Mullite-Corundum Composites from Bauxite: Effect of Chemical Composition

In situ mullite-corundum composites have been prepared from low grade Indian bauxite containing high percentage of impurities (SiO2, Fe2O3, TiO2, CaO) and silica sol to study the effect of different mullite proportions on the refractory properties. Formation of different phases has been identified by X-ray diffractometry and the microstructure has been studied by field emission scanning electron microscopy. XRD analysis shows the presence of mainly mullite and corundum peaks. The bulk density increases and apparent porosity decreases with decreasing amount of mullite phase proportion in the mullite-corundum sintered aggregate. Refractoriness under load of mullite-corundum composites increases with increasing corundum amount up to a certain level and then decreases marginally. The unit cell parameter and cell volume calculated from X-ray diffraction data for mullite also follows the similar trend.