金属表面疏水性研究进展

表面疏水性是近年来科学研究的热点。在生活中观察到荷叶表面上的水滴呈现圆球状,并能在荷叶上滚动而带走灰尘。研究发现荷叶表面具有优越的疏水性和自清洁特性,主要是由其表面微观的粗糙结构和低表面能物质共同引起的。概述了荷叶表面疏水性产生的原因,指出由于荷叶表面存在大量的微米级乳突,在这些微米级乳突上还有一些纳米级结构,这种纳米级结构正是引起荷叶表面超疏水的根本原因。归纳了疏水性表面的重要理论,其中,Young方程针对平整、光滑表面,将液滴在光滑表面上的张力和接触角联系起来;Wenzel模型是在Young方程的基础上引入了粗糙度因子,Wenzel模型中液滴形成的是一种非复合式的润湿状态,液滴和固体表面完全接触;Cassie方程是Wenzel模型的延伸,液滴和固体之间不再是单纯的非复合式接触,而是混有一定空气的复合式接触。在此基础上,综述了近年来表面疏水性的制备方法,包括化学法、特种加工法和微切削法等,最后展望了疏水性表面目前存在的问题。

Hydrophobicity of Metal Surface

Surface hydrophobicity is the hotspot of scientific research in recent years. In daily life, spherical water droplets can be observed on the surface of the lotus leaf, they can roll on the lotus leaf and take away dust as well. It was found that the surface of lotus leaf exhibited excellent hydrophobicity and self-cleaning characteristics, mainly due to its surface microscopic rough structure and low surface energy substances. Causes of the hydrophobicity on lotus leaf were summarized, and it was pointed out that there were a number of micrometer mastoids on lotus leaf under some nanoscale structures. This nanostructure was the root cause of su-per-hydrophobicity. The important theories of hydrophobic surface were concluded. The Young equation associated tension with contact angle of droplets on flat and smooth surface. Wenzel model introduced roughness factor based on the Young equation. The droplets in the Wenzel model formed a non-compound wetting state in which the droplets were in complete contact with solid surface. The Cassie equation was an extension of the Wenzel model, contact between the droplets and solid surface was complex type which was mixed with a certain amount of air. On this basis, the preparation methods of surface hydrophobicity in recent years were reviewed, including chemical method, special processing method and micro-cutting method. Finally, existing problems in hydrophobic surfaces were expected.