Effects of Chromite Additive on the Microstructure and Performance of Bauxite-based Fracturing Proppant

High-strength fracturing proppant was prepared by pressureless sintering process using bauxite(67wt% Al2O3)and chromite as raw materials. The influence of chromite content(0-5wt%) on phase composition, microstructure and breakage ratio were studied by XRD, SEM, EDS and the column compression method, respectively. The results indicate that the additive of chromite promotes the formation of solid solution of chrome-corundum(Al2-2x Cr2x O3,0x1)and rod-shape mullite phases, both of which are believed to strengthen the fracturing proppant. Additionally, liquid phase is formed by excessive ferrum located between the ceramic grains at relatively high sintering temperatures, which is important for accelerating the sintering densification. The sintering temperature decreases with the addition of chromite. The optimized proppant sample with 2wt% chromite doped, sintered at 1420 ℃ for 2 h shows a breakage ratio of only 1.8%under the pressure of 69 MPa. Furthermore, 2 wt% chromite doping decreases the sintering temperature by 60 ℃(from 1480 ℃ to 1420 ℃). This process enables the production of high-strength fracturing proppant from low-rank mineral materials and demonstrates a promising practical application.