Effect and mechanism of Fe₂O₃ decomposition in the preparation of foaming ceramics from industrial solid waste

MgO-Al2O3-SiO2 foam ceramics were prepared by direct sintering of asbestos tailings and coal fly ash by spontaneous bubble process. By X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermodynamic analysis, the effect of Fe2O3 decomposition on the preparation of foaming ceramics from industrial solid waste and the pore-forming process was studied. The results show that the foaming effect of foaming ceramics with higher raw iron content is better when the roasting temperature is higher. Increasing the content of iron is beneficial to the formation of cordierite, and increasing the roasting temperature is beneficial to the relative content of spinel in foaming ceramics. Combined with the change in the Fe valence state, content in porous ceramic samples, and thermodynamic analysis of the product, it is found that Fe2O3 decomposition is the fundamental cause of ceramic foaming at high temperature. Fe2+ produced after decomposition replaces Mg2+ into spinel and cordierite structures, and the O-2 produced by decomposition cannot be discharged in time to cause ceramic foaming. The research results can provide theoretical basis for the preparation of industrial solid waste foamed ceramics.