

Improves contrast ratio by twisting electrode plane layout. Also introduces an optional Advanced True White polarizing film from NEC, to make white look more natural. This is used in professional/photography LCDs.

Enhanced IPS

E-IPS

2009

Wider aperture for light transmission, enabling the use of lower-power, cheaper backlights. Improves diagonal viewing angle and further reduce response time to 5ms.

Professional IPS

P-IPS

2010

Offer 1.07 billion colors (10-bit color depth). More possible orientations per sub-pixel (1024 as opposed to 256) and produces a better true color depth.

Advanced High Performance IPS

AH-IPS

2011

Improved color accuracy, increased resolution and PPI, and greater light transmission for lower power consumption.

This is an LCD technology derived from the IPS by Boe-Hydis of Korea. Known as fringe field switching (FFS) until 2003, advanced fringe field switching is a technology similar to IPS or S-IPS offering superior performance and color gamut with high luminosity. Color shift and deviation caused by light leakage is corrected by optimizing the white gamut, which also enhances white/grey reproduction. AFFS is developed by Hydis Technologies Co., Ltd, Korea (formally Hyundai Electronics, LCD Task Force).

In 2004, Hydis Technologies Co., Ltd licensed its AFFS patent to Japan's Hitachi Displays. Hitachi is using AFFS to manufacture high end panels in their product line. In 2006, Hydis also licensed its AFFS to Sanyo Epson Imaging Devices Corporation.

Hydis introduced AFFS+ which improved outdoor readability in 2007.

It achieved pixel response which was fast for its time, wide viewing angles, and high contrast at the cost of brightness and color reproduction. Modern MVA panels can offer wide viewing angles (second only to S-IPS technology), good black depth, good color reproduction and depth, and fast response times due to the use of RTC ( Response Time Compensation) technologies. When MVA panels are viewed off-perpendicular, colors will shift, but much less than for TN panels.

There are several "next-generation" technologies based on MVA, including AU Optronics' P-MVA and AMVA, as well as Chi Mei Optoelectronics' S-MVA.

Less expensive PVA panels often use dithering and FRC, whereas super-PVA (S-PVA) panels all use at least 8 bits per color component and do not use color simulation methods.S-PVA also largely eliminated off-angle glowing of solid blacks and reduced the off-angle gamma shift. Some high-end Sony BRAVIA LCD TVs offer 10-bit and xvYCC color support, for example, the Bravia X4500 series. S-PVA also offers fast response times using modern RTC technologies.

Advanced super view, also called axially symmetric vertical alignment was developed by Sharp. It is a VA mode where liquid crystal molecules orient perpendicular to the substrates in the off state. The bottom sub-pixel has continuously covered electrodes, while the upper one has a smaller area electrode in the center of the subpixel.

When the field is on, the liquid crystal molecules start to tilt towards the center of the sub-pixels because of the electric field; as a result, a continuous pinwheel alignment (CPA) is formed; the azimuthal angle rotates 360 degrees continuously resulting in an excellent viewing angle. The ASV mode is also called CPA mode.

A technology developed by Samsung is Super PLS, which bears similarities to IPS panels and touts improved viewing angles and image quality, increased brightness and lower production costs. PLS technology debuted in the PC display market with the release of the Samsung S27A850 and S24A850 monitors in September 2011.

TFT dual-transistor pixel or cell technology is a reflective-display technology for use in very-low-power-consumption applications such as electronic shelf labels (ESL), digital watches, or metering. DTP involves adding a secondary transistor gate in the single TFT cell to maintain the display of a pixel during a period of 1s without loss of image or without degrading the TFT transistors over time. By slowing the refresh rate of the standard frequency from 60 Hz to 1 Hz, DTP claims to increase the power efficiency by multiple orders of magnitude.

Due to the very high cost of building TFT factories, there are few major OEM panel vendors for large display panels. The glass panel suppliers are as follows:

External consumer display devices like a TFT LCD feature one or more analog VGA, DVI, HDMI, or DisplayPort interface, with many featuring a selection of these interfaces. Inside external display devices there is a controller board that will convert the video signal using color mapping and image scaling usually employing the discrete cosine transform (DCT) in order to convert any video source like CVBS, VGA, DVI, HDMI, etc. into digital RGB at the native resolution of the display panel. In a laptop the graphics chip will directly produce a signal suitable for connection to the built-in TFT display. A control mechanism for the backlight is usually included on the same controller board.

The low level interface of STN, DSTN, or TFT display panels use either single ended TTL 5 V signal for older displays or TTL 3.3 V for slightly newer displays that transmits the pixel clock, horizontal sync, vertical sync, digital red, digital green, digital blue in parallel. Some models (for example the AT070TN92) also feature input/display enable, horizontal scan direction and vertical scan direction signals.

New and large (>15") TFT displays often use LVDS signaling that transmits the same contents as the parallel interface (Hsync, Vsync, RGB) but will put control and RGB bits into a number of serial transmission lines synchronized to a clock whose rate is equal to the pixel rate. LVDS transmits seven bits per clock per data line, with six bits being data and one bit used to signal if the other six bits need to be inverted in order to maintain DC balance. Low-cost TFT displays often have three data lines and therefore only directly support 18 bits per pixel. Upscale displays have four or five data lines to support 24 bits per pixel ( truecolor) or 30 bits per pixel ( HDR) respectively. Panel manufacturers are slowly replacing LVDS with Internal DisplayPort and Embedded DisplayPort, which allow sixfold reduction of the number of differential pairs.

Backlight intensity is usually controlled by varying a few volts DC, or generating a PWM signal, or adjusting a potentiometer or simply fixed. This in turn controls a high-voltage (1.3 kV) DC-AC inverter or a matrix of LEDs. The method to control the intensity of LED is to pulse them with PWM which can be source of harmonic flicker.

The bare display panel will only accept a digital video signal at the resolution determined by the panel pixel matrix designed at manufacture. Some screen panels will ignore the LSB bits of the color information to present a consistent interface (8 bit -> 6 bit/color x3).

With analogue signals like VGA, the display controller also needs to perform a high speed analog to digital conversion. With digital input signals like DVI or HDMI some simple reordering of the bits is needed before feeding it to the rescaler if the input resolution doesn't match the display panel resolution.

Liquid crystals are constantly subjected to toxicity and eco-toxicity testing for any hazard potential. The result is that:

wastewater from manufacturing is acutely toxic to aquatic life,

but may have an irritant, corrosive or sensitizing effect in rare cases. Any effects can be avoided by using a limited concentration in mixtures,

are not mutagenic - neither in bacteria (Ames test) nor in mammalian cells (mouse lymphoma assay or chromosome aberration test),

are not suspected of being carcinogenic,

are hazardous to aquatic organisms (bacteria, algae, daphnia, fish),

do not possess any significant bioaccumulation potential,

are not easily biodegradable.

The statements are applicable to Merck KGaA as well as its competitors JNC Corporation (formerly Chisso Corporation) and DIC (formerly Dainippon Ink & Chemicals). All three manufacturers have agreed not to introduce any acutely toxic or mutagenic liquid crystals to the market. They cover more than 90 percent of the global liquid crystal market. The remaining market share of liquid crystals, produced primarily in China, consists of older, patent-free substances from the three leading world producers and have already been tested for toxicity by them. As a result, they can also be considered non-toxic.

The complete report is available from Merck KGaA online.

The CCFL backlights used in many LCD monitors contain mercury, which is toxic.

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2. ^ Kuo, Yue (1 January 2013). "Thin Film Transistor Technology-Past, Present, and Future" (PDF). The Electrochemical Society Interface. 22 (1): 55-61. doi:10.1149/2.F06131if. ISSN 1064-8208.

3. ^ Brody, T. Peter; Asars, J. A.; Dixon, G. D. (November 1973). "A 6 × 6 inch 20 lines-per-inch liquid-crystal display panel". IEEE Transactions on Electron Devices. 20 (11): 995-1001. doi:10.1109/T-ED.1973.17780. ISSN 0018-9383.

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5. ^ Kimizuka, Noboru; Yamazaki, Shunpei (2016). Physics and Technology of Crystalline Oxide Semiconductor CAAC-IGZO: Fundamentals. John Wiley & Sons. p. 217. ISBN 9781119247401.

6. ^ Lojek, Bo (2007). History of Semiconductor Engineering. Springer Science & Business Media. pp. 322-324. ISBN 978-3540342588.

7. ^ Richard Ahrons (2012). "Industrial Research in Microcircuitry at RCA: The Early Years, 1953-1963". 12 (1). IEEE Annals of the History of Computing: 60-73.

8. Marek Matuszczyk, ^ Liquid crystals in displays Archived 2004-12-23 at the Wayback Machine. Chalmers University Sweden, c. 2000.

9. ^ K. H. Lee; H. Y. Kim; K. H. Park; S. J. Jang; I. C. Park & J. Y. Lee (June 2006). "A Novel Outdoor Readability of Portable TFT-LCD with AFFS Technology". SID Symposium Digest of Technical Papers. AIP. 37 (1): 1079-82. doi:10.1889/1.2433159.

10. ^ The World of Liquid Crystal Displays from personal.kent.edu/%7Emgu

11. ^ Kim, Sae-Bom; Kim, Woong-Ki; Chounlamany, Vanseng; Seo, Jaehwan; Yoo, Jisu; Jo, Hun-Je; Jung, Jinho (15 August 2012). "Identification of multi-level toxicity of liquid crystal display wastewater toward Daphnia magna and Moina macrocopa". Journal of Hazardous Materials. Seoul, Korea; Laos, Lao. 227-228: 327-333. doi:10.1016/j.jhazmat.2012.05.059 - via Elsevier.

12. ^ "Display solutions | Merck KGaA, Darmstadt, Germany". www.merck-performance-materials.com.

TFT Central - Reviews, News and Articles and includes panel search database

"Monitor panel search". FlatpanelsHD.com. - LCD monitor panel search database

Animated LCD Tutorial by 3M

LCD Panels with Response Time Compensation, X-bit labs, December 20, 2005

"Contemporary LCD Monitor Parameters and Characteristics". X-bit labs. October 26, 2004. Archived from the original on January 14, 2005.

Gaming issues with TFT LCD Displays, Digital Silence, August 10, 2004

What is TFT LCD, Plasma.com - detailed description of the technology inside a TFT LCD

Monitor buying guide - CNET reviews

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Horizontal IPS H-IPS 2007 Improves contrast ratio by twisting electrode plane layout. Also introduces an optional Advanced True White polarizing film from NEC, to make white look more natural. This is used in professional/photography LCDs. Enhanced IPS E-IPS 2009 Wider aperture for light transmission, enabling the use of lower-power, cheaper backlights.

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We fill the water tank and install it to our machine. So it is convenient where tap water is not available or qualitive.

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In order to make coffee we need some water. This can be done by 2 methods. either put a water tank or capsule or give a water hose connection to your coffee maker.

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A polymer (; Greek , "many" + , "part") is a substance or material consisting of very large molecules, or macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals.

The term "polymer" derives from the Greek word πολύς ( polus, meaning "many, much") and μέρος ( meros, meaning "part"), and refers to large molecules whose structure is composed of multiple repeating units, from which originates a characteristic of high relative molecular mass and attendant properties. The units composing polymers derive, actually or conceptually, from molecules of low relative molecular mass. The term was coined in 1833 by Jöns Jacob Berzelius, though with a definition distinct from the modern IUPAC definition. The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger, who spent the next decade finding experimental evidence for this hypothesis.

Polymers are studied in the fields of polymer science (which includes polymer chemistry and polymer physics), biophysics and materials science and engineering. Historically, products arising from the linkage of repeating units by covalent chemical bonds have been the primary focus of polymer science. An emerging important area now focuses on supramolecular polymers formed by non-covalent links. Polyisoprene of latex rubber is an example of a natural polymer, and the polystyrene of styrofoam is an example of a synthetic polymer. In biological contexts, essentially all biological macromolecules-i.e., proteins (polyamides), nucleic acids (polynucleotides), and polysaccharides-are purely polymeric, or are composed in large part of polymeric components.

Common examples

Polymers are of two types: naturally occurring and synthetic or man made.

Natural polymeric materials such as hemp, shellac, amber, wool, silk, and natural rubber have been used for centuries. A variety of other natural polymers exist, such as cellulose, which is the main constituent of wood and paper.

The list of synthetic polymers, roughly in order of worldwide demand, includes polyethylene, polypropylene, polystyrene, polyvinyl chloride, synthetic rubber, phenol formaldehyde resin (or Bakelite), neoprene, nylon, polyacrylonitrile, PVB, silicone, and many more. More than 330 million tons of these polymers are made every year (2015).

Most commonly, the continuously linked backbone of a polymer used for the preparation of plastics consists mainly of carbon atoms. A simple example is polyethylene ('polythene' in British English), whose repeating unit is based on ethylene monomer. Many other structures do exist; for example, elements such as silicon form familiar materials such as silicones, examples being Silly Putty and waterproof plumbing sealant. Oxygen is also commonly present in polymer backbones, such as those of polyethylene glycol, polysaccharides (in glycosidic bonds), and DNA (in phosphodiester bonds).

Polymers have been essential components of commodities since the early days of humankind. The use of wool ( keratin), cotton and linen fibres ( cellulose) for garments, paper reed ( cellulose) for paper are just a few examples of how our ancestors exploited polymer-containing raw materials to obtain artefacts. The latex sap of "cautchouc" trees ( natural rubber) reached Europe in the 16th century from South America long after the Olmec, Maya and Atzec had started using it as a material to make balls, waterproof textiles and containers.

The chemical manipulation of polymers dates back to the 19th century, although at the time the nature of these species was not understood. The behaviour of polymers was initially rationalised according to the theory proposed by Thomas Graham which considered them as colloidal aggregates of small molecules held together by unknown forces.

Notwithstanding the lack of theoretical knowledge, the potential of polymers to provide innovative, accessible and cheap materials was immediately grasped. The work carried out by Braconnot, Parkes, Ludersdorf, Hayard and many others on the modification of natural polymers determined many significant advances in the field. Their contributions led to the discovery of materials such as celluloid, galalith, parkesine, rayon, vulcanised rubber and, later, Bakelite: all materials that quickly entered industrial manufacturing processes and reached households as garments components ( e.g., fabrics, buttons), crockery and decorative items.

In 1920, Hermann Staudinger published his seminal work "Über Polymerisation", in which he proposed that polymers were in fact long chains of atoms linked by covalent bonds. His work was debated at length, but eventually it was accepted by the scientific community. Because of this work, Staudinger was awarded the Nobel Prize in 1953.

After the 1930s polymers entered a golden age during which new types were discovered and quickly given commercial applications, replacing naturally-sourced materials. This development was fuelled by an industrial sector with a strong economical drive and it was supported by a wide academic community that contributed with innovative synthesis of monomers from cheaper raw materials, more efficient polymerisation processes, improved techniques for polymer characterisation and advanced theoretical understanding of polymers.

Since 1953, six Nobel prizes were awarded in the area of polymer science, excluding those for research on biological macromolecules. This further testifies its impact on modern science and technology. As Lord Todd summarised it in 1980, "I am inclined to think that the development of polymerization is perhaps the biggest thing that chemistry has done, where it has had the biggest effect on everyday life".

Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain or network. During the polymerization process, some chemical groups may be lost from each monomer. This happens in the polymerization of PET polyester. The monomers are terephthalic acid (HOOC-C ₆H ₄-COOH) and ethylene glycol (HO-CH ₂-CH ₂-OH) but the repeating unit is -OC-C ₆H ₄-COO-CH ₂-CH ₂-O-, which corresponds to the combination of the two monomers with the loss of two water molecules. The distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue.

Synthetic methods are generally divided into two categories, step-growth polymerization and chain polymerization. The essential difference between the two is that in chain polymerization, monomers are added to the chain one at a time only, such as in polystyrene, whereas in step-growth polymerization chains of monomers may combine with one another directly, such as in polyester. Step-growth polymerization can be divided into polycondensation, in which low-molar-mass by-product is formed in every reaction step, and polyaddition.

Newer methods, such as plasma polymerization do not fit neatly into either category. Synthetic polymerization reactions may be carried out with or without a catalyst. Laboratory synthesis of biopolymers, especially of proteins, is an area of intensive research.

Biological synthesis

There are three main classes of biopolymers: polysaccharides, polypeptides, and polynucleotides. In living cells, they may be synthesized by enzyme-mediated processes, such as the formation of DNA catalyzed by DNA polymerase. The synthesis of proteins involves multiple enzyme-mediated processes to transcribe genetic information from the DNA to RNA and subsequently translate that information to synthesize the specified protein from amino acids. The protein may be modified further following translation in order to provide appropriate structure and functioning. There are other biopolymers such as rubber, suberin, melanin, and lignin.

Modification of natural polymers

Naturally occurring polymers such as cotton, starch, and rubber were familiar materials for years before synthetic polymers such as polyethene and perspex appeared on the market. Many commercially important polymers are synthesized by chemical modification of naturally occurring polymers. Prominent examples include the reaction of nitric acid and cellulose to form nitrocellulose and the formation of vulcanized rubber by heating natural rubber in the presence of sulfur. Ways in which polymers can be modified include oxidation, cross-linking, and endcapping.

The structure of a polymeric material can be described at different length scales, from the sub-nm length scale up to the macroscopic one. There is in fact a hierarchy of structures, in which each stage provides the foundations for the next one. The starting point for the description of the structure of a polymer is the identity of its constituent monomers. Next, the microstructure essentially describes the arrangement of these monomers within the polymer at the scale of a single chain. The microstructure determines the possibility for the polymer to form phases with different arrangements, for example though crystallization, the glass transition or microphase separation. These features play a major role in determining the physical and chemical properties of a polymer.

Monomers and repeat units

The identity of the repeat units (monomer residues, also known as "mers") comprising a polymer is its first and most important attribute. Polymer nomenclature is generally based upon the type of monomer residues comprising the polymer. A polymer which contains only a single type of repeat unit is known as a homopolymer, while a polymer containing two or more types of repeat units is known as a . A terpolymer is a copolymer which contains three types of repeat units.

Polystyrene is composed only of styrene-based repeat units, and is classified as a homopolymer. Polyethylene terephthalate, even though produced from two different monomers ( ethylene glycol and terephthalic acid), is usually regarded as a homopolymer because only one type of repeat unit is formed. Ethylene-vinyl acetate contains more than one variety of repeat unit and is a copolymer. Some biological polymers are composed of a variety of different but structurally related monomer residues; for example, polynucleotides such as DNA are composed of four types of nucleotide subunits.

A polymer molecule containing ionizable subunits is known as a polyelectrolyte or ionomer.

Microstructure

The microstructure of a polymer (sometimes called configuration) relates to the physical arrangement of monomer residues along the backbone of the chain. These are the elements of polymer structure that require the breaking of a covalent bond in order to change. Various polymer structures can be produced depending on the monomers and reaction conditions: A polymer may consist of linear macromolecules containing each only one unbranched chain. In the case of unbranched polyethylene, this chain is a long-chain n-alkane. There are also branched macromolecules with a main chain and side chains, in the case of polyethylene the side chains would be alkyl groups. In particular unbranched macromolecules can be in the solid state semi-crystalline, crystalline chain sections highlighted red in the figure below.

While branched and unbranched polymers are usually thermoplastics, many elastomers have a wide-meshed cross-linking between the "main chains". Close-meshed crosslinking, on the other hand, leads to thermosets. Cross-links and branches are shown as red dots in the figures. Highly branched polymers are amorphous and the molecules in the solid interact randomly.

Polymer architecture

An important microstructural feature of a polymer is its architecture and shape, which relates to the way branch points lead to a deviation from a simple linear chain. A branched polymer molecule is composed of a main chain with one or more substituent side chains or branches. Types of branched polymers include star polymers, comb polymers, polymer brushes, dendronized polymers, ladder polymers, and dendrimers. There exist also two-dimensional polymers (2DP) which are composed of topologically planar repeat units. A polymer's architecture affects many of its physical properties including solution viscosity, melt viscosity, solubility in various solvents, glass-transition temperature and the size of individual polymer coils in solution. A variety of techniques may be employed for the synthesis of a polymeric material with a range of architectures, for example living polymerization.

Chain length

A common means of expressing the length of a chain is the degree of polymerization, which quantifies the number of monomers incorporated into the chain. As with other molecules, a polymer's size may also be expressed in terms of molecular weight. Since synthetic polymerization techniques typically yield a statistical distribution of chain lengths, the molecular weight is expressed in terms of weighted averages. The number-average molecular weight ( M n) and weight-average molecular weight ( M w) are most commonly reported. The ratio of these two values ( M w / M n) is the dispersity ( Đ), which is commonly used to express the width of the molecular weight distribution.

The physical properties[34] of polymer strongly depend on the length (or equivalently, the molecular weight) of the polymer chain.[35] One important example of the physical consequences of the molecular weight is the scaling of the viscosity (resistance to flow) in the melt.[36] The influence of the weight-average molecular weight ( ) on the melt viscosity ( ) depends on whether the polymer is above or below the onset of entanglements. Below the entanglement molecular weight[clarification needed ], , whereas above the entanglement molecular weight, . In the latter case, increasing the polymer chain length 10-fold would increase the viscosity over 1000 times.[37][page needed ] Increasing chain length furthermore tends to decrease chain mobility, increase strength and toughness, and increase the glass-transition temperature (T g).[38] This is a result of the increase in chain interactions such as van der Waals attractions and entanglements that come with increased chain length.[39][40] These interactions tend to fix the individual chains more strongly in position and resist deformations and matrix breakup, both at higher stresses and higher temperatures.

Monomer arrangement in copolymers

Copolymers are classified either as statistical copolymers, alternating copolymers, block copolymers, graft copolymers or gradient copolymers. In the schematic figure below, Ⓐ and Ⓑ symbolize the two repeat units.

Alternating copolymers possess two regularly alternating monomer residues: [AB]n. An example is the equimolar copolymer of styrene and maleic anhydride formed by free-radical chain-growth polymerization. A step-growth copolymer such as Nylon 66 can also be considered a strictly alternating copolymer of diamine and diacid residues, but is often described as a homopolymer with the dimeric residue of one amine and one acid as a repeat unit.

Periodic copolymers have more than two species of monomer units in a regular sequence.

Statistical copolymers have monomer residues arranged according to a statistical rule. A statistical copolymer in which the probability of finding a particular type of monomer residue at a particular point in the chain is independent of the types of surrounding monomer residue may be referred to as a truly random copolymer. For example, the chain-growth copolymer of vinyl chloride and vinyl acetate is random.

Block copolymers have long sequences of different monomer units. Polymers with two or three blocks of two distinct chemical species (e.g., A and B) are called diblock copolymers and triblock copolymers, respectively. Polymers with three blocks, each of a different chemical species (e.g., A, B, and C) are termed triblock terpolymers.

Graft or grafted copolymers contain side chains or branches whose repeat units have a different composition or configuration than the main chain. The branches are added on to a preformed main chain macromolecule.

Monomers within a copolymer may be organized along the backbone in a variety of ways. A copolymer containing a controlled arrangement of monomers is called a sequence-controlled polymer. Alternating, periodic and block copolymers are simple examples of sequence-controlled polymers.

Tacticity describes the relative stereochemistry of chiral centers in neighboring structural units within a macromolecule. There are three types of tacticity: isotactic (all substituents on the same side), atactic (random placement of substituents), and syndiotactic (alternating placement of substituents).

Morphology

Polymer morphology generally describes the arrangement and microscale ordering of polymer chains in space. The macroscopic physical properties of a polymer are related to the interactions between the polymer chains.

Randomly oriented polymer

Interlocking of several polymers

Disordered polymers: In the solid state, atactic polymers, polymers with a high degree of branching and random copolymers form amorphous (i.e. glassy structures). In melt and solution, polymers tend to form a constantly changing "statistical cluster", see freely-jointed-chain model. In the solid state, the respective conformations of the molecules are frozen. Hooking and entanglement of chain molecules lead to a "mechanical bond" between the chains. Intermolecular and intramolecular attractive forces only occur at sites where molecule segments are close enough to each other. The irregular structures of the molecules prevent a narrower arrangement.

polyethylene: zigzag conformation of molecules in close packed chains

lamella with tie molecules

spherulite

Linear polymers with periodic structure, low branching and stereoregularity (e. g. not atactic) have a semi-crystalline structure in the solid state. In simple polymers (such as polyethylene), the chains are present in the crystal in zigzag conformation. Several zigzag conformations form dense chain packs, called crystallites or lamellae. The lamellae and are much thinner than the polymers are long (often about 10 nm). They are formed by more or less regular folding of one or more molecular chains. Amorphous structures exist between the lamellae. Individual molecules can lead to entanglements between the lamellae and can also be involved in the formation of two (or more) lamellae (chains than called tie molecules). Several lamellae form a superstructure, a spherulite, often with a diameter in the range of 0.05 to 1 mm.

The type and arrangement of (functional) residues of the repeat units effects or determines the crystallinity and strength of the secondary valence bonds. In isotactic polypropylene, the molecules form a helix. Like the zigzag conformation, such helices allow a dense chain packing. Particularly strong intermolecular interactions occur when the residues of the repeating units allow the formation of hydrogen bonds, as in the case of p-aramid. Crystallinity and superstructure are always dependent on the conditions of their formation, see also: crystallization of polymers. Compared to amorphous structures, semi-crystalline structures lead to a higher stiffness, density, melting temperature and higher resistance of a polymer.

Cross-linked polymers: Wide-meshed cross-linked polymers are elastomers and cannot be molten (unlike thermoplastics); heating cross-linked polymers only leads to decomposition. Thermoplastic elastomers, on the other hand, are reversibly "physically crosslinked" and can be molten. Block copolymers in which a hard segment of the polymer has a tendency to crystallize and a soft segment has an amorphous structure are one type of thermoplastic elastomers: the hard segments ensure wide-meshed, physical crosslinking.

wide-meshed cross-linked polymer (elastomer)

wide-meshed cross-linked polymer (elastomer) under tensile stress

crystallites as "crosslinking sites": one type of thermoplastic elastomer

semi-crystalline thermoplastic elastomer under tensile stress

Crystallinity

When applied to polymers, the term crystalline has a somewhat ambiguous usage. In some cases, the term crystalline finds identical usage to that used in conventional crystallography. For example, the structure of a crystalline protein or polynucleotide, such as a sample prepared for x-ray crystallography, may be defined in terms of a conventional unit cell composed of one or more polymer molecules with cell dimensions of hundreds of angstroms or more. A synthetic polymer may be loosely described as crystalline if it contains regions of three-dimensional ordering on atomic (rather than macromolecular) length scales, usually arising from intramolecular folding or stacking of adjacent chains. Synthetic polymers may consist of both crystalline and amorphous regions; the degree of crystallinity may be expressed in terms of a weight fraction or volume fraction of crystalline material. Few synthetic polymers are entirely crystalline. The crystallinity of polymers is characterized by their degree of crystallinity, ranging from zero for a completely non-crystalline polymer to one for a theoretical completely crystalline polymer. Polymers with microcrystalline regions are generally tougher (can be bent more without breaking) and more impact-resistant than totally amorphous polymers. Polymers with a degree of crystallinity approaching zero or one will tend to be transparent, while polymers with intermediate degrees of crystallinity will tend to be opaque due to light scattering by crystalline or glassy regions. For many polymers, reduced crystallinity may also be associated with increased transparency.

Chain conformation

The space occupied by a polymer molecule is generally expressed in terms of radius of gyration, which is an average distance from the center of mass of the chain to the chain itself. Alternatively, it may be expressed in terms of pervaded volume, which is the volume spanned by the polymer chain and scales with the cube of the radius of gyration. The simplest theoretical models for polymers in the molten, amorphous state are ideal chains.

Properties

Polymer properties depend of their structure and they are divided into classes according to their physical basis. Many physical and chemical properties describe how a polymer behaves as a continuous macroscopic material. They are classified as bulk properties, or intensive properties according to thermodynamics.

Mechanical properties

The bulk properties of a polymer are those most often of end-use interest. These are the properties that dictate how the polymer actually behaves on a macroscopic scale.

Tensile strength

The tensile strength of a material quantifies how much elongating stress the material will endure before failure. This is very important in applications that rely upon a polymer's physical strength or durability. For example, a rubber band with a higher tensile strength will hold a greater weight before snapping. In general, tensile strength increases with polymer chain length and crosslinking of polymer chains.

Young's modulus of elasticity

Transport properties

Transport properties such as diffusivity describe how rapidly molecules move through the polymer matrix. These are very important in many applications of polymers for films and membranes.

The movement of individual macromolecules occurs by a process called reptation in which each chain molecule is constrained by entanglements with neighboring chains to move within a virtual tube. The theory of reptation can explain polymer molecule dynamics and viscoelasticity.

Phase behavior

Crystallization and melting

Depending on their chemical structures, polymers may be either semi-crystalline or amorphous. Semi-crystalline polymers can undergo crystallization and melting transitions, whereas amorphous polymers do not. In polymers, crystallization and melting do not suggest solid-liquid phase transitions, as in the case of water or other molecular fluids. Instead, crystallization and melting refer to the phase transitions between two solid states ( i.e., semi-crystalline and amorphous). Crystallization occurs above the glass-transition temperature ( T g) and below the melting temperature ( T m).

Glass transition

All polymers (amorphous or semi-crystalline) go through glass transitions. The glass-transition temperature ( T g) is a crucial physical parameter for polymer manufacturing, processing, and use. Below T g, molecular motions are frozen and polymers are brittle and glassy. Above T g, molecular motions are activated and polymers are rubbery and viscous. The glass-transition temperature may be engineered by altering the degree of branching or crosslinking in the polymer or by the addition of plasticizers.

Whereas crystallization and melting are first-order phase transitions, the glass transition is not. The glass transition shares features of second-order phase transitions (such as discontinuity in the heat capacity, as shown in the figure), but it is generally not considered a thermodynamic transition between equilibrium states.

Mixing behavior

In general, polymeric mixtures are far less miscible than mixtures of small molecule materials. This effect results from the fact that the driving force for mixing is usually entropy, not interaction energy. In other words, miscible materials usually form a solution not because their interaction with each other is more favorable than their self-interaction, but because of an increase in entropy and hence free energy associated with increasing the amount of volume available to each component. This increase in entropy scales with the number of particles (or moles) being mixed. Since polymeric molecules are much larger and hence generally have much higher specific volumes than small molecules, the number of molecules involved in a polymeric mixture is far smaller than the number in a small molecule mixture of equal volume. The energetics of mixing, on the other hand, is comparable on a per volume basis for polymeric and small molecule mixtures. This tends to increase the free energy of mixing for polymer solutions and thereby making solvation less favorable, and thereby making the availability of concentrated solutions of polymers far rarer than those of small molecules.

Furthermore, the phase behavior of polymer solutions and mixtures is more complex than that of small molecule mixtures. Whereas most small molecule solutions exhibit only an upper critical solution temperature phase transition (UCST), at which phase separation occurs with cooling, polymer mixtures commonly exhibit a lower critical solution temperature phase transition (LCST), at which phase separation occurs with heating.

In dilute solutions, the properties of the polymer are characterized by the interaction between the solvent and the polymer. In a good solvent, the polymer appears swollen and occupies a large volume. In this scenario, intermolecular forces between the solvent and monomer subunits dominate over intramolecular interactions. In a bad solvent or poor solvent, intramolecular forces dominate and the chain contracts. In the theta solvent, or the state of the polymer solution where the value of the second virial coefficient becomes 0, the intermolecular polymer-solvent repulsion balances exactly the intramolecular monomer-monomer attraction. Under the theta condition (also called the Flory condition), the polymer behaves like an ideal random coil. The transition between the states is known as a coil-globule transition.

Inclusion of plasticizers

Inclusion of plasticizers tends to lower T g and increase polymer flexibility. Addition of the plasticizer will also modify dependence of the glass-transition temperature T g on the cooling rate. The mobility of the chain can further change if the molecules of plasticizer give rise to hydrogen bonding formation. Plasticizers are generally small molecules that are chemically similar to the polymer and create gaps between polymer chains for greater mobility and reduced interchain interactions. A good example of the action of plasticizers is related to polyvinylchlorides or PVCs. A uPVC, or unplasticized polyvinylchloride, is used for things such as pipes. A pipe has no plasticizers in it, because it needs to remain strong and heat-resistant. Plasticized PVC is used in clothing for a flexible quality. Plasticizers are also put in some types of cling film to make the polymer more flexible.

Chemical properties

The attractive forces between polymer chains play a large part in determining the polymer's properties. Because polymer chains are so long, they have many such interchain interactions per molecule, amplifying the effect of these interactions on the polymer properties in comparison to attractions between conventional molecules. Different side groups on the polymer can lend the polymer to ionic bonding or hydrogen bonding between its own chains. These stronger forces typically result in higher tensile strength and higher crystalline melting points.

