ZHANG Ling ¹, HUANG Jingyin ¹, HE Yu ¹, LIU Kaige ¹, XIAO Zhuohao ^{2, 3}, ZHOU Chaolan ^1, ZENG Shaozhong ¹, XIANG Bingxi ¹, ZHAI Jianpang ¹, KONG Lingbing ¹

(1. College of New Materials and New Energies, Shenzhen Technology University, Shenzhen 518118, Guangdong, China; 2. School of Materials Science and Engineering, Jingde zhen Ceramic Institute, Jingdezhen 333403, Jiangxi, China; 3. Jiangxi Guanyi Grinding Co., Ltd., Fengxin 330700, Jiangxi, China)

Abstract: Porous mullite ceramics were fabricated by using high-energy ball milling and solid state sintering with Al₂O₃ and SiO₂ as the main raw materials and ZnO (0-37.5 mol%) as an additive. The effects of ZnO and sintering temperature on phase formation, microstructure evolution, thermal expansion, bulk density and porosity of the porous mullite samples were examined. The results show that ZnO has a positive effect on the phase formation and anisotropic grain growth of mullite. The formation temperature of mullite phase is 1300 ℃ in samples doped with 37.5 mol% ZnO, which is nearly 100 ℃ lower than samples without ZnO doped, and the size of anisotropic grain increases. The porosity of the as-prepared porous ceramics increases, while the linear shrinkage and bulk density decrease with ZnO increasing from 0 mol% to 37.5 mol%. When the content of ZnO is 37.5 mol% , the linear shrinkage and bulk density of the porous ceramics samples are 1.59% and 1.96 g/cm3, with the maximum porosity of 45.54%, after sintering at 1500 ℃. This method provides a new approach for the preparation of porous mullite ceramics without pore-forming agent.

Key words: mullite; ZnO; porous ceramics; high-energy ball milling; grain growth; densification; microstructure