Preparation And Properties Of Artificial Bionic Superhydrophobic Functional Surfaces

Superhydrophobicity is a special wettability of a solid surface, on which a water droplet could not spread out and just keep sphere shape, and leading to a rolling motional self-clean function. Superhydrophobic surface possesses water repellent properties as louts leaf. Due to the potential applications in self-cleaning, anti-corrosion, anti-fog, drag reduction and so on, it has attracted a lot of interests of the researcher from both fundamental and industrial fields. It has been realized that the high surface roughness and low surface energy are two basic properties of a superhydrophobic surface. Based on this, a lot of methods were used to fabricate superhydrophobic surface, such as sol-gel, plasma etching, water bath deposition, electrospinning, layer by layer and son on. However, few of these methods could be used in large scale production. In this thesis, wet chemical method was used to prepare superhydrophobic ZnO film, modified paint coating and engineering materials. And their superhydrophobic properties were discussed by using Wenzel and Cassie-Baxter models throughoutly. The content of this thesis is as following. In chapter1, the superhydrophobic theory and superhydrophobic surface in nature were introduced, firstly. Then the methods to prepare superhydrophobic surface and their potential applications were summarized.In chapter2, the formation and wettability of flower like ZnO micro-sphere were investigated. HF was used to modify ZnO growth process, and nanosheets composed ZnO microsphere was produced. After modified with heptadecafluorodecyltrimethoxy-silane (HTMS), the ZnO film showed superhydrophobicity with water contact angle154°and water sliding angle less than5°. Then the superhydrophobic property of the film was discussed by combing Cassie-Baxter model and surface morphology analysis. The air pocket among nanoshees, wihch reduced the contact between water and solid surface of the film, accounted for the superhydrophobicity of the film. Finally, the formation mechanism of the ZnO micro-sphere was discussed by changing the experiment parameters, such as growth time, HF concentration. The results showed that H+will reduce the nucleary of ZnO, and F-will restrain ZnO growth along c-axis. Due to synergical effect of these tow ions, flower like Zno micro-spheres were formed.In chapter3, modified paint coating was produced by mixing ZnO particle and paint. As the surface roughness of the surface increased by adding ZnO particles and the low free energy of the paint, the hydrophobicity of the modified paint (water contact angle147°) is better than pure paint (water contact angle95°). The ratios between ZnO and paint will affect the hydrophobicity of the coating, and should be strictly controlled to produce better hydrophobic coating. Finally, by comparing hydrophobicity of the HTMS modified ZnO particle, it could be concluded that the intrinsic poor hydrophobicity of the paint and low air pocket ratio of the ZnO particle are accounted for the sub superhydrophobicity of the coating.In chapter4, superhydrophobic aluminum sheets were fabricated by hot water immersing process and HTMS modification. The effects of temperature and immersing time on the superhydrophobicity of the aluminum sheet were investigated. The results showed that the best experiment parameter were the90℃water and less than2h immersing. In this condition, the treated aluminum sheet shows best superhydrophobicity with contact angle larger than160°and sliding angle less than5°.In chapter5, superhydrophobic zinc sheets were fabricated. Firstly, by HCl etching and hot water treatment, lotus leaf like structure was formed on zinc sheets. After modified by HTMS, the zinc sheets showed superhydrophobicity. After throughout researches, it has been shown that the90s HCl etching could product the sample with the best superhydrophobicity (contact angle larger than160°and sliding angle close to0°).In chapter6, a galvanized iron sheet with both anti-infrared reflectance invisibility functions and superhydrophobic properties was fabricated. Firstly, the micro-scale structures were produced by HCl etching. Then ZnO nanorods were grown on their surface to form lotus-like structure. After modification with HTMS, the surface showed superhydrophobicity. At the same time, the surface possessed anti-infrared reflectance property. It could be ascribed to the light scattering of the ZnO nanorods. Finally, a light scattering model was used to calculate the infrared reflectance of treated sheet. The result fitted well with the experimental data.In chapter7, the whole thesis contents were summarized and the potential applications of the experiment product were illustrated.