Ta2O5 induced aligned growth of mullite achieving superior wear resistance properties

Coal-series kaolin (CSK), a large-scale solid waste, has caused significant environmental pollution. Its effective conversion into high-value products remains a challenge. In this study, mullite-based ceramics featuring needle-like microstructures were controllably prepared by adding Ta 2 O 5 without the need for additional sintering acids. The resulting ceramics exhibited superior wear resistance. Ta 2 O 5 reacts with Al 2 O 3 to form Ta-O-Al chemical bridges. Combined with density functional theory (DFT) calculations and experimental data, these chemical bridges effectively lower the nucleation energy barrier for new crystalline phases and provide anchoring sites. This drives the transition from equiaxed grains to interwoven whiskers and facilitates the preferential one-dimensional anisotropic growth of the mullite phase. Due to the distinctive needle-like mullite microstructures and the pinning effect of AlTaO 4 , the wear rate decreases by 89% compared to the blank sample. These results demonstrate that Ta 2 O 5 regulates the crystal growth and friction behavior of mullite, offering an economically effective strategy for utilizing CSK.