The intermolecular forces in polymers can be affected by dipoles in the monomer units. Polymers containing amide or carbonyl groups can form hydrogen bonds between adjacent chains; the partially positively charged hydrogen atoms in N-H groups of one chain are strongly attracted to the partially negatively charged oxygen atoms in C=O groups on another. These strong hydrogen bonds, for example, result in the high tensile strength and melting point of polymers containing urethane or urea linkages. Polyesters have dipole-dipole bonding between the oxygen atoms in C=O groups and the hydrogen atoms in H-C groups. Dipole bonding is not as strong as hydrogen bonding, so a polyester's melting point and strength are lower than Kevlar's ( Twaron), but polyesters have greater flexibility. Polymers with non-polar units such as polyethylene interact only through weak Van der Waals forces. As a result, they typically have lower melting temperatures than other polymers.

When a polymer is dispersed or dissolved in a liquid, such as in commercial products like paints and glues, the chemical properties and molecular interactions influence how the solution flows and can even lead to self-assembly of the polymer into complex structures. When a polymer is applied as a coating, the chemical properties will influence the adhesion of the coating and how it interacts with external materials, such as superhydrophobic polymer coatings leading to water resistance. Overall the chemical properties of a polymer are important elements for designing new polymeric material products.

Optical properties

Polymers such as PMMA and HEMA:MMA are used as matrices in the gain medium of solid-state dye lasers, also known as solid-state dye-doped polymer lasers. These polymers have a high surface quality and are also highly transparent so that the laser properties are dominated by the laser dye used to dope the polymer matrix. These type of lasers, that also belong to the class of organic lasers, are known to yield very narrow linewidths which is useful for spectroscopy and analytical applications. An important optical parameter in the polymer used in laser applications is the change in refractive index with temperature also known as dn/dT. For the polymers mentioned here the (dn/dT) ~ −1.4 × 10 −4 in units of K −1 in the 297 ≤ T ≤ 337 K range.

Electrical properties

Most conventional polymers such as polythylene are electrical insulators, but the development of polymers containing π-conjugated bonds has led to a wealth of polymer-based semiconductors, such as polythiophenes. This has led to many applications in the field of organic electronics.

Applications

Nowadays, synthetic polymers are used in almost all walks of life. Modern society would look very different without them. The spreading of polymer use is connected to their unique properties: low density, low cost, good thermal/electrical insulation properties, high resistance to corrosion, low-energy demanding polymer manufacture and facile processing into final products. For a given application, the properties of a polymer can be tuned or enhanced by combination with other materials, as in composites. Their application allows to save energy (lighter cars and planes, thermally insulated buildings), protect food and drinking water (packaging), save land and reduce use of fertilizers (synthetic fibres), preserve other materials (coatings), protect and save lifes (hygiene, medical applications). A representative, non-exhaustive list of applications is given below.

Clothing, sportswear and accessories: polyester and PVC clothing, spandex, sport shoes, wetsuits, footballs and billiard balls, skis and snowboards, rackets, parachutes, sails, tents and shelters.

Electronic and photonic technologies: organic field effect transistors (OFET), light emitting diodes (OLED) and solar cells, television components, compact discs (CD), photoresists, holography.

Insulation: electrical and thermal insulation, spray foams.

Paints, glues and lubricants: varnish, adhesives, dispersants, anti-graffiti coatings, antifouling coatings, non-stick surfaces, lubricants.

Car parts: tires, bumpers, windshields, windscreen wipers, fuel tanks, car seats.

Medical applications: blood bag, syringes, rubber gloves, surgical suture, contact lenses, prosthesis, controlled drug delivery and release, matrices for cell growth.

Personal hygiene and healthcare: diapers using superabsorbent polymers, toothbrushes, cosmetics, shampoo, condoms.

Money: polymer banknotes and payment cards.

3D printing.

Standardized nomenclature

There are multiple conventions for naming polymer substances. Many commonly used polymers, such as those found in consumer products, are referred to by a common or trivial name. The trivial name is assigned based on historical precedent or popular usage rather than a standardized naming convention. Both the American Chemical Society (ACS) and IUPAC have proposed standardized naming conventions; the ACS and IUPAC conventions are similar but not identical. Examples of the differences between the various naming conventions are given in the table below:

Poly(ethylene oxide) or PEO

Poly(oxyethylene)

Poly(oxyethylene)

Poly(ethylene terephthalate) or PET

Poly(oxy-1,2-ethanediyloxycarbonyl-1,4-phenylenecarbonyl)

Poly(oxyethyleneoxyterephthaloyl)

Nylon 6 or Polyamide 6

Poly[imino(1-oxo-1,6-hexanediyl)]

Poly[azanediyl(1-oxohexane-1,6-diyl)]

In both standardized conventions, the polymers' names are intended to reflect the monomer(s) from which they are synthesized (source based nomenclature) rather than the precise nature of the repeating subunit. For example, the polymer synthesized from the simple alkene ethene is called polyethene, retaining the -ene suffix even though the double bond is removed during the polymerization process:

→

However, IUPAC structure based nomenclature is based on naming of the preferred constitutional repeating unit,[64].

Characterization

Polymer characterization spans many techniques for determining the chemical composition, molecular weight distribution, and physical properties. Select common techniques include the following:

Wide-angle X-ray scattering (also called wide-angle X-ray diffraction) is used to determine the crystalline structure of polymers (or lack thereof).

Spectroscopy techniques, including Fourier-transform infrared spectroscopy, Raman spectroscopy, and nuclear magnetic resonance spectroscopy, can be used to determine the chemical composition.

Differential scanning calorimetry is used to characterize the thermal properties of polymers, such as the glass-transition temperature, crystallization temperature, and melting temperature. The glass-transition temperature can also be determined by dynamic mechanical analysis.

Thermogravimetry is a useful technique to evaluate the thermal stability of the polymer.

Rheology is used to characterize the flow and deformation behavior. It can be used to determine the viscosity, modulus, and other rheological properties. Rheology is also often used to determine the molecular architecture (molecular weight, molecular weight distribution, branching) and to understand how the polymer can be processed.

Degradation

Although such changes are frequently undesirable, in some cases, such as biodegradation and recycling, they may be intended to prevent environmental pollution. Degradation can also be useful in biomedical settings. For example, a copolymer of polylactic acid and polyglycolic acid is employed in hydrolysable stitches that slowly degrade after they are applied to a wound.

The degradation of polyethylene occurs by random scission-a random breakage of the bonds that hold the atoms of the polymer together. When heated above 450 °C, polyethylene degrades to form a mixture of hydrocarbons. In the case of chain-end scission, monomers are released and this process is referred to as unzipping or depolymerize . With mechanism dominates will depend on the type of polymer and temperature; in general, polymers with no or a single small substituent in the repeat unit will decompose via random-chain scission.

The sorting of polymer waste for recycling purposes may be facilitated by the use of the resin identification codes developed by the Society of the Plastics Industry to identify the type of plastic.

Product failure

Failure of safety-critical polymer components can cause serious accidents, such as fire in the case of cracked and degraded polymer fuel lines. Chlorine-induced cracking of acetal resin plumbing joints and polybutylene pipes has caused many serious floods in domestic properties, especially in the US in the 1990s. Traces of chlorine in the water supply attacked polymers present in the plumbing, a problem which occurs faster if any of the parts have been poorly extruded or injection molded. Attack of the acetal joint occurred because of faulty molding, leading to cracking along the threads of the fitting where there is stress concentration.

Polymer oxidation has caused accidents involving medical devices. One of the oldest known failure modes is ozone cracking caused by chain scission when ozone gas attacks susceptible elastomers, such as natural rubber and nitrile rubber. They possess double bonds in their repeat units which are cleaved during ozonolysis. Cracks in fuel lines can penetrate the bore of the tube and cause fuel leakage. If cracking occurs in the engine compartment, electric sparks can ignite the gasoline and can cause a serious fire. In medical use degradation of polymers can lead to changes of physical and chemical characteristics of implantable devices.

References

1. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006-) "polymer". doi:10.1351/goldbook.P04735

2. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006-) "macromolecule (polymer molecule)". doi:10.1351/goldbook.M03667

3. If two substances had molecular formulae such that one was an integer multiple of the other - e.g., acetylene (C^ ₂H₂) and benzene (C₆H₆) - Berzelius called the multiple formula "polymeric". See: Jöns Jakob Berzelius (1833) "Isomerie, Unterscheidung von damit analogen Verhältnissen" (Isomeric, distinction from relations analogous to it), Jahres-Bericht über die Fortschitte der physischen Wissenschaften ..., 12: 63-67. From page 64: "Um diese Art von Gleichheit in der Zusammensetzung, bei Ungleichheit in den Eigenschaften, bezeichnen zu können, möchte ich für diese Körper die Benennung polymerische (von πολυς mehrere) vorschlagen." (In order to be able to denote this type of similarity in composition [which is accompanied] by differences in properties, I would like to propose the designation "polymeric" (from πολυς, several) for these substances.)
Originally published in 1832 in Swedish as: Jöns Jacob Berzelius (1832) "Isomeri, dess distinktion från dermed analoga förhållanden," Årsberättelse om Framstegen i Fysik och Kemi, pages 65-70; the word "polymeriska" appears on page 66.

4. ^ Jensen, William B. (2008). "Ask the Historian: The origin of the polymer concept" (PDF). Journal of Chemical Education. 85 (5): 624-625. Bibcode:2008JChEd..85..624J. doi:10.1021/ed085p624.

5. ^ Staudinger, H (1920). "Über Polymerisation" [On polymerization]. Berichte der Deutschen Chemischen Gesellschaft (in German). 53 (6): 1073-1085. doi:10.1002/cber.19200530627.

6. Feldman, Dorel (January 2008). "Polymer History". Designed Monomers and Polymers. 11 (1): 1-15. doi:10.1163/156855508X292383. ISSN 1568-5551. S2CID 219539020.

7. ^ Staudinger, H. (1920-06-12). "Über Polymerisation". Berichte der Deutschen Chemischen Gesellschaft (A and B Series). 53 (6): 1073-1085. doi:10.1002/cber.19200530627. ISSN 0365-9488.

8. Rubinstein, Michael; Colby, Ralph H. (2003). . Oxford; New York: Oxford University Press. p. 6. ISBN 978-0-19-852059-7.

9. ^ "Periodic copolymer". IUPAC Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). International Union of Pure and Applied Chemistry.

10. ^ Lutz, Jean-François; Ouchi, Makoto; Liu, David R.; Sawamoto, Mitsuo (2013-08-09). "Sequence-Controlled Polymers". Science. 341 (6146): 1238149. doi:10.1126/science.1238149. ISSN 0036-8075. PMID 23929982. S2CID 206549042.

11. Bernd Tieke: Makromolekulare Chemie. 3. Auflage, Wiley-VCH, Weinheim 2014, S. 295f (in German).

12. Wolfgang Kaiser: Kunststoffchemie für Ingenieure. 3. Auflage, Carl Hanser, München 2011, S. 84.

13. ^ Sayed, Abu (August 2014). "Types of polymer: Requirements of fibre forming polymer". Textile Apex.

14. ^ Meyers, M. A.; Chawla, K. K. (1999). Mechanical Behavior of Materials. Cambridge University Press. p. 41. ISBN 978-0-521-86675-0. Archived from the original on 2013-11-02.

15. ^ Meille, S.; Allegra, G.; Geil, P.; et al. (2011). "Definitions of terms relating to crystalline polymers (IUPAC Recommendations 2011)" (PDF). Pure and Applied Chemistry. 83 (10): 1831-1871. doi:10.1351/PAC-REC-10-11-13. S2CID 98823962.

16. ^ Capponi, S.; Alvarez, F.; Racko, D. (2020), "Free Volume in a PVME Polymer-Water Solution", Macromolecules, XXX (XXX): XXX-XXX, doi:10.1021/acs.macromol.0c00472

17. ^ Duarte, F. J. (1999). "Multiple-prism grating solid-state dye laser oscillator: optimized architecture". Applied Optics. 38 (30): 6347-6349. Bibcode:1999ApOpt..38.6347D. doi:10.1364/AO.38.006347. PMID 18324163.

18. ^ IUPAC (1976). "Nomenclature of Regular Single-Strand Organic Polymers". Pure Appl. Chem. 48 (3): 373-385. doi:10.1351/pac197648030373.

19. ^ Wilks, E.S. "Macromolecular Nomenclature Note No. 18". Archived from the original on 25 September 2003.

20. ^ Hiorns, R. C.; Boucher, R. J.; Duhlev, R.; Hellwich, Karl-Heinz; Hodge, Philip; Jenkins, Aubrey D.; Jones, Richard G.; Kahovec, Jaroslav; Moad, Graeme; Ober, C. K.; Smith, D. W. (2012-10-03). "A brief guide to polymer nomenclature (IUPAC Technical Report)". Pure and Applied Chemistry. 84 (10): 2167-2169. doi:10.1351/PAC-REP-12-03-05. ISSN 0033-4545. S2CID 95629051.

Bibliography

External links

# data[].attributes.attachment_link.description
A polymer (; Greek , "many" + , "part") is a substance or material consisting of very large molecules, or macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life.

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brass

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In contrast, bronze is an alloy of copper and tin. Both bronze and brass may include small proportions of a range of other elements including arsenic, lead, phosphorus, aluminium, manganese, and silicon. The distinction is largely historical. Modern practice in museums and archaeology increasingly avoids both terms for historical objects in favour of the all-embracing " copper alloy".

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copper

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Copper

Appearance

red-orange metallic luster

Standard atomic weight A r, std(Cu)

63.546(3) [1]

Copper in the periodic table

(Atomic number Z)

29

Group

group 11

Period

period 4

Block

d-block

Element category

Transition metal

Electron configuration

[ Ar] 3d ¹⁰ 4s ¹

Electrons per shell

2, 8, 18, 1

Physical properties

at Phase STP
solid

Melting point

1357.77 K ​(1084.62 °C, ​1984.32 °F)

(near Density r.t.)

8.96 g/cm ³

when liquid (at m.p.)

8.02 g/cm ³

Heat of fusion

13.26 kJ/mol

Vapor pressure

P (Pa)

1

10

100

1 k

10 k

100 k

at T (K)

1509

1661

1850

2089

2404

2834

Atomic properties

Oxidation states

−2, 0,[2] +1, +2, +3, +4 (a mildly basic oxide)

Ionization energies

1st: 745.5 kJ/mol

2nd: 1957.9 kJ/mol

3rd: 3555 kJ/mol

(more)

Atomic radius

empirical: 128 pm

Spectral lines of copper

Other properties

Natural occurrence
primordial

Crystal structure

​ face-centered cubic (fcc)

Speed of sound thin rod

(annealed)
3810 m/s (at r.t.)

Magnetic ordering

diamagnetic[3]

Magnetic susceptibility

−5.46·10 −6 cm ³/mol[4]

History

Naming

after Cyprus, principal mining place in Roman era ( Cyprium)

Discovery

( Middle East 9000 BC)

Main isotopes of copper

Category: Copper
| references

Copper is a chemical element with the symbol Cu (from Latin: cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orange color. Copper is used as a conductor of heat and electricity, as a building material, and as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins, and constantan used in strain gauges and thermocouples for temperature measurement.

Copper is one of the few metals that can occur in nature in a directly usable metallic form ( native metals). This led to very early human use in several regions, from c. 8000 BC. Thousands of years later, it was the first metal to be smelted from sulfide ores, c. 5000 BC; the first metal to be cast into a shape in a mold, c. 4000 BC; and the first metal to be purposefully alloyed with another metal, tin, to create bronze, c. 3500 BC.

In the Roman era, copper was mined principally on Cyprus, the origin of the name of the metal, from aes сyprium (metal of Cyprus), later corrupted to сuprum (Latin). Coper ( Old English) and copper were derived from this, the later spelling first used around 1530.

Commonly encountered compounds are copper(II) salts, which often impart blue or green colors to such minerals as azurite, malachite, and turquoise, and have been used widely and historically as pigments.

Copper used in buildings, usually for roofing, oxidizes to form a green verdigris (or patina). Copper is sometimes used in decorative art, both in its elemental metal form and in compounds as pigments. Copper compounds are used as bacteriostatic agents, fungicides, and wood preservatives.

Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c oxidase. In molluscs and crustaceans, copper is a constituent of the blood pigment hemocyanin, replaced by the iron-complexed hemoglobin in fish and other vertebrates. In humans, copper is found mainly in the liver, muscle, and bone. The adult body contains between 1.4 and 2.1 mg of copper per kilogram of body weight.

Characteristics

Copper, silver, and gold are in group 11 of the periodic table; these three metals have one s-orbital electron on top of a filled d- electron shell and are characterized by high ductility, and electrical and thermal conductivity. The filled d-shells in these elements contribute little to interatomic interactions, which are dominated by the s-electrons through metallic bonds. Unlike metals with incomplete d-shells, metallic bonds in copper are lacking a covalent character and are relatively weak. This observation explains the low hardness and high ductility of single crystals of copper. At the macroscopic scale, introduction of extended defects to the crystal lattice, such as grain boundaries, hinders flow of the material under applied stress, thereby increasing its hardness. For this reason, copper is usually supplied in a fine-grained polycrystalline form, which has greater strength than monocrystalline forms.

The softness of copper partly explains its high electrical conductivity (59.6×10 ⁶ S/m) and high thermal conductivity, second highest (second only to silver) among pure metals at room temperature. This is because the resistivity to electron transport in metals at room temperature originates primarily from scattering of electrons on thermal vibrations of the lattice, which are relatively weak in a soft metal. The maximum permissible current density of copper in open air is approximately 3.1×10 ⁶ A/m ² of cross-sectional area, above which it begins to heat excessively.

Copper is one of a few metallic elements with a natural color other than gray or silver. Pure copper is orange-red and acquires a reddish tarnish when exposed to air. The characteristic color of copper results from the electronic transitions between the filled 3d and half-empty 4s atomic shells - the energy difference between these shells corresponds to orange light.

As with other metals, if copper is put in contact with another metal, galvanic corrosion will occur.

Copper does not react with water, but it does slowly react with atmospheric oxygen to form a layer of brown-black copper oxide which, unlike the rust that forms on iron in moist air, protects the underlying metal from further corrosion ( passivation). A green layer of verdigris (copper carbonate) can often be seen on old copper structures, such as the roofing of many older buildings and the Statue of Liberty. Copper tarnishes when exposed to some sulfur compounds, with which it reacts to form various copper sulfides.

There are 29 isotopes of copper. ⁶³Cu and ⁶⁵Cu are stable, with ⁶³Cu comprising approximately 69% of naturally occurring copper; both have a spin of ​. The other isotopes are radioactive, with the most stable being ⁶⁷Cu with a half-life of 61.83 hours. Seven metastable isotopes have been characterized; 68mCu is the longest-lived with a half-life of 3.8 minutes. Isotopes with a mass number above 64 decay by , whereas those with a mass number below 64 decay by . , which has a half-life of 12.7 hours, decays both ways.

⁶²Cu and ⁶⁴Cu have significant applications. ⁶²Cu is used in ⁶²Cu-PTSM as a radioactive tracer for positron emission tomography.

Occurrence

Copper is produced in massive stars and is present in the Earth's crust in a proportion of about 50 parts per million (ppm). In nature, copper occurs in a variety of minerals, including native copper, copper sulfides such as chalcopyrite, bornite, digenite, covellite, and chalcocite, copper sulfosalts such as tetrahedite-tennantite, and enargite, copper carbonates such as azurite and malachite, and as copper(I) or copper(II) oxides such as cuprite and tenorite, respectively. The largest mass of elemental copper discovered weighed 420 tonnes and was found in 1857 on the Keweenaw Peninsula in Michigan, US. Native copper is a polycrystal, with the largest single crystal ever described measuring 4.4×3.2×3.2 cm.

Production

Most copper is mined or extracted as copper sulfides from large open pit mines in porphyry copper deposits that contain 0.4 to 1.0% copper. Sites include Chuquicamata, in Chile, Bingham Canyon Mine, in Utah, United States, and El Chino Mine, in New Mexico, United States. According to the British Geological Survey, in 2005, Chile was the top producer of copper with at least one-third of the world share followed by the United States, Indonesia and Peru. Copper can also be recovered through the in-situ leach process. Several sites in the state of Arizona are considered prime candidates for this method. The amount of copper in use is increasing and the quantity available is barely sufficient to allow all countries to reach developed world levels of usage.

Copper has been in use at least 10,000 years, but more than 95% of all copper ever mined and smelted has been extracted since 1900, and more than half was extracted the last 24 years. As with many natural resources, the total amount of copper on Earth is vast, with around 10 ¹⁴ tons in the top kilometer of Earth's crust, which is about 5 million years' worth at the current rate of extraction. However, only a tiny fraction of these reserves is economically viable with present-day prices and technologies. Estimates of copper reserves available for mining vary from 25 to 60 years, depending on core assumptions such as the growth rate. Recycling is a major source of copper in the modern world. Because of these and other factors, the future of copper production and supply is the subject of much debate, including the concept of peak copper, analogous to peak oil.

The price of copper has historically been unstable, and its price increased from the 60-year low of US$0.60/lb (US$1.32/kg) in June 1999 to $3.75 per pound ($8.27/kg) in May 2006. It dropped to $2.40/lb ($5.29/kg) in February 2007, then rebounded to $3.50/lb ($7.71/kg) in April 2007.[better source needed ] In February 2009, weakening global demand and a steep fall in commodity prices since the previous year's highs left copper prices at $1.51/lb ($3.32/kg).

The concentration of copper in ores averages only 0.6%, and most commercial ores are sulfides, especially chalcopyrite (CuFeS ₂), bornite (Cu ₅FeS ₄) and, to a lesser extent, covellite (CuS) and chalcocite (Cu ₂S). These minerals are concentrated from crushed ores to the level of 10-15% copper by froth flotation or bioleaching. Heating this material with silica in flash smelting removes much of the iron as slag. The process exploits the greater ease of converting iron sulfides into oxides, which in turn react with the silica to form the silicate slag that floats on top of the heated mass. The resulting copper matte, consisting of Cu ₂S, is roasted to convert all sulfides into oxides:

The cuprous oxide is converted to blister copper upon heating:

The Sudbury matte process converted only half the sulfide to oxide and then used this oxide to remove the rest of the sulfur as oxide. It was then electrolytically refined and the anode mud exploited for the platinum and gold it contained. This step exploits the relatively easy reduction of copper oxides to copper metal. Natural gas is blown across the blister to remove most of the remaining oxygen and electrorefining is performed on the resulting material to produce pure copper:

Like aluminium, copper is recyclable without any loss of quality, both from raw state and from manufactured products. In volume, copper is the third most recycled metal after iron and aluminium. An estimated 80% of all copper ever mined is still in use today. According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of copper in use in society is 35-55 kg. Much of this is in more-developed countries (140-300 kg per capita) rather than less-developed countries (30-40 kg per capita).

The process of recycling copper is roughly the same as is used to extract copper but requires fewer steps. High-purity scrap copper is melted in a furnace and then reduced and cast into billets and ingots; lower-purity scrap is refined by electroplating in a bath of sulfuric acid.

Numerous copper alloys have been formulated, many with important uses. Brass is an alloy of copper and zinc. Bronze usually refers to copper- tin alloys, but can refer to any alloy of copper such as aluminium bronze. Copper is one of the most important constituents of silver and karat gold solders used in the jewelry industry, modifying the color, hardness and melting point of the resulting alloys. Some lead-free solders consist of tin alloyed with a small proportion of copper and other metals.

The alloy of copper and nickel, called cupronickel, is used in low-denomination coins, often for the outer cladding. The US five-cent coin (currently called a nickel) consists of 75% copper and 25% nickel in homogeneous composition. Prior to the introduction of cupronickel, which was widely adopted by countries in the latter half of the 20th century, alloys of copper and silver were also used, with the United States using an alloy of 90% silver and 10% copper until 1965, when circulating silver was removed from all coins with the exception of the Half dollar - these were debased to an alloy of 40% silver and 60% copper between 1965 and 1970. The alloy of 90% copper and 10% nickel, remarkable for its resistance to corrosion, is used for various objects exposed to seawater, though it is vulnerable to the sulfides sometimes found in polluted harbors and estuaries. Alloys of copper with aluminium (about 7%) have a golden color and are used in decorations. is a Japanese decorative alloy of copper containing a low percentage of gold, typically 4-10%, that can be patinated to a dark blue or black color.

Copper forms a rich variety of compounds, usually with oxidation states +1 and +2, which are often called cuprous and cupric, respectively. Copper compounds, whether organic complexes or organometallics, promote or catalyse numerous chemical and biological processes.

Binary compounds

As with other elements, the simplest compounds of copper are binary compounds, i.e. those containing only two elements, the principal examples being oxides, sulfides, and halides. Both cuprous and cupric oxides are known. Among the numerous copper sulfides, important examples include copper(I) sulfide and copper(II) sulfide.

Cuprous halides (with chlorine, bromine, and iodine) are known, as are cupric halides with fluorine, chlorine, and bromine. Attempts to prepare copper(II) iodide yield only cuprous iodide and iodine.

Coordination chemistry

Copper forms coordination complexes with ligands. In aqueous solution, copper(II) exists as . This complex exhibits the fastest water exchange rate (speed of water ligands attaching and detaching) for any transition metal aquo complex. Adding aqueous sodium hydroxide causes the precipitation of light blue solid copper(II) hydroxide. A simplified equation is:

Aqueous ammonia results in the same precipitate. Upon adding excess ammonia, the precipitate dissolves, forming tetraamminecopper(II):

Many other oxyanions form complexes; these include copper(II) acetate, copper(II) nitrate, and copper(II) carbonate. Copper(II) sulfate forms a blue crystalline penta hydrate, the most familiar copper compound in the laboratory. It is used in a fungicide called the Bordeaux mixture.

Polyols, compounds containing more than one alcohol functional group, generally interact with cupric salts. For example, copper salts are used to test for reducing sugars. Specifically, using Benedict's reagent and Fehling's solution the presence of the sugar is signaled by a color change from blue Cu(II) to reddish copper(I) oxide. Schweizer's reagent and related complexes with ethylenediamine and other amines dissolve cellulose. Amino acids form very stable chelate complexes with copper(II). Many wet-chemical tests for copper ions exist, one involving potassium ferrocyanide, which gives a brown precipitate with copper(II) salts.

Organocopper chemistry

Compounds that contain a carbon-copper bond are known as organocopper compounds. They are very reactive towards oxygen to form copper(I) oxide and have many uses in chemistry. They are synthesized by treating copper(I) compounds with Grignard reagents, terminal alkynes or organolithium reagents; in particular, the last reaction described produces a Gilman reagent. These can undergo substitution with alkyl halides to form coupling products; as such, they are important in the field of organic synthesis. Copper(I) acetylide is highly shock-sensitive but is an intermediate in reactions such as the Cadiot-Chodkiewicz coupling and the Sonogashira coupling. Conjugate addition to enones and carbocupration of alkynes can also be achieved with organocopper compounds. Copper(I) forms a variety of weak complexes with alkenes and carbon monoxide, especially in the presence of amine ligands.

Copper(III) and copper(IV)

Copper(III) is most often found in oxides. A simple example is potassium cuprate, KCuO ₂, a blue-black solid. The most extensively studied copper(III) compounds are the cuprate superconductors. Yttrium barium copper oxide (YBa ₂Cu ₃O ₇) consists of both Cu(II) and Cu(III) centres. Like oxide, fluoride is a highly basic anion and is known to stabilize metal ions in high oxidation states. Both copper(III) and even copper(IV) fluorides are known, and , respectively.

Some copper proteins form oxo complexes, which also feature copper(III). With tetrapeptides, purple-colored copper(III) complexes are stabilized by the deprotonated amide ligands.

Complexes of copper(III) are also found as intermediates in reactions of organocopper compounds. For example, in the Kharasch-Sosnovsky reaction.

A timeline of copper illustrates how the metal has advanced human civilization for the past 11,000 years.

Prehistoric

Copper occurs naturally as native metallic copper and was known to some of the oldest civilizations on record. The history of copper use dates to 9000 BC in the Middle East; a copper pendant was found in northern Iraq that dates to 8700 BC. Evidence suggests that gold and meteoric iron (but not smelted iron) were the only metals used by humans before copper. The history of copper metallurgy is thought to follow this sequence: First, cold working of native copper, then annealing, smelting, and, finally, lost-wax casting. In southeastern Anatolia, all four of these techniques appear more or less simultaneously at the beginning of the Neolithic c. 7500 BC.

Copper smelting was independently invented in different places. It was probably discovered in China before 2800 BC, in Central America around 600 AD, and in West Africa about the 9th or 10th century AD. Investment casting was invented in 4500-4000 BC in Southeast Asia and carbon dating has established mining at Alderley Edge in Cheshire, UK, at 2280 to 1890 BC. Ötzi the Iceman, a male dated from 3300 to 3200 BC, was found with an axe with a copper head 99.7% pure; high levels of arsenic in his hair suggest an involvement in copper smelting. Experience with copper has assisted the development of other metals; in particular, copper smelting led to the discovery of iron smelting. Production in the Old Copper Complex in Michigan and Wisconsin is dated between 6000 and 3000 BC. Natural bronze, a type of copper made from ores rich in silicon, arsenic, and (rarely) tin, came into general use in the Balkans around 5500 BC.

Alloying copper with tin to make bronze was first practiced about 4000 years after the discovery of copper smelting, and about 2000 years after "natural bronze" had come into general use. Bronze artifacts from the Vinča culture date to 4500 BC. Sumerian and Egyptian artifacts of copper and bronze alloys date to 3000 BC. The Bronze Age began in Southeastern Europe around 3700-3300 BC, in Northwestern Europe about 2500 BC. It ended with the beginning of the Iron Age, 2000-1000 BC in the Near East, and 600 BC in Northern Europe. The transition between the Neolithic period and the Bronze Age was formerly termed the Chalcolithic period (copper-stone), when copper tools were used with stone tools. The term has gradually fallen out of favor because in some parts of the world, the Chalcolithic and Neolithic are coterminous at both ends. Brass, an alloy of copper and zinc, is of much more recent origin. It was known to the Greeks, but became a significant supplement to bronze during the Roman Empire.

Ancient and post-classical

In Greece, copper was known by the name chalkos (χαλκός). It was an important resource for the Romans, Greeks and other ancient peoples. In Roman times, it was known as aes Cyprium, aes being the generic Latin term for copper alloys and Cyprium from Cyprus, where much copper was mined. The phrase was simplified to cuprum, hence the English copper. Aphrodite ( Venus in Rome) represented copper in mythology and alchemy because of its lustrous beauty and its ancient use in producing mirrors; Cyprus was sacred to the goddess. The seven heavenly bodies known to the ancients were associated with the seven metals known in antiquity, and Venus was assigned to copper.

Copper was first used in ancient Britain in about the 3rd or 2nd century BC. In North America, copper mining began with marginal workings by Native Americans. Native copper is known to have been extracted from sites on Isle Royale with primitive stone tools between 800 and 1600. Copper metallurgy was flourishing in South America, particularly in Peru around 1000 AD. Copper burial ornamentals from the 15th century have been uncovered, but the metal's commercial production did not start until the early 20th century.

The cultural role of copper has been important, particularly in currency. Romans in the 6th through 3rd centuries BC used copper lumps as money. At first, the copper itself was valued, but gradually the shape and look of the copper became more important. Julius Caesar had his own coins made from brass, while Octavianus Augustus Caesar's coins were made from Cu-Pb-Sn alloys. With an estimated annual output of around 15,000 t, Roman copper mining and smelting activities reached a scale unsurpassed until the time of the Industrial Revolution; the provinces most intensely mined were those of Hispania, Cyprus and in Central Europe.

The gates of the Temple of Jerusalem used Corinthian bronze treated with depletion gilding.[clarification needed ][citation needed ] The process was most prevalent in Alexandria, where alchemy is thought to have begun. In ancient India, copper was used in the holistic medical science Ayurveda for surgical instruments and other medical equipment. Ancient Egyptians (~2400 BC) used copper for sterilizing wounds and drinking water, and later to treat headaches, burns, and itching.

The Great Copper Mountain was a mine in Falun, Sweden, that operated from the 10th century to 1992. It satisfied two-thirds of Europe's copper consumption in the 17th century and helped fund many of Sweden's wars during that time. It was referred to as the nation's treasury; Sweden had a copper backed currency.

Copper is used in roofing, currency, and for photographic technology known as the daguerreotype. Copper was used in Renaissance sculpture, and was used to construct the Statue of Liberty; copper continues to be used in construction of various types. Copper plating and copper sheathing were widely used to protect the under-water hulls of ships, a technique pioneered by the British Admiralty in the 18th century. The Norddeutsche Affinerie in Hamburg was the first modern electroplating plant, starting its production in 1876. The German scientist Gottfried Osann invented powder metallurgy in 1830 while determining the metal's atomic mass; around then it was discovered that the amount and type of alloying element (e.g., tin) to copper would affect bell tones.

