Showing papers on "Contact angle published in 2014"
TL;DR: In this article, a novel polyethersulfone (PES) mixed matrix nanofiltration membrane containing graphene oxide (GO) nanoplates was prepared via the phase inversion method.
826 citations
TL;DR: The potentiodynamic polarization and electrochemical impedance spectroscopy test shows that the as-prepared superhydrophobic surface has excellent corrosion resistance that can provide effective protection for the bare Cu substrate.
Abstract: A novel method for controllable fabrication of a superhydrophobic surface with a water contact angle of 162 ± 1° and a sliding angle of 3 ± 0.5° on copper substrate is reported in this Research Article. The facile and low-cost fabrication process is composed from the electrodeposition in traditional Watts bath and the heat-treatment in the presence of (heptadecafluoro-1,1,2,2-tetradecyl) triethoxysilane (AC-FAS). The superhydrophobicity of the fabricated surface results from its pine-cone-like hierarchical micro-nanostructure and the assembly of low-surface-energy fluorinated components on it. The superhydrophobic surface exhibits high microhardness and excellent mechanical abrasion resistance because it maintains superhydrophobicity after mechanical abrasion against 800 grit SiC sandpaper for 1.0 m at the applied pressure of 4.80 kPa. Moreover, the superhydrophobic surface has good chemical stability in both acidic and alkaline environments. The potentiodynamic polarization and electrochemical impedance ...
369 citations
TL;DR: In this article, various categories of materials for the fabrication of hydrophilic, hydrophobic, oleophobic, amphiphobic and multifunctional coatings and their synthesis routes have been discussed.
Abstract: This review article exemplifies the importance of self-cleaning materials and coatings. Self-cleaning coatings are becoming an integral part of our daily life because of their utility in various applications such as windows, solar panels, cements, and paints. In this review, various categories of materials for the fabrication of hydrophilic, hydrophobic, oleophobic, amphiphobic and multifunctional coatings and their synthesis routes have been discussed. Furthermore, different natural organisms exhibiting superhydrophobic behaviour have been analysed. This review also covers the fundamentals of self-cleaning attributes such as water contact angle, surface energy, and contact angle hysteresis.
368 citations
TL;DR: G/Cu exhibits the highest surface energy immediately after synthesis, and the surface energy decreases after airborne contamination occurs, suggesting the root cause of intrinsically mild polarity of G/Cu surface is discussed.
Abstract: Because of the atomic thinness of graphene, its integration into a device will always involve its interaction with at least one supporting substrate, making the surface energy of graphene critical to its real-life applications. In the current paper, the contact angle of graphene synthesized by chemical vapor deposition (CVD) was monitored temporally after synthesis using water, diiodomethane, ethylene glycol, and glycerol. The surface energy was then calculated based on the contact angle data by the Fowkes, Owens–Wendt (extended Fowkes), and Neumann models. The surface energy of fresh CVD graphene grown on a copper substrate (G/Cu) immediately after synthesis was determined to be 62.2 ± 3.1 mJ/m2 (Fowkes), 53.0 ± 4.3 mJ/m2 (Owens–Wendt) and 63.8 ± 2.0 mJ/m2 (Neumann), which decreased to 45.6 ± 3.9, 37.5 ± 2.3, and 57.4 ± 2.1 mJ/m2, respectively, after 24 h of air exposure. The ellipsometry characterization indicates that the surface energy of G/Cu is affected by airborne hydrocarbon contamination. G/Cu ex...
360 citations
TL;DR: In this article, a method for the measurement of the contact angle between immiscible fluids at the pore scale at reservoir conditions (10 MPa and 50 C) inside a quarry limestone through the use of X-ray microtomography is presented.
320 citations
TL;DR: In this paper, fly-eye bio-inspired inorganic nanostructures are synthesized via a two-step self-assembly approach, which have low contact angle hysteresis and excellent anti-fogging properties, and are promising candidates for anti-freezing/fogging materials to be applied in extreme and hazardous environments
Abstract: Fly-eye bio-inspired inorganic nanostructures are synthesized via a two-step self-assembly approach, which have low contact angle hysteresis and excellent anti-fogging properties, and are promising candidates for anti-freezing/fogging materials to be applied in extreme and hazardous environments
268 citations
TL;DR: The synthesis of large area MoS2 thin films on insulating substrates (SiO2/Si and Al2O3) with different surface morphology via vapor phase deposition by varying the growth temperatures sheds light on theMoS2-water interaction that is important for the development of devices based on MoS 2 coated surfaces for microfluidic applications.
