scholarly journals Dynamic Wetting on Moving Surfaces: A Molecular Dynamics Study

2012 ◽  
Author(s):  
Konstantinos Ritos ◽  
Nishanth Dongari ◽  
Yonghao Zhang ◽  
Jason M. Reese
Keyword(s):  
Molecular Dynamics ◽  
Contact Angle ◽  
Capillary Number ◽  
Contact Angle Hysteresis ◽  
Hydrophobic Surface ◽  
Md Simulations ◽  
Dynamic Wetting ◽  
Water Contact ◽  
Liquid Flows ◽  
Insight Into

We report molecular dynamics (MD) simulations of the dynamic wetting of nanoscale droplets on moving surfaces. The dynamic water contact angle and contact angle hysteresis are measured as a function of capillary number on smooth silicon and graphite surfaces. The hydrogen bonding and density profile variations are also reported, and the width of the water depletion layer is evaluated for droplets on three different static surfaces: silicon, graphite and a fictitious super-hydrophobic surface. Our results show that molecular displacements at the contact line are mostly influenced by interactions with the solid surface, while the viscous dissipation effects induced through the movement of surfaces are found to be negligible, especially for hydrophobic surfaces. This finding is in contrast with the wetting dynamics of macroscale droplets, which show significant dependence on the capillary number. This study may yield new insight into surface-wettability characteristics of nano droplets, in particular, developing new boundary conditions for continuum solvers for liquid flows in micro- and nanoscale devices.

scholarly journals One-Step Preparation of Durable Super-Hydrophobic MSR/SiO2 Coatings by Suspension Air Spraying

Micromachines ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 677 ◽  
Author(s):  
Zhengyong Huang ◽  
Wenjie Xu ◽  
Yu Wang ◽  
Haohuan Wang ◽  
Ruiqi Zhang ◽  
...  
Keyword(s):  
Contact Angle ◽  
Adhesion Strength ◽  
Contact Angle Hysteresis ◽  
Surface Hardness ◽  
Hierarchical Structures ◽  
Hydrophobic Surface ◽  
Water Contact ◽  
Hydrophobic Coating ◽  
Mechanical Durability ◽  
One Step

In this study, we develop a facial one-step approach to prepare durable super-hydrophobic coatings on glass surfaces. The hydrophobic characteristics, corrosive liquid resistance, and mechanical durability of the super-hydrophobic surface are presented. The as-prepared super-hydrophobic surface exhibits a water contact angle (WCA) of 157.2° and contact angle hysteresis of 2.3°. Mico/nano hierarchical structures and elements of silicon and fluorine is observed on super-hydrophobic surfaces. The adhesion strength and hardness of the surface are determined to be 1st level and 4H, respectively. The coating is, thus, capable of maintaining super-hydrophobic state after sand grinding with a load of 200 g and wear distances of 700 mm. The rough surface retained after severe mechanical abrasion observed by atomic force microscope (AFM) microscopically proves the durable origin of the super-hydrophobic coating. Results demonstrate the feasibility of production of the durable super-hydrophobic coating via enhancing its adhesion strength and surface hardness.

Fabrication of a Super-Hydrophobic Micro-Nanoporous Aluminum Surface by Anodic Oxidation

2012 ◽  
Vol 200 ◽  
pp. 190-193 ◽  
Author(s):  
Ruo Mei Wu ◽  
Shu Quan Liang ◽  
Hong Chen ◽  
An Qiang Pan ◽  
Hai Yun Jiang ◽  
...  
Keyword(s):  
Contact Angle ◽  
Stearic Acid ◽  
Contact Angle Hysteresis ◽  
Hydrophobic Surface ◽  
Aluminum Surface ◽  
Anodized Aluminum ◽  
Water Contact ◽  
Static Water ◽  
Superhydrophobic Property ◽  
Device Associated Infection

A novel and stable super-hydrophobic film was prepared by stearic acid (C18H36O2), which was chemically adsorbed onto the anodized aluminum surface. The maximum static water contact angle (WCA) of the super-hydrophobic surface was 157.5º ± 2.0º and the contact angle hysteresis was less than 3º. The superhydrophobic property is attributed to the micro-nanoporous surface morphology and stearic acid. The pore size on the surface of anodic aluminum oxide is an important factor for controlling the superhydrophobic adhesiveness. The superhydrophobic surface is a factor to reduce device-associated infection and can be used in metal packaging practice.