During the rise in demand for copper for the Age of Electricity, from the 1880s until the Great Depression of the 1930s, the United States produced one third to half the world's newly mined copper. Major districts included the Keweenaw district of northern Michigan, primarily native copper deposits, which was eclipsed by the vast sulphide deposits of Butte, Montana in the late 1880s, which itself was eclipsed by porphyry deposits of the Souhwest United States, especially at Bingham Canyon, Utah and Morenci, Arizona. Introduction of open pit steam shovel mining and innovations in smelting, refining, flotation concentration and other processing steps led to mass production. Early in the twentieth century, Arizona ranked first, followed by Montana, then Utah and Michigan.

Flash smelting was developed by Outokumpu in Finland and first applied at Harjavalta in 1949; the energy-efficient process accounts for 50% of the world's primary copper production.

The Intergovernmental Council of Copper Exporting Countries, formed in 1967 by Chile, Peru, Zaire and Zambia, operated in the copper market as OPEC does in oil, though it never achieved the same influence, particularly because the second-largest producer, the United States, was never a member; it was dissolved in 1988.

Applications

The major applications of copper are electrical wire (60%), roofing and plumbing (20%), and industrial machinery (15%). Copper is used mostly as a pure metal, but when greater hardness is required, it is put into such alloys as brass and bronze (5% of total use). For more than two centuries, copper paint has been used on boat hulls to control the growth of plants and shellfish. A small part of the copper supply is used for nutritional supplements and fungicides in agriculture. Machining of copper is possible, although alloys are preferred for good machinability in creating intricate parts.

Wire and cable

Despite competition from other materials, copper remains the preferred electrical conductor in nearly all categories of electrical wiring except overhead electric power transmission where aluminium is often preferred. Copper wire is used in power generation, power transmission, power distribution, telecommunications, electronics circuitry, and countless types of electrical equipment. Electrical wiring is the most important market for the copper industry. This includes structural power wiring, power distribution cable, appliance wire, communications cable, automotive wire and cable, and magnet wire. Roughly half of all copper mined is used for electrical wire and cable conductors. Many electrical devices rely on copper wiring because of its multitude of inherent beneficial properties, such as its high electrical conductivity, tensile strength, ductility, creep (deformation) resistance, corrosion resistance, low thermal expansion, high thermal conductivity, ease of soldering, malleability, and ease of installation.

For a short period from the late 1960s to the late 1970s, copper wiring was replaced by aluminium wiring in many housing construction projects in America. The new wiring was implicated in a number of house fires and the industry returned to copper.

Electronics and related devices

Integrated circuits and printed circuit boards increasingly feature copper in place of aluminium because of its superior electrical conductivity; heat sinks and heat exchangers use copper because of its superior heat dissipation properties. Electromagnets, vacuum tubes, cathode ray tubes, and magnetrons in microwave ovens use copper, as do waveguides for microwave radiation.

Electric motors

Copper's superior conductivity enhances the efficiency of electrical motors. This is important because motors and motor-driven systems account for 43%-46% of all global electricity consumption and 69% of all electricity used by industry. Increasing the mass and cross section of copper in a coil increases the efficiency of the motor. Copper motor rotors, a new technology designed for motor applications where energy savings are prime design objectives, are enabling general-purpose induction motors to meet and exceed National Electrical Manufacturers Association (NEMA) premium efficiency standards.

Architecture

Copper has been used since ancient times as a durable, corrosion resistant, and weatherproof architectural material. Roofs, flashings, rain gutters, downspouts, domes, spires, vaults, and doors have been made from copper for hundreds or thousands of years. Copper's architectural use has been expanded in modern times to include interior and exterior wall cladding, building expansion joints, radio frequency shielding, and antimicrobial and decorative indoor products such as attractive handrails, bathroom fixtures, and counter tops. Some of copper's other important benefits as an architectural material include low thermal movement, light weight, lightning protection, and recyclability

The metal's distinctive natural green patina has long been coveted by architects and designers. The final patina is a particularly durable layer that is highly resistant to atmospheric corrosion, thereby protecting the underlying metal against further weathering. It can be a mixture of carbonate and sulfate compounds in various amounts, depending upon environmental conditions such as sulfur-containing acid rain. Architectural copper and its alloys can also be 'finished' to take on a particular look, feel, or color. Finishes include mechanical surface treatments, chemical coloring, and coatings.

Copper has excellent brazing and soldering properties and can be welded; the best results are obtained with gas metal arc welding.

Antibiofouling

Copper is biostatic, meaning bacteria and many other forms of life will not grow on it. For this reason it has long been used to line parts of ships to protect against barnacles and mussels. It was originally used pure, but has since been superseded by Muntz metal and copper-based paint. Similarly, as discussed in copper alloys in aquaculture, copper alloys have become important netting materials in the aquaculture industry because they are antimicrobial and prevent biofouling, even in extreme conditions and have strong structural and corrosion-resistant properties in marine environments.

Antimicrobial

Copper-alloy touch surfaces have natural properties that destroy a wide range of microorganisms (e.g., O157:H7, methicillin-resistant Staphylococcus aureus ( MRSA), Staphylococcus, Clostridium difficile, influenza A virus, adenovirus, and fungi). Some 355 copper alloys[clarification needed ] were proven to kill more than 99.9% of disease-causing bacteria within just two hours when cleaned regularly. The United States Environmental Protection Agency (EPA) has approved the registrations of these copper alloys as " antimicrobial materials with public health benefits"; that approval allows manufacturers to make legal claims to the public health benefits of products made of registered alloys. In addition, the EPA has approved a long list of antimicrobial copper products made from these alloys, such as bedrails, handrails, over-bed tables, sinks, faucets, door knobs, toilet hardware, computer keyboards, health club equipment, and shopping cart handles (for a comprehensive list, see: Antimicrobial copper-alloy touch surfaces#Approved products). Copper doorknobs are used by hospitals to reduce the transfer of disease, and Legionnaires' disease is suppressed by copper tubing in plumbing systems. Antimicrobial copper alloy products are now being installed in healthcare facilities in the U.K., Ireland, Japan, Korea, France, Denmark, and Brazil, as well as being called for in the US, and in the subway transit system in Santiago, Chile, where copper-zinc alloy handrails were installed in some 30 stations between 2011 and 2014. Textile fibers can be blended with copper to create antimicrobial protective fabrics.

Speculative investing

Copper may be used as a speculative investment due to the predicted increase in use from worldwide infrastructure growth, and the important role it has in producing wind turbines, solar panels, and other renewable energy sources. Another reason predicted demand increases is the fact that electric cars contain an average of 3.6 times as much copper as conventional cars, although the effect of electric cars on copper demand is debated. Some people invest in copper through copper mining stocks, ETFs, and futures. Others store physical copper in the form of copper bars or rounds although these tend to carry a higher premium in comparison to precious metals. Those who want to avoid the premiums of copper bullion alternatively store old copper wire, copper tubing or American pennies made before 1982.

Folk medicine

Copper is commonly used in jewelry, and according to some folklore, copper bracelets relieve arthritis symptoms. In one trial for osteoarthritis and one trial for rheumatoid arthritis no differences is found between copper bracelet and control (non-copper) bracelet. No evidence shows that copper can be absorbed through the skin. If it were, it might lead to copper poisoning.

Compression clothing

Recently, some compression clothing with inter-woven copper has been marketed with health claims similar to the folk medicine claims. Because compression clothing is a valid treatment for some ailments, the clothing may have that benefit, but the added copper may have no benefit beyond a placebo effect.

Degradation

Chromobacterium violaceum and Pseudomonas fluorescens can both mobilize solid copper as a cyanide compound. The ericoid mycorrhizal fungi associated with Calluna, Erica and Vaccinium can grow in metalliferous soils containing copper. The ectomycorrhizal fungus Suillus luteus protects young pine trees from copper toxicity. A sample of the fungus Aspergillus niger was found growing from gold mining solution and was found to contain cyano complexes of such metals as gold, silver, copper, iron, and zinc. The fungus also plays a role in the solubilization of heavy metal sulfides.

Biological role

Biochemistry

Copper proteins have diverse roles in biological electron transport and oxygen transportation, processes that exploit the easy interconversion of Cu(I) and Cu(II). Copper is essential in the aerobic respiration of all eukaryotes. In mitochondria, it is found in cytochrome c oxidase, which is the last protein in oxidative phosphorylation. Cytochrome c oxidase is the protein that binds the O ₂ between a copper and an iron; the protein transfers 8 electrons to the O ₂ molecule to reduce it to two molecules of water. Copper is also found in many superoxide dismutases, proteins that catalyze the decomposition of superoxides by converting it (by disproportionation) to oxygen and hydrogen peroxide:

The protein hemocyanin is the oxygen carrier in most mollusks and some arthropods such as the horseshoe crab ( Limulus polyphemus). Because hemocyanin is blue, these organisms have blue blood rather than the red blood of iron-based hemoglobin. Structurally related to hemocyanin are the laccases and tyrosinases. Instead of reversibly binding oxygen, these proteins hydroxylate substrates, illustrated by their role in the formation of lacquers. The biological role for copper commenced with the appearance of oxygen in earth's atmosphere. Several copper proteins, such as the "blue copper proteins", do not interact directly with substrates; hence they are not enzymes. These proteins relay electrons by the process called electron transfer.

A unique tetranuclear copper center has been found in nitrous-oxide reductase.

Chemical compounds which were developed for treatment of Wilson's disease have been investigated for use in cancer therapy.

Copper is an essential trace element in plants and animals, but not all microorganisms. The human body contains copper at a level of about 1.4 to 2.1 mg per kg of body mass.

Absorption

Copper is absorbed in the gut, then transported to the liver bound to albumin. After processing in the liver, copper is distributed to other tissues in a second phase, which involves the protein ceruloplasmin, carrying the majority of copper in blood. Ceruloplasmin also carries the copper that is excreted in milk, and is particularly well-absorbed as a copper source. Copper in the body normally undergoes enterohepatic circulation (about 5 mg a day, vs. about 1 mg per day absorbed in the diet and excreted from the body), and the body is able to excrete some excess copper, if needed, via bile, which carries some copper out of the liver that is not then reabsorbed by the intestine.

Dietary recommendations

The U.S. Institute of Medicine (IOM) updated the estimated average requirements (EARs) and recommended dietary allowances (RDAs) for copper in 2001. If there is not sufficient information to establish EARs and RDAs, an estimate designated Adequate Intake (AI) is used instead. The AIs for copper are: 200 μg of copper for 0-6-month-old males and females, and 220 μg of copper for 7-12-month-old males and females. For both sexes, the RDAs for copper are: 340 μg of copper for 1-3 years old, 440 μg of copper for 4-8 years old, 700 μg of copper for 9-13 years old, 890 μg of copper for 14-18 years old and 900 μg of copper for ages 19 years and older. For pregnancy, 1,000 μg. For lactation, 1,300 μg. As for safety, the IOM also sets Tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of copper the UL is set at 10 mg/day. Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes.

The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL defined the same as in United States. For women and men ages 18 and older the AIs are set at 1.3 and 1.6 mg/day, respectively. AIs for pregnancy and lactation is 1.5 mg/day. For children ages 1-17 years the AIs increase with age from 0.7 to 1.3 mg/day. These AIs are higher than the U.S. RDAs. The European Food Safety Authority reviewed the same safety question and set its UL at 5 mg/day, which is half the U.S. value.

For U.S. food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of Daily Value (%DV). For copper labeling purposes 100% of the Daily Value was 2.0 mg, but as of May 27, 2016 it was revised to 0.9 mg to bring it into agreement with the RDA. Compliance with the updated labeling regulations was required by 1 January 2020, for manufacturers with $10 million or more in annual food sales, and by 1 January 2021, for manufacturers with less than $10 million in annual food sales. During the first six months following the 1 January 2020 compliance date, the FDA plans to work cooperatively with manufacturers to meet the new Nutrition Facts label requirements and will not focus on enforcement actions regarding these requirements during that time. A table of the old and new adult Daily Values is provided at Reference Daily Intake.

Deficiency

Because of its role in facilitating iron uptake, copper deficiency can produce anemia-like symptoms, neutropenia, bone abnormalities, hypopigmentation, impaired growth, increased incidence of infections, osteoporosis, hyperthyroidism, and abnormalities in glucose and cholesterol metabolism. Conversely, Wilson's disease causes an accumulation of copper in body tissues.

Severe deficiency can be found by testing for low plasma or serum copper levels, low ceruloplasmin, and low red blood cell superoxide dismutase levels; these are not sensitive to marginal copper status. The "cytochrome c oxidase activity of leucocytes and platelets" has been stated as another factor in deficiency, but the results have not been confirmed by replication.

Gram quantities of various copper salts have been taken in suicide attempts and produced acute copper toxicity in humans, possibly due to redox cycling and the generation of reactive oxygen species that damage DNA. Corresponding amounts of copper salts (30 mg/kg) are toxic in animals. A minimum dietary value for healthy growth in rabbits has been reported to be at least 3 ppm in the diet. However, higher concentrations of copper (100 ppm, 200 ppm, or 500 ppm) in the diet of rabbits may favorably influence feed conversion efficiency, growth rates, and carcass dressing percentages.

Chronic copper toxicity does not normally occur in humans because of transport systems that regulate absorption and excretion. Autosomal recessive mutations in copper transport proteins can disable these systems, leading to Wilson's disease with copper accumulation and cirrhosis of the liver in persons who have inherited two defective genes.

Elevated copper levels have also been linked to worsening symptoms of Alzheimer's disease.

Human exposure

In the US, the Occupational Safety and Health Administration (OSHA) has designated a permissible exposure limit (PEL) for copper dust and fumes in the workplace as a time-weighted average (TWA) of 1 mg/m ³. The National Institute for Occupational Safety and Health (NIOSH) has set a Recommended exposure limit (REL) of 1 mg/m ³, time-weighted average. The IDLH (immediately dangerous to life and health) value is 100 mg/m ³.

Copper is a constituent of tobacco smoke. The tobacco plant readily absorbs and accumulates heavy metals, such as copper from the surrounding soil into its leaves. These are readily absorbed into the user's body following smoke inhalation. The health implications are not clear.

Peak copper

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in pure water, or acidic or alkali conditions. Copper in neutral water is more noble than hydrogen.

in water containing sulfide

in 10 M ammonia solution

in a chloride solution

Further reading

Massaro, Edward J., ed. (2002). Handbook of Copper Pharmacology and Toxicology. Humana Press. ISBN 978-0-89603-943-8.

"Copper: Technology & Competitiveness (Summary) Chapter 6: Copper Production Technology" (PDF). Office of Technology Assessment. 2005.

Current Medicinal Chemistry, Volume 12, Number 10, May 2005, pp. 1161-1208(48) Metals, Toxicity and Oxidative Stress

William D. Callister (2003). Materials Science and Engineering: an Introduction (6th ed.). Wiley, New York. Table 6.1, p. 137. ISBN 978-0-471-73696-7.

Material: Copper (Cu), bulk, MEMS and Nanotechnology Clearinghouse.

Kim BE; Nevitt T; Thiele DJ (2008). "Mechanisms for copper acquisition, distribution and regulation". Nat. Chem. Biol. 4 (3): 176-85. doi:10.1038/nchembio.72. PMID 18277979.

External links

# data[].attributes.attachment_link.description
Copper Appearance red-orange metallic luster Standard atomic weight A r, std(Cu) 63.546(3) [1] Copper in the periodic table (Atomic number Z) 29 Group group 11 Period period 4 Block d-block Element category Transition metal Electron configuration [ Ar] 3d 10 4s 1 Electrons per shell 2, 8, 18, 1 Physical properties at Phase STP solid Melting point 1357.77 K ​(1084.62 °C, ​1984.32 °F) (near Density r.t.)

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Nickel will alloy readily with other metals, including chromium, iron, molybdenum and copper. Discover the various types of nickel alloys and their properties and consult further technical literature on this topic here.

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A glass building facade

Glass is a non-crystalline solid that is often transparent, brittle and chemically inert. It has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics.

Glass is most often formed by rapid cooling ( quenching) of the molten form; some glasses such as volcanic glass are naturally occurring. The most familiar, and historically the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. Soda-lime glass, containing around 70% silica, accounts for around 90% of manufactured glass. The term glass, in popular usage, is often used to refer only to this type of material, although silica-free glasses often have desirable properties for applications in modern communications technology. Some objects, such as drinking glasses and eyeglasses, are so commonly made of silicate-based glass that they are simply called by the name of the material.

Despite being brittle, buried silicate glass will survive for very long periods if not disturbed, and many examples of glass fragments exist from early glassmaking cultures. Archaeological evidence suggests glassmaking dates back to at least 3600 BC in Mesopotamia, Egypt, or Syria. The earliest known glass objects were beads, perhaps created accidentally during metalworking or the production of faience. Due to its ease of formability into any shape, glass has been traditionally used for vessels, such as bowls, vases, bottles, jars and drinking glasses. In its most solid forms, it has also been used for paperweights and marbles. Glass can be coloured by adding metal salts or painted and printed with vitreous enamels, leading to its use in stained glass windows and other glass art objects. The refractive, reflective and transmission properties of glass make glass suitable for manufacturing optical lenses, prisms, and optoelectronics materials. Extruded glass fibres have application as optical fibres in communications networks, thermal insulating material when matted as glass wool so as to trap air, or in glass-fibre reinforced plastic ( fibreglass).

Microscopic structure

The amorphous structure of glassy silica (SiO₂) in two dimensions. No long-range order is present, although there is local ordering with respect to the tetrahedral arrangement of oxygen (O) atoms around the silicon (Si) atoms.

Microscopically, a single crystal has atoms in a near-perfect periodic arrangement; a polycrystal is composed of many microscopic crystals; and an amorphous solid such as glass has no periodic arrangement even microscopically.

The standard definition of a glass (or vitreous solid) is a non-crystalline solid formed by rapid melt quenching. However, the term "glass" is often defined in a broader sense, to describe any non-crystalline ( amorphous) solid that exhibits a glass transition when heated towards the liquid state.

Glass is an amorphous solid. Although the atomic-scale structure of glass shares characteristics of the structure of a supercooled liquid, glass exhibits all the mechanical properties of a solid. As in other amorphous solids, the atomic structure of a glass lacks the long-range periodicity observed in crystalline solids. Due to chemical bonding constraints, glasses do possess a high degree of short-range order with respect to local atomic polyhedra. The notion that glass flows to an appreciable extent over extended periods of time well below the glass transition temperature is not supported by empirical research or theoretical analysis (see viscosity in solids). Though atomic motion at glass surfaces can be observed, and a viscosity on the order of 10 ¹⁷-10 ¹⁸ Pa s can be measured in glass, such a high value reinforces the fact that glass would not change shape appreciably over even large periods of time.

Formation from a supercooled liquid

Unsolved problem in physics :

What is the nature of the transition between a fluid or regular solid and a glassy phase? "The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition." - P.W. Anderson

For melt quenching, if the cooling is sufficiently rapid (relative to the characteristic crystallization time) then crystallization is prevented and instead the disordered atomic configuration of the supercooled liquid is frozen into the solid state at T g. The tendency for a material to form a glass while quenched is called glass-forming ability. This ability can be predicted by the rigidity theory. Generally, a glass exists in a structurally metastable state with respect to its crystalline form, although in certain circumstances, for example in atactic polymers, there is no crystalline analogue of the amorphous phase.

Glass is sometimes considered to be a liquid due to its lack of a first-order phase transition where certain thermodynamic variables such as volume, entropy and enthalpy are discontinuous through the glass transition range. The glass transition may be described as analogous to a second-order phase transition where the intensive thermodynamic variables such as the thermal expansivity and heat capacity are discontinuous. However, the equilibrium theory of phase transformations does not hold for glass, and hence the glass transition cannot be classed as one of the classical equilibrium phase transformations in solids.

Occurrence in nature

Glass can form naturally from volcanic magma. Obsidian is a common volcanic glass with high silica (SiO ₂) content formed when felsic lava extruded from a volcano cools rapidly. Impactite is a form of glass formed by the impact of a meteorite, where Moldavite (found in central and eastern Europe), and Libyan desert glass (found in areas in the eastern Sahara, the deserts of eastern Libya and western Egypt) are notable examples. Vitrification of quartz can also occur when lightning strikes sand, forming hollow, branching rootlike structures called fulgurites. Trinitite is a glassy residue formed from the desert floor sand at the Trinity nuclear bomb test site. Edeowie glass, found in South Australia, is proposed to originate from Pleistocene grassland fires, lightning strikes, or hypervelocity impact by one or several asteroids or comets.

Roman cage cup from the 4th century BC

Naturally occurring obsidian glass was used by Stone Age societies as it fractures along very sharp edges, making it ideal for cutting tools and weapons. Glassmaking dates back at least 6000 years, long before humans had discovered how to smelt iron. Archaeological evidence suggests that the first true synthetic glass was made in Lebanon and the coastal north Syria, Mesopotamia or ancient Egypt. The earliest known glass objects, of the mid-third millennium BC, were beads, perhaps initially created as accidental by-products of metalworking ( slags) or during the production of faience, a pre-glass vitreous material made by a process similar to glazing. Early glass was rarely transparent and often contained impurities and imperfections, and is technically faience rather than true glass, which did not appear until the 15th century BC. However, red-orange glass beads excavated from the Indus Valley Civilization dated before 1700 BC (possibly as early as 1900 BC) predate sustained glass production, which appeared around 1600 BC in Mesopotamia and 1500 BC in Egypt. During the Late Bronze Age there was a rapid growth in glassmaking technology in Egypt and Western Asia. Archaeological finds from this period include coloured glass ingots, vessels, and beads. Much early glass production relied on grinding techniques borrowed from stoneworking, such as grinding and carving glass in a cold state.

The term glass developed in the late Roman Empire. It was in the Roman glassmaking centre at Trier (located in current-day Germany) that the late-Latin term glesum originated, probably from a Germanic word for a transparent, lustrous substance. Glass objects have been recovered across the Roman Empire in domestic, funerary, and industrial contexts, as well as trade items in marketplaces in distant provinces. Examples of Roman glass have been found outside of the former Roman Empire in China, the Baltics, the Middle East, and India. The Romans perfected cameo glass, produced by etching and carving through fused layers of different colours to produce a design in relief on the glass object.

Windows in the choir of the Basilica of Saint-Denis, one of the earliest uses of extensive areas of glass (early 13th-century architecture with restored glass of the 19th century)

In post-classical West Africa, Benin was a manufacturer of glass and glass beads. Glass was used extensively in Europe during the Middle Ages. Anglo-Saxon glass has been found across England during archaeological excavations of both settlement and cemetery sites. From the 10th century onwards, glass was employed in stained glass windows of churches and cathedrals, with famous examples at Chartres Cathedral and the Basilica of Saint-Denis. By the 14th century, architects were designing buildings with walls of stained glass such as Sainte-Chapelle, Paris, (1203-1248) and the East end of Gloucester Cathedral. With the change in architectural style during the Renaissance period in Europe, the use of large stained glass windows became much less prevalent, although stained glass had a major revival with Gothic Revival architecture in the 19th century.

During the 13th century, the island of Murano, Venice, became a centre for glass making, building on medieval techniques to produce colourful ornamental pieces in large quantities. Murano glass makers developed the exceptionally clear colourless glass cristallo, so called for its resemblance to natural crystal, which was extensively used for windows, mirrors, ships' lanterns, and lenses. In the 13th, 14th, and 15th centuries, enamelling and gilding on glass vessels was perfected in Egypt and Syria. Towards the end of the 17th century, Bohemia became an important region for glass production, remaining so until the start of the 20th century. By the 17th century, glass in the Venetian tradition was also being produced in England. In about 1675, George Ravenscroft invented lead crystal glass, with cut glass becoming fashionable in the 18th century. Ornamental glass objects became an important art medium during the Art Nouveau period in the late 19th century.

Throughout the 20th century, new mass production techniques led to widespread availability of glass in much larger amounts, making it practical as a building material and enabling new applications of glass. In the 1920s a mould-etch process was developed, in which art was etched directly into the mould, so that each cast piece emerged from the mould with the image already on the surface of the glass. This reduced manufacturing costs and, combined with a wider use of coloured glass, led to cheap glassware in the 1930s, which later became known as Depression glass. In the 1950s, Pilkington Bros., England, developed the float glass process, producing high-quality distortion-free flat sheets of glass by floating on molten tin. Modern multi-story buildings are frequently constructed with curtain walls made almost entirely of glass. Laminated glass has been widely applied to vehicles for windscreens. Optical glass for spectacles has been used since the Middle Ages. The production of lenses has become increasingly proficient, aiding astronomers as well as having other application in medicine and science. Glass is also employed as the aperture cover in many solar energy collectors.

In the 21st century, glass manufacturers have developed different brands of chemically strengthened glass for widespread application in touchscreens for smartphones, tablet computers, and many other types of information appliances. These include Gorilla Glass, developed and manufactured by Corning, AGC Inc.'s Dragontrail and Schott AG's Xensation.

Physical properties

Glass is in widespread use in optical systems due to its ability to refract, reflect, and transmit light following geometrical optics. The most common and oldest applications of glass in optics are as lenses, windows, mirrors, and prisms. The key optical properties refractive index, dispersion, and transmission, of glass are strongly dependent on chemical composition and, to a lesser degree, its thermal history. Optical glass typically has a refractive index of 1.4 to 2.4, and an Abbe number (which characterises dispersion) of 15 to 100. Refractive index may be modified by high-density (refractive index increases) or low-density (refractive index decreases) additives.

Glass transparency results from the absence of grain boundaries which diffusely scatter light in polycrystalline materials. Semi-opacity due to crystallization may be induced in many glasses by maintaining them for a long period at a temperature just insufficient to cause fusion. In this way, the crystalline, devitrified material, known as Réaumur's glass porcelain is produced. Although generally transparent to visible light, glasses may be opaque to other wavelengths of light. While silicate glasses are generally opaque to infrared wavelengths with a transmission cut-off at 4 μm, heavy-metal fluoride and chalcogenide glasses are transparent to infrared wavelengths of 7 to 18 μm. The addition of metallic oxides results in different coloured glasses as the metallic ions will absorb wavelengths of light corresponding to specific colours.

Glass can be fairly easily melted and manipulated with a heat source

In the manufacturing process, glasses can be poured, formed, extruded and moulded into forms ranging from flat sheets to highly intricate shapes. The finished product is brittle but can be laminated or tempered to enhance durability. Glass is typically inert, resistant to chemical attack, and can mostly withstand the action of water, making it an ideal material for the manufacture of containers for foodstuffs and most chemicals. Nevertheless, although usually highly resistant to chemical attack, glass will corrode or dissolve under some conditions. The materials that make up a particular glass composition have an effect on how quickly the glass corrodes. Glasses containing a high proportion of alkali or alkaline earth elements are more susceptible to corrosion than other glass compositions.

The density of glass varies with chemical composition with values ranging from 2.2 grams per cubic centimetre (2,200 kg/m ³) for fused silica to 7.2 grams per cubic centimetre (7,200 kg/m ³) for dense flint glass. Glass is stronger than most metals, with a theoretical tensile strength for pure, flawless glass estimated at 14 to 35 gigapascals (2,000,000 to 5,100,000 psi) due to its ability to undergo reversible compression without fracture. However, the presence of scratches, bubbles, and other microscopic flaws lead to a typical range of 14 to 175 megapascals (2,000 to 25,400 psi) in most commercial glasses. Several processes such as toughening can increase the strength of glass. Carefully drawn flawless glass fibres can be produced with strength of up to 11.5 gigapascals (1,670,000 psi).

Reputed flow

The observation that old windows are sometimes found to be thicker at the bottom than at the top is often offered as supporting evidence for the view that glass flows over a timescale of centuries, the assumption being that the glass has exhibited the liquid property of flowing from one shape to another. This assumption is incorrect, as once solidified, glass stops flowing. The sags and ripples observed in old glass were already there the day it was made; manufacturing processes used in the past produced sheets with imperfect surfaces and non-uniform thickness (the near-perfect float glass used today only became widespread in the 1960s).

A 2017 study computed the rate of flow of the medieval glass used in Westminster Abbey from the year 1268. The study found that the room temperature viscosity of this glass was roughly 10 ²⁴ Pa· s which is about 10 ¹⁶ times less viscous than a previous estimate made in 1998, which focused on soda-lime silicate glass. Even with this lower viscosity, the study authors calculated that the maximum flow rate of medieval glass is 1 nm per billion years, making it impossible to observe in a human timescale.

Quartz sand (silica) is the main raw material in commercial glass production

Silicon dioxide (SiO ₂) is a common fundamental constituent of glass. Fused quartz is a glass made from chemically pure silica. It has very low thermal expansion and excellent resistance to thermal shock, being able to survive immersion in water while red hot, resists high temperatures (1000-1500 °C) and chemical weathering, and is very hard. It is also transparent to a wider spectral range than ordinary glass, extending from the visible further into both the UV and IR ranges, and is sometimes used where transparency to these wavelengths is necessary. Fused quartz is used for high-temperature applications such as furnace tubes, lighting tubes, melting crucibles, etc. However, its high melting temperature (1723 °C) and viscosity make it difficult to work with. Therefore, normally, other substances (fluxes) are added to lower the melting temperature and simplify glass processing.

Sodium carbonate (Na ₂CO ₃, "soda") is a common additive and acts to lower the glass-transition temperature. However, sodium silicate is water-soluble, so lime (CaO, calcium oxide, generally obtained from limestone), along with magnesium oxide (MgO), and aluminium oxide (Al ₂O ₃), are commonly added to improve chemical durability. Soda-lime glasses (Na ₂O) + lime (CaO) + magnesia (MgO) + alumina (Al ₂O ₃) account for over 75% of manufactured glass, containing about 70 to 74% silica by weight. Soda-lime-silicate glass is transparent, easily formed, and most suitable for window glass and tableware. However, it has a high thermal expansion and poor resistance to heat. Soda-lime glass is typically used for windows, bottles, light bulbs, and jars.

Borosilicate

A Pyrex borosilicate glass measuring cup

Borosilicate glasses (e.g. Pyrex, Duran) typically contain 5-13% boron trioxide (B ₂O ₃). Borosilicate glasses have fairly low coefficients of thermal expansion (7740 Pyrex CTE is 3.25×10/°C as compared to about 9×10/°C for a typical soda-lime glass). They are, therefore, less subject to stress caused by thermal expansion and thus less vulnerable to cracking from thermal shock. They are commonly used for e.g. labware, household cookware, and sealed beam car head lamps.

The addition of lead(II) oxide into silicate glass lowers melting point and viscosity of the melt. The high density of lead glass (silica + lead oxide (PbO) + potassium oxide (K ₂O) + soda (Na ₂O) + zinc oxide (ZnO) + alumina) results in a high electron density, and hence high refractive index, making the look of glassware more brilliant and causing noticeably more specular reflection and increased optical dispersion. Lead glass has a high elasticity, making the glassware more workable and giving rise to a clear "ring" sound when struck. However, lead glass cannot withstand high temperatures well. Lead oxide also facilitates solubility of other metal oxides and is used in coloured glass. The viscosity decrease of lead glass melt is very significant (roughly 100 times in comparison with soda glass); this allows easier removal of bubbles and working at lower temperatures, hence its frequent use as an additive in vitreous enamels and glass solders. The high ionic radius of the Pb ²⁺ ion renders it highly immobile and hinders the movement of other ions; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda-lime glass (10 8.5 vs 10 6.5 Ω⋅cm, DC at 250 °C).

Aluminosilicate

Aluminosilicate glass typically contains 5-10% alumina (Al ₂O ₃). Aluminosilicate glass tends to be more difficult to melt and shape compared to borosilicate compositions, but has excellent thermal resistance and durability. Aluminosilicate glass is extensively used for fiberglass, used for making glass-reinforced plastics (boats, fishing rods, etc.), top-of-stove cookware, and halogen bulb glass.

Other oxide additives

The addition of barium also increases the refractive index. Thorium oxide gives glass a high refractive index and low dispersion and was formerly used in producing high-quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern eyeglasses. Iron can be incorporated into glass to absorb infrared radiation, for example in heat-absorbing filters for movie projectors, while cerium(IV) oxide can be used for glass that absorbs ultraviolet wavelengths. Fluorine lowers the dielectric constant of glass. Fluorine is highly electronegative and lowers the polarizability of the material. Fluoride silicate glasses are used in manufacture of integrated circuits as an insulator.

