Quadrant Model of Reality Book 22 Silicon

Silicon chapter

Silicon is known as the miracle element because it is so important, especially in electronics. It has four valence electrons, making git look like a quadrant.

Production[edit]

Reactive-ion etching[edit]

Scanning electron micrograph of a single "needle" of black silicon, produced by RIE (ASE process)

In semiconductor technology, reactive-ion etching (RIE) is a standard procedure for producing trenches and holes with a depth of up to several hundred micrometres and very high aspect ratios. In Bosch process RIE, this is achieved by repeatedly switching between an etching and passivation. With cryogenic RIE, the low temperature and oxygen gas achieve this sidewall passivation by forming SiO

2, easily removed from the bottom by directional ions. Both RIE methods can produce black silicon, but the morphology of the resulting structure differs substantially. The switching between etching and passivation of the Bosch process creates undulated sidewalls, which are visible also on the black silicon formed this way.

During etching, however, small debris remain on the substrate; they mask the ion beam and produce structures that are not removed and in the following etching steps and result in tall silicon pillars.[16] The process can be set so that a million needles are formed on an area of one square millimeter.[12]

Mazur's method[edit] In 1999, a Harvard University group developed a process in which black silicon was produced by irradiating silicon with femtosecond laser pulses.[17] After irradiation in the presence of a gas containing sulfur hexafluoride and other dopants, the surface of silicon develops a self-organized microscopic structure of micrometer-sized cones. The resulting material has many remarkable properties, such as absorption that extends to the infrared range, below the band gap of silicon, including wavelengths for which ordinary silicon is transparent. sulfur atoms are forced to the silicon surface, creating a structure with a lower band gap and therefore the ability to absorb longer wavelengths. Black silicon made without special gas ambient - laboratory LP3-CNRS Similar surface modification can be achieved in vacuum using the same type of laser and laser processing conditions. In this case, the individual silicon cones lack sharp tips (see image). The reflectivity of such a micro-structured surface is very low, 3-14% in the spectral range 350–1150 nm.[18] Such reduction in reflectivity is contributed by the cone geometry, which increases the light internal reflections between them. Hence, the possibility of light absorption is increased. The gain in absorption achieved by fs laser texturization was superior to that achieved by using an alkaline chemical etch method,[19] which is a standard industrial approach for surface texturing of mono-crystalline silicon wafers in solar cell manufacturing. Such surface modification is independent of local crystalline orientation. A uniform texturing effect can be achieved across the surface of a multi-crystalline silicon wafer. The very steep angles lower the reflection to near zero and also increase the probability of recombination, keeping it from use in solar cells

Applications[edit] The unusual optical characteristics, combined with the semiconducting properties of silicon make this material interesting for sensor applications. Potential applications include:[6] Image sensors with increased sensitivity Thermal imaging cameras Photodetector with high-efficiency through increased absorption.[7][8] Mechanical contacts and interfaces [2] Terahertz applications.[9][10][11][12] Solar cells[3][13][14] Antibacterial surfaces[15] that work by physically rupturing bacteria's cellular membranes.

Properties[edit] Scanning electron micrograph of black silicon, produced by RIE (ASE process) SEM micrograph of black silicon formed by cryogenic RIE. Notice the smooth, sloped surfaces, unlike the undulated sidewalls obtained with the Bosch process RIE. Black silicon is a needle-shaped surface structure where needles are made of single-crystal silicon and have a height above 10 µm and diameter less than 1 µm.[2] Its main feature is an increased absorption of incident light—the high reflectivity of the silicon, which is usually 20–30% for quasi-normal incidence, is reduced to about 5%. This is due to the formation of a so-called effective medium[4] by the needles. Within this medium, there is no sharp interface, but a continuous change of the refractive index that reduces Fresnel reflection. When the depth of the graded layer is roughly equal to the wavelength of light in silicon (about one-quarter the wavelength in vacuum) the reflection is reduced to 5%; deeper grades produce even blacker silicon.[5] For low reflectivity, the nanoscale features producing the index graded layer must be smaller than the wavelength of the incident light to avoid scattering.[5]

QMRBlack silicon is a semiconductor material, a surface modification of silicon with very low reflectivity and correspondingly high absorption of visible (and infrared) light. The modification was discovered in the 1980s as an unwanted side effect of reactive ion etching (RIE).[1][2] Other methods for forming a similar structure include electrochemical etching, stain etching, metal-assisted chemical etching, and laser treatment (which is developed in Eric Mazur's laboratory at Harvard University ), and FFC Cambridge process (an electrochemical reduction process).

QMRSilicon Valley is a nickname for the southern portion of the San Francisco Bay Area, which is located in part of the U.S. state of California known as Northern California. It is home to many of the world's largest high-tech corporations, as well as thousands of startup companies. Geographically, it encompasses all of the Santa Clara Valley, the southern half of the San Francisco Peninsula, and southern portions of the East Bay. It includes parts or most of Santa Clara County, San Mateo County, and Alameda County.

The word "valley" refers to the Santa Clara Valley, where the region has traditionally been centered, which includes the city of San Jose and surrounding cities and towns. The word "silicon" originally referred to the large number of silicon chip innovators and manufacturers in the region. The term "Silicon Valley" eventually came to refer to all high tech businesses in the area, and is now generally used as a synecdoche for the American high-technology economic sector. It also became a global synonym for leading high-tech research and enterprises, and thus inspired similar named locations, as well as research parks and technology centers with a comparable structure all around the world.

Silicon Valley is a leading hub and startup ecosystem for high-tech innovation and development, accounting for one-third of all of the venture capital investment in the United States. It was in the Valley that the silicon-based integrated circuit, the microprocessor, and the microcomputer, among other key technologies, were developed. As of 2013, the region employed about a quarter of a million information technology workers.[1]

printed silicon electronics wiki

Biological role Silica skeletons of radiolaria in false color. Although silicon is readily available in the form of silicates, very few organisms have a use for it. Diatoms, radiolaria and siliceous sponges use biogenic silica as a structural material to construct skeletons. In more advanced plants, the silica phytoliths (opal phytoliths) are rigid microscopic bodies occurring in the cell; some plants, for example rice, need silicon for their growth.[65][66][67] The possible biological potential of silicon as bioavailable orthosilicic acid and the potential beneficial effects on human health has been reviewed.[68] Silicon is needed for synthesis of elastin and collagen;[not in citation given] the aorta contains the highest quantity of elastin and silicon.[69] Silicon is currently under consideration for elevation to the status of a "plant beneficial substance by the Association of American Plant Food Control Officials (AAPFCO)."[70][71] Silicon has been shown in university and field studies to improve plant cell wall strength and structural integrity,[72] improve drought and frost resistance, decrease lodging potential and boost the plant's natural pest and disease fighting systems.[73] Silicon has also been shown to improve plant vigor and physiology by improving root mass and density, and increasing above ground plant biomass and crop yields.[72]

Mechanical watches Since 2000, silicon has found a new use in mechanical watch movements. Several manufacturers of mechanical watch movements have incorporated silicon parts, mainly in the escapements and balance wheel regions. Silicon hair-springs are becoming more common as are silicon escapement wheels and forks. Silicon has several desirable properties when used in these contexts; It is thermally stable, shock resistant, and requires little to no lubrication. Ulysse Nardin pioneered these applications, with Omega, Breguet, Patek, Rolex, Cartier, and Damasco following.[63] Most of these parts for watch movements are manufactured using deep reactive-ion etching (DRIE).[64]

In common integrated circuits, a wafer of monocrystalline silicon serves as a mechanical support for the circuits, which are created by doping, and insulated from each other by thin layers of silicon oxide, an insulator that is easily produced by exposing the element to oxygen under the proper conditions. Silicon has become the most popular material to build both high power semiconductors and integrated circuits. The reason is that silicon is the semiconductor that can withstand the highest temperatures and electrical powers without becoming dysfunctional due to avalanche breakdown (a process in which an electron avalanche is created by a chain reaction process whereby heat produces free electrons and holes, which in turn produce more current which produces more heat). In addition, the insulating oxide of silicon is not soluble in water, which gives it an advantage over germanium (an element with similar properties which can also be used in semiconductor devices) in certain type of fabrication techniques.[62] Monocrystalline silicon is expensive to produce, and is usually only justified in production of integrated circuits, where tiny crystal imperfections can interfere with tiny circuit paths. For other uses, other types of pure silicon which do not exist as single crystals may be employed. These include hydrogenated amorphous silicon and upgraded metallurgical-grade silicon (UMG-Si) which are used in the production of low-cost, large-area electronics in applications such as liquid crystal displays, and of large-area, low-cost, thin-film solar cells. Such semiconductor grades of silicon which are either slightly less pure than those used in integrated circuits, or which are produced in polycrystalline rather than monocrystalline form, make up roughly similar amount of silicon as are produced for the monocrystalline silicon semiconductor industry, or 75,000 to 150,000 metric tons per year. However, production of such materials is growing more quickly than silicon for the integrated circuit market. By 2013 polycrystalline silicon production, used mostly in solar cells, is projected to reach 200,000 metric tons per year, while monocrystalline semiconductor silicon production (used in computer microchips) remains below 50,000 tons/year.[30]

Electronics Main article: Semiconductor device fabrication Silicon wafer with mirror finish Most elemental silicon produced remains as ferrosilicon alloy, and only a relatively small amount (20%) of the elemental silicon produced is refined to metallurgical grade purity (a total of 1.3–1.5 million metric tons/year). The fraction of silicon metal which is further refined to semiconductor purity is estimated at only 15% of the world production of metallurgical grade silicon.[30] However, the economic importance of this small very high-purity fraction (especially the ~ 5% which is processed to monocrystalline silicon for use in integrated circuits) is disproportionately large. Pure monocrystalline silicon is used to produce silicon wafers used in the semiconductor industry, in electronics and in some high-cost and high-efficiency photovoltaic applications. In terms of charge conduction, pure silicon is an intrinsic semiconductor which means that unlike metals it conducts electron holes and electrons that may be released from atoms within the crystal by heat, and thus increase silicon's electrical conductivity with higher temperatures. Pure silicon has too low a conductivity (i.e., too high a resistivity) to be used as a circuit element in electronics. In practice, pure silicon is doped with small concentrations of certain other elements, a process that greatly increases its conductivity and adjusts its electrical response by controlling the number and charge (positive or negative) of activated carriers. Such control is necessary for transistors, solar cells, semiconductor detectors and other semiconductor devices, which are used in the computer industry and other technical applications. For example, in silicon photonics, silicon can be used as a continuous wave Raman laser medium to produce coherent light, though it is ineffective as an everyday light source.

Alloys Elemental silicon is added to molten cast iron as ferrosilicon or silicocalcium alloys to improve performance in casting thin sections and to prevent the formation of cementite where exposed to outside air. The presence of elemental silicon in molten iron acts as a sink for oxygen, so that the steel carbon content, which must be kept within narrow limits for each type of steel, can be more closely controlled. Ferrosilicon production and use is a monitor of the steel industry, and although this form of elemental silicon is grossly impure, it accounts for 80% of the world's use of free silicon. Silicon is an important constituent of electrical steel, modifying its resistivity and ferromagnetic properties. The properties of silicon can be used to modify alloys with metals other than iron. "Metallurgical grade" silicon is silicon of 95–99% purity. About 55% of the world consumption of metallurgical purity silicon goes for production of aluminium-silicon alloys (silumin alloys) for aluminium part casts, mainly for use in the automotive industry. Silicon's importance in aluminium casting is that a significantly high amount (12%) of silicon in aluminium forms a eutectic mixture which solidifies with very little thermal contraction. This greatly reduces tearing and cracks formed from stress as casting alloys cool to solidity. Silicon also significantly improves the hardness and thus wear-resistance of aluminium.[29][30]

Ceramics and glass. Silica is used to make fire brick, a type of ceramic. Silicate minerals are also in whiteware ceramics, an important class of products usually containing various types of fired clay minerals (natural aluminium phyllosilicates). An example is porcelain which is based on the silicate mineral kaolinite. Traditional glass (silica-based soda-lime glass) also functions in many of the same ways, and is also used for windows and containers. In addition, specialty silica based glass fibers are used for optical fiber, as well as to produce fiberglass for structural support and glass wool for thermal insulation.

Artificial silicon compounds. Very occasional elemental silicon is found in nature, and also naturally-occurring compounds of silicon and carbon (silicon carbide) or nitrogen (silicon nitride) are found in stardust samples or meteorites in presolar grains, but the oxidizing conditions of the inner planets of the solar system make planetary silicon compounds found there mostly silicates and silica. Free silicon, or compounds of silicon in which the element is covalently attached to hydrogen, boron, or elements other than oxygen, are mostly artificially produced. They are described below.

Silicon compounds of more modern origin function as high-technology abrasives and new high-strength ceramics based upon silicon carbide. Silicon is a component of some superalloys. Alternating silicon-oxygen chains with hydrogen attached to the remaining silicon bonds form the ubiquitous silicon-based polymeric materials known as silicones. These compounds containing silicon-oxygen and occasionally silicon-carbon bonds have the capability to act as bonding intermediates between glass and organic compounds, and to form polymers with useful properties such as impermeability to water, flexibility and resistance to chemical attack. Silicones are often used in waterproofing treatments, molding compounds, mold-release agents, mechanical seals, high temperature greases and waxes, and caulking compounds. Silicone is also sometimes used in breast implants, contact lenses, explosives and pyrotechnics.[60] Silly Putty was originally made by adding boric acid to silicone oil.[61]

Applications Compounds Building materials. Most silicon is used industrially without being separated into the element, and indeed often with comparatively little processing from natural occurrence. Over 90% of the Earth's crust is composed of silicate minerals, which are compounds of silicon and oxygen, often with metallic ions when negatively charged silicate anions require cations to balance the charge. Many of these have direct commercial uses, such as clays, silica sand and most kinds of building stone. Thus, the vast majority of uses for silicon are as structural compounds, either as the silicate minerals or silica (crude silicon dioxide). Silicates are used in making Portland cement (made mostly of calcium silicates) which is used in building mortar and modern stucco, but more importantly, combined with silica sand, and gravel (usually containing silicate minerals like granite), to make the concrete that is the basis of most of the very largest industrial building projects of the modern world. [59]

Silicon dioxide (silica) is a high melting solid with a number of crystal forms; the most familiar of which is the mineral quartz. In crystalline quartz each silicon atom is surrounded by four oxygen atoms that bridge to other silicon atoms to form a three dimensional lattice (see below for the vitreous or glass form of pure silica). [51] Silica is soluble in water at high temperatures forming a range of compounds called monosilicic acid, Si(OH)4.[52]

Under the right conditions monosilicic acid readily polymerizes to form more complex silicic acids, ranging from the simplest condensate, disilicic acid (H6Si2O7) to linear, ribbon, layer and lattice structures which form the basis of the many silicate minerals and are called polysilicic acids {Six(OH)4–2x}n.[52]

Silica can be fused directly into glass form, as so-called fused quartz, which contains no crystalline structure. With oxides of other elements, the high temperature reaction of silicon dioxide can give a wide range of mixed glasses and glass-like network solids with various properties.[53] Examples include soda-lime glass, borosilicate glass and lead crystal glass.

