Abstract:
Surfaces that are repellent to water and liquids in a wide range of surface tension and resistant to high temperatures can have applications in many industrial processes, e.g. refinery process, ethanol concentration, fuel transportation, etc1.
In this work, Lotus leaf (LF) and SLIPS approaches2, providing suitably roughened substrates (aluminum, alloys, or composites) of featured chemistry and topography, were adopted as functional processes leading to solid or liquid working interfaces with water contact angle ≥150° and contact angle hysteresis ≤10. According to the different design approaches, hybrid coatings are obtained by deposition of ceramic oxides (such as Al2O3, SiO2, CeO2) as the inner layer followed by dipping (LF) or infusion (SLIPS) with organic fluoroalkylsilanes as outer layers (with respectively, solid and liquid working interface). Alternatively, the treatment of completely smooth surfaces with a high temperature-resistant oleophobic silicone-based coating was considered. The hydrophobic coated surfaces presented here are characterized by low surface energy and resistance to temperatures up to 400°C, which make them very interesting for practical applications. These enhanced performances are due to the bond strength between the –OH groups of ceramic oxides and the Si-C bond of the organic outer layer4.  
All coated samples were submitted to many thermal cycles at high temperatures followed by an extensive evaluation of hydrophobicity, and morphological and spectroscopic properties. The correlations among the different coatings and their performances highlighted that these coatings after thermal cycles retain their hydrophobic properties while also keeping their morphology unaltered.