Crack-healing in spinel (MgAl2O4) ceramic

This paper reports the crack-healing behavior in spinel ceramic. Spinel nanopowder was synthesized via mechanical activation with subsequent annealing of magnesium carbonate and aluminum hydroxide. The produced nanopowder was uniaxially pressed and then sintered at 1200 °C for 1 h. Initial cracks were produced on the surface of the sintered bodies by Vickers indenter to investigate the healing behavior of spinel after various heat treatment regimes. It was found that cracks can be healed completely after annealing the specimens at 1600 °C for 100 h. Those specimens sintered at lower temperatures and/or sintered for less times showed partial healing. The results demonstrated that sintering process and abnormal grain growth are responsible for crack-healing in spinel. Also the healing efficiency was expressed as the strength recovery of the pre-cracked samples after healing procedures and was evaluated by diametral tensile strength (DTS) test or indirect tensile test (ITT). It was found that the strength recovery of those samples heat treated at 1600 °C for 100 h was about 91%, which suggests high healing efficiency.