An in situ reaction-bonding technique was developed to fabricate porous silicon carbide (SiC) ceramics in air from SiC and Al₂O₃, using graphite as the pore former. The main phase is SiC and the bonded phases are mullite and cristobalite in porous SiC ceramics. The reaction-bonded SiC ceramics possess connected open pores. The linear shrinkage of the specimens before and after sintering is between --1.5% and +1.5%. Open porosity decreases with the sintering temperature and forming pressure, but increases with the graphite content. Bulk density and mechanical
strength increase with sintering temperature and forming pressure, but decrease with the graphite content. The pore size distribution takes on a bimodal distribution when the graphite particle size is 20.0μm. In addition, as-fabricated porous SiC ceramics exhibit low coefficient of thermal expansion, high N₂ permeability, excellent high temperature-oxidation
resistance, good acid endurance and relatively bad alkaline endurance.