13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- wear volume is light and the wear process fails at its early stage. Near the initial point, the t3/2 curve increases slower than that of t3/4. That means if suitable chemical reactions are introduced into micro- tribo-devices, corrosive wear can exhibit a longer life-time than adhesive type (Fig. 4). Figure 4. The log-normal distribution of life-time (tl) in nitrogen and ethanol vapor environments. 4. The life-time test in corrosive vapor environments Since the initial wear is sensitive to chemical conditions, several vapor environments are tested to study their lubrication effects, including methanol, ethanol, propanol, isopropanol, 2,2,3,3-tetrafluoropropanol, 2,2,2-trifluoroethanol, hexanol, propylene oxide and water. Their life-times compared by the reference pairs in ethanol vapor environments are shown in Fig. 5. According to these results, fluoroalcohols are better lubricant than fatty alcohols. Figure 5. The life-time ratio of different corrosive vapors. The error bars denote the maximum and minimum values for each case. A basic question is what chemical reactions happen on tribo-surfaces that make fluoroalcohol a better lubricant. For silicon material, especially the silicon dioxide, solvolysis (i.e., hydrolysis for water and alcoholysis for alcohols) is the most important reaction when the environment is filled by
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