Improvements on the mechanical properties and thermal shock behaviours of MgO–spinel composite refractories by ZrO2 incorporation

Microstructural features and improvements on the mechanical properties and thermal shock behaviours of MgO–spinel composite refractories with ZrO2 addition were examined. ZrO2 incorporation into MgO–spinel led to improvements around ∼1.5-fold ratios on mechanical properties, Rst values and thermal shock results. The basic parameters improving mechanical properties and thermal shock resistance of MgO–spinel–ZrO2 composite refractories were determined as follows: (i) propagation of microcracks for a short distance by interlinking each other, (ii) stopping or deviation of microcracks when reaching pores or ZrO2 particles, (iii) concurrent occurrence of mostly intergranular and some transgranular cracks on fracture surfaces, and with the addition of ZrO2 (iv) the increase in bulk density, and (v) a significant decrease in MgO grain size. The improvements observed in thermo-mechanical properties confirmed that MgO–spinel–ZrO2 refractories showed a low strength loss and high thermal shock damage resistance at high temperatures, leading to longer service lives for using industrial applications.