Abstract: MoS2 is an important member of the transition metal dichalcogenides that is emerging as a potential 2D atomically thin layered material for low power electronic and optoelectronic applications. However, for MoS2 a critical fundamental question of significant importance is how the surface energy and hence the wettability is altered at the nanoscale in particular, the role of crystallinity and orientation. This work reports on the synthesis of large area MoS2 thin films on insulating substrates (SiO2/Si and Al2O3) with different surface morphology via vapor phase deposition by varying the growth temperatures. The samples were examined using transmission electron microscopy and Raman spectroscopy. From contact angle measurements, it is possible to correlate the wettability with crystallinity at the nanoscale. The specific surface energy for few layers MoS2 is estimated to be about 46.5 mJ/m2. Moreover a layer thickness-dependent wettability study suggests that the lower the thickness is, the higher the conta...
247 citations
TL;DR: The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern design, particularly under higher humidity conditions in the presence of noncondensable gases (NCG), a condition that is more challenging for maintaining sustained DWC.
Abstract: Dropwise condensation (DWC) heat transfer depends strongly on the maximum diameter (Dmax) of condensate droplets departing from the condenser surface. This study presents a facile technique implemented to gain control of Dmax in DWC within vapor/air atmospheres. We demonstrate how this approach can enhance the corresponding heat transfer rate by harnessing the capillary forces in the removal of the condensate from the surface. We examine various hydrophilic-superhydrophilic patterns, which, respectively, sustain and combine DWC and filmwise condensation on the substrate. The material system uses laser-patterned masking and chemical etching to achieve the desired wettability contrast and does not employ any hydrophobizing agent. By applying alternating straight parallel strips of hydrophilic (contact angle ∼78°) mirror-finish aluminum and superhydrophilic regions (etched aluminum) on the condensing surface, we show that the average maximum droplet size on the less-wettable domains is nearly 42% of the width of the corresponding strips. An overall improvement in the condensate collection rate, up to 19% (as compared to the control case of DWC on mirror-finish aluminum) was achieved by using an interdigitated superhydrophilic track pattern (on the mirror-finish hydrophilic surface) inspired by the vein network of plant leaves. The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern design, particularly under higher humidity conditions in the presence of noncondensable gases (NCG), a condition that is more challenging for maintaining sustained DWC.
238 citations
TL;DR: In this article, a super-hydrophobic surface with self-cleaning was successfully deposited on AZ91D magnesium alloy by the nickel plating process, and the surface morphologies, chemical composition, wettability and corrosion resistance were characterized by means of SEM, FT-IR, water contact angle and electrochemical impedance spectroscopy (EIS) measurements.
230 citations
TL;DR: A review of the published articles on contact angles and summarizes the views of the both sides can be found in this article, where the weak and strong sides of both three-phase contact line and contact area approaches are discussed in detail and some practical conclusions are drawn.
229 citations
TL;DR: In this article, the anti-icing properties of hydrophilic, hydrophobic and super-hydrophobic surfaces/coatings were evaluated using a custom-built apparatus based on zero-degree cone test method.
TL;DR: In this article, anatase and amorphous TiO2 nanoparticles were used to improve recovery of heavy oil from sandstone cores, and contact angle measurements were performed on the rock surface before and after treatment with the nanoparticle solution.
Abstract: Anatase and amorphous TiO2 nanoparticles were used to improve recovery of heavy oil from sandstone cores. Before performing core floods, the stability of nanoparticles at different salinities was tested using ζ potential and ultraviolet–visible (UV–vis) methods. While water recovered only 49% of the oil in the core flood experiments, 0.01% anatase structure solution recovered 80% of the oil after injecting two pore volumes at optimum conditions. To understand the mechanism responsible for improved recovery, contact angle measurements were performed on the rock surface before and after treatment with the nanoparticle solution. Contact angle measurements showed that the rock wettability changed from oil-wet to water-wet conditions after treatment with nanoparticles. In 0.01% concentration, scanning electron microscopy (SEM) results showed homogeneous deposition of nanoparticles onto the core plug surface and a few nanorods with a diameter about 60 nm were observed. Energy-dispersive spectrometry (EDS) confi...
TL;DR: In this article, the authors used surface cleaning methods typically prescribed in the surface chemistry community and found that the water contact angle θ on a clean quartz substrate is low, 0-30°, and that θ increases with pressure.
TL;DR: The direct contact membrane distillation (DCMD) tests demonstrate that the newly developed membranes are able to present stable high performance over 50 h of testing time, and the superhydrophobic selective layer exhibits excellent durability in ultrasonic treatment and a continuous DCMD test.
