Thermo-mechanical properties of ceramics: Resistance to initiation and propagation of crack in high temperature

Dense silicon nitride is investigated to determine the effect of its microstructural parameters and densification on thermo-mechanical properties as well as its thermal stress resistance to fracture initiation during a hot or cold mechanical and thermal shock testing. The different materials and microstructures are obtained by changing the parameters such as the type of the powder, additive, forming process and sintering condition. The maximum crack growth and thermal shock resistance of dense Si3N4 is achieved for the materials with higher toughness having a thick elongated grain with high aspect ratio dispersed in matrice of relatively coarse and equiaxed grains and higher grain phase boundary (glassy phase) by mechanism of pull-out and recovery of crack.