Synthesis and properties of foam glass-ceramics from granite tailings by using SiC and MnO2 as the mixed foaming agent

Foam glass-ceramics were successfully prepared with the powder sintering method using granite tailings as the main raw material, and silicon carbide (SiC), and manganese dioxide (MnO2) as the mixed foaming agent. The effects of the mixed foaming agent and sintering temperature on the crystalline phase, pore-wall structure, and the properties of the prepared foam glass-ceramics were systematically studied. Moreover, the foaming mechanism of the foam glass-ceramics prepared by using the mixed foaming agent was revealed. The results showed that, with a decrease of SiC content, the thermal conductivity and compressive strength decreased, and with an increase of MnO2 content, a special connected pore structure formed in the pore wall of the sample. The optimum mass ratio of MnO2: SiC in the mixed foaming agent was 1: x (x = 3‒7). Foam glass-ceramics with good thermal insulation performance, a bulk density of 0.35–0.50 g/cm3, a porosity of 85.05–88.12%, a thermal conductivity of 0.037–0.046 W/(m·K), and high compressive strength (0.46–3.11 MPa) were obtained at the sintering temperature of 880 °C.