Experimental examination of the phase transition of water on silica at 298 K

Abstract

The objective of this study was to investigate the prediction of the wetting characteristics obtained from the equilibrium adsorption analysis using the Zeta adsorption isotherm approach with an experimental study. Water vapor’s adsorption and wetting characteristics on a hydroxylated and nano-polished silica substrate were studied in near-equilibrium conditions at temperatures near 298 K. Using a UV–visible interferometer, water vapor adsorbate film thicknesses were measured and converted into amount adsorbed per unit area. The current results show that the wetting transition occurred at an average subcooling value of 0.39 K, less than the predicted value of 0.49 K. All the different experimental observations showed growth of film thickness as a function of subcooling value with a maximum film thickness of 12.6 nm. The analysis of the results further showed that the maximum stable film was in a metastable state that then condensed in a dropwise manner, if perturbed by increasing the subcooling. The study further revealed that the adsorbate is unstable after transitioning. The solid surface energy calculated by including the near-equilibrium observations was comparable and close to that of the equilibrium studies, thus supporting solid surface energy as a material property.

Chemical physics of controlled wettability and super surfaces

“…A fundamental thermodynamic question is addressed in reference [5]. They address the relation between vapor of a liquid, a finite contact angle and a possible wetting transition at saturation vapor pressure.…”