CHEMICAL-INSTABILITY OF SILICON-CARBIDE IN THE PRESENCE OF TRANSITION-METALS

SIC has been proved chemically unstable at temperatures >1073 K (800 d egrees C) in the presence of cobalt, nickel, or iron. The instability results from reactions of cobalt, nickel, or iron with SIC to produce silicides and free carbon. A method of calculation is proposed for the rmodynamic analyses of these reactions. The results show that the sili cides of cobalt, nickel, and iron are thermodynamically more stable th an SiC. The metal-silicon eutectic may provide kinetic condition to th e reactions. Calculations also are performed for reactions of SIC with other transition metals. Instabilities of SIC in the presence of thos e metals are predicted.