OXIDATION OF CHEMICALLY-VAPOR-DEPOSITED SILICON-CARBIDE IN CARBON-DIOXIDE

Chemically-vapor-deposited silicon carbide (CVD SiC) was oxidized in c arbon dioxide (CO2) at temperatures of 1200-1400 degrees C for times b etween 96 and 500 h at several gas flow rates. Oxidation weight gains were monitored by thermogravimetric analysis (TGA) and were found to b e very small and independent of temperature. Possible rate-limiting ki netic mechanisms are discussed. Passive oxidation of SiC by CO2 is neg ligible compared to the rates measured for other oxidants that are als o found in combustion environments, oxygen and water vapor.