Study on mullitization of sillimanite group minerals and its effect on properties of the Al2O3-SiC-C gunning material

This study aimed to compare and summarize the mullitization mechanism of the sillimanite group minerals and investigated its effect on the mechanical properties of Al₂O₃-SiC-C gunning materials. By comparing the phase composition and microstructure of kyanite, andalusite, and sillimanite at different temperatures, the mullitization mechanism of sillimanite group minerals was clarified. Furthermore, the Al₂O₃-SiC-C gunning materials with sillimanite group minerals addition were prepared by bauxite and fused brown corundum as aggregates, fused white corundum (≤0.045 mm), SiC (≤0.075 mm), α-Al₂O₃ (≤10 µm), pitch sphere, SiO₂ micropowder (≤2 µm) as a matrix, and silica sol as a binder. Then, the effect of the addition of sillimanite group minerals on the mechanical properties of Al₂O₃-SiC-C gunning materials was characterized. The results indicate that kyanite requires the lowest temperature for mullitization compared to andalusite and sillimanite. The mullitization process involves the migration of Al³⁺ and Si⁴⁺, resulting in a decrease in the lattice constant of sillimanite group minerals followed by the production of mullite and SiO₂. Incorporating sillimanite group minerals into Al₂O₃-SiC-C gunning materials effectively controls their linear change rate after firing while enhancing their mechanical properties. Notably, the addition of kyanite yields superior performance in Al₂O₃-SiC-C gunning materials.