BENEFICIAL EFFECT OF ALUMINUM ON THE OXIDATION BEHAVIOR OF PRECURSOR-DERIVED CERAMICS

摘要

The oxidation behavior of precursor derived SiBCN and SiBCNAl ceramics was investigated at 1500℃ in dry oxygen. Oxide scale growth rates on the SiBCN material were comparable to CVD-SiC. The scales, which were largely amorphous after short oxidation times, showed cracking and partial spalling. Oxidation times of 24h and greater, lead to the beginning of crystallization of the scales, which was accompanied by bubble formation. The addition of aluminum increased the scale growth rate, but the scale quality was significantly improved. Even after oxidation for 100h at 1500℃, all scales were dense, largely amorphous, and crack-free with a perfect adhesion to the substrate. Bubble formation as a result of crystallization was not observed.