Oxidation Behavior of Hot-Pressed Si3N4 |
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| Authors: | A. J. KIEHLE L. K. HEUNG P. J. GIELISSE T. J. ROCKETT |
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| Affiliation: | University of Rhode Island, Kingston, Rhode Island 02881 |
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| Abstract: | The high-temperature chemical stability of hot-pressed Si3N4 was studied between 600° and 1450°C. Reactions were followed by X-ray diffraction and scanning electron microscopy. In air, this material begins to oxidize at 700° to 750°C; a distinct amorphous siO2 surface layer results after 24 h at 750°C-Concomitant formation of cristobalite occurs, depending on exposure time, and is enhanced as temperature is Increased. Magnesium and calcium magnesium silicates form above 1000°C. The data suggest that impurities, e.g. Mg, Ca, and Fe, greatly lower the oxidation resistance of Si3N4 in air. |
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