低酸素濃度雰囲気で加熱されたSiCセラミックスの酸化挙動に及ぼす既成シリカ保護膜の影響

概要

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Oxidation behavior of SiC ceramics protected by preformed silica layer on exposure to Ar-O_2 atmosphere with P_<O_2> in the active oxidation range (0.02 kPa) was surveyed to investigate whether Gulbransen's theory predicting the transitional P_<O_2>, between active and passive oxidation behavior is adaptable also to well-passivated ceramics. Here, high-purity SiC was selected as a testing sample to avoid the influence of impurities on its oxidation behavior. A silica layer thicker than 0.2 μm played a role of protection during soaking at 1700 K for 10h at P_<O_2>=0.02 kPa. Zero weight change observed during the soaking treatment of the passivated sample suggested the simultaneous formation of SiO_2(2/3) and SiO (1/3) from SiC accompanied by a the volume increase, which would result in the absence of cavities at the silica/SiC interface. It was pointed out that at least minor correction should be done in Gulbransen's theory in the case of well-passivated SiC ceramics.
社団法人日本セラミックス協会の論文
1997-11-01