In addition, it was found that all the FGLNAs grown on different substrates have a similar shape and size for the same heating conditions. However, the density of FGLNAs is clearly different. The density of FGLNAs grown

on unpolished Cu foil, Cu foil polished using a 400-grit abrasive paper, and Cu film specimens is shown in Figure 2. NVP-AUY922 solubility dmso The densities of FGLNAs grown on the Cu film specimen and polished Cu foil specimen using a 400-grit abrasive paper are much higher than those grown on the unpolished Cu foil specimen. For all the polished foil specimens, the final results turned out that the best polishing condition for the growth of FGLNAs is 400 grit. The density of FGLNAs grown on the 400-grit polished Cu foil specimen is the highest among all the polished Cu foil specimens. Figure 2 Density of FGLNAs. The FGLNAs were grown on unpolished Cu foil, polished Cu foil (400 grit), and Cu film specimens heated at 120°C for 2 h. Figure 3 shows EDX analysis of the FGLNAs grown on the 400-grit polished Cu foil

specimen heated at 240°C for 2 h. It indicates that the FGLNAs are mainly composed of the Cu element (30.30%) and oxygen element (69.27%). MLN0128 We also obtained similar EDX results for the other specimens. As shown in the XRD spectrum in Figure 4, orientations 111, 200, 311, etc. of Cu2O indicate that the FGLNAs are composed of Cu2O. Similar results of the XRD spectra were also obtained from the other specimens. As shown in the XRD spectrum, Ni is not oxidized. The reason is that the catalyst we used here is high-temperature resistance Ni; therefore, after heating, it continues Adenosine to maintain as Ni. Figure 3 EDX spectra of FGLNAs. The FGLNAs were grown on the polished Cu foil specimen (400 grit) heated at 240°C for 2 h. Figure 4 XRD spectra of FGLNAs. The

FGLNAs were grown on polished Cu foil (400 grit) and Cu film specimens heated at 240°C for 2 h. When the specimens were heated in air, a Cu2O oxide layer formed on the surface of the specimens. As shown in Figure 5, compressive stress occurred in the oxide layer due to the oxide volume expansion. Meanwhile, as a reactive force, tensile stress occurred in the Cu substrate at the interface of Cu2O/Cu, which leads to the generation of vertical gradient stress (VGS) in the thickness direction of the specimen. Therefore, Cu atoms diffuse from the center of the Cu substrate to the interface between the oxide layer and the substrate due to the VGS. In the initial stage, since the temperature is relatively low (120°C and 240°C), the surface oxidation of the Cu foil/film is carried out under a low speed. The Cu2O layer that formed on the Cu foil/film is very thin, and the VGS is not large enough. Therefore, the diffused Cu atoms cannot penetrate the oxidation layer.