Temperature-Dependent Wettability of Water on a Nickel Surface at Pressurized Condition: A Molecular Dynamics Study

2019 ◽  
Author(s):  
Dong-Lei Zeng ◽  
Biao Feng ◽  
Jia-Wen Song ◽  
Li-Wu Fan
Keyword(s):  
Contact Angle ◽  
Hydrogen Bonds ◽  
Average Energy ◽  
Contact Angles ◽  
Nickel Surface ◽  
Free Energies ◽  
Water Droplets ◽  
Temperature Dependent ◽  
Interfacial Free Energies ◽  
Solid Liquid

Abstract Temperature-dependent wettability of water droplets on a metal surface in a pressurized environment is of great theoretical and practical significance. In this paper, molecular dynamic simulation is used to study this problem by relating the temperature-dependent apparent contact angles to the changes in solid-liquid and solid-vapor interfacial free energies and hydrogen bonds in the nano-sized water droplets with increasing the temperature. The temperature range of interest is set from 298 K to 538 K in a 20 K interval under a constant pressure of 7 MPa. The results show that the contact angle in general decreases with raising the temperature and decreasing trend can be divided into two sections with different slopes. The contact angle drops slowly when the temperature is below 458 K as a critical point. Beyond this point, the contact angle shows a much steeper decrease. The difference between solid-vapor and solid-liquid interfacial free energies is found to decrease slightly with temperature. Combining with that the surface tension drops with increasing the temperature, a decreasing trend of the contact angle is expected according to the Young’s equation. As the temperature increases, the number and average energy of the hydrogen bonds both decrease, and the hydrogen bonds tend to aggregate at the bottom of the nano-droplets.

Investigation of Pool Boiling Critical Heat Flux Enhancement on a Modified Surface Through the Dynamic Wetting of Water Droplets

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Ho Seon Ahn ◽  
Joonwon Kim ◽  
Moo Hwan Kim
Keyword(s):  
Surface Tension ◽  
Heat Flux ◽  
Contact Angle ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Water Layer ◽  
Contact Angles ◽  
Water Droplets ◽  
Dynamic Wetting ◽  
Modified Surface

Dynamic wetting behaviors of water droplet on the modified surface were investigated experimentally. Dynamic contact angles were measured as a characterization method to explain the extraordinary pool boiling critical heat flux (CHF) enhancement on the zirconium surface by anodic oxidation modification. The sample surface is rectangular zirconium alloy plates (20 × 25 × 0.7 mm), and 12 μl of deionized water droplets were fallen from 40 mm of height over the surface. Dynamic wetting movement of water on the surface showed different characteristics depending on static contact angle (49.3 deg–0 deg) and surface temperature (120 °C–280 °C). Compared with bare surface, wettable and spreading surface had no-receding contact angle jump and seemed stable evaporating meniscus of liquid droplet in dynamic wetting condition on hot surface. This phenomenon could be explained by the interaction between the evaporation recoil and the surface tension forces. The surface tension force increased by micro/nanostructure of the modified zirconium surface suppresses the vapor recoil force by evaporation which makes the water layer unstable on the heated surface. Thus, such increased surface force could sustain the water layer stable in pool boiling CHF condition so that the extraordinary CHF enhancement could be possible.

Molecular Simulation of the Contact Angle of Water Droplet on a Platinum Surface

2005 ◽  
Author(s):  
Bo Shi ◽  
Shashank Sinha ◽  
Vijay K. Dhir
Keyword(s):  
Contact Angle ◽  
Molecular Simulation ◽  
Simulation Study ◽  
Water Droplet ◽  
Solid Wall ◽  
Contact Angles ◽  
Water Droplets ◽  
Platinum Surface

This paper presents a molecular simulation study of the contact angles of water droplets on a platinum surface for a range of temperatures. SPC/E and Z-P model are used for the water-water and water-platinum potentials, respectively. The results show that the contact angle decreases with the increase of system temperatures and increases when the potential decreases. When the temperature is high enough, the contact angles drop to zero degrees. The results were compared with the argon-virtual solid wall and water-Aluminum results, a similar trend was found.

scholarly journals Amphiphobic Nanostructured Coatings for Industrial Applications

