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

Microporous MgO-Mg(Al, Fe)(2)O-4 refractory aggregates were prepared by the in-situ decomposition synthesis method using the magnesite, Al(OH)(3) and Fe2O(3) as raw materials. The effect of raw material composition (theoretical Mg(Al, Fe)(2)O-4 contents were 0-55 wt %) on their microstructure and strengths was investigated. When the theoretical Mg(Al, Fe)(2)O-4 contents were relatively low (0-5.5 wt %), the number of neck connections between the particles in the microporous MgO-Mg(Al, Fe)(2)O-4 refractory aggregates was small. As the theoretical Mg(Al, Fe)(2)O-4 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)(2)O-4 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)(2)O-4 contents were 11-22 wt %, the microporous MgO-Mg(Al, Fe)(2)O-4 refractory aggregates showed the excellent performances with the median pore sizes of 17.37-25.46 mu m, the apparent porosities of 23.4-28.1%, the bulk densities of 2.57-2.79 g/cm(3) as well as the compressive strengths of 41.2-75.8 MPa.