Investigation of the oxidation mechanism of Si-Al2O3-fused mullite containing Ti2O3 composite

In this work, Si-Al2O3-fused mullite containing Ti2O3 composite was prepared and heat-treated at 1100 °C, 1300 °C and 1500 °C for 3 h respectively in an air atmosphere to explore its oxidation mechanism. The results show that the Si-Al2O3-fused mullite containing Ti2O3 composite has excellent oxidation resistance at evaluated temperatures. The reason for this is the formation of a complete oxide layer and a transition layer in the exterior to absorb and filter O2, allowing the interior without oxidation. The oxidation of Si and Ti2O3 in the exterior is accompanied by volume expansion. SiC and mullite are formed in the transition layer at 1300 °C. At 1500 °C, SiO2, mullite and Si2N2O are formed in the transition layer. O′-Sialon and Ti(C, N)ss are formed in the interior of the samples at both 1300 °C and 1500 °C. At 1100 °C, Si oxidizes to form SiO2 coating on the surface of Si particles. The industrial CT characterization of the pore evolution of the samples after oxidation is consistent with the oxidation mechanism. A reaction model is developed.