Porous mullite-ZrO2 composites from reaction sintering of zircon and aluminum

Mullite-zirconia porous bodies were prepared by reaction sintering of zircon and alumina derived from oxidation reaction of Al at sintering temperatures between 1200 and 1600 °C. The results show that the incorporation of TiO2 improves the oxidation reaction of Al, dissociation of zircon subsequently formation of mullite and zirconia. Composites containing TiO2 obtain a high tetragonal concentration at 1500 °C, which reduces by increasing sintering temperature to 1600 °C. No tetragonal zirconia phase was detected at 1500 °C in TiO2-free composites while tetragonal concentration was increased over this temperature. The major oxidation reaction of Al proceeds with a liquid-gas mechanism that is suitable for producing low dense ceramics. In spite of the higher porosity of the composites containing TiO2, they possess almost the same flexural strength values as obtained from the TiO2-free composites.