Porous acicular mullite obtained by controlled oxidation of waste molybdenum disilicide

Porous acicular mullite was fabricated by using waste MoSi2 heating element and Al2O3. Careful calcination of the pulverized heating element led to the formation of a mixture of MoO3 and amorphous SiO2. This mixture was employed as both SiO2 precursor and pore former. The oxidation of MoSi2 and mullite formation were studied. The effect of fabrication temperature on phase composition, porosity, grain morphology, and compressive strength of sintered mullite was examined. Pure mullite with porosity of more than 60% and compressive strength of ∼20 MPa was obtained at temperature as low as 1300 °C. The microstructure consisted of elongated, rectangular, prism-like grains which are known to be effective in filtration of diesel engine exhaust. The increase in sintering temperature caused the change of grain morphology and reduction in compressive strength.