Elastic properties of engineering ceramics at elevated temperature

Abstract

Young's modulus and internal friction of engineering ceramics such as silicon nitride, silicon carbide and tetragonal zirconia polycrystals were measured by the resonance method up to 1400°C. Effect of hanging position on the apparent value of Young's modulus and internal friction was investigated. The apparent value of internal friction increased when the specimen is hung near the edge of the specimen because of the loss of vibration by the equipments. The error of apparent value of internal friction was negligibly small if the shift of hanging position from the node is less than 2.4% of the total length of the specimen. Measured value of Young's modulus was independent of hanging position. Internal friction increased abruptly above 1150°C in hot-pressed silicon nitride, above 1000°C in pressureless sintered silicon nitride and tetragonal zirconia polycrystals with increasing temperature. Internal friction showed peaks at 1080°C in hot-pressed silicon nitride, at 600°C in silicon carbide and at 180°C in tetragonal zirconia polycrystals. All of these temperatures corresponded to the temperatures at which Young's modulus decreased.