Effects of pyrolusite additive on the microstructure and mechanical strength of corundum–mullite ceramics

Corundum–mullite ceramics have been successfully synthesized by using the raw materials of bauxite and kaolin clay. The effects of pyrolusite additive on the microstructure and mechanical strength of the corundum–mullite duplex ceramics were systematically investigated. The results show that the duplex ceramics exhibit the optimal performance with the amount of 4 wt% additives at 1350 °C. The liquid glass phases appear during the sintering process due to the presence of the impurities in pyrolusite powder, which is beneficial to the growth of crystal, the gap decrease of grain boundary and pores, and the improvement of compressive strength. Moreover, the component of MnO2 could lead to the distortion of lattice, and further improve the mechanical strength via a solid solution strengthening mechanism.