ELASTIC PROPERTIES OF SILICON OXYNITRIDE

Silicon oxynitride is a refactory material which appears to exhibit good mechanical and thermal properties. This work studies the elastic properties of hot-pressed samples with an addition of 5 wt% MgO. The samples are isotropic and homogeneous, and the three different methods of measurement used, operating in the frequency range 20 kHz to 10 MHz, give similar results. Young's modulus and shear modulus are low (about 22×1010 Pa and 9×1010 Pa, respectively), which leads to small thermal stresses and thus allows a good thermal shock resistance. The elastic moduli decrease linearly when the porosity increases over the range of 0 to 27%. Poisson's ratio is sensibly a constant equal to 0.2, and the rate of variation is the same for both moduli: 2.5, this value being superior to what could be expected from the usual theories. © 1979 Chapman and Hall Ltd.