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A Micro-Nano Structure On Steel Surface: Preparation, Characterization, Surface Wetting And Its Use In An Anti-Fouling Coating

Posted on:2017-08-12Degree:DoctorType:Dissertation
Country:ChinaCandidate:S LuoFull Text:PDF
GTID:1311330512452871Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
Micro-nano structure plays a vital role for preparation of a super-hydrophobic surface with self cleaning, anti-stick or anti-fouling property. Metallic materials have been used in many fields. As a metallic material, steel is widely used, and needs to be coated with a super-hydrophobic coating for some special purpose, such as anti-fouling and other properties. Hence, preparation of a micro-nano structure on steel surface is a fundamental work. A two-step method is proposed to prepare a micro-nano structure on steel surface. The two-step method combines micro-shot peening and anodization. Micro-shot peening is proposed for preparing a micro-structure and anodization is proposed for preparing a nano-structure. A study on wettability of the micro-nano structure is conducted. Anti-fouling property of a surface with the micro-nano structure is evaluated.A method based on the theory of metal plastic deformation is proposed for fabricating a micro structure. This method is micro-shot peening. Surface topography of a surface with the micro-structure has been studied using the following techniques: macroscopic and microscopic analysis, surface profile analysis, and surface. roughness. Results show that micro-shot peening produces a micro-structured surface with a controlled roughness and a concave-convex texture. Peening pressure, size of micro-shots and peening time has an effect on fabrication of the micro-structure.Anodization is proposed for fabricating a nano-structure on steel surface. Effects of pretreatment on anodization of steel are investigated. The mechanism for promoting anodization of steel by shot peening is investigated. Surface topography and chemical composition for anodized film have been studied using the following techniques:SEM, EDS, XPS, XRD, Raman and IR. A polarization curve test has been carried out to investigate the corrosion resistance of the steel coated with the anodized film. Results show the following. Anodization produces a nano-structure on steel surface. Micro shot-peening aids anodization of steel. Anodized films are yellow in color, and the color of films deepens with increasing anodization time. The anodized film contains Fe,O, C and F. The chemical form of iron in the anodized films is Fe (?). Anodized oxides are mainly ?-Fe2O3 and FeOOH. The corrosion resistance of the steel coated with an anodized film is improved compared with an uncoated steel.A two-step method is proposed for fabricating a micro-nano structure on steel surface. Surface topographies of the micro-nano structure is investigated using SEM and AFM. Research on wettability of a surface with the micro-nano structure is conducted to reveal the effects of surface structure and surface chemical modification on wettability. Results show the following. A nano-structure is coupled onto the top of a micro-structure to form a micro-nano structure. The micro-structure shows a concave-convex texture. The nano-structure shows primarily a flower-like pattern. Current density has an effect on the pattern of the micro-nano structure. A contact angle is depended on a surface structure. Before modifying these structured surfaces, the surface with the micro-nano structure shows a smallest contact angle. After modifying these structured surfaces, the surface with the micro-nano structure has a greatest contact angle, showing super-hydrophobicity. Compared with stearic acid, a structured surface modified using trichlorosilane has a greater increase in the contact angle.Application of the micro-nano structure is explored. A super-hydrophobic coating with the micro-nano structure is produced by the two-step method and subsequent chemical modification. Anti-fouling property of this coating is evaluated. Results of the comparative study show that chemical modification reduces surface energy to aid the surface to repel contamination. Surface structure has an influence on the anti-fouling property. As a hierarchy structure, micro-nano structure can hold up contamination, resulting in a decrease in the real contact area between the steel surface and the contamination. Micro-nano structure reduces steel surface fouling.
Keywords/Search Tags:micro-nano structure, micro-shot peening, anodization, surface wetting, super-hydrophobic, anti-fouling
PDF Full Text Request
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