FORMATION AND REACTIVITY OF SOME METAL BORIDES AND CARBIDES

Abstract

Most recent developments in the production, properties and applications of borides and carbides are reviewed. The reactivity and sintering of finely-divided boron carbide with metal additives has been investigated. The additives (Fe, Ti, Zr, V, Nb, Ta, Mo, VJ and Al) generally promote sintering of the boron carbide. Their effectiveness as reduced occasionally when there is some surface activation caused by the metals reacting with the boron carbide to form metal borides and carbides of different crystal lattice type and molecular volume. The more metallic character of the bonding in the metal borides and carbides enhances surface and crystal lattice diffusion at the grain boundaries of the more covalent boron carbide. Iron is much more effective than the other metal additives tested in promoting sintering of the boron carbide at 1800°C since it forms the lowest-melting borides.