The Effect of Oxygen Introduction on Oxidation Resistance of Si_3N_4 Ceramics (2nd Report)

摘要

The first report in 2001 Nippon Tungsten Review(NTR), Si_3N_4 ceramics used in this study were introduced to oxygen during preparation by three different methods; 1) pre-oxidation of raw powder, 2) sintering in different atmospheres, and 3) controlling the amount of A1_2O_3 to be added as a sintering additive. Their oxidation behavior in terms of change in mass, morphological surface composition and cross-section of the specimen was studied between temperature of 1473 and 1673 K. Though mass change could hardly be seen below 1573K, it was observed remarkably at 1673K. In isothermal oxidation at 1673K, as the amount of A1_2O_3 increased from 2mass percent to 4rnass percent, the mass of the specimen also increased. So that it was recognized to be necessary to analyze the beginning of the oxidation resistance between temperature of 873K and 1273K, in order to clear the behavior of the oxidation resistance between temperature of 1473K and 1673K. In this report, there was a trend that the oxidation of specimens with less introduced oxygen began earlier than that of specimens with more introduced oxygen at 1273K or lower.