Carborundum silicon carbide

There is considerable uncertainty al)out the heat of formation of carborundum, silicon carbide. A value of AHf= -28 kcal, based chiefly on the results of von Wartenberg and Schutte5 56 has been frequently used, but other evidence leads to values differing from this by over 20 kcal. Under these circumstances, the resulting E(G - Si) =64 kcal is not to be taken very seriously. 

Silicon carbide, SiC, is one of the hardest materials known. Surpassed in hardness only by diamond, it is sometimes known commercially as carborundum. Silicon carbide is used primarily as an abrasive for sandpaper and is manufactured by heating common sand (silicon dioxide, Si02) with carbon in a furnace. 

The first observation of silicon carbide was made in 1824 by Jons Jacob Berzelius. It was first prepared industrially in 1893 by the American chemist Edward Goodrich Acheson, who patented both the batch process and the electric furnace for making synthetic silicon-carbide powder. In 1894 he established the Carborundum Company in Monongahela City, PA, to manufacture bulk synthetic silicon carbide commercialized under the trade name Carborundum . Silicon carbide was initially used to produce grinding wheels, whetstones, knife sharpeners, and powdered abrasives. Despite being extremely rare in nature, when it occurs as a mineral it is called moissanite after the French chemist Henri Moissan who discovered it in a meteorite " in 1905. 

The formation of silicon carbide, SiC (carborundum), is prevented by the addition of a little iron as much of the silicon is added to steel to increase its resistance to attack by acids, the presence of a trace of iron does not matter. (Addition of silicon to bronze is found to increase both the strength and the hardness of the bronze.) Silicon is also manufactured by the reaction between silicon tetrachloride and zinc at 1300 K and by the reduction of trichlorosilane with hydrogen. 

Silicon carbide was made accidently by E. G. Acheson in 1891 he recognized its abrasive power and coined the name carborundum from carbo(n) and (co)rundum (AI2O3) to indicate that its hardness on the Mohs scale (9.5) was intermediate between that of diamond (10) and AI2O3 (9). Within months he had formed the Carborundum Co. for its manufacture, and current world production approaches 1 million tonnes annually. 

The covalent carbides include silicon carbide, SiC, which is sold as carborundum ... 

Pure silicon carbide is colorless, but iron impurities normally impart an almost black color to the crystals. Carborundum is an excellent abrasive because it is very hard, with a diamondlike structure that fractures into pieces with sharp edges (Fig. 14.43). 

Silicon, like carbon, is relatively inactive at ordinary temperatures. But, when heated, it reacts vigorously with the halogens (fluorine, chlorine, bromine, cmd iodine) to form halides and with certain metals to form silicides. It is unaffected by all acids except hydrofluoric. At red heat, silicon is attacked by water vapor or by oxygen, forming a surface layer of silicon dioxide. When silicon and carbon are combined at electric furnace temperatures of 2,000 to 2,600 °C (3,600 to 4700 °F), they form silicon carbide (Carborundum = SiC), which is an Importeint abrasive. When reacted with hydrogen, silicon forms a series of hydrides, the silanes. Silicon also forms a series of organic silicon compounds called silicones, when reacted with various organic compounds. 

Silicon carbide (carborundum) Talc Bluish-black, very hard crystals. Used as an abrasive and refractory material. A hydrous magnesium silicate used in ceramics, cosmetics, paint and pharmaceuticals. 

Silicon carbide, SiC or carborundum, has the diamond structure, and it is widely used as an abrasive in grinding wheels. These are made by crushing the SiC, adding clay, then heating the material in molds. Silicon carbide is prepared by the reaction... 

Among the useful compounds of silicon are silicon carbide (carborundum) and silicon nitride, which are hard, tough materials used for making cutting tools, abrasives, and engineering... 

Aluminum Oxide-Silicon Carbide Fiber, developed by the Carborundum Co at Niagara Falls, NY, will withstand temps of 2300°F. 

In 1891, a small amount of silicon carbide was produced bypassing a strong electric current from a carbon electrode through a mixture of clay and coke contained in an iron bowl that served as the second electrode (1). The abrasive value of the crystals obtained were recognized and The Carborundum Company was founded that year (2). About 10 years eadier tetratomic radicals of silicon (S CgOg, Si2C2N) had been reported (3). That work also produced some SiC. 

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