Effect of raw material composition on microstructures and properties of microporous MgO–Mg(Al, Fe)2O4 refractory aggregates

Abstract

Microporous MgO–Mg(Al, Fe)2O4 refractory aggregates were prepared by the in-situ decomposition synthesis method using the magnesite, Al(OH)3 and Fe2O3 as raw materials. The effect of raw material composition (theoretical Mg(Al, Fe)2O4 contents were 0–55 wt %) on their microstructure and strengths was investigated. When the theoretical Mg(Al, Fe)2O4 contents were relatively low (0–5.5 wt %), the number of neck connections between the particles in the microporous MgO–Mg(Al, Fe)2O4 refractory aggregates was small. As the theoretical Mg(Al, Fe)2O4 contents increased to be 11–22 wt %, the number of neck connections increased and the compressive strengths were enhanced. When the theoretical Mg(Al, Fe)2O4 contents increased to be excessive (33–55 wt %), the inter-particle pore size further increased due to the increase of volume expansion caused by the formation of more spinel, resulting in a decrease of compressive strength. Overall, when the theoretical Mg(Al, Fe)2O4 contents were 11–22 wt %, the microporous MgO–Mg(Al, Fe)2O4 refractory aggregates showed the excellent performances with the median pore sizes of 17.37–25.46 μm, the apparent porosities of 23.4–28.1%, the bulk densities of 2.57–2.79 g/cm3 as well as the compressive strengths of 41.2–75.8 MPa.