Journal of the American Ceramic Society, Vol.83, No.7, 1761-1767, 2000
Paralinear oxidation of CVD SiC in simulated fuel-rich combustion
The oxidation kinetics of CVD SiC were measured by thermogravimetric analysis (TGA) in a 4H(2). 12H(2)O . 10CO . 7CO(2). 67N(2) gas mixture flowing at 0.44 cm/s at temperatures between 1300 degrees and 1450 degrees C in fused quartz furnace tubes at 1 atm total pressure. The SiC was oxidized to form solid SiO2. At greater than or equal to 1350 degrees C, the SiO2 was in turn volatilized, Volatilization kinetics were consistent with the thermodynamic predictions based on SiO formation. These two simultaneous reactions resulted in overall paralinear kinetics. A curve fitting technique was used to determine the linear and parabolic rate constants from the paralinear kinetic data, Volatilization of the protective SiO2 scale resulted in accelerated consumption of SIG. Recession rates under conditions more representative of actual combustors were estimated from the furnace data.