Microstructural composite mullite derived from oxides via a high-energy ball milling process

High-energy ball milling had a great influence on phase formation and morphology development of mullite derived from oxide precursors. Mullite phase was formed at 1300 °C in an oxide mixture of Al2O3 and quartz without high-energy ball milling and the mullitization was not complete up to 1500 °C. After milling for 5 h, the mullitization temperature was reduced by about 200 °C. At the same time, mullite whiskers were obtained. Based on these results, microstructural composite mullite ceramics were proposed to be made from the mixtures of the oxide precursors with and without the high-energy ball milling. The unmilled precursor was sintered to equiaxed grains while the milled one resulted in anisotropic grains. The relative proportion of the equiaxed and anisotropic grains could be readily adjusted by the precursor mixtures. Moreover, the mullite crystallites coming from the milled precursor powder at low temperature acted as seeds to enhance the mullite phase formation of the composites. It is believed that the mullite whiskers produced in this way can also be used as reinforcing components to design structural composites of others materials.