Ca(OH)2-assisted preparation of mullite-corundum foam ceramics based on waste electrical porcelain and gangue: phase transformation, structural homogenization, and foaming mechanism

In this study, a low-cost foam ceramic was prepared by a high-temperature reconstruction method using gangue and waste electric porcelain as the main materials. The results showed that the sintering temperature, foaming agent (waste SiC slab) content and modifier Ca(OH) 2 had significant effects on the macrostructure, microstructure, crystalline phases and properties of the foam ceramics. With a sintering temperature of 1190 °C, waste SiC slab dosage of 3 % and the addition of the modifier Ca(OH) 2 , the obtained ceramics showed an earthy-yellow appearance, a compressive strength of 1.20 MPa, an apparent porosity of 64.00 %, a bulk density of 1.08 g/cm 3 , and a vertical expansion of 165 %. The increase of sintering temperature and foaming agent content improved the size of the pores. The SiO 2 protective layer of waste SiC slab was destroyed with the addition of Ca(OH) 2 , resulting in an increase in the porosity of foam ceramics by 24.9 %. Meanwhile, the introduction of calcium ions led to the fracture of Si-O bond and the reduction of liquid phase viscosity, thereby improving the uniformity of the pores. This study provides an innovative strategy and novel ideas for the value-added utilization of solid waste and the preparation of foam ceramics.