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 787 ◽  
Author(s):  
Federico Veronesi ◽  
Giulio Boveri ◽  
Mariarosa Raimondo
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Photoelectron Spectroscopy ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Friction Reduction ◽  
Hybrid Coatings ◽  
Wetting Behavior ◽  
Wide Range ◽  
Solid Liquid

The search for surfaces with non-wetting behavior towards water and low-surface tension liquids affects a wide range of industries. Surface wetting is regulated by morphological and chemical features interacting with liquid phases under different ambient conditions. Most of the approaches to the fabrication of liquid-repellent surfaces are inspired by living organisms and require the fabrication of hierarchically organized structures, coupled with low surface energy chemical composition. This paper deals with the design of amphiphobic metals (AM) and alloys by deposition of nano-oxides suspensions in alcoholic or aqueous media, coupled with perfluorinated compounds and optional infused lubricant liquids resulting in, respectively, solid–liquid–air and solid–liquid–liquid working interfaces. Nanostructured organic/inorganic hybrid coatings with contact angles against water above 170°, contact angle with n-hexadecane (surface tension γ = 27 mN/m at 20 °C) in the 140–150° range and contact angle hysteresis lower than 5° have been produced. A full characterization of surface chemistry has been undertaken by X-ray photoelectron spectroscopy (XPS) analyses, while field-emission scanning electron microscope (FE-SEM) observations allowed the estimation of coatings thicknesses (300–400 nm) and their morphological features. The durability of fabricated amphiphobic surfaces was also assessed with a wide range of tests that showed their remarkable resistance to chemically aggressive environments, mechanical stresses and ultraviolet (UV) radiation. Moreover, this work analyzes the behavior of amphiphobic surfaces in terms of anti-soiling, snow-repellent and friction-reduction properties—all originated from their non-wetting behavior. The achieved results make AM materials viable solutions to be applied in different sectors answering several and pressing technical needs.

Quantitative Evaluation of the Interfacial Free Energies at A Solid-Liquid Lamellar Eutectic Interface

1981 ◽  
Vol 12 ◽  
Author(s):  
W. F. Kaukler ◽  
J. W. Rutter
Keyword(s):  
Free Energy ◽  
Solid Phase ◽  
Interfacial Free Energy ◽  
Eutectic System ◽  
Liquid Interfaces ◽  
Free Energies ◽  
Two Phases ◽  
Interfacial Free Energies ◽  
The Individual ◽  
Solid Liquid

The solid-liquid interfacial free energies of each of the individual phases comprising the eutectic system, Carbon Tetrabromide-Hexachloroethane, were measured as a function of composition using a “grain boundary groove” technique. Thermodynamic data were combined with groove shape measurements made from high resolution optical photomicrographs of the solid-liquid interfaces to give the interfacial free energy data. An interfacial free energy balance at the eutectic trijunction was performed to obtain all the forces acting on that point. The three interphase interfacial free energies at the eutectic trijunctions as well as a solid-solid phase boundary torque were evaluated.It was found that the solid-liquid interfacial free energies of the two phases of the eutectic could be evaluated from photomicrographs of growing or stationary eutectic interfaces. In addition, it was found that for a substantial range of freezing conditions the eutectic interface shape can be predicted from a knowledge of the interfacial free energies alone.

Measuring the contact angle of water droplets on foliar surfaces

1988 ◽  
Vol 66 (12) ◽  
pp. 2599-2602 ◽  
Author(s):  
Richard L. Boyce ◽  
Graeme P. Berlyn
Keyword(s):  
Contact Angle ◽  
Contact Angles ◽  
Water Droplets ◽  
Projected Image ◽  
Novel Technique ◽  
Static Contact

We describe a novel technique for measuring static contact angles on foliar surfaces that uses a micromanipulator and a 35-mm camera equipped with a microlens, autobellows, focusing rail, and tripod. After placing droplets on foliage, the contact angle is photographed. Negatives are mounted as slides, and the contact angle is measured from the projected image. We suggest that this method has a number of advantages over those previously used.

