Preparation of Al₂O₃-ZrO₂-SiO₂ ceramic composites by high-gravity combustion synthesis

By a furnace-free technique of high-gravity combustion synthesis, Al ₂O₃-ZrO₂-SiO₂ ceramic composites were prepared via melt solidification instead of conventional powder sintering. The solidification kinetics and microstructure evolution of the ceramic composites in high-gravity combustion synthesis were discussed. The phase assemblage of the ceramic composites depended on the chemical composition, where both (Al₂O₃ + ZrO₂) and (mullite + ZrO ₂) composites were obtained. The ceramic composites consisted of ultrafine eutectics and sometimes also large primary crystals. In the (mullite + ZrO₂) composites, two different morphologies and orientations were observed for the primary mullite crystals, and the volume fraction of mullite increased with increasing SiO₂ content. The ceramic composites exhibited a hardness of 11.2-14.8 GPa, depending on the chemical composition and phase assemblage.