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 SiO2−C mixtures． The graphite sub− stratum has been allowed to react with SiO and CO generated from the heated SiO2−C mlxture． At lower temperatures， the deposit of SiC is formed on the graphite substratum by the Over＿all reaCtiOn The formation of SiC is linear with the reaction time． The activation energy is 97 kJ／mol． It is considered that the rate of the formation would be under a mixed control of the inter− facial reaction and the gaseous diffusion． At 1873 K and higher， SiC is formed by the over−all reactlon 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 524 kJ／mol． The rate−determining step is the diffusion of carbon in SiC．