Silicon carbide

Silicon carbide (SiC), also known as carborundum (/ˌkɑːrbəˈrʌndəm/), 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. 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. Large single crystals of silicon carbide can be grown by the Lely method and they can be cut into gems known as synthetic moissanite.

Electronic applications of silicon carbide such 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.

Naturally occurring moissanite is found in only minute quantities in certain types of meteorite, 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 Ferdinand Henri Moissan, after whom the material was named in 1905. 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.

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 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 that these grains originated outside the Solar System.

Non-systematic, less-recognized, and often unverified syntheses of silicon carbide include:

Wide-scale production is credited to Edward Goodrich Acheson in 1891. Acheson was attempting to prepare artificial diamonds when he heated a mixture of clay (aluminium silicate) and powdered coke (carbon) in an iron bowl. He called the blue crystals that formed carborundum, believing it to be a new compound of carbon and aluminium, similar to corundum. Henri Moissan also synthesized SiC by several routes, including dissolution of carbon in molten silicon, melting a mixture of calcium carbide and silica, and reducing silica with carbon in an electric furnace.

Acheson patented the method for making silicon carbide powder on February 28, 1893. 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. 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".