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superhydrophobic-surfaces
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Selective fabrication of robust and multifunctional super nonwetting surfaces by diverse modifications of zirconia-ceria nanocomposites
, Article Langmuir ; Volume 38, Issue 30 , 2022 , Pages 9195-9209 ; 07437463 (ISSN) ; Zandi, A ; Ghazanfari, M. H ; Khezrnejad, A ; Fatemi, M ; Molaei Dehkordi, A ; Sharif University of Technology
American Chemical Society
2022
Abstract
The creation of surfaces with various super nonwetting properties is an ongoing challenge. We report diverse modifications of novel synthesized zirconia-ceria nanocomposites by different low surface energy agents to fabricate nanofluids capable of regulating surface wettability of mineral substrates to achieve selective superhydrophobic, superoleophobic-superhydrophilic, and superamphiphobic conditions. Surfaces treated with these nanofluids offer self-cleaning properties and effortless rolling-off behavior with sliding angles ≤7° for several liquids with surface tensions between 26 and 72.1 mN/m. The superamphiphobic nanofluid coating imparts nonstick properties to a solid surface whereby...
Condensation enhancement on hydrophobic surfaces using electrophoretic method and hybrid paint coating
, Article Heat Transfer Engineering ; Volume 42, Issue 18 , 2021 , Pages 1557-1572 ; 01457632 (ISSN) ; Moosavi, A ; Najafkhani, H ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
Condensation heat transfer on stainless steel tube utilizing superhydrophobic coatings was investigated. The electrophoretic deposition and spraying methods were employed to coat the tubes’ outer surface. The mixture that was synthesized for spray coating was a hybrid paint. It incorporated polyurethane matrix and a colloidal suspension containing organic nanoparticles. The hybrid paint had a proper adhesion to the substrate which caused more durability compared to the electrophoretic coating. The agglomeration of nanoparticles in the hybrid paint caused the formation of particles with larger size compared to the particles in the electrophoretic coating. Consequently, contact angle...
Mechanically stable superhydrophobic nanostructured aluminum mesh with reduced water surface friction
, Article Nanotechnology ; Volume 32, Issue 19 , 2021 ; 09574484 (ISSN) ; Afzali, N ; Taghvaei, N ; Moosavi, A ; Sharif University of Technology
IOP Publishing Ltd
2021
Abstract
Superhydrophobic surfaces demonstrate significant characteristics which make them suitable for a wide variety of applications. In this study, we propose a facile, one-step, and cost-effective anodizing scheme using aluminum nitrate/stearic acid mixture solution to create a superhydrophobic surface on an aluminum mesh. The surface outperforms the surface anodized by the widely used oxalic acid solution in terms of superhydrophobicity and water-surface friction behavior. The proposed surface reduced the friction by 11% on average respective to the surface prepared by oxalic acid. The durability of the introduced superhydrophobic surface has also been investigated. The proposed surface retained...
Influence of new superhydrophobic micro-structures on delaying ice formation
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 595 , 2020 ; Taeibi Rahni, M ; Javadi, K ; Davoudian, S. H ; Miller, R ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Drop motion on different types of new proposed micro-structure surfaces has been numerically investigated to find the optimum structure in view point of ice formation delaying. The droplet automatically moves on the inclined surfaces due to gravity forces. To validate the numerical algorithm, three different bench mark problems have been considered. The results indicate that the present algorithm is trustable for the presented numerical simulations. Then the validated numerical approach has been used to simulate droplet motion on nine proposed superhydrophobic surfaces in the same conditions. Comparison the drop motion on different micro-structure surfaces at different time indicate that...
Condensation enhancement on hydrophobic surfaces using electrophoretic method and hybrid paint coating
, Article Heat Transfer Engineering ; 26 August , 2020 ; Moosavi, A ; Najafkhani, H ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
Condensation heat transfer on stainless steel tube utilizing superhydrophobic coatings was investigated. The electrophoretic deposition and spraying methods were employed to coat the tubes’ outer surface. The mixture that was synthesized for spray coating was a hybrid paint. It incorporated polyurethane matrix and a colloidal suspension containing organic nanoparticles. The hybrid paint had a proper adhesion to the substrate which caused more durability compared to the electrophoretic coating. The agglomeration of nanoparticles in the hybrid paint caused the formation of particles with larger size compared to the particles in the electrophoretic coating. Consequently, contact angle...
