Effect of thermochemical activation of clay raw materials on phase formation, microstructure and properties of aluminosilicate proppants

In this study, the complex influence of the preliminary calcination temperature of refractory clay raw materials and mineralizing oxide additives on phase formation, microstructure and properties of aluminosilicate proppants was researched. The morphology structure and phase composition of specimens were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the effectiveness on the addition of 3d-transition element oxides (Fe₂O₃ and MnO₂) and alkaline and alkaline earth oxides (Na₂O, MgO, CaO) and B₂O₃ to the sintering process of samples based on kaolin depends on the temperature of preliminary kaolin calcination (900–1100 °C) and temperature sample sintering (1350–1450°C). Based on the effectiveness of the influence on aluminosilicate ceramic sintering at the temperature range of 1400–1450°C, the recommended additives can be sequentially arranged as follows: Fe₂O₃ > MgO > MnO₂ > Na₂O > B₂O₃ > CaO. The thermal activity scheme for each group of mineralizer additives depending on the temperature conditions of the consolidation process has been proposed in this study. The use of mineralizing additives with kaolin calcined at a temperature range of 980–1100 °C produces lightweight aluminosilicate proppants with bulk density of up to 1.50 g/cm³ at sintering calcination of 1400–1450 °C, which can endure destructive pressures up to 52 MPa.