The effect of SiC content on microstructure and microwave heating rate of h-BN/SiC ceramics fabricated by spark plasma sintering

Abstract

Hexagonal boron nitride/silicon carbide (h-BN/SiC) ceramics were fabricated by a spark plasma sintering (SPS) method. Phase and microstructure of ceramics were characterized and observed, respectively, using The X-ray diffraction, scanning electron microscope and electron probe microanalysis. The effect of molar ratios of SiC to h-BN on The microstructure, relative density, hardness, thermal conductivity, and The heating rate by microwaves on The ceramics were investigated. The results showed that The orientation of flake-like h-BN was significantly influenced by SiC content in h-BN/SiC ceramics. With The increasing of SiC content, The h-BN flakes gradually became an isotropic distribution from The preferred orientation aligning in a SPS pressure direction. The relative density of h-BN/SiC ceramics was 97.6 ± 0.9% at a molar ratio of SiC to h-BN of 40/60 mol%. The preferential orientation of h-BN flakes contributed to a relatively high thermal conductivity along The SPS pressure direction, which was beneficial to increasing The heating rate of h-BN/SiC ceramics in microwave fields.