silicon carbide
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What is silicon carbide?
Silicon carbide (SiC), also known as carborundum, is a synthetically produced crystalline compound of silicon and carbon with the chemical formula SiC. American inventor Edward G. Acheson discovered it in 1891 while attempting to produce artificial diamonds.
Silicon carbide is an exceedingly hard material. Until 1929, it was the hardest synthetic material known. It has a Mohs hardness rating of 9, close to that of diamond. Silicon carbide is manufactured by combining pure silica sand and carbon in an electric resistance furnace at very high temperatures.
Silicon carbide is used in sandpapers, grinding wheels, cutting tools, refractory linings, heating elements, and wear-resistant parts. It is also a semiconductor, making it a promising substitute for silicon in high-temperature applications.
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What elements make up silicon carbide?
Silicon carbide (SiC), also known as carborundum, is a crystalline compound of silicon and carbon. It is created synthetically and is extremely hard.
To manufacture silicon carbide, pure silica sand and carbon, in the form of finely ground coke, are mixed and heated in an electric furnace. At temperatures ranging from 2,200° to 2,700° C (4,000° to 4,900° F), the carbon in the coke and the silicon in the sand combine, forming silicon carbide (SiC) and carbon monoxide gas.
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How is silicon carbide made?
Silicon carbide (SiC) is made by combining pure silica sand and finely ground coke around a carbon conductor in a brick furnace. Electric current heats the mixture, initiating a reaction where carbon and silicon form SiC and carbon monoxide gas. Temperatures range from 2,200° to 2,700° C in the core and about 1,400° C at the edge, consuming over 100,000 kilowatt-hours per run. After several days, SiC crystals form, surrounded by raw materials. The aggregate is then crushed and sorted.
For specialized uses, reaction-bonded SiC is made by mixing SiC powder with carbon and a plasticizer, shaping, burning off the plasticizer, and infusing silicon. Chemical vapor deposition creates wear-resistant SiC layers, while large single crystals are grown from vapor for electronics. SiC fibers can also be made through chemical vapor deposition or by firing silicon-containing polymer fibers for reinforcing materials.
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What are some common uses for silicon carbide?
Silicon carbide (SiC) is a synthetically produced crystalline compound of silicon and carbon with extreme hardness. Common uses include:
* Abrasives: As an important material for sandpapers, grinding wheels, and cutting tools. Its crystals' fracture characteristics make it useful in abrasive products.
* Refractories: Its properties, such as high thermal conductivity, high-temperature strength, low thermal expansion, and chemical reaction resistance, make it valuable in high-temperature bricks and furnace linings.
* Semiconductors: SiC can be a substitute for silicon in high-temperature applications. It is suited for making devices for specialized high-temperature applications.
* Other: Wear-resistant parts for pumps and rocket engines and semiconducting substrates for light-emitting diodes.2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why is silicon carbide useful as an abrasive material?
Silicon carbide (SiC) is useful as an abrasive material due to its extreme hardness, approaching that of diamond. Until 1929, it was the hardest known synthetic material.
Its crystals' fracture characteristics make silicon carbide valuable in grinding wheels and abrasive paper and cloth products. Silicon carbide is also chemically inert. These properties have made it an important material for sandpapers, grinding wheels, and cutting tools since the late 19th century.
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How does silicon carbide compare to other materials in electronics and industry?
Silicon carbide (SiC) is a synthetically produced crystalline compound of silicon and carbon that is exceptionally hard. Until 1929, it was the hardest synthetic material known.
SiC has a high thermal conductivity, high-temperature strength, low thermal expansion, and resistance to chemical reactions, making it valuable in high-temperature bricks and refractories. SiC is a semiconductor, with electrical conductivity between metals and insulators, making it a promising substitute for silicon in high-temperature applications.
Modern methods of SiC manufacture include mixing silica sand and carbon and heating it in an electric resistance furnace. Special applications use advanced processes like reaction-bonded silicon carbide, chemical vapor deposition, and growing single crystals for electronics.
