Microstructure control and mechanical properties of porous silicon nitride ceramics

Porous silicon nitride ceramics with a fibrous interlocking microstructure were synthesized by carbothermal nitridation of silicon dioxide. The influences of different starting powders on microstructure and mechanical properties of the samples were studied. The results showed that the microstructure and mechanical properties of porous silicon nitride ceramics depended mostly on the size of starting powders. The formation of single-phase β-Si3N4 and the microstructure of the samples were demonstrated by XRD and SEM, respectively. The resultant porous Si3N4 ceramics with a porosity of 71% showed a relative higher flexural strength of 24 MPa.