Abstract: This study utilized coal gasification slag as the primary raw material to prepare foam ceramics via the high-temperature foaming method. The effects of sintering temperature, holding time and SiC addition on the pore structure and properties of samples were investigated. The foaming and pore-forming mechanisms were also explored through the morphological changes and thermogravimetric analysis of the green body. The results show that when the sintering temperature is 1 100 ℃, the melt viscosity is too high and the porosity is only 78.7%. When the sintering temperature is 1 150 ℃, the pores become interconnected and the compressive strength decreases to 0.32 MPa. When the holding time is extended to 60 min, the average pore size increases to 3.29 mm and the compressive strength decreases to 0.48 MPa. When the SiC addition exceeds 0.6% (mass fraction), the pore coalescence is intensified. When the SiC addition is 1.2%, the sample bulk density rises back to 0.257 g/cm³. The optimized process parameters are determined to be a sintering temperature of 1 110 ℃, a holding time of 30 min, and a SiC addition of 0.6%. Foam ceramics prepared under these conditions have an uniform pore size, a bulk density of 0.457 g/cm³, a porosity of 81.5%, a compressive strength of 1.33 MPa, and an average pore size of 1.70 mm. The analysis indicates that before the green body reaches the dry shrinkage temperature, the gases are mainly produced by the residual carbon and calcite in coal gasification slag. After the sintering temperature reaches 1 000 ℃, the foaming is transformed into the decomposition of Fe₂O₃ and the oxidation of SiC. Meanwhile, under the action of alkali metals, the SiO₂ protective film is eroded, which promotes the diffusion of oxygen into the melt, thus enabling the continuous growth of bubbles.

Key words: coal gasification slag, foam ceramics, pore, sintering temperature, holding time, silicon carbide