Glass-ceramics

A high-strength glass-ceramic cooktop with negligible thermal expansion

Glass-ceramic materials contain both non-crystalline glass and crystalline ceramic phases. They are formed by controlled nucleation and partial crystallisation of a base glass by heat treatment. Crystalline grains are often embedded within a non-crystalline intergranular phase of grain boundaries. Glass-ceramics exhibit advantageous thermal, chemical, biological, and dielectric properties as compared to metals or organic polymers.

The most commercially important property of glass-ceramics is their imperviousness to thermal shock. Thus, glass-ceramics have become extremely useful for countertop cooking and industrial processes. The negative thermal expansion coefficient (CTE) of the crystalline ceramic phase can be balanced with the positive CTE of the glassy phase. At a certain point (~70% crystalline) the glass-ceramic has a net CTE near zero. This type of glass-ceramic exhibits excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 °C.

Fibreglass

Fibreglass (also called glass fibre reinforced plastic, GRP) is a composite material made by reinforcing a plastic resin with glass fibres. It is made by melting glass and stretching the glass into fibres. These fibres are woven together into a cloth and left to set in a plastic resin. Fibreglass has the properties of being lightweight and corrosion resistant, and is a good insulator enabling its use as building insulation material and for electronic housing for consumer products. Fibreglass was originally used in the United Kingdom and United States during World War II to manufacture radomes. Uses of fibreglass include building and construction materials, boat hulls, car body parts, and aerospace composite materials.

Glass-fibre wool is an excellent thermal and sound insulation material, commonly used in buildings (e.g. attic and cavity wall insulation), and plumbing (e.g. pipe insulation), and soundproofing. It is produced by forcing molten glass through a fine mesh by centripetal force, and breaking the extruded glass fibres into short lengths using a stream of high-velocity air. The fibres are bonded with an adhesive spray and the resulting wool mat is cut and packed in rolls or panels.

Non-silicate

A CD-RW (CD). Chalcogenide glass form the basis of rewritable CD and DVD solid-state memory technology.[93]

Besides common silica-based glasses many other inorganic and organic materials may also form glasses, including metals, aluminates, phosphates, borates, chalcogenides, fluorides, germanates (glasses based on ), tellurites (glasses based on TeO ₂), antimonates (glasses based on Sb ₂O ₃), arsenates (glasses based on As ₂O ₃), titanates (glasses based on TiO ₂), tantalates (glasses based on Ta ₂O ₅), nitrates, carbonates, plastics, acrylic, and many other substances. Some of these glasses (e.g. Germanium dioxide (GeO ₂, Germania), in many respects a structural analogue of silica, fluoride, aluminate, phosphate, borate, and chalcogenide glasses) have physico-chemical properties useful for their application in fibre-optic waveguides in communication networks and other specialised technological applications.

Silica-free glasses may often have poor glass forming tendencies. Novel techniques, including containerless processing by aerodynamic levitation (cooling the melt whilst it floats on a gas stream) or splat quenching (pressing the melt between two metal anvils or rollers), may be used to increase cooling rate, or to reduce crystal nucleation triggers.

Samples of amorphous metal, with millimeter scale

In the past, small batches of amorphous metals with high surface area configurations (ribbons, wires, films, etc.) have been produced through the implementation of extremely rapid rates of cooling. Amorphous metal wires have been produced by sputtering molten metal onto a spinning metal disk.

A number of alloys have been produced in layers with thickness exceeding 1 millimeter. These are known as bulk metallic glasses (BMG). Liquidmetal Technologies sell a number of zirconium-based BMGs.

Batches of amorphous steel have also been produced that demonstrate mechanical properties far exceeding those found in conventional steel alloys.

Experimental evidence indicates that the system Al-Fe-Si may undergo a first-order transition to an amorphous form (dubbed "q-glass") on rapid cooling from the melt. Transmission electron microscopy (TEM) images indicate that q-glass nucleates from the melt as discrete particles with a uniform spherical growth in all directions. While x-ray diffraction reveals the isotropic nature of q-glass, a nucleation barrier exists implying an interfacial discontinuity (or internal surface) between the glass and melt phases.

Important polymer glasses include amorphous and glassy pharmaceutical compounds. These are useful because the solubility of the compound is greatly increased when it is amorphous compared to the same crystalline composition. Many emerging pharmaceuticals are practically insoluble in their crystalline forms. Many polymer thermoplastics familiar from everyday use are glasses. For many applications, like glass bottles or eyewear, polymer glasses ( acrylic glass, polycarbonate or polyethylene terephthalate) are a lighter alternative to traditional glass.

Molecular liquids and molten salts

Molecular liquids, electrolytes, molten salts, and aqueous solutions are mixtures of different molecules or ions that do not form a covalent network but interact only through weak van der Waals forces or through transient hydrogen bonds. In a mixture of three or more ionic species of dissimilar size and shape, crystallization can be so difficult that the liquid can easily be supercooled into a glass. Examples include LiCl: RH ₂O (a solution of lithium chloride salt and water molecules) in the composition range 4< R<8. sugar glass, or Ca 0.4K 0.6(NO ₃) 1.4. Glass electrolytes in the form of Ba-doped Li-glass and Ba-doped Na-glass have been proposed as solutions to problems identified with organic liquid electrolytes used in modern lithium-ion battery cells.

Production

Glass blowing

Robotised float glass unloading

Following the glass batch preparation and mixing, the raw materials are transported to the furnace. Soda-lime glass for mass production is melted in glass melting furnaces. Smaller scale furnaces for specialty glasses include electric melters, pot furnaces, and day tanks. After melting, homogenization and refining (removal of bubbles), the glass is formed. This may be achieved manually by glassblowing, which involves gathering a mass of hot semi-molten glass, inflating it into a bubble using a hollow blowpipe, and forming it into required shape by blowing, swinging, rolling, or molding. While hot, the glass can be worked using hand tools, cut with shears, and additional parts such as handles or feet attached by welding. Flat glass for windows and similar applications is formed by the float glass process, developed between 1953 and 1957 by Sir Alastair Pilkington and Kenneth Bickerstaff of the UK's Pilkington Brothers, who created a continuous ribbon of glass using a molten tin bath on which the molten glass flows unhindered under the influence of gravity. The top surface of the glass is subjected to nitrogen under pressure to obtain a polished finish. Container glass for common bottles and jars is formed by blowing and pressing methods. This glass is often slightly modified chemically (with more alumina and calcium oxide) for greater water resistance.

Once the desired form is obtained, glass is usually annealed for the removal of stresses and to increase the glass's hardness and durability. Surface treatments, coatings or lamination may follow to improve the chemical durability ( glass container coatings, glass container internal treatment), strength ( toughened glass, bulletproof glass, windshields), or optical properties ( insulated glazing, anti-reflective coating).

New chemical glass compositions or new treatment techniques can be initially investigated in small-scale laboratory experiments. The raw materials for laboratory-scale glass melts are often different from those used in mass production because the cost factor has a low priority. In the laboratory mostly pure chemicals are used. Care must be taken that the raw materials have not reacted with moisture or other chemicals in the environment (such as alkali or alkaline earth metal oxides and hydroxides, or boron oxide), or that the impurities are quantified (loss on ignition). Evaporation losses during glass melting should be considered during the selection of the raw materials, e.g., sodium selenite may be preferred over easily evaporating selenium dioxide (SeO ₂). Also, more readily reacting raw materials may be preferred over relatively inert ones, such as aluminum hydroxide (Al(OH) ₃) over alumina (Al ₂O ₃). Usually, the melts are carried out in platinum crucibles to reduce contamination from the crucible material. Glass homogeneity is achieved by homogenizing the raw materials mixture ( glass batch), by stirring the melt, and by crushing and re-melting the first melt. The obtained glass is usually annealed to prevent breakage during processing.

Colour in glass may be obtained by addition of homogenously distributed electrically charged ions (or colour centres). While ordinary soda-lime glass appears colourless in thin section, iron(II) oxide (FeO) impurities produce a green tint in thick sections. Manganese dioxide (MnO ₂), which gives glass a purple colour, may be added to remove the green tint given by FeO. FeO and chromium(III) oxide (Cr ₂O ₃) additives are used in the production of green bottles. Iron (III) oxide, on the other-hand, produces yellow or yellow-brown glass. Low concentrations (0.025 to 0.1%) of cobalt oxide (CoO) produces rich, deep blue cobalt glass. Chromium is a very powerful colourising agent, yielding dark green. Sulphur combined with carbon and iron salts produces amber glass ranging from yellowish to almost black. A glass melt can also acquire an amber colour from a reducing combustion atmosphere. Cadmium sulfide produces imperial red, and combined with selenium can produce shades of yellow, orange, and red. The additive Copper(II) oxide (CuO) produces a turquoise colour in glass, in contrast to Copper(I) oxide (Cu ₂ O) which gives a dull brown-red colour.

Architecture and windows

Soda-lime sheet glass is typically used as transparent glazing material, typically as windows in external walls of buildings. Float or rolled sheet glass products is cut to size either by scoring and snapping the material, laser cutting, water jets, or diamond bladed saw. The glass may be thermally or chemically tempered (strengthened) for safety and bent or curved during heating. Surface coatings may be added for specific functions such as scratch resistance, blocking specific wavelengths of light (e.g. infrared or ultraviolet), dirt-repellence (e.g. self-cleaning glass), or switchable electrochromic coatings.

Structural glazing systems represent one of the most significant architectural innovations of modern times, where glass buildings now often dominate skylines of many modern cities. These systems use stainless steel fittings countersunk into recesses in the corners of the glass panels allowing strengthened panes to appear unsupported creating a flush exterior. Structural glazing systems have their roots in iron and glass conservatories of the nineteenth century

Glass is an essential component of tableware and is typically used for water, beer and wine drinking glasses. Wine glasses are typically stemware, i.e. goblets formed from a bowl, stem, and foot. Crystal or Lead crystal glass may be cut and polished to produce decorative drinking glasses with gleaming facets. Other uses of glass in tableware include decanters, jugs, plates, and bowls.

The inert and impermeable nature of glass makes it a stable and widely used material for food and drink packaging as glass bottles and jars. Most container glass is soda-lime glass, produced by blowing and pressing techniques. Container glass has a lower magnesium oxide and sodium oxide content than flat glass, and a higher silica, calcium oxide, and aluminum oxide content. Its higher content of water-insoluble oxides imparts slightly higher chemical durability against water, which is advantageous for storing beverages and food. Glass packaging is sustainable, readily recycled, reusable and refillable.

For electronics applications, glass can be used as a substrate in the manufacture of integrated passive devices, thin-film bulk acoustic resonators, and as a hermetic sealing material in device packaging, including very thin solely glass based encapsulation of integrated circuits and other semiconductors in high manufacturing volumes.

Laboratories

Glass is an important material in scientific laboratories for the manufacture of experimental apparatus because it is relatively cheap, readily formed into required shapes for experiment, easy to keep clean, can withstand heat and cold treatment, is generally non-reactive with many reagents, and its transparency allows for the observation of chemical reactions and processes. Laboratory glassware applications include flasks, petri dishes, test tubes, pipettes, graduated cylinders, glass lined metallic containers for chemical processing, fractionation columns, glass pipes, Schlenk lines, gauges, and thermometers. Although most standard laboratory glassware has been mass-produced since the 1920s, scientists still employ skilled glassblowers to manufacture bespoke glass apparatus for their experimental requirements.

Glass is a ubiquitous material in optics by virtue of its ability to refract, reflect, and transmit light. These and other optical properties can be controlled by varying chemical compositions, thermal treatment, and manufacturing techniques. The many applications of glass in optics includes glasses for eyesight correction, imaging optics (e.g. lenses and mirrors in telescopes, microscopes, and cameras), fibre optics in telecommunications technology, and integrated optics. Microlenses and gradient-index optics (where the refractive index is non-uniform) find application in e.g. reading optical discs, laser printers, photocopiers, and laser diodes.

Glass as art dates to least 1300 BC shown as an example of natural glass found in Tutankhamun's pectoral, which also contained vitreous enamel, that is to say, melted coloured glass used on a metal backing. Enamelled glass, the decoration of glass vessels with coloured glass paints, has existed since 1300 BC, and was prominent in the early 20th century with Art Nouveau glass and that of the House of Fabergé in St. Petersburg, Russia. Both techniques were used in stained glass, which reached its height roughly from 1000 to 1550, before a revival in the 19th century.

The 19th century saw a revival in ancient glassmaking techniques including cameo glass, achieved for the first time since the Roman Empire, initially mostly for pieces in a neo-classical style. The Art Nouveau movement made great use of glass, with René Lalique, Émile Gallé, and Daum of Nancy in the first French wave of the movement, producing coloured vases and similar pieces, often in cameo glass or in lustre glass techniques.

Louis Comfort Tiffany in America specialised in stained glass, both secular and religious, in panels and his famous lamps. The early 20th-century saw the large-scale factory production of glass art by firms such as Waterford and Lalique. Small studios may hand-produce glass artworks. Techniques for producing glass art include blowing, kiln-casting, fusing, slumping, pâte de verre, flame-working, hot-sculpting and cold-working. Cold work includes traditional stained glass work and other methods of shaping glass at room temperature. Objects made out of glass include vessels, paperweights, marbles, beads, sculptures and installation art.

References

1. ^ ASTM definition of glass from 1945

2. ^

3. "Philip Gibbs" ^ Glass Worldwide, (May/June 2007), pp. 14-18

4. ^ Ashtekar, Sumit; Scott, Gregory; Lyding, Joseph; Gruebele, Martin (2010). "Direct Visualization of Two-State Dynamics on Metallic Glass Surfaces Well Below Tg". J. Phys. Chem. Lett. 1 (13): 1941-1945. arXiv:1006.1684. doi:10.1021/jz100633d. S2CID 93171134.

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External links

# data[].attributes.attachment_link.description
Glass is a non-crystalline solid that is often transparent, brittle and chemically inert. It has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching) of the molten form; some glasses such as volcanic glass are naturally occurring.

# data[].attributes.attachment_link.readable_text
Pronunciation

Alternative name

Aluminum (U.S., Canada)

Appearance

Silvery gray metallic

(Atomic number Z)

13

Group
group 13 (boron group)

Period
period 3

Block

p-block

Electron configuration

[ Ne] 3s ² 3p ¹

Electrons per shell

2, 8, 3

at Phase STP
solid

Melting point

933.47 K ​(660.32 °C, ​1220.58 °F)

Density (at 20° C)

2.699 g/cm ³[4]

when liquid (at m.p.)

2.375 g/cm ³

Heat of fusion

10.71 kJ/mol

Vapor pressure

P (Pa)

1

10

100

1 k

10 k

100 k

at T (K)

1482

1632

1817

2054

2364

2790

Oxidation states

−2, −1, 0,[5] +1,[6] +2,[7] +3 (an amphoteric oxide)

Ionization energies

1st: 577.5 kJ/mol

2nd: 1816.7 kJ/mol

3rd: 2744.8 kJ/mol

(more)

Atomic radius

empirical: 143 pm

Spectral lines of aluminium

Natural occurrence
primordial

Crystal structure

​ face-centered cubic (fcc) ( cF4)

Lattice constant

a = 404.93 pm (at 20 °C)[4]

Thermal expansion

22.87×10 −6/K (at 20 °C)[4]

Magnetic ordering

paramagnetic[8]

Molar magnetic susceptibility

+16.5×10 −6 cm ³/mol

Speed of sound thin rod

(rolled) 5000 m/s (at r.t.)

Naming

from alumine, obsolete name for alumina

Prediction

Antoine Lavoisier (1782)

Discovery

Hans Christian Ørsted (1824)

Named by

(1812 Humphry Davy[a])

Category: Aluminium
| references

Aluminium ( Aluminum in North American English) is a chemical element; it has symbol Al and atomic number 13. Aluminium has a density lower than that of other common metals, about one-third that of steel. It has a great affinity towards oxygen, forming a protective layer of oxide on the surface when exposed to air. Aluminium visually resembles silver, both in its color and in its great ability to reflect light. It is soft, nonmagnetic, and ductile. It has one stable isotope, ²⁷Al, which is highly abundant, making aluminium the twelfth-most common element in the universe. The radioactivity of , a more unstable isotope, leads to it being used in radiometric dating.

Chemically, aluminium is a post-transition metal in the boron group; as is common for the group, aluminium forms compounds primarily in the +3 oxidation state. The aluminium cation Al ³⁺ is small and highly charged; as such, it has more polarizing power, and bonds formed by aluminium have a more covalent character. The strong affinity of aluminium for oxygen leads to the common occurrence of its oxides in nature. Aluminium is found on Earth primarily in rocks in the crust, where it is the third-most abundant element, after oxygen and silicon, rather than in the mantle, and virtually never as the free metal. It is obtained industrially by mining bauxite, a sedimentary rock rich in aluminium minerals.

The discovery of aluminium was announced in 1825 by Danish physicist Hans Christian Ørsted. The first industrial production of aluminium was initiated by French chemist Henri Étienne Sainte-Claire Deville in 1856. Aluminium became much more available to the public with the Hall-Héroult process developed independently by French engineer Paul Héroult and American engineer Charles Martin Hall in 1886, and the mass production of aluminium led to its extensive use in industry and everyday life. In the First and Second World Wars, aluminium was a crucial strategic resource for aviation. In 1954, aluminium became the most produced non-ferrous metal, surpassing copper. In the 21st century, most aluminium was consumed in transportation, engineering, construction, and packaging in the United States, Western Europe, and Japan.

Despite its prevalence in the environment, no living organism is known to metabolize aluminium salts, but this aluminium is well tolerated by plants and animals. Because of the abundance of these salts, the potential for a biological role for them is of interest, and studies are ongoing.

Physical characteristics

Of aluminium isotopes, only is stable. This situation is common for elements with an odd atomic number. It is the only primordial aluminium isotope, i.e. the only one that has existed on Earth in its current form since the formation of the planet. It is therefore a mononuclidic element and its standard atomic weight is virtually the same as that of the isotope. This makes aluminium very useful in nuclear magnetic resonance (NMR), as its single stable isotope has a high NMR sensitivity. The standard atomic weight of aluminium is low in comparison with many other metals.

All other isotopes of aluminium are radioactive. The most stable of these is : while it was present along with stable ²⁷Al in the interstellar medium from which the Solar System formed, having been produced by stellar nucleosynthesis as well, its half-life is only 717,000 years and therefore a detectable amount has not survived since the formation of the planet. However, minute traces of ²⁶Al are produced from argon in the atmosphere by spallation caused by cosmic ray protons. The ratio of ²⁶Al to has been used for radiodating of geological processes over 10 ⁵ to 10 ⁶ year time scales, in particular transport, deposition, sediment storage, burial times, and erosion. Most meteorite scientists believe that the energy released by the decay of ²⁶Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.

The remaining isotopes of aluminium, with mass numbers ranging from 22 to 43, all have half-lives well under an hour. Three metastable states are known, all with half-lives under a minute.

Electron shell

An aluminium atom has 13 electrons, arranged in an electron configuration of , with three electrons beyond a stable noble gas configuration. Accordingly, the combined first three ionization energies of aluminium are far lower than the fourth ionization energy alone. Such an electron configuration is shared with the other well-characterized members of its group, boron, gallium, indium, and thallium; it is also expected for nihonium. Aluminium can surrender its three outermost electrons in many chemical reactions (see below). The electronegativity of aluminium is 1.61 (Pauling scale).

A free aluminium atom has a radius of 143 pm. With the three outermost electrons removed, the radius shrinks to 39 pm for a 4-coordinated atom or 53.5 pm for a 6-coordinated atom. At standard temperature and pressure, aluminium atoms (when not affected by atoms of other elements) form a face-centered cubic crystal system bound by metallic bonding provided by atoms' outermost electrons; hence aluminium (at these conditions) is a metal. This crystal system is shared by many other metals, such as lead and copper; the size of a unit cell of aluminium is comparable to that of those other metals. The system, however, is not shared by the other members of its group; boron has ionization energies too high to allow metallization, thallium has a hexagonal close-packed structure, and gallium and indium have unusual structures that are not close-packed like those of aluminium and thallium. The few electrons that are available for metallic bonding in aluminium are a probable cause for it being soft with a low melting point and low electrical resistivity.

Aluminium metal has an appearance ranging from silvery white to dull gray depending on its surface roughness. Aluminium mirrors are the most reflective of all metal mirrors for near ultraviolet and far infrared light. It is also one of the most reflective for light in the visible spectrum, nearly on par with silver in this respect, and the two therefore look similar. Aluminium is also good at reflecting solar radiation, although prolonged exposure to sunlight in air adds wear to the surface of the metal; this may be prevented if aluminium is anodized, which adds a protective layer of oxide on the surface.

The density of aluminium is 2.70 g/cm ³, about 1/3 that of steel, much lower than other commonly encountered metals, making aluminium parts easily identifiable through their lightness. Aluminium's low density compared to most other metals arises from the fact that its nuclei are much lighter, while difference in the unit cell size does not compensate for this difference. The only lighter metals are the metals of groups 1 and 2, which apart from beryllium and magnesium are too reactive for structural use (and beryllium is very toxic). Aluminium is not as strong or stiff as steel, but the low density makes up for this in the aerospace industry and for many other applications where light weight and relatively high strength are crucial.

Pure aluminium is quite soft and lacking in strength. In most applications various aluminium alloys are used instead because of their higher strength and hardness. The yield strength of pure aluminium is 7-11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa. Aluminium is ductile, with a percent elongation of 50-70%, and malleable allowing it to be easily drawn and extruded. It is also easily machined and cast.

Aluminium is an excellent thermal and electrical conductor, having around 60% the conductivity of copper, both thermal and electrical, while having only 30% of copper's density. Aluminium is capable of superconductivity, with a superconducting critical temperature of 1.2 kelvin and a critical magnetic field of about 100 gauss (10 milliteslas). It is paramagnetic and thus essentially unaffected by static magnetic fields. The high electrical conductivity, however, means that it is strongly affected by alternating magnetic fields through the induction of eddy currents.

Aluminium combines characteristics of pre- and post-transition metals. Since it has few available electrons for metallic bonding, like its heavier group 13 congeners, it has the characteristic physical properties of a post-transition metal, with longer-than-expected interatomic distances. Furthermore, as Al ³⁺ is a small and highly charged cation, it is strongly polarizing and bonding in aluminium compounds tends towards covalency; this behavior is similar to that of beryllium (Be ²⁺), and the two display an example of a diagonal relationship.

The underlying core under aluminium's valence shell is that of the preceding noble gas, whereas those of its heavier congeners gallium, indium, thallium, and nihonium also include a filled d-subshell and in some cases a filled f-subshell. Hence, the inner electrons of aluminium shield the valence electrons almost completely, unlike those of aluminium's heavier congeners. As such, aluminium is the most electropositive metal in its group, and its hydroxide is in fact more basic than that of gallium. Aluminium also bears minor similarities to the metalloid boron in the same group: AlX ₃ compounds are valence isoelectronic to BX ₃ compounds (they have the same valence electronic structure), and both behave as Lewis acids and readily form adducts. Additionally, one of the main motifs of boron chemistry is regular icosahedral structures, and aluminium forms an important part of many icosahedral quasicrystal alloys, including the Al-Zn-Mg class.

Aluminium has a high chemical affinity to oxygen, which renders it suitable for use as a reducing agent in the thermite reaction. A fine powder of aluminium reacts explosively on contact with liquid oxygen; under normal conditions, however, aluminium forms a thin oxide layer (~5 nm at room temperature) that protects the metal from further corrosion by oxygen, water, or dilute acid, a process termed passivation. Because of its general resistance to corrosion, aluminium is one of the few metals that retains silvery reflectance in finely powdered form, making it an important component of silver-colored paints. Aluminium is not attacked by oxidizing acids because of its passivation. This allows aluminium to be used to store reagents such as nitric acid, concentrated sulfuric acid, and some organic acids.

In hot concentrated hydrochloric acid, aluminium reacts with water with evolution of hydrogen, and in aqueous sodium hydroxide or potassium hydroxide at room temperature to form aluminates-protective passivation under these conditions is negligible. Aqua regia also dissolves aluminium. Aluminium is corroded by dissolved chlorides, such as common sodium chloride, which is why household plumbing is never made from aluminium. The oxide layer on aluminium is also destroyed by contact with mercury due to amalgamation or with salts of some electropositive metals. As such, the strongest aluminium alloys are less corrosion-resistant due to galvanic reactions with alloyed copper, and aluminium's corrosion resistance is greatly reduced by aqueous salts, particularly in the presence of dissimilar metals.

Aluminium reacts with most nonmetals upon heating, forming compounds such as aluminium nitride (AlN), aluminium sulfide (Al ₂S ₃), and the aluminium halides (AlX ₃). It also forms a wide range of intermetallic compounds involving metals from every group on the periodic table.

Inorganic compounds

The vast majority of compounds, including all aluminium-containing minerals and all commercially significant aluminium compounds, feature aluminium in the oxidation state 3+. The coordination number of such compounds varies, but generally Al ³⁺ is either six- or four-coordinate. Almost all compounds of aluminium(III) are colorless.

Aluminium hydrolysis as a function of pH. Coordinated water molecules are omitted. (Data from Baes and Mesmer)[44]

In aqueous solution, Al ³⁺ exists as the hexaaqua cation [Al(H ₂O) ₆] ³⁺, which has an approximate of 10 −5. Such solutions are acidic as this cation can act as a proton donor and progressively hydrolyze until a precipitate of aluminium hydroxide, Al(OH) ₃, forms. This is useful for clarification of water, as the precipitate nucleates on suspended particles in the water, hence removing them. Increasing the pH even further leads to the hydroxide dissolving again as aluminate, [Al(H ₂O) ₂(OH) ₄] −, is formed.

Aluminium hydroxide forms both salts and aluminates and dissolves in acid and alkali, as well as on fusion with acidic and basic oxides. This behavior of Al(OH) ₃ is termed amphoterism and is characteristic of weakly basic cations that form insoluble hydroxides and whose hydrated species can also donate their protons. One effect of this is that aluminium salts with weak acids are hydrolyzed in water to the aquated hydroxide and the corresponding nonmetal hydride: for example, aluminium sulfide yields hydrogen sulfide. However, some salts like aluminium carbonate exist in aqueous solution but are unstable as such; and only incomplete hydrolysis takes place for salts with strong acids, such as the halides, nitrate, and sulfate. For similar reasons, anhydrous aluminium salts cannot be made by heating their "hydrates": hydrated aluminium chloride is in fact not AlCl ₃·6H ₂O but [Al(H ₂O) ₆]Cl ₃, and the Al-O bonds are so strong that heating is not sufficient to break them and form Al-Cl bonds instead:

All four trihalides are well known. Unlike the structures of the three heavier trihalides, aluminium fluoride (AlF ₃) features six-coordinate aluminium, which explains its involatility and insolubility as well as high heat of formation. Each aluminium atom is surrounded by six fluorine atoms in a distorted octahedral arrangement, with each fluorine atom being shared between the corners of two octahedra. Such {AlF ₆} units also exist in complex fluorides such as cryolite, Na ₃AlF ₆. AlF ₃ melts at 1,290 °C (2,354 °F) and is made by reaction of aluminium oxide with hydrogen fluoride gas at 700 °C (1,300 °F).

With heavier halides, the coordination numbers are lower. The other trihalides are dimeric or polymeric with tetrahedral four-coordinate aluminium centers. Aluminium trichloride (AlCl ₃) has a layered polymeric structure below its melting point of 192.4 °C (378 °F) but transforms on melting to Al ₂Cl ₆ dimers. At higher temperatures those increasingly dissociate into trigonal planar AlCl ₃ monomers similar to the structure of . Aluminium tribromide and aluminium triiodide form Al ₂X ₆ dimers in all three phases and hence do not show such significant changes of properties upon phase change. These materials are prepared by treating aluminium with the halogen. The aluminium trihalides form many addition compounds or complexes; their Lewis acidic nature makes them useful as catalysts for the Friedel-Crafts reactions. Aluminium trichloride has major industrial uses involving this reaction, such as in the manufacture of anthraquinones and styrene; it is also often used as the precursor for many other aluminium compounds and as a reagent for converting nonmetal fluorides into the corresponding chlorides (a transhalogenation reaction).

Aluminium forms one stable oxide with the chemical formula Al ₂O ₃, commonly called alumina. It can be found in nature in the mineral corundum, α-alumina; there is also a γ-alumina phase. Its crystalline form, corundum, is very hard ( Mohs hardness 9), has a high melting point of 2,045 °C (3,713 °F), has very low volatility, is chemically inert, and a good electrical insulator, it is often used in abrasives (such as toothpaste), as a refractory material, and in ceramics, as well as being the starting material for the electrolytic production of aluminium. Sapphire and ruby are impure corundum contaminated with trace amounts of other metals. The two main oxide-hydroxides, AlO(OH), are boehmite and diaspore. There are three main trihydroxides: bayerite, gibbsite, and nordstrandite, which differ in their crystalline structure ( polymorphs). Many other intermediate and related structures are also known. Most are produced from ores by a variety of wet processes using acid and base. Heating the hydroxides leads to formation of corundum. These materials are of central importance to the production of aluminium and are themselves extremely useful. Some mixed oxide phases are also very useful, such as spinel (MgAl ₂O ₄), Na-β-alumina (NaAl ₁₁O ₁₇), and tricalcium aluminate (Ca ₃Al ₂O ₆, an important mineral phase in Portland cement).

The only stable chalcogenides under normal conditions are aluminium sulfide (Al ₂S ₃), selenide (Al ₂Se ₃), and telluride (Al ₂Te ₃). All three are prepared by direct reaction of their elements at about 1,000 °C (1,800 °F) and quickly hydrolyze completely in water to yield aluminium hydroxide and the respective hydrogen chalcogenide. As aluminium is a small atom relative to these chalcogens, these have four-coordinate tetrahedral aluminium with various polymorphs having structures related to wurtzite, with two-thirds of the possible metal sites occupied either in an orderly (α) or random (β) fashion; the sulfide also has a γ form related to γ-alumina, and an unusual high-temperature hexagonal form where half the aluminium atoms have tetrahedral four-coordination and the other half have trigonal bipyramidal five-coordination.

Four pnictides - aluminium nitride (AlN), aluminium phosphide (AlP), aluminium arsenide (AlAs), and aluminium antimonide (AlSb) - are known. They are all III-V semiconductors isoelectronic to silicon and germanium, all of which but AlN have the zinc blende structure. All four can be made by high-temperature (and possibly high-pressure) direct reaction of their component elements.

Aluminium alloys well with most other metals (with the exception of most alkali metals and group 13 metals) and over 150 intermetallics with other metals are known. Preparation involves heating fixed metals together in certain proportion, followed by gradual cooling and annealing. Bonding in them is predominantly metallic and the crystal structure primarily depends on efficiency of packing.

There are few compounds with lower oxidation states. A few aluminium(I) compounds exist: AlF, AlCl, AlBr, and AlI exist in the gaseous phase when the respective trihalide is heated with aluminium, and at cryogenic temperatures. A stable derivative of aluminium monoiodide is the cyclic adduct formed with triethylamine, Al ₄I ₄(NEt ₃) ₄. Al ₂O and Al ₂S also exist but are very unstable. Very simple aluminium(II) compounds are invoked or observed in the reactions of Al metal with oxidants. For example, aluminium monoxide, AlO, has been detected in the gas phase after explosion and in stellar absorption spectra. More thoroughly investigated are compounds of the formula R ₄Al ₂ which contain an Al-Al bond and where R is a large organic ligand.

Organoaluminium compounds and related hydrides

Structure of trimethylaluminium, a compound that features five-coordinate carbon.

A variety of compounds of empirical formula AlR ₃ and AlR 1.5Cl 1.5 exist. The aluminium trialkyls and triaryls are reactive, volatile, and colorless liquids or low-melting solids. They catch fire spontaneously in air and react with water, thus necessitating precautions when handling them. They often form dimers, unlike their boron analogues, but this tendency diminishes for branched-chain alkyls (e.g. , , Me ₃CCH ₂); for example, triisobutylaluminium exists as an equilibrium mixture of the monomer and dimer. These dimers, such as trimethylaluminium (Al ₂Me ₆), usually feature tetrahedral Al centers formed by dimerization with some alkyl group bridging between both aluminium atoms. They are hard acids and react readily with ligands, forming adducts. In industry, they are mostly used in alkene insertion reactions, as discovered by Karl Ziegler, most importantly in "growth reactions" that form long-chain unbranched primary alkenes and alcohols, and in the low-pressure polymerization of ethene and propene. There are also some heterocyclic and cluster organoaluminium compounds involving Al-N bonds.

The industrially most important aluminium hydride is lithium aluminium hydride (LiAlH ₄), which is used in as a reducing agent in organic chemistry. It can be produced from lithium hydride and aluminium trichloride. The simplest hydride, aluminium hydride or alane, is not as important. It is a polymer with the formula (AlH ₃)n, in contrast to the corresponding boron hydride that is a dimer with the formula (BH ₃) ₂.

