Papers by Author: Xin Yan Yue

Abstract: SiC-TiB2 composite was prepared at 2298 K by using pressureless sintering. The microstructures and mechanical properties of the SiC-TiB2 composite were investigated. The SiC-TiB2 composite with 5 mass % B4C-C showed the optimized comprehensive properties. The volume density, hardness, flexural strength and fracture toughness of that were 3.43 g/cm3, 18.5 GPa, 353 MPa and 4.67 MPa•m1/2, respectively. The excessive B4C-C content might decrease the mechanical properties of the composite.

Abstract: MgO substituted polycrystalline BaTi₂O₅ (BT₂), Ba_1-xMgxTi₂O5 (BMT₂), was prepared by a floating zone method (FZ-melting). The dielectric property of BMT₂ was investigated by_{Subscript text} an AC impedance method. At x = 0.005 MgO, the permittivity (r) showed the maximum value of 5800 for FZ-melted specimens. The Curie temperature (T_c) decreased with increasing x and the permittivity showed a flat peak at x ≥ 0.03. Second phases of BaTiO₃, Ba₆Ti17O40 and Ba4MgTi11O27 were identified in polycrystalline BMT2. BaTiO3 and Ba6Ti17O40 could be due to the decomposition of BT2 at high temperatures.

Abstract: Gp/SiC composite was prepared with electrode graphite particle and SiC powders as the raw materials, using coating process and hot-pressing sintering technology. The microstructure and phase constitution was measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron energy spectrum (EDS). It was found that the graphite cores are embedded in the SiC matrix as the islands. The apparent porosity increased, density decreased, with graphite particle content increasing, the bending strength decreased, however, fracture toughness increased with the graphite particle content increasing. Increasing hot-pressing sintering temperature imparted Gp/SiC composite characteristic behaviors of better mechanical strength. The apparent porosity, bulk density, bending strength, fracture toughness were 4.0%, 2.58 g•cm-3, 50 MPa, 6.3 MPa•m1/2, respectively, with the size 200 μm graphite core at 2050 °C, while the volume rate of SiC and graphite was 6:4.

Abstract: B4C-TiB2 composite was prepared using hot pressure sintering. The microstructures and mechanical properties of the B4C-TiB2 composite were investigated. The B4C-TiB2 composite with 43 mass % TiB2 showed the optimized properties. The relative density, hardness, flexural strength and fracture toughness of that were 98.2 %, 25.9 GPa, 458 MPa and 8.7 MPa•m1/2, respectively. A number of toughening mechanisms, including fine grain, crack deflection and grain pull-out, were observed during microstructural analysis of the composite. The fracture mode of the B4C-TiB2 composite was greatly affected by the existence of the second phase of TiB2.