▎ 摘　　要

The inherent defects of traditional graphite bulks, such as microcracks and brittleness, have a severe impact on their application performances. The introduction of graphene (Gr) into graphite materials is considered as an effective strategy to improve their properties. Herein, Gr reinforced graphite bulk composites with nanodiamonds (NDs) as a matrix precursor and Gr as reinforcement were successfully synthesized by spark plasma sintering. After sintering, the NDs phase was completely transformed into nanographite sheets, and the volume expansion during the transformation endows the graphite bulks with dense structure. The introduction of Gr can not only reduce the internal stress in the sintered composites, but effectively promote the deflection of the crack propagation path. As a result, the prepared composites reinforced by doping 1 wt% of Gr (Gr-1) demonstrates the highest flexural strength (57 MPa) and compressive strength (245 MPa), which are 90% and 82.6% higher than those of the NDs graphitized compacts (Gr-0), respectively. Gr-1 exhibits the lowest friction coefficient (0.1) and higher thermal conductivity and electrical conductivity in all the Gr/nanographite composites. It is attributed to the fact that Gr maintains its planar structure in the matrix and forms a good interface bond with nanographite sheets. (C) 2020 Elsevier Ltd. All rights reserved.