Fundamental Research for Fabrication and Application of high hardness Materials with Nano Size Grain Boundary at high temperature

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In this study, the fabrication and application research of Si-B-C system composite were investigated, to confirm whether the high temperature properties of SiB6 containing carbon ceramics can be improved. The samples were sintered by hot pressing in the simultaneous presence of carbon, in order to investigate the effects on properties of the sintered composites. It was found that the relative density of SiB6 with C sintered bodies became good densification at 1973 K for 1 hour in vacuum under a pressure of 25 MPa. The porosity of SiB6 containing 0, 5, 10, 15, and 20 mass% C sintered bodies was 1.0 %, 1.5 %, 2.8 %, and 20 %, respectively. Based on the XRD analysis results, the sintered composites exhibited diffraction peaks considered to be relevant to B4C and SiC, in addition to those relevant to SiB6, However, the diffraction peaks for C disappeared, and those for B4C and SiC. The Vickers hardness of the SiB6 with 10 mass % C composite was 28 and 22 GPa at room temperature and 1073 K, respectively. The hardness of the composite did not decrease with increasing measurement temperature. The Vickers hardness at high temperature of SiB6 addition of 10 mass% C composite was higher than Al2O3, ZrO2, and Si3N4 sintered bodies.