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Silicon carbide (SiC), also known as carborundum (/ ˌ k ɑːr b ə ˈ r ʌ n d əm /), is a hard chemical compound containing silicon and carbon. A wide bandgap semiconductor , it occurs in nature as the extremely rare mineral moissanite , but has been mass-produced as a powder and crystal since 1893 for use as an abrasive .
Silicon carbide is commonly found around these stars, as deduced from their infrared spectra. [14] The discovery of silicon carbide in the Canyon Diablo meteorite and other places was delayed for a long time as carborundum (SiC) contamination had occurred from man-made abrasive tools .
Most modern lapidary work is done using motorized equipment. Polishing is done with resin- or metal-bonded emery, silicon carbide (carborundum), aluminium oxide , or diamond dust in successively decreasing particle sizes until a polish is achieved. In older systems, the grinding and polishing powders were applied separately to the grinding or ...
Many compound materials exhibit polymorphism, that is they can exist in different structures called polymorphs. Silicon carbide (SiC) is unique in this regard as more than 250 polymorphs of silicon carbide had been identified by 2006, [1] with some of them having a lattice constant as long as 301.5 nm, about one thousand times the usual SiC lattice spacings.
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. [ 3 ] In the 1940s, first the Manhattan Project and then the Soviet atomic bomb project adopted Acheson process for nuclear graphite manufacturing (see details there).
Boron carbide, B 4 C, on the other hand, has an unusual structure which includes icosahedral boron units linked by carbon atoms. In this respect boron carbide is similar to the boron rich borides. Both silicon carbide (also known as carborundum) and boron carbide are very hard materials and refractory. Both materials are important industrially.
Binary compounds such as tungsten carbide or boron nitride can be very refractory. Hafnium carbide is the most refractory binary compound known, with a melting point of 3890 °C. [8] [9] The ternary compound tantalum hafnium carbide has one of the highest melting points of all known compounds (4215 °C). [10] [11]
Icelandic name Manuscript description Image Að unni “To get a girl”, this magical stave is used by a man in love to gain the affections of the object of his desires.