Osteoconductivity of Superhydrophilic Ti- and Zr-Alloy for Biomedical Application

2016 ◽  
Vol 879 ◽  
pp. 2524-2527
Author(s):  
Masazumi Okido ◽  
Kensuke Kuroda
Keyword(s):  
Contact Angle ◽  
Water Contact Angle ◽  
Strong Influence ◽  
Biomedical Application ◽  
Hydrophobic Surface ◽  
Hydrophilic Surface ◽  
Water Contact ◽  
Zr Alloy ◽  
Zr Alloys

Surface hydrophilicity is considered to have a strong influence on the biological reactions of bone-substituting materials. However, the influence of a hydrophilic or hydrophobic surface on the osteoconductivity is not completely clear. In this study, we produced super-hydrophilic and hydrophobic surface on Ti-and Zr-alloys. Hydrothermal treatment at 180 oC for 180 min. in the distilled water and immersion in x5 PBS(-) brought the super-hydrophilic surface (water contact angle < 10 (deg.)) and heat treatment of as-hydrothermaled the hydrophobic surface. The osteoconductivity of the surface treated samples with several water contact angle was evaluated by in vivo testing. The surface properties, especially water contact angle, strongly affected the osteoconductivity and protein adsorbability, and not the surface substance.

scholarly journals A Simple Method to Create Superhydrophobic Aluminium Surfaces

2012 ◽  
Vol 706-709 ◽  
pp. 2874-2879 ◽  
Author(s):  
R. Jafari ◽  
Masoud Farzaneh
Keyword(s):  
Contact Angle ◽  
Stearic Acid ◽  
Synergistic Effects ◽  
Low Cost ◽  
Contact Angle Hysteresis ◽  
Spray Coating ◽  
Superhydrophobic Surfaces ◽  
Water Contact ◽  
Simple Method ◽  
Static Contact

Superhydrophobic surfaces were prepared using a very simple and low-cost method by spray coating. A high static water contact angle of about 154° was obtained by deposition of stearic acid on an aluminium alloy. However, this coating demonstrated a high contact angle hysteresis (~ 30º). On the other hand, superhydrophobic surfaces with a static contact angle of about 162º and 158º, and a low contact angle hysteresis of about 3º and 5º were respectively obtained by incorporating nanoparticles of SiO2and CaCO3in stearic acid. The excellent resulting hydrophobicity is attributed to the synergistic effects of micro/nanoroughness and low surface energy. A study of the wettability of these surfaces at temperatures ranging from 20 to-10 °C showed that the superhydrophobic surface becomes rather hydrophobic at supercooled temperatures.

scholarly journals Preparation of Superhydrophobic Steel Surfaces with Chemical Stability and Corrosion

Coatings ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 398 ◽  
Author(s):  
Chongwei Du ◽  
Xiaoyan He ◽  
Feng Tian ◽  
Xiuqin Bai ◽  
Chengqing Yuan
Keyword(s):  
Contact Angle ◽  
Corrosion Resistance ◽  
Carbon Steel ◽  
Chemical Stability ◽  
Superhydrophobic Surface ◽  
Contact Angle Hysteresis ◽  
Water Contact ◽  
Simple Method ◽  
Q235 Carbon Steel ◽  
Steel Surfaces

Corrosion seriously limits the long-term application of Q235 carbon steel. Herein, a simple fabrication method was used to fabricate superhydrophobic surfaces on Q235 carbon steel for anticorrosion application. The combination of structure and the grafted low-surface-energy material contributed to the formation of superhydrophobic steel surfaces, which exhibited a water contact angle of 161.6° and a contact angle hysteresis of 0.8°. Meanwhile, the as-prepared superhydrophobic surface showed repellent toward different solutions with pH ranging from 1 to 14, presenting excellent chemical stability. Moreover, the acid corrosive liquid (HCl solution with pH of 1) maintained sphere-like shape on the as-prepared superhydrophobic surface at room temperature, indicating superior corrosion resistance. This work provides a simple method to fabricate superhydrophobic steel surfaces with chemical stability and corrosion resistance.

