Effects of AlF3 and MoO3 on properties of Mullite whisker reinforced porous ceramics fabricated from construction waste

Mullite-whisker-reinforced anorthite-mullite-corundum porous ceramics were prepared from construction waste and Al2O3 powder by adding AlF3 and MoO3 as the additive and crystallization catalyst, respectively. The effects of AlF3 and MoO3 content on the properties of mullite whiskers, such as open porosity, mechanical properties, pore size distribution, microstructure and phase structure, were investigated in detail. The results showed that the morphology of the mullite whiskers and properties of the porous ceramics were greatly influenced by the AlF3 and MoO3 content. The specimen obtained by co-adding 12 wt% AlF3 and 3 wt% MoO3, and sintering at 1350 °C for 1 h, exhibited excellent properties, including an open porosity of 67.4±0.5% and biaxial flexural strength of 24.0±0.8 MPa. The mullite whiskers were uniformly distributed; the whiskers had a diameter of 0.05-0.5 µm, length of 8-10 µm, and aspect ratios (length to diameter ratio) of 20-30 on average.