Abstract: The practical application of membrane distillation (MD) for water purification is hindered by the absence of desirable membranes that can fulfill the special requirements of the MD process. Compared to the membranes fabricated by other methods, nanofiber membranes produced by electrospinning are of great interest due to their high porosity, low tortuosity, large surface pore size, and high surface hydrophobicity. However, the stable performance of the nanofiber membranes in the MD process is still unsatisfactory. Inspired by the unique structure of the lotus leaf, this study aimed to develop a strategy to construct superhydrophobic composite nanofiber membranes with robust superhydrophobicity and high porosity suitable for use in MD. The newly developed membrane consists of a superhydrophobic silica-PVDF composite selective skin formed on a polyvinylidene fluoride (PVDF) porous nanofiber scaffold via electrospinning. This fabrication method could be easily scaled up due to its simple preparation procedures. The effects of silica diameter and concentration on membrane contact angle, sliding angle, and MD performance were investigated thoroughly. For the first time, the direct contact membrane distillation (DCMD) tests demonstrate that the newly developed membranes are able to present stable high performance over 50 h of testing time, and the superhydrophobic selective layer exhibits excellent durability in ultrasonic treatment and a continuous DCMD test. It is believed that this novel design strategy has great potential for MD membrane fabrication.
TL;DR: The characterization results suggest that the electrospun composite nanofibers are constructed by carbon chains interpenetrated through a linear network of 3-dimensional SiO2 through which the inherent property of high porosity allows oil-water separation to be performed in a gravity-driven process with high-flux.
Abstract: A novel free-standing and flexible electrospun carbon–silica composite nanofibrous membrane is newly introduced. The characterization results suggest that the electrospun composite nanofibers are constructed by carbon chains interpenetrated through a linear network of 3-dimensional SiO2. Thermogravimetric analysis indicates that the presence of insulating silica further improve the thermal resistance of the membrane. Additionally, the mechanical strength test shows that the membrane’s toughness and flexibility can be enhanced if the concentration of SiO2 is maintained below 2.7 wt %. Thermal and chemical stability test show that the membrane’s wettability properties can be sustained at an elevated temperature up to 300 °C and no discernible change in wettability was observed under highly acidic and basic conditions. After surface-coating with silicone oil for 30 mins, the composite membrane exhibits ultra-hydrophobic and superoleophilic properties with water and oil contact angles being 144.2 ± 1.2° and 0...
TL;DR: In this article, a super-hydrophobic nickel film with micro-nano structure was successfully fabricated by electrodeposition process and it exhibited pine cone-like microstructure with nano-cone arrays randomly dispersed on each micro-protrusion.
TL;DR: The wetting properties of graphene oxide are characterized by performing classical molecular dynamics simulations with relevant applications in graphene oxide-derived functional materials and offer a fundamental understanding of their wetting and flow phenomena.
Abstract: We characterize the wetting properties of graphene oxide by performing classical molecular dynamics simulations. With oxygen-containing functional groups on the basal plane, graphene becomes hydrophilic and the water contact angle decreases with their concentration, c. The concentration dependence displays a transition at c ≈ 11% as defined by the interacting range of hydrogen bonds with oxidized groups and water. Patterns of the oxidized region and the morphological corrugation of the sheet strongly influence the spreading of water droplets with their lateral spans defined by corresponding geometrical parameters and thus can be used to control their behavior on the surface. These results are discussed with respect to relevant applications in graphene oxide-derived functional materials and offer a fundamental understanding of their wetting and flow phenomena.
TL;DR: In this paper, high performance superhydrophobic PVDF flat sheet membranes for direct contact membrane distillation (DCMD) were prepared via CF 4 plasma surface modification, and the performance of the virgin and CF 4 modified membranes was examined using sodium chloride solution (4 ¼wt%) as feed in a DCMD process.
TL;DR: In this paper, the authors report the surface modification of different engineering polymers, such as polyethylene terephthalate (PET), polymethylene (PE) and polypropylene (PP), by an atmospheric pressure plasma jet (APPJ) which was operated with Ar gas using 10kV, 37 kHz, sine wave as an excitation source.
TL;DR: Faghihnejad et al. as discussed by the authors investigated the surface properties and self-adhesion mechanism of self-healing poly(butyl acrylate) (PBA) copolymers containing comonomers with 2-ureido-4[1H]-pyrimidinone quadruple hydrogen bonding groups.
