The High Temperature Oxidation Behavior of Reaction–bonded Porous Silicon Carbide Ceramics

The oxidation behavior of reaction–bonded porous silicon carbide (RPSC) ceramics with different open porosities was studied in dry oxygen between 1200 and 1500oC. RPSC ceramics exhibited a rapid mass increase in the initial stage of oxidation and a slow mass increase in the following oxidation. This oxidation behavior of RPSC is more plausible to be represented by an asymptotic law rather than the parabolic law for dense SiC. The porosity of RPSC led to dominant internal oxidation mass gain in pore channels at the beginning of oxidation besides surface oxidation. The oxidation mass gain was proportional to the amount of the porosity. As the oxide growth rate near the pore mouth was much faster than the rate of oxygen supply to the interior of the pores, the pores were blocked by silica rapidly, which subsequently prevented the further oxidation of the inner pores.