Natural occurrence

Aluminium's per-particle abundance in the Solar System is 3.15 ppm (parts per million). It is the twelfth most abundant of all elements and third most abundant among the elements that have odd atomic numbers, after hydrogen and nitrogen. The only stable isotope of aluminium, ²⁷Al, is the eighteenth most abundant nucleus in the universe. It is created almost entirely after fusion of carbon in massive stars that will later become Type II supernovas: this fusion creates ²⁶Mg, which upon capturing free protons and neutrons, becomes aluminium. Some smaller quantities of ²⁷Al are created in hydrogen burning shells of evolved stars, where ²⁶Mg can capture free protons. Essentially all aluminium now in existence is ²⁷Al. ²⁶Al was present in the early Solar System with abundance of 0.005% relative to ²⁷Al but its half-life of 728,000 years is too short for any original nuclei to survive; ²⁶Al is therefore extinct. Unlike for ²⁷Al, hydrogen burning is the primary source of ²⁶Al, with the nuclide emerging after a nucleus of ²⁵Mg catches a free proton. However, the trace quantities of ²⁶Al that do exist are the most common gamma ray emitter in the interstellar gas; if the original ²⁶Al were still present, gamma ray maps of the Milky Way would be brighter.

Overall, the Earth is about 1.59% aluminium by mass (seventh in abundance by mass). Aluminium occurs in greater proportion in the Earth's crust than in the universe at large. This is because aluminium easily forms the oxide and becomes bound into rocks and stays in the Earth's crust, while less reactive metals sink to the core. In the Earth's crust, aluminium is the most abundant metallic element (8.23% by mass) and the third most abundant of all elements (after oxygen and silicon). A large number of silicates in the Earth's crust contain aluminium. In contrast, the Earth's mantle is only 2.38% aluminium by mass. Aluminium also occurs in seawater at a concentration of 2 μg/kg.

Because of its strong affinity for oxygen, aluminium is almost never found in the elemental state; instead it is found in oxides or silicates. Feldspars, the most common group of minerals in the Earth's crust, are aluminosilicates. Aluminium also occurs in the minerals beryl, cryolite, garnet, spinel, and turquoise. Impurities in Al ₂O ₃, such as chromium and iron, yield the gemstones ruby and sapphire, respectively. Native aluminium metal is extremely rare and can only be found as a minor phase in low oxygen fugacity environments, such as the interiors of certain volcanoes. Native aluminium has been reported in cold seeps in the northeastern continental slope of the South China Sea. It is possible that these deposits resulted from bacterial reduction of tetrahydroxoaluminate Al(OH) ₄−.

Although aluminium is a common and widespread element, not all aluminium minerals are economically viable sources of the metal. Almost all metallic aluminium is produced from the ore bauxite (AlOx(OH) 3-2x). Bauxite occurs as a weathering product of low iron and silica bedrock in tropical climatic conditions. In 2017, most bauxite was mined in Australia, China, Guinea, and India.

Friedrich Wöhler, the chemist who first thoroughly described metallic elemental aluminium

The history of aluminium has been shaped by usage of alum. The first written record of alum, made by Greek historian Herodotus, dates back to the 5th century BCE. The ancients are known to have used alum as a dyeing mordant and for city defense. After the Crusades, alum, an indispensable good in the European fabric industry, was a subject of international commerce; it was imported to Europe from the eastern Mediterranean until the mid-15th century.

The nature of alum remained unknown. Around 1530, Swiss physician Paracelsus suggested alum was a salt of an earth of alum. In 1595, German doctor and chemist Andreas Libavius experimentally confirmed this. In 1722, German chemist Friedrich Hoffmann announced his belief that the base of alum was a distinct earth. In 1754, German chemist Andreas Sigismund Marggraf synthesized alumina by boiling clay in sulfuric acid and subsequently adding potash.

Attempts to produce aluminium date back to 1760. The first successful attempt, however, was completed in 1824 by Danish physicist and chemist Hans Christian Ørsted. He reacted anhydrous aluminium chloride with potassium amalgam, yielding a lump of metal looking similar to tin. He presented his results and demonstrated a sample of the new metal in 1825. In 1827, German chemist Friedrich Wöhler repeated Ørsted's experiments but did not identify any aluminium. (The reason for this inconsistency was only discovered in 1921.) He conducted a similar experiment in the same year by mixing anhydrous aluminium chloride with potassium and produced a powder of aluminium. In 1845, he was able to produce small pieces of the metal and described some physical properties of this metal. For many years thereafter, Wöhler was credited as the discoverer of aluminium.

As Wöhler's method could not yield great quantities of aluminium, the metal remained rare; its cost exceeded that of gold. The first industrial production of aluminium was established in 1856 by French chemist Henri Etienne Sainte-Claire Deville and companions. Deville had discovered that aluminium trichloride could be reduced by sodium, which was more convenient and less expensive than potassium, which Wöhler had used. Even then, aluminium was still not of great purity and produced aluminium differed in properties by sample. Because of its electricity-conducting capacity, aluminium was used as the cap of the Washington Monument, completed in 1885. The tallest building in the world at the time, the non-corroding metal cap was intended to serve as a lightning rod peak.

The first industrial large-scale production method was independently developed in 1886 by French engineer Paul Héroult and American engineer Charles Martin Hall; it is now known as the Hall-Héroult process. The Hall-Héroult process converts alumina into metal. Austrian chemist Carl Joseph Bayer discovered a way of purifying bauxite to yield alumina, now known as the Bayer process, in 1889. Modern production of the aluminium is based on the Bayer and Hall-Héroult processes.

As large-scale production caused aluminium prices to drop, the metal became widely used in jewelry, eyeglass frames, optical instruments, tableware, and foil, and other everyday items in the 1890s and early 20th century. Aluminium's ability to form hard yet light alloys with other metals provided the metal with many uses at the time. During World War I, major governments demanded large shipments of aluminium for light strong airframes; during World War II, demand by major governments for aviation was even higher.

By the mid-20th century, aluminium had become a part of everyday life and an essential component of housewares. In 1954, production of aluminium surpassed that of copper, historically second in production only to iron, making it the most produced non-ferrous metal. During the mid-20th century, aluminium emerged as a civil engineering material, with building applications in both basic construction and interior finish work, and increasingly being used in military engineering, for both airplanes and land armor vehicle engines. Earth's first artificial satellite, launched in 1957, consisted of two separate aluminium semi-spheres joined and all subsequent space vehicles have used aluminium to some extent. The aluminium can was invented in 1956 and employed as a storage for drinks in 1958.

World production of aluminium since 1900

Throughout the 20th century, the production of aluminium rose rapidly: while the world production of aluminium in 1900 was 6,800 metric tons, the annual production first exceeded 100,000 metric tons in 1916; 1,000,000 tons in 1941; 10,000,000 tons in 1971. In the 1970s, the increased demand for aluminium made it an exchange commodity; it entered the London Metal Exchange, the oldest industrial metal exchange in the world, in 1978. The output continued to grow: the annual production of aluminium exceeded 50,000,000 metric tons in 2013.

The real price for aluminium declined from $14,000 per metric ton in 1900 to $2,340 in 1948 (in 1998 United States dollars). Extraction and processing costs were lowered over technological progress and the scale of the economies. However, the need to exploit lower-grade poorer quality deposits and the use of fast increasing input costs (above all, energy) increased the net cost of aluminium; the real price began to grow in the 1970s with the rise of energy cost. Production moved from the industrialized countries to countries where production was cheaper. Production costs in the late 20th century changed because of advances in technology, lower energy prices, exchange rates of the United States dollar, and alumina prices. The BRIC countries' combined share in primary production and primary consumption grew substantially in the first decade of the 21st century. China is accumulating an especially large share of the world's production thanks to an abundance of resources, cheap energy, and governmental stimuli; it also increased its consumption share from 2% in 1972 to 40% in 2010. In the United States, Western Europe, and Japan, most aluminium was consumed in transportation, engineering, construction, and packaging. In 2021, prices for industrial metals such as aluminium have soared to near-record levels as energy shortages in China drive up costs for electricity.

The names aluminium and aluminum are derived from the word alumine, an obsolete term for alumina, a naturally occurring oxide of aluminium. Alumine was borrowed from French, which in turn derived it from alumen, the classical Latin name for alum, the mineral from which it was collected. The Latin word alumen stems from the Proto-Indo-European root *alu- meaning "bitter" or "beer".

1897 American advertisement featuring the aluminum spelling

British chemist Humphry Davy, who performed a number of experiments aimed to isolate the metal, is credited as the person who named the element. The first name proposed for the metal to be isolated from alum was alumium, which Davy suggested in an 1808 article on his electrochemical research, published in Philosophical Transactions of the Royal Society. It appeared that the name was created from the English word alum and the Latin suffix -ium; but it was customary then to give elements names originating in Latin, so this name was not adopted universally. This name was criticized by contemporary chemists from France, Germany, and Sweden, who insisted the metal should be named for the oxide, alumina, from which it would be isolated. The English name alum does not come directly from Latin, whereas alumine/ alumina obviously comes from the Latin word alumen (upon declension, alumen changes to alumin-).

One example was Essai sur la Nomenclature chimique (July 1811), written in French by a Swedish chemist, Jöns Jacob Berzelius, in which the name aluminium is given to the element that would be synthesized from alum. (Another article in the same journal issue also refers to the metal whose oxide is the basis of sapphire, i.e. the same metal, as to aluminium.) A January 1811 summary of one of Davy's lectures at the Royal Society mentioned the name aluminium as a possibility. The next year, Davy published a chemistry textbook in which he used the spelling aluminum. Both spellings have coexisted since. Their usage is currently regional: aluminum dominates in the United States and Canada; aluminium is prevalent in the rest of the English-speaking world.

In 1812, British scientist Thomas Young wrote an anonymous review of Davy's book, in which he proposed the name aluminium instead of aluminum, which he thought had a "less classical sound". This name persisted: although the spelling was occasionally used in Britain, the American scientific language used from the start. Most scientists throughout the world used in the 19th century; and it was entrenched in several other European languages, such as French, German, and Dutch. In 1828, an American lexicographer, Noah Webster, entered only the aluminum spelling in his American Dictionary of the English Language. In the 1830s, the spelling gained usage in the United States; by the 1860s, it had become the more common spelling there outside science. In 1892, Hall used the spelling in his advertising handbill for his new electrolytic method of producing the metal, despite his constant use of the spelling in all the patents he filed between 1886 and 1903: it is unknown whether this spelling was introduced by mistake or intentionally; but Hall preferred aluminum since its introduction because it resembled , the name of a prestigious metal. By 1890, both spellings had been common in the United States, the spelling being slightly more common; by 1895, the situation had reversed; by 1900, aluminum had become twice as common as aluminium; in the next decade, the spelling dominated American usage. In 1925, the American Chemical Society adopted this spelling.

The International Union of Pure and Applied Chemistry (IUPAC) adopted aluminium as the standard international name for the element in 1990. In 1993, they recognized aluminum as an acceptable variant; the most recent 2005 edition of the IUPAC nomenclature of inorganic chemistry also acknowledges this spelling. IUPAC official publications use the spelling as primary, and they list both where it is appropriate.

Production and refinement

The production of aluminium starts with the extraction of bauxite rock from the ground. The bauxite is processed and transformed using the Bayer process into alumina, which is then processed using the Hall-Héroult process, resulting in the final aluminium.

Aluminium production is highly energy-consuming, and so the producers tend to locate smelters in places where electric power is both plentiful and inexpensive. Production of one kilogram of aluminium requires 7 kilograms of oil energy equivalent, as compared to 1.5 kilograms for steel and 2 kilograms for plastic. As of 2019, the world's largest smelters of aluminium are located in China, India, Russia, Canada, and the United Arab Emirates, while China is by far the top producer of aluminium with a world share of fifty-five percent.

According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of aluminium in use in society (i.e. in cars, buildings, electronics, etc.) is 80 kg (180 lb). Much of this is in more-developed countries (350-500 kg (770-1,100 lb) per capita) rather than less-developed countries (35 kg (77 lb) per capita).

Bayer process

Bauxite is converted to alumina by the Bayer process. Bauxite is blended for uniform composition and then is ground. The resulting slurry is mixed with a hot solution of sodium hydroxide; the mixture is then treated in a digester vessel at a pressure well above atmospheric, dissolving the aluminium hydroxide in bauxite while converting impurities into relatively insoluble compounds:

After this reaction, the slurry is at a temperature above its atmospheric boiling point. It is cooled by removing steam as pressure is reduced. The bauxite residue is separated from the solution and discarded. The solution, free of solids, is seeded with small crystals of aluminium hydroxide; this causes decomposition of the [Al(OH) ₄] − ions to aluminium hydroxide. After about half of aluminium has precipitated, the mixture is sent to classifiers. Small crystals of aluminium hydroxide are collected to serve as seeding agents; coarse particles are converted to alumina by heating; the excess solution is removed by evaporation, (if needed) purified, and recycled.

Hall-Héroult process

Extrusion billets of aluminium

The conversion of alumina to aluminium is achieved by the Hall-Héroult process. In this energy-intensive process, a solution of alumina in a molten (950 and 980 °C (1,740 and 1,800 °F)) mixture of cryolite (Na ₃AlF ₆) with calcium fluoride is electrolyzed to produce metallic aluminium. The liquid aluminium sinks to the bottom of the solution and is tapped off, and usually cast into large blocks called aluminium billets for further processing.

Anodes of the electrolysis cell are made of carbon-the most resistant material against fluoride corrosion-and either bake at the process or are prebaked. The former, also called Söderberg anodes, are less power-efficient and fumes released during baking are costly to collect, which is why they are being replaced by prebaked anodes even though they save the power, energy, and labor to prebake the cathodes. Carbon for anodes should be preferably pure so that neither aluminium nor the electrolyte is contaminated with ash. Despite carbon's resistivity against corrosion, it is still consumed at a rate of 0.4-0.5 kg per each kilogram of produced aluminium. Cathodes are made of anthracite; high purity for them is not required because impurities leach only very slowly. The cathode is consumed at a rate of 0.02-0.04 kg per each kilogram of produced aluminium. A cell is usually terminated after 2-6 years following a failure of the cathode.

The Hall-Heroult process produces aluminium with a purity of above 99%. Further purification can be done by the Hoopes process. This process involves the electrolysis of molten aluminium with a sodium, barium, and aluminium fluoride electrolyte. The resulting aluminium has a purity of 99.99%.

Electric power represents about 20 to 40% of the cost of producing aluminium, depending on the location of the smelter. Aluminium production consumes roughly 5% of electricity generated in the United States. Because of this, alternatives to the Hall-Héroult process have been researched, but none has turned out to be economically feasible.

Common bins for recyclable waste along with a bin for unrecyclable waste. The bin with a yellow top is labeled "aluminum". Rhodes, Greece.

Recovery of the metal through recycling has become an important task of the aluminium industry. Recycling was a low-profile activity until the late 1960s, when the growing use of aluminium beverage cans brought it to public awareness. Recycling involves melting the scrap, a process that requires only 5% of the energy used to produce aluminium from ore, though a significant part (up to 15% of the input material) is lost as dross (ash-like oxide). An aluminium stack melter produces significantly less dross, with values reported below 1%.

White dross from primary aluminium production and from secondary recycling operations still contains useful quantities of aluminium that can be extracted industrially. The process produces aluminium billets, together with a highly complex waste material. This waste is difficult to manage. It reacts with water, releasing a mixture of gases (including, among others, hydrogen, acetylene, and ammonia), which spontaneously ignites on contact with air; contact with damp air results in the release of copious quantities of ammonia gas. Despite these difficulties, the waste is used as a filler in asphalt and concrete.

Applications

Aluminium-bodied Austin A40 Sports (c. 1951)

The global production of aluminium in 2016 was 58.8 million metric tons. It exceeded that of any other metal except iron (1,231 million metric tons).

Aluminium is almost always alloyed, which markedly improves its mechanical properties, especially when tempered. For example, the common aluminium foils and beverage cans are alloys of 92% to 99% aluminium. The main alloying agents are copper, zinc, magnesium, manganese, and silicon (e.g., duralumin) with the levels of other metals in a few percent by weight. Aluminium, both wrought and cast, has been alloyed with: manganese, silicon, magnesium, copper and zinc among others. For example, the Kynal family of alloys was developed by the British chemical manufacturer Imperial Chemical Industries.

Aluminium can

The major uses for aluminium are in:

Transportation (automobiles, aircraft, trucks, railway cars, marine vessels, bicycles, spacecraft, etc.). Aluminium is used because of its low density;

Packaging (cans, foil, frame, etc.). Aluminium is used because it is non-toxic (see below), non-adsorptive, and splinter-proof;

Building and construction (windows, doors, siding, building wire, sheathing, roofing, etc.). Since steel is cheaper, aluminium is used when lightness, corrosion resistance, or engineering features are important;

Electricity-related uses (conductor alloys, motors, and generators, transformers, capacitors, etc.). Aluminium is used because it is relatively cheap, highly conductive, has adequate mechanical strength and low density, and resists corrosion;

A wide range of household items, from cooking utensils to furniture. Low density, good appearance, ease of fabrication, and durability are the key factors of aluminium usage;

Machinery and equipment (processing equipment, pipes, tools). Aluminium is used because of its corrosion resistance, non-pyrophoricity, and mechanical strength.

The great majority (about 90%) of aluminium oxide is converted to metallic aluminium. Being a very hard material ( Mohs hardness 9), alumina is widely used as an abrasive; being extraordinarily chemically inert, it is useful in highly reactive environments such as high pressure sodium lamps. Aluminium oxide is commonly used as a catalyst for industrial processes; e.g. the Claus process to convert hydrogen sulfide to sulfur in refineries and to alkylate amines. Many industrial catalysts are supported by alumina, meaning that the expensive catalyst material is dispersed over a surface of the inert alumina. Another principal use is as a drying agent or absorbent.

Laser deposition of alumina on a substrate

Several sulfates of aluminium have industrial and commercial application. Aluminium sulfate (in its hydrate form) is produced on the annual scale of several millions of metric tons. About two-thirds is consumed in water treatment. The next major application is in the manufacture of paper. It is also used as a mordant in dyeing, in pickling seeds, deodorizing of mineral oils, in leather tanning, and in production of other aluminium compounds. Two kinds of alum, ammonium alum and potassium alum, were formerly used as mordants and in leather tanning, but their use has significantly declined following availability of high-purity aluminium sulfate. Anhydrous aluminium chloride is used as a catalyst in chemical and petrochemical industries, the dyeing industry, and in synthesis of various inorganic and organic compounds. Aluminium hydroxychlorides are used in purifying water, in the paper industry, and as antiperspirants. Sodium aluminate is used in treating water and as an accelerator of solidification of cement.

Many aluminium compounds have niche applications, for example:

Aluminium acetate in solution is used as an astringent.

Aluminium phosphate is used in the manufacture of glass, ceramic, pulp and paper products, cosmetics, paints, varnishes, and in dental cement.

Aluminium hydroxide is used as an antacid, and mordant; it is used also in water purification, the manufacture of glass and ceramics, and in the waterproofing of fabrics.

Lithium aluminium hydride is a powerful reducing agent used in organic chemistry.

Organoaluminiums are used as Lewis acids and co-catalysts.

Methylaluminoxane is a co-catalyst for Ziegler-Natta olefin polymerization to produce vinyl polymers such as polyethene.

Aqueous aluminium ions (such as aqueous aluminium sulfate) are used to treat against fish parasites such as Gyrodactylus salaris.

In many vaccines, certain aluminium salts serve as an immune adjuvant (immune response booster) to allow the protein in the vaccine to achieve sufficient potency as an immune stimulant. Until 2004, most of the adjuvants used in vaccines were aluminium-adjuvanted.

Schematic of aluminium absorption by human skin.[169]

Despite its widespread occurrence in the Earth's crust, aluminium has no known function in biology. At pH 6-9 (relevant for most natural waters), aluminium precipitates out of water as the hydroxide and is hence not available; most elements behaving this way have no biological role or are toxic. Aluminium sulfate has an of 6207 mg/kg (oral, mouse), which corresponds to 435 grams (about one pound) for a 70 kg (150 lb) person.

Aluminium is classified as a non-carcinogen by the United States Department of Health and Human Services. A review published in 1988 said that there was little evidence that normal exposure to aluminium presents a risk to healthy adult, and a 2014 multi-element toxicology review was unable to find deleterious effects of aluminium consumed in amounts not greater than 40 mg/day per kg of body mass. Most aluminium consumed will leave the body in feces; most of the small part of it that enters the bloodstream, will be excreted via urine; nevertheless some aluminium does pass the blood-brain barrier and is lodged preferentially in the brains of Alzheimer's patients. Evidence published in 1989 indicates that, for Alzheimer's patients, aluminium may act by electrostatically crosslinking proteins, thus down-regulating genes in the superior temporal gyrus.

Aluminium, although rarely, can cause vitamin D-resistant osteomalacia, erythropoietin-resistant microcytic anemia, and central nervous system alterations. People with kidney insufficiency are especially at a risk. Chronic ingestion of hydrated aluminium silicates (for excess gastric acidity control) may result in aluminium binding to intestinal contents and increased elimination of other metals, such as iron or zinc; sufficiently high doses (>50 g/day) can cause anemia.

There are five major aluminium forms absorbed by human body: the free solvated trivalent cation (Al³⁺(aq)); low-molecular-weight, neutral, soluble complexes (LMW-Al⁰(aq)); high-molecular-weight, neutral, soluble complexes (HMW-Al⁰(aq)); low-molecular-weight, charged, soluble complexes (LMW-Al(L)n+/−(aq)); nano and micro-particulates (Al(L)n(s)). They are transported across cell membranes or cell epi-/endothelia through five major routes: (1) paracellular; (2) transcellular; (3) active transport; (4) channels; (5) adsorptive or receptor-mediated endocytosis.[169]

During the 1988 Camelford water pollution incident people in Camelford had their drinking water contaminated with aluminium sulfate for several weeks. A final report into the incident in 2013 concluded it was unlikely that this had caused long-term health problems.

Aluminium has been suspected of being a possible cause of Alzheimer's disease, but research into this for over 40 years has found, as of 2018, no good evidence of causal effect.

Aluminium increases estrogen-related gene expression in human breast cancer cells cultured in the laboratory. In very high doses, aluminium is associated with altered function of the blood-brain barrier. A small percentage of people have contact allergies to aluminium and experience itchy red rashes, headache, muscle pain, joint pain, poor memory, insomnia, depression, asthma, irritable bowel syndrome, or other symptoms upon contact with products containing aluminium.

Exposure to powdered aluminium or aluminium welding fumes can cause pulmonary fibrosis. Fine aluminium powder can ignite or explode, posing another workplace hazard.

Exposure routes

Food is the main source of aluminium. Drinking water contains more aluminium than solid food; however, aluminium in food may be absorbed more than aluminium from water. Major sources of human oral exposure to aluminium include food (due to its use in food additives, food and beverage packaging, and cooking utensils), drinking water (due to its use in municipal water treatment), and aluminium-containing medications (particularly antacid/antiulcer and buffered aspirin formulations). Dietary exposure in Europeans averages to 0.2-1.5 mg/kg/week but can be as high as 2.3 mg/kg/week. Higher exposure levels of aluminium are mostly limited to miners, aluminium production workers, and dialysis patients.

Consumption of antacids, antiperspirants, vaccines, and cosmetics provide possible routes of exposure. Consumption of acidic foods or liquids with aluminium enhances aluminium absorption, and maltol has been shown to increase the accumulation of aluminium in nerve and bone tissues.

In case of suspected sudden intake of a large amount of aluminium, the only treatment is deferoxamine mesylate which may be given to help eliminate aluminium from the body by chelation. However, this should be applied with caution as this reduces not only aluminium body levels, but also those of other metals such as copper or iron.

Environmental effects

High levels of aluminium occur near mining sites; small amounts of aluminium are released to the environment at the coal-fired power plants or incinerators. Aluminium in the air is washed out by the rain or normally settles down but small particles of aluminium remain in the air for a long time.

Acidic precipitation is the main natural factor to mobilize aluminium from natural sources and the main reason for the environmental effects of aluminium; however, the main factor of presence of aluminium in salt and freshwater are the industrial processes that also release aluminium into air.

In water, aluminium acts as a toxiс agent on gill-breathing animals such as fish when the water is acidic, in which aluminium may precipitate on gills, which causes loss of plasma- and hemolymph ions leading to osmoregulatory failure. Organic complexes of aluminium may be easily absorbed and interfere with metabolism in mammals and birds, even though this rarely happens in practice.

Aluminium is primary among the factors that reduce plant growth on acidic soils. Although it is generally harmless to plant growth in pH-neutral soils, in acid soils the concentration of toxic Al ³⁺ cations increases and disturbs root growth and function. Wheat has developed a tolerance to aluminium, releasing organic compounds that bind to harmful aluminium cations. Sorghum is believed to have the same tolerance mechanism.

Aluminium production possesses its own challenges to the environment on each step of the production process. The major challenge is the greenhouse gas emissions. These gases result from electrical consumption of the smelters and the byproducts of processing. The most potent of these gases are perfluorocarbons from the smelting process. Released sulfur dioxide is one of the primary precursors of acid rain.

Biodegradation of metallic aluminium is extremely rare; most aluminium-corroding organisms do not directly attack or consume the aluminium, but instead produce corrosive wastes. The fungus Geotrichum candidum can consume the aluminium in compact discs. The bacterium Pseudomonas aeruginosa and the fungus Cladosporium resinae are commonly detected in aircraft fuel tanks that use kerosene-based fuels (not avgas), and laboratory cultures can degrade aluminium.

References

Bibliography

Davis, J. R. (1999). Corrosion of Aluminum and Aluminum Alloys. ASM International. ISBN 978-1-61503-238-9.

Dean, J. A. (1999). Lange's handbook of chemistry (15 ed.). McGraw-Hill. ISBN 978-0-07-016384-3. OCLC 40213725.

Drozdov, A. (2007). Aluminium: The Thirteenth Element. RUSAL Library. ISBN 978-5-91523-002-5.

Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

King, R. B. (1995). Inorganic Chemistry of Main Group Elements. Wiley-VCH. ISBN 978-0-471-18602-1.

Nappi, C. (2013). The global aluminium industry 40 years from 1972 (PDF) (Report). International Aluminium Institute. Archived (PDF) from the original on 9 October 2022.

Richards, J. W. (1896). Aluminium: Its history, occurrence, properties, metallurgy and applications, including its alloys (3 ed.). Henry Carey Baird & Co.

Schmitz, C. (2006). Handbook of Aluminium Recycling. Vulkan-Verlag GmbH. ISBN 978-3-8027-2936-2.

Further reading

Mimi Sheller, Aluminum Dream: The Making of Light Modernity. Cambridge, Mass.: Massachusetts Institute of Technology Press, 2014.

External links

# data[].attributes.attachment_link.description
Pronunciation Alternative name Aluminum (U.S., Canada) Appearance Silvery gray metallic (Atomic number Z) 13 Group group 13 (boron group) Period period 3 Block p-block Electron configuration [ Ne] 3s 2 3p 1 Electrons per shell 2, 8, 3 at Phase STP solid Melting point 933.47 K ​(660.32 °C, ​1220.58 °F) Density (at 20° C) 2.699 g/cm 3 [4] when liquid (at m.p.)

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Polypropylene ( PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene.

Polypropylene belongs to the group of polyolefins and is partially crystalline and non-polar. Its properties are similar to polyethylene, but it is slightly harder and more heat resistant. It is a white, mechanically rugged material and has a high chemical resistance.

Polypropylene is the second-most widely produced commodity plastic (after polyethylene). In 2019, the global market for polypropylene was worth $126.03 billion. Revenues are expected to exceed US$145 billion by 2019. The sales of this material are forecast to grow at a rate of 5.8% per year until 2021.

Phillips Petroleum chemists J. Paul Hogan and Robert Banks first demonstrated the polymerization of propylene in 1951. The stereoselective polymerization to the isotactic was discovered by Giulio Natta and Karl Rehn in March 1954. This pioneering discovery led to large-scale commercial production of isotactic polypropylene by the Italian firm Montecatini from 1957 onwards. Syndiotactic polypropylene was also first synthesized by Natta.

Chemical and physical properties

Polypropylene is in many aspects similar to polyethylene, especially in solution behaviour and electrical properties. The methyl group improves mechanical properties and thermal resistance, although the chemical resistance decreases. The properties of polypropylene depend on the molecular weight and molecular weight distribution, crystallinity, type and proportion of comonomer (if used) and the iso tacticity. In isotactic polypropylene, for example, the methyl groups are oriented on one side of the carbon backbone. This arrangement creates a greater degree of crystallinity and results in a stiffer material that is more resistant to creep than both atactic polypropylene and polyethylene.

The density of (PP) is between 0.895 and 0.92 g/cm³. Therefore, PP is the commodity plastic with the lowest density. With lower density, moldings parts with lower weight and more parts of a certain mass of plastic can be produced. Unlike polyethylene, crystalline and amorphous regions differ only slightly in their density. However, the density of polyethylene can significantly change with fillers.

The Young's modulus of PP is between 1300 and 1800 N/mm².

Polypropylene is normally tough and flexible, especially when copolymerized with ethylene. This allows polypropylene to be used as an engineering plastic, competing with materials such as acrylonitrile butadiene styrene (ABS). Polypropylene is reasonably economical.

The melting point of polypropylene occurs in a range, so the melting point is determined by finding the highest temperature of a differential scanning calorimetry chart. Perfectly isotactic PP has a melting point of 171 °C (340 °F). Commercial isotactic PP has a melting point that ranges from 160 to 166 °C (320 to 331 °F), depending on atactic material and crystallinity. Syndiotactic PP with a crystallinity of 30% has a melting point of 130 °C (266 °F). Below 0 °C, PP becomes brittle.

The thermal expansion of PP is very large, but somewhat less than that of polyethylene.

Polypropylene at room temperature is resistant to fats and almost all organic solvents, apart from strong oxidants. Non-oxidizing acids and bases can be stored in containers made of PP. At elevated temperature, PP can be dissolved in nonpolar solvents such as xylene, tetralin and decalin. Due to the tertiary carbon atom PP is chemically less resistant than PE (see Markovnikov rule).

Most commercial polypropylene is isotactic and has an intermediate level of crystallinity between that of low-density polyethylene (LDPE) and high-density polyethylene (HDPE). Isotactic & atactic polypropylene is soluble in p-xylene at 140 °C. Isotactic precipitates when the solution is cooled to 25 °C and atactic portion remains soluble in p-xylene.

The melt flow rate (MFR) or melt flow index (MFI) is a measure of molecular weight of polypropylene. The measure helps to determine how easily the molten raw material will flow during processing. Polypropylene with higher MFR will fill the plastic mold more easily during the injection or blow-molding production process. As the melt flow increases, however, some physical properties, like impact strength, will decrease.

There are three general types of polypropylene: homopolymer, random copolymer, and block copolymer. The comonomer is typically used with ethylene. Ethylene-propylene rubber or EPDM added to polypropylene homopolymer increases its low temperature impact strength. Randomly polymerized ethylene monomer added to polypropylene homopolymer decreases the polymer crystallinity, lowers the melting point and makes the polymer more transparent.

Molecular structure - tacticity

Polypropylene can be categorized as atactic polypropylene (PP-at), syndiotactic polypropylene (PP-st) and isotactic polypropylene (PP-it). In case of atactic polypropylene, the methyl group (-CH₃) is randomly aligned, alternating (alternating) for syndiotactic polypropylene and evenly for isotactic polypropylene. This has an impact on the crystallinity (amorphous or semi-crystalline) and the thermal properties (expressed as glass transition point Tg and melting point Tm).

The term tacticity describes for polypropylene how the methyl group is oriented in the polymer chain. Commercial polypropylene is usually isotactic. This article therefore always refers to isotactic polypropylene, unless stated otherwise. The tacticity is usually indicated in percent, using the isotactic index (according to DIN 16774). The index is measured by determining the fraction of the polymer insoluble in boiling heptane. Commercially available polypropylenes usually have an isotactic index between 85 and 95%. The tacticity effects the polymers physical properties. As the methyl group is in isotactic propylene consistently located at the same side, it forces the macromolecule in a helical shape, as also found in starch. An isotactic structure leads to a semi-crystalline polymer. The higher the isotacticity (the isotactic fraction), the greater the crystallinity, and thus also the softening point, rigidity, e-modulus and hardness.

Atactic polypropylene, on the other hand, lacks any regularity which makes it unable to crystallize and amorphous.

