Novel cordierite-acicular mullite composite for diesel particulate filters

Abstract

Cordierite-acicular mullite composites containing 0, 25, 50, 75 and 100 wt% of mullite were fabricated from waste MoSi 2 and commercial powders of Al 2 O 3 and spinel (MgAl 2 O 4 ). Careful oxidation of pulverised waste MoSi 2 rendered a precursor mixture of MoO 3 and amorphous SiO 2 , which served as pore forming agent and SiO 2 source, respectively. Evaporation of MoO 3 at ∼750 °C allowed production of highly porous cordierite-mullite ceramic composite after sintering in air at 1350 °C for 4 h. The combination of equiaxed cordierite grains and elongated (prism-like) mullite grains, resulted in unique microstructure with open porosity between 53.3 and 55.6 vol% which makes the obtained composite convenient for application as diesel particulate filter material. The presence of mullite affected four key thermo-mechanical properties which determine the thermal shock resistance of cordierite-mullite composite. The best thermal shock resistance was measured in composite containing 75 wt% of mullite. It was a result of improved thermal conductivity (1.081 W/mK) and bending strength (3.62 MPa) and relatively low values of coefficient of thermal expansion (3.8 × 10 −6 K −1 ) and elastic modulus (2.27 GPa).