Fabrication of Ultrahydrophobic ZnO by Vapor Phase Transport

2011 ◽  
Vol 282-283 ◽  
pp. 753-756
Author(s):  
Zhi Jun Xi ◽  
Gang Li ◽  
Li Ming Lu
Keyword(s):  
Contact Angle ◽  
Vapor Phase ◽  
Film Surface ◽  
Contact Angles ◽  
Nickel Surface ◽  
Zno Film ◽  
Vapor Phase Transport ◽  
Si Substrates ◽  
Vapor Phase Transport Method ◽  
Phase Transport

A ultrahydrophobic ZnO film was synthesized on the Si substrates by a novel vapor phase transport method. The surface structural properties of as-synthesized ZnO film was characterized using scanning electron micrograph (SEM). The contact angles and the rolling angles on such films were measured through an optical contact angle meter. Wettability studies revealed the films exhibited a ultrahydrophobic behaviour with a higher contact angle of 166.8°±6.8° and lower rolling angle of less than 2°-a water droplet moved easily on the surface. SEM showed that compared with pure smooth nickel surface, a lotus-like structrure with micro-nano hierarchical papillae was obviously observed on the ultrahydrophobic ZnO film surface. Such a speccial surface microstructure may result in the ultrahydrophobicity.

scholarly journals On the limitations of the applicability of Young’s equations temperature

2021 ◽  
Vol 23 (2) ◽  
pp. 218-222
Author(s):  
Magomed Pashevich Dokhov
Keyword(s):  
Contact Angle ◽  
Surface Energy ◽  
Interfacial Energy ◽  
Contact Angles ◽  
Surface Phenomena ◽  
Surface Energies ◽  
Three Phase ◽  
Production Techniques ◽  
The Difference ◽  
Solid Liquid

The article uses the thermodynamics of interfacial phenomena to justify the fact that Young’s equations can correctly describe the three-phase equilibrium with any type of interatomic bonds. Wetting, adhesion, dissolution, surface adsorption, and other surface phenomena are important characteristics, whichlargely determine the quality and durability of materials, and the development of a number of production techniques, including welding, soldering, baking of metallic and non-metallic powders, etc. Therefore, it is important to study them.Using experimental data regarding surface energies of liquids (melts) and contact angles available in the literature, we calculated the surface energies of many solid metals, oxides, carbides, and other inorganic and organic materials without taking into account the amount of the interfacial energy at the solid-liquid (melt) interface. Some researchers assumed that in case of an acute contact angle the interfacial energy is low. Therefore, they neglected it and assumed it to be zero.Others knew that this value could not be measured, that is why they measured and calculated the difference between the surface energy of a solid and the interfacial energy of a solid and a liquid (melt), which is equal to the product of the surface energy of this liquid by the cosine of the contact angle. It is obvious that these methods of determining the surface energy based on such oversimplified assumptions result in poor accuracy.Through the use of examples this paper shows how the surface energies of solids were previously calculated and how the shortcomings of previous calculations can be corrected

scholarly journals Water entry of spheres with various contact angles

2019 ◽  
Vol 862 ◽  
Author(s):  
Nathan B. Speirs ◽  
Mohammad M. Mansoor ◽  
Jesse Belden ◽  
Tadd T. Truscott
Keyword(s):  
Contact Angle ◽  
Weber Number ◽  
Bond Number ◽  
Water Entry ◽  
Contact Angles ◽  
Cavity Formation ◽  
Liquid Impact ◽  
Critical Impact Velocity ◽  
Solid Liquid ◽  
Rough Sphere

It is well known that the water entry of a sphere causes cavity formation above a critical impact velocity as a function of the solid–liquid contact angle; Duez et al. (Nat. Phys., vol. 3 (3), 2007, pp. 180–183). Using a rough sphere with a contact angle of $120^{\circ }$ , Aristoff & Bush (J. Fluid Mech., vol. 619, 2009, pp. 45–78) showed that there are four different cavity shapes dependent on the Bond and Weber numbers (i.e., quasistatic, shallow, deep and surface). We experimentally alter the Bond number, Weber number and contact angle of smooth spheres and find two key additions to the literature: (1) cavity shape also depends on the contact angle; (2) the absence of a splash crown at low Weber number results in cavity formation below the predicted critical velocity. In addition, we use alternate scales in defining the Bond, Weber and Froude numbers to predict the cavity shapes and scale pinch-off times for various impacting bodies (e.g., spheres, multidroplet streams and jets) on the same plots, merging the often separated studies of solid–liquid and liquid–liquid impact in the literature.

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