High temperature physical vapor transport(HTPVT) was employed to grow polycrystalline SiC ceramics with high density and purity, induced by nano SiC particles as seeds. The obtained SiC ceramics were identified as 6 H...High temperature physical vapor transport(HTPVT) was employed to grow polycrystalline SiC ceramics with high density and purity, induced by nano SiC particles as seeds. The obtained SiC ceramics were identified as 6 H-SiC with a mainly preferred orientation along the(0 0 0 6) plane, and an obvious refinement of grain size was demonstrated for the SiC seeds. Mean grain sizes of the obtained SiC ceramics were112 μm and 314 μm, by using the SiC seeds with the mean particle size of 50 nm and 500 nm, respectively,which were obviously smaller than that of the seed-free sample(960 μm). The samples obtained with the seeds also demonstrated enhanced flexural strength and hardness, attributing to the reduced mean grain size. Furthermore, SiC ceramics without seeds via HTPVT exhibited a high thermal conductivity of242 W·(m·K)^-1 at room temperature due to the highly preferred orientation. While the degree of preferred orientation of seed-induced samples was lower, the thermal conductivity of SiC ceramics induced by seeding still maintained at least 200 W·(m·K)^-1 at room temperature, this level was much higher than most other methods. Therefore, seed-induced method appears to be an effective way to control structures and behavior of SiC ceramics through HTPVT.展开更多
基金supported by the National Natural Science Foundation of China (NSFC, grant No. 51672209)the National Key R&D Program of China (Grant No. 2017YFB0310300)the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2016JQ5046)
文摘High temperature physical vapor transport(HTPVT) was employed to grow polycrystalline SiC ceramics with high density and purity, induced by nano SiC particles as seeds. The obtained SiC ceramics were identified as 6 H-SiC with a mainly preferred orientation along the(0 0 0 6) plane, and an obvious refinement of grain size was demonstrated for the SiC seeds. Mean grain sizes of the obtained SiC ceramics were112 μm and 314 μm, by using the SiC seeds with the mean particle size of 50 nm and 500 nm, respectively,which were obviously smaller than that of the seed-free sample(960 μm). The samples obtained with the seeds also demonstrated enhanced flexural strength and hardness, attributing to the reduced mean grain size. Furthermore, SiC ceramics without seeds via HTPVT exhibited a high thermal conductivity of242 W·(m·K)^-1 at room temperature due to the highly preferred orientation. While the degree of preferred orientation of seed-induced samples was lower, the thermal conductivity of SiC ceramics induced by seeding still maintained at least 200 W·(m·K)^-1 at room temperature, this level was much higher than most other methods. Therefore, seed-induced method appears to be an effective way to control structures and behavior of SiC ceramics through HTPVT.
