Silicon carbide (SiC), is an extremely hard and strong material with superior wear properties and temperature resistance, often used in metallurgy, automotive, semiconductor and electronics industries as well as making abrasives.
This material derives its strength and hardiness from tetrahedral silicon-carbon structures held together by covalent bonds within its crystal lattice, while color centres within the material can be activated on demand to emit single photons.
Origin
Silicon Carbide (SiC) is a wide bandgap semiconductor found naturally in moissanite gemstone and produced as an abrasive in laboratories; since 1893 it has also been mass-produced as powder to use as high endurance ceramic car brakes and clutches as well as bulletproof vest ceramic plates. SiC grains can also be fused together to form extremely hard ceramics.
Edward G. Acheson unwittingly created carborundum while trying to synthesize artificial diamonds. While heating a mixture of clay (aluminium silicate) and coke using an ordinary carbon arc light, Acheson observed shiny green crystals forming at his electrode. At first he thought he had hit upon something similar to rubies or sapphires – however soon realized he had discovered something much greater as his newly discovered compound was nearly as hard as diamond and could be mass produced industrially for use as abrasives.
SiC is relatively rare on Earth but highly abundant in space. Ejected from carbon-rich stars, SiC can often be found in meteorites, kimberlite and other natural formations here on Earth; fragments can sometimes even be found as meteorite fragments and meteorite shards. But in the late nineteenth century it became possible to cultivate large single crystals of moissanite and produce it for gem cutting as a “diamond substitute.” Thus leading some to refer to moissanite as synthetic diamond.
Properties
Silicon carbide (SiC), also referred to as carborundum, is an extremely hard and durable compound of silicon and carbon. Due to its unique crystalline structure comprised of bonds between tetrahedral carbon atoms and silicon atoms, SiC has excellent mechanical strength ratings of 9-9.5 on Mohs scale; low density; excellent fatigue resistance; high thermal conductivity; low coefficient of thermal expansion and high chemical inertia properties.
Carborundum’s exceptional hardness makes it ideal for use in applications involving abrasives such as grinding wheels and sandpaper, while its superior heat resistance – able to tolerate temperatures up to 1400degC – also make it suitable for use in harsh environments. Furthermore, carborundum resists corrosion as well as oxidation for continued usage in challenging settings.
SiC is an ideal material for semiconductor and electronic research due to its wide bandgap and high blocking voltage capabilities, making it an attractive candidate for research into both semiconductors and electronics. Furthermore, unlike silicon-based (Si) devices, SiC devices can operate at very high temperatures while also offering significant power efficiency advantages over their silicon counterparts.
Carborundum, commonly referred to as moissanite in nature, can also be produced synthetically through Acheson carburising – this allows the creation of controlled properties and composition for specific industrial uses such as refractories, high temperature research and semiconductor devices as well as ceramic applications like automobile brake system plates or bulletproof vests.
Synthesis
Silicon carbide (SiC) is an extremely hard and non-oxide ceramic material commonly found in industrial settings. SiC is known for its superior hardness, thermal conductivity and resistance to corrosion – qualities which make it suitable for electronics devices as well as cutting/abrasion applications.
Silicon Carbide is created through a chemical reaction at extremely high temperatures using raw materials such as silica sand and petroleum coke mixed together in a furnace that heats to temperatures exceeding 2700 degrees Celsius.
SiC synthesis can be improved by increasing the reaction temperature. Doing so increases both reaction rate and shortens reaction time; however, too much carbon consumption could damage purity of resulting powder; hence it should be carefully controlled in order to prevent over production of carbon.
Carbon-thermal reduction is one of the most popular methods used for producing SiC. It boasts low production expenses, straightforward procedures and higher product qualification rates; its downside lies in inconsistent and coarse powder production as well as oxygen absorption during calcination resulting in formation of amorphous particles.
Applications
Silicon carbide (SiC) is an extremely hard and durable wide bandgap semiconductor material found naturally as the rare mineral moissanite, mass produced as powder or crystal form since 1893 for use as an abrasive. Sintering bonds grains together into extremely hard ceramics used for applications requiring high durability such as bulletproof vest plates and car brakes, or used in carborundum printmaking, an artform using collagraph printing technology.
SiC has seen tremendous expansion in electric vehicle (EV) battery management systems in recent years. Thanks to its higher switching frequencies, superior thermal conductivity (three times better than Si) and ability to withstand temperatures up to 1000degC, SiC’s superior energy efficiency and smaller size help increase overall weight savings and energy efficiency while simultaneously decreasing battery size and weight.
Electric vehicles make up 40-50% of global electricity usage and any increase in power density can make a tremendous difference to driving distances. SiC is helping EV motor manufacturers do just this by increasing efficiency of boost converters which convert DC voltage from the battery into high current necessary for acceleration.
ST has invested significantly to meet the growing demand for SiC technology by investing in several large-scale manufacturing facilities. These include a 200 mm plant for power devices and modules as well as test and packaging capabilities; when combined with its 200 mm facility for SiC substrates currently undergoing preparation on site, these will form ST’s Silicon Carbide Campus which will offer industry-leading performance and reliability across a range of applications.
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