Silicon sulfide, SiS2, is a polymeric solid (unlike its carbon analogue the liquid CS2).[54]

Silicon forms a nitride, Si3N4 which is a ceramic.[55] Silatranes, a group of tricyclic compounds containing five-coordinate silicon, may have physiological properties.[56] Many transition metal complexes containing a metal-silicon bond are now known, which include complexes containing SiH nX 3−n ligands, SiX3 ligands, and Si(OR)3 ligands.[56] Silicones are large group of polymeric compounds with an (Si-O-Si) backbone. An example is the silicone oil PDMS (polydimethylsiloxane). These polymers can be crosslinked to produce resins and elastomers.[57] Many organosilicon compounds are known which contain a silicon-carbon single bond. Many of these are based on a central tetrahedral silicon atom, and some are optically active when central chirality exists. Long chain polymers containing a silicon backbone are known, such as polydimethysilylene (SiMe 2) n.[58] Polycarbosilane, [(SiMe 2) 2CH 2] n with a backbone containing a repeating -Si-Si-C unit, is a precursor in the production of silicon carbide fibers.

Compounds

See also: Category:Silicon compounds.

PDMS – a silicone compound

Silicon forms binary compounds called silicides with many metallic elements whose properties range from reactive compounds, e.g. magnesium silicide, Mg2Si through high melting refractory compounds such as molybdenum disilicide, MoSi2.[44]

Silicon carbide, SiC (carborundum) is a hard, high melting solid and a well known abrasive. It may also be sintered into a type of high-strength ceramic used in armor.

Silane, SiH4, is a pyrophoric gas with a similar tetrahedral structure to methane, CH4. When pure, it does not react with pure water or dilute acids; however, even small amounts of alkali impurities from the laboratory glass can result in a rapid hydrolysis.[45] There is a range of catenated silicon hydrides that form a homologous series of compounds, Si

nH

2n+2 where n = 2–8 (analogous to the alkanes). These are all readily hydrolyzed and are thermally unstable, particularly the heavier members.[46][47]

Disilenes contain a silicon-silicon double bond (analogous to the alkenes) and are generally highly reactive requiring large substituent groups to stabilize them.[48] A disilyne with a silicon-silicon triple bond was first isolated in 2004; although as the compound is non-linear, the bonding is dissimilar to that in alkynes.[49]

Tetrahalides, SiX4, are formed with all the halogens.[50] Silicon tetrachloride, for example, reacts with water, unlike its carbon analogue, carbon tetrachloride.[51] Silicon dihalides are formed by the high temperature reaction of tetrahalides and silicon; with a structure analogous to a carbene they are reactive compounds. Silicon difluoride condenses to form a polymeric compound, (SiF 2) n.[47]

Early purification techniques

Early silicon purification techniques were based on the fact that if silicon is melted and re-solidified, the last parts of the mass to solidify contain most of the impurities. The earliest method of silicon purification, first described in 1919 and used on a limited basis to make radar components during World War II, involved crushing metallurgical grade silicon and then partially dissolving the silicon powder in an acid. When crushed, the silicon cracked so that the weaker impurity-rich regions were on the outside of the resulting grains of silicon. As a result, the impurity-rich silicon was the first to be dissolved when treated with acid, leaving behind a more pure product.

In zone melting, also called zone refining, the first silicon purification method to be widely used industrially, rods of metallurgical grade silicon are heated to melt at one end. Then, the heater is slowly moved down the length of the rod, keeping a small length of the rod molten as the silicon cools and re-solidifies behind it. Since most impurities tend to remain in the molten region rather than re-solidify, when the process is complete, most of the impurities in the rod will have been moved into the end that was the last to be melted.

This end is then cut off and discarded, and the process repeated if a still higher purity is desired.[42]

Electronic grade

Monocrystalline silicon ingot grown by the Czochralski process

Main article: Monocrystalline silicon

The use of silicon in semiconductor devices demands a much greater purity than afforded by metallurgical grade silicon. Very pure silicon (>99.9%) can be extracted directly from solid silica or other silicon compounds by molten salt electrolysis.[39][40] This method, known as early as 1854[41] (see also FFC Cambridge process), has the potential to directly produce solar-grade silicon without any carbon dioxide emission at much lower energy consumption.

Solar grade silicon cannot be used for microelectronics. To properly control the quantum mechanical properties, the purity of the silicon must be very high. Bulk silicon wafers used at the beginning of the integrated circuit making process must first be refined to a purity of 99.9999999% often referred to as "9N" for "9 nines", a process which requires repeated applications of refining technology.

The majority of silicon crystals grown for device production are produced by the Czochralski process, (Cz-Si) It was the cheapest method available. However, single crystals grown by the Czochralski process contain impurities because the crucible containing the melt often dissolves. Historically, a number of methods have been used to produce ultra-high-purity silicon.

Siemens process and alternatives

The best known technique is the so-called Siemens process. This technique does not require a reductant such as zinc, as it grows high-purity silicon crystallites directly on the surface of (pre-existing) pure silicon seed rods by a chemical decomposition that takes place when the gasous trichlorosilane is blown over the rod's surface at 1150 °C. A common name for this type of technique is chemical vapor deposition (CVD) and produces high-purity polycrystalline silicon, also known as polysilicon. While the conventional Siemens process produces electronic grade polysilicon at typically 9N–11N purities, that is, it contains impurity levels of less than one part per billion (ppb), the modified Siemens process is a dedicated process-route for the production of solar grade silicon (SoG-Si) with purities of 6N (99.9999%) and less energy demand.[34][35][36]

A more recent alternative for the production of polysilicon is the fluidized bed reactor (FBR) manufacturing technology. Compared to the traditional Siemens process, FBR features a number of advantages that lead to cheaper polysilicon demanded by the fast-growing photovoltaic industry. Contrary to Siemens' batch process, FBR runs continuously, wasting fewer resources and requires less setup and downtime. It uses about 10 percent of the electricity consumed by a conventional rod reactor in the established Siemens process, as it does not waste energy by placing heated gas and silicon in contact with cold surfaces. In the FBR, silane (SiH4) is injected into the reactor from below and forms a fluidized bed together with the silicon seed particles that are fed from above. The gaseous silane then decomposes and deposits silicon on the seed particles. When the particles have grown to larger granules, they eventually sink to the bottom of the reactor where they are continuously withdrawn from the process.

The FBR manufacturing technology outputs polysilicon at 6N to 9N, a purity still higher than the 5N to 6N of upgraded metallurgical silicon (UMG-Si), a third technology used by the photovoltaic industry, that dispenses altogether with chemical purification, using metallurgical techniques instead. Currently most silicon for the photovoltaic market is produced by the Siemens process and only about 10 percent by the FBR technology, while UMG-Si accounts for about 2 percent. By 2020, however, IHS Technology predicts that market shares for FBR technology and UMG-Si will grow to 16.7 and 5.4 percent, respectively.[37]

The company REC is one of the leading producers of silane and polysilicon using FBR technology. The three-step chemical reaction involves (last step occurs inside the FB-reactor): (1.) 3 SiCl4 + Si + 2 H2 → 4 HSiCl3, followed by (2.) 4 HSiCl3 → 3 SiCl4 + SiH4, and (3.) SiH4 → Si + 2 H2.[38] Other precursors such as tribromosilane had been used by other companies as well.

QMRUltramafic (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). The Earth's mantle is composed of ultramafic rocks. Ultrabasic is a more inclusive term that includes igneous rocks with low silica content that may not be extremely enriched in Fe and Mg, such as carbonatites and ultrapotassic igneous rocks.

QMRMagma is a complex high-temperature fluid substance. Temperatures of most magmas are in the range 700 °C to 1300 °C (or 1300 °F to 2400 °F), but very rare carbonatite magmas may be as cool as 600 °C, and komatiite magmas may have been as hot as 1600 °C. Most magmas are silicate mixtures.[2]

Characteristics of the four different magma types are as follows:

Ultramafic (picritic)

SiO2 < 45%

Fe–Mg > 8% up to 32%MgO

Temperature: up to 1500°C

Viscosity: Very Low

Eruptive behavior: gentle or very explosive (kimberilites)

Distribution: divergent plate boundaries, hot spots, convergent plate boundaries; komatiite and other ultramafic lavas are mostly Archean and were formed from a higher geothermal gradient and are unknown in the present

Mafic (basaltic)

SiO2 < 50%

FeO and MgO typically < 10 wt%

Temperature: up to ~1300°C

Viscosity: Low

Eruptive behavior: gentle

Distribution: divergent plate boundaries, hot spots, convergent plate boundaries

Intermediate (andesitic)

SiO2 ~ 60%

Fe–Mg: ~ 3%th

Temperature: ~1000°C

Viscosity: Intermediate

Eruptive behavior: explosive or effusive

Distribution: convergent plate boundaries, island arcs

Felsic (rhyolitic)

SiO2 > 70%

Fe–Mg: ~ 2%

Temp: < 900°C

Viscosity: High

Eruptive behavior: explosive or effusive

Distribution: common in hot spots in continental crust (Yellowstone National Park) and in continental rifts

Composition, melt structure and properties[edit]

Silicate melts are composed mainly of silicon, oxygen, aluminium, alkalis (sodium, potassium, calcium), magnesium and iron. Silicon atoms are in tetrahedral coordination with oxygen, as in almost all silicate minerals, but in melts atomic order is preserved only over short distances. The physical behaviours of melts depend upon their atomic structures as well as upon temperature and pressure and composition.[8]

Viscosity is a key melt property in understanding the behaviour of magmas. More silica-rich melts are typically more polymerized, with more linkage of silica tetrahedra, and so are more viscous. Dissolution of water drastically reduces melt viscosity. Higher-temperature melts are less viscous.

Generally speaking, more mafic magmas, such as those that form basalt, are hotter and less viscous than more silica-rich magmas, such as those that form rhyolite. Low viscosity leads to gentler, less explosive eruptions.

Rock types produced by small degrees of partial melting in the Earth's mantle are typically alkaline (Ca, Na), potassic (K) and/or peralkaline (high aluminium to silica ratio). Typically, primitive melts of this composition form lamprophyre, lamproite, kimberlite and sometimes nepheline-bearing mafic rocks such as alkali basalts and essexite gabbros or even carbonatite.

Composition[edit]

It is usually very difficult to change the bulk composition of a large mass of rock, so composition is the basic control on whether a rock will melt at any given temperature and pressure. The composition of a rock may also be considered to include volatile phases such as water and carbon dioxide.

The presence of volatile phases in a rock under pressure can stabilize a melt fraction. The presence of even 0.8% water may reduce the temperature of melting by as much as 100 °C. Conversely, the loss of water and volatiles from a magma may cause it to essentially freeze or solidify. Also a major portion of all magma is silica, which is a compound of silicon and oxygen. Magma also contains gases, which expand as the magma rises. Magma that is high in silica resists flowing, so expanding gases are trapped in it. Pressure builds up until the gases blast out in a violent, dangerous explosion. Magma that is relatively poor in silica flows easily, so gas bubbles move up through it and escape fairly gently. Again silicon has four valence electrons and thus reflects the cross/quadrant.

Analysis using phenocrysts[edit] Geologists use phenocrysts to help determine rock origins and transformations, as when and whether crystals form depends on pressure and on temperature. Fumiko Shido first applied this technique to oceanic basalts,[8] further development came from Tsugio Shibata,[9] and from W. B. Bryan.[10] Other characteristics[edit] Plagioclase phenocrysts often exhibit zoning with a more calcic core surrounded by progressively more sodic rinds. This zoning reflects the change in magma composition as crystallization progresses.[11] In rapakivi granites, phenocrysts of orthoclase are enveloped within rinds of sodic plagioclase such as oligoclase. In shallow intrusives or volcanic flows phenocrysts which formed before eruption or shallow emplacement are surrounded by a fine-grained to glassy matrix. These volcanic phenocrysts often show flow banding, a parallel arrangement of lath-shaped crystals. These characteristics provide clues to the rocks' origins. Similarly, intragranular microfractures and any intergrowth among crystals provide additional clues.[12]

Phenocryst

From Wikipedia, the free encyclopedia

Granites often have large feldspathic phenocrysts. This granite, from the Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coin (diameter 2.3 cm) for scale.

A phenocryst is a relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock. Such rocks that have a distinct difference in the size of the crystals are called porphyries, and the adjective porphyritic is used to describe them. Phenocrysts often have euhedral forms, either due to early growth within a magma, or by post-emplacement recrystallization. Normally the term phenocryst is not used unless the crystals are directly observable, which is sometimes stated as greater than .5 millimeter in diameter.[1] Phenocrysts below this level, but still larger than the groundmass crystals, are termed microphenocrysts. Very large phenocrysts are termed megaphenocrysts. Some rocks contain both microphenocrysts and megaphenocrysts.[2] In metamorphic rocks, crystals similar to phenocrysts are called porphyroblasts.

Phenocrysts are more often found in the lighter (higher silica) igneous rocks such as felsites and andesites, although they occur throughout the igneous spectrum including in the ultramafics. The largest crystals found in some pegmatites are often phenocrysts being significantly larger than the other minerals.