Abstract: Author(s): Faghihnejad, A; Feldman, KE; Yu, J; Tirrell, MV; Israelachvili, JN; Hawker, CJ; Kramer, EJ; Zeng, H | Abstract: The surface properties and self-adhesion mechanism of self-healing poly(butyl acrylate) (PBA) copolymers containing comonomers with 2-ureido-4[1H]-pyrimidinone quadruple hydrogen bonding groups (UPy) are investigated using a surface forces apparatus (SFA) coupled with a top-view optical microscope. The surface energies of PBA-UPy4.0 and PBA-UPy7.2 (with mole percentages of UPy 4.0% and 7.2%, respectively) are estimated to be 45-56 mJ m-2 under dry condition by contact angle measurements using a three probe liquid method and also by contact and adhesion mechanics tests, as compared to the reported literature value of 31-34 mJ m-2 for PBA, an increase that is attributed to the strong UPy-UPy H-bonding interactions. The adhesion strengths of PBA-UPy polymers depend on the UPy content, contact time, temperature and humidity level. Fractured PBA-UPy films can fully recover their self-adhesion strength to 40, 81, and 100% in 10 s, 3 h, and 50 h, respectively, under almost zero external load. The fracture patterns (i.e., viscous fingers and highly "self-organized" parallel stripe patterns) have implications for fabricating patterned surfaces in materials science and nanotechnology. These results provide new insights into the fundamental understanding of adhesive mechanisms of multiple hydrogen-bonding polymers and development of novel self-healing and stimuli-responsive materials. © 2014 WILEY-VCH Verlag GmbH a Co. KGaA, Weinheim.
TL;DR: In this paper, a bio-inspired superhydrophobic coating, having a high water contact angle (>160°) and low sliding angle, was used to reduce the size of the silica nanoparticles.
TL;DR: In this article, a photo-catalysis polyvinylidene fluoride ultrafiltration membrane was successfully fabricated via phase inversion method, and the membrane matrix was supplemented with nano-ZnO of different content for membrane modification.
TL;DR: In this paper, the correlation between the contact angle, the spreading, the surface tension and the surface energy of fourteen frequently used engineering materials belonging to four different classes of materials (steel, DLC coatings, ceramics, and polymers) wetted with four different liquids: three oils (a non-polar synthetic oil of two different viscosities and a polar natural-based oil) and water.
TL;DR: In this article, a simple, one-step and environment-friendly method to construct a super-hydrophobic surface on a magnesium alloy substrate was presented, where the substrate was immersed in a solution containing ferric chloride (FeCl3·6H2O), deionized water, tetradecanoic acid (CH3(CH2)12COOH) and ethanol.
TL;DR: In this paper, the authors show through careful experiments and modeling that rare earth oxide hydrophobicity occurs due to the same hydrocarbon adsorption mechanism seen previously on noble metals.
Abstract: Vapor condensation is routinely used as an effective means of transferring heat, with dropwise condensation exhibiting a 5 − 7x heat transfer improvement compared to filmwise condensation. However, state-of-the-art techniques to promote dropwise condensation rely on functional hydrophobic coatings, which are often not robust and therefore undesirable for industrial implementation. Natural surface contamination due to hydrocarbon adsorption, particularly on noble metals, has been explored as an alternative approach to realize stable dropwise condensing surfaces. While noble metals are prohibitively expensive, the recent discovery of robust rare earth oxide (REO) hydrophobicity has generated interest for dropwise condensation applications due to material costs approaching 1% of gold; however, the underlying mechanism of REO hydrophobicity remains under debate. In this work, we show through careful experiments and modeling that REO hydrophobicity occurs due to the same hydrocarbon adsorption mechanism seen previously on noble metals. To investigate adsorption dynamics, we studied holmia and ceria REOs, along with control samples of gold and silica, via X-Ray photoelectron spectroscopy (XPS) and dynamic time-resolved contact angle measurements. The contact angle and surface carbon percent started at ≈0 on in-situ argon-plasma-cleaned samples and increased asymptotically over time after exposure to laboratory air, with the rare earth oxides displaying hydrophobic (>90°) advancing contact angle behavior at long times (>4 days). The results indicate that REOs are in fact hydrophilic when clean and become hydrophobic due to hydrocarbon adsorption. Furthermore, this study provides insight into how REOs can be used to promote stable dropwise condensation, which is important for the development of enhanced phase change surfaces.
TL;DR: It is demonstrated that the most essential freezing delay is characteristic of the superhydrophobic coating on aluminum, with the texture resistant to contact with ice and water, which can reach many hours at T = -8 °C and a few minutes at -23 °C.
