A simple and efficient way to prepare porous mullite matrix ceramics via directly sintering SiO2-Al2O3 microspheres

A novel route was proposed to fabricate porous mullite matrix ceramics by directly sintering SiO2-Al2O3 microspheres (SAMs) in air, which was simple and efficient compared with other methods. The effects of sintering temperature on the phase composition, microstructure, porosity and compressive strength of porous ceramics were studied. It is found that the mullite phase generates when sintered at above 1450 °C. SEM results shows that the sintering temperature has a significant influence on the formation of pores morphology. As the sintering temperature increases from 1200 °C to 1650 °C, the original small holes inside and between the SAMs develop into macropores, whose pore size increases to eight times more than that of SAMs at a maximum, and the distribution of pores is relatively uniform. Porous mullite matrix ceramics with the porosity of 81.37% and compressive strength of 6.25 ± 0.91 MPa have been obtained through this method at the sintering temperature of 1550 °C.