A comprehensive review on recent advances in superhydrophobic surfaces and their applications for drag reduction
, Article Progress in Organic Coatings ; Volume 140 , March , 2020 ; Pakzad, H ; Moosavi, A ; Nouri Borujerdi, A ; Sharif University of Technology
Elsevier B. V
2020
Abstract
Nowadays, superhydrophobic surfaces have attracted a lot of interest because of the wide range of applications in industries. These surfaces can significantly reduce the drag force due to the formation of air gaps between the substrate and liquid interface. The present review mainly focuses on the very recent progresses in the drag reduction studies using superhydrophobic surfaces. Also, a brief discussion about the mathematical modeling and the theories of superhydrophobic surfaces, natural water repellent surfaces, various fabrication techniques with advantages and disadvantages of each method and different properties of the fabricated surfaces in industrial applications is presented....
Fabrication of durable superhydrophobic surfaces using PDMS and beeswax for drag reduction of internal turbulent flow
, Article Applied Surface Science ; Volume 513 , 2020 ; Liravi, M ; Moosavi, A ; Nouri Borujerdi, A ; Najafkhani, H ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Nowadays, one of the biggest concerns in the world is increasing the CO2 emissions and global warming due to the over-consumption of fossil fuels. In addition, under the intense market competition, the demand for more efficient systems with higher performance and lower energy consumption has escalated. Since the drag force contributes to a considerable percentage of the energy loss and reducing the performance, a large number of studies have been conducted to improve the surface characteristics and, subsequently, declining the drag force. Making the surface superhydrophobic is one of the most effective ways for this purpose. In this work, two different superhydrophobic surfaces using SiO2...
Droplet condensation and jumping on structured superhydrophobic surfaces
, Article International Journal of Heat and Mass Transfer ; Volume 134 , 2019 , Pages 680-693 ; 00179310 (ISSN) ; Moosavi, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
A complete cycle of droplet nucleation, growth, coalescence and jumping on different textured hydrophobic and superhydrophobic surfaces is studied for the first time, using a 2-D double distribution function thermal lattice Boltzmann method. First, droplet nucleation mechanism on smooth and rough surfaces is studied in detail. The results reveal the presence of cooled vapor layer instability in the condensation on completely smooth surfaces. However, on the rough surfaces and near the roughness a completely different mechanism is observed and the nucleation occurs on the roughness wedges. Also, the condensation on different textured surfaces with nominal contact angles θa=90°,120°,155° is...
Wettability properties of PTFE/ZnO nanorods thin film exhibiting UV-resilient superhydrophobicity
, Article Applied Surface Science ; Volume 341 , 2015 , Pages 92-99 ; 01694332 (ISSN) ; Ebrahimi, M ; Nourmohammadi, A ; Moshfegh, A. Z ; Sharif University of Technology
Elsevier
2015
Abstract
In this research, initially anodization process was used to fabricate ZnO nanorods on Zn substrate and then RF sputtering technique was applied to grow a thin layer of polytetrafluoroethylene (PTFE, Teflon) on the coated ZnO nanorods for producing a superhydrophobic surface. According to scanning electron microscopy (SEM) observations, ZnO nanorods were formed with average diameter and length of about ∼180 nm and 14 μm, respectively. Superhydrophilic property of ZnO nanorods and superhydrophobic property of PTFE/ZnO nanorods was investigated by water contact angle (WCA) measurements. It was found that the contact angle varied with the PTFE deposition time. The highest contact angle...
