Flexible Nanotwinned Graphene/Copper Composites as Thermal Management Materials

The flexible nanotwinned graphene/copper (Gr/Cu) composite is successfully fabricated by pulse electrodeposition (PED). Microstructure, nanoindentation hardness, tensile properties, and thermal conductivity of the Gr/Cu composite are investigated. The results show that the few-layer graphene nanoplates (FLG; six to eight layers) are homogeneously distributed in the nanotwinned Cu matrix, and their orientation is parallel to the boundaries of nanotwins. The defect density of graphene in the Gr/Cu composite is 8.54 × 109 cm–2, close to that of 7.64 × 109 cm–2 in the raw FLG. The thermal conductivity and elongation to failure of the Gr/Cu composite is 431 ± 13 W·m–1·K–1 and 13%, which is increased by 97 and 40% in comparison with the PED Cu, respectively. The enhancement of the thermal conductivity and elongation to failure is attributed to the graphene being parallel to the boundaries of nanotwins and to the high amount of nanotwins. Graphene defects and nanotwins are taken into account to explain thermal conductivity and tensile properties of the Gr/Cu composite. A modified thermal model is proposed to evaluate the thermal conductivity of the Gr/Cu composite. It is found that the measured thermal conductivity is well in agreement with the modified prediction. The present work provides a feasible and potential route to process the Gr/Cu composite with high thermal conductivity and tensile ductility, which could meet the application requirements of thermal management and flexible electronic materials.