Experiment on preparation of porous glass-ceramics by inorganic gel casting from coal-based slag

Porous glass-ceramics have aroused extensive attention due to their thermal insulation and sound insulation properties. An emerging research focus is the utilization of solid waste as raw material for producing porous glass-ceramics. The inorganic gel casting method, involving alkali activation and mechanical stirring, has been proposed to achieve a hierarchical porous structure. In this study, porous glass-ceramics were fabricated using coal-based slag as the raw material through inorganic gel casting and the effects of the key parameters on the properties of porous glass-ceramics were revealed. Five key factors, namely the mass ratio of raw materials (A), gelation time (B), curing time (C), and sintering temperature (D), and heating rate (E), were identified as the design variables. The Taguchi method of L16 orthogonal array was employed to establish the mix proportions based on these design variables. Subsequently, the influences of these design variables on the microstructure of intermediate porous glass embryo, as well as the porosity and compressive strength of porous glass-ceramics, were analyzed. The results revealed the optimal parameter combination for gel generation as follows: a material mass ratio of 61:35:4 wt%, a gel time of 60 min, and a curing time of 36 h. The effects of these factors on pore structure and compressive strength followed the descending ranks of A > E > B > C > D and A > B > D > C > E, respectively. The maximum gel yield was reached at a mass ratio of 61:35:4 wt%, while the optimal pore structure was obtained at a mass ratio of 66:35:4 wt%. The sintering temperature exhibited minimal influence on the pore structure, whereas the sintering heating rate had minimal effect on the compressive strength. At a gelation time of 90 min and a curing time of 36 h, the porosity were exceeded 30%, and the pore size exhibited uniform distribution.