Mullite Reinforced SiC/Al2O3 Composites Prepared by Microwave Sintering Based on Green Manufacturing

In the preparation process of composites, the implementation of green manufacturing technology has an important impact on improving material properties and preparation efficiency. The adopting of green manufacturing technology not only greatly reduces the energy consumption but also effectively avoids the environmental pollution. Compared with the traditional material preparation process, the material preparation process for green manufacturing is a new concept and idea. Microwave sintering is such an efficient, clean, and pollution-free preparation process, so it is widely used in the field of material preparation. By microwave sintering, the mullite reinforced SiC/Al2O3 composites with different SiC particle size were prepared from the composite powders composed of SiC particles coated with SiO2, by a sol-gel method and Al2O3 particles. The effect of SiC particle size on the microstructure, bulk density, fracture toughness, flexural strength, and thermal shock resistance of SiC/Al2O3 composites was studied. The bulk density, fracture toughness, and flexural strength were evaluated by the Archimedes method, single-side notched beam method, and three-point bending method, respectively. The thermal shock resistance of samples was investigated through the combination of water quenching and three-point bending methods. The results showed that with the increase of SiC particle size, the bulk density, fracture toughness, and flexural strength of samples all increased first and then decreased. The bulk density, fracture toughness, flexural strength, and flexural strength retention of SiC(5 μm)/Al2O3 composites were better than those of other samples, which were 2.06 g/cm3, 1.98 MPa·m1/2, 63 MPa, and 60%, respectively. The better mechanical properties and thermal shock resistance of SiC(5 μm)/Al2O3 composites are due to the formation of bridging mullite whiskers between SiC and Al2O3 particles with large length diameter ratio. Therefore, the unique sintering mechanisms of size coupling effect and local thermal aggregation effect in microwave sintering were discussed. The research results can not only provide reference for the preparation process of mullite reinforced SiC/Al2O3 composites but also for the wide application of microwave sintering technology.