High gas permeability of SiC porous ceramics reinforced by mullite fibers

The gas permeability of SiC porous ceramics (SCPCs) is typically proportional to the open porosity. However, an increase in open porosity can decrease the bending strength due to weak contact between particles. In this study, high-permeability SCPCs were prepared using a combination method of dry press forming and in situ reaction bonding. The resulting materials contained doping mullite fibers as a reinforcing agent and maintained sufficient bending strength. The open porosity, mechanical strength, microstructure, gas permeability and thermal shocking resistance were systematically investigated. The presence of the mullite fibers (4%) led to increases in open porosity and bending strength to 46.8% and 15.7 MPa after sintering at 1450 °C for 4 h. Additionally, gas permeability of 1600 m³/m²·h·kPa was attained in ceramic wafer and a high gas permeability coefficient of 1.64 × 10⁻¹¹ m² was achieved, superior values than most porous ceramic materials were reported. The close thermal expansion coefficient between the mullite fibers and silicon carbide confers good thermal shock resistance. The bending strength of 14.5 MPa was maintained after 60 cold-hot cycles (0–800 °C). The new SCPCs show great promise for use as next generation hot-gas filters.