Effect mechanism of spinel (MgAl2O4) reinforced corundum ceramics on microstructure and properties

Abstract

High strength spinel reinforced corundum ceramics were successfully prepared by using a bauxite mixture with additions of varying mixtures of magnesium ore - clay. Controlled corundum grains were obtained tightly arranged crystal structure by controlling the rate of Al2O3 dissolution-precipitation process through magnesium ore addition in ceramic system. At the same time, the size of the pores was controlled by adjusting the content of the liquid phase in the system. Finally, high strength ceramics were obtained by modifying corundum grain boundary through controlling the content of the magnesium ore. The effects of magnesium ore on microstructure and properties of corundum ceramics were studied. The phase compositions and microstructures were investigated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Fracture mechanism and sintering behavior of corundum ceramics were preliminary analyzed. The flexural strength, density and water absorption of ceramics as functions of magnesium ore contents were systematically investigated. When additions of magnesium ore were 7 wt%, corundum ceramic performances of flexural strength and density were reached a maximum of 291.64 MPa and 3.28 g/cm3. High strength corundum ceramics from bauxite are important to broaden the application fields of bauxite-based ceramics. Alternatively, the formula of the highest strength ceramic (7 wt% magnesium ore) was selected to be the final formula to manufacture proppants, the performances were 4.88% of breakage ratio (under the closed pressure of 86 MPa) and 1.86 g/cm3 of bulk density. The approach opens new opportunities for corundum ceramic as a proppant material since the ceramic system displays high strength.