QMRIn petrology the mineral clinopyroxene is used for temperature and pressure calculations of the magma that produced igneous rock containing this mineral. Clinopyroxene thermobarometry is one of several geothermobarometers. Two things makes this method especially useful: first, clinopyroxene is a common phenocryst in igneous rocks and easy to identify; second, the crystallization of the jadeite component of clinopyroxene implies a growth in molar volume being thus a good indicator of pressure. The minerals and liquids involved in clinopyroxene thermobarometry are these four: Augite - (Ca,Mg,Fe)SiO3 Diopside - MgCaSi2O6 Hedenbergite - CaFeSi2O6 Jadeite - Na(Al,Fe3+)Si2O6

Pyroxene minerals[edit]

First X-ray diffraction view of Martian soil - CheMin analysis reveals feldspar, pyroxenes, olivine and more (Curiosity rover at "Rocknest", October 17, 2012).[1]

Clinopyroxenes (monoclinic; abbreviated CPx)

Aegirine (Sodium Iron Silicate)

Augite (Calcium Sodium Magnesium Iron Aluminium Silicate)

Clinoenstatite (Magnesium Silicate)

Diopside (Calcium Magnesium Silicate, CaMgSi2O6)

Esseneite (Calcium Iron Aluminium Silicate)

Hedenbergite (Calcium Iron Silicate)

Jadeite (Sodium Aluminium Silicate)

Jervisite (Sodium Calcium Iron Scandium Magnesium Silicate)

Johannsenite (Calcium Manganese Silicate)

Kanoite (Manganese Magnesium Silicate)

Kosmochlor (Sodium Chromium Silicate)

Namansilite (Sodium Manganese Silicate)

Natalyite (Sodium Vanadium Chromium Silicate)

Omphacite (Calcium Sodium Magnesium Iron Aluminium Silicate)

Petedunnite (Calcium Zinc Manganese Iron Magnesium Silicate)

Pigeonite (Calcium Magnesium Iron Silicate) Spodumene (Lithium Aluminium Silicate) Orthopyroxenes (orthorhombic; abbreviated OPx) Hypersthene (Magnesium Iron Silicate) Donpeacorite, (MgMn)MgSi2O6 Enstatite, Mg2Si2O6 Ferrosilite, Fe2Si2O6 Nchwaningite (Hydrated Manganese Silicate)

Trioctahedral micas[edit]

Common micas:

Biotite

Lepidolite

Muscovite

Phlogopite

Zinnwaldite

Brittle micas:

Clintonite

Interlayer deficient micas[edit]

Very fine-grained micas, which typically show more variation in ion and water content, are informally termed "clay micas". They include:

Hydro-muscovite with H3O+ along with K in the X site;

Illite with a K deficiency in the X site and correspondingly more Si in the Z site;

Phengite with Mg or Fe2+ substituting for Al in the Y site and a corresponding increase in Si in the Z site.

Occurrence and production[edit]

File:Mica.webm

Mica embedded in metamorphic rock

Mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes. Large crystals of mica used for various applications are typically mined from granitic pegmatites.

Until the 19th century, large crystals of mica were quite rare and expensive as a result of the limited supply in Europe. However, their price dramatically dropped when large reserves were found and mined in Africa and South America during the early 19th century. The largest documented single crystal of mica (phlogopite) was found in Lacey Mine, Ontario, Canada; it measured 10 × 4.3 × 4.3 m and weighed about 330 tonnes.[7] Similar-sized crystals were also found in Karelia, Russia.[8]

The British Geological Survey reported that as of 2005, Koderma district in Jharkhand state in India had the largest deposits of mica in the world. China was the top producer of mica with almost a third of the global share, closely followed by the US, South Korea and Canada. Large deposits of sheet mica were mined in New England from the 19th century to the 1970s. Large mines existed in Connecticut, New Hampshire, and Maine.

Scrap and flake mica is produced all over the world. In 2010, the major producers were Russia (100,000 tonnes), Finland (68,000 t), United States (53,000 t), South Korea (50,000 t), France (20,000 t) and Canada (15,000 t). The total production was 350,000 t, although no reliable data were available for China. Most sheet mica was produced in India (3,500 t) and Russia (1,500 t).[9] Flake mica comes from several sources: the metamorphic rock called schist as a byproduct of processing feldspar and kaolin resources, from placer deposits, and from pegmatites. Sheet mica is considerably less abundant than flake and scrap mica, and is occasionally recovered from mining scrap and flake mica. The most important sources of sheet mica are pegmatite deposits. Sheet mica prices vary with grade and can range from less than $1 per kilogram for low-quality mica to more than $2,000 per kilogram for the highest quality.

QMRThe mica group of sheet silicate (phyllosilicate) minerals includes several closely related materials having nearly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition. The nearly perfect cleavage, which is the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms. The word mica is derived from the Latin word mica, meaning a crumb, and probably influenced by micare, to glitter.[5]

QMRThe chain silicate structure of the pyroxenes offers much flexibility in the incorporation of various cations and the names of the pyroxene minerals are primarily defined by their chemical composition. Pyroxene minerals are named according to the chemical species occupying the X (or M2) site, the Y (or M1) site, and the tetrahedral T site. Cations in Y (M1) site are closely bound to 6 oxygens in octahedral coordination. Cations in the X (M2) site can be coordinated with 6 to 8 oxygen atoms, depending on the cation size. Twenty mineral names are recognised by the International Mineralogical Association's Commission on New Minerals and Mineral Names and 105 previously used names have been discarded (Morimoto et al., 1989).

A typical pyroxene has mostly silicon in the tetrahedral site and predominately ions with a charge of +2 in both the X and Y sites, giving the approximate formula XYT2O6. The names of the common calcium – iron – magnesium pyroxenes are defined in the 'pyroxene quadrilateral' shown in Figure 2. The enstatite-ferrosilite series ([Mg,Fe]SiO3) contain up to 5 mol.% calcium and exists in three polymorphs, orthorhombic orthoenstatite and protoenstatite and monoclinic clinoenstatite (and the ferrosilite equivalents). Increasing the calcium content prevents the formation of the orthorhombic phases and pigeonite ([Mg,Fe,Ca][Mg,Fe]Si2O6) only crystallises in the monoclinic system. There is not complete solid solution in calcium content and Mg-Fe-Ca pyroxenes with calcium contents between about 15 and 25 mol.% are not stable with respect to a pair of exolved crystals. This leads to a miscibility gap between pigeonite and augite compositions. There is an arbitrary separation between augite and the diopside-hedenbergite (CaMgSi2O6 – CaFeSi2O6) solid solution. The divide is taken at >45 mol.% Ca. As the calcium ion cannot occupy the Y site, pyroxenes with more than 50 mol.% calcium are not possible. A related mineral wollastonite has the formula of the hypothetical calcium end member but important structural differences mean that it is not grouped with the pyroxenes.

Magnesium, calcium and iron are by no means the only cations that can occupy the X and Y sites in the pyroxene structure. A second important series of pyroxene minerals are the sodium-rich pyroxenes, corresponding to nomenclature shown in Figure 3. The inclusion of sodium, which has a charge of +1, into the pyroxene implies the need for a mechanism to make up the "missing" positive charge. In jadeite and aegirine this is added by the inclusion of a +3 cation (aluminium and iron(III) respectively) on the Y site. Sodium pyroxenes with more than 20 mol.% calcium, magnesium or iron(II) components are known as omphacite and aegirine-augite, with 80% or more of these components the pyroxene falls in the quadrilateral shown in figure 2.

Table 1 shows the wide range of other cations that can be accommodated in the pyroxene structure, and indicates the sites that they occupy.

Table 1: Order of cation occupation in the pyroxenes T Si Al Fe3+ Y Al Fe3+ Ti4+ Cr V Ti3+ Zr Sc Zn Mg Fe2+ Mn X Mg Fe2+ Mn Li Ca Na In assigning ions to sites the basic rule is to work from left to right in this table first assigning all silicon to the T site then filling the site with remaining aluminium and finally iron(III), extra aluminium or iron can be accommodated in the Y site and bulkier ions on the X site. Not all the resulting mechanisms to achieve charge neutrality follow the sodium example above and there are several alternative schemes: Coupled substitutions of 1+ and 3+ ions on the X and Y sites respectively. For example, Na and Al give the jadeite (NaAlSi2O6) composition. Coupled substitution of a 1+ ion on the X site and a mixture of equal numbers of 2+ and 4+ ions on the Y site. This leads to e.g. NaFe2+0.5Ti4+0.5Si2O6. The Tschermak substitution where a 3+ ion occupies the Y site and a T site leading to e.g. CaAlAlSiO6. In nature, more than one substitution may be found in the same mineral.

Tectosilicates[edit]

Main category: Tectosilicates

Tectosilicates, or "framework silicates," have a three-dimensional framework of silicate tetrahedra with SiO2 or a 1:2 ratio. This group comprises nearly 75% of the crust of the Earth. Tectosilicates, with the exception of the quartz group, are aluminosilicates. Nickel-Strunz classification: 09.F and 09.G, 04.DA (Quartz/ silica family)

Quartz

Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). Collected by Apollo 16 from the Lunar Highlands near Descartes Crater.

Quartz group

Quartz - SiO2

Tridymite - SiO2

Cristobalite - SiO2

Coesite - SiO2

Stishovite - SiO2

Feldspar family

Alkali-feldspars (potassium-feldspars)

Microcline - KAlSi3O8

Orthoclase - KAlSi3O8

Anorthoclase - (Na,K)AlSi3O8

Sanidine - KAlSi3O8

Albite - NaAlSi3O8

Plagioclase feldspars

Albite - NaAlSi3O8

Oligoclase - (Na,Ca)(Si,Al)4O8 (Na:Ca 4:1)

Andesine - (Na,Ca)(Si,Al)4O8 (Na:Ca 3:2)

Labradorite - (Na,Ca)(Si,Al)4O8 (Na:Ca 2:3)

Bytownite - (Na,Ca)(Si,Al)4O8 (Na:Ca 1:4)

Anorthite - CaAl2Si2O8

Feldspathoid family

Nosean - Na8Al6Si6O24(SO4)

Cancrinite - Na6Ca2(CO3,Al6Si6O24).2H2O

Leucite - KAlSi2O6

Nepheline - (Na,K)AlSiO4

Sodalite - Na8(AlSiO4)6Cl2

Hauyne - (Na,Ca)4-8Al6Si6(O,S)24(SO4,Cl)1-2

Lazurite - (Na,Ca)8(AlSiO4)6(SO4,S,Cl)2

Petalite - LiAlSi4O10

Scapolite group

Marialite - Na4(AlSi3O8)3(Cl2,CO3,SO4)

Meionite - Ca4(Al2Si2O8)3(Cl2CO3,SO4)

Analcime - NaAlSi2O6•H2O

Zeolite family

Natrolite - Na2Al2Si3O10•2H2O

Erionite - (Na2,K2,Ca)2Al4Si14O36·15H2O Chabazite - CaAl2Si4O12•6H2O Heulandite - CaAl2Si7O18•6H2O Stilbite - NaCa2Al5Si13O36•17H2O Scolecite - CaAl2Si3O10.3H2O Mordenite - (Ca,Na2,K2)Al2Si10O24•7H2O

Phyllosilicates[edit]

Main category: Phyllosilicates

Phyllosilicates (from Greek φύλλον phyllon, leaf), or sheet silicates, form parallel sheets of silicate tetrahedra with Si2O5 or a 2:5 ratio. Nickel-Strunz classification: 09.E. All phyllosilicate minerals are hydrated, with either water or hydroxyl groups attached.

Kaolin

Serpentine group

Antigorite - Mg3Si2O5(OH)4

Chrysotile - Mg3Si2O5(OH)4

Lizardite - Mg3Si2O5(OH)4

Clay mineral group

Halloysite - Al2Si2O5(OH)4

Kaolinite - Al2Si2O5(OH)4

Illite - (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]

Montmorillonite - (Na,Ca)0.33(Al,Mg)2Si4O10(OH)2·nH2O

Vermiculite - (MgFe,Al)3(Al,Si)4O10(OH)2·4H2O

Talc - Mg3Si4O10(OH)2

Sepiolite - Mg4Si6O15(OH)2·6H2O

Palygorskite (or attapulgit)- (Mg,Al)2Si4O10(OH)·4(H2O)

Pyrophyllite - Al2Si4O10(OH)2

Mica group

Biotite - K(Mg,Fe)3(AlSi3)O10(OH)2

Muscovite - KAl2(AlSi3)O10(OH)2

Phlogopite - KMg3(AlSi3)O10(OH)2

Lepidolite - K(Li,Al)2-3(AlSi3)O10(OH)2

Margarite - CaAl2(Al2Si2)O10(OH)2 Glauconite - (K,Na)(Al,Mg,Fe)2(Si,Al)4O10(OH)2 Chlorite group Chlorite - (Mg,Fe)3(Si,Al)4O10(OH)2•(Mg,Fe)3(OH)6

Double chain inosilicates[edit] Amphibole group Anthophyllite - (Mg,Fe)7Si8O22(OH)2 Cumingtonite series Cummingtonite - Fe2Mg5Si8O22(OH)2 Grunerite - Fe7Si8O22(OH)2 Tremolite series Tremolite - Ca2Mg5Si8O22(OH)2 Actinolite - Ca2(Mg,Fe)5Si8O22(OH)2 Hornblende - (Ca,Na)2-3(Mg,Fe,Al)5Si6(Al,Si)2O22(OH)2 Sodium amphibole group Glaucophane - Na2Mg3Al2Si8O22(OH)2 Riebeckite (asbestos) - Na2Fe2+3Fe3+2Si8O22(OH)2 Arfvedsonite - Na3(Fe,Mg)4FeSi8O22(OH)2

Inosilicates[edit] Main category: Inosilicates Inosilicates (from Greek ἴς is [genitive: ἰνός inos], fibre), or chain silicates, have interlocking chains of silicate tetrahedra with either SiO3, 1:3 ratio, for single chains or Si4O11, 4:11 ratio, for double chains. Nickel-Strunz classification: 09.D Single chain inosilicates[edit] Pyroxene group Enstatite - orthoferrosilite series Enstatite - MgSiO3 Ferrosilite - FeSiO3 Pigeonite - Ca0.25(Mg,Fe)1.75Si2O6 Diopside - hedenbergite series Diopside - CaMgSi2O6 Hedenbergite - CaFeSi2O6 Augite - (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6 Sodium pyroxene series Jadeite - NaAlSi2O6 Aegirine (Acmite) - NaFe3+Si2O6 Spodumene - LiAlSi2O6 Pyroxenoid group Wollastonite - CaSiO3 Rhodonite - MnSiO3 Pectolite - NaCa2(Si3O8)(OH)

Cyclosilicates[edit] Cyclosilicate specimens at the Museum of Geology, South Dakota Main category: Cyclosilicates Cyclosilicates (from Greek κύκλος kuklos, circle), or ring silicates, have linked tetrahedra with (TxO3x)2x− or a ratio of 1:3. These exist as 3-member (T3O9)6− and 6-member (T6O18)12− rings, where T stands for a tetrahedrally coordinated cation. Nickel-Strunz classification: 09.C 3-member ring Benitoite - BaTi(Si3O9) 6-member ring Axinite - (Ca,Fe,Mn)3Al2(BO3)(Si4O12)(OH) Beryl/Emerald - Be3Al2(Si6O18) Sugilite - KNa2(Fe,Mn,Al)2Li3Si12O30 Cordierite - (Mg,Fe)2Al3(Si5AlO18) Tourmaline - (Na,Ca)(Al,Li,Mg)3-(Al,Fe,Mn)6(Si6O18(BO3)3(OH)4 Note that the ring in axinite contains two B and four Si tetrahedra and is highly distorted compared to the other 6-member ring cyclosilicates.

