Effects of sintering temperature on the properties and the pore evolution of microporous MgAl2O4 aggregates

It is of great significance to develop new types of refractories by replacing the traditional refractory aggregate with a porous refractory aggregate, which enables the long-lived operation of high-temperature industries and low carbon emissions. In this study, microporous MgAl2O4 aggregates containing sub-micron pores were successfully prepared from magnesite and boehmite using an in-situ decomposition pore-forming method. The effects of sintering temperature on the phase compositions, sintering properties, and microstructure of the aggregates were reported for the first time. The resulting aggregates sintered at 1500 degrees C showed superior comprehensive performance with a median equivalent pore diameter of 10.75 mu m, corresponding to a bulk density and closed porosity of 2.27 g cm-3 and 8.7%, respectively. Meanwhile, several sub-micron pores were observed in microporous MgAl2O4 aggregates, which contributed to a lower thermal conductivity of 1.932 W m- 1 k-1 at 500 degrees C and a higher compressive strength of 40.8 MPa. In addition, the formation mechanism of submicron pores was proposed, and the effects of pore structure on the thermal conductivity and compressive strength were discussed.