HIGH-TEMPERATURE ACTIVE OXIDATION OF CHEMICALLY VAPOR-DEPOSITED SILICON-CARBIDE IN CO-CO2 ATMOSPHERE

Active oxidation behavior of CVD-SiC in CO-CO2 atmospheres was investigated using a thermogravimetric technique in the temperature range between 1823 and 1923 K. The gas pressure ratio, P(CO2)/P(CO), was controlled between 10(-4) and 10(-1) at 0.1 MPa. Active oxidation rates (mass loss rates) showed maxima at a certain value of P(CO2)/P(CO), (P(CO2)/P(CO))*. In a P(CO2)/P(CO) region lower than the (P(CO2)/P(CO))*, a carbon layer was formed on the SiC surface. In a P(CO2)/P(CO) region higher than the (P(CO2)/P(CO))*, silica particles or a porous silica layer was observed on the SiC surface.