Sorosilicates[edit] Sorosilicate exhibit at Museum of Geology in South Dakota Main category: Sorosilicates Sorosilicates (from Greek σωρός sōros, heap, mound) have isolated double tetrahedra groups with (Si2O7)6− or a ratio of 2:7. Nickel-Strunz classification: 09.B Hemimorphite (calamine) - Zn4(Si2O7)(OH)2·H2O Lawsonite - CaAl2(Si2O7)(OH)2·H2O Ilvaite - CaFe2+2Fe3+O(Si2O7)(OH) Epidote group (has both (SiO4)4− and (Si2O7)6− groups) Epidote - Ca2(Al,Fe)3O(SiO4)(Si2O7)(OH) Zoisite - Ca2Al3O(SiO4)(Si2O7)(OH) Clinozoisite - Ca2Al3O(SiO4)(Si2O7)(OH) Tanzanite - Ca2Al3O(SiO4)(Si2O7)(OH) Allanite - Ca(Ce,La,Y,Ca)Al2(Fe2+,Fe3+)O(SiO4)(Si2O7)(OH) Dollaseite-(Ce) - CaCeMg2AlSi3O11F(OH) Vesuvianite (idocrase) - Ca10(Mg,Fe)2Al4(SiO4)5(Si2O7)2(OH)4

Nesosilicates or orthosilicates[edit]

Basic (ortho-)silicate anion structure

Nesosilicate specimens at the Museum of Geology in South Dakota

Main category: Nesosilicates

Nesosilicates (from Greek νησος nēsos, island), or orthosilicates, have the orthosilicate ion, which constitute isolated (insular) [SiO4]4− tetrahedra that are connected only by interstitial cations. Nickel-Strunz classification: 09.A

Phenakite group

Phenakite - Be2SiO4

Willemite - Zn2SiO4

Olivine group

Forsterite - Mg2SiO4

Fayalite - Fe2SiO4

Tephroite - Mn2SiO4

Garnet group

Pyrope - Mg3Al2(SiO4)3

Almandine - Fe3Al2(SiO4)3

Spessartine - Mn3Al2(SiO4)3

Grossular - Ca3Al2(SiO4)3

Andradite - Ca3Fe2(SiO4)3

Uvarovite - Ca3Cr2(SiO4)3

Hydrogrossular - Ca3Al2Si2O8(SiO4)3-m(OH)4m Zircon group Zircon - ZrSiO4 Thorite - (Th,U)SiO4 Kyanite crystals (unknown scale) Al2SiO5 group Andalusite - Al2SiO5 Kyanite - Al2SiO5 Sillimanite - Al2SiO5 Dumortierite - Al6.5-7BO3(SiO4)3(O,OH)3 Topaz - Al2SiO4(F,OH)2 Staurolite - Fe2Al9(SiO4)4(O,OH)2 Humite group - (Mg,Fe)7(SiO4)3(F,OH)2 Norbergite - Mg3(SiO4)(F,OH)2 Chondrodite - Mg5(SiO4)2(F,OH)2 Humite - Mg7(SiO4)3(F,OH)2 Clinohumite - Mg9(SiO4)4(F,OH)2 Datolite - CaBSiO4(OH) Titanite - CaTiSiO5 Chloritoid - (Fe,Mg,Mn)2Al4Si2O10(OH)4 Mullite (aka Porcelainite) - Al6Si2O13

QMRSilicate minerals From Wikipedia, the free encyclopedia (Redirected from Tectosilicate) Silicate minerals Chrysocolla.jpg Copper silicate mineral chrysocolla Category Mineral "Orthosilicate" redirects here. For anion, see Orthosilicate (ion). The silicate minerals are rock-forming minerals, constituting approximately 90 percent of the crust of the Earth. They are classified based on the structure of their silicate group which contain different ratios of silicon and oxygen. They make up the largest and most important class of rock-forming minerals.

Memnonia quadrangle

From Wikipedia, the free encyclopedia

Memnonia quadrangle

USGS-Mars-MC-16-MemnoniaRegion-mola.png

Map of Memnonia quadrangle from Mars Orbiter Laser Altimeter (MOLA) data. The highest elevations are red and the lowest are blue.

Coordinates 15°S 157.5°WCoordinates: 15°S 157.5°W

Image of the Memnonia Quadrangle (MC-16). The south includes heavily cratered highlands intersected, in the northeastern part, by Mangala Vallis. The north contains undulating wind-eroded deposits and the east contains lava flows from the Tharsis region.

The Memnonia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Memnonia quadrangle is also referred to as MC-16 (Mars Chart-16).[1]

The quadrangle is a region of Mars that covers latitude -30° to 0° and longitude 135° to 180°.[2] The western part of Memnonia is a highly cratered highland region that exhibits a large range of crater degradation.

Memnonia includes these topographical regions of Mars: Arcadia Planitia Amazonis Planitia Lucus Planum Terra Sirenum Daedalia Planum Terra Cimmeria Recently, evidence of water was found in the area. Layered sedimentary rocks were found in the wall and floor of Columbus Crater. These rocks could have been deposited by water or by wind. Hydrated minerals were found in some of the layers, so water may have been involved.[3] Many ancient river valleys Vallis including Mangala Vallis, have been found in the Memnonia quadrangle. Mangala appears to have begun with the formation of a graben, a set of faults that may have exposed an aquifer.[4] Dark slope streaks and troughts (fossae) are present in this quadrangle. Part of the Medusae Fossae Formation is found in the Memnonia quadrangle.

QMRThe Elysium quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Elysium quadrangle is also referred to as MC-15 (Mars Chart-15).[1] The Elysium quadrangle covers the area 180° to 225° west longitude and 0° to 30° north latitude on Mars. Elysium Planitia is in the Elysium quadrangle. The Elysium quadrangle includes a part of Lucus Planum. A small part of the Medusae Fossae Formation lies in this quadrangle. The largest craters in this quadrangle are Eddie, Lockyer, and Tombaugh. Elysium contains major volcanoes named Elysium Mons and Albor Tholus and river valleys—one of which, Athabasca Valles may be one of the youngest on Mars. On the east side is an elongated depression called Orcus Patera. A large lake may once have existed in the south near Lethe Valles and Athabasca Valles.[2]

QMRClay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay minerals form in the presence of water[1] and have been important to life, and many theories of abiogenesis involve them. They have been useful to humans since ancient times in agriculture and manufacturing. silicate means clay contains silicon. Again silicon is shaped as a quadrant. In the Bible it says that man was made from clay

Barium feldspars[edit] Barium feldspars are also considered alkali feldspars. Barium feldspars form as the result of the substitution of barium for potassium in the mineral structure. The barium feldspars are monoclinic and include the following: celsian—BaAl2Si2O8[11] hyalophane—(K,Ba)(Al,Si)4O8[12] Plagioclase feldspars[edit] The plagioclase feldspars are triclinic. The plagioclase series follows (with percent anorthite in parentheses): albite (0 to 10)—NaAlSi3O8 oligoclase (10 to 30)—(Na,Ca)(Al,Si)AlSi2O8 andesine (30 to 50)—NaAlSi3O8—CaAl2Si2O8 labradorite (50 to 70)—(Ca,Na)Al(Al,Si)Si2O8 bytownite (70 to 90)—(NaSi,CaAl)AlSi2O8 anorthite (90 to 100)—CaAl2Si2O8 Intermediate compositions of plagioclase feldspar also may exsolve to two feldspars of contrasting composition during cooling, but diffusion is much slower than in alkali feldspar, and the resulting two-feldspar intergrowths typically are too fine-grained to be visible with optical microscopes. The immiscibility gaps in the plagioclase solid solutions are complex compared to the gap in the alkali feldspars. The play of colours visible in some feldspar of labradorite composition is due to very fine-grained exsolution lamellae.

Compositions[edit]

This group of minerals consists of framework tectosilicates. Compositions of major elements in common feldspars can be expressed in terms of three endmembers:

Potassium-Feldspar (K-spar) endmember KAlSi3O8[2]

Albite endmember NaAlSi3O8[2]

Anorthite endmember CaAl2Si2O8[2]

Solid solutions between K-feldspar and albite are called alkali feldspar.[2] Solid solutions between albite and anorthite are called plagioclase,[2] or more properly plagioclase feldspar. Only limited solid solution occurs between K-feldspar and anorthite, and in the two other solid solutions, immiscibility occurs at temperatures common in the crust of the earth. Albite is considered both a plagioclase and alkali feldspar.

Alkali feldspars[edit]

The alkali feldspars are as follows:

orthoclase (monoclinic)[7]—KAlSi3O8 sanidine (monoclinic)[8]—(K,Na)AlSi3O8 microcline (triclinic)[9]—KAlSi3O8 anorthoclase (triclinic)—(Na,K)AlSi3O8 Sanidine is stable at the highest temperatures, and microcline at the lowest.[7][8] Perthite is a typical texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. The perthitic textures in the alkali feldspars of many granites can be seen with the naked eye.[10] Microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope.

QMRFeldspars (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) are a group of rock-forming tectosilicate minerals that make up as much as 60% of the Earth's crust.[2] Feldspars crystallize from magma as veins in both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock.[3] Rock formed almost entirely of calcic plagioclase feldspar (see below) is known as anorthosite.[4] Feldspars are also found in many types of sedimentary rocks.[5]

QMR A QAPF diagram is a double triangle diagram which is used to classify igneous rocks based on mineralogic composition. The acronym, QAPF, stands for "Quartz, Alkali feldspar, Plagioclase, Feldspathoid (Foid)". These are the four mineral groups used for classification in QAPF diagram. Q, A, P and F percentages are normalized (recalculated so that their sum is 100%).

Granitoids are a ubiquitous component of the crust. They have crystallized from magmas that have compositions at or near a eutectic point (or a temperature minimum on a cotectic curve). Magmas will evolve to the eutectic because of igneous differentiation, or because they represent low degrees of partial melting. Fractional crystallisation serves to reduce a melt in iron, magnesium, titanium, calcium and sodium, and enrich the melt in potassium and silicon – alkali feldspar (rich in potassium) and quartz (SiO2), are two of the defining constituents of granite. This process operates regardless of the origin of the parental magma to the granite, and regardless of its chemistry. However, the composition and origin of the magma that differentiates into granite leaves certain geochemical and mineral evidence as to what the granite's parental rock was. The final mineralogy, texture and chemical composition of a granite is often distinctive as to its origin. For instance, a granite that is formed from melted sediments may have more alkali feldspar, whereas a granite derived from melted basalt may be richer in plagioclase feldspar. It is on this basis that the modern "alphabet" classification schemes are based. Granite has a slow cooling process which forms larger crystals.

SiO2 72.04% (silica) Al2O3 14.42% (alumina) K2O 4.12% Na2O 3.69% CaO 1.82% FeO 1.68% Fe2O3 1.22% MgO 0.71% TiO2 0.30% P2O5 0.12% MnO 0.05%

QMRThe term "granitic" means granite-like and is applied to granite and a group of intrusive igneous rocks with similar textures and slight variations in composition and origin. These rocks mainly consist of feldspar, quartz, mica, and amphibole minerals, which form an interlocking, somewhat equigranular matrix of feldspar and quartz with scattered darker biotite mica and amphibole (often hornblende) peppering the lighter color minerals. Occasionally some individual crystals (phenocrysts) are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic texture is known as a granite porphyry. Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks. Petrographic examination is required for identification of specific types of granitoids.[1]

QMRLechatelierite

From Wikipedia, the free encyclopedia

Lechatelierite created by high voltage power line arcing on rocky soil.

Lechatelierite is silica glass, amorphous SiO2. One common way in which lechatelierite forms naturally is by very high temperature melting of quartz sand during a lightning strike. The result is an irregular, branching, often foamy hollow tube of silica glass called a fulgurite.[1]

Lechatelierite also forms as the result of high pressure shock metamorphism during meteorite impact cratering and is a common component of a type of glassy ejecta called tektites. Most tektites are blobs of impure glassy material, but tektites from the Sahara Desert in Libya and Egypt, known as Libyan desert glass, are composed of almost pure silica, that is almost pure lechatelierite.[2] High pressure experiments have shown that shock pressures of 85 GPa are needed to produce lechatelierite in quartz grains embedded in granite.[3]

Lechatelierite was formed during the impact of a meteorite into a layer of Coconino Sandstone at Meteor Crater in Arizona. During the rapid pressure reduction following the impact, steam expanded the newly formed lechatelierite. The shattered and expanded glass has a density less than that of water.[4]

Lechatelierite may also form artificially, a unique example being the trinitite produced by melting of quartz sand at the first nuclear bomb explosion at Trinity Flats, White Sands, New Mexico.[5] Lechatelierite is a mineraloid as it does not have a crystal structure. Although not a true mineral, it is often classified in the quartz mineral group.

