Silicon carbide, commonly referred to as SiC, is an extremely hard, dark brown to black synthetic crystalline mineral created in 1891 by Edward Goodrich Acheson for use as an abrasive.
Pure silicon carbide is colorless, and can be doped n-type with nitrogen or phosphorus for semiconductor applications and p-type with beryllium, boron, or aluminium for other uses.
Characteristics
SiC, commonly referred to as silicon carbide, is an extremely hard material (second only to diamond and some synthetic compounds) and highly resistant to heat. Depending on its raw materials used for production, SiC may appear black or green depending on how heavily doped with boron, nitrogen or aluminium it has been. Silicon carbide also functions as a semiconductor material and doping with such elements can increase metallic conductivity further.
Silicon carbide differs from silicon nitride in that its formation involves tightly bound silicon and carbon atoms arranged as tetrahedra within its crystal structure, giving the material superior covalent strength when exposed to pressure.
Silicon carbide boasts excellent wear resistance and corrosion resistance, operating reliably at temperatures of 1600degC without losing structural integrity, while having a low thermal expansion rate.
Assembling silicon carbide requires the addition of a sintering additive in order to facilitate densification. These typically consist of 0.5% carbon and 0.5% boron, which react to prevent the formation of SiO2 on its surface and modify grain boundary energy in order to induce pore shrinkage. Silicon carbide also has excellent physical properties: Mohs scale hardness rating of 9.5; it can be easily formed into almost any desired form through shaping or molding processes.
Tillämpningar
Silicon carbide (SiC) is an inorganic material composed of silicon and carbon that has become one of the most versatile refractory ceramics used industrially, from sandpaper and grinding wheels to furnace linings, wear-resistant parts for pumps, rocket engines, as well as semiconductor substrates. Due to its hard, synthetically produced nature and inherently impressive mechanical properties, silicon carbide makes an attractive candidate for use as semiconductor substrate material.
Carborundum abrasives are usually manufactured as powder or crystals that can be ground down into various abrasive products, while their use has been linked to diffuse interstitial pulmonary fibrosis and lung cancer among workers exposed to large quantities.
Edward Goodrich Acheson is widely credited with discovering moissanite. While trying to make diamonds from clay, Acheson discovered a hard, blue-to-black crystal known as carborundum when heating it with coke and heating it again with heat and steam – the initial discovery. Acheson recognized its industrial potential and founded an abrasive company to manufacture it more commercially in 1891. While natural moissanite is extremely rare; most is produced today via synthetic methods and doped with nitrogen or phosphorus for use as an n-type semiconductor or with beryllium, boron aluminum, or gallium doping to form p-type semiconductors.
Tillverkning
Silicon carbide is an abrasive material with outstanding thermal stability that makes it suitable for junction temperatures much higher than silicon (i.e., over 200degC). Furthermore, this strong yet wear-resistant material makes for excellent abrasive tools used in demanding industrial settings.
Silicon carbide, a highly crystalline material, is produced through sintering raw material granules with various sintering aids such as 0.5% boron to increase crystal structure and increase porosity – two essential requirements for effective sintering. Sintering aids also improve densification and facilitate smooth, fine-grained structures – for instance providing the material with enough porosity that it allows sintering processes to take place more easily.
Manufacturers combine equal quantities of silica (in the form of quartz sand) and carbon, typically coke, before heating this mixture in a graphite furnace to 2,500 degrees Celsius to cause chemical reaction that produces silicon carbide.
Once silicon carbide ingots have cooled, skilled workers carefully sort and classify them by size into narrow size fractions for milling if necessary for specific applications. This process can be energy intensive. Sometimes silicon carbide may also be further chemically treated to achieve specific properties for specific uses; workers exposed to silicon carbide manufacturing may develop respiratory disorders like diffuse interstitial pulmonary fibrosis or carborundum lung.
Säkerhet
Silicon carbide compounds are ideal for manufacturing bulletproof armor due to their hardness. Sintering binds grains of silicon carbide together into hard ceramic blocks that resist penetration by bullets and other harmful materials, providing protection from bullet penetration and other forms of penetration. Furthermore, their impact resistance, corrosion resistance and thermal shock resistance allow it to be used in high-temperature indirect heating applications like the lining of large blast furnaces.
Silicon carbide occurs naturally as the mineral moissanite, and was first mass-produced as an abrasive in 1893. Today, most commercial sales of this compound consist of synthetic powders or single crystals produced synthetically for commercial sale. Silicon carbide has since been adopted for various structural material applications including automobile brakes and clutches as well as bulletproof vest ceramic plates; in addition, moissanite can also be cut into moissanite gemstones although most currently sold are synthetic varieties.
Workers involved with producing silicon carbide or using carborundum abrasives may become susceptible to diffuse interstitial pulmonary fibrosis, which results in thickening of lung tissue and decreased oxygen supply – ultimately leading to death. Proper ventilation and protective equipment can reduce this risk. Furthermore, adding 3 weight percent lanthanum reduces activation energy requirements threefold while simultaneously decreasing particle agglomeration rates.
Swedish 
English