Effects of in situ synthesized mullite whiskers on flexural strength and fracture toughness of corundum-mullite refractory materials

The method of in situ synthesis of mullite whiskers was introduced to improve the fracture toughness of the corundum-mullite refractory materials. Effects of process parameters (sintering temperature, holding time and addition amount of V2O5) on flexural strength and fracture toughness of corundum-mullite during the in situ toughening course were analyzed. The optimum process parameters (the sintering temperature of 1350 °C, the holding time of 2 h, and the V2O5 addition amount of 5%) for in situ synthesized mullite whiskers to toughen corundum-mullite were obtained by the response surface method combined with single factor analysis. SEM and EDS analysis results demonstrated that the mullite whiskers had been synthesized in corundum-mullite and they could bridge the cracks during the fracture process. After in situ toughening, the flexural strength versus deflection curves of corundum-mullite showed obvious zigzag or waveform characteristics, indicating in situ toughening effects. At the same time, the flexural strength and corresponding deflection increased remarkably.