Use of Engineered Surfaces to Increase Dropwise Condensation
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
The limitation of energy resources and the increasing energy consumption has led researchers to look more closely at industrial processes such as condensation to improve these processes and prevent energy wastage. Increasing the efficiency of the condensation process will improve the performance of energy systems, save energy and protect the environment. In this research, various surfaces are fabricated, each of which in some way makes it possible to improve the condensation process. To perform the condensation test, the condensation surface, which is placed in the condensation test chamber, is cooled with a heat exchanger. Due to the high temperature of water vapor, many of the surfaces...
Fabrication and Investigation of Condensation Performance of Hybrid and Solid – Infused Surfaces
, M.Sc. Thesis Sharif University of Technology ; Mousavi, Ali (Supervisor) ; Aryanpour, Masood (Supervisor)
Abstract
Increasing energy consumption and limited energy resources are instances of the concerns of human societies and environmentalists today. The condensation process, as one of the most important processes in the industry, plays an important role in saving and regeneration the existing energy. Nowdays, surface optimization is one of the modern ways to improve condensation.In this research, two methods have been used to construct surfaces useful for enhancement of droplet condensation, including hybrid surfaces and solid infused surfaces. In the construction of hybrid surfaces, superhydrophobic coating with silica nanoparticles based on hydroxyl acrylic resin was used. The superhydrophilic parts...
Dynamics and Heat transfer of Two-phase Non-Newtonian Fluids in Superhydrophobic Channels
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
When the fluid passes through the microchannel, some energy is lost due to drag force and pressure drop. One of the methods used in the last few decades to optimize energy consumption is creating superhydrophobic surfaces in microchannels. These surfaces, with their features such as increasing the contact angle and reducing the contact angle hysteresis, can reduce energy loss, which is due to the presence of unevenness on the surface, and by trapping air and creating a two-phase flow, they reduce the drag force. On the other hand, the air trapped inside these irregularities will also affect the heat transfer of the passing fluid in the microchannel, which by creating resistance in the...
Using the Engineered Surface to Reduce the Adhesion Force of Ice to the Surface and Increase the Freezing Time of Water on the Surface
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor) ; Hosseini, Vahid (Supervisor)
Abstract
Ice formation upon various surfaces could lead to many industry problems and result in unpleasant accidents. For instance, the formation of ice on wind turbine blades or airplanes/helicopter wings could cause catastrophic disasters. The methods used to address this problem usually require exogenous energy consumption or anti-ice ingredients. The energy or anti-ice ingredients usage has adverse environmental effects and should be replaced with better approaches. One of these approaches is utilizing modified anti-ice surfaces. In this method, by modifying surface features, such as physical asperities and surface energy, the icing time of the surface could be prolonged. These surfaces are...
Molecular Dynamic Simulation of Friction Reduction in Two-Phase Flows with Nanostructures and Study of the effect of Electric Field
, M.Sc. Thesis Sharif University of Technology ; Kazemzadeh Hannani, Siamak (Supervisor) ; Moosavi, Ali (Supervisor)
Abstract
The use of superhydrophobic surfaces is one the most promising methods for reducing the friction and increasing the flow rate in fluid transfer systems. Since in such systems the surface structure plays a key role, in the first part of this study, the performance of the hierarchical nanostructures is explored. These nanostructures are inspired by the superhydrophobic surface of the lotus leaf. The flow is considered between two walls with hierarchical nanostructures and simulate the system via the molecular dynamics (MD) method. The size of the nanostructures and the distance between them have been studied to find whether a design with maximum flow rate exists. The nanostructures have two...
Super Hydrophobic Ni Coating on Steel by Electrodeposition Method
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
In this study, the properties of super-hydrophobic Ni coating on carbon steel including wetting behavior and corrosion resistance of Nickel coatings deposited on the steel substrate were investigated. For this purpose, Nickel coatings deposited by electrodeposition method in deferent current density (10,20,30,50, 70 mA /cm2) in bath containing 1.5 mol of ethylene de-ammonium de-chloride, 0.5 mol H3BO3, 1 mol Nicl2.6H2o and then immersed in a bath containing 0.01 mol per liter myristic acid and ethanol for 24 hours and then placed in the room temperature for 14 days. Deferent tests were used for characterization, wettability properties, corrosion behavior and morphology of Ni coatings. The...
