Grain growth kinetics in microwave sintered graphene platelets reinforced ZrO2/Al2O3 composites

The grain growth kinetics and mechanical properties of graphene platelets(GPLs) reinforced ZrO2/Al2O3(ZTA) composites prepared by microwave sintering were investigated. The calculated grain growth kinetics exponent n indicated that the GPLs could accelerate the process of the Al2O3 columnar crystal growth. And the grain growth activation energy of the Al2O3 columnar crystal indicated that the grain growth activation energy of the GPLs doped ZTA composites is much higher than those of pure Al2O3 and ZTA in microwave sintering. The optimal mechanical properties were achieved with 0.4 vol% GPLs, whose relative density, Vickers hardness and fracture toughness were 98.76%, 18.10 GPa and 8.86 MPa m1/2, respectively. The toughening mechanisms were crack deflection, bridging, branching and pull-out of GPLs. The results suggested that GPLs-doped are good for the Al2O3 columnar crystal growth in the ZTA ceramic and have a potentially improvement for the fracture toughness of the ceramics.