Effects of Magnesia Fines on Physical Properties of Al2O3-MgO Unfired Bricks

Al2O3-MgO unfired bricks were prepared by using brown corundum, white corundum, fused magnesia and α-A12O3 micropowder as main starting materials, Al2O3-SiO2 gel powder as a binder. The effects of magnesia fines addition on physical performance of Al2O3-MgO unfired bricks were investigated. The phase composition and microstructure were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). The results showed that with the increase of magnesia fines addition, bulk density of Al2O3-MgO unfired bricks after dried decreased and strength increased. After heat treatment at 1100 °C, apparent porosity (AP) slightly reduced, bulk density (BD) slightly increased. Strength had little change. After heat treatment at 1500 °C, AP first decreased and then increased, and strength change correspondingly. The hot modulus of rupture (HMOR) first increased and then decreased with increasing magnesia content. The optimum magnesia addition is at 6.0 wt. %.