Effect of MoO3 addition on fly ash based porous and high-strength mullite ceramics: In situ whisker growth and self-enhancement mechanism

In this paper, using only high alumina fly ash as raw material and MoO3 as additive agent, the high-strength porous mullite ceramics were achieved by in situ mullite whisker growth via a calcination method. The influence of MoO3 addition on pore structure and mechanical properties of as-prepared mullite ceramics was investigated. The mechanism of MoO3 promoting the formation of mullite whiskers and improving the strength of matrix was elucidated. The porous mullite ceramic reached its best performance with a high porosity of 49.4% and an improved compressive strength of 13.03 MPa with 10 wt% MoO3 addition calcinated at 1300 °C. Specifically, MoO3 facilitated the mullite whisks growth mainly by reducing melting point of amorphous SiO2/quartz and changing crystal structure of Al2O3. The larger aspect ratio of mullite grain at 1300 °C was easier to form an interlocking structure, which enhanced the strength of mullite ceramic while maintaining high porosity.