Effects of sintering parameters on microstructure, graphene structure stability and mechanical properties of graphene reinforced Al2O3-based composite ceramic tool material

Abstract Graphene reinforced Al2O3-based composite ceramic tool materials were synthesized using hot pressing (HP) under sintering conditions of 1550–1750 °C sintering temperature, 5–30 min dwell time and 25–40 MPa applied pressure in order to investigate the effects of sintering parameters on microstructure, graphene structure stability and mechanical properties of composite ceramic tool materials. Sintering parameters of 1600 °C sintering temperature, 15 min dwell time and 30 MPa applied pressure were demonstrated to be the optimal sintering parameters to obtain dense and refined microstructure. The wrapping mechanism of graphene on ceramic grains was believed to play a significant role in the formation process of this optimized microstructure. Based on Raman spectrum analysis, graphene structure stability was subjected to sintering temperature and dwell time. Graphene structure could be destructed under the high sintering temperature or extended dwell time. And the shortened dwell time was also detrimental to graphene structure stability due to the lower crystallinity. Mechanical properties of composite ceramic tool materials were also optimized under the optimal sintering parameters. Grain refinement and weak bonding interface induced by graphene were responsible for the improved fracture toughness.