| Summary: | The interfacial structures and interfacial bonding characteristics between graphene and matrix in graphene-reinforced Al<sub>2</sub>O<sub>3</sub>–WC matrix ceramic composite prepared by two-step hot pressing sintering were systematically investigated. Three interfacial structures including graphene–Al<sub>2</sub>O<sub>3</sub>, graphene–Al<sub>2</sub>OC and graphene-WC were determined in the Al<sub>2</sub>O<sub>3</sub>–WC–TiC–graphene composite by TEM. The interfacial adhesion energy and interfacial shear strength were calculated by first principles, and it has been found that the interfacial adhesion energy and interfacial shear strength of the graphene–Al<sub>2</sub>OC interface (0.287 eV/nm<sup>2</sup>, 59.32 MPa) were far lower than those of graphene–Al<sub>2</sub>O<sub>3</sub> (0.967 eV/nm<sup>2</sup>, 395.77 MPa) and graphene–WC (0.781 eV/nm<sup>2</sup>, 229.84 MPa) interfaces. Thus, the composite with the strong and weak hybrid interfaces was successfully obtained, which was further confirmed by the microstructural analysis. This interfacial structure could induce strengthening mechanisms such as load transfer, grain refinement, etc., and toughening mechanisms such as crack bridging, graphene pull-out, etc., which effectively improved mechanical properties.
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