An Effective Route to the Fabrication of Super-Hydrophobic Surfaces Combined by Micromolding and Photograft Polymerization Methods

2012 ◽  
Vol 152-154 ◽  
pp. 9-13
Author(s):  
Jing Tao Yang ◽  
Lei Wang ◽  
Zheng Yuan Huo ◽  
Jie Feng ◽  
Feng Chen ◽  
...  
Keyword(s):  
Contact Angle ◽  
Water Contact Angle ◽  
Energy Dispersive Spectrometer ◽  
Hydrophobic Surface ◽  
Body Structure ◽  
Critical Difference ◽  
Water Contact ◽  
Methacrylate Monomers ◽  
Polypropylene Matrix ◽  
Morphology Characterization

A super-hydrophobic surface on the polypropylene matrix was fabricated via micromolding and photograft polymerization. A micro-convex body structure was molded by etching templates. The water contact angle could be increased to 138°. The fluoro methacrylate monomers were further grafted to the surface through UV-induced photograft polymerization. The morphology characterization and the spectroanalysis indicated that the rough hierarchical structure (confirmed by scanning electron microscope) and the grafted fluoropolymers (measured by fourier transform infrared spectrum and X-ray energy dispersive spectrometer) made a critical difference. A water contact angle of 160° was arrived.

Hydrophobic Performance of Core/Shell Nanoarrays Modified by Stearic Acid

2020 ◽  
Vol 15 (2) ◽  
pp. 264-268
Author(s):  
Hongxing Han ◽  
Lin Pan ◽  
Manying Zhang ◽  
Lei Zhao ◽  
Zhifeng Liu
Keyword(s):  
Contact Angle ◽  
Stearic Acid ◽  
Water Contact Angle ◽  
Zno Nanorods ◽  
Hydrophobic Surface ◽  
Optical Transmittance ◽  
Surface Hydrophobicity ◽  
Core Shell ◽  
Water Contact ◽  
Angle Measurements

In this paper, we successfully prepare hydrophobic surface of ZnO/ZnS nanorods arrays modified by stearic acid. The morphology, microstructure, optical transmittance and self-cleaning property are examined by SEM, XRD, UV-vis and water contact angle measurements, respectively. The ZnO/ZnS core/shell nanoarrays shows a higher value of water contact angle in compare with that of pure ZnO nanorods arrays. After treatment by stearic acid, the resulting ZnO/ZnS nanostructure exhibits the best hydrophobicity with water droplets about 146.5 . The results show that the surface hydrophobicity of ZnO/ZnS nanoarrays can be improved by using stearic acid with low-surface-energy.

Nanomechanical and Friction Properties of Ultrathin Amorphous Carbon Films Studied by Molecular Dynamics Analysis

2010 ◽  
Author(s):  
N. Wang ◽  
K. Komvopoulos
Keyword(s):  
Molecular Dynamics ◽  
Amorphous Carbon ◽  
Md Simulations ◽  
Carbon Films ◽  
Magnetic Storage ◽  
Disk Drives ◽  
Magnetic Medium ◽  
High Density Magnetic Recording ◽  
Protective Overcoats ◽  
Insight Into

An ultrathin (<4 nm) film of amorphous carbon (a-C) is used in contemporary disk drives to protect the magnetic medium of the hard disk from corrosion and mechanical wear due to intermittent impact of the low-flying magnetic head. Because of increasing demands for much higher magnetic storage densities (i.e., >10 Tbits/in2), the a-C film thickness must be decreased to <2 nm. However, the tribological and mechanical properties of such thin a-C films are not well understood and, moreover, are extremely difficult to determine experimentally. The objective of this study was to obtain insight into the tribological behavior of ultrathin a-C films by performing molecular dynamics (MD) simulations. MD results of the hardness and friction properties of nanometer-thick a-C films are interpreted in terms of the ratio of tetrahedral-to-trigonal carbon atom hybridization. A critical thickness for the effective protection of the magnetic medium by the a-C film is estimated from MD results. The results of this study elucidate the nanomechanical and nanotribological properties of ultrathin a-C films used as protective overcoats in extremely-high-density magnetic recording.

Temperature profiles and heat fluxes observed in molecular dynamics simulations of force-driven liquid flows

2017 ◽  
Vol 19 (16) ◽  
pp. 10317-10325 ◽  
Author(s):  
Jafar Ghorbanian ◽  
Ali Beskok
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Md Simulations ◽  
Heat Fluxes ◽  
Temperature Profiles ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
Liquid Flows ◽  
Non Equilibrium

This paper concentrates on the unconventional temperature profiles and heat fluxes observed in non-equilibrium molecular dynamics (MD) simulations of force-driven liquid flows in nano-channels.

Sign in / Sign up

Export Citation Format

Share Document