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Showing papers on "Sessile drop technique published in 2006"


Journal ArticleDOI
TL;DR: In this paper, the influence of Cu-coating on the spreading kinetics and equilibrium contact angles of aluminum on ceramics using a sessile drop technique was investigated.
Abstract: The purpose of this study was to investigate the influence of Cu-coating on the spreading kinetics and equilibrium contact angles of aluminum on ceramics using a sessile drop technique. Al2O3 and SiC plates were coated by electroless plating. The copper film overcomes the low wetting of the uncoated samples by dissolution in the drop at 800 °C in argon, showing an intrinsically favorable effect on the adhesion energy. Just after 2 min, the contact angle decreased to 12.6° and 26°for Al/Cu–Al2O3 and Al/Cu–SiC, respectively. However, a de-wetting behavior was observed, reaching equilibrium contact angles of 58.3° and 45.5° for the couples. The dissolution reaction rate at the triple junction was so high that the spreading process was controlled by local diffusion rather than chemical reaction kinetics.

967 citations


Journal ArticleDOI
25 Mar 2006-Langmuir
TL;DR: This work investigated the formation of a droplet from a single pore in a glass chip, which is a model system for droplet formation in membrane emulsification, and found that all resulting droplet sizes could be correlated quantitatively with the capillary number and the fluxes in the system.
Abstract: We investigated the formation of a droplet from a single pore in a glass chip, which is a model system for droplet formation in membrane emulsification. Droplet formation was simulated with the lattice Boltzmann method, a method suitable for modeling on the mesoscale. We validated the lattice Boltzmann code with several benchmarks such as the flow profile in a rectangular channel, droplet deformation between two shearing plates, and a sessile drop on a plate with different wetting conditions. In all cases, the modeling results were in good agreement with the benchmark. A comparison of experimental droplet formation in a microchannel glass chip showed good quantitative agreement with the modeling results. With this code, droplet formation simulations with various interfacial tensions and various flow rates were performed. All resulting droplet sizes could be correlated quantitatively with the capillary number and the fluxes in the system.

326 citations


Journal ArticleDOI
TL;DR: In this paper, a concept of reactive wetting has been formulated which suggests a direct relation between wetting and physicochemical properties of the interfacial reaction products of the CuAg-Ti/alumina system, which is more complex but important in brazing.

151 citations


Journal ArticleDOI
TL;DR: In this article, a sessile drop of individually suspended carbon nanotubes (SWNTs) in an aqueous solution of F68 Pluronic was measured at four different angles and averaged.
Abstract: Single-walled carbon nanotubes (SWNTs) are currently the focus of extensive interdisciplinary studies because of their unique physical and chemical properties and potential electronic applications, for example, in making sensors and fieldemission devices. Processing of SWNT-based materials into engineered macroscopic materials is still in its infancy; the most successful methods so far have been based on adapting techniques that had been developed in other areas of material science such as colloids and polymers. Recent successes include preparing fibers and ribbons of SWNTs; films of pure SWNTs, polymers doped with SWNTs, and growth in situ of SWNT arrays. Evaporation of drops on substrates has been used for patterned deposition of solutes onto non-porous substrates, such as in DNA microarrays, nanolithography, protein crystallization, and stretching DNA for hybridization studies. Shimoda et al. prepared continuous selfassembled films of SWNT bundles on glass near a receding contact line by solvent evaporation. The moving contact line of a drying drop could be similarly used to form aligned patterns of SWNTs on substrates for making films or for nanofabrication. Drops of a solution on a substrate follow one of two drying mechanisms: either the drop maintains a constant contact angle by de-pinning the contact line (e.g., water on non-wetting substrates), or the contact line gets pinned and the drop maintains a fixed contact area (e.g., colloidal dispersions). Deegan and co-workers have studied the drying of drops of colloidal dispersions and found that the particles deposit in a ring at the periphery of the drop due to capillary flow in which the pinned contact line causes the solvent to flow towards the edge. Recent investigations have also shown the formation of a skin or crust at the free surface of drops of polymers and colloidal suspensions. Pauchard and Allain found that the crust may collapse and evolve into different shapes as the surface area remains constant while the drop volume decreases due to solvent evaporation. “Crusting” on the surface of spin-cast films is a well-known phenomenon. De Gennes suggested a transport model for crust formation in spin-cast films. Because the glass-transition or gelation temperature of a pure polymer/colloid is higher than that in solution, at any temperature below the glass transition there is a critical particle concentration at which the system transitions from fluid to glassy or gel-like. Evaporation of solvent from the free surface leads to a local increase in concentration of the polymer/suspension at the free surface, and a very thin glassy or gelled crust is formed at the free surface. Here, we investigated drying of a sessile drop of individually suspended SWNTs in an aqueous solution of F68 Pluronic. We found that, instead of assembling on the substrate, the SWNTs selfassemble into a crust at the free surface. This entangled meshlike crust was characterized by various microscopy techniques. The “crusting” phenomenon could be used as a potential route for making thin coatings and films of SWNTs. Video microscopy showed that the initial drying progressed by de-pinning of the contact line, i.e., the radius of the base decreased with time. Figure 1a shows the drop radius (normalized by the initial radius) as a function of time. The diameter of each drop was measured at four different angles and then averaged. After about 360 s the drop attained a fixed base radius and a foot started appearing. Drops of pure water on the same substrate dried by maintaining a fixed base radius, in agreement with the findings by Birdi et al. Assuming quasistationary conditions, if diffusion of water in air is rate controlling, then in a sessile drop receding with a constant contact angle the square of the base radius is linear with time. While the drop radius shrunk, the contact angle between the drop and the glass substrate was about 10–15 °C (inferred by video microscopy). Up to t ∼ 210 s, we find that the assumption that diffusion is rate controlling is fairly accurate (Fig. 1b). We recorded the variation of weight of the drop with time (Fig. 1c) and found that the initial evaporation rate J0 was J0 ∼ 2 × 10 cm s. As the drying progressed further, the drop attained a constant base radius at t∼ 360 s, and a surface undulation appeared at the top of the drop. A thin crust appeared at the free surface, with a convective flow toward the foot underneath. The formation of the crust slowed down the solvent loss from the initial evaporation rate J0 (Fig. 1c) by reducing the diffusion of water from the core of the drop to the free surface. Loss of the solvent decreased the volume enclosed by the thin crust, and the crust thus inverted, forming an undulation similar to a collapsing dome. The drying process is summarized schematically in Figure 2. C O M M U N IC A IO N S

