Oxidation of sintered silicon nitride |
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Authors: | Chuan He Ling Wang Jianguang Wu |
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Affiliation: | (1) Department of Materials Science and Engineering, Tsinghua University, 100084 Beijing, People's Republic of China;(2) Present address: Ceramic Division, National Institute of Standards and Technology, 20899 Gaithersburg, MD, USA |
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Abstract: | The influence of oxidation at 1200 °C in air for up to 1000 h on the mechanical properties of two Si3N4-Y2O3-Al2O3 materials with different Y2O3/Al2O3 ratios, Material A (Si3N4-13.9 wt% Y2O3-4.5 wt% Al2O3) and Material B (Si3N4-6.0 wt% Y2O3-12.4 wt% Al2O3), was investigated. The oxidation significantly improves the high-temperature strength and fracture toughness of both materials, but more for Material A. After oxidation, Material A at 1300 °C retains 93% of its room-temperature strength and 87% higher than that before the oxidation. The oxidation has a different effect on the room-temperature K
IC for the two materials. The room-temperature Weibull modulus of Material A decreased by more than half while the 1200 °C Weibull modulus decreased slightly after oxidation. The annealing treatment prior to oxidation had no effect on the high-temperature strengths of the materials after oxidation. The effect of oxidation on mechanical properties is discussed in terms of the microstructure change of the materials. |
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