biostudies-literatureYang XMOST | National Natural Science Foundation of China (NSFC)MOST | National Natural Science Foundation of Chinae2316580121https://www.ebi.ac.uk/biostudies/studies/S-EPMC10907318biostudies-literatureUnknown121(9)Achieving high-performance materials with superior mechanical properties and electrical conductivity, especially in large-sized bulk forms, has always been the goal. However, it remains a grand challenge due to the inherent trade-off between these properties. Herein, by employing nanodiamonds as precursors, centimeter-sized diamond/graphene composites were synthesized under moderate pressure and temperature conditions (12 GPa and 1,300 to 1,500 °C), and the composites consisted of ultrafine diamond grains and few-layer graphene domains interconnected through covalently bonded interfaces. The composites exhibit a remarkable electrical conductivity of 2.0 × 10⁴ S m^-1 at room temperature, a Vickers hardness of up to ~55.8 GPa, and a toughness of 10.8 to 19.8 MPa m^1/2. Theoretical calculations indicate that the transformation energy barrier for the graphitization of diamond surface is lower than that for diamond growth directly from conventional <i>sp²</i> carbon materials, allowing the synthesis of such diamond composites under mild conditions. The above results pave the way for realizing large-sized diamond-based materials with ultrahigh electrical conductivity and superior mechanical properties simultaneously under moderate synthesis conditions, which will facilitate their large-scale applications in a variety of fields.Proceedings of the National Academy of Sciences of the United States of AmericaCentimeter-sized diamond composites with high electrical conductivity and hardness.PMC1090731862271450 622701104412174348 1237401662027816Yang XRen XCheng SLi XMa SZang JLi SZhang ZZhang YLiu BShan CZhao XfalseCentimeter-sized diamond composites with high electrical conductivity and hardness.Achieving high-performance materials with superior mechanical properties and electrical conductivity, especially in large-sized bulk forms, has always been the goal. However, it remains a grand challenge due to the inherent trade-off between these properties. Herein, by employing nanodiamonds as precursors, centimeter-sized diamond/graphene composites were synthesized under moderate pressure and temperature conditions (12 GPa and 1,300 to 1,500 °C), and the composites consisted of ultrafine diamond grains and few-layer graphene domains interconnected through covalently bonded interfaces. The composites exhibit a remarkable electrical conductivity of 2.0 × 10⁴ S m^-1 at room temperature, a Vickers hardness of up to ~55.8 GPa, and a toughness of 10.8 to 19.8 MPa m^1/2. Theoretical calculations indicate that the transformation energy barrier for the graphitization of diamond surface is lower than that for diamond growth directly from conventional <i>sp²</i> carbon materials, allowing the synthesis of such diamond composites under mild conditions. The above results pave the way for realizing large-sized diamond-based materials with ultrahigh electrical conductivity and superior mechanical properties simultaneously under moderate synthesis conditions, which will facilitate their large-scale applications in a variety of fields.2024-01-01T00:00:00Z2024 Feb2026-04-12T19:10:16.164Z2026-04-07T13:17:28.292ZS-EPMC109073183837720410.1073/pnas.2316580121