Magnesia–spinel microcomposites

This study used a model system of fully dense high purity MgO, incorporating micron size spinel prepared by hot-pressing. Spinel powder was obtained from two sources: (i) 0.5 μm alumina powder was incorporated into MgO by in situ reaction, and (ii) preformed 3 μm spinel powder. The thermal expansion mismatch between MgO and spinel particles led to the intergranular and intragranular crack development, with consequent loss of strength and Young’s modulus. The extent of interlinking of the microcracking was determined to be a function of spinel particle size and volume fraction; the reasons for this were examined. The mechanical properties and R⁗ parameter values of the microcomposites were reported. The thermal shock resistance of in situ formed 20% 0.5 μm and preformed 30% 3 μm spinel composites, in terms of the R⁗ parameter, was predicted to be 4 to ∼5 times better than that of pure MgO, respectively.