METHOD OF MANUFACTURING HIGH DENSITY SILICON NITRIDE HAVING HIGH TEMPERATURE STRENGTH AND ANTIIOXIDATION AND CONTAINING Y203 AND AL203

摘要

The addition of controlled amounts of Al2O3 to high purity Si3N4 powder (containing less than 0.1 weight percent cation impurities and containing Y2O3 as a densifying additive) enables shorter sintering times to achieve polycrystalline Si3N4 bodies having densities approaching theoretical density, while a postsintering crystallization heat treatment results in strengths at high temperatures not otherwise obtainable in the presence of Al2O3. Resulting Si3N4 bodies are useful as engine parts and components or a regenerator or recuperator structures for waste heat recovery. In addition, such Si3N4 bodies containing Al2O3 exhibit good oxidation resistance.