Effect of MnO2 on properties of SiC-mullite composite ceramics for solar sensible thermal storage

For improving the properties of SiC-mullite composite ceramics used for solar sensible thermal storage, MnO2 was introduced as sintering additive when preparing. The composite ceramics were synthesized by using SiC, andalusite, α-Al2O3 as the starting materials with non-contact graphite-buried sintering method. Phase composition and microstructure of the composites were investigated by XRD and SEM, and the effect of MnO2 on the properties of SiC composites was studied. Results indicated that samples SM1 with 0.2 wt% MnO2 addition achieved the optimum properties: bending strength of 70.96 MPa, heat capacity of 1.02 J·(g·K)-1, thermal conductivity of 9.05 W·(m·K)-1. Proper addition of MnO2 was found to weaken the volume effect of the composites and improve the thermal shock resistance with an increased rate of 27.84% for bending strength after 30 cycles of thermal shock (air cooling from 1 100 °C to RT).