Low-cost and environment-friendly ceramic foams made from lead-zinc mine tailings and red mud: Foaming mechanism, physical, mechanical and chemical properties

Ceramic foams were prepared by powder technology using lead-zinc mine tailings, red mud and silica sand as the major component, Na2B4O7 as the flux agent. The influence of the sintering temperature on the phase evolution, pore morphology, bulk density, water absorption, porosity, thermal conductivity, mechanical properties and chemical stability was studied. The experimental results showed that a process of desulfurization was observed. With increasing sintering temperature, the bulk density decreased while the porosity and the water absorption both increased. The SEM images showed that larger pores and smaller pores were formed at high temperature. These differences may be caused by the different foaming mechanisms. The thermal conductivity of samples decreased and later increased and the bending strength decreased with increasing the sintering temperature. Based on these results, the sample sintered at 970 °C had a bulk density of 0.56 g/cm3, a porosity of 76.2%, a bending strength of 5.3 MPa and a thermal conductivity of 0.21 W/(m K). Furthermore, because of its high porosity and lower thermal conductivity, the ceramic foams prepared in this work would be suitable for thermal insulation in the building industry.