Interfacial behavior and evolution mechanisms of mechanical and thermal properties in graphene/Cu composites based on molecular dynamics and spark plasma sintering

By integrating the excellent formability of copper with the ultra-high in-plane thermal conductivity and robust mechanical properties of graphene, graphene/Cu composites exhibit broad application prospects in cutting-edge defense equipment, fifth-generation (5G) communications, artificial intelligence (AI) servers, and new energy sectors, making them promising candidates for thermal-management packaging in high-power electronic devices. However, the weak van der Waals forces between graphene and Cu render the interface highly susceptible to severe phonon scattering, thereby degrading the overall thermal conductivity. This interfacial bottleneck makes it exceptionally challenging for high-volume-fraction heat sink composites to achieve a trade-off between superior thermal conductivity and microscopic mechanical stability at the interface. Here, minor Ti addition was investigated through molecular dynamics (MD) simulations and spark plasma sintering (SPS) experiments to connect atomistic mechanisms with interfacial evolution at different temperatures. Ti-C bonds transformed the modeled interface from physical adsorption to strong chemical bonding. Under identical MD conditions, the model with Ti-C bonding exhibited a work of adhesion 12.6 times that of Gr/Cu, a 78.2% higher theoretical peak tensile strength, and a 19.8% lower effective interfacial thermal resistance. Phonon participation ratio analysis indicated that Ti-C bonding promoted more spatially extended interfacial vibrational modes, while models containing carbon vacancies showed that disruption and clustering of the carbon network markedly weakened the mechanical response. Experiments revealed corresponding changes in Ti distribution, interfacial chemistry, and fracture morphology. Within the investigated 0.8 wt% Ti series, 925 °C provided a favorable balance between Ti redistribution, interfacial bonding, and preservation of the graphene structure, whereas 950 °C caused pronounced Ti agglomeration and lamellar fragmentation. These results clarify how Ti-C bonding enhances interfacial load and heat transfer and provide guidance for controlling interfacial reactions in graphene/Cu composites.