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.
Highlights
Hexagonal boron nitride/silicon carbide (h-BN/SiC) ceramic composite is an useful structural material possessing The advantages of hexagonal boron nitride (h-BN) ceramic, such as The high thermal conductivity and high chemical stability of h-BN [1,2,3,4,5], as well as The advantages of SiC, such as high temperature mechanical properties, ablation resistance, excellent thermal and semiconductor characteristics [6,7,8,9], which is used for thermocouple protection tubes, casting side dams, and heat sinks for semiconductor parts [10,11]
The h-BN/SiC ceramics were fabricated by spark plasma sintering (SPS) at 1600 ◦ C for 5 min under
The h-BN/SiC ceramics were fabricated by spark plasma sintering (SPS) at 1600 °C for 5 min
Summary
Hexagonal boron nitride/silicon carbide (h-BN/SiC) ceramic composite is an useful structural material possessing The advantages of h-BN ceramic, such as The high thermal conductivity and high chemical stability of h-BN [1,2,3,4,5], as well as The advantages of SiC, such as high temperature mechanical properties, ablation resistance, excellent thermal and semiconductor characteristics [6,7,8,9], which is used for thermocouple protection tubes, casting side dams, and heat sinks for semiconductor parts [10,11]. There are few reports concerning The microstructure and its effects on The heating rate by microwaves of such material. In order to obtain a relative high density, h-BN/SiC ceramic is usually sintered by hot pressing and spark plasma sintering (SPS). The hot pressing method is often done at a high temperature, about 1900 ◦ C [16], and The h-BN grains grow rapidly, which leads to decrease of The fracture strength of ceramic. With low sintering temperatures of about 1600 ◦ C [17], SPS is used to achieve fine grains that improve The mechanical properties. The effect of SiC content on relative density, microstructure, hardness, and especially The heating rate of ceramics in microwave fields were investigated
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