Abstract: An increasing number of studies directed at supercooling water droplets on surfaces with different wettabilities have appeared in recent years. This activity has been stimulated by the recognition that water supercooling phenomena can be effectively used to develop methods for protecting outdoor equipment and infrastructure elements against icing and snow accretion. In this article, we discuss the nucleation kinetics of supercooled sessile water droplets on hydrophilic, hydrophobic, and superhydrophobic surfaces under isothermal conditions at temperatures of −8, −10, and −15 °C and a saturated water vapor atmosphere. The statistics of nucleation events for the ensembles of freezing sessile droplets is completed by the detailed analysis of the contact angle temperature dependence and freezing of individual droplets in a saturated vapor atmosphere. We have demonstrated that the most essential freezing delay is characteristic of the superhydrophobic coating on aluminum, with the texture resistant to contact ...
TL;DR: In this paper, some selected types of nanoparticles were used, which were aluminum oxide, iron oxide, and silicon oxide treated by silane, as EOR agents during different flooding scenarios and EOR experiments under surface conditions.
Abstract: Most oil reservoirs around the world are experiencing their second half of life. Hence, the necessity of appropriate enhanced oil recovery (EOR) method as a more efficient technology gets further importance. Nanotechnology is an advanced technology that has proved its potential to enhance oil recovery. In this study, some selected types of nanoparticles were used, which were aluminum oxide, iron oxide, and silicon oxide treated by silane, as EOR agents during different flooding scenarios and EOR experiments under surface conditions. For the first time, the application of propanol as a dispersing agent of nanoparticles and EOR agent in the formation was investigated by this research work. In order to examine the recovery mechanisms of nanofluids, interfacial tension (IFT), and contact angle measurements between different concentrations of nanofluids and crude oil were measured. Then, several coreflood experiments were conducted to investigate their impacts directly on recoveries. The experiment results sho...
TL;DR: It is demonstrated that stable organic monolayers can be grafted onto all these textured polymeric surfaces and provides a simple and generic method to obtain superamphiphobicity on polymers toward superoleophobicity.
Abstract: Superhydrophobic and superamphiphobic toward superoleophobic polymeric surfaces of polymethyl methacrylate (PMMA), polyether ether ketone (PEEK), and polydimethyl siloxane (PDMS) are fabricated in a two-step process: (1) plasma texturing (i.e., ion-enhanced plasma etching with simultaneous roughening), with varying plasma chemistry depending on the polymer, and subsequently (2) grafting of self-assembled perfluorododecyltrichlorosilane monolayers (SAMs). Depending on the absence or not of an etch mask (i.e., colloidal microparticle self-assembly on it), random or ordered hierarchical micro-nanotexturing can be obtained. We demonstrate that stable organic monolayers can be grafted onto all these textured polymeric surfaces. After the monolayer deposition, the initially hydrophilic polymeric surfaces become superamphiphobic with static contact angles for water and oils >153°, for hexadecane >142°, and hysteresis <10° for all surfaces. This approach thus provides a simple and generic method to obtain superam...
TL;DR: In this paper, an anti-icing hybrid material synthesized by grafting fluorinated polymer chains to silica nanoparticles via surface-initiated activators generated by electron transfer atom transfer radical polymerization (SI-AGET ATRP) was proposed.
Abstract: Ice aggregation is a global challenge, especially for cold regions. In this article, a novel anti-icing hybrid material synthesized by grafting fluorinated polymer chains to silica nanoparticles via surface-initiated activators generated by electron transfer atom transfer radical polymerization (SI-AGET ATRP) was proposed. It showed such properties as controllable molecular design, wonderful thermal stability and high superhydrophobicity. Most importantly, it exhibited excellent anti-icing properties by using coatings with different wettabilities that varied from hydrophilic to superhydrophobic. Its large static water contact angle (WCA, 170.3°) and small contact angle hysteresis (CAH, <3°) can promote the removal of droplets efficiently. A new characterization method, DSC, was used to test the crystallization point of water and its results demonstrated that the crystallization point can be depressed to a large extent (6.82 °C). The low temperature WCA showed that it can postpone the freezing time from 196 s to 10 054 s which indicates the surface can prevent ice formation well, especially with the help of external forces. The mechanisms were discussed based on physicochemical properties, heterogeneous nucleation theory and heat transfer theory. According to the present study, it is reasonable to predict that the organic–inorganic hybrid superhydrophobic coating will be a prospective anti-icing candidate for various applications such as wind turbine blades, power lines and aircraft.
TL;DR: This model is mostly influential during the spreading phase for the cases of low The authors number impacts (They<˜80) since for high impact velocities, inertia dominates significantly over capillary forces in the initial phase of spreading.