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 oxidation) was observed in a region of PCO2/PCO < 1, while mass gain (passive oxidation) was observed at around PCO2PCO= 10. In the active oxidation region below PCO2PCO= 10 –4, carbon particles were formed on the Si3N4 surface as an oxidation product, and the mass‐loss rates were independent of PCO2/PCO In the active oxidation region above PCO2/PCO= 10–4 the mass‐loss rates decreased with increasing PCO2/Pco. The critical PCO2/PCO value from the active to passive oxidation was 2 orders of magnitude larger than the calculated value predicted from the Wagner model.
|Number of pages||5|
|Journal||Journal of the American Ceramic Society|
|Publication status||Published - 1994 Nov|