Fabrication of Si3N4/SiC Composite by Reaction-Bonding and Gas-Pressure Sintering |
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Authors: | Soo Young Lee |
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Affiliation: | Korea Institute of Machinery and Materials, Changwon, Kyungnam, Korea |
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Abstract: | Si3N4/SiC composite materials have been fabricated by reaction-sintering and postsintering steps. The green body containing Si metal and SiC particles was reaction-sintered at 1370°C in a flowing N2/H2 gas mixture. The initial reaction product was dominated by alpha-Si3N4. However, as the reaction processed there was a gradual increase in the proportion of β-Si3N4. The reaction-bonded composite consisting of alpha-Si3N4, β-Si3N4, and SiC was heat-treated again at 2000°C for 150 min under 7-MPa N2 gas pressure. The addition of SiC enhanced the reaction-sintering process and resulted in a fine microstructure, which in turn improved fracture strength to as high as 1220 MPa. The high value in flexural strength is attributed to the formation of uniformly elongated β-Si3N4 grains as well as small size of the grains (length = 2 μm, thickness = 0.5 μm). The reaction mechanism of the reaction sintering and the mechanical properties of the composite are discussed in terms of the development of microstructures. |
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