Abstract
ABSTRACTThe effect of oxygen content of silicon nitride powders on the properties of resulting ceramics was studied by physically and chemically treating the powder to modify its surface oxygen content. These powders were compounded with yttria and hot-pressed into dense ceramics. Strength and oxidation resistance of these ceramics were measured and correlated with the powder and ceramic compositions as well as the resulting intergranular phases. Results showed that the phases varied with slight differences in the initial powder oxygen content as predicted, and that strength could be correlated to initial oxygen concentration. Best results were obtained when the oxygen content was increased by thermal oxidation. A Taguchi Methods experimental study designed to optimize the thermal treatment resulted in silicon nitride ceramics with strength improvements of 22 and 37% at ambient temperature and 1370°C, respectively. Oxidation resistance was also improved.
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