## 3 Results and Discussion
### Suppressed Mechanical Properties of FS Surfaces
Second, the H\({}_{2}\)O\({}_{2}\) solutions  
Figure 3: (**a**) AFM images and (**b**) corresponding cross–section line profiles of Vickers indentation residual imprints on FS surfaces with an applied load of 0.1 N. (**c**) Residual indentation volume of various FS surfaces. (**d**) Vickers hardness of various FS surfaces. Figure 2: (**a**) Nanohardness and (**b**) reduced modulus of various FS surfaces. can cause weak surface corrosion, which may lead to the reduction in Si-O bond strength of the FS surface [15]. As a result, the FS surface becomes more penetrable, and more surface damage of FS caused by indentation can occur, resulting in lower hardness. As the H\({}_{2}\)O\({}_{2}\) concentration increases, these effects can induce more surface damage of FS following indentation; thus, the hardness and modulus of FS continue to decrease with increasing H\({}_{2}\)O\({}_{2}\) concentration (Figures 2 and 3). Figure 4 shows the AFM image and corresponding cross-section of nanowear marks on various FS surfaces. As the H\({}_{2}\)O\({}_{2}\) concentration increases from 0% to 20%, the depth of wear mark on the FS surface increases from \(\sim\)9.7 nm to \(\sim\)12.6 nm, and the corresponding wear volume of FS increases from \(\sim\)1.2 \(\times\) 10\({}^{3}\) nm\({}^{3}\) to \(\sim\)1.4 \(\times\) 10\({}^{3}\) nm\({}^{3}\), indicating an increase in the wear depth and volume of \(\sim\)27% and \(\sim\)16%, respectively (Figure 4). The friction force on the FS surface decreases slightly from \(\sim\)6 \(\mu\)N to \(\sim\)5 \(\mu\)N (Figure 4d), which is because as the H\({}_{2}\)O\({}_{2}\) concentration increases, the water film thickness on the FS surface increases slightly (Table 1), and this water film can lubricate the sliding interface to some extent [36]. The decrease in friction force and the increase in wear volume with H\({}_{2}\)O\({}_{2}\) concentration suggests the wear mechanism of the FS surface in humid air is not purely a mechanical effect, because a slightly lower wear depth and volume with a lower friction force would be expected with a higher H\({}_{2}\)O\({}_{2}\) concentration if the mechanical effect is the predominate role; in contrast, the data presented in Figure 4 show that the wear depth and volume increase with the H\({}_{2}\)O\({}_{2}\) concentration. Numerous studies have demonstrated that the nanoscale wear of oxide glass in humid air is governed by mechanochemical reactions involving glass substrate, adsorbed water, and the counter-surface, where the formation and dissociation of interfacial bridging bonds at sliding interfaces play critical roles [36; 37; 38]. As the diamond tip slides over the FS surface in humid air, the C-O-Si interfacial bridging bonds can be formed [38]. As the FS surface is treated with H\({}_{2}\)O\({}_{2}\) solutions, the FS surface becomes more hydrophilic; thus, there are several roles that can affect the nanowear performance. For example, as more water can be adsorbed on FS surface, the formation of C-O-Si interfacial bridging bonds becomes more difficult, and the nanowear of FS surface is weakened [38]. Alternatively, as more water molecules are adsorbed on the FS surface, it will facilitate the hydrolysis of the Si-O-Si network of the FS surface under shear stress [37; 39], causing more nanowear of the FS surface. Moreover, H\({}_{2}\)O\({}_{2}\) solutions can cause weak surface corrosion, which may lead to the reduction in the Si-O bond strength of the FS surface [15]. As a result, the nanowear of the FS surface would be facilitated. Based on the results in Figure 4, it seems that the latter two roles play more important roles since the nanowear of FS surfaces increases with the H\({}_{2}\)O\({}_{2}\) concentration under the given sliding contact conditions (Figure 4). Figure 4: (**a**) AFM images and (**b**) corresponding cross–section line profiles of nanowear marks on FS surfaces. (**c**) Scratch depth and its wear volume of various FS surfaces. (**d**) Friction force during nanowear of various FS surfaces.