Mitigating interfacial thermal resistance in fine-grained diamond/Cu composites via a continuous diamond-diamond network

Diamond/Cu composites can be used to achieve the efficient heat dissipation of high-power devices. Particularly, the low coefficient of thermal expansion, smooth surface, and relatively low cost of fine-grained diamond/Cu composites make them promising candidates for further research. However, high interfacial thermal resistance is difficult to be mitigated for diamond/Cu composites with a high volume fraction of fine-grained diamond particles, which severely limits their thermal conductivity. In this study, a high-temperature high-pressure infiltration process was employed to construct a three-dimensional (3D) continuous diamond network within the diamond/Cu-B composite, where the fine-grained diamond particles were interconnected by direct bonding. Microstructural characterization provided direct evidence of diamond-diamond bonding that form a primary pathway for efficient phonon transport. This continuous network shifts the heat transfer mechanism from ‘metal-matrix-dominated’ to ‘diamond-network-dominated’, thereby overcoming the thermal resistance bottleneck imposed by the high content of fine-grained diamond particles (≥80%). The composite achieved a thermal conductivity of ~ 399 W/(m·K) while maintaining excellent surface flatness (Ra ≈ 1.3 μm). The strategy of constructing a continuous diamond network to optimize thermal transport pathways provides a new paradigm for developing next-generation composites with ultra-high thermal conductivity.