| Wettability is an important surface characteristic of metals. Surface modification ofmetals with different surface free energy materials can change the wettability of metals andexpand their application fields. In recent years, the hydrophobic nano films have attractedmuch attention in fields of water-repellency, anti-corrosion and anti-friction due to theirunique surface functionality, showing important research significance.In this dissertation, various hydrophobic nano films were prepared on metals by differentfilm-synthesis techniques and low surface free energy materials. The properties such aswettability, corrosion resistance and micro-tribological behavior were investigated. Theimportant conclusions are as follows:(1) The hydrophobic nano film (DBN) was successfully fabricated on low carbon steelsurface by polymer plating technique. The process of polymer plating can be divided into twosteps. The DBN monomers react with substrate at the prime of film formation, and then SHgroups in DBN monomers couple with each other to increase film thickness. Aftermodification by polymer plating, the static contact angle of distilled water increases from65.5°for substrate to96.3°, and the surface free energy decreases from47.21mJ/m~2to36.44mJ/m~2. The corrosion current density of polymer-plated steel decreases to0.53μA/cm~2compared with14.80μA/cm~2for substrate, and the charge transfer resistance rises to15.73kΩ·cm~2compared with2.13kΩ·cm~2for substrate in0.1mol/L NaCl solution. The protectionefficiency is as high as96.42%, indicating that the corrosion resistance property is efficientlyimproved for low carbon steel.(2) The hydrophobic nano film containing F element (ATP) was fabricated on thesurface of Ti-6Al-4V titanium alloy by polymer plating technique. The hydrophobic silanenano film (TES) was fabricated by self-assembled monolayer method. Combining theadvantages of the two techniques, composite film (TES-ATP) was prepared. Theexperimental results show that the composite film combines with the substrate by Si O Tibond, while S S bond was formed between TES film and ATP film through the coupling of-SH groups both in TES monolayer and ATP molecules. (3) The superhydrophobic nano film was obtained on Ti-6Al-4V titanium alloy surfacethrough the combination of chemical etching and polymer plating. The relation betweensurface roughness and wettability was investigated, which indicates that superhydrophobicsurface can be formed on hierarchical structured surface by coating a low surface free energymaterial.(4) The wettability of various modified surfaces was compared. The static contact angleof distilled water on Ti-6Al-4V titanium alloy surface is45.6°and the surface free energy is64.88mJ/m~2; the water contact angle of ATP film is118.2°, and the surface free energy is9.13mJ/m~2; the water contact angle of TES film is94.5°, and the surface free energy is26.17mJ/m~2; the water contact angle of TES ATP film is130.5°, and the surface free energy is8.59mJ/m~2; the water contact angle of superhydrophobic film is155.0°, and the surface freeenergy is0.37mJ/m~2.(5) The micro-tribological behavior of various modified surfaces is investigated. Theexperimental results under constant loading rate show that the friction coefficients ofTi-6Al-4V titanium alloy surface, ATP film, TES film, TES ATP film and superhydrophobicfilm are0.41,0.22,0.23,0.15and0.20, respectively. The results under a constant load of50mN show that the friction coefficient of Ti-6Al-4V titanium alloy surface is0.50; the frictioncoefficient of ATP film is0.19, while the wear life is21s; the friction coefficient of TES filmis0.23, while the wear life is30s; the friction coefficient of TES ATP film is0.17, while thewear life is220s; the friction coefficient of superhydrophobic film is0.20, while the wear lifeis200s. It indicates that the TES ATP film has the best excellent micro-tribologicalproperties, and superhydrophobic film can efficiently improve the friction coefficient andwear life. However ATP film and TES film can only reduce the friction coefficient, while theiranti-friction properties are not satisfactory. |
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