Isotactic polypropylene has a high degree of crystallinity, in industrial products 30-60%. Syndiotactic polypropylene is slightly less crystalline, atactic PP is amorphous (not crystalline).

Isotactic polypropylene (iPP)

Isotactic polypropylene can exist in various crystalline modifications which differ by the molecular arrangement of the polymer chains. The crystalline modifications are categorized into the α-, β- and γ-modification as well as mesomorphic (smectic) forms. The α-modification is predominant in iPP. Such crystals are built from lamellae in the form of folded chains. A characteristic anomaly is that the lamellae are arranged in the so-called "cross-hatched" structure. The melting point of α-crystalline regions is given as 185 to 220 °C, the density as 0.936 to 0.946 g·cm −3. The β-modification is in comparison somewhat less ordered, as a result of which it forms faster and has a lower melting point of 170 to 200 °C. The formation of the β-modification can be promoted by nucleating agents, suitable temperatures and shear stress. The γ-modification is hardly formed under the conditions used in industry and is poorly understood. The mesomorphic modification, however, occurs often in industrial processing, since the plastic is usually cooled quickly. The degree of order of the mesomorphic phase ranges between the crystalline and the amorphous phase, its density is with 0.916 g·cm −3 comparatively. The mesomorphic phase is considered as cause for the transparency in rapidly cooled films (due to low order and small crystallites).

Syndiotactic polypropylene (sPP)

Syndiotactic polypropylene was discovered much later than isotactic PP and could only be prepared by using metallocene catalysts. Syndiotactic PP has a lower melting point, with 161 to 186 °C, depending on the degree of tacticity.

Atactic polypropylene (aPP)

Atactic polypropylene is amorphous and has therefore no crystal structure. Due to its lack of crystallinity, it is readily soluble even at moderate temperatures, which allows to separate it as by-product from isotactic polypropylene by extraction. However, the aPP obtained this way is not completely amorphous but can still contain 15% crystalline parts. Atactic polypropylene can also be produced selectively using metallocene catalysts, atactic polypropylene produced this way has a considerably higher molecular weight.

Atactic polypropylene has lower density, melting point and softening temperature than the crystalline types and is tacky and rubber-like at room temperature. It is a colorless, cloudy material and can be used between −15 and +120 °C. Atactic polypropylene is used as a sealant, as an insulating material for automobiles and as an additive to bitumen.

Polypropylene copolymers are in use as well. A particularly important one is polypropylene random copolymer ( PPR or PP-R), a random copolymer with polyethylene used for plastic pipework.

Polypropylene random crystallinity temperature ( PP-RCT), also used for plastic pipework, is a new form of this plastic. It achieves higher strength at high temperature by β- crystallization.

Polypropylene is liable to chain degradation from exposure to temperatures above 100 °C. Oxidation usually occurs at the tertiary carbon centers leading to chain breaking via reaction with oxygen. In external applications, degradation is evidenced by cracks and crazing. It may be protected by the use of various polymer stabilizers, including UV-absorbing additives and anti-oxidants such as phosphites (e.g. tris(2,4-di-tert-butylphenyl)phosphite) and hindered phenols, which prevent polymer degradation.

Microbial communities isolated from soil samples mixed with starch have been shown to be capable of degrading polypropylene. Polypropylene has been reported to degrade while in the human body as implantable mesh devices. The degraded material forms a tree bark-like layer at the surface of mesh fibers.

PP can be made translucent when uncolored but is not as readily made transparent as polystyrene, acrylic, or certain other plastics. It is often opaque or colored using pigments.

Polypropylene is produced by the chain-growth polymerization of propene:

The industrial production processes can be grouped into gas phase polymerization, bulk polymerization and slurry polymerization. All state-of-the-art processes use either gas-phase or bulk reactor systems.

In gas-phase and slurry-reactors, the polymer is formed around heterogeneous catalyst particles. The gas-phase polymerization is carried out in a fluidized bed reactor, propene is passed over a bed containing the heterogeneous (solid) catalyst and the formed polymer is separated as a fine powder and then converted into pellets. Unreacted gas is recycled and fed back into the reactor.

In bulk polymerization, liquid propene acts as a solvent to prevent the precipitation of the polymer. The polymerization proceeds at 60 to 80 °C and 30-40 atm are applied to keep the propene in the liquid state. For the bulk polymerization, typically loop reactors are applied. The bulk polymerization is limited to a maximum of 5% ethene as comonomer due to a limited solubility of the polymer in the liquid propene.

In the slurry polymerization, typically C4-C6 alkanes (butane, pentane or hexane) are utilized as inert diluent to suspend the growing polymer particles. Propene is introduced into the mixture as a gas.

The properties of PP are strongly affected by its tacticity, the orientation of the methyl groups () relative to the methyl groups in neighboring monomer units (see above). The tacticity of polypropylene can be chosen by the choice of an appropriate catalyst.

The properties of PP are strongly affected by its tacticity, the orientation of the methyl groups ( in the figure) relative to the methyl groups in neighboring monomer units. A Ziegler-Natta catalyst is able to restrict linking of monomer molecules to a specific orientation, either isotactic, when all methyl groups are positioned at the same side with respect to the backbone of the polymer chain, or syndiotactic, when the positions of the methyl groups alternate. Commercially available isotactic polypropylene is made with two types of Ziegler-Natta catalysts. The first group of the catalysts encompasses solid (mostly supported) catalysts and certain types of soluble metallocene catalysts. Such isotactic macromolecules coil into a helical shape; these helices then line up next to one another to form the crystals that give commercial isotactic polypropylene many of its desirable properties.

Another type of metallocene catalysts produce syndiotactic polypropylene. These macromolecules also coil into helices (of a different type) and crystallize. Atactic polypropylene is an amorphous rubbery material. It can be produced commercially either with a special type of supported Ziegler-Natta catalyst or with some metallocene catalysts.

Modern supported Ziegler-Natta catalysts developed for the polymerization of propylene and other 1-alkenes to isotactic polymers usually use as an active ingredient and as a support. The catalysts also contain organic modifiers, either aromatic acid esters and diesters or ethers. These catalysts are activated with special cocatalysts containing an organoaluminum compound such as Al(C ₂H ₅) ₃ and the second type of a modifier. The catalysts are differentiated depending on the procedure used for fashioning catalyst particles from MgCl ₂ and depending on the type of organic modifiers employed during catalyst preparation and use in polymerization reactions. Two most important technological characteristics of all the supported catalysts are high productivity and a high fraction of the crystalline isotactic polymer they produce at 70-80 °C under standard polymerization conditions. Commercial synthesis of isotactic polypropylene is usually carried out either in the medium of liquid propylene or in gas-phase reactors.

Commercial synthesis of syndiotactic polypropylene is carried out with the use of a special class of metallocene catalysts. They employ bridged bis-metallocene complexes of the type bridge-(Cp ₁)(Cp ₂)ZrCl ₂ where the first Cp ligand is the cyclopentadienyl group, the second Cp ligand is the fluorenyl group, and the bridge between the two Cp ligands is -CH ₂-CH ₂-, >SiMe ₂, or >SiPh ₂. These complexes are converted to polymerization catalysts by activating them with a special organoaluminum cocatalyst, methylaluminoxane (MAO).

Melting process of polypropylene can be achieved via extrusion and molding. Common extrusion methods include production of melt-blown and spun-bond fibers to form long rolls for future conversion into a wide range of useful products, such as face masks, filters, diapers and wipes.

The most common shaping technique is injection molding, which is used for parts such as cups, cutlery, vials, caps, containers, housewares, and automotive parts such as batteries. The related techniques of blow molding and injection-stretch blow molding are also used, which involve both extrusion and molding.

The large number of end-use applications for polypropylene are often possible because of the ability to tailor grades with specific molecular properties and additives during its manufacture. For example, antistatic additives can be added to help polypropylene surfaces resist dust and dirt. Many physical finishing techniques can also be used on polypropylene, such as machining. Surface treatments can be applied to polypropylene parts in order to promote adhesion of printing ink and paints.

Expanded Polypropylene (EPP) has been produced through both solid and melt state processing. EPP is manufactured using melt processing with either chemical or physical blowing agents. Expansion of PP in solid state, due to its highly crystalline structure, has not been successful. In this regard, two novel strategies were developed for expansion of PP. It was observed that PP can be expanded to make EPP through controlling its crystalline structure or through blending with other polymers.

Biaxially oriented polypropylene (BOPP)

When polypropylene film is extruded and stretched in both the machine direction and across machine direction it is called biaxially oriented polypropylene. Biaxial orientation increases strength and clarity. BOPP is widely used as a packaging material for packaging products such as snack foods, fresh produce and confectionery. It is easy to coat, print and laminate to give the required appearance and properties for use as a packaging material. This process is normally called converting. It is normally produced in large rolls which are slit on slitting machines into smaller rolls for use on packaging machines.

As polypropylene is resistant to fatigue, most plastic living hinges, such as those on flip-top bottles, are made from this material. However, it is important to ensure that chain molecules are oriented across the hinge to maximise strength.

Polypropylene is used in the manufacturing of piping systems, both ones concerned with high purity and ones designed for strength and rigidity (e.g., those intended for use in potable plumbing, hydronic heating and cooling, and reclaimed water). This material is often chosen for its resistance to corrosion and chemical leaching, its resilience against most forms of physical damage, including impact and freezing, its environmental benefits, and its ability to be joined by heat fusion rather than gluing.

Many plastic items for medical or laboratory use can be made from polypropylene because it can withstand the heat in an autoclave. Its heat resistance also enables it to be used as the manufacturing material of consumer-grade kettles. Food containers made from it will not melt in the dishwasher, and do not melt during industrial hot filling processes. For this reason, most plastic tubs for dairy products are polypropylene sealed with aluminum foil (both heat-resistant materials). After the product has cooled, the tubs are often given lids made of a less heat-resistant material, such as LDPE or polystyrene. Such containers provide a good hands-on example of the difference in modulus, since the rubbery (softer, more flexible) feeling of LDPE with respect to polypropylene of the same thickness is readily apparent. Rugged, translucent, reusable plastic containers made in a wide variety of shapes and sizes for consumers from various companies such as Rubbermaid and Sterilite are commonly made of polypropylene, although the lids are often made of somewhat more flexible LDPE so they can snap onto the container to close it. Polypropylene can also be made into disposable bottles to contain liquid, powdered, or similar consumer products, although HDPE and polyethylene terephthalate are commonly also used to make bottles. Plastic pails, car batteries, wastebaskets, pharmacy prescription bottles, cooler containers, dishes and pitchers are often made of polypropylene or HDPE, both of which commonly have rather similar appearance, feel, and properties at ambient temperature. A diversity of medical devices are made from PP.

A common application for polypropylene is as biaxially oriented polypropylene (BOPP). These BOPP sheets are used to make a wide variety of materials including clear bags. When polypropylene is biaxially oriented, it becomes crystal clear and serves as an excellent packaging material for artistic and retail products.

Polypropylene, highly colorfast, is widely used in manufacturing carpets, rugs and mats to be used at home.

Polypropylene is widely used in ropes, distinctive because they are light enough to float in water. For equal mass and construction, polypropylene rope is similar in strength to polyester rope. Polypropylene costs less than most other synthetic fibers.

Polypropylene is also used as an alternative to polyvinyl chloride (PVC) as insulation for electrical cables for LSZH cable in low-ventilation environments, primarily tunnels. This is because it emits less smoke and no toxic halogens, which may lead to production of acid in high-temperature conditions.

Polypropylene is also used in particular roofing membranes as the waterproofing top layer of single-ply systems as opposed to modified-bit systems.

Polypropylene is most commonly used for plastic moldings, wherein it is injected into a mold while molten, forming complex shapes at relatively low cost and high volume; examples include bottle tops, bottles, and fittings.

It can also be produced in sheet form, widely used for the production of stationery folders, packaging, and storage boxes. The wide color range, durability, low cost, and resistance to dirt make it ideal as a protective cover for papers and other materials. It is used in Rubik's Cube stickers because of these characteristics.

The availability of sheet polypropylene has provided an opportunity for the use of the material by designers. The light-weight, durable, and colorful plastic makes an ideal medium for the creation of light shades, and a number of designs have been developed using interlocking sections to create elaborate designs.

Polypropylene sheets are a popular choice for trading card collectors; these come with pockets (nine for standard-size cards) for the cards to be inserted and are used to protect their condition and are meant to be stored in a binder.

Expanded polypropylene (EPP) is a foam form of polypropylene. EPP has very good impact characteristics due to its low stiffness; this allows EPP to resume its shape after impacts. EPP is extensively used in model aircraft and other radio controlled vehicles by hobbyists. This is mainly due to its ability to absorb impacts, making this an ideal material for RC aircraft for beginners and amateurs.

Polypropylene is used in the manufacture of loudspeaker drive units. Its use was pioneered by engineers at the BBC and the patent rights subsequently purchased by Mission Electronics for use in their Mission Freedom Loudspeaker and Mission 737 Renaissance loudspeaker.

Polypropylene fibres are used as a concrete additive to increase strength and reduce cracking and spalling. In some areas susceptible to earthquakes (e.g., California), PP fibers are added with soils to improve the soil's strength and damping when constructing the foundation of structures such as buildings, bridges, etc.

Polypropylene fibres are also used in drywall joint compound for reinforcement. It can increase the flexibility and dimensional stability of the joint compound and reduce shrinkage and cracking when it dries.

Polypropylene is used in polypropylene drums.

In June 2016, a study showed that a mixture of polypropylene and durable superoleophobic surfaces created by two engineers from Ohio State University can repel liquids such as shampoo and oil. This technology could make it easier to remove all of the liquid contents from polypropylene bottles, particularly those that have high surface tension such as shampoo or oil.

Polypropylene is a major polymer used in nonwovens, with over 50% used for diapers or sanitary products where it is treated to absorb water (hydrophilic) rather than naturally repelling water (hydrophobic). Other non-woven uses include filters for air, gas, and liquids in which the fibers can be formed into sheets or webs that can be pleated to form cartridges or layers that filter in various efficiencies in the 0.5 to 30 micrometre range. Such applications occur in houses as water filters or in air-conditioning-type filters. The high surface-area and naturally oleophilic polypropylene nonwovens are ideal absorbers of oil spills with the familiar floating barriers near oil spills on rivers.

Polypropylene, or 'polypro', has been used for the fabrication of cold-weather base layers, such as long-sleeve shirts or long underwear. Polypropylene is also used in warm-weather clothing, in which it transports sweat away from the skin. Polyester has replaced polypropylene in these applications in the U.S. military, such as in the ECWCS. Although polypropylene clothes are not easily flammable, they can melt, which may result in severe burns if the wearer is involved in an explosion or fire of any kind. Polypropylene undergarments are known for retaining body odors which are then difficult to remove. The current generation of polyester does not have this disadvantage.

Some fashion designers have adapted polypropylene to construct jewelry and other wearable items.

Its most common medical use is in the synthetic, nonabsorbable suture Prolene, manufactured by Ethicon Inc.

Polypropylene has been used in hernia and pelvic organ prolapse repair operations to protect the body from new hernias in the same location. A small patch of the material is placed over the spot of the hernia, below the skin, and is painless and rarely, if ever, rejected by the body. However, a polypropylene mesh will erode the tissue surrounding it over the uncertain period from days to years.

A notable application was as a transvaginal mesh, used to treat vaginal prolapse and concurrent urinary incontinence. Due to the above-mentioned propensity for polypropylene mesh to erode the tissue surrounding it, the FDA has issued several warnings on the use of polypropylene mesh medical kits for certain applications in pelvic organ prolapse, specifically when introduced in close proximity to the vaginal wall due to a continued increase in number of mesh-driven tissue erosions reported by patients over the past few years. On 3 January 2012, the FDA ordered 35 manufacturers of these mesh products to study the side effects of these devices. Due to the outbreak of the COVID-19 pandemic in 2020, the demand for PP has increased significantly because it's a vital raw material for producing meltblown fabric, which is in turn the raw material for producing facial masks.

Very thin sheets (≈2-20 µm) of polypropylene are used as a dielectric within certain high-performance pulse and low-loss RF capacitors.

Expanded polypropylene (EPP) foam is a structural material in hobbyist radio control model aircraft. Unlike expanded polystyrene foam (EPS) which is friable and breaks easily on impact, EPP foam is able to absorb kinetic impacts very well without breaking, retains its original shape, and exhibits memory form characteristics which allow it to return to its original shape in a short amount of time.

When the cathedral on Tenerife, La Laguna Cathedral, was repaired in 2002-2014, it turned out that the vaults and dome were in a rather bad condition. Therefore, these parts of the building were demolished, and replaced by constructions in polypropylene. This was reported as the first time this material was used in this scale in buildings.

Under the trade name Ulstron polypropylene rope is used to manufacture scoop nets for whitebait. It has also been used for sheets of yacht sails.

Polymer banknotes are made from BOPP, where it provides a durable base and allows for the use of transparent security features by omitting opaque inks in the desired areas.

Polypropylene is recyclable and has the number "5" as its resin identification code:[63]

Many objects are made with polypropylene precisely because it is resilient and resistant to most solvents and glues. Also, there are very few glues available specifically for gluing PP. However, solid PP objects not subject to undue flexing can be satisfactorily joined with a two-part epoxy glue or using hot-glue guns. Preparation is important and it is often helpful to roughen the surface with a file, emery paper or other abrasive material to provide better anchorage for the glue. Also it is recommended to clean with mineral spirits or similar alcohol prior to gluing to remove any oils or other contamination. Some experimentation may be required. There are also some industrial glues available for PP, but these can be difficult to find, especially in a retail store.

PP can be melted using a speed tip welding technique. With speed welding, the plastic welder, similar to a soldering iron in appearance and wattage, is fitted with a feed tube for the plastic weld rod. The speed tip heats the rod and the substrate, while at the same time it presses the molten weld rod into position. A bead of softened plastic is laid into the joint, and the parts and weld rod fuse. With polypropylene, the melted welding rod must be "mixed" with the semi-melted base material being fabricated or repaired. A speed tip "gun" is essentially a soldering iron with a broad, flat tip that can be used to melt the weld joint and filler material to create a bond.

The advocacy organization Environmental Working Group classifies PP as of low to moderate hazard. PP is dope-dyed; no water is used in its dyeing, in contrast with cotton.

In 2020 researchers reported that polypropylene infant feeding bottles with contemporary preparation procedures were found to cause microplastics exposure to infants ranging from 14,600 to 4,550,000 particles per capita per day in 48 regions. Microplastics release is higher with warmer liquids and similar with other polypropylene products such as lunchboxes.

Like all organic compounds, polypropylene is combustible. The flash point of a typical composition is 260 °C; autoignition temperature is 388 °C.

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Polypropylene ( PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins and is partially crystalline and non-polar. Its properties are similar to polyethylene, but it is slightly harder and more heat resistant.

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The boiler will be much more stable in temperature than the thermoblock although it requires between 5 and 8 min of heating.
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The professional machines are generally equipped with a Boiler while automatic machines more often have a Thermoblock system.

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When you brew coffee and hot water pours through the grounds, the filter allows the rich flavor into your coffee pot or mug, while keeping the grounds separate. It's a morning ritual we barely think about, but I got to thinking about the wide variety of coffee filter types, and whether this plays an important role in determining the quality of coffee.

Does it affect the flavor? What are coffee filters made of, and does the material impact the taste? What about the different shapes and sizes?

Let's break down some interesting details about this simple yet vital component of a good brew.

How coffee filters work

The purpose of a coffee filter is fairly straightforward: after the hot water has dissolved the flavor compounds of the coffee beans, and absorbed their taste, color, and aroma, the filter separates this liquid from the grounds. This filter is often (but not always) made of disposable paper-thin and porous enough to allow liquid through, but not the tiny grains of coffee. Essentially, a filter traps the grounds and other particles that you don't want to drink. The filter you choose influences what gets into the coffee and what stays out.

What coffee filters are made of

Just as the type of coffee bean influences flavor, so does the filter material. The most common coffee filter types are paper, metal, and cloth.

Paper coffee filters

Paper coffee filters are one of the most commonly available filters. You can easily find them in any grocery store. They are used in drip coffee makers and are both highly absorbent and tightly woven, removing the majority of excess oils and grounds for a cleaner liquid. Without these particles, coffee may seem more acidic, but this is a matter of perception.

Paper coffee filters are typically available in a cone shape or a basket shape (above), and in different sizes for compatibility with your coffee maker. Melitta coffee filters, among other brands, are available in white, natural brown, and bamboo.

How to use a paper coffee filter

There are several ways to use a paper coffee filter, depending on the brewing method. Using a paper coffee filter with a coffee maker is the most universal method. These appliances are relatively affordable and found easily in many stores. After setting up the coffee maker, you fill up the water tank and insert the paper filter into the pull-out compartment. Then, measure out the desired amount of coffee and pour the grounds into the filter. Replace the compartment and turn on the coffee maker to brew.

Other methods use paper coffee filters as well, such as pour-over. This method requires a cone filter and a cone. You start by bringing the water to a boil separately. Place the paper filter inside the cone and saturate it with hot water. Place the cone on a pot or mug, measure the coffee grounds into the filter, and pour in the water, allowing water to extract compounds from the coffee grounds as it passes through and emerges into the pot or mug.

What kind of paper are coffee filters made of?

Coffee filters are typically made with paper that weights 100 grams per square meter. Melitta also offers bamboo-based paper filters. The type of paper impacts the brewing process, as the coffee filter pore size plays a role in what makes it through.

Why are some paper coffee filters brown and some white?

The filter's color depends on whether the paper is bleached (white) or unbleached (brown). While neither of these options will affect the quality of the coffee, unbleached filters are more environmentally friendly. Bleached coffee filters take paper away from its natural color, which is brown.

Metal coffee filters provide a different experience from paper filters. The mesh inevitably has larger pores, so it doesn't block as much of the natural oils or small grounds of coffee. Even the best metal coffee filter will allow some particles and residue through, but that's not necessarily a bad thing. The coffee filter pore size is still tiny, which makes the particles barely noticeable.

Many people find that this extra body, and the accompanying oils that get through, actually give you a much richer taste and fuller mouthfeel than you get with a paper filter. Certain flavors only present themselves when the oils are present, offering a sweetness that paper filters remove.

Metal coffee filters can be tricky to clean. When cleaning coffee filters, you should consider both daily upkeep and monthly deep cleaning. On a daily basis, old coffee grounds need to be tossed into the garbage or compost pile, and the filter needs to be washed with soap and water. If there are any grounds that get stuck in the filter holes, they should be wiped out or plucked out.

These daily washings are enough to prevent too much buildup, but a monthly deep cleaning session is needed to keep coffee fresh. You can do this a few ways:

Soak the filter in soap, water, citric acid, and hydrogen peroxide for four hours.

Boil the filter in white vinegar and water mixture (1:13) and allow it to soak overnight.

Clean the filter with a coffee filter cleaner (like Urnex Espresso Machine Cleaning Powder).

After this wash, make sure to thoroughly rinse and wash with soap and water as a final step.

Cloth coffee filters

The least common coffee filter material is cloth, although these filters have a lot of benefits. Like paper filters, cloth filters do a great job of capturing all the coffee grounds. However, as with a metal filter, you still get all the oils that contribute to the coffee's flavor. By brewing coffee with this material, you get a rich cup that contains no unsavory grains or particles.

While cloth can provide a good middle ground between paper and metal filters, upkeep is a chore. Between each brew, these filters need to be washed, but you shouldn't let them become too dry or too moist. Usually, cloth filters last for about 30 brews before the micro-grounds and oil start to permeate the taste of the coffee. However, they can be used for about 100 brews safely.

Coffee filter shapes

Just as the material plays a role, so can the shape of the coffee filter. Coffee filters are available in cone, basket, and disk shapes for different brewing styles.

Cone coffee filters

Cone filters are the best coffee filters for pour-over brewing methods. They come in different sizes, depending on the type of coffee maker used. While a size No. 1 fits the one-cup coffee makers, the size No. 6 filters are meant for 10-cup coffee makers. There are No. 2 and No. 4 sizes in between. Consult the instructions for your coffee maker to find out which one you need.

Basket coffee filters

Basket coffee filters are commonly made to fit nearly every model of basket coffee mater. The shape is much like a large cupcake wrapper, and it is likely the image that most people think of when coffee filters are mentioned. While their opening towards the top is wide, the bottom of this filter is flat and wide.

Cone vs. basket filter

You might be wondering if the taste of your coffee would change if you switched from a cone to a flat bottom coffee filter.

The answer, according to coffee scientists at the UC Davis Coffee Center, is yes!

They recently conducted a study on this very question. They partnered with Breville, a company that makes coffee makers and whose Precision Brewer can brew with either a cone or a basket filter. They tried it with both, and kept all other variables such as roast level, water temperature and flow rate exactly the same.

Participants in their study tasted the coffees and were able to tell the difference. They described different flavor notes depending on the shape of the filter.

The researchers are still trying to learn why this happens. They know that a change in filter shape changes how the water flows through the grounds and therefore how the coffee molecules are transferred into the water. They are investigating the details of that process.

Disk coffee filters

The disk filter is mostly used in AeroPress brewers, though they sometimes are used to replace filters for Fresh press machines. They are significantly smaller than the others on this list, and their sizing varies according to the coffee maker with which they are intended to be used.

Coffee filter sizes

It is important to choose a filter that serves the number of cups that you want to brew.

Cone filters are sized by numbers, depending on the amount of coffee each one is meant for. Most automatic coffee makers can brew four to six cups (No. 2), eight to 12 cups (No. 4), and 10 cups (No. 6) at a time. (Note that these are small, five-or-six ounce cups rather than the 12-ounce "Tall" cup you would get at Starbucks.) Two-cup non-electric makers can use the No. 2 cone filter. Anyone who wants to brew a single cup of coffee will need a size No. 1.

Basket coffee filters have a standard size, although anyone who wants to brew fewer than six cups of coffee will need to seek out junior-size basket filters.

Brand-specific coffee filters

Some brewing devices have their own dedicated filters, rather than using one of the universal options. These include Chemex, AeroPress, and Hario V60.

Chemex filters

Filters for Chemex have up to 30 per cent more weight than other brands, allowing them to remove the finest of particles like cloth filters can. However, these filters also remove oils and fats, using a cone shape to filter water through the grounds. They produce a very clear cup of coffee.

AeroPress filters

AeroPress coffee makers generally use the brand's paper filters, although a metal replacement is available and preferred by some. AeroPress paper filters are fully compostable and they are not designed for any other brewer.

Hario V60 filters

Hario V60 uses a standard cone shape with a single large hole at the bottom of the dripper. Their branded filters are made of natural pulp, and no chemicals are used to create them. While a trapezoid filter could be used in a pinch, the company states that "delicious coffee" can only be made with their filter.

Coffee filter substitutes

Waking up to grind your coffee only to find that there are no filters can throw off an entire morning. Fortunately, there are a variety of household items that can act as a coffee filter substitute.

Paper towel coffee filter

Perhaps the most accessible and direct alternative is to grab a paper towel or napkin and fold it into your coffee maker to cover the space the filter would have.

Toilet paper coffee filter

Toilet paper can work this way as well and may shape to fit more easily into the coffee maker. However, be careful dumping the coffee grounds as this filter substitute can fall apart and make a mess.

Spare cloth

For a reusable coffee filter substitute, try using a scrap of cloth in your coffee maker. Muslin or fine grain cheesecloth provide a dense enough material to trap the grounds while allowing full flavor coffee to seep through, but other tightly woven cloth will do.

Sock coffee filter

In a real pinch, people have been known to use a (clean!) sock. Environmentally friendly and portable, you can skip the coffee maker and simply put the grounds inside the sock, holding the sock over a pot or mug, and pour hot water directly through the sock.

Cloth options can all be washed and reused, so you'll always have a backup on hand.

Coffee filter FAQ

Do coffee filters affect taste?

Coffee filters do affect the taste of coffee, but not in a way that will be obvious to everyone. The quality and shape of the filter both play a role in flavor. Anyone who is particular about taste should prioritize the quality of filter over a low price.

Do coffee filters go bad?

Filters generally don't come with an expiry date. If you've had filters sitting for a long time and want to use them up, there are several ways to ensure they don't go to waste. Try using them as disposable snack bowls for pretzels, popcorn, etc. Filters carry no lint so they make excellent screen cleaners for phones and computers. And you can use them to remove sediment when you pour the last of the wine.

Can you reuse coffee filters?

Most coffee filters can be used several times before they stop giving you the quality of coffee you want. Just rinse them immediately after use and leave them to dry. If you want to replace your coffee filter less often, buy a metal filter that can be used for years.

Can you compost a coffee filter?

Yes. Both the coffee filter and its used coffee grounds can be put in the compost pile. Decomposition happens relatively fast, especially if the filter is buried rather than kept near the top where it can dry out.

Will paper towel work as a coffee filter?

You can use a paper towel as a coffee filter in a pinch. Measure two tablespoons of coffee into the paper towel and slowly pour hot (but not boiling) water over the grounds, allowing the liquid to strain into a cup.

Will coffee filters filter water?

Yes. If the water is particularly dirty, the filter will eventually become clogged and water will have a hard time passing through. That's when it's time to change to a new filter. Even after filtering, water should be boiled before consuming to kill pathogens such as bacteria and viruses.

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Coffee Filter Types, Shapes and Sizes You Should Know

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When you brew coffee and hot water pours through the grounds, the filter allows the rich flavor into your coffee pot or mug, while keeping the grounds separate. It's a morning ritual we barely think about, but I got to thinking about the wide variety of coffee filter types, and whether this plays an important role in determining the quality of coffee.

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Cloth coffee filters are a good middle ground flavor-wise between paper and cloth, but they're difficult to maintain.

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I did some research, took some advice from the internet, and settled on a box of Chemex filters from Austin, Texas-based CoffeeSock. Currently, a pack of two is $13.

This March, after I ran out of Hario V60 paper filters, I bought a box of CoffeeSock's cloth V60 filters (also $13).

(If you're in the UK or Europe, CoffeeSock will ship to you, or you can try a more local option like these from Earthtopia -of course I can't vouch for them, but hey it's an option.)

So, I've had six plus months of using cloth Chemex filters, and a couple of months using their V60 counterparts. What are they like? Are they better than paper?

Note: this is all my personal rambling opinion-"better" is a meaningless word here, exactly zero scientific rigor or actual quantifiable research was used, and I paid for everything myself.

Just wanted to get that out of the way.

The brewing experience-Chemex

First things first: CoffeeSock recommends boiling your new filter for ten minutes in fresh water to sanitize and pre-shrink. Best not skip this step.

Now, let's consider the filter itself: CoffeeSock's offerings are made of Certified Organic cotton (cotton, it should be noted, isn't without its environmental problems- even the organic kind). They're made in Austin, Texas, and come in a nice plastic-free box that includes lots of handy info about brewing and cleaning and whatnot.

The Chemex brewer is famous for (among other things) the coffee it produces: light, clean, with a delicate body. This can put people off- thin is the criticism I've heard leveled most at the Chemex brew-but in general it's a very popular brew method.

It's also beautiful, and is even in the Museum of Modern Art's permanent collection.

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Cloth coffee filters: are they worth it? - The Pourover

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Short answer: yes, I believe so. Long answer: well, read the article.

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Metal coffee filters brew coffee on the complete opposite end of the spectrum compared to paper coffee filters. Since there’s no finely weaved paper to absorb the natural oils or catch the microscopic grounds, some of these things end up in your final mug.

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.The filter shape that likely comes into your head when someone mentions a “coffee filter” is the basket filter. Also called the cupcake or-flat bottom filter, these filters are either shaped like cupcake liners with folds around the sides or like buckets with smooth edges.

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Cloud based control through wifi or bluetooth or App

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Cloud based control through wifi or bluetooth or App

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When you are returning to your home tired and want a hot cup of coffee already waiting for you at home then this technology is for you.
Just open the app and give the commands in app.
That's it

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A wireless network interface controller ( WNIC) is a network interface controller which connects to a wireless network, such as Wi-Fi or Bluetooth, rather than a wired network, such as a Token Ring or Ethernet. A WNIC, just like other NICs, works on the layers 1 and 2 of the OSI model and uses an antenna to communicate via radio waves.

Early wireless network interface controllers were commonly implemented on expansion cards connected using the PCI bus and PCIe bus or via USB, PC Card, ExpressCard, Mini PCIe or M.2.

The low cost and ubiquity of the Wi-Fi standard means that many newer mobile computers have a wireless network interface built into the motherboard.

The term is usually applied to IEEE 802.11 adapters; it may also apply to a NIC using protocols other than 802.11, such as one implementing Bluetooth connections.

