Preparation and properties of porous SiC-Al2O3 ceramics using coal ash

In this paper, we first reported that porous SiC-Al2O3 ceramics were prepared from solid waste coal ash, activated carbon, and commercial SiC powder by a carbothermal reduction reaction (CRR) method under Ar atmosphere. The effects of addition amounts of SiC (0, 10, 15, and 20 wt%) on the postsintering properties of as-prepared porous SiC-Al2O3 ceramics, such as phase composition, microstructure, apparent porosity, bulk density, pore size distribution, compressive strength, thermal shock resistance, and thermal diffusivity have been investigated. It was found that the final products are beta-SiC and alpha-Al2O3. Meanwhile, the SEM shows the pores distribute uniformly and the body gradually contacts closely in the porous SiC-Al2O3 ceramics. The properties of as-prepared porous SiC-Al2O3 ceramics were found to be remarkably improved by adding proper amounts of SiC (10, 15, and 20 wt%). However, further increasing the amount of SiC leads to a decrease in thermal shock resistance and mechanical properties. Porous SiC-Al2O3 ceramics doped with 10 wt% SiC and sintered at 1600 degrees C for 5 hours with the median pore diameter of 4.24 mu m, room-temperature compressive strength of 21.70 MPa, apparent porosity of 48%, and thermal diffusivity of 0.0194 cm(2)/s were successfully obtained.