# Production and Characterization of Cu/CNT Nanocomposites
## 3 Results and Discussion  
### Powders Characterization  
The powders' morphology, shape, and particle size have an essential role in the success of the production by powder metallurgy. Figure 1 shows the scanning electron microscopy (SEM) images using the secondary electron mode of the as-received Cu powders. These powders exhibited a dendritic shape. Dynamic light scattering (DLS) analysis of particle size distribution revealed a D50 value of 29.45 \(\upmu\)m. The length and width are very different, meaning the particles are elongated. The microstructure of the powders was analyzed in more detail by EBSD. Figure 2 shows a Cu particle's inverse pole figure (IPF), Kernel average misorientation (KAM), and grain boundary maps. The IPF reveals that the particle comprises grains with different crystallographic orientations. Some misorientation is detected, mainly at the surface of the particle. The high-angle misorientation regions, associated with a high density of low-angle grain boundaries, can be attributed to plastic deformation during production. Figure 1: (**a**) SEM images of the as-received Cu powders, (**b**) higher magnification of the region marked in (**a**), (**c**) particle size distribution, and (**d**) average length and width of the particles. Figure 2: Cu powder particle as-received: (**a**) Inverse pole figure (IPF) map, (**b**) Kernel average misorientation (KAM) map overlapped with image quality (IQ) map, and (**c**) IQ map with delineated high- and low-angle boundaries as well as twins. The dispersing/mixing process can change the powders' shape and size, affecting the pressing and sintering steps of nanocomposite production. The evaluation of the effect of ultrasonication on the size and dimension of Cu powders was carried out. The impact of introducing CNTs on these parameters was also studied during this process step. The OM images of the received and dispersed powders and the roundness and particle size distributions for the Cu powders and Cu/CNTs can be seen in Figure 3. Based on these results, it is clear that CNTs do not significantly affect the shape and size of copper powders. Roundness values show only a slight decrease for the value of 1, i.e., a form faintly closer to sphericity. There are also no significant differences in size, and all samples have the same particle size distribution. Similar results were observed for Ni powders processed to the same dispersion and mixing process [20]. Furthermore, the ultrasonication process does not cause significant damage to the structure of the CNTs that would impair their strengthening effect. Figure 4 shows the SEM, TEM, and HRTEM images exhibiting the structure of the CNTs after the ultrasonication process. The size distribution of the outer diameters is also presented in this figure which shows a decrease that may be associated with the exfoliation of the CNTs. Moreover, the process only significantly affects the shape of the powders to avoid influencing the next steps of the powder metallurgy process, mainly during densification in the sintering step. Regarding structural damage, the ultrasonication process causes less damage than the ball milling process, which is one of the most reported in the literature. In the Raman results in Figure 4, the influence of these processes on the structure of the initial CNTs is observed. The decrease in the intensity ratio of the D band (ID) and G band (IG) may  
Figure 3: (**a**,**b**) OM images of as-received and dispersed Cu powders and (**c**) roundness distribution of the particles, and (**d**) particle size distribution, for as-received and dispersed Cu (US: Ultrasonication) and Cu/CNTs powders. be associated with the exfoliation that occurred on the CNTs due to the ultrasonication treatment already observed in previous work [21]. The increase observed for this ratio for ball milling may be due to the growth of defects in the structure of CNTs. Similar results were also obtained by [PERSON] et al. [4], who observed few defects promoted in the structure of the CNTs using sonication.