128 citations


Journal ArticleDOI
H. S. Xue, J. R. Fan, Y. C. Hu, R. H. Hong, Kefa Cen 
TL;DR: In this article, an aqueous solution of carbon nanotubes, treated by a concentrated nitric/sulfuric acid mixture to disentangle the nanotube, was utilized as the working medium in a two-phase closed thermosyphon to investigate its performance.
Abstract: An aqueous solution of carbon nanotubes, treated by a concentrated nitric/sulfuric acid mixture to disentangle the nanotubes, was utilized as the working medium in a two-phase closed thermosyphon to investigate its performance. In comparison with the thermosyphon filled with a distilled water medium, the one filled with carbon nanotube suspension has a high evaporation section wall temperature, incipience temperature, and excursion, as well as thermal resistance. The carbon nantotubes’ nanofluid deteriorates the performance of the gravity-assisted heat pipe. Measurements employing the maximum bubble pressure method demonstrate that suspending carbon nanotubes in bulk water gives rise to increased surface tension. In addition, the contact angle of suspension obtained with the sessile drop method on a copper plate is much smaller than that of water. Alterations of solid-liquid-vapor interfacial properties, arising from the addition of carbon nanotubes, change the boiling mechanism and thus deteriorate the b...

118 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of the hydrophobicity of two bacterial strains ( Pseudomonas stutzeri PS, and Staphylococcus epidermidis SE) and substrata surfaces on the adhesion mechanism was investigated.

116 citations


Journal ArticleDOI
TL;DR: Substrates of aluminum (Al) deposited by physical vapor deposition onto Si substrates and then chemically reacted with perfluorodecylphosphonic acid (PFDP alkylphosphonate, DPAlSi, and ODPAlSi) were studied to characterize their surface chemical composition, roughness, and micro-/nanotribological properties.
Abstract: Substrates of aluminum (Al) deposited by physical vapor deposition onto Si substrates and then chemically reacted with perfluorodecylphosphonic acid (PFDP∕Al∕Si), decylphosphonic acid (DP∕Al∕Si), and octadecylphosphonic acid (ODP∕Al∕Si) were studied by x-ray photoelectron spectroscopy (XPS), contact angle measurements, atomic force microscopy (AFM), and friction force microscopy, a derivative of AFM, to characterize their surface chemical composition, roughness, and micro-/nanotribological properties. XPS analysis confirmed the presence of perfluorinated and nonperfluorinated alkylphosphonate molecules on the PFDP∕Al∕Si, DP∕Al∕Si, and ODP∕Al∕Si. The sessile drop static contact angle of pure water on PFDP∕Al∕Si was typically more than 130° and on DP∕Al∕Si and ODP∕Al∕Si typically more than 125° indicating that all phosphonic acid reacted Al∕Si samples were very hydrophobic. The surface roughness for PFDP∕Al∕Si, DP∕Al∕Si, ODP∕Al∕Si, and bare Al∕Si was approximately 35nm as determined by AFM. The surface ener...

