# Graphene-Enhanced CuW Composites for High-Voltage Circuit Breaker Electrical Contacts
## 3 Results and Discussion  
### Microstructure and Morphology of Graphene-Enhanced CuW Composites  
The microstructure and morphology of the graphene-enhanced CuW composites were meticulously examined using a combination of advanced techniques, included Scanning Electron Microscope (SEM) coupled with Energy Dispersive Spectroscopy (EDS), Scanning Kelvin Probe Force Microscopy (SKPFM), Electron Back Scatter Diffraction (EBSD), and Raman Spectroscopy. These methods were utilized to confirm the existence of graphene in composites and characterize the composition and microstructure of graphene-enhanced CuW composites. The SEM micrographs of both the ordinary CuW composites and the graphene-enhanced CuW composites are presented in Figure 2. It is evident from the field emission SEM images that a high-sensitivity white graphene phase is clearly distinguishable between the dark copper phase and the light gray tungsten phase. Notably, the grain size of graphene is finer than that of copper and tungsten. During the vacuum infiltration process, due to the infiltration flow of copper, graphene primarily resides in the microstructural defects and grain boundaries of copper and tungsten. This helps to fill the interfacial gaps and compensate for microstructural imperfections. Figure 2: The SEM micrographs of CuW composites and graphene-enhanced CuW composites. (a,b) CuW80; (c,d) graphene-enhanced CuW80. The microstructure and compositional distribution of graphene-enhanced CuW composites were further analyzed using EDS mapping. As depicted in Figure 3, the distribution of tungsten, copper, and carbon within these composites was clearly observed. Notably, the copper phase is seen infiltrating and filling the voids within the tungsten skeleton phase. Additionally, the EDS mapping of the carbon element revealed that graphene is uniformly dispersed throughout the tungsten phase, with some noticeable aggregation observed at the phase interface between tungsten and copper. SKPFM is a characterizing technique which applies scanning Kelvin probe on the basis of atomic force microscopy (AFM). This method simultaneously enables nanometer-scale topography measurement and high-resolution in situ Volta potential mapping. Due to the disparities in electronic work functions among carbon, copper, and tungsten, the distribution of low-potential tungsten and high-potential copper phases can be preliminarily distinguished using SKPFM. By integrating the EDS mapping results presented in Figure 3 with AFM height scanning and SKPFM surface potential scanning, an in situ characterization of the surface height and potential of graphene-enhanced CuW composites is conducted. As depicted in Figure 4, as the distance varies, the surface potential undergoes changes within the range of 0 to 10 \(\upmu\)m. Notably, the surface height exhibits significant and synchronous variations with the potential at approximately 6 \(\upmu\)m. This correlation further corroborates that the predominant phase at the boundary between tungsten and copper is carbon-based. EBSD can be used to analyze the microstructure and orientation of solid crystal materials under different process conditions. In order to study the texture and orientation of graphene-enhanced CuW composites, the sample was analyzed using a Thermo Scientific Helios 5 UX focused ion beam electron microscopy. The texture of face-centered cubic metal includes {011}<100> goss texture, (112)<111> copper texture, {111}<211> R texture, {001}<100> cubic texture, and {011}<211> brass texture. Copper is a face-centered cubic  
Figure 3: The SEM-EDS micrographs of graphene-enhanced CuW composites. (**a**) Optical image; (**b**) EDS mapping of tungsten element; (**c**) EDS mapping of copper element; (**d**) EDS mapping of carbon element. crystal. In the experiment, the crystal orientation of <001>, <101>, and <111> is represented as a triangle.