QMRHydrothermal breccia in the Cloghleagh Iron Mine, near Blessington in Ireland, composed mainly of quartz and manganese oxides, the result of seismic activity about 12 million years ago

Discovery[edit] Shocked quartz was discovered after underground nuclear bomb testing, which caused the intense pressures required to form shocked quartz. Eugene Shoemaker showed that shocked quartz is also found inside craters created by meteor impact, such as the Barringer Crater and Chicxulub crater.[1] The presence of shocked quartz proves that these craters were formed by an impact: a volcano would not generate the pressure required. Prevalence[edit] Shocked quartz is found worldwide, in the thin Cretaceous–Paleogene boundary layer, which occurs at the contact between Cretaceous and Paleogene rocks. This is further evidence (in addition to iridium enrichment) that the transition between the two geological periods was caused by a large impact. Though shocked quartz is only recently recognized, Eugene Shoemaker discovered it in building stones in the Bavarian town of Nördlingen.[2

QMRShocked quartz From Wikipedia, the free encyclopedia Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure (but limited temperature), the crystalline structure of quartz will be deformed along planes inside the crystal. These planes, which show up as lines under a microscope, are called planar deformation features (PDFs), or shock lamellae.

Vycor products are made by a multi-step process. First, a relatively soft alkali-borosilicate glass is melted and formed by typical glassworking techniques into the desired shape. This is heat-treated, which causes the material to separate into two intermingled "phases" with distinct chemical compositions. One phase is rich in alkali and boric oxide, and can be easily dissolved in acid. The other phase is mostly silica, which is insoluble. The glass object is then soaked in a hot acid solution, which leaches away the soluble glass phase, leaving an object which is mostly silica. At this stage, the glass is porous. Finally, the object is heated to more than 1200°C, which consolidates the porous structure, making the object shrink slightly and become non-porous. The finished material is classified as a "reconstructed glass".

For some applications the final step is skipped, leaving the glass porous. Such glass has a high affinity for water, and makes an excellent getter for water vapour. It is widely used in science and engineering.

Vycor has an extremely low coefficient of thermal expansion, just one quarter that of Pyrex.[1] This property makes the material suitable for use in applications which demand very-high-dimensional stability, such as metrology instruments, and for products that need to withstand high thermal shock loads. Immersing the porous glass in certain chemical solutions before the final consolidation step produces a colored glass that can withstand high temperatures without degrading. This is used for colored glass filters for various applications. Corning manufactures Vycor products for high-temperature applications, such as evaporating dishes. Porous vycor is a prototypical matrix material for the study of confined liquid physics.

QMRVycor is the brand name of Corning's high silica, high temperature glass. It provides very high thermal shock resistance. Vycor is approximately 96% silica and 4% boron trioxide, but unlike pure fused silica it can be readily manufactured in a variety of shapes

The optical dispersion of fused silica can be approximated by the following Sellmeier equation:[5] \varepsilon=n^2=1+\frac{0.6961663\lambda^2}{\lambda^2-0.0684043^2}+\frac{0.4079426\lambda^2}{\lambda^2-0.1162414^2}+\frac{0.8974794\lambda^2}{\lambda^2-9.896161^2}, where the wavelength \lambda is measured in micrometers. This equation is valid between 0.21 and 3.71 micrometers and at 20 °C.[5] Its validity was confirmed for wavelengths up to 6.7 µm.[6] Experimental data for the real (refractive index) and imaginary (absorption index) parts of the complex refractive index of fused quartz reported in the literature over the spectral range from 30 nm to 1000 µm has been reviewed by Kitamura et al.[6] and are available online.

Physical properties[edit]

The extremely low coefficient of thermal expansion, about 5.5×10−7/°C (20–320 °C), accounts for its remarkable ability to undergo large, rapid temperature changes without cracking (see thermal shock).

Phosphorescence in fused quartz from an extremely intense pulse of ultraviolet light, centered at 170 nm, in a flashtube.

Fused quartz is prone to phosphorescence and "solarisation" (purplish discoloration) under intense UV illumination, as is often seen in flashtubes. "UV grade" synthetic fused silica (sold under various tradenames including "HPFS", "Spectrosil" and "Suprasil") has a very low metallic impurity content making it transparent deeper into the ultraviolet. An optic with a thickness of 1 cm will have a transmittance of about 50% at a wavelength of 170 nm, which drops to only a few percent at 160 nm. However, its infrared transmission is limited by strong water absorptions at 2.2 μm and 2.7 μm.

"Infrared grade" fused quartz (tradenames "Infrasil", "Vitreosil IR" and others) which is electrically fused, has a greater presence of metallic impurities, limiting its UV transmittance wavelength to around 250 nm, but a much lower water content, leading to excellent infrared transmission up to 3.6 μm wavelength. All grades of transparent fused quartz/fused silica have nearly identical physical properties.

Refractory material applications[edit]

Fused silica as an industrial raw material is used to make various refractory shapes such as crucibles, trays, shrouds, and rollers for many high-temperature thermal processes including steelmaking, investment casting, and glass manufacture. Refractory shapes made from fused silica have excellent thermal shock resistance and are chemically inert to most elements and compounds including virtually all acids, regardless of concentration, except hydrofluoric acid which is very reactive even in fairly low concentrations. Translucent fused silica tubes are commonly used to sheathe electric elements in room heaters, industrial furnaces and other similar applications.

Owing to its low mechanical damping at ordinary temperatures, it is used for high-Q resonators, in particular, for wine-glass resonator of hemispherical resonator gyro (HRG).[3][4] Quartz glassware is occasionally used in chemistry laboratories when standard borosilicate glass cannot withstand high temperatures; it is more commonly found as a very basic element, such as a tube in a furnace, or as a flask, the elements in direct exposure to the heat.

Applications[edit]

Most of the applications of fused silica exploit its wide transparency range, which extends from the UV to the near IR. Fused silica is the key starting material for optical fiber, used for telecommunications.

Because of its strength and high melting point (compared to ordinary glass), fused silica is used as an envelope for halogen lamps and high-intensity discharge lamps, which must operate at a high envelope temperature to achieve their combination of high brightness and long life. Vacuum tubes with silica envelopes allowed for radiation-cooling by incandescent anodes.

Because of its strength fused silica was used in deep diving vessels such as the Bathysphere and Benthoscope.

The combination of strength, thermal stability, and UV transparency makes it an excellent substrate for projection masks for photolithography.

An EPROM with fused quartz window in the top of the package

Its UV transparency also finds uses in the semiconductor industry; an EPROM, or erasable programmable read only memory, is a type of memory chip that retains its data when its power supply is switched off, but which can be erased by exposure to strong ultraviolet light. EPROMs are recognizable by the transparent fused quartz window which sits on top of the package, through which the silicon chip is visible, and which permits exposure to UV light during erasing.

Due to the thermal stability and composition it is used in semiconductor fabrication furnaces. Fused quartz has nearly ideal properties for fabricating first surface mirrors such as those used in telescopes. The material behaves in a predictable way and allows the optical fabricator to put a very smooth polish onto the surface and produce the desired figure with fewer testing iterations. In some instances, a high-purity UV grade of fused quartz has been used to make several of the individual uncoated lens elements of special purpose lenses including the Zeiss 105mm f/4.3 UV Sonnar, a lens formerly made for the Hasselblad camera, and the Nikon UV-Nikkor 105mm f/4.5 (presently sold[clarification needed] as the Nikon PF10545MF-UV) lens. These lenses are used for UV photography, as the quartz glass has a lower extinction rate than lens made with more common flint or crown glass formulas. Fused quartz is also the material used for modern glass instruments such as the glass harp and the verrophone, and is also used for new builds of the historical glass harmonica. Here, the superior strength and structure of fused quartz gives it a greater dynamic range than the historically used lead crystal, and a clearer sound.

Feedstock[edit]

Fused quartz is produced by fusing (melting) high-purity silica sand, which consists of quartz crystals. Quartz contains only silicon and oxygen, although commercial quartz glass often contains impurities. The most dominant impurities are aluminium and titanium.[2]

Fusion[edit]

Melting is effected at approximately 2000 °C using either an electrically heated furnace (electrically fused) or a gas/oxygen-fuelled furnace (flame fused). Fused silica can be made from almost any silicon-rich chemical precursor, usually using a continuous process which involves flame oxidation of volatile silicon compounds to silicon dioxide, and thermal fusion of the resulting dust (although there are alternative processes). This results in a transparent glass with an ultra-high purity and improved optical transmission in the deep ultraviolet. One common method involves adding silicon tetrachloride to a hydrogen–oxygen flame, however use of this precursor results in environmentally unfriendly by-products including chlorine and hydrochloric acid. To eliminate these by-products, new processes have been developed using an alternative feedstock,[which?] which has also resulted in a higher purity fused silica with further improved deep ultraviolet transmission.[citation needed]

Product quality[edit] Fused quartz is normally transparent, the process of fusion results in a material that is translucent. The material can however appear opaque owing to the presence small air bubbles trapped within the material. The water content (and therefore infrared transmission of fused quartz and fused silica) is determined by the manufacturing process. Flame fused material always has a higher water content due to the combination of the hydrocarbons and oxygen fuelling the furnace forming hydroxyl [OH] groups within the material. An IR grade material typically has an [OH] content of <10 parts per million.

QMR Recall quartz is made of silicon. Silicon is called the miracle element. It is shaped as a quadrant. Like carbon, which also has four valence electrons and is shaped as a quadrant, silicon is very important. Fused quartz or fused silica is glass consisting of silica in amorphous (non-crystalline) form. It differs from traditional glasses in containing no other ingredients, which are typically added to glass to lower the melt temperature. Fused silica, therefore, has high working and melting temperatures. The optical and thermal properties of fused quartz are superior to those of other types of glass due to its purity. For these reasons, it finds use in situations such as semiconductor fabrication and laboratory equipment. It has better ultraviolet transmission than most other glasses, and so is used to make lenses and other optics for the ultraviolet spectrum. Its low coefficient of thermal expansion also makes it a useful material for precision mirror substrates.[1]

QMRBiasing resistor[edit] R1 acts as a feedback resistor, biasing the inverter in its linear region of operation and effectively causing it to function as a high gain inverting amplifier. To see this, assume the inverter is ideal, with infinite input impedance and zero output impedance. The resistor forces the input and output voltages to be equal. Hence the inverter will neither be fully on nor fully off, but will operate in the transition region where it has gain. Resonator[edit] Extremely low cost applications sometimes use a piezoelectric PZT crystal ceramic resonator rather than a piezoelectric quartz crystal resonator. The crystal in combination with C1 and C2 forms a pi network band-pass filter, which provides a 180 degree phase shift and a voltage gain from the output to input at approximately the resonant frequency of the crystal. To understand the operation, note that at the frequency of oscillation, the crystal appears inductive. Thus, the crystal can be considered a large, high Q inductor. The combination of the 180 degree phase shift (i.e. inverting gain) from the pi network, and the negative gain from the inverter, results in a positive loop gain (positive feedback), making the bias point set by R1 unstable and leading to oscillation.

QMRhttps://www.youtube.com/watch?v=b1ujLaXGSlY Beyonce's twerk dance happens four moves by four moves.

Metallurgical aspects[edit] The silicon content limits the solubility of zinc in copper in the α-phase. In the given alloy the maximum amount of silicon at a very high zinc content is added. The consequence is that the α-phase crystallized silicon supersaturated when it comes to high cooling rates of the alloy. As a result the α-solid solution does not disintegrate, which leads to the described high mechanical properties.

General properties[edit] The silicon content leads to a strengthening of the metal matrix. The appearance is similar to ordinary brass. Silicon tombac has good friction bearing characteristics and is corrosion resistant but is not resistant to ammonia atmosphere. The strength properties are largely retained at application temperatures up to 200 °C.[1] It is a special alloy in terms of the combination of casting process and casting temperature. In most cases, parts made of silicon tombac, are produced through the high pressure die casting process, which is normally specialized on metals with relatively low melting temperatures. But in this case the temperature melting range of silicon tombac is in the area of 950 to 1000 °C, which is relatively high for casting into permanent moulds. The advantage is the productivity of this highly automated casting process. The disadvantage is the temperature stress of the surface of the permanent mould, so that the lifetime of these moulds is limited. Comparison to investment cast steel parts[edit] High pressure die cast Silicon tombac is often used as an alternative for investment cast steel parts, because the mechanical strength is comparable (500 MPa [1]), but the production process is more efficient. There can be found a break-even-point when comparing both processes, whereas the advantages of high pressure die casting regularly predominate at high unit numbers (for instance greater than 5000 units [2]) to produce. This alloy has outstanding casting properties and good strength properties,[3] which is required for the die casting process. It is often chosen for small to medium size parts in terms of casting metal volume. For large parts often investment casting of steels is applied because of the lower material cost.

QMRSilicon tombac From Wikipedia, the free encyclopedia Silicon tombac (German word origin: Siliziumtombak) is an alloy made of copper (80%), zinc (16%) and silicon (4%). Silicon tombac From Wikipedia, the free encyclopedia Silicon tombac (German word origin: Siliziumtombak) is an alloy made of copper (80%), zinc (16%) and silicon (4%).

Nanopores[edit]

When a mix of copper nitrate, phosphorous acid, hydrogen fluoride and water are applied to a silicon wafer, the phosphorous acid reduction reduces the copper ions to copper nanoparticles. The nanoparticles attract electrons from the wafer’s surface, oxidizing it and allowing the hydrogen fluoride to burn inverted pyramid-shaped nanopores into the silicon. The process produced pores as small as 590 nm that let through more than 99% of light.[20]

Function[edit]

When the material is biased by a small electric voltage, absorbed photons are able to excite dozens of electrons. The sensitivity of black silicon detectors is 100–500 times higher than that of untreated silicon (conventional silicon), in both the visible and infrared spectra.[21][22]

A group at the National Renewable Energy Laboratory reported black silicon solar cells with 18.2% efficiency.[14] This black silicon anti-reflective surface was formed by a metal-assisted etch process using nano particles of silver. In May 2015, researchers from Finland's Aalto University, working with researchers from Universitat Politècnica de Catalunya announced they had created black silicon solar cells with 22.1% efficiency[23][24] by applying a thin passivating film on the nanostructures by Atomic Layer Deposition, and by integrating all metal contacts on the back side of the cell.

