# Graphene-Enhanced CuW Composites for High-Voltage Circuit Breaker Electrical Contacts
## 3 Results and Discussion
### Microstructure and Morphology of Graphene-Enhanced CuW Composites
EBSD results of element distribution mapping and grain orientation diagram of CuW composites and graphene-enhanced CuW composites are shown in Figure 5. From the element distribution maps in Figure 5a,c, it can be seen that the distribution of Cu in CuW80 forms a nearly three-dimensional network structure which is relatively uniform and continuous, with only a small number of areas experiencing concentration and aggregation. However, the connection between some W is not dense enough, making the network-like Cu veins clearly visible, indicating that the metallurgical bonding degree between W-W is still insufficient. After sintering, there are still a few pores inside the material, which also makes the distribution of some Cu too concentrated. In the CuW80 alloy modified with graphene, the W-W bond becomes tighter, and Cu is uniformly distributed in small and uniform gaps, which also reduces the phenomenon of Cu phase segregation. C particles are mostly distributed at the boundary of W, and are often enveloped by Cu. There are three main colors in the orientation map, and different colors represent the different orientations of grains. Figure 5b shows the EBSD orientation map of CuW80 material. It can be seen that the grains are mostly concentrated in the <101> orientation, and the proportion of grains with <001> and <111> orientations is relatively small. The distribution of grains with different orientations is relatively dispersed. The number of <101>-oriented grains in the CuW80 material modified with a small amount of graphene is significantly reduced, and the distribution of grains with different orientations is also more dispersed. At the same time, orientation changes also occurred on multiple identical grains. In summary, after adding graphene, the element distribution of CuW80 material becomes more compact and uniform, and the grain orientation undergoes significant changes. The microstructure of graphene-enhanced CuW composites was analyzed using Raman spectroscopy, as shown in Figure 6. Upon analyzing the Raman spectrum curve at the designated location, it was observed that the peak position coincided significantly with the characteristic peak of graphene, verifying the existence of a graphene structure within that  
Figure 4: In situ characterization of AFM height scanning and SKPFM surface potential scanning. (**a,b**) AFM and SKPFM images of graphene-enhanced CuW composites; (**c**) trend chart of height changing with distance; (**d**) trend chart of potential changing with distance. area. The sharp G peak at 1580 cm\({}^{-1}\) represents the carbon of sp\({}^{2}\) hybrid structure, which proves the existence of graphene, while the D peak at 1350 cm\({}^{-1}\) represents the carbon of a sp\({}^{3}\) hybrid structure, and indicates that a certain defect structure exist. The ratio of 2D peak to G peak can be used to determine that the graphene here is not a monolayer structure, but a certain multilayer graphene aggregation structure [34]. In summary, it can be proved that graphene exists in CuW composites, and it should exist at the interface between copper and tungsten to fill gaps and make up for defects. Figure 5: EBSD characterization of CuW composites and graphene-enhanced CuW composites. (**a**) Element distribution mapping of CuW80; (**b**) grain orientation diagram of CuW80; (**c**) element distribution mapping of graphene-enhanced CuW80; (**d**) grain orientation diagram of graphene-enhanced CuW80. Figure 6: Raman characterization of graphene-enhanced CuW composites. (**a**) Raman spectroscopy image; (**b**) the position of the Raman spectrum sampling point; (**c**) Raman spectrum of graphene-enhanced CuW composites. The X-ray Diffraction technique is mainly used to identify the phase of the material based on cell dimension units. Figure 7 shows X-ray diffraction (XRD) results of CuW composites and graphene-enhanced CuW composites, respectively.