Excellent hydration and thermal shock resistance in MgAlON–MgO ceramics synthesized from spent MgO–C brick: Microstructural characteristics, hydration mechanism and thermal shock behaviour

Hydration and thermal shock resistance of MgAlON–MgO ceramics synthesized from spent MgO–C bricks were investigated by hydration experiment and water/air quenching method. It was observed that MgAlON does not undergo hydration reaction and hydrated MgO only accounts for about 0.2 wt% of total amount of MgAlON–MgO ceramics. Thermal shock tests indicated that MgAlON–MgO quenching in water show different fracture mechanism at different temperature. The retained strength of MgAlON–MgO ceramics quenched at 1398 K is only affected by thermal shock. However, the retained strength of the ceramics quenched at 698 K and 1098 K are affected by synergistic effect of hydration reaction of MgO and thermal shock. The retained strength of MgAlON–MgO ceramics quenching in air and water at 1398 K still reached about 55 MPa and 6 MPa, respectively. Furthermore, thermal shock resistance of MgAlON–MgO improve with the increase of MgO content and MgAlON with 15.7 wt%MgO shows the best thermal shock resistance. The reason for the improvement is that the microcracks between MgAlON and MgO particles increase with the increase of MgO content, and the dispersed microcracks could release the thermoelastic strain energy and thus inhibit crack propagation. The results showed that the MgAlON–MgO ceramics synthesized with spent MgO–C bricks possess excellent hydration and thermal shock resistance hence have potential application in the metallurgical industry.