Revisiting Wetting, Freezing, and Evaporation Mechanisms of Water on Copper

Abstract

Wetting of metal surfaces plays an important role in fuel cells, corrosion science, and heat-transfer devices. It has been recently stipulated that Cu surface is hydrophobic. In order to address this issue we use high purity (1 1 1) Cu prepared without oxygen, and resistant to oxidation. Using the modern Fringe Projection Phase-Shifting method of surface roughness determination, together with a new cell allowing the vacuum and thermal desorption of samples, we define the relation between the copper surface roughness and water contact angle (WCA). Next by a simple extrapolation, we determine the WCA for the perfectly smooth copper surface (WCA = 34°). Additionally, the kinetics of airborne hydrocarbons adsorption on copper was measured. It is shown for the first time that the presence of surface hydrocarbons strongly affects not only WCA, but also water droplet evaporation and the temperature of water droplet freezing. The different behavior and features of the surfaces were observed once the atmosphere of the experiment was changed from argon to air. The evaporation results are well described by the theoretical framework proposed by Semenov, and the freezing process by the dynamic growth angle model.

Switchable Ionic Transportation in the Nanochannels of the MOFs Triggered by Light and pH

“…We attribute this “diffusion barrier effect” to the hydrophobic nature of the SP-COOH form, ,, which switches the channel to a closed state. As a result, the completely diverse behavior in peak current might be attributed to the difference in the channel wettability caused by the conformational changes of the grafted isomeric molecule, which was further proved by the contact angle measurements . When radiated by the visible light, the water contact angle on the channel surface reached 106° ± 2°, which indicates that a hydrophobic surface was achieved (Figure A,C).…”

“…As a result, the completely diverse behavior in peak current might be attributed to the difference in the channel wettability caused by the conformational changes of the grafted isomeric molecule, which was further proved by the contact angle measurements. 40 When radiated by the visible light, the water contact angle on the channel surface reached 106°± 2°, which indicates that a hydrophobic surface was achieved (Figure 4A,C). Due to the higher polarity of MC-COOH than SP-COOH, the channel surface was converted to be hydrophilic with a contact angle of approximately 58°± 2°in the dark, thus permitting the ionic transportation (Figure 4B,D).…”

Biomimetically Inspired Highly Homogeneous Hydrophilization of Graphene with Poly(l-DOPA): Toward Electroconductive Coatings from Water-Processable Paints

“…The water contact angle (WCA) (five measurements, standard deviation < 5%) was measured at 25 °C (relative humidity, 35%) using the goniometric system used by us previously. 62 The samples of G3, G3@PDOPA, and PDOPA were sprayed on the surface of polished silicone (1 × 1 cm, Institute of Electronic Materials Technology, Lukasiewicz Research Network, Warsaw, Poland) using air under a pressure of 2.5 bar airbrush (Fine-Art FA-180X, with a 0.2 mm nozzle). The dispersions/solutions were sprayed up to a coverage of 0.1 mg cm –2 .…”

Surfaces with Adjustable Features—Effective and Durable Materials for Water Desalination

“…SFE plays a significant role in surface-active media producing an adsorption-induced reduction in strength to deformation (the Rebinder's effect) [33,34]. Since SFE was calculated based on the values of contact angle corrected by the roughness [35], it was possible to exclude the impact of the roughness/irregularities that might be a source of error in SFE calculation. The measured critical surface tension (γcr) for the pristine material PVDF was 32.3 ± 1.1 mN m −1 , which agrees with estimates in the literature ranging between 30.3-37.4 mN m −1 [47,48].…”

“…The results of apparent contact angle (CA) with different testing liquids (3 µL drop volume) allowed the calculation of spreading pressure (S), surface free energy (SFE), and critical surface tension (γ cr ) [32]. The values of CA were determined with the roughness correction applying the Fringe Projection Phase-Shifting method [35]. To calculate the SFE according to the Owens, Wendt, Rabel, and Kaelble (OWRK) method, liquids with liquid surface tension in the range of 18.5 mN m −1 for hexane to 72.7 mN m −1 for water were used (Equation (S4)).…”