An 802.11 WNIC can operate in two modes known as infrastructure mode and :

Infrastructure mode

In an infrastructure mode network the WNIC needs a wireless access point: all data is transferred using the access point as the central hub. All wireless nodes in an infrastructure mode network connect to an access point. All nodes connecting to the access point must have the same service set identifier (SSID) as the access point, and if a kind of wireless security is enabled on the access point (such as WEP or WPA), they must share the same keys or other authentication parameters.

Ad hoc mode

In an ad hoc mode network the WNIC does not require an access point, but rather can interface with all other wireless nodes directly. All the nodes in an ad hoc network must have the same channel and SSID.

The IEEE 802.11 standard sets out low-level specifications for how all 802.11 wireless networks operate. Earlier 802.11 interface controllers are usually only compatible with earlier variants of the standard, while newer cards support both current and old standards.

Specifications commonly used in marketing materials for WNICs include:

Wireless data transfer rates (measured in Mbit/s); these range from 2 Mbit/s to 54 Mbit/s.

Wireless transmit power (measured in dBm)

Wireless network standards (may include standards such as 802.11b, 802.11g, 802.11n, etc.) 802.11g offers data transfer speeds equivalent to 802.11a - up to 54 Mbit/s - and the wider 300-foot (91 m) range of 802.11b, and is backward compatible with 802.11b.

Most Bluetooth cards do not implement any form of the 802.11 standard.

Wireless range may be substantially affected by objects in the way of the signal and by the quality of the antenna. Large electrical appliances, such as refrigerators, fuse boxes, metal plumbing, and air conditioning units can impede a wireless network signal. The theoretical maximum range of IEEE 802.11 is only reached under ideal circumstances and true effective range is typically about half of the theoretical range. Specifically, the maximum throughput speed is only achieved at extremely close range (less than 25 feet (7.6 m) or so); at the outer reaches of a device's effective range, speed may decrease to around 1 Mbit/s before it drops out altogether. The reason is that wireless devices dynamically negotiate the top speed at which they can communicate without dropping too many data packets.

FullMAC and SoftMAC devices

In an 802.11 WNIC, the MAC Sublayer Management Entity (MLME) can be implemented either in the NIC's hardware or firmware, or in host-based software that is executed on the main CPU. A WNIC that implements the MLME function in hardware or firmware is called a FullMAC WNIC or a HardMAC NIC and a NIC that implements it in host software is called a SoftMAC NIC.

A FullMAC device hides the complexity of the 802.11 protocol from the main CPU, instead providing an 802.3 (Ethernet) interface; a SoftMAC design implements only the timing-critical part of the protocol in hardware/firmware and the rest on the host.

FullMAC chips are typically used in mobile devices because:

they are easier to integrate in complete products

power is saved by having a specialized CPU perform the 802.11 processing;

the chip vendor has tighter control of the MLME.

Popular example of FullMAC chips is the one implemented on the Raspberry Pi 3.

Linux kernel's mac80211 framework provides capabilities for SoftMAC devices and additional capabilities (such as mesh networking, which is known as the IEEE 802.11s standard) for devices with limited functionality.

FreeBSD also supports SoftMAC drivers.

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A wireless network interface controller ( WNIC) is a network interface controller which connects to a wireless network, such as Wi-Fi or Bluetooth, rather than a wired network, such as a Token Ring or Ethernet. A WNIC, just like other NICs, works on the layers 1 and 2 of the OSI model and uses an antenna to communicate via radio waves.

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It is simplest way to control a machine just give a command "Hello machine make a cup of coffee for me" then the machine will give you different options for varieties of coffee and you just have to select on of it.
It is like speaking with a person.

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A voice-user interface ( VUI) makes spoken human interaction with computers possible, using speech recognition to understand spoken commands and answer questions, and typically text to speech to play a reply. A voice command device ( VCD) is a device controlled with a voice user interface.

Voice user interfaces have been added to automobiles, home automation systems, computer operating systems, home appliances like washing machines and microwave ovens, and television remote controls. They are the primary way of interacting with virtual assistants on smartphones and smart speakers. Older automated attendants (which route phone calls to the correct extension) and interactive voice response systems (which conduct more complicated transactions over the phone) can respond to the pressing of keypad buttons via DTMF tones, but those with a full voice user interface allow callers to speak requests and responses without having to press any buttons.

Newer VCDs are speaker-independent, so they can respond to multiple voices, regardless of accent or dialectal influences. They are also capable of responding to several commands at once, separating vocal messages, and providing appropriate feedback, accurately imitating a natural conversation.

A VUI is the interface to any speech application. Controlling a machine by simply talking to it was science fiction only a short time ago. Until recently, this area was considered to be artificial intelligence. However, advances in technologies like text-to-speech, speech-to-text, Natural Language Processing, and cloud services, in general, contributed to the mass adoption of these types of interfaces. VUIs have become more commonplace, and people are taking advantage of the value that these hands-free, eyes-free interfaces provided in many situations.

VUIs need to respond to input reliably, or they will be rejected and often ridiculed by their users. Designing a good VUI requires interdisciplinary talents of computer science, linguistics and human factors psychology - all of which are skills that are expensive and hard to come by. Even with advanced development tools, constructing an effective VUI requires an in-depth understanding of both the tasks to be performed, as well as the target audience that will use the final system. The closer the VUI matches the user's mental model of the task, the easier it will be to use with little or no training, resulting in both higher efficiency and higher user satisfaction.

A VUI designed for the general public should emphasize ease of use and provide a lot of help and guidance for first-time callers. In contrast, a VUI designed for a small group of power users (including field service workers), should focus more on productivity and less on help and guidance. Such applications should streamline the call flows, minimize prompts, eliminate unnecessary iterations and allow elaborate "mixed initiative dialogs", which enable callers to enter several pieces of information in a single utterance and in any order or combination. In short, speech applications have to be carefully crafted for the specific business process that is being automated.

Not all business processes render themselves equally well for speech automation. In general, the more complex the inquiries and transactions are, the more challenging they will be to automate, and the more likely they will be to fail with the general public. In some scenarios, automation is simply not applicable, so live agent assistance is the only option. A legal advice hotline, for example, would be very difficult to automate. On the flip side, speech is perfect for handling quick and routine transactions, like changing the status of a work order, completing a time or expense entry, or transferring funds between accounts.

Early applications for VUI included voice-activated dialing of phones, either directly or through a (typically Bluetooth) headset or vehicle audio system.

In 2007, a CNN business article reported that voice command was over a billion dollar industry and that companies like Google and Apple were trying to create speech recognition features. It has been years since the article was published, and since then the world has witnessed a variety of voice command devices. In addition, Google created a speech recognition engine called Pico TTS and Apple has released Siri. Voice command devices are becoming more widely available, and innovative ways for using the human voice are always being created. For example, Business Week suggests that the future remote controller is going to be the human voice. Currently Xbox Live allows such features and Jobs hinted at such a feature on the new Apple TV.

Both Apple Mac and Windows PC provide built in speech recognition features for their latest operating systems.

Two Microsoft operating systems, Windows 7 and Windows Vista, provide speech recognition capabilities. Microsoft integrated voice commands into their operating systems to provide a mechanism for people who want to limit their use of the mouse and keyboard, but still want to maintain or increase their overall productivity.

Windows Vista

With Windows Vista voice control, a user may dictate documents and emails in mainstream applications, start and switch between applications, control the operating system, format documents, save documents, edit files, efficiently correct errors, and fill out forms on the Web. The speech recognition software learns automatically every time a user uses it, and speech recognition is available in English (U.S.), English (U.K.), German (Germany), French (France), Spanish (Spain), Japanese, Chinese (Traditional), and Chinese (Simplified). In addition, the software comes with an interactive tutorial, which can be used to train both the user and the speech recognition engine.

In addition to all the features provided in Windows Vista, Windows 7 provides a wizard for setting up the microphone and a tutorial on how to use the feature.

All Mac OS X computers come pre-installed with the speech recognition software. The software is user-independent, and it allows for a user to, "navigate menus and enter keyboard shortcuts; speak checkbox names, radio button names, list items, and button names; and open, close, control, and switch among applications." However, the Apple website recommends a user buy a commercial product called Dictate.

If a user is not satisfied with the built in speech recognition software or a user does not have a built speech recognition software for their OS, then a user may experiment with a commercial product such as Braina Pro or DragonNaturallySpeaking for Windows PCs, and Dictate, the name of the same software for Mac OS.

Any mobile device running Android OS, Microsoft Windows Phone, iOS 9 or later, or Blackberry OS provides voice command capabilities. In addition to the built speech recognition software for each mobile phone's operating system, a user may download third party voice command applications from each operating system's application store: Apple App store, Google Play, Windows Phone Marketplace (initially Windows Marketplace for Mobile), or BlackBerry App World.

Google has developed an open source operating system called Android, which allows a user to perform voice commands such as: send text messages, listen to music, get directions, call businesses, call contacts, send email, view a map, go to websites, write a note, and search Google. The speech recognition software is available for all devices since Android 2.2 "Froyo", but the settings must be set to English. Google allows for the user to change the language, and the user is prompted when he or she first uses the speech recognition feature if he or she would like their voice data to be attached to their Google account. If a user decides to opt into this service, it allows Google to train the software to the user's voice.

Google introduced the Google Assistant with Android 7.0 "Nougat". It is much more advanced than the older version.

Amazon.com has the Echo that uses Amazon's custom version of Android to provide a voice interface.

Windows Phone is Microsoft's mobile device's operating system. On Windows Phone 7.5, the speech app is user independent and can be used to: call someone from your contact list, call any phone number, redial the last number, send a text message, call your voice mail, open an application, read appointments, query phone status, and search the web. In addition, speech can also be used during a phone call, and the following actions are possible during a phone call: press a number, turn the speaker phone on, or call someone, which puts the current call on hold.

Windows 10 introduces Cortana, a voice control system that replaces the formerly used voice control on Windows phones.

Apple added Voice Control to its family of iOS devices as a new feature of iPhone OS 3. The iPhone 4S, iPad 3, iPad Mini 1G, iPad Air, iPad Pro 1G, iPod Touch 5G and later, all come with a more advanced voice assistant called Siri. Voice Control can still be enabled through the Settings menu of newer devices. Siri is a user independent built-in speech recognition feature that allows a user to issue voice commands. With the assistance of Siri a user may issue commands like, send a text message, check the weather, set a reminder, find information, schedule meetings, send an email, find a contact, set an alarm, get directions, track your stocks, set a timer, and ask for examples of sample voice command queries. In addition, Siri works with Bluetooth and wired headphones.

In 2014 Amazon introduced the Alexa smart home device. Its main purpose was just a smart speaker, that allowed the consumer to control the device with their voice. Eventually, it turned into a novelty device that had the ability to control home appliance with voice. Now almost all the appliances are controllable with Alexa, including light bulbs and temperature. By allowing voice control Alexa can connect to smart home technology allowing you to lock your house, control the temperature, and activate various devices. This form of A.I allows for someone to simply ask it a question, and in response the Alexa searches for, finds, and recites the answer back to you.

As car technology improves, more features will be added to cars and these features will most likely distract a driver. Voice commands for cars, according to CNET, should allow a driver to issue commands and not be distracted. CNET stated that Nuance was suggesting that in the future they would create a software that resembled Siri, but for cars. Most speech recognition software on the market in 2011 had only about 50 to 60 voice commands, but Ford Sync had 10,000. However, CNET suggested that even 10,000 voice commands was not sufficient given the complexity and the variety of tasks a user may want to do while driving. Voice command for cars is different from voice command for mobile phones and for computers because a driver may use the feature to look for nearby restaurants, look for gas, driving directions, road conditions, and the location of the nearest hotel. Currently, technology allows a driver to issue voice commands on both a portable GPS like a Garmin and a car manufacturer navigation system.

List of Voice Command Systems Provided By Motor Manufacturers:

While most voice user interfaces are designed to support interaction through spoken human language, there have also been recent explorations in designing interfaces take non-verbal human sounds as input. In these systems, the user controls the interface by emitting non-speech sounds such as humming, whistling, or blowing into a microphone.

One such example of a non-verbal voice user interface is Blendie, an interactive art installation created by Kelly Dobson. The piece comprised a classic 1950s-era blender which was retrofitted to respond to microphone input. To control the blender, the user must mimic the whirring mechanical sounds that a blender typically makes: the blender will spin slowly in response to a user's low-pitched growl, and increase in speed as the user makes higher-pitched vocal sounds.

Another example is VoiceDraw, a research system that enables digital drawing for individuals with limited motor abilities. VoiceDraw allows users to "paint" strokes on a digital canvas by modulating vowel sounds, which are mapped to brush directions. Modulating other paralinguistic features (e.g. the loudness of their voice) allows the user to control different features of the drawing, such as the thickness of the brush stroke.

Other approaches include adopting non-verbal sounds to augment touch-based interfaces (e.g. on a mobile phone) to support new types of gestures that wouldn't be possible with finger input alone.

Voice interfaces pose a substantial number of challenges for usability. In contrast to graphical user interfaces (GUIs), best practices for voice interface design are still emergent.

With purely audio-based interaction, voice user interfaces tend to suffer from low discoverability: it is difficult for users to understand the scope of a system's capabilities. In order for the system to convey what is possible without a visual display, it would need to enumerate the available options, which can become tedious or infeasible. Low discoverability often results in users reporting confusion over what they are "allowed" to say, or a mismatch in expectations about the breadth of a system's understanding.

While speech recognition technology has improved considerably in recent years, voice user interfaces still suffer from parsing or transcription errors in which a user's speech is not interpreted correctly. These errors tend to be especially prevalent when the speech content uses technical vocabulary (e.g. medical terminology) or unconventional spellings such as musical artist or song names.

Effective system design to maximize conversational understanding remains an open area of research. Voice user interfaces that interpret and manage conversational state are challenging to design due to the inherent difficulty of integrating complex natural language processing tasks like coreference resolution, named-entity recognition, information retrieval, and dialog management. Most voice assistants today are capable of executing single commands very well but limited in their ability to manage dialogue beyond a narrow task or a couple turns in a conversation.

Pocket-size devices, such as PDAs or mobile phones, currently rely on small buttons for user input. These are either built into the device or are part of a touch-screen interface, such as that of the Apple iPod Touch and iPhone Siri Application. Extensive button-pressing on devices with such small buttons can be tedious and inaccurate, so an easy-to-use, accurate, and reliable VUI would potentially be a major breakthrough in the ease of their use. Nonetheless, such a VUI would also benefit users of laptop- and desktop-sized computers, as well, as it would solve numerous problems currently associated with keyboard and mouse use, including repetitive-strain injuries such as carpal tunnel syndrome and slow typing speed on the part of inexperienced keyboard users. Moreover, keyboard use typically entails either sitting or standing stationary in front of the connected display; by contrast, a VUI would free the user to be far more mobile, as speech input eliminates the need to look at a keyboard.

Such developments could literally change the face of current machines and have far-reaching implications on how users interact with them. Hand-held devices would be designed with larger, easier-to-view screens, as no keyboard would be required. Touch-screen devices would no longer need to split the display between content and an on-screen keyboard, thus providing full-screen viewing of the content. Laptop computers could essentially be cut in half in terms of size, as the keyboard half would be eliminated and all internal components would be integrated behind the display, effectively resulting in a simple tablet computer. Desktop computers would consist of a CPU and screen, saving desktop space otherwise occupied by the keyboard and eliminating sliding keyboard rests built under the desk's surface. Television remote controls and keypads on dozens of other devices, from microwave ovens to photocopiers, could also be eliminated.

Numerous challenges would have to be overcome, however, for such developments to occur. First, the VUI would have to be sophisticated enough to distinguish between input, such as commands, and background conversation; otherwise, false input would be registered and the connected device would behave erratically. A standard prompt, such as the famous "Computer!" call by characters in science fiction TV shows and films such as Star Trek, could activate the VUI and prepare it to receive further input by the same speaker. Conceivably, the VUI could also include a human-like representation: a voice or even an on-screen character, for instance, that responds back (e.g., "Yes, Vamshi?") and continues to communicate back and forth with the user in order to clarify the input received and ensure accuracy.

Second, the VUI would have to work in concert with highly sophisticated software in order to accurately process and find/retrieve information or carry out an action as per the particular user's preferences. For instance, if Samantha prefers information from a particular newspaper, and if she prefers that the information be summarized in point-form, she might say, "Computer, find me some information about the flooding in southern China last night"; in response, the VUI that is familiar with her preferences would "find" facts about "flooding" in "southern China" from that source, convert it into point-form, and deliver it to her on screen and/or in voice form, complete with a citation. Therefore, accurate speech-recognition software, along with some degree of artificial intelligence on the part of the machine associated with the VUI, would be required.

Privacy concerns are raised by the fact that voice commands are available to the providers of voice-user interfaces in unencrypted form, and can thus be shared with third parties and be processed in an unauthorized or unexpected manner. Additionally to the linguistic content of recorded speech, a user's manner of expression and voice characteristics can implicitly contain information about his or her biometric identity, personality traits, body shape, physical and mental health condition, sex, gender, moods and emotions, socioeconomic status and geographical origin.

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A voice-user interface ( VUI) makes spoken human interaction with computers possible, using speech recognition to understand spoken commands and answer questions, and typically text to speech to play a reply. A voice command device ( VCD) is a device controlled with a voice user interface.

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More robust and traditional way of interface. it also reduces cost of production.

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Introduction: LCD and Keypad Interface

Introduction

In this tutorial am going to show you how to interface a liquid crystal display and a keypad with Intel Galileo. we will use a 16x2 LCD,which displays 2 rows or character in 16 columns.

Add Tip Ask Question Download

Step 1: Components;

Components;

1. Intel Galileo.

2. 4x4 matrix keypad.

3. 16x2 Liquid Crystal Display (LCD).

4. Potentiometer.

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Step 2: Setup;

-connect pin 1-VSS of the LCD to ground and also end of the

potentiometer to ground.

-connect pin 2-VDD of the LCD to power, to provide power for the LCD.

-connect pin 3-VEE of the LCD to the variable terminal of the potentiometer. This pin is used to adjust the contrast of the LCD.

-connect pin 4-RS of the LCD to pin 12 of Galileo.

-connect pin 5-RW of the LCD to ground.

-connect pin 6-E of the LCD to pin 11 of Galileo.

-connect pin 11-D4 of the LCD to pin 5 of Galileo.

-connect pin 12-D5 of the LCD to pin 4 of Galileo.

-connect pin 13-D6 of the LCD to pin 3 of Galileo.

-connect pin 14-D7 of the LCD to pin 2 of Galileo.

-connect pin 13 of Galileo to pin 1 of the keypad.

-connect pin 10 of Galileo to pin 2 of the keypad.

-connect pin 9 of Galileo to pin 3 of the keypad.

-connect pin 8 of Galileo to pin 4 of the keypad.

-connect pin 7 of Galileo to pin 5 of the keypad.

-connect pin 6 of Galileo to pin 6 of the keypad.

-connect pin 1 of Galileo to pin 7 of the keypad.

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Step 3: Working;

When the project is switched on, power is fed to the LCD and

the back light goes on. When the keypad is pressed contact is made between two terminals to represent a character. Each character is represented by a combination of contact between two terminals. The character pressed on the keypad is read by the pins of the Galileo. The Galileo sets a position on the LCD as specified in the program where the Character is to be printed. It then sends the character to the LCD and it is printed on the set position. This whole process prints the specific character pressed on the key pad on to the LCD

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Step 4: Code;

#include<LiquidCrystal.h>

#include<Keypad.h>
#include<wire.h>
const byte rows=4;
const byte cols=3;
char keys[rows][cols]={
{'1','2','3'},
{'4','5','6'},
{'7','8','9'},
{'*','0','#'}
};
byte rowPins[rows]={13,10,9,8};
byte colPins[cols]={7,6,1};
Keypad keypad=Keypad(makeKeymap(keys),rowPins,colPins,rows,cols);
LiquidCrystal Lcd(12,11,5,4,3,2);
void setup() {
Lcd.begin(16,2);
Lcd.setCursor(1,0);
Lcd.print("Press a number");
// put your setup code here, to run once:
}
void loop() {
char key=keypad.getKey();
if(int(key)!=0)
{
Lcd.setCursor(5,1);
Lcd.print(key);
}
}

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# data[].attributes.attachment_link.description
Introduction In this tutorial am going to show you how to interface a liquid crystal display and a keypad with Intel Galileo. we will use a 16x2 LCD,which displays 2 rows or character in 16 columns. Add Tip Ask Question Download Components; 1. Intel Galileo. 2. 4x4 matrix keypad. 3.

# data[].attributes.body
A canister coffee mill with an integrated mill and storage container. The bottom has a silicone cover to prevent slipping for easier grinding. The burrs are ceramic, meaning they won’t damage your coffee beans with heat caused by friction as you grind them.
It can grind around 120g of coffee in one go.

# data[].attributes.body
This is as the name would suggest a  blade grinder that uses two stainless steel cutting blades to chop up the beans. Now although not the quality of a burr grinder, it is nonetheless, a grinder that will be able to do a decent job for most people. It can grind around 75 grams of coffee beans, and that will be enough to make around 15 cups of coffee in a single run. The simple rule with these types of grinders is that the longer you grind the beans, then the finer the grind will become.

# data[].attributes.body
Its easy to use a machine when we have touch screen interface. Use of pictorials makes it more easy.

# data[].attributes.attachment_link.readable_text
A , or touch screen, is both an input and output device and normally layered on the top of an electronic visual display of an information processing system. The display is often an LCD or OLED display while the system is usually a laptop, tablet, or smartphone. A user can give input or control the information processing system through simple or multi-touch gestures by touching the screen with a special stylus or one or more fingers. Some touchscreens use ordinary or specially coated gloves to work while others may only work using a special stylus or pen. The user can use the touchscreen to react to what is displayed and, if the software allows, to control how it is displayed; for example, zooming to increase the text size.

The touchscreen enables the user to interact directly with what is displayed, rather than using a mouse, touchpad, or other such devices (other than a stylus, which is optional for most modern touchscreens).

Touchscreens are common in devices such as game consoles, personal computers, electronic voting machines, and point-of-sale (POS) systems. They can also be attached to computers or, as terminals, to networks. They play a prominent role in the design of digital appliances such as personal digital assistants (PDAs) and some e-readers. Touchscreens are also important in educational settings such as classrooms or on college campuses.

The popularity of smartphones, tablets, and many types of information appliances is driving the demand and acceptance of common touchscreens for portable and functional electronics. Touchscreens are found in the medical field, heavy industry, automated teller machines (ATMs), and kiosks such as museum displays or room automation, where keyboard and mouse systems do not allow a suitably intuitive, rapid, or accurate interaction by the user with the display's content.

Historically, the touchscreen sensor and its accompanying controller-based firmware have been made available by a wide array of after-market system integrators, and not by display, chip, or motherboard manufacturers. Display manufacturers and chip manufacturers have acknowledged the trend toward acceptance of touchscreens as a user interface component and have begun to integrate touchscreens into the fundamental design of their products.

Eric Johnson, of the Royal Radar Establishment, located in Malvern, England, described his work on capacitive touchscreens in a short article published in 1965 and then more fully-with photographs and diagrams-in an article published in 1967. The application of touch technology for air traffic control was described in an article published in 1968. Frank Beck and Bent Stumpe, engineers from CERN (European Organization for Nuclear Research), developed a transparent touchscreen in the early 1970s, based on Stumpe's work at a television factory in the early 1960s. Then manufactured by CERN, and shortly after by industry partners, it was put to use in 1973. In 1977, an American company, Elographics - in partnership with Siemens - began work on developing a transparent implementation of an existing opaque touchpad technology, US patent No. 3,911,215, October 7, 1975, which had been developed by Elographics' founder George Samuel Hurst. The resulting resistive technology touch screen was first shown in 1982.

In 1972, a group at the University of Illinois filed for a patent on an optical touchscreen that became a standard part of the Magnavox Plato IV Student Terminal and thousands were built for this purpose. These touchscreens had a crossed array of 16×16 infrared position sensors, each composed of an LED on one edge of the screen and a matched phototransistor on the other edge, all mounted in front of a monochrome plasma display panel. This arrangement could sense any fingertip-sized opaque object in close proximity to the screen. A similar touchscreen was used on the HP-150 starting in 1983. The HP 150 was one of the world's earliest commercial touchscreen computers. HP mounted their infrared transmitters and receivers around the bezel of a 9-inch Sony cathode ray tube (CRT).

In 1984, Fujitsu released a touch pad for the Micro 16 to accommodate the complexity of kanji characters, which were stored as tiled graphics. In 1985, Sega released the Terebi Oekaki, also known as the Sega Graphic Board, for the SG-1000 video game console and SC-3000 home computer. It consisted of a plastic pen and a plastic board with a transparent window where pen presses are detected. It was used primarily with a drawing software application. A graphic touch tablet was released for the Sega AI computer in 1986.

Touch-sensitive control-display units (CDUs) were evaluated for commercial aircraft flight decks in the early 1980s. Initial research showed that a touch interface would reduce pilot workload as the crew could then select waypoints, functions and actions, rather than be "head down" typing latitudes, longitudes, and waypoint codes on a keyboard. An effective integration of this technology was aimed at helping flight crews maintain a high level of situational awareness of all major aspects of the vehicle operations including the flight path, the functioning of various aircraft systems, and moment-to-moment human interactions.

In the early 1980s, General Motors tasked its Delco Electronics division with a project aimed at replacing an automobile's non-essential functions (i.e. other than throttle, transmission, braking, and steering) from mechanical or electro-mechanical systems with solid state alternatives wherever possible. The finished device was dubbed the ECC for "Electronic Control Center", a digital computer and software control system hardwired to various peripheral sensors, servos, solenoids, antenna and a monochrome CRT touchscreen that functioned both as display and sole method of input. The ECC replaced the traditional mechanical stereo, fan, heater and air conditioner controls and displays, and was capable of providing very detailed and specific information about the vehicle's cumulative and current operating status in real time. The ECC was standard equipment on the 1985-1989 Buick Riviera and later the 1988-1989 Buick Reatta, but was unpopular with consumers-partly due to the technophobia of some traditional Buick customers, but mostly because of costly technical problems suffered by the ECC's touchscreen which would render climate control or stereo operation impossible.

Multi-touch technology began in 1982, when the University of Toronto's Input Research Group developed the first human-input multi-touch system, using a frosted-glass panel with a camera placed behind the glass. In 1985, the University of Toronto group, including Bill Buxton, developed a multi-touch tablet that used capacitance rather than bulky camera-based optical sensing systems (see History of multi-touch).

The first commercially available graphical point-of-sale (POS) software was demonstrated on the 16-bit Atari 520ST color computer. It featured a color touchscreen widget-driven interface. The ViewTouch POS software was first shown by its developer, Gene Mosher, at the Atari Computer demonstration area of the Fall COMDEX expo in 1986.

In 1987, Casio launched the Casio PB-1000 pocket computer with a touchscreen consisting of a 4×4 matrix, resulting in 16 touch areas in its small LCD graphic screen.

Touchscreens had a bad reputation of being imprecise until 1988. Most user-interface books would state that touchscreen selections were limited to targets larger than the average finger. At the time, selections were done in such a way that a target was selected as soon as the finger came over it, and the corresponding action was performed immediately. Errors were common, due to parallax or calibration problems, leading to user frustration. "Lift-off strategy" was introduced by researchers at the University of Maryland Human-Computer Interaction Lab (HCIL). As users touch the screen, feedback is provided as to what will be selected: users can adjust the position of the finger, and the action takes place only when the finger is lifted off the screen. This allowed the selection of small targets, down to a single pixel on a 640×480 Video Graphics Array (VGA) screen (a standard of that time).

Sears et al. (1990) gave a review of academic research on single and multi-touch human-computer interaction of the time, describing gestures such as rotating knobs, adjusting sliders, and swiping the screen to activate a switch (or a U-shaped gesture for a toggle switch). The HCIL team developed and studied small touchscreen keyboards (including a study that showed users could type at 25 wpm on a touchscreen keyboard), aiding their introduction on mobile devices. They also designed and implemented multi-touch gestures such as selecting a range of a line, connecting objects, and a "tap-click" gesture to select while maintaining location with another finger.

In 1990, HCIL demonstrated a touchscreen slider, which was later cited as prior art in the lock screen patent litigation between Apple and other touchscreen mobile phone vendors (in relation to U.S. Patent 7,657,849).

In 1991-1992, the Sun Star7 prototype PDA implemented a touchscreen with inertial scrolling. In 1993, IBM released the IBM Simon the first touchscreen phone.

An early attempt at a handheld game console with touchscreen controls was Sega's intended successor to the Game Gear, though the device was ultimately shelved and never released due to the expensive cost of touchscreen technology in the early 1990s.

The first mobile phone with a capacitive touchscreen was LG Prada released in May 2007 (which was before the first iPhone).

Touchscreens would not be popularly used for video games until the release of the Nintendo DS in 2004. Until recently[when? ], most consumer touchscreens could only sense one point of contact at a time, and few have had the capability to sense how hard one is touching. This has changed with the commercialization of multi-touch technology, and the Apple Watch being released with a force-sensitive display in April 2015.

In 2007, 93% of touchscreens shipped were resistive and only 4% were projected capacitance. In 2013, 3% of touchscreens shipped were resistive and 90% were projected capacitance.

There are a variety of touchscreen technologies with different methods of sensing touch.

A resistive touchscreen panel comprises several thin layers, the most important of which are two transparent electrically resistive layers facing each other with a thin gap between. The top layer (that which is touched) has a coating on the underside surface; just beneath it is a similar resistive layer on top of its substrate. One layer has conductive connections along its sides, the other along top and bottom. A voltage is applied to one layer and sensed by the other. When an object, such as a fingertip or stylus tip, presses down onto the outer surface, the two layers touch to become connected at that point. The panel then behaves as a pair of voltage dividers, one axis at a time. By rapidly switching between each layer, the position of pressure on the screen can be detected.

Resistive touch is used in restaurants, factories and hospitals due to its high tolerance for liquids and contaminants. A major benefit of resistive-touch technology is its low cost. Additionally, as only sufficient pressure is necessary for the touch to be sensed, they may be used with gloves on, or by using anything rigid as a finger substitute. Disadvantages include the need to press down, and a risk of damage by sharp objects. Resistive touchscreens also suffer from poorer contrast, due to having additional reflections (i.e. glare) from the layers of material placed over the screen. This is the type of touchscreen that was used by Nintendo in the DS family, the 3DS family, and the Wii U GamePad.

Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched, a portion of the wave is absorbed. The change in ultrasonic waves is processed by the controller to determine the position of the touch event. Surface acoustic wave touchscreen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touchscreen.

A capacitive touchscreen panel consists of an insulator, such as glass, coated with a transparent conductor, such as indium tin oxide (ITO). As the human body is also an electrical conductor, touching the surface of the screen results in a distortion of the screen's electrostatic field, measurable as a change in capacitance. Different technologies may be used to determine the location of the touch. The location is then sent to the controller for processing. Touchscreens that use silver instead of ITO exist, as ITO causes several environmental problems due to the use of indium. The controller is typically a complementary metal-oxide-semiconductor (CMOS) application-specific integrated circuit (ASIC) chip, which in turn usually sends the signals to a CMOS digital signal processor (DSP) for processing.

Unlike a resistive touchscreen, some capacitive touchscreens cannot be used to detect a finger through electrically insulating material, such as gloves. This disadvantage especially affects usability in consumer electronics, such as touch tablet PCs and capacitive smartphones in cold weather when people may be wearing gloves. It can be overcome with a special capacitive stylus, or a special-application glove with an embroidered patch of conductive thread allowing electrical contact with the user's fingertip.

A low-quality switching-mode power supply unit with an accordingly unstable, noisy voltage may temporarily interfere with the precision, accuracy and sensitivity of capacitive touch screens.

Some capacitive display manufacturers continue to develop thinner and more accurate touchscreens. Those for mobile devices are now being produced with 'in-cell' technology, such as in Samsung's Super AMOLED screens, that eliminates a layer by building the capacitors inside the display itself. This type of touchscreen reduces the visible distance between the user's finger and what the user is touching on the screen, reducing the thickness and weight of the display, which is desirable in smartphones.

A simple parallel-plate capacitor has two conductors separated by a dielectric layer. Most of the energy in this system is concentrated directly between the plates. Some of the energy spills over into the area outside the plates, and the electric field lines associated with this effect are called fringing fields. Part of the challenge of making a practical capacitive sensor is to design a set of printed circuit traces which direct fringing fields into an active sensing area accessible to a user. A parallel-plate capacitor is not a good choice for such a sensor pattern. Placing a finger near fringing electric fields adds conductive surface area to the capacitive system. The additional charge storage capacity added by the finger is known as finger capacitance, or CF. The capacitance of the sensor without a finger present is known as parasitic capacitance, or CP.

