Preparation and Thermal Shock Resistance of Mullite and Corundum Co-bonded SiC Ceramics for Solar Thermal Storage

Mullite and corundum co-bonded SiC-based composite ceramics (SiC-mullite-Al2O3) were prepared by using SiC, calcined bauxite and kaolin via pressureless carbon-buried sintering. The low-cost SiCbased composite ceramics designed in this study are expected to be used as thermal storage materials in solar thermal power generation based on the high density and excellent thermal shock resistance. The influences of calcined bauxite addition and sintering temperature on the microstructures, phase compositions, and physical properties of the samples were investigated. Results demonstrated that the introduction of calcined bauxite containing two bonding phases greatly reduced the lowest sintering temperature to 1 400 °C. The SiC-mullite- Al2O3 composite with 40 wt% calcined bauxite sintered at 1 500 °C exhibited optimum performance. The density and bending strength were 2.27 g·cm−3 and 77.05 MPa. The bending strength increased by 24.58% and no cracks were observed after 30 thermal shock cycles, while general clay would reduce the thermal shock resistance of SiC. The SiC-mullite-Al2O3 composites with satisfied performance are expected to be used as thermal storage materials in solar thermal power generation systems.