The Influence of Different Foaming Agents on the Properties and Foaming Mechanisms of Foam Ceramics from Quartz Tailings

The type of foaming agent significantly influences the pore structure and properties of foam ceramics, particularly their compressive strength. This study used quartz sand tailings and waste glass powder as raw materials to fabricate foam ceramic materials. The effects of different foaming agents (SiC, CaCO3, and MnO2) on the phase evolution, microstructure, pore size distribution, and physical properties of the foam ceramics were investigated, and the foaming mechanisms were elucidated. The results indicated that when SiC was employed as the foaming agent, the viscosity was high at elevated temperatures and pores with irregular shapes tended to form because of the anisotropy of the quartz crystals. CaO generated from CaCO3 decomposition reduced the melt viscosity by disrupting the [SiO4] tetrahedra, whereas the formation of anorthite and diopside stabilized the pore morphology, resulting in regular circular pores. When MnO2 was used as the foaming agent, the pressure from the gas produced during oxidation exceeded the surface tension of the molten phase owing to its viscosity, leading to the formation of larger, irregular, and interconnected pores. The foam ceramic material exhibited optimal properties when 2% CaCO3 was used as the foaming agent, with a water absorption rate of 30%, bulk density of 0.62 g/cm3, porosity of 68.4%, compressive strength of 9.67 MPa, and thermal conductivity of 0.26 W/(m·K).