The Effects of BN Addition on the Mechanical Properties of Porous Si3N4/BN Ceramics Prepared Via Nitridation of Silicon Powder

Porous Si3N4/BN ceramics were prepared via nitridation of silicon powder, with Si and BN as starting powder, Y2O3 as sintering additive. After nitridation and sintering at 1680 degrees C, porous Si3N4/BN ceramics with a porosity of 47%-51% and a flexural strength of 170-90 MPa were obtained. Compared with pure porous Si3N4 ceramics, the grains of porous Si3N4/BN ceramics were finer, the aspect ratio of beta-Si3N4 grains was higher, and the pore size was decreased, which can be attributed to grain-boundary pinning due to BN dispersions. The relatively high flexural strength was obtained with 5% BN addition. The porous Si3N4/BN ceramics also showed low shrinkage and machinable properties.