MnO2-TiO2 composite additives driven low-cost fabrication of coal gangue/bauxite ceramic proppants

The urgency of resource utilization for coal gangue has driven innovations toward its high-value processing technologies. Although coal gangue can serve as a low-cost source of silicon and aluminum—reducing raw material costs by 14% compared to pure bauxite—its direct application in the production of ceramic proppants faces significant challenges. These challenges include an excessively high calcination temperature (e.g. >1450 °C) and compromised mechanical properties. In this study, we designed the fabrication of ceramic proppants by using coal gangue and bauxite as raw materials. By adjusting the dosage of a MnO 2 –TiO 2 composite additive (0–7.5 wt%), a dual-phase ceramic proppant composed of corundum and mullite was prepared. The results show that the addition of the MnO 2 –TiO 2 can lower the sintering temperature, allowing the proppant to develop a well-dense structure within the temperature range of 1250 to 1350 °C. However, the composite additive also inhibits the formation of mullite while promoting the development of the corundum phase. This phase transformation enhances the compressive strength of the proppant but simultaneously increases its density. When the composite additive content is 7.5 wt% and the sintering temperature is 1350 °C, the resulting ceramic proppant exhibits a bulk density of 1.88 ± 0.01 g/cm 3 and an apparent density of 3.17 ± 0.02 g/cm 3 , with a minimum breakage rate of 2.71 ± 0.32% under 52 MPa.