107 citations


Journal ArticleDOI
TL;DR: The resonant modes of sessile water drops on a hydrophobic substrate subjected to a small-amplitude lateral vibration are investigated using computational fluid dynamic (CFD) modeling and a comparison between the frequency-dependent motion of these drops and the variation of contact angles on both sides is made.
Abstract: The resonant modes of sessile water drops on a hydrophobic substrate subjected to a small-amplitude lateral vibration are investigated using computational fluid dynamic (CFD) modeling. As the substrate is vibrated laterally, its momentum diffuses within the Stokes layer of the drop. Above the Stokes layer, the competition between the inertial and Laplace forces causes the formation of capillary waves on the surface of the drop. In the first part of this paper, the resonant states of water drops are illustrated by investigating the velocity profile and the hydrostatic force using a 3d simulation of the Navier-Stokes equation. The simulation also allows an estimation of the contact angle variation on both sides of the drop. In the second part of the paper, we investigate the effect of vibration on a water drop in contact with a vertical plate. Here, as the plate vibrates parallel to gravity, the contact line oscillates. Each oscillation is, however, rectified by hysteresis, thus inducing a ratcheting motion to the water droplet vertically downward. Maximum rectification occurs at the resonant states of the drop. A comparison between the frequency-dependent motion of these drops and the variation of contact angles on their both sides is made. The paper ends with a discussion on the movements of the drops on a horizontal hydrophobic surface subjected to an asymmetric vibration.

103 citations


Journal ArticleDOI
TL;DR: The results demonstrate that electrowetting can greatly reduce the hydrophobicity of the aligned CNTs and may be invoked to controllably reduce the interfacial tension between carbon nanotubes (CNTs) and polymer precursors when infiltrating the monomers into the prealigned nanotube films.
Abstract: Electrowetting is one approach to reducing the interfacial tension between a solid and a liquid. In this method, an electrical potential is applied across the solid/liquid interface which modifies the wetting properties of the liquid on the solid without changing the composition of the solid and liquid phases. Electrowetting of aligned carbon nanotube (CNT) films is investigated by the sessile drop method by dispensing deionized (DI) water or 0.03 M NaCl droplets (contacted by Au wire) onto aligned CNT films assembled on a copper substrate. The results demonstrate that electrowetting can greatly reduce the hydrophobicity of the aligned CNTs; the contact angle saturation for DI water and 0.03 M NaCl droplets occurs at 98 and 50°, respectively. The combined effects of the geometrical roughness and the electrical potential on the contact angle are briefly discussed and modeled. Such a strategy may be invoked to controllably reduce the interfacial tension between carbon nanotubes (CNTs) and polymer precursors...

91 citations


Journal ArticleDOI
TL;DR: ODP/Al and OP/Al were studied by friction force microscopy, a derivative of AFM, to better understand their micro-/nano-tribological properties and gave the lowest coefficient of friction values while bare Al gave the highest.
Abstract: The surface properties of aluminum, such as chemical composition, roughness, friction, adhesion, and wear, can play an important role in the performance of micro-/nano-electromechanical systems, e.g., digital micromirror devices. Aluminum substrates chemically reacted with octadecylphosphonic acid (ODP/Al), decylphosphonic acid (DP/Al), and octylphosphonic acid (OP/Al) have been investigated and characterized by X-ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM). XPS analysis confirmed the presence of alkylphosphonate molecules on ODP/Al, DP/Al, and OP/Al. No phosphonates were found on bare Al as a control. The sessile drop static contact angle of pure water on ODP/Al and DP/Al was typically more than 115° and on OP/Al typically less than 105° indicating that all phosphonic acid reacted Al samples were highly hydrophobic. The root-mean-square surface roughness for ODP/Al, DP/Al, OP/Al, and bare Al was less than 15 nm as determined by AFM. The surface ener...

90 citations


Journal ArticleDOI
TL;DR: In this paper, the geometrical shape, wetting length, and contact angle of a microdroplet on a fiber were derived based on the free energy variation of the droplet/fiber system.
Abstract: This paper is concerned with the geometrical shape, wetting length, and contact angle of a microdroplet on a fiber by using the method free energy variation. The governing equation and relevant boundary conditions of the microdroplet were re-derived based on the free energy variation of the droplet/fiber system. The geometrical shape of the droplet was determined as the combination of Legendre's elliptical functions of the first and second kinds, corresponