Effect of A CaF2 addition on the oxidation of hot-pressed silicon nitride-base materials
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A hot-pressed Si3N4-10% MgO material possesses goodoxidation resistance in air at temperatures in the range 1100–1200‡C. When such a material contains an antifriction lubricant (1–20% CaF2), raising the latter's concentration increases its rate of oxidation by decreasing the viscosity of the oxide layer, which facilitates access of oxygen to the specimen surface. At CaF2 contents of more than 5% the material lacks mechanical strength owing to the formation of a thick oxide layer and appearance of cracks.
KeywordsOxidation Oxygen Silicon Viscosity Oxide Layer
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