Microstructure and fracture strength of silicon nitride ceramics consolidated by oscillatory pressure sintering

摘要

Oscillatory pressure sintering (OPS) technique is considered as a promising approach in the preparation of structural ceramics. In this study, the influence of oscillatory pressure on the grain growth, grain boundary characters and mechanical behaviors of silicon nitride ceramics was investigated. The TEM analysis indicated fringes in the grains and Moire' patterns at the grain boundaries of the OPS specimen. In addition, the OPS specimen presented a coarse structure resulted from the accelerated diffusion of atoms in liquid phase at high temperature. Based on these microstructure evolutions, the fracture work of the OPS specimen increased from 835 to 1240 J/m(2) and the Weibull modulus of flexural strength increased from 23.9 to 35.9 when compared with that of the hot-pressed specimen.