Abstract
Abstract Solid/ liquid interaction strongly depends, among other things, on the chemical and physical properties of fluids, therefore, there are unexploited analytical possibilities in investigating the surface wetting and evaporation behavior. Strongly hydrophobic rough surface thin films were prepared by spray-coating a fluoropolymer film with incorporated layered double oxide (LDO) microparticles. We studied the evaporation of ethanol–water mixtures from the low energy (8.4 ± 2.6 mJ/m2) composite surfaces by simultaneous high-speed visible imaging, infrared imaging and weight loss monitoring. The wetting behavior changed from Cassie's wetting mode (pure water) to Wenzel's (pure ethanol) as a function of solvent composition. The vaporization process could be divided into three stages described by constant evaporate rates and the heat transfer coefficient between the studied layer and water is KT = 1768 W/(m2K). We have found strong correlations between parameters of the measured evaporation profiles and certain physical properties of the solvents. It is possible to estimate the viscosity, the boiling point, or the surface tension of a studied liquid merely from the total evaporation time. This novel solvent identification method can serve as a new application field for such low energy hybrid surfaces.
Highlights
Recent developments in nanotechnology have highlighted the importance of the classical topics of wetting, droplet spreading and evaporation [1,2,3,4]
The spherical layered double oxide (LDO) particles were prepared by the calcination of ZnMgAl-Layered double hydroxides (LDHs) powder at 600 °C for 2 h
The measured thickness values of the layers were varied between 64 and 201 μm and increased with the increase in LDO content. These composite layers with porous structure and roughened surfaces, but non- water wetting characteristic seemed like an ideal choice for the characterization of solvent specific evaporation
Summary
Recent developments in nanotechnology have highlighted the importance of the classical topics of wetting, droplet spreading and evaporation [1,2,3,4]. In the Cassie's state the droplet sits on the top of the protrusions of the surface, whereas in Wenzel's state the fluid wets the grooves between the protrusions [16] Due to their different local minimum energy states, the transformation phenomenon from Cassies's mode to Wenzel's mode can occur, which is called wetting mode transition and reduces the contact angle drastically [1]. These rough surfaces are frequently superhydrophobic substrates, on which the droplet evaporation usually follows either the CCA, the CCR, or the mixed mode [17,18]. The so-called coffee-ring patterns develop during this phenomenon [20,21]
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