# Advancing Copper Wire Technology: Graphene/Cu Composites for Superior Conductivity and Strength
## 3 Results and Discussion
This is crucial for maintaining the structural integrity and enhancing the functional properties of the composites. HRTEM images revealed variability in the interface clarity between graphene and copper grains. In the Gr/Cu-Z wire (Figure 7c), the interface appeared blurred with a high degree of atomic misalignment and a lower order of graphene layers, whereas the Gr/Cu-T wire displayed a distinctly clearer interface with pronounced graphene striations (Figure 7f). The conclusions drawn from these analyses are multifaceted. The predominant localization of graphene within the grains or at the grain boundaries may influence the mechanical and electrical properties of the composite materials [35]. Grain boundaries can act as barriers to dislocation motion, significantly enhancing the mechanical strength of the material. Furthermore, the presence of graphene at the grain boundaries can promote electron mobility by reducing electron scattering, thereby improving conductivity. Further EDS analysis investigated the distribution of C and Cu elements in the composite wires (Figure 8). In the Gr/Cu-Z composite wire, the distribution of C is relatively uniform due to the low layer number and content of graphene, with only slight aggregation observed (Figure 8a-c). In contrast, the C distribution in the Gr/Cu-T composite wire shows a significant presence of carbon aggregates (Figure 8d-f). These results confirm the presence of carbon aggregates, identified as graphene clusters, within the copper matrix,  
Figure 5: Characterization of cross-sectional SEM morphology of the annealed composite wire. (**a,b**) Pure copper, (**c,d**) Gr/Cu-Z and (**e,f**) Gr/Cu-T composite wires. Figure 6: Microstructure of the annealed composite wire: (**a**) the metallographic structure of pure Cu, (**b**) Gr/Cu-Z, and (**c**) Gr/Cu-T composite wires; (**d**) grain size distribution map, (**e**) dislocation density division, (**f**) grain boundary angle distribution, (**g**) EBSD maps of pure Cu, (**h**) Gr/Cu-Z, and (**i**) Gr/Cu-T composite wires. Electrical and mechanical performance tests conducted on annealed composite wires measuring 1.2 m in length and 2.0 mm in diameter have revealed significant improvements in both electrical conductivity and tensile strength upon the introduction of graphene. Specifically, both the annealed Gr/Cu-Z and Gr/Cu-T composite wires demonstrated electrical conductivities of 101.0% \(\pm\) 0.4% IACS, marking a notable increase compared to the 92.6% \(\pm\) 0.4% IACS recorded for pure copper wires (Figure 9a). In terms of mechanical properties, the addition of graphene increased the tensile strength from 201.2 MPa in pure copper to 238.3 MPa in Gr/Cu-Z and 247.1 MPa in Gr/Cu-T, corresponding to enhancements of 18.4% and 22.9%, respectively (Figure 9b). Compared to pure copper wires or graphene/copper composite wires fabricated by other methods reported in the literature, the Gr/Cu composite wires prepared in this work achieve a simultaneous enhancement of mechanical and electrical properties, promoting the potential application of this composite material in high-end electrical equipment, as illustrated in Figure 9c [8; 20; 36; 37; 38; 39; 40; 41]. The mechanisms behind these performance enhancements are primarily attributed to the microstructural changes induced by graphene. The reduction in dislocation density, facilitated by high-quality graphene, leads to decreased electron scattering, thereby enhancing the electrical properties of the annealed wires [6; 36; 42]. Furthermore, graphene's role as a barrier to grain growth results in smaller matrix grain sizes and an increased number of grain boundaries [36]. These additional grain boundaries act as impediments to dislocation movement, thereby enhancing the mechanical strength of composite materials. The conclusions drawn from these tests underscore the significant role of graphene in enhancing both the electrical and mechanical properties of copper wires.