A team led by Elena Ivanova at Swinburne University of Technology in Melbourne discovered in 2012[25] that cicada wings were potent killers of Pseudomonas aeruginosa, an opportunist germ that also infects humans and is becoming resistant to antibiotics. The effect came from regularly-spaced "nanopillars" on which bacteria were sliced to shreds as they settled on the surface. Both cicada wings and black silicon were put through their paces in a lab, and both were bactericidal. Smooth to human touch, the surfaces destroyed Gram-negative and Gram-positive bacteria, as well as bacterial spores. The three targeted bacterial species P. aeruginosa, Staphylococcus aureus and Bacillus subtilis, a wide-ranging soil germ that is a cousin of anthrax. The killing rate was 450,000 bacteria per square centimetre per minute over the first three hours of exposure or 810 times the minimum dose needed to infect a person with S. aureus, and 77,400 times that of P. aeruginosa.

Steel production[edit]

Piece of silicon carbide used in steel making

Silicon carbide, dissolved in a basic oxygen furnace used for making steel, acts as a fuel. The additional energy liberated allows the furnace to process more scrap with the same charge of hot metal. It can also be used to raise tap temperatures and adjust the carbon and silicon content. Silicon carbide is cheaper than a combination of ferrosilicon and carbon, produces cleaner steel and less emissions due to low levels of trace elements, has a low gas content, and does not lower the temperature of steel.[64]

Catalyst support[edit]

The natural resistance to oxidation exhibited by silicon carbide, as well as the discovery of new ways to synthesize the cubic β-SiC form, with its larger surface area, has led to significant interest in its use as a heterogeneous catalyst support. This form has already been employed as a catalyst support for the oxidation of hydrocarbons, such as n-butane, to maleic anhydride.[65][66]

Carborundum printmaking[edit]

Silicon carbide is used in carborundum printmaking – a collagraph printmaking technique. Carborundum grit is applied in a paste to the surface of an aluminium plate. When the paste is dry, ink is applied and trapped in its granular surface, then wiped from the bare areas of the plate. The ink plate is then printed onto paper in a rolling-bed press used for intaglio printmaking. The result is a print of painted marks embossed into the paper.[67]

Graphene production[edit] Silicon carbide is used to produce epitaxial graphene by graphitization at high temperatures. This is considered as one of the promising methods to synthesize graphene at large scale for practical applications.[68][69] See

Nuclear fuel cladding[edit] Silicon carbide composite material has been investigated for use as a replacement for Zircaloy cladding in light water reactors. The composite consists of SiC fibers wrapped around a SiC inner layer and surrounded by an SiC outer layer.[60] Problems have been reported with the ability to join the pieces of the SiC composite.[61] Jewelry[edit] A moissanite engagement ring As a gemstone used in jewelry, silicon carbide is called "synthetic moissanite" or just "moissanite" after the mineral name. Moissanite is similar to diamond in several important respects: it is transparent and hard (9–9.5 on the Mohs scale, compared to 10 for diamond), with a refractive index between 2.65 and 2.69 (compared to 2.42 for diamond). Moissanite is somewhat harder than common cubic zirconia. Unlike diamond, moissanite can be strongly birefringent. For this reason, moissanite jewels are cut along the optic axis of the crystal to minimize birefringent effects. It is lighter (density 3.21 g/cm3 vs. 3.53 g/cm3), and much more resistant to heat than diamond. This results in a stone of higher luster, sharper facets and good resilience. Loose moissanite stones may be placed directly into wax ring moulds for lost-wax casting, as can diamond,[62] as moissanite remains undamaged by temperatures up to 1800 °C. Moissanite has become popular as a diamond substitute, and may be misidentified as diamond, since its thermal conductivity is closer to diamond than any other substitute. Many thermal diamond-testing devices cannot distinguish moissanite from diamond, but the gem is distinct in its birefringence and a very slight green or yellow fluorescence under ultraviolet light. Some moissanite stones also have curved, string-like inclusions, which diamonds never have.[63]

Thin filament pyrometry[edit]

Main article: Thin filament pyrometry

Image of the test flame and glowing SiC fibers. The flame is about 7 cm tall.

Silicon carbide fibers are used to measure gas temperatures in an optical technique called thin filament pyrometry. It involves the placement of a thin filament in a hot gas stream. Radiative emissions from the filament can be correlated with filament temperature. Filaments are SiC fibers with a diameter of 15 micrometers, about one fifth that of a human hair. Because the fibers are so thin, they do little to disturb the flame and their temperature remains close to that of the local gas. Temperatures of about 800–2500 K can be measured.[56][57]

Heating elements[edit]

References to silicon carbide heating elements exist from the early 20th century when they were produced by Acheson's Carborundum Co. in the U.S. and EKL in Berlin. Silicon carbide offered increased operating temperatures compared with metallic heaters. Silicon carbide elements are used today in the melting of glass and non-ferrous metal, heat treatment of metals, float glass production, production of ceramics and electronics components, igniters in pilot lights for gas heaters, etc.[58]

Nuclear fuel particles[edit] Silicon carbide is an important material in TRISO-coated fuel particles, the type of nuclear fuel found in high temperature gas cooled reactors such as the Pebble Bed Reactor. A layer of silicon carbide gives coated fuel particles structural support and is the main diffusion barrier to the release of fission products.

LEDs[edit] The phenomenon of electroluminescence was discovered in 1907 using silicon carbide and the first commercial LEDs were again based on SiC. Yellow LEDs made from 3C-SiC were manufactured in the Soviet Union in the 1970s[52] and blue ones (6H-SiC) worldwide in the 1980s.[53] The production was soon stopped because gallium nitride showed 10–100 times brighter emission. This difference in efficiency is due to the unfavorable indirect bandgap of SiC, whereas GaN has a direct bandgap which favors light emission. However, SiC is still one of the important LED components – it is a popular substrate for growing GaN devices, and it also serves as a heat spreader in high-power LEDs.[53] Astronomy[edit] The low thermal expansion coefficient, high hardness, rigidity and thermal conductivity make silicon carbide a desirable mirror material for astronomical telescopes. The growth technology (chemical vapor deposition) has been scaled up to produce disks of polycrystalline silicon carbide up to 3.5 meters in diameter, and several telescopes like the Herschel Space Telescope are already equipped with SiC optics.[54][55]

Electronic circuit elements[edit]

Ultraviolet LED

Power electronic devices[edit]

Silicon carbide is a semiconductor in research and early mass-production providing advantages for fast, high-temperature and/or high-voltage devices. The first devices available were Schottky diodes, followed by junction-gate FETs and MOSFETs for high-power switching. Bipolar transistors and thyristors are currently developed.[31] A major problem for SiC commercialization has been the elimination of defects: edge dislocations, screw dislocations (both hollow and closed core), triangular defects and basal plane dislocations.[45] As a result, devices made of SiC crystals initially displayed poor reverse blocking performance though researchers have been tentatively finding solutions to improve the breakdown performance.[46] Apart from crystal quality, problems with the interface of SiC with silicon dioxide have hampered the development of SiC-based power MOSFETs and insulated-gate bipolar transistors. Although the mechanism is still unclear, nitridation has dramatically reduced the defects causing the interface problems.[47] In 2008, the first commercial JFETs rated at 1200 V were introduced to the market,[48] followed in 2011 by the first commercial MOSFETs rated at 1200 V. Beside SiC switches and SiC Schottky diodes (also Schottky barrier diode, SBD) in the popular TO-247 and TO-220 packages, companies started even earlier to implement the bare chips into their power electronic modules. SiC SBD diodes found wide market spread being used in PFC circuits and IGBT power modules.[49] Conferences such as the International Conference on Integrated Power Electronics Systems (CIPS) report regularly about the technological progress of SIC power devices. Major challenges for fully unleashing the capabilities of SiC power devices are:

Gate drive: SiC devices often require gate drive voltage levels that are different from their silicon counterparts and may be even unsymmetric, for example, +20 V and −5 V.[50] Packaging: SiC chips may have a higher power density than silicon power devices and are able to handle higher temperatures exceeding the silicon limit of 150 °C. New die attach technologies such as sintering are required to efficiently get the heat out of the devices and ensure a reliable interconnection.[51]

Electric systems[edit] The earliest electrical application of SiC was in lightning arresters in electric power systems. These devices must exhibit high resistance until the voltage across them reaches a certain threshold VT at which point their resistance must drop to a lower level and maintain this level until the applied voltage drops below VT.[43] It was recognized early on that SiC had such a voltage-dependent resistance, and so columns of SiC pellets were connected between high-voltage power lines and the earth. When a lightning strike to the line raises the line voltage sufficiently, the SiC column will conduct, allowing strike current to pass harmlessly to the earth instead of along the power line. Such SiC columns proved to conduct significantly at normal power-line operating voltages and thus had to be placed in series with a spark gap. This spark gap is ionized and rendered conductive when lightning raises the voltage of the power line conductor, thus effectively connecting the SiC column between the power conductor and the earth. Spark gaps used in lightning arresters are unreliable, either failing to strike an arc when needed or failing to turn off afterwards, in the latter case due to material failure or contamination by dust or salt. Usage of SiC columns was originally intended to eliminate the need for the spark gap in a lightning arrester. Gapped SiC lightning arresters were used as lightning-protection tool and sold under GE and Westinghouse brand names, among others. The gapped SiC arrester has been largely displaced by no-gap varistors that use columns of zinc oxide pellets.[44]

Automobile parts[edit] Silicon-infiltrated carbon-carbon composite is used for high performance "ceramic" brake discs, as it is able to withstand extreme temperatures. The silicon reacts with the graphite in the carbon-carbon composite to become carbon-fiber-reinforced silicon carbide (C/SiC). These discs are used on some road-going sports cars, supercars, as well as other performance cars including the Porsche Carrera GT, the Bugatti Veyron, the Chevrolet Corvette ZR1, Bentleys, Ferraris, Lamborghinis, some specific high performance Audis, and the McLaren P1.[40] Silicon carbide is also used in a sintered form for diesel particulate filters.[41] SiC is also used as an oil additive to reduce friction, emissions, and harmonics.[42]

The Porsche Carrera GT's carbon-ceramic (silicon carbide) disc brake

Silicon carbide is used for trauma plates of ballistic vests

Structural material[edit]

In the 1980s and 1990s, silicon carbide was studied in several research programs for high-temperature gas turbines in Europe, Japan and the United States. The components were intended to replace nickel superalloy turbine blades or nozzle vanes. However, none of these projects resulted in a production quantity, mainly because of its low impact resistance and its low fracture toughness.[36]

Like other hard ceramics (namely alumina and boron carbide), silicon carbide is used in composite armor (e.g. Chobham armor), and in ceramic plates in bulletproof vests. Dragon Skin, which is produced by Pinnacle Armor, uses disks of silicon carbide.[37]

Silicon carbide is used as a support and shelving material in high temperature kilns such as for firing ceramics, glass fusing, or glass casting. SiC kiln shelves are considerably lighter and more durable than traditional alumina shelves.[38]

In December 2015, infusion of silicon carbide nano-particles in molten magnesium was mentioned as a way to produce a new strong and plastic alloy suitable for use in aeronautics, aerospace, automobile and micro-electronics.

Abrasive and cutting tools[edit] In the arts, silicon carbide is a popular abrasive in modern lapidary due to the durability and low cost of the material. In manufacturing, it is used for its hardness in abrasive machining processes such as grinding, honing, water-jet cutting and sandblasting. Particles of silicon carbide are laminated to paper to create sandpapers and the grip tape on skateboards.[34] In 1982 an exceptionally strong composite of aluminium oxide and silicon carbide whiskers was discovered. Development of this laboratory-produced composite to a commercial product took only three years. In 1985, the first commercial cutting tools made from this alumina and silicon carbide whisker-reinforced composite were introduced to the market.[35]

Electrical conductivity[edit] Silicon carbide is a semiconductor, which can be doped n-type by nitrogen or phosphorus and p-type by beryllium, boron, aluminium, or gallium.[3] Metallic conductivity has been achieved by heavy doping with boron, aluminium or nitrogen. Superconductivity has been detected in 3C-SiC:Al, 3C-SiC:B and 6H-SiC:B at the same temperature of 1.5 K.[29][32] A crucial difference is however observed for the magnetic field behavior between aluminium and boron doping: SiC:Al is type-II, same as Si:B. On the contrary, SiC:B is type-I. In attempt to explain this difference, it was noted that Si sites are more important than carbon sites for superconductivity in SiC. Whereas boron substitutes carbon in SiC, Al substitutes Si sites. Therefore, Al and B "see" different environment that might explain different properties of SiC:Al and SiC:B.[33]

Silicon carbide exists in about 250 crystalline forms.[27] The polymorphism of SiC is characterized by a large family of similar crystalline structures called polytypes. They are variations of the same chemical compound that are identical in two dimensions and differ in the third. Thus, they can be viewed as layers stacked in a certain sequence.[28]

Alpha silicon carbide (α-SiC) is the most commonly encountered polymorph; it is formed at temperatures greater than 1700 °C and has a hexagonal crystal structure (similar to Wurtzite). The beta modification (β-SiC), with a zinc blende crystal structure (similar to diamond), is formed at temperatures below 1700 °C.[29] Until recently, the beta form has had relatively few commercial uses, although there is now increasing interest in its use as a support for heterogeneous catalysts, owing to its higher surface area compared to the alpha form.