Fabrication of Superhydrophobic Coating to Reduce Drag force with Anti-Corrosion and Anti-biofouling Properties
, M.Sc. Thesis Sharif University of Technology ; Mousavi, Ali (Supervisor)
Abstract
Growth of the fuel consumption in the world and the greenhouse effect of its pollution get industrial managers and environmental activities attention. Skin drag force has a significant role in energy uses. The drag reduction property of superhydrophobic surfaces shows a new approach for investigators to reduce energy uses. Surface with 150° contact angle called superhydrophobic surface.In this project, a superhydrophobic coating is developed based on acrylic hydroxyl resin by silica nanoparticles. This coating can be sprayed on any surface. Using the Iron oxid particles and silica nanoparticles together produces hierarchical micro-nano structures. This coating has a 160.1° contact angle on...
Re-Creation of Lost Gas Layer on Superhydrophobic Surfaces with Micro/Nanostructures
, M.Sc. Thesis Sharif University of Technology ; Mosavi, Ali (Supervisor)
Abstract
Due to their unique characteristics, such as drag reduction, anti-fouling, and enhancing condensation, hydrophobic and superhydrophobic surfaces have attracted a lot of attention in the past decades. Since approximately 4% of the fossil fuel usage and 14-19% of the air pollution (including greenhouse gases, sulfur, and so forth) are attributed to naval activities, and the dominant form of drag on vessels is friction, drag reduction will not only reduce the cost and usage of fossil fuels, but it will also have numerous environmental benefits
Fabrication of Transparent, Superhydrophobic and Self-cleaning Coatings for Glass Substrate Using Nano-particles
, M.Sc. Thesis Sharif University of Technology ; moosavi, Ali (Supervisor)
Abstract
Although using solar energies have some limitations, such as low efficiency, require a large space and high starting cost, they are one of the most attractive source of energies. The reasons that cause efficiency of the solar panels decrease are contamination of dust particles on them and formation of water droplet on solar panel surface due to humidity of the air. Also, a solar panel can absorb only 25% of incident light and the others are reflected by the cover glass. Therefore, fabrication of a self-cleaning surface that can inhibit the aggregation of dust particles and also transparent that doesn’t reflect the incident light is crucial.In this work, we aim to obtain a transparent,...
Fabrication of Superhydrophobic Surfaces to Decrease Pressure Drop through the Galvanized Pipe and Study about Feasibility of the Fabricated Surface to Use for Non-newtonian Fluid
, M.Sc. Thesis Sharif University of Technology ; Mousavi, Ali (Supervisor) ; Nouri boroojerdi, Ali (Supervisor)
Abstract
Nowdays, one of the most important concerns for scientists is increasing CO2 emmisions and global warming. To overcome this problem, a large number of studies have been carried out to improve energy system performance and reducing the overall energy consumption. One solution to this problem is using the superhydrophobic surfaces with contact angle larger than 150°.In this study, we try to reduce the pressure drop through the galvanized pipes. So, by reducing the pressure drop, power required for pumps can be reduced. To this end, two different coatings by silica nano-particles which were modified with first hydrophobic agent are used. In first coating which is named as PS coating, stearic...
Synthesis and Properties of Functional Super Hydrophobic TiO2
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Titanium nano-oxide (TiO2) coatings have been used for self-cleaning, antimicrobial, and dust-proof designs. The degree of wetting of a solid surface with water in humid air depends on how the surface tension of the existing phases relates. The ratio between these tensions estimates the contact angle between a drop of water and the surface on which it is placed. A contact angle above 150 º is essential for surface overflow. In this study, 18 different combinations of titanium oxide and FAS, PDMS and PMS nanoparticles were obtained with a static contact angle of 165 to 150 º and a dynamic contact angle of 7 º.1 to 4.5 º. Following the measurement of water droplet slip speed on a sloping...