Effect of particle size of associated rare earth kaolin powder on the sintering and properties of synthetic mullite

Abstract The objective of this work is to synthesize mullite from associated rare‐earth kaolin. The effects of 300 mesh (48 μm) and 400 mesh (38 μm) associated rare earth kaolin and sintering temperature on the phase composition, microstructure, sintering behavior, and mechanical properties of mullite were studied. The study showed that the relative mullite content, average aspect ratio, relative density, micro Vickers hardness, and flexural strength of mullite synthesized by using 400‐mesh calcined associated rare earth kaolin as raw material and sintered at 1500°C for 4 h were 76.6%, 5.55 μm, 90.19%, 12.05 GPa, and 166.35 MPa, respectively. Compared with mullite synthesized from 300‐mesh calcined associated rare earth kaolin, the use of 400‐mesh associated rare earth kaolin can reduce the mullitization temperature by about 100°C, increase the average aspect ratio and relative density of mullite by 5.23% and 9.47%, and increase the microscopic Vickers hardness and flexural strength by 6.09% and 17.04%, respectively. This provides new ideas for the comprehensive utilization of associated rare earth kaolin mineral resources and new ways for the high value‐added utilization of associated rare earth kaolin, which has great economic value.