YANG Mengmeng ¹, LUO Xudong ^1,2, XIE Zhipeng ², YU Min ¹, ZHANG Xiaofang ¹
(1. School of High Temperature Materials and Magnesium Resource Engineering, University of Science and Technology Liaoning, Anshan 114051, Liaoning, China; 2. State Key Lab of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China)

Abstract: High purity mullite powder was prepared by co-precipitation method. Starch and AlF₃ were doped to prepare the self-locking structure of porous ceramics consisting of in situ generated mullite whiskers. The bulk density, apparent porosity and bending strength were tested. The effects of AlF₃ on the microstructure and strength of the sample were investigated. Phase compositions and microstructures of the sintered samples were measured by XRD and SEM, respectively. The results show that the addition of AlF₃ was helpful for the formation of mullite whisker. The whisker reached the maximum length to diameter ratio of 26.28 when the sample was prepared with 2wt.%AlF₃ as an additive. Mullite flakes were observed when excessive AlF₃ was added to the sample. The in situ synthesized mullite whiskers formed an interlocking structure, which improved the mechanical strength of the porous mullite ceramics. The porous mullite ceramics had the bending strength of about 98.58 MPa when prepared with 2wt.% AlF₃.

Key words: mullite; whisker; porous ceramic; self-lock structure