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2005  Volume 37 

The Effect of Oxygen Introduction on Oxidation Resistance of Si3N4 Ceramics (2nd Report)
Mituyoshi NAGANO, Kokoro GOTO, Hideaki SANO, Shigeya SAKAGUCHI, Yasuo UCHIYAMA
Key words Si3N4 ceramics, oxidation, sintering, powder, Al2O3 , solid solution,


The first report in 2001 Nippon Tungsten Review(NTR), Si3N4 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 Al2O3 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 1200 and 1400°C. Though mass change could hardly be seen below 1300°C, it was observed remarkably at 1400°C. In isothermal oxidation at 1400°C, as the amount of Al2O3 increased from 2mass% to 4mass%, 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 600 and 1000°C, in order to clear the behavior of the oxidation resistance between temperature of 1200 and 1400°C. 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 1000°C or lower.
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