## 4 Results Characterization
### FESEM Characterization  
At the end of the experiment, the copper samples were taken out and their surface topography was characterized by FESEM. The surface photomicrographs are shown in Figures 5 and 6. Figure 5 shows the surface morphology of copper in the C\({}_{5}\)F\({}_{10}\)O/N\({}_{2}\) gas mixture experiment group and the control group. In the control group, the copper surface is smooth and flat, while its structure is fine and compact. The small grooves appearing under the microstructure are inevitable due to the limitations of the manufacturing process. When the experiment temperature is 120 \({}^{\circ}\)C, corrosion spots appear on some parts of the copper surface. Figure 5b presents the morphology of the corrosion point, which in turn shows an island-like irregular distribution in the field of view and a flat crystal structure. When the experiment temperature is 170 \({}^{\circ}\)C, the distribution of the corrosion points gradually increases while its distribution remains relatively uniform. The crystal structure of the corrosion points in the entire field of view becomes more three-dimensional, and the crystal exhibits a certain regularity. When the experiment temperature is 220 \({}^{\circ}\)C, the corrosion layer evenly covers the entire copper surface, and the density of the corrosion point increases. However, the corrosion layer remains in the shallow region of the copper surface during the experiment. When the copper surface temperature increases, the corrosion point is initially concentrated in the position where the copper surface has a small flaw. As the temperature increases, the corrosion point gradually spreads across the surface of the copper sample. The temperature further increases, and the corrosion point becomes dense, thereby covering the entire copper surface. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Gas Type** & **Mass-to-Charge Ratios (m/z)** & **Separation Time (min)** \\ \hline C\({}_{5}\)F\({}_{10}\)O & 69, 97, 169, 197, 266 & 6.423–7.254 \\ C\({}_{3}\)F\({}_{7}\)H & 69, 151 & 6.013–6.373 \\ C\({}_{3}\)F\({}_{6}\) & 69, 100, 131, 150 & 5.762–5.964 \\ C\({}_{4}\) & 51, 69 & 5.106–5.295 \\ C\({}_{3}\)F\({}_{6}\)O & 69, 97, 147 & 5.339–5.631 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: C\({}_{5}\)F\({}_{10}\)O gas and its decomposition product mass-to-charge ratios (\(m/z\)) and separation time. Figure 4: Gas chromatogram of C\({}_{5}\)F\({}_{10}\)O gas. Figure 6 shows the surface morphology of the copper in the C5F10O/air gas mixture experiment group and the pure C5F10O experiment group. When viewed under an electron microscope, the surface of the copper sample of the pure C5F10O experimental group is  
Figure 5: FESEM morphology of the surface after contact of copper with C5F10O/N2 gas mixture. Figure 6: FESEM morphology of the surface after contact of copper with C5F10O/air gas mixtures. very corroded, and at high magnification, coarse and irregular cubic grains are observed on the surface. When the experiment temperature of the C\({}_{5}\)F\({}_{10}\)O/air gas mixture experiment group is 120 \({}^{\circ}\)C, no obvious corrosion point is observed on the copper surface. The copper surface color of the C\({}_{5}\)F\({}_{10}\)O/air gas mixture experiment group at 120 \({}^{\circ}\)C becomes similar to that of the C\({}_{5}\)F\({}_{10}\)O/N\({}_{2}\) gas mixture experiment group at a temperature of 220 \({}^{\circ}\)C. However, the micrograph does not show a similar morphology, thereby suggesting that the change in the color of the copper surface cannot accurately determine whether the copper is corroded. Therefore, FESEM testing must be applied on the copper samples. When the experiment temperature is 170 \({}^{\circ}\)C, a dense cubic block crystal appears on the copper surface, thereby suggesting a severe corrosion on the copper surface. Meanwhile, when the experiment temperature is 220 \({}^{\circ}\)C, a rough and uniform crystal is observed on the surface when viewed under a microscope, and a more serious degree of corrosion is recorded.