Effect of Nano SiC on Microstructure and Mechanical Properties of BN-ZrO2-SiC Multiphase Ceramics

Abstract:

h-BN-ZrO₂-SiC multiphase ceramics were prepared rapidly by spark plasma sintering (SPS) with h-BN, ZrO₂ and SiC powders as raw materials and 8%(Al₂O₃+Y₂O₃) as sintering aids. The effects of nano SiC content on the densification, microstructure and mechanical properties of h-BN-ZrO₂-SiC multiphase ceramics were systematically investigated. The results show that the addition of nano SiC particles can effectively promote the sintering and increase density and mechanical properties of the sintered samples at a low sintering temperature. The flexural strength, fracture toughness and elastic modulus all increase with the content increase of nano SiC, especially, the increasement of the elastic modulus is obvious. The comparison of all results shows that the sample with the SiC content of 25% has optimal mechanical properties than other samples, and the flexural strength, fracture toughness and elastic modulus are 268.4 MPa, 3.24 MPa.m_1/2 and 115 GPa, respectively. The reason is mainly due to the nano SiC particles can better play a gap filling, dispersion strengthening and grain boundary pinning effect than ZrO₂, which are beneficial to improve the bonding strength between the phases and reduce the residual stress due to thermal mismatch. As a result, the more fracture energy was absorbed during the crack propagation process, and the flexural strength and fracture toughness increased.