Effect of modified MgO aggregates on mechanical properties of magnesium aluminate spinel refractories

Abstract

Magnesium aluminate spinel (MA spinel) refractory samples were prepared and their cold and hot modulus of rupture, thermal shock resistance were determined, phase composition and microstructure were analyzed by means of XRD and SEM. Experimental results showed that: with introduction of MgO aggregates modified by α-Al 2 O 3 ultrafine powder coating approach, considerable amount of well-developed spinel (MgAl 2 O 4 ) was in-situ formed on the surface of MgO aggregates, being beneficial to reducing expansion stress and enhancing thermal shock resistance of the material, evidenced by the residual strength retention rate of 78.3%; with addition of MgO aggregates modified respectively by hydration and APS coating approaches, hot modulus of rupture (HMOR) of the material can be improved, due to the accelerated sinterability and improved interfacial bond degree of MgO aggregates and matrix, which was brought by micro and nano scaled activated secondary MgO decomposed from hydrated Mg(OH) 2 under heating.