Abstract

Carbon reacts with many elements of the Periodic Table to form a diverse group of compounds known as carbides, some of which are extremely important in technology. Their applications are varied, ranging from cutting tools and structural materials to magnetic and electronic components, and superconductive devices. For example, calcium carbide, CaC₂, is a source of acetylene; silicon carbide, SiC, and boron carbide, B₄C, are used as abrasives; tungsten carbide, WC, and titanium carbide, TiC, find use as structural materials. Cementite, Fe₃C, and the multimetallic complexes of Co, W, Cr, Fe, and Mo with carbon are the components in tool steels and Stellite-type alloys responsible for their hardness, wear resistance, and excellent cutting performance. Binary compounds of carbon are divided into four main groups: the salt-like, metallic, diamond-like, and volatile compounds of carbon. The nature of the bonding is correspondingly of ionic, metallic, semiconductor, or covalent character, but these divisions are not rigid and there are a number of transitional cases. For the metallic carbides, the solid-state structures and chemical properties reflect an increase in metal sp electron count. Carbides are generally prepared by the direct reaction of carbon with metals or metal-like materials at elevated temperatures. Their most outstanding properties are extreme hardness and physical strength combined with high temperature stability.