Preparation And Characteristics Of Superhydrophobic Surface On Magnesium Alloy And Silicon Substrate

Superhydrophobic surface have attracted much attention because of their promising applications in our daily life and industrial applications. Inspired by natural biological superhydrophobic surfaces researchers have found that, surface wettability is governed by the microstructure and surface energy of a solid substrate, thus it can be controlled by the modulation of surface energy and roughness of a solid substrate. In the present dissertation, several kinds of surfaces with special wettability were designed and constructed by manipulating surface roghness and chemical compositions. We have succeeded in preparing superhydrophobic surface base on controlling microstructures and surface free energy by several techniques.1. Superhydrophobic surfaces of silicon substrate and magnesium alloy substrate were prepared by regular surface texture and self-assemled monolayers deposited on textured surface. The relationship between surface microstructures and the contact angle of specimen were analysed by mathematical modeling. The results indicate that the wetting-state on superhydrophobic surface of silicon substrate and magnesium alloy substrate based on lasering manufacturing and SAMs is in accord with the Cassie-Baxter model’s prediction.2. Rough surfaces of Al-Mg alloy substrate were acquired by immersing in solution based on dislocation etching theory, and the rough surface free energy was reduced by modifying self-assemled monolayers. Then superhydrophobic surfaces of Al-Mg alloy substrate were acquired. The surface properties of substrate show that superhydrophobic surface with different adhesive force were acquired by changing immersing time. The results indicate that the different adhesive forces are caused by the different state of water droplets on the superhydrophobic surface with different surface microstructure.3. Superhydrophobic surface of MB8magnesium alloy substrate were acquired by micro-arc oxidation and perfluorodecyltrichlorosilane self-assembled monolayers deposited on the micro-arc oxidation coating. The micro-tribological behavior characterization of substrates was analysed. The results of tribological behavior indicate that compact layer, loose layer and their modified surfaces by SAMs all show a better anti-wear ability than bare magnesium alloy under the same testing condition. The hydrophobic and superhydrophobic boundary lubricating film formed by self-assembled monolayers can reduce the friction coefficient of base layer under certain load conditions. The tribological behavior depends on surface characteristics of base layer, if the boundary lubricating film is failed.4. Micron scale rough structures of MB8magnesium alloy substrate were acquired by micro-arc oxidation technique. Nanoscale rough structures on the surface of micro-arc oxidation coating were prepared by painting epoxy acetone solutione and silica suspension subsquently.Superhydrophobic duplex-treated film was fabricated by perfluorodecyltrichlorosilane self-assembled monolayers deposited on micro-and nanostructures.The duplex-treated film acquired under this condition show stable self-cleaning effect and superhydrophobicity to water droplets with different pH values. The potentiodynamic polarization curves indicate that compared to bare magnesium alloy, corrosion resistance of duplex-treated film increase significantly by two to three orders of magnitude.