Ultrastrong conductive in situ composite composed of nanodiamond incoherently embedded in disordered multilayer graphene

ZH Li and YJ Wang and MD Ma and HC Ma and WT Hu and X Zhang and ZW Zhuge and SS Zhang and K Luo and YF Gao and L Sun and AV Soldatov and YJ Wu and B Liu and BZ Li and P Ying and Y Zhang and B Xu and JL He and DL Yu and ZY Liu and ZS Zhao and YZ Yue and YJ Tian and XY Li, NATURE MATERIALS, 22, 42-+ (2023).

DOI: 10.1038/s41563-022-01425-9

Traditional ceramics or metals cannot simultaneously achieve ultrahigh strength and high electrical conductivity. The elemental carbon can form a variety of allotropes with entirely different physical properties, providing versatility for tuning mechanical and electrical properties in a wide range. Here, by precisely controlling the extent of transformation of amorphous carbon into diamond within a narrow temperature-pressure range, we synthesize an in situ composite consisting of ultrafine nanodiamond homogeneously dispersed in disordered multilayer graphene with incoherent interfaces, which demonstrates a Knoop hardness of up to similar to 53 GPa, a compressive strength of up to similar to 54 GPa and an electrical conductivity of 670-1,240 S-1 at room temperature. With atomically resolving interface structures and molecular dynamics simulations, we reveal that amorphous carbon transforms into diamond through a nucleation process via a local rearrangement of carbon atoms and diffusion-driven growth, different from the transformation of graphite into diamond. The complex bonding between the diamond-like and graphite-like components greatly improves the mechanical properties of the composite. This superhard, ultrastrong, conductive elemental carbon composite has comprehensive properties that are superior to those of the known conductive ceramics and C/C composites. The intermediate hybridization state at the interfaces also provides insights into the amorphous-to-crystalline phase transition of carbon.

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