Effect of microstructure and surface roughness on the wettability of superhydrophobic sol-gel nanocomposite coatings

Sol-gel nanocomposite coatings were fabricated by spraying precursor mixtures containing hydrophobically modified silica (HMS) nanoparticles dispersed in sol-gel matrices prepared with acid-catalyzed tetraethoxysilane (TEOS), and methyltriethoxysilane (MTEOS). The hydrophobicity of the coatings increased with increase in the concentration of HMS nanoparticles. Superhydrophobic coatings with water contact angle (WCA) of 166A degrees and roll-off angle < 2A degrees were obtained by optimizing the sol-gel processing parameters and the concentration of silica nanoparticles in the coating. FESEM studies have shown that surface has a micro-nano binary structure composed of microscale bumps and craters with protrusions of nanospheres. The properties of composite coatings fabricated by spin coating and spray coating methods were compared. It was found that the microstructure and the wettability were also dependent on the method of application of the coating.