T. Narushima et al., HIGH-TEMPERATURE OXIDATION OF CHEMICALLY VAPOR-DEPOSITED SILICON-NITRIDE IN A CARBON-MONOXIDE CARBON-DIOXIDE ATMOSPHERE, Journal of the American Ceramic Society, 77(11), 1994, pp. 2921-2925
Oxidation behavior of chemically vapor-deposited silicon nitride (CVD-
Si3N4) in CO-CO2 atmospheres between 1823 and 1923 K was investigated
using a thermogravimetric technique. Mass loss of Si3N4 (active oxidat
ion) was observed in a region of P-CO2/P-CO < 1, while mass gain (pass
ive oxidation) was observed at around P-CO2/P-CO 10. In the active oxi
dation region below P-CO2/P-CO 10(-4), carbon particles were formed on
the Si3N4 surface as an oxidation product, and the mass-loss rates we
re independent of P-CO2/P-CO. In the active oxidation region above P-C
O2/P-CO 10(-4), the mass-loss rates decreased with increasing P-CO2/P-
CO. The critical P-CO2/P-CO value from the active to passive oxidation
was 2 orders of magnitude larger than the calculated value predicted
from the Wagner model.