THERMAL-SHOCK PROPERTIES OF SIC WHISKER-REINFORCED SILICON-NITRIDE CERAMICS

Improvement in the thermal shock durability of the hot-pressed silicon nitride with Y2O3 and Al2O3 as sintering aids by incorporation of silicon carbide whiskers was carefully investigated. Using a standard bending specimen in size of 3x4x40mm, the thermal shock durability was evaluated by water quenching method. As a measure of the thermal shock durability, the quenching temperature defference, Delta T, was larger than 1000 degrees C for the materials incorporated with silicon carbide whiskers. On the other hand, the silicon nitride ceramics without whiskers exhibited Delta T=600 degrees C. The improvement of the Delta T due to incorporation of whiskers was discussed on the factors affecting to the thermal shock durability such as strength, Young's modulus, Poisson's ratio, thermal expansion coefficient and thermal conductivity.