Abstract
By addition of colloidal alumina, three different particle sizes of dead burnt MgO were employed as raw materials to prepare MgO-based spinel substrates at 1773 K (1500 °C). It was found that the particle size of MgO, as well as its size distribution, had substantial impact on the resistance of the refractory to the slag penetration at 1873 K (1600 °C). Using relatively small particles of MgO (<0.5 mm) can efficiently limit the slag penetration, due to the formation of solid phases (CaO·Al2O3 and CaO-MgO-Al2O3) at the grain boundaries. A particularly significant improvement against the slag penetration was found on MgO substrates with a proper particle size distribution in a size range of 0-1 mm. The improvement could be mainly related to the higher density and distribution of spinel phase in the MgO matrix, which is mostly located at the borders of large MgO particles.