Fig. 9. Two distinct mechanisms for the oxidation of SiC/ZrO2/mullite composites are shown. Whenf < fc, the oxygen diffusivity in the matrix is much lower than that in the silica layer, so that most of the oxygen will be consumed continuously by the SiC particles located near the surface (Fig. 9(a)); a small oxidation zone is obtained. Whenf > fc, the oxygen diffusivity in the silica layer is much lower than that in the matrix, so that oxygen will pass over the partially oxidized SiC particles and enter into the inner region, causing more SiC particles to be oxidized (Fig. 9(b)); a large oxidation zone is obtained.
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