Abstract
A method for the preparation of transparent superhydrophobic silica coatings on glass substrates via aerosol‐assisted chemical vapour deposition (AACVD) is described. A multi-layer process to produce dual scale silica nanoparticles films, by using different functional alkoxysilanes was investigated. A first layer of 3-methacryloxypropyltrimethoxysilane (MPS) and a second layer of tetraethylorthosilicate (TEOS) were deposited at different temperatures to generate micro and nano particles of silica. Finally, a layer of perfluorooctyltriethoxysilane was deposited on top of the two layers to achieve superhydrophobicity. The transparent superhydrophobic film showed transparency of 90% in the visible light region with a static water contact angle of 165° and a sliding angle lower than 1°. Various durability tests were performed on the transparent superhydrophobic film, showing a constant water repellency after corrosion and organic solvents tests, strong resistance under UV light, and thermal stability up to 400 °C. Sandpaper mechanical robustness durability test showed superhydrophobicity for up to 5 rubbing cycles. In this study, a novel strategy to achieve highly transparent superhydrophobic glass surfaces using AACVD of alkoxysilanes, to produce surfaces with excellent durability is described. This shows great potential to obtain silica superhydrophobic films for large–scale applications.
Highlights
Over the last few years, the development of superhydrophobic surfaces has generated increasing interest and importance in materials science for applied technologies[1,2]
The precursors solutions Solution of 3methacryloxypropyltrimethoxysilane (SOL-MPS), SOL-TEOS and SOL-POTS were prepared by using acidic aqueous solutions so that alkoxysilane can react with water to form hydrolysed species able to react in the aerosol/reactor to form silica nanoparticles
The formation of silica nanoparticles was improved by the presence of the acidic catalyst, HCl, and a lower amount of water had to be used for the hydrolysis reaction, in order to obtain a more transparent film
Summary
Over the last few years, the development of superhydrophobic surfaces has generated increasing interest and importance in materials science for applied technologies[1,2]. Some practical applications of superhydrophobic surface require that those surfaces retain good transparency, especially in the fields of solar cells, optical devices and windshields. Wenzel’s theory assumes that liquid droplet fully penetrates the interstices on the rough surface This increases the available surface area that can be wetted by the liquid compared to a smooth surface. Roughness is an essential requirement for superhydrophobicity but it frequently causes light scattering, which can lead to opacity of the surface causing a lower transparency[17]. Higher transparency of the superhydrophobic films, surface roughness should be lower than the wavelength of visible light (150° and lower sliding angle (SA). AACVD has showed good results in the preparation of superhydrophobic films by using precursors, which vary widely from each other[32,33]
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