Properties of major SiC polytypes[3][23] Polytype 3C (β) 4H 6H (α) Crystal structure Zinc blende (cubic) Hexagonal Hexagonal Space group T2d-F43m C46v-P63mc C46v-P63mc Pearson symbol cF8 hP8 hP12 Lattice constants (Å) 4.3596 3.0730; 10.053 3.0810; 15.12 Density (g/cm3) 3.21 3.21 3.21 Bandgap (eV) 2.36 3.23 3.05 Bulk modulus (GPa) 250 220 220 Thermal conductivity (W cm−1K−1) @ 300K (see [30] for temp. dependence) 3.6 3.7 4.9 Pure SiC is colorless. The brown to black color of industrial product results from iron impurities. The rainbow-like luster of the crystals is caused by a passivation layer of silicon dioxide that forms on the surface. The high sublimation temperature of SiC (approximately 2700 °C) makes it useful for bearings and furnace parts. Silicon carbide does not melt at any known pressure. It is also highly inert chemically. There is currently much interest in its use as a semiconductor material in electronics, where its high thermal conductivity, high electric field breakdown strength and high maximum current density make it more promising than silicon for high-powered devices.[31] SiC also has a very low coefficient of thermal expansion (4.0 × 10−6/K) and experiences no phase transitions that would cause discontinuities in thermal expansion.[

Production[edit]

Because of the rarity of natural moissanite, most silicon carbide is synthetic. It is used as an abrasive, and more recently as a semiconductor and diamond simulant of gem quality. The simplest manufacturing process is to combine silica sand and carbon in an Acheson graphite electric resistance furnace at a high temperature, between 1,600 °C (2,910 °F) and 2,500 °C (4,530 °F). Fine SiO2 particles in plant material (e.g. rice husks) can be converted to SiC by heating in the excess carbon from the organic material.[15] The silica fume, which is a byproduct of producing silicon metal and ferrosilicon alloys, also can be converted to SiC by heating with graphite at 1,500 °C (2,730 °F).[16]

Synthetic SiC crystals ~3 mm in diameter

Synthetic SiC Lely crystals

The material formed in the Acheson furnace varies in purity, according to its distance from the graphite resistor heat source. Colorless, pale yellow and green crystals have the highest purity and are found closest to the resistor. The color changes to blue and black at greater distance from the resistor, and these darker crystals are less pure. Nitrogen and aluminium are common impurities, and they affect the electrical conductivity of SiC.[17]

Pure silicon carbide can be made by the so-called Lely process,[18] in which SiC powder is sublimated into high-temperature species of silicon, carbon, silicon dicarbide (SiC2), and disilicon carbide (Si2C) in an argon gas ambient at 2500 °C and redeposited into flake-like single crystals,[19] sized up to 2×2 cm, at a slightly colder substrate. This process yields high-quality single crystals, mostly of 6H-SiC phase (because of high growth temperature). A modified Lely process involving induction heating in graphite crucibles yields even larger single crystals of 4 inches (10 cm) in diameter, having a section 81 times larger compared to the conventional Lely process.[20] Cubic SiC is usually grown by the more expensive process of chemical vapor deposition (CVD).[17][21] Homoepitaxial and heteroepitaxial SiC layers can be grown employing both gas and liquid phase approaches.[22] Pure silicon carbide can also be prepared by the thermal decomposition of a polymer, poly(methylsilyne), under an inert atmosphere at low temperatures. Relative to the CVD process, the pyrolysis method is advantageous because the polymer can be formed into various shapes prior to thermalization into the ceramic.[23][24][25][26]

The first use of SiC was as an abrasive. This was followed by electronic applications. In the beginning of the 20th century, silicon carbide was used as a detector in the first radios.[9] In 1907 Henry Joseph Round produced the first LED by applying a voltage to a SiC crystal and observing yellow, green and orange emission at the cathode. Those experiments were later repeated by O. V. Losev in theSoviet Union in 1923.[10]

Natural occurrence[edit]

Moissanite single crystal (≈1 mm in size)

Naturally occurring moissanite is found in only minute quantities in certain types of meteorite and in corundum deposits and kimberlite. Virtually all the silicon carbide sold in the world, including moissanite jewels, is synthetic. Natural moissanite was first found in 1893 as a small component of the Canyon Diablo meteorite in Arizona by Dr. Ferdinand Henri Moissan, after whom the material was named in 1905.[11] Moissan's discovery of naturally occurring SiC was initially disputed because his sample may have been contaminated by silicon carbide saw blades that were already on the market at that time.[12]

While rare on Earth, silicon carbide is remarkably common in space. It is a common form of stardust found around carbon-rich stars, and examples of this stardust have been found in pristine condition in primitive (unaltered) meteorites. The silicon carbide found in space and in meteorites is almost exclusively the beta-polymorph. Analysis of SiC grains found in the Murchison meteorite, a carbonaceous chondrite meteorite, has revealed anomalous isotopic ratios of carbon and silicon, indicating an origin from outside the solar system; 99% of these SiC grains originate around carbon-rich asymptotic giant branch stars.[13] SiC is commonly found around these stars as deduced from their infrared spectra.[14]

Wide-scale production[edit] A replication of H. J. Round's LED experiments Wide-scale production is credited to Edward Goodrich Acheson in 1890.[5] Acheson was attempting to prepare artificial diamonds when he heated a mixture of clay (aluminum silicate) and powdered coke (fuel) (carbon) in an iron bowl. He called the blue crystals that formed Carborundum, believing it to be a new compound of carbon and aluminum, similar to corundum. In 1893, Henri Moissan discovered the very rare naturally-occurring SiC mineral while examining rock samples found in the Canyon Diablo meteorite in Arizona. The mineral was named moissanite in his honor. Moissan also synthesized SiC by several routes, including dissolution of carbon in molten silicon, melting a mixture of calcium carbide and silica, and by reducing silica with carbon in an electric furnace. Acheson patented the method for making silicon carbide powder on February 28, 1893.[6] Acheson also developed the electric batch furnace by which SiC is still made today and formed the Carborundum Company to manufacture bulk SiC, initially for use as an abrasive.[7] In 1900 the company settled with the Electric Smelting and Aluminum Company when a judge's decision gave "priority broadly" to its founders "for reducing ores and other substances by the incandescent method".[8] It is said that Acheson was trying to dissolve carbon in molten corundum (alumina) and discovered the presence of hard, blue-black crystals which he believed to be a compound of carbon and corundum: hence carborundum. It may be that he named the material "carborundum" by analogy to corundum, which is another very hard substance (9 on the Mohs scale).

Early experiments[edit] Non-systematic, less-recognized, and often unverified syntheses of silicon carbide include J. J. Berzelius's reduction of potassium fluorosilicate by potassium (1810) César-Mansuète Despretz's passing an electric current through a carbon rod embedded in sand (1849) Robert Sydney Marsden's dissolution of silica in molten silver in a graphite crucible (1881) Paul Schuetzenberger's heating of a mixture of silicon and silica in a graphite crucible (1881) Albert Colson's heating of silicon under a stream of ethylene (1882).[4]

QMRSilicon carbide (SiC), also known as carborundum /kɑrbəˈrʌndəm/, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive. Grains of silicon carbide can be bonded together by sintering to form very hard ceramics that are widely used in applications requiring high endurance, such as car brakes, car clutches and ceramic plates in bulletproof vests. Electronic applications of silicon carbide as light-emitting diodes (LEDs) and detectors in early radios were first demonstrated around 1907. SiC is used in semiconductor electronics devices that operate at high temperatures or high voltages or both. Large single crystals of silicon carbide can be grown by the Lely method; they can be cut into gems known as synthetic moissanite. Silicon carbide with high surface area can be produced from SiO2 contained in plant material.

QMRThe Acheson process is a process to synthesize graphite and silicon carbide, named after its inventor Edward Goodrich Acheson. Again, graphite is composed of carbon, which is shaped as a quadrant, and silicon is shaped as a quadrant.

The process consists of heating a mixture of silica or quartz sand[1] and powdered coke (carbon) in an iron bowl. Acheson, in 1890, originally attempted to synthesize artificial diamond, but ended up creating blue crystals of silicon carbide, which he called carborundum.[2] When heated to 4150 °C, the silicon is removed, leaving graphite. The process was patented by Acheson in 1896.[3] After discovering this process, Acheson developed an efficient electric furnace based on resistive heating, the design of which is the basis of most silicon carbide manufacturing today. Silicon carbide was a useful material in jewelry making due to its abrasive properties, and this was the first commercial application of the Acheson process.[4]

In the furnace, an electric current was passed through a graphite core, surrounded by sand, salt, and carbon. The electric current heated the graphite and other materials, allowing them to react, producing a layer of silicon carbide around the graphite core. The process gives off carbon monoxide. There are four chemical reactions in the process that produces silicon carbide (SiC):[4]

C + SiO2 → SiO + CO

SiO2 + CO → SiO + CO2

C + CO2 → 2CO

2C + SiO → SiC + CO

The first light emitting diodes were produced using silicon carbide from the Acheson process. The potential use of silicon carbide as a semiconductor led to the development of the Lely process, which was based on the Acheson process, but allowed control over the purity of the silicon carbide crystals.[5]

The first commercial plant using the Acheson process was built by Acheson in Niagara Falls, New York, where hydroelectric plants nearby could cheaply produce the necessary power for the energy intensive process. By 1896, The Carborundum Company was producing 1 million pounds of "carborundum".[6] Many current silicon carbide plants use the same basic design as the first Acheson plant. In the first plant, sawdust and salt were added to the sand to control purity. The addition of salt was stopped in the 1960s, as the advantages of greater purity were outweighed by the disadvantages of the corrosion of steel structures, which the salt caused. The addition of sawdust was stopped in some plants to reduce emissions.[4]

In the manufacture of synthetic graphite, the Acheson process is run for approximately 20 hours, with currents of 200 A, and voltages of 40,000–50,000 V (8–10 MW). The purity of graphite achievable using the process is 99.5%.

Graphite mining, beneficiation, and milling[edit] Large graphite specimen. Naturalis Biodiversity Center Graphite is mined by both open pit and underground methods. Graphite usually needs beneficiation. This may be carried out by hand-picking the pieces of gangue (rock) and hand-screening the product or by crushing the rock and floating out the graphite. Beneficiation by flotation encounters the difficulty that graphite is very soft and "marks" (coats) the particles of gangue. This makes the "marked" gangue particles float off with the graphite, yielding impure concentrate. There are two ways of obtaining a commercial concentrate or product: repeated regrinding and floating (up to seven times) to purify the concentrate, or by acid leaching (dissolving) the gangue with hydrofluoric acid (for a silicate gangue) or hydrochloric acid (for a carbonate gangue). In milling, the incoming graphite products and concentrates can be ground before being classified (sized or screened), with the coarser flake size fractions (below 8 mesh, 8–20 mesh, 20–50 mesh) carefully preserved, and then the carbon contents are determined. Some standard blends can be prepared from the different fractions, each with a certain flake size distribution and carbon content. Custom blends can also be made for individual customers who want a certain flake size distribution and carbon content. If flake size is unimportant, the concentrate can be ground more freely. Typical end products include a fine powder for use as a slurry in oil drilling and coatings for foundry molds, carbon raiser in the steel industry (Synthetic graphite powder and powdered petroleum coke can also be used as carbon raiser). Environmental impacts from graphite mills consist of air pollution including fine particulate exposure of workers and also soil contamination from powder spillages leading to heavy metals contaminations of soil.

Other uses[edit] Graphite (carbon) fiber and carbon nanotubes are also used in carbon fiber reinforced plastics, and in heat-resistant composites such as reinforced carbon-carbon (RCC). Commercial structures made from carbon fiber graphite composites include fishing rods, golf club shafts, bicycle frames, sports car body panels, the fuselage of the Boeing 787 Dreamliner and pool cue sticks and have been successfully employed in reinforced concrete, The mechanical properties of carbon fiber graphite-reinforced plastic composites and grey cast iron are strongly influenced by the role of graphite in these materials. In this context, the term "(100%) graphite" is often loosely used to refer to a pure mixture of carbon reinforcement and resin, while the term "composite" is used for composite materials with additional ingredients.[40] Modern smokeless powder is coated in graphite to prevent the buildup of static charge. Graphite has been used in at least three radar absorbent materials. It was mixed with rubber in Sumpf and Schornsteinfeger, which were used on U-boat snorkels to reduce their radar cross section. It was also used in tiles on early F-117 Nighthawk (1983)s.

Powder and scrap[edit] The powder is made by heating powdered petroleum coke above the temperature of graphitization, sometimes with minor modifications. The graphite scrap comes from pieces of unusable electrode material (in the manufacturing stage or after use) and lathe turnings, usually after crushing and sizing. Most synthetic graphite powder goes to carbon raising in steel (competing with natural graphite), with some used in batteries and brake linings. According to the USGS, US synthetic graphite powder and scrap production was 95,000 tonnes in 2001 (latest data).[8] Neutron moderator[edit] Main article: Nuclear graphite Special grades of synthetic graphite also find use as a matrix and neutron moderator within nuclear reactors. Its low neutron cross-section also recommends it for use in proposed fusion reactors. Care must be taken that reactor-grade graphite is free of neutron absorbing materials such as boron, widely used as the seed electrode in commercial graphite deposition systems—this caused the failure of the Germans' World War II graphite-based nuclear reactors. Since they could not isolate the difficulty they were forced to use far more expensive heavy water moderators. Graphite used for nuclear reactors is often referred to as nuclear graphite.

Scientific research[edit]

Highly oriented pyrolytic graphite (HOPG) is the highest-quality synthetic form of graphite. It is used in scientific research, in particular, as a length standard for scanner calibration of scanning probe microscope.[38][39]

Electrodes[edit]

Graphite electrodes carry the electricity that melts scrap iron and steel (and sometimes direct-reduced iron: DRI) in electric arc furnaces, which are the vast majority of steel furnaces. They are made from petroleum coke after it is mixed with coal tar pitch. They are then extruded and shaped, baked to carbonize the binder (pitch), and finally graphitized by heating it to temperatures approaching 3000 °C, at which the carbon atoms arrange into graphite. They can vary in size up to 11 ft. long and 30 in. in diameter. An increasing proportion of global steel is made using electric arc furnaces, and the electric arc furnace itself is getting more efficient, making more steel per tonne of electrode. An estimate based on USGS data indicates that graphite electrode consumption was 197,000 tonnes in 2005.[8]

On a much smaller scale, graphite is also used for making electrodes for electrical discharge machining (EDM), commonly used to make plastic injection molds.

Uses of synthetic graphite[edit] Invention of a process to produce synthetic graphite[edit] A process to make synthetic graphite was invented by Edward Goodrich Acheson (1856–1931). In the mid-1890s, Acheson discovered that overheating carborundum, which he is also credited with discovering, produced almost pure graphite. While studying the effects of high temperature on carborundum, he had found that silicon vaporizes at about 4,150 °C (7,500 °F), leaving behind graphitic carbon. This graphite was another major discovery for him, and it became extremely valuable and helpful as a lubricant.[6] In 1896 Acheson received a patent for his method of synthesizing graphite,[37] and in 1897 started commercial production.[6] The Acheson Graphite Co. was formed in 1899. In 1928 this company was merged with National Carbon Company (now GrafTech International). Acheson also developed a variety of colloidal graphite products including Oildag and Aquadag. These were later manufactured by the Acheson Colloids Co. (now Acheson Industries, a unit of Henkel AG).

