The High-Temperature Oxidation Behavior of Reaction-Bonded Porous Silicon Carbide Ceramics in Dry Oxygen

The oxidation behavior of reaction-bonded porous silicon carbide (RPSC) ceramics in dry oxygen between 1100 degrees and 1500 degrees C was investigated based on four specimens with different porosities. RPSC ceramics exhibited a rapid mass increase in the initial stage of oxidation but a slow mass increase in the following oxidation, which was considerably different from the oxidation behavior of dense SiC. The oxidation kinetics for RPSC can be better represented by an asymptotic law rather than the parabolic law for dense SiC. We suppose that, although oxidation occurred in the entire pore channels at the beginning, the pores were rapidly blocked by the oxide as their growth rate near the pore mouth was very fast due to sufficient oxygen. As the result, the oxidation of the pore interior was stopped in the absence of further oxygen supply.