MECHANISM OF FORMATION OF SIC BY REACTION OF SIO WITH GRAPHITE AND CO

The rates of the reactions of the gaseous species SiO and CO with solid carbon have been studied by means of thermogravimetry at temperatures between 1673 and 1973 K in order to investigate the mechanism of the formation of SiC in SiO//2-C mixtures. The graphite substratum has been allowed to react with SiO and CO generated from the heated SiO//2// minus C mixture. The formation of SiC is linear with the reaction time. The activation energy is 97 kJ/mol. It is considered that the rate of formation is under a mixed control of the interfacial reaction and the gaseous diffusion. At 1873 K and higher, the layer of SiC grows into the graphite and the rate of the formation of SiC obeys the parabolic rate equation. The activation energy is 524kJ/mol. The rate-determining step is the diffusion of carbon in SiC.