Expanded graphite[edit]

Expanded graphite is made by immersing natural flake graphite in a bath of chromic acid, then concentrated sulfuric acid, which forces the crystal lattice planes apart, thus expanding the graphite. The expanded graphite can be used to make graphite foil or used directly as "hot top" compound to insulate molten metal in a ladle or red-hot steel ingots and decrease heat loss, or as firestops fitted around a fire door or in sheet metal collars surrounding plastic pipe (during a fire, the graphite expands and chars to resist fire penetration and spread), or to make high-performance gasket material for high-temperature use. After being made into graphite foil, the foil is machined and assembled into the bipolar plates in fuel cells. The foil is made into heat sinks for laptop computers which keeps them cool while saving weight, and is made into a foil laminate that can be used in valve packings or made into gaskets. Old-style packings are now a minor member of this grouping: fine flake graphite in oils or greases for uses requiring heat resistance. A GAN estimate of current US natural graphite consumption in this end use is 7,500 tonnes.[8]

Intercalated graphite[edit] Main article: Graphite intercalation compound Structure of CaC6 Graphite forms intercalation compounds with some metals and small molecules. In these compounds, the host molecule or atom gets "sandwiched" between the graphite layers, resulting in a type of compounds with variable stoichiometry. A prominent example of an intercalation compound is potassium graphite, denoted by the formula KC8. Graphite intercalation compounds are superconductors. The highest transition temperature (by June 2009) Tc = 11.5 K is achieved in CaC6, and it further increases under applied pressure (15.1 K at 8 GPa).[

Foundry facings and lubricants[edit]

A foundry facing mold wash is a water-based paint of amorphous or fine flake graphite. Painting the inside of a mold with it and letting it dry leaves a fine graphite coat that will ease separation of the object cast after the hot metal has cooled. Graphite lubricants are specialty items for use at very high or very low temperatures, as forging die lubricant, an antiseize agent, a gear lubricant for mining machinery, and to lubricate locks. Having low-grit graphite, or even better no-grit graphite (ultra high purity), is highly desirable. It can be used as a dry powder, in water or oil, or as colloidal graphite (a permanent suspension in a liquid). An estimate based on USGS graphite consumption statistics indicates that 2,200 tonnes was used in this fashion in 2005.[8]

Pencils[edit]

Graphite pencils

Graphite pencils

The ability to leave marks on paper and other objects gave graphite its name, given in 1789 by German mineralogist Abraham Gottlob Werner. It stems from graphein, meaning to write/draw in Ancient Greek.[6][31]

From the 16th Century, pencils were made with leads of English natural graphite, but modern pencil lead is most commonly a mix of powdered graphite and clay; it was invented by Nicolas-Jacques Conté in 1795.[32][33] It is chemically unrelated to the metal lead, whose ores had a similar appearance, hence the continuation of the name. Plumbago is another older term for natural graphite used for drawing, typically as a lump of the mineral without a wood casing. The term plumbago drawing is normally restricted to 17th and 18th century works, mostly portraits. Today, pencils are still a small but significant market for natural graphite. Around 7% of the 1.1 million tonnes produced in 2011 was used to make pencils.[30] Low-quality amorphous graphite is used and sourced mainly from China.[8] Other uses[edit] Natural graphite has found uses in zinc-carbon batteries, in electric motor brushes, and various specialized applications. Graphite of various hardness or softness results in different qualities and tones when used as an artistic medium.[34] Railroads would often mix powdered graphite with waste oil or linseed oil to create a heat resistant protective coating for the exposed portions of a steam locomotive's boiler, such as the smokebox or lower part of the firebox.[

Steelmaking[edit] Natural graphite in this end use mostly goes into carbon raising in molten steel, although it can be used to lubricate the dies used to extrude hot steel. Supplying carbon raisers is very competitive, therefore subject to cut-throat pricing from alternatives such as synthetic graphite powder, petroleum coke, and other forms of carbon. A carbon raiser is added to increase the carbon content of the steel to the specified level. An estimate based on USGS US graphite consumption statistics indicates that 10,500 tonnes were used in this fashion in 2005.[8] Brake linings[edit] Natural amorphous and fine flake graphite are used in brake linings or brake shoes for heavier (nonautomotive) vehicles, and became important with the need to substitute for asbestos. This use has been important for quite some time, but nonasbestos organic (NAO) compositions are beginning to reduce graphite's market share. A brake-lining industry shake-out with some plant closures has not been beneficial, nor has an indifferent automotive market. According to the USGS, US natural graphite consumption in brake linings was 6,510 tonnes in 2005.[8]

Batteries[edit] The use of graphite in batteries has been increasing in the last 30 years. Natural and synthetic graphite are used to construct the anode of all major battery technologies.[8] The lithium-ion battery utilizes roughly twice the amount of graphite than lithium carbonate.[30] The demand for batteries, primarily nickel-metal-hydride and lithium-ion batteries, has caused a growth in graphite demand in the late 1980s and early 1990s. This growth was driven by portable electronics, such as portable CD players and power tools. Laptops, mobile phones, tablet, and smartphone products have increased the demand for batteries. Electric vehicle batteries are anticipated to increase graphite demand. As an example, a lithium-ion battery in a fully electric Nissan Leaf contains nearly 40 kg of graphite.

Uses of natural graphite[edit]

Natural graphite is mostly consumed for refractories, batteries, steelmaking, expanded graphite, brake linings, foundry facings and lubricants.[8] Graphene, which occurs naturally in graphite, has unique physical properties and is among the strongest substances known. However, the process of separating it from graphite will require more technological development.

Refractories[edit]

This end-use began before 1900 with the graphite crucible used to hold molten metal; this is now a minor part of refractories. In the mid-1980s, the carbon-magnesite brick became important, and a bit later the alumina-graphite shape. Currently the order of importance is alumina-graphite shapes, carbon-magnesite brick, monolithics (gunning and ramming mixes), and then crucibles.

Crucibles began using very large flake graphite, and carbon-magnesite brick requiring not quite so large flake graphite; for these and others there is now much more flexibility in size of flake required, and amorphous graphite is no longer restricted to low-end refractories. Alumina-graphite shapes are used as continuous casting ware, such as nozzles and troughs, to convey the molten steel from ladle to mold, and carbon magnesite bricks line steel converters and electric arc furnaces to withstand extreme temperatures. Graphite Blocks are also used in parts of blast furnace linings where the high thermal conductivity of the graphite is critical. High-purity monolithics are often used as a continuous furnace lining instead of the carbon-magnesite bricks.

The US and European refractories industry had a crisis in 2000–2003, with an indifferent market for steel and a declining refractory consumption per tonne of steel underlying firm buyouts and many plant closures. Many of the plant closures resulted from the acquisition of Harbison-Walker Refractories by RHI AG and some plants had their equipment auctioned off. Since much of the lost capacity was for carbon-magnesite brick, graphite consumption within refractories area moved towards alumina-graphite shapes and monolithics, and away from the brick. The major source of carbon-magnesite brick is now imports from China. Almost all of the above refractories are used to make steel and account for 75% of refractory consumption; the rest is used by a variety of industries, such as cement. According to the USGS, US natural graphite consumption in refractories was 12,500 tonnes in 2010.[8] Batteries

Other names [edit] Historically, graphite was called black lead or plumbago.[6][26] Plumbago was commonly used in its massive mineral form. Both of these names arise from confusion with the similar-appearing lead ores, particularly galena. The Latin word for lead, plumbum, gave its name to the English term for this grey metallic-sheened mineral and even to the leadworts or plumbagos, plants with flowers that resemble this colour. The term black lead usually refers to a powdered or processed graphite, matte black in color. Abraham Gottlob Werner coined the name graphite ("writing stone") in 1789. He attempted to clear up the confusion between molybdena, plumbago and blacklead after Carl Wilhelm Scheele in 1778 proved that there are at least three different minerals. Scheele's analysis showed that the chemical compounds molybdenum sulfide (molybdenite), lead(II) sulfide (galena) and graphite were three different soft black minerals.[27][28][29]

History of natural graphite use[edit] In the 4th millennium B.C., during the Neolithic Age in southeastern Europe, the Mariţa culture used graphite in a ceramic paint for decorating pottery.[22] Some time before 1565 (some sources say as early as 1500), an enormous deposit of graphite was discovered on the approach to Grey Knotts from the hamlet of Seathwaite in Borrowdale parish, Cumbria, England, which the locals found very useful for marking sheep.[23][24] During the reign of Elizabeth I (1533–1603), Borrowdale graphite was used as a refractory material to line moulds for cannonballs, resulting in rounder, smoother balls that could be fired farther, contributing to the strength of the English navy. This particular deposit of graphite was extremely pure and soft, and could easily be broken into sticks. Because of its military importance, this unique mine and its production were strictly controlled by the Crown.[25]

Structure[edit] Graphite has a layered, planar structure. In each layer, the carbon atoms are arranged in a honeycomb lattice with separation of 0.142 nm, and the distance between planes is 0.335 nm.[9] Atoms in the plane are bonded covalently, with only three of the four potential bonding sites satisfied. The fourth electron is free to migrate in the plane, making graphite electrically conductive. However, it does not conduct in a direction at right angles to the plane. Bonding between layers is via weak van der Waals bonds, which allows layers of graphite to be easily separated, or to slide past each other. The two known forms of graphite, alpha (hexagonal) and beta (rhombohedral), have very similar physical properties, except the graphene layers stack slightly differently.[10] The hexagonal graphite may be either flat or buckled.[11] The alpha form can be converted to the beta form through mechanical treatment and the beta form reverts to the alpha form when it is heated above 1300 °C.[12]

Graphite occurs in metamorphic rocks as a result of the reduction of sedimentary carbon compounds during metamorphism. It also occurs in igneous rocks and in meteorites.[4] Minerals associated with graphite include quartz, calcite, micas and tourmaline. In meteorites it occurs with troilite and silicate minerals.[4] Small graphitic crystals in meteoritic iron are called cliftonite.[6] According to the United States Geological Survey (USGS), world production of natural graphite in 2012 was 1,100,000 tonnes, of which the following major exporters are: China (750 kt), India (150 kt), Brazil (75 kt), North Korea (30 kt) and Canada (26 kt). Graphite is not mined in the United States, but U.S. production of synthetic graphite in 2010 was 134 kt valued at $1.07 billion.

Types and varieties[edit] There are three principal types of natural graphite, each occurring in different types of ore deposit: Crystalline flake graphite (or flake graphite for short) occurs as isolated, flat, plate-like particles with hexagonal edges if unbroken and when broken the edges can be irregular or angular; Amorphous graphite: very fine flake graphite is sometimes called amorphous in the trade;[5] Lump graphite (also called vein graphite) occurs in fissure veins or fractures and appears as massive platy intergrowths of fibrous or acicular crystalline aggregates, and is probably hydrothermal in origin.[6] Highly ordered pyrolytic graphite or more correctly highly oriented pyrolytic graphite (HOPG) refers to graphite with an angular spread between the graphite sheets of less than 1°.[7] The name "graphite fiber" is also sometimes used to refer to carbon fiber or carbon fiber-reinforced polymer.

QMRGraphite /ˈɡræfaɪt/, archaically referred to as Plumbago, is a crystalline form of carbon, a semimetal, a native element mineral, and one of the allotropes of carbon. Graphite is the most stable form of carbon under standard conditions. Therefore, it is used in thermochemistry as the standard state for defining the heat of formation of carbon compounds. Graphite may be considered the highest grade of coal, just above anthracite and alternatively called meta-anthracite, although it is not normally used as fuel because it is difficult to ignite. Graphie is made up of carbon. Carbon is the other miracle element according to chemists. It also has four valence electrons and resembles a quadrant

QMR Mold materials[edit]

There are four main components for making a sand casting mold: base sand, a binder, additives, and a parting compound.

Again sand is made up of silicon, called the miracle element. It has four valence electrons and resembles a quadrant.

Silica sand[edit]

Silica (SiO2) sand is the sand found on a beach and is also the most commonly used sand. It is made by either crushing sandstone or taken from natural occurring locations, such as beaches and river beds. The fusion point of pure silica is 1,760 °C (3,200 °F), however the sands used have a lower melting point due to impurities. For high melting point casting, such as steels, a minimum of 98% pure silica sand must be used; however for lower melting point metals, such as cast iron and non-ferrous metals, a lower purity sand can be used (between 94 and 98% pure).[11]

Silica sand is the most commonly used sand because of its great abundance, and, thus, low cost (therein being its greatest advantage). Its disadvantages are high thermal expansion, which can cause casting defects with high melting point metals, and low thermal conductivity, which can lead to unsound casting. It also cannot be used with certain basic metal because it will chemically interact with the metal forming surface defect. Finally, it causes silicosis in foundry workers.[14]

Olivine sand[edit]

Olivine is a mixture of orthosilicates of iron and magnesium from the mineral dunite. Its main advantage is that it is free from silica, therefore it can be used with basic metals, such as manganese steels. Other advantages include a low thermal expansion, high thermal conductivity, and high fusion point. Finally, it is safer to use than silica, therefore it is popular in Europe.[14]

Chromite sand[edit]

Chromite sand is a solid solution of spinels. Its advantages are a low percentage of silica, a very high fusion point (1,850 °C (3,360 °F)), and a very high thermal conductivity. Its disadvantage is its costliness, therefore it's only used with expensive alloy steel casting and to make cores.[14]

Zircon sand[edit]

Zircon sand is a compound of approximately two-thirds zircon oxide (Zr2O) and one-third silica. It has the highest fusion point of all the base sands at 2,600 °C (4,710 °F), a very low thermal expansion, and a high thermal conductivity. Because of these good properties it is commonly used when casting alloy steels and other expensive alloys. It is also used as a mold wash (a coating applied to the molding cavity) to improve surface finish. However, it is expensive and not readily available.[14]

Chamotte sand[edit] Chamotte is made by calcining fire clay (Al2O3-SiO2) above 1,100 °C (2,010 °F). Its fusion point is 1,750 °C (3,180 °F) and has low thermal expansion. It is the second cheapest sand, however it is still twice as expensive as silica. Its disadvantages are very coarse grains, which result in a poor surface finish, and it is limited to dry sand molding. Mold washes are used to overcome the surface finish problem. This sand is usually used when casting large steel workpieces.[14][15]

This dance teacher teaches how to dance like Chris brown by doing first four moves like a quadrant in each of the four squares. Then he does four more moves.