# Advancing Copper Wire Technology: Graphene/Cu Composites for Superior Conductivity and Strength
## 3 Results and Discussion
This microstructural refinement likely contributes to enhanced mechanical properties such as strength and hardness due to increased grain boundary density, known as the grain boundary strengthening effect. Moreover, the rougher surface and presence of graphene clusters could potentially affect the electrical conductivity properties of the composites. These characteristics indicate that Gr/Cu composite wires are promising for applications that demand superior mechanical properties without sacrificing the excellent conductivity typical of pure copper. This makes them particularly suitable for high-performance applications where both strength and conductivity are critical. The incorporation of graphene into annealed Gr/Cu wires substantially modifies their dislocation dynamics and grain boundary characteristics, enhancing electrical conductivity and material strength. Graphene promotes dislocation climb, which in turn leads to a notable reduction in dislocation density (Figure 6e). The climb and rearrangement of dislocations during annealing are the primary mechanisms responsible for the reduction in dislocation density [31; 32]. This decrease in dislocation density is significant as it reduces electron scattering, potentially enhancing the electrical conductivity of the wires. In terms of grain boundary changes, the addition of graphene results in a marked decrease in low-angle grain boundaries, from 9.4% in pure copper to 2.0% in Gr/Cu-Z and further down to 1.3% in Gr/Cu-T, as displayed in Figure 6f. Conversely, there is an increase in high-angle grain boundaries, rising from 34.2% in pure copper to over 59.0% in both types of Gr/Cu composites. Theoretically, the migration and reorganization of grain boundaries during annealing lead to the transformation of low-angle grain boundaries into high-angle ones. This transformation in composites has been widely reported in the literature [33; 34]. High-angle grain boundaries are particularly effective at impeding dislocation motion, suggesting potential improvements in the material's strength due to the addition of graphene. Texture and orientation analysis using Electron Backscatter Diffraction (EBSD) and Inverse Pole Figure (IPF) mapping reveals that graphene incorporation primarily affects the (001) orientation (Figure 6g-i), with a decreased proportion of copper grains aligned in this direction, while the texture in the (101) direction remains largely unchanged. This selective influence on grain orientation indicates that graphene's impact on the microstructure of copper composites is directionally specific. Overall, the reduction in dislocation density and the strategic alteration of grain boundaries by graphene not only promise enhanced electrical conductivity but also improved mechanical strength. The changes in grain orientation further underscore the nuanced yet significant role graphene plays in dictating the microstructural characteristics of Gr/Cu wires. Despite variations in the graphene content between Gr/Cu-Z and Gr/Cu-T samples, the differences in dislocation densities and grain boundary angles are minimal, suggesting that while the presence of graphene significantly alters key microstructural features, the exact content and morphology of the graphene powder exert only slight influences on these properties. These findings underscore the profound and selective impact of graphene on the performance and characteristics of copper composites. Furthermore, TEM was employed to analyze the distribution and impact of graphene within annealed Gr/Cu composite wire materials. The TEM images (Figure 7a,b,d,e) revealed that graphene in both types of Gr/Cu composites wires is predominantly localized within the grains or at grain boundaries, with particle sizes ranging from 50.0 to 100.0 nm. Additionally, some degree of agglomeration of graphene particles was observed in both types of Gr/Cu composites wires, however, no pores or defects were detected in the composites, indicating that the graphene/copper wires possess high density.