Surface capacitance

In this basic technology, only one side of the insulator is coated with a conductive layer. A small voltage is applied to the layer, resulting in a uniform electrostatic field. When a conductor, such as a human finger, touches the uncoated surface, a capacitor is dynamically formed. The sensor's controller can determine the location of the touch indirectly from the change in the capacitance as measured from the four corners of the panel. As it has no moving parts, it is moderately durable but has limited resolution, is prone to false signals from parasitic capacitive coupling, and needs calibration during manufacture. It is therefore most often used in simple applications such as industrial controls and kiosks.

Although some standard capacitance detection methods are projective, in the sense that they can be used to detect a finger through a non-conductive surface, they are very sensitive to fluctuations in temperature, which expand or contract the sensing plates, causing fluctuations in the capacitance of these plates. These fluctuations result in a lot of background noise, so a strong finger signal is required for accurate detection. This limits applications to those where the finger directly touches the sensing element or is sensed through a relatively thin non-conductive surface.

Projected capacitance

Projected capacitive touch (PCT; also PCAP) technology is a variant of capacitive touch technology but where sensitivity to touch, accuracy, resolution and speed of touch have been greatly improved by the use of a simple form of "Artificial Intelligence". This intelligent processing enables finger sensing to be projected, accurately and reliably, through very thick glass and even double glazing.

Some modern PCT touch screens are composed of thousands of discrete keys, but most PCT touch screens are made of a matrix of rows and columns of conductive material, layered on sheets of glass. This can be done either by etching a single conductive layer to form a grid pattern of electrodes, or by etching two separate, perpendicular layers of conductive material with parallel lines or tracks to form a grid. The conductive layer is often transparent, being made of Indium tin oxide (ITO), a transparent electrical conductor. In some designs, voltage applied to this grid creates a uniform electrostatic field, which can be measured. When a conductive object, such as a finger, comes into contact with a PCT panel, it distorts the local electrostatic field at that point. This is measurable as a change in capacitance. If a finger bridges the gap between two of the "tracks", the charge field is further interrupted and detected by the controller. The capacitance can be changed and measured at every individual point on the grid. This system is able to accurately track touches.

Due to the top layer of a PCT being glass, it is sturdier than less-expensive resistive touch technology. Unlike traditional capacitive touch technology, it is possible for a PCT system to sense a passive stylus or gloved finger. However, moisture on the surface of the panel, high humidity, or collected dust can interfere with performance. These environmental factors, however, are not a problem with 'fine wire' based touchscreens due to the fact that wire based touchscreens have a much lower 'parasitic' capacitance, and there is greater distance between neighbouring conductors.

There are two types of PCT: mutual capacitance and self-capacitance.

Mutual capacitance

This is a common PCT approach, which makes use of the fact that most conductive objects are able to hold a charge if they are very close together. In mutual capacitive sensors, a capacitor is inherently formed by the row trace and column trace at each intersection of the grid. A 16×14 array, for example, would have 224 independent capacitors. A voltage is applied to the rows or columns. Bringing a finger or conductive stylus close to the surface of the sensor changes the local electrostatic field, which in turn reduces the mutual capacitance. The capacitance change at every individual point on the grid can be measured to accurately determine the touch location by measuring the voltage in the other axis. Mutual capacitance allows multi-touch operation where multiple fingers, palms or styli can be accurately tracked at the same time.

Self-capacitance

Self-capacitance sensors can have the same X-Y grid as mutual capacitance sensors, but the columns and rows operate independently. With self-capacitance, the capacitive load of a finger is measured on each column or row electrode by a current meter, or the change in frequency of an RC oscillator.

A finger may be detected anywhere along the whole length of a row. If that finger is also detected by a column, then it can be assumed that the finger position is at the intersection of this row/column pair. This allows for the speedy and accurate detection of a single finger, but it causes some ambiguity if more than one finger is to be detected. Two fingers may have four possible detection positions, only two of which are true. However, by selectively de-sensitizing any touch-points in contention, conflicting results are easily eliminated. This enables "Self Capacitance" to be used for multi-touch operation.

Alternatively, ambiguity can be avoided by applying a "de-sensitizing" signal to all but one of the columns . This leaves just a short section of any row sensitive to touch. By selecting a sequence of these sections along the row, it is possible to determine the accurate position of multiple fingers along that row. This process can then be repeated for all the other rows until the whole screen has been scanned.

Self-capacitive touch screen layers are used on mobile phones such as the Sony Xperia Sola, the Samsung Galaxy S4, Galaxy Note 3, Galaxy S5, and Galaxy Alpha.

Self capacitance is far more sensitive than mutual capacitance and is mainly used for single touch, simple gesturing and proximity sensing where the finger does not even have to touch the glass surface. Mutual capacitance is mainly used for multitouch applications. Many touchscreen manufacturers use both self and mutual capacitance technologies in the same product, thereby combining their individual benefits.

Use of styli on capacitive screens

Capacitive touchscreens do not necessarily need to be operated by a finger, but until recently the special styli required could be quite expensive to purchase. The cost of this technology has fallen greatly in recent years and capacitive styli are now widely available for a nominal charge, and often given away free with mobile accessories. These consist of an electrically conductive shaft with a soft conductive rubber tip, thereby resistively connecting the fingers to the tip of the stylus.

An infrared touchscreen uses an array of X-Y infrared LED and photodetector pairs around the edges of the screen to detect a disruption in the pattern of LED beams. These LED beams cross each other in vertical and horizontal patterns. This helps the sensors pick up the exact location of the touch. A major benefit of such a system is that it can detect essentially any opaque object including a finger, gloved finger, stylus or pen. It is generally used in outdoor applications and POS systems that cannot rely on a conductor (such as a bare finger) to activate the touchscreen. Unlike capacitive touchscreens, infrared touchscreens do not require any patterning on the glass which increases durability and optical clarity of the overall system. Infrared touchscreens are sensitive to dirt and dust that can interfere with the infrared beams, and suffer from parallax in curved surfaces and accidental press when the user hovers a finger over the screen while searching for the item to be selected.

A translucent acrylic sheet is used as a rear-projection screen to display information. The edges of the acrylic sheet are illuminated by infrared LEDs, and infrared cameras are focused on the back of the sheet. Objects placed on the sheet are detectable by the cameras. When the sheet is touched by the user, the deformation results in leakage of infrared light which peaks at the points of maximum pressure, indicating the user's touch location. Microsoft's PixelSense tablets use this technology.

Optical touchscreens are a relatively modern development in touchscreen technology, in which two or more image sensors (such as CMOS sensors) are placed around the edges (mostly the corners) of the screen. Infrared backlights are placed in the sensor's field of view on the opposite side of the screen. A touch blocks some lights from the sensors, and the location and size of the touching object can be calculated (see visual hull). This technology is growing in popularity due to its scalability, versatility, and affordability for larger touchscreens.

Introduced in 2002 by 3M, this system detects a touch by using sensors to measure the piezoelectricity in the glass. Complex algorithms interpret this information and provide the actual location of the touch. The technology is unaffected by dust and other outside elements, including scratches. Since there is no need for additional elements on screen, it also claims to provide excellent optical clarity. Any object can be used to generate touch events, including gloved fingers. A downside is that after the initial touch, the system cannot detect a motionless finger. However, for the same reason, resting objects do not disrupt touch recognition.

The key to this technology is that a touch at any one position on the surface generates a sound wave in the substrate which then produces a unique combined signal as measured by three or more tiny transducers attached to the edges of the touchscreen. The digitized signal is compared to a list corresponding to every position on the surface, determining the touch location. A moving touch is tracked by rapid repetition of this process. Extraneous and ambient sounds are ignored since they do not match any stored sound profile. The technology differs from other sound-based technologies by using a simple look-up method rather than expensive signal-processing hardware. As with the dispersive signal technology system, a motionless finger cannot be detected after the initial touch. However, for the same reason, the touch recognition is not disrupted by any resting objects. The technology was created by SoundTouch Ltd in the early 2000s, as described by the patent family EP1852772, and introduced to the market by Tyco International's Elo division in 2006 as Acoustic Pulse Recognition. The touchscreen used by Elo is made of ordinary glass, giving good durability and optical clarity. The technology usually retains accuracy with scratches and dust on the screen. The technology is also well suited to displays that are physically larger.

This section needs expansion. You can help by adding to it.

There are several principal ways to build a touchscreen. The key goals are to recognize one or more fingers touching a display, to interpret the command that this represents, and to communicate the command to the appropriate application.

In the resistive approach, which used to be the most popular technique, there are typically four layers:

1. Top polyester-coated layer with a transparent metallic-conductive coating on the bottom.

2. Adhesive spacer

3. Glass layer coated with a transparent metallic-conductive coating on the top

4. Adhesive layer on the backside of the glass for mounting.

When a user touches the surface, the system records the change in the electric current that flows through the display.

Dispersive-signal technology measures the piezoelectric effect -the voltage generated when mechanical force is applied to a material-that occurs chemically when a strengthened glass substrate is touched.

There are two infrared-based approaches. In one, an array of sensors detects a finger touching or almost touching the display, thereby interrupting infrared light beams projected over the screen. In the other, bottom-mounted infrared cameras record heat from screen touches.

The x/y layout, commonly used in touchscreens, has also been improved by using a diagonal lattice layout, where there are no dedicated x or y elements, but each element may be transmitting or sensing at different times during a scan of the touchscreen. This means that there are nearly twice as many cross-over points for a fixed number of terminal connections and no 'bussed' connections around the edges of the touchscreen .

In each case, the system determines the intended command based on the controls showing on the screen at the time and the location of the touch.

The development of multi-touch screens facilitated the tracking of more than one finger on the screen; thus, operations that require more than one finger are possible. These devices also allow multiple users to interact with the touchscreen simultaneously.

With the growing use of touchscreens, the cost of touchscreen technology is routinely absorbed into the products that incorporate it and is nearly eliminated. Touchscreen technology has demonstrated reliability and is found in airplanes, automobiles, gaming consoles, machine control systems, appliances, and handheld display devices including cellphones; the touchscreen market for mobile devices was projected to produce US$5 billion by 2009.[needs update ]

The ability to accurately point on the screen itself is also advancing with the emerging graphics tablet-screen hybrids. Polyvinylidene fluoride (PVFD) plays a major role in this innovation due its high piezoelectric properties, which allow the tablet to sense pressure, making such things as digital painting behave more like paper and pencil.

TapSense, announced in October 2011, allows touchscreens to distinguish what part of the hand was used for input, such as the fingertip, knuckle and fingernail. This could be used in a variety of ways, for example, to copy and paste, to capitalize letters, to activate different drawing modes, etc.

A real practical integration between television-images and the functions of a normal modern PC could be an innovation in the near future: for example "all-live-information" on the internet about a film or the actors on video, a list of other music during a normal video clip of a song or news about a person.

For touchscreens to be effective input devices, users must be able to accurately select targets and avoid accidental selection of adjacent targets. The design of touchscreen interfaces should reflect technical capabilities of the system, ergonomics, cognitive psychology and human physiology.

Guidelines for touchscreen designs were first developed in the 1990s, based on early research and actual use of older systems, typically using infrared grids-which were highly dependent on the size of the user's fingers. These guidelines are less relevant for the bulk of modern devices which use capacitive or resistive touch technology.

From the mid-2000s, makers of operating systems for smartphones have promulgated standards, but these vary between manufacturers, and allow for significant variation in size based on technology changes, so are unsuitable from a human factors perspective.

Much more important is the accuracy humans have in selecting targets with their finger or a pen stylus. The accuracy of user selection varies by position on the screen: users are most accurate at the center, less so at the left and right edges, and least accurate at the top edge and especially the bottom edge. The R95 accuracy (required radius for 95% target accuracy) varies from 7 mm (0.28 in) in the center to 12 mm (0.47 in) in the lower corners. Users are subconsciously aware of this, and take more time to select targets which are smaller or at the edges or corners of the touchscreen.

This user inaccuracy is a result of parallax, visual acuity and the speed of the feedback loop between the eyes and fingers. The precision of the human finger alone is much, much higher than this, so when assistive technologies are provided-such as on-screen magnifiers-users can move their finger (once in contact with the screen) with precision as small as 0.1 mm (0.004 in).[dubious ]

Hand position, digit used and switching

Users of handheld and portable touchscreen devices hold them in a variety of ways, and routinely change their method of holding and selection to suit the position and type of input. There are four basic types of handheld interaction:

Holding at least in part with both hands, tapping with a single thumb

Holding with two hands and tapping with both thumbs

Holding with one hand, tapping with the finger (or rarely, thumb) of another hand

Holding the device in one hand, and tapping with the thumb from that same hand

Use rates vary widely. While two-thumb tapping is encountered rarely (1-3%) for many general interactions, it is used for 41% of typing interaction.

In addition, devices are often placed on surfaces (desks or tables) and tablets especially are used in stands. The user may point, select or gesture in these cases with their finger or thumb, and vary use of these methods.

Touchscreens are often used with haptic response systems. A common example of this technology is the vibratory feedback provided when a button on the touchscreen is tapped. Haptics are used to improve the user's experience with touchscreens by providing simulated tactile feedback, and can be designed to react immediately, partly countering on-screen response latency. Research from the University of Glasgow (Brewster, Chohan, and Brown, 2007; and more recently Hogan) demonstrates that touchscreen users reduce input errors (by 20%), increase input speed (by 20%), and lower their cognitive load (by 40%) when touchscreens are combined with haptics or tactile feedback. On top of this, a study conducted in 2013 by Boston College explored the effects that touchscreens haptic stimulation had on triggering psychological ownership of a product. Their research concluded that a touchscreens ability to incorporate high amounts of haptic involvement resulted in customers feeling more endowment to the products they were designing or buying. The study also reported that consumers using a touchscreen were willing to accept a higher price point for the items they were purchasing.

Touchscreen technology has become integrated into many aspects of customer service industry in the 21st century. The restaurant industry is a good example of touchscreen implementation into this domain. Chain restaurants such as Taco Bell, Panera Bread, and McDonald's offer touchscreens as an option when customers are ordering items off the menu. While the addition of touchscreens is a development for this industry, customers may choose to bypass the touchscreen and order from a traditional cashier. To take this a step further, a restaurant in Bangalore has attempted to completely automate the ordering process. Customers sit down to a table embedded with touchscreens and order off an extensive menu. Once the order is placed it is sent electronically to the kitchen. These types of touchscreens fit under the Point of Sale (POS) systems mentioned in the lead section.

"Gorilla arm"

Extended use of gestural interfaces without the ability of the user to rest their arm is referred to as "gorilla arm". It can result in fatigue, and even repetitive stress injury when routinely used in a work setting. Certain early pen-based interfaces required the operator to work in this position for much of the workday. Allowing the user to rest their hand or arm on the input device or a frame around it is a solution for this in many contexts. This phenomenon is often cited as an example of movements to be minimized by proper ergonomic design.[citation needed ]

Unsupported touchscreens are still fairly common in applications such as ATMs and data kiosks, but are not an issue as the typical user only engages for brief and widely spaced periods.

Touchscreens can suffer from the problem of fingerprints on the display. This can be mitigated by the use of materials with optical coatings designed to reduce the visible effects of fingerprint oils. Most modern smartphones have oleophobic coatings, which lessen the amount of oil residue. Another option is to install a matte-finish anti-glare screen protector, which creates a slightly roughened surface that does not easily retain smudges.

Touchscreens do not work most of the time when the user wears gloves. The thickness of the glove and the material they are made of play a significant role on that and the ability of a touchscreen to pick up a touch.

Shneiderman, B. (1991). "Touch screens now offer compelling uses". IEEE Software. 8 (2): 93-94, 107. doi:10.1109/52.73754. S2CID 14561929.

Potter, R.; Weldon, L. & Shneiderman, B. (1988). An experimental evaluation of three strategies. Proc. CHI'88. Washington, DC: ACM Press. pp. 27-32.

Sears, A.; Plaisant, C. & Shneiderman, B. (1992). "A new era for high precision touchscreens". In Hartson, R. & Hix, D. (eds.). Advances in Human-Computer Interaction. 3. Ablex, NJ. pp. 1-33.

Holzinger, A. (2003). Carbonell, N.; Stephanidis, C. (eds.). "Finger Instead of Mouse: Touch Screens as a means of enhancing Universal Access". Universal Access, Lecture Notes in Computer Science. Lecture Notes in Computer Science. 2615: 387-397. doi:10.1007/3-540-36572-9_30. ISBN 978-3-540-00855-2. S2CID 34969584.

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A , or touch screen, is both an input and output device and normally layered on the top of an electronic visual display of an information processing system. The display is often an LCD or OLED display while the system is usually a laptop, tablet, or smartphone.

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Just like it sounds, a manual or hand burr grinder uses manual energy. In a manual burr grinder, you crank the swivel arm continuously thus providing the necessary power required to rotate the burrs and crush the beans. The texture of coffee obtained mainly depends on the amount of energy or effort that you put in combined with your grinder settings. A coarse grind will come out quickly and will require less energy. On the other hand, if you want a fine grind, then you will spend more time grinding the beans to the desired level.

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One of the main benefits of using electric coffee grinders is convenience. They are simple and fast to use. You just fill the hopper with the coffee beans, select the preferred grind size, and then press the switch. Within a few seconds, you will have freshly ground coffee, which is ready to be brewed. One of the main disadvantages of electric coffee grinders, is they are quite expensive. In fact, you will achieve better grinds using a manual grinder, than an electric one less than $100.

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Burr grinders use two revolving abrasive surfaces to grind up coffee while blade grinders use a propeller-like blade, similar to a blender

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A blade grinder is a machine that chops coffee beans and spices while mixing it. There is a blade in the center of the grinder that looks like a propeller, similar to a blade in a blender or a food processor. This grinder offers more power for faster grinding, but coffee grounds can be uneven in size.

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Being able to pop a little pod into your coffee machine and get out a freshly brewed cup of coffee is one of the most used inventions of our time. So, how do these magical devices create the perfect cup of joe on demand?
One of the biggest things that single-serving coffee makers brought to the industry was the ease of use. It used to be that you had to have coffee ground, then measure it out, get a coffee filter, pour water, and brew. That isn't arguably an arduous task, but it still took time in your groggy morning mood. Pod coffee makers have brought a variety of flavors into our morning routines all with a few pushes of a button.

The first steps of the coffee maker

The first thing that needs to happen in a single serving coffee maker is for the user to fill up the reservoir in the back. Following this, simply pop a pod in and press brew. Here's where the engineering and magic begins. That wurrrrrrrr noise you hear when your coffee maker starts is actually a little pump that starts pushing water through the machine. In most cases, this pump consists of a small motor with an uneven roller on it.
RELATED: THIS PORTABLE LITHIUM ION POWERED COFFEE MAKER CAN GIVE YOU A CAFFEINE FIX ON THE GO
This uneven roller will cause a flexible tube to move in a pumping action, sucking water through. However, many coffee makers won't use a pump; in fact, some coffee makers have no moving parts. Rather they use what is called a check valve - a valve that only allows flow in one direction. Water flows through the check valve due to gravity to the heater. The heater heats the water, creating a difference in temperature between the heated water and the reservoir.

This differential causes flow from the reservoir to the heater, and the check valve keeps the water moving in one direction. This principle allows many coffee makers to operate with only tubing and a heater, no moving parts. You can learn more about this principle in the video below.

The heating element is the next step in the process. Oftentimes coffee makers will use coiled copper tubing that gets heated. This increases the surface area of the water in contact with the heated metal and speeds up the process. Some coffee makers will use heated reservoirs, but by far, the most common are coiled heated tubing. The heat is created through electrical resistance. A current tries to flow through the metal, which presents significant resistance to the flow of energy. These heaters are typically 1500 watts and will bring your coffee to 185 degrees Fahrenheit. This resistance transforms the electrical energy into heat energy, bringing your coffee water up to temperature.

The final steps in the process

Now, your coffee water has been pumped to the top of the coffee machine. At the end of the tube, there is a narrowing, hose-like nozzle that increases the pressure of the water. This high-pressure water is pumped in and throughout the pod, only to exit through the small hole poked in the bottom of the pod when you popped it into the machine.

This pressurization of the water ensures that the whole pod's flavor gets used, and the water makes it all the way through the coffee capsule. If you wanted to dissect a single-serving coffee pod, you would see that the coffee actually rests on a final layer of filter paper that keeps your coffee from being full of grounds. The final step in the process is to fill up that mug and for you to enjoy.
RELATED: THE TRUTH ABOUT COFFEE AND YOUR POOP
One thing you may not expect to be in your single-serving coffee maker is an air compressor. That final blast of steam you see come out of your machine is actually a burst from the air compressor used to clear out the pipes. This keeps your machine clean after every use and ensures the perfect brew every time.

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Take a Look at the Interesting Engineering Behind Single Serving Coffee Makers

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Being able to pop a little pod into your coffee machine and get out a freshly brewed cup of coffee is one of the most used inventions of our time. So, how do these magical devices create the perfect cup of joe on demand?

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A thermoblock or thermocoil takes water from the reservoir in an espresso machine and heats it on the fly, versus heating up a full boiler of water. This technology is commonly seen on home espresso machines, where it manages either the brew function, steam function or both. The benefit of a thermoblock is that it doesn't take as long for your machine to heat up for either brew or steam; however, the drawback can be that your temperature for brew or steam is not quite as consistent as you might like.

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Metals which do not react with food items.

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Metals which do not react with food items.

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Pour over, water displacement drip coffeemakers. 

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Pour over, water displacement drip coffeemakers. 

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The machine uses a holding tank or boiler pre-filled with water. When the machine is turned on, all of the water in the holding tank is brought to near boiling point (approximately 200–207 °F or 93–97 °C) using a thermostatically-controlled heating element. When water is poured into a top-mounted tray, it descends into a funnel and tube which delivers the cold water to the bottom of the boiler. The less-dense hot water in the boiler is displaced out of the tank and into a tube leading to the spray head, where it drips into a brew basket containing the ground coffee.

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Pour over coffee has been embraced by the specialty coffee scene in recent years and there is much discussion about the best techniques and tools to use.

But the filter method isn't just for competitions and specialty coffee shops. At heart, it's a straightforward way to make a delicious cup of coffee. Whether you're a new home brewer or a seasoned barista, drip coffee can work for you. Take a look at this comprehensive guide to brewing pour over coffee.
Prefer audio? Listen to the podcast below

A barista at Linear Coffee Roasters adds a measured dose of ground coffee to a filter in a Kalita Wave. Credit: Nathaniel Soque

What Is Pour Over Coffee?

The pour over method involves pouring hot water through coffee grounds in a filter. The water drains through the coffee and filter into a carafe or mug. Pour over is also known as filter coffee or drip coffee, although these terms also include batch brewers.

What sets pour over apart is that it is made by hand-pouring the water over the coffee. So you may hear it called hand brewing or manual brewing.

The technique has been commonly used in Europe since the 1900s and for much longer, but was "rediscovered" by the specialty coffee movement in recent years.

A barista pours water on to coffee for the bloom. Credit: Nathaniel Soque
Why Use The Pour Over Method?

Pour over accentuates intricate flavors when compared to other brewing methods. This makes it a popular choice for single origin coffees, since it allows the flavors and aromas to shine.

Good filter coffee is clean, clear, and consistent. This is because the water is allowed to coffee oils and fragrances in its own consistent time and at its own pressure. The filter then catches a lot of oils, leading to a clean cup.

And because this is an infusion method, it is a little more efficient at extracting coffee solubles than immersion techniques such as the French press. Immersion methods cause the water to become saturated, whereas pour overs use a constant supply of fresh water.

is New Zealand 2017 Brewers Cup Champion. She says, "I don't think that the method we use changes the flavor, but [it can highlight] more of the nuances. I don't think the equipment changes the whole coffee flavor and taste, but some people believe that it does."

The top three at the 2017 New Zealand Brewers Cup: Sarah Stevens, left, second place; Nara Lee, center, 2017 New Zealand Brewers Cup Champion; Dianne Wang, right, third place. Credit: Nick Kean
But pour over coffee has some challenges. Manual methods are victim to human error and bad pouring techniques.

For example, all infusion methods (including espresso) run the risk of channeling, where a stream of water finds an easy route around the ground coffee. This happens when there are clumps of coffee or the grounds are unevenly distributed, and it means that some of the coffee doesn't get extracted. So it's important that baristas learns how to pour in a way that evenly immerses the grounds in water.

Because it is difficult to replicate a method precisely every time, some café owners and brewers prefer to use SCA-approved batch brewers instead. These machines bring automation to the method and can have more consistent results than a hand pour.

A barista makes a pour over at Mothership Coffee Roasters in Las Vegas. Credit: Nathaniel Soque

What Equipment Do You Need?

It may seem like there is an unending amount of options for pour over equipment, but you don't need to invest in all of it. You can start with a simple device and some filters and then add more equipment as you choose.

is World Brewers Cup Champion 2017. He says "It's very important to understand that the cup quality of the end result is much more important than being technical about your recipe or choosing a V60 over a Clever."

Let's take a look at what the basic equipment you need to make a pour over.

A brewing device or dripper is simply the piece of equipment that holds the coffee filter and grounds. The , Kalita Wave , and Melitta are popular choices. All three sit on top of the cup or carafe and they may seem interchangeable. But there are specific design features to each that aid flow and affect extraction. The is another popular option with its own design features that impact the cup.

The advantage of using any one of these devices is that they are widely available, simple to use, and have filters made specifically for their design. There are also many online guides and hacks to using these devices so it's easy to learn how to use them properly and adapt as needed.

If you're not sure where to start, try brews made in different devices in your local specialty coffee shop and ask the barista which they prefer and why.

Lanz of Linear Coffee Roasters , in Cebu City, Philippines, pours water into a V60 device. Credit: Nathaniel Soque

Paper or cloth? Bleached or unbleached? You may think that the filter is the least controversial part of brewing, but there is even some debate here. Specific filters are designed to fit different devices and allow efficient extraction. The Chemex uses paper filters that are 20-30% heavier than other filters, which the manufacturers say retain more of the suspended oils during the brewing process.

Some claim that paper filters create an undesirable papery taste, particularly if they are bleached. To avoid this, rinse your filter before using it. Cloth filters have been around for a long time and some people prefer them because they don't affect flavor and have a smaller environmental impact than paper.

It's up to you which specific filters you choose, but make sure they fit your device properly. Bunched-up paper or cloth will impede water flow and trap coffee grounds, which will make your extraction less consistent.

You may not think scales are essential, but if you want to create consistently good coffee, they are. Invest in a digital scale and use it to measure your coffee and water. Knowing exactly how much of each you used in a good (or bad) brew can allow you to replicate the recipe or tweak it for even better results.

Have you seen specialty baristas pour water from a small copper kettle and wondered why? Can't you just use a standard electric kettle? Yes, you can. But you may choose not to.

Like many things in specialty coffee, the important factor here is consistency. Kettles made specifically for pour over are designed to keep water at a stable temperature. This helps you create consistent extraction. And that long, thin gooseneck is designed to control the flow of water. Water tends to gush out of kettles with shorter spouts.

Whether you choose electric, stove-top, or a batch water heater is up to you but look into the reviews of specific kettles and keep a thermometer handy to keep an eye on the temperature.

Which Coffee Should You Use?

So you have your equipment ready, but now what? Which coffee should you use with a pour over? There are a few factors to consider when choosing your beans.

Because the pour over method works well to highlight subtle flavor notes and aromas, you may want to choose a light roast. Beans that are roasted to this profile are the brightest, with the most acidic flavors.

Chad says "Light roasts showcase the most authentic quality of the coffee."

Of course, you can go medium or even dark if you prefer, but this brewing method is complementary to subtle flavors.

The size of your grounds affects the rate of extraction. Pour over is a an infusion method, which means that the coffee and water are in contact for a shorter amount of time than in an immersion method, but longer than in an espresso. So you want the coffee to have enough surface area to extract before the water filters through into the cup, but not so much that they under-extract and produce a bitter brew.

What this means is that you should start with a medium grind size and then evaluate your cup and tweak it as needed. If it's a little watery or sour, try a finer grind. If it's bitter and lacking sweet notes, try going a little coarser.

And invest in a quality grinder to make sure your coffee particles are all ground to the same size. Lower-quality grinders may produce inconsistently ground coffee and a lot of "fines". These tiny fragments of coffee extract very quickly and can throw your cup off.

Stathis Koremtas holds his trophy at the 2017 World Brewers Cup, where he took third place. Credit: Stathis Koremtas
Stathis Koremtas is the 2018 Greece Greece National Brewer's Cup Champion. He is also a barista at and tells me how he prepares a V60 there.

"We use finely ground, not coarse," he says. "We play with the temperature of the water. So we have 92°C [198°F] water and we try to make a fast extraction, to finish the whole process in 2 mins to 2 minutes, 10 seconds."

"The advantage of the fine grind size is that you increase the body and aroma of the coffee. And if you are going to make a fast extraction, you're also going to get the sweetness and the cleanliness that you want in the cup."

What Ratio of Coffee to Water Should You Use?

You'll see a lot of different suggested ratios out there, but 1:17 (1g of coffee to 17g of water) is a generally accepted good starting point. Make some brews with this measurement but adjust factors that affect extraction, such as grind size and water temperature, one at a time until you find a recipe that works for you.

Then, try changing the ratio of coffee to water. If your brew tastes watery or weak, add more coffee without changing other factors and evaluate whether it tastes better. If you find your cup too intense, consider reducing the amount of coffee. But remember to keep track of what you're changing so you can replicate your perfect brew when you find it.

And don't forget about the water. Tap water can contain minerals and contaminants that affect flavor, so use filtered water.

Which Pouring Technique Is Best?

Avoid watching too many videos on technique when you first start to brew with the pour over method. It can quickly get overwhelming. Instead, start out simple. Be consistent in how your pour and learn how to use blooming, pulse pouring, and agitation to achieve even extraction. Many people pour in concentric circles, which helps the barista maintain a consistent flow of water.

You can work your way up to more detailed methods or break all the rules when you're more familiar with the basics.

The bloom is the quick bubbling up of water that happens when you first pour. It is caused by the of carbon dioxide that is built up in the roasting process. Light roasts and fresh coffee are likely to produce a big bloom because they usually contain more gases.

Carbon dioxide can prevent even extraction because it repels water, and the disturbed grounds can sit at different heights. So let the gases escape and improve your chances of a consistent extraction.

Gently pour twice the measure of coffee in water over the grounds. So, if you have a 15 g dose of coffee, pour 30 ml of water. Then wait 30 to 45 seconds until the bloom has ended and the grounds have settled.

Pulse pouring means using multiple pours of specific amounts of water. You can experiment with the volume of water and number of pours. This technique help prevent channelling or grounds rising up the side of the filter. It also gently disrupts the grinds, causing them to move about and creating more even contact with the water.

It's an alternative to continuous pouring, which is when the barista pours the water at as constant of a flow rate as possible without stopping. Continuous pouring aims to keep the flow and saturation as even as possible, whereas pulse pouring is intentionally varied.

You can use pouring technique as another variable to consider when adapting your recipe. Different types of pours will have different effects on extraction and therefore have different impacts on your brew.

This is simply mild disturbance of the coffee grounds during the brew process. There are many ways to agitate coffee, including stirring or swirling the brew.

Agitation disperses grounds that can be left "high and dry" on the filter by channeling. It also breaks up any dry clumps inside the bed of coffee. By making sure all grounds are saturated, agitation aids even extraction.

Pour over coffee can be a great way to make your daily cup and it doesn't have to be complicated. By understanding these key topics, you're well prepared to make a decent brew and have the tools to tweak it until it becomes a great one.

So what are you waiting for? Unpack your V60, Kalita Wave, or Chemex and invest in some specialty coffee. The world of the pour over is yours to explore
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Everything You Need to Know to Brew Great Pour Over Coffee

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Pour over coffee has been embraced by the specialty coffee scene in recent years and there is much discussion about the best techniques and tools to use. But the filter method isn't just for competitions and specialty coffee shops. At heart, it's a straightforward way to make a delicious cup of coffee.

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A coffee percolator is a type of pot used for the brewing of coffee by continually cycling the boiling or nearly boiling brew through the grounds using gravity until the required strength is reached.
https://en.wikipedia.org/wiki/Coffee_percolator

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A vacuum coffee maker operates as a siphon, where heating and cooling the lower vessel changes the vapor pressure of water in the lower, first pushing the water up into the upper vessel, then allowing the water to fall back down into the lower vessel.

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In order to make body of coffee maker

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A coffee filter is a coffee-brewing utensil, usually made of disposable paper. This enables it to trap the coffee grounds and allow the liquid coffee to flow through.

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In order to run our coffee machine we have to give the machine some kind of energy like electricity.

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The user interface (UI) is the point of human-computer interaction and communication in a device. This can include display screens, keyboards, a mouse and the appearance of a desktop. It is also the way through which a user interacts with an application or a website.