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silicon carbide, exceedingly hard, synthetically produced crystalline compound of silicon and carbon. Its chemical formula is SiC. Since the late 19th century silicon carbide has been an important material for sandpapers, grinding wheels, and cutting tools. More recently, it has found application in refractory linings and heating elements for industrial furnaces, in wear-resistant parts for pumps and rocket engines, and in semiconducting substrates for light-emitting diodes.
Discovery.
Silicon carbide was discovered by the American inventor Edward G. Acheson in 1891. While attempting to produce artificial diamonds, Acheson heated a mixture of clay and powdered coke in an iron bowl, with the bowl and an ordinary carbon arc-light serving as the electrodes. He found bright green crystals attached to the carbon electrode and thought that he had prepared some new compound of carbon and alumina from the clay. He called the new compound Carborundum because the natural mineral form of alumina is called corundum. Finding that the crystals approximated the hardness of diamond and immediately realizing the significance of his discovery, Acheson applied for a U.S. patent. His early product initially was offered for the polishing of gems and sold at a price comparable with natural diamond dust. The new compound, which was obtainable from cheap raw materials and in good yields, soon became an important industrial abrasive.
About the same time Acheson made his discovery, Henri Moissan in France produced a similar compound from a mixture of quartz and carbon; but in a publication of 1903, Moissan ascribed the original discovery to Acheson. Some natural silicon carbide was found in Arizona in the Canyon Diablo meteorite and bears the mineralogical name moissanite.
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Modern manufacture.
The modern method of manufacturing silicon carbide for the abrasives, metallurgical, and refractories industries is basically the same as that developed by Acheson. A mixture of pure silica sand and carbon in the form of finely ground coke is built up around a carbon conductor within a brick electrical resistance-type furnace. Electric current is passed through the conductor, bringing about a chemical reaction in which the carbon in the coke and silicon in the sand combine to form SiC and carbon monoxide gas. A furnace run can last several days, during which temperatures vary from 2,200° to 2,700° C (4,000° to 4,900° F) in the core to about 1,400° C (2,500° F) at the outer edge. The energy consumption exceeds 100,000 kilowatt-hours per run. At the completion of the run, the product consists of a core of green to black SiC crystals loosely knitted together, surrounded by partially or entirely unconverted raw material. The lump aggregate is crushed, ground, and screened into various sizes appropriate to the end use.
For special applications, silicon carbide is produced by a number of advanced processes. Reaction-bonded silicon carbide is produced by mixing SiC powder with powdered carbon and a plasticizer, forming the mixture into the desired shape, burning off the plasticizer, and then infusing the fired object with gaseous or molten silicon, which reacts with the carbon to form additional SiC. Wear-resistant layers of SiC can be formed by chemical vapour deposition, a process in which volatile compounds containing carbon and silicon are reacted at high temperatures in the presence of hydrogen. For advanced electronic applications, large single crystals of SiC can be grown from vapour; the boule can then be sliced into wafers much like silicon for fabrication into solid-state devices. For reinforcing metals or other ceramics, SiC fibres can be formed in a number of ways, including chemical vapour deposition and the firing of silicon-containing polymer fibres.
Properties and applications.
Until the invention of boron carbide in 1929, silicon carbide was the hardest synthetic material known. It has a Mohs hardness rating of 9, approaching that of diamond. In addition to hardness, silicon carbide crystals have fracture characteristics that make them extremely useful in grinding wheels and in abrasive paper and cloth products. Its high thermal conductivity, together with its high-temperature strength, low thermal expansion, and resistance to chemical reaction, makes silicon carbide valuable in the manufacture of high-temperature bricks and other refractories. It is also classed as a semiconductor, having an electrical conductivity between that of metals and insulating materials. This property, in combination with its thermal properties, makes SiC a promising substitute for traditional semiconductors such as silicon in high-temperature applications.