Gradient evolution in graphene reinforced carbon/carbon composites

Graphene-guided carbonization is an effective route to achieve carbon-reinforcement/carbon matrix (C/C) composites with high mechanical performance at lower energy consumption, due to the reduced anneal temperatures required. However, the underlying microstructure evolution mechanisms associated with this phenomenon remain mysterious. Here, through large-scale reactive molecular dynamics simulations, we revealed a “gradient evolution” effect occurred in carbon matrix, which gives rise to the formation of additional stacked graphene layers in the vicinity of the original introduced graphene sheet. Two microstructure evolution pathways correlated with such effect are identified: (1) near the introduced graphene surface, one or two graphene-like layers rapidly developed due to the growth of curved carbon nanosheets via edge-crosslinking, (2) away from the graphene surface, graphene-like layers progressively promoted by reconstruction of dissociated disordered carbon nanosheets. As a result, the graphene reinforced C/C composites exhibit significantly improved tensile modulus and strength in comparison to those without graphene. Our study not only provides fundamental insights into the graphene-induced carbonization phenomenon, but also emphasizes the unprecedented potential of graphene as an excellent reinforcement for C/C composites.