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Study on Structure Control and Performance of Superhydorphobic Coatings

Author: HuYou
Tutor: HuangChengYa；WangHuiMin
School: South China University of Technology
Course: Materials Engineering
Keywords: superhydrophobic decamethylcyclopentasiloxane microstructure electrocheildeposition capillary force
CLC: O647.1
Type: Master's thesis
Year: 2011
Downloads: 235
Quote: 0
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Abstract

A superhydrophobic coating can show many unique properties, like self-cleaning, hydrophobic, low friction and anti-icing, etc. These properties make superhydrophobic coatings have important application prospects in industrial and agricultural production, national defense and people’s daily lives. As the wettibility of the surface is governed by both the chemical composition and surface microstructure of the surface, so the control of surface hydrophobicity can be achieved by changing the material by chemical composition and surface structure. This paper is based on this theory and two techniques are included. Firstly, a micro-nano dual structure combination with low surface free energy material is prepared on glasses; the second, a micro-roughness surface modified with low surface free energy material is fabricated on aluminum alloy plates. Both above methods are implemented for the control of surface hydrophobicity, which provides a foundation for further industrial applications. Finally, a two-dimensional model is created based on experiments and literatures. The wetting state of a water droplet on superhydrophobic surface is modeled .This article reads as follows:1. Cotton candy-like superhydrophobic thin surfaces were prepared on glass by air-brushing the in situ polymerization compositions of D5/SiO2 and additives. The prepared surface exhibits excellent hydrophobic, the water static contact angle exceeds 150°, and the roll angle is less than 5°. More importantly, such a superhydrophobic surface shows certain chemical stability, good adhesion and excellent thermal stability.2. Weathered rock-like superhydrophobic surfaces were fabricated on aluminum alloy substrates by galvanization to generate a surface roughness, followed by hydrophobization with 1-Octadecanethiol. By changing the current density, different micro-roughness galvanized surface can be build. Various characterization results and theoretical analysis show that: the special microstructure along with the low surface energy leads to the high surface superhydrophobicity. In addition, the prepared superhydrophobic surface exhibits good weather resistance and excellent self-cleaning properties.3. A two-dimensional model is established and the wetting state of a water droplet on superhydrophobic surface is modeled. Based on this, capillary force formula is derived for Cassie state. Combined with the experimental results, hydrophobicity of the prepared samples is analysis using this model. It is concluded that when there exists air trapping in the Cassie state, increasing the fraction of air/liquid not only increases the contact angle, but also decreases the contact area between the solid and liquid, which results in decreasing of adhesion force of solid/liquid while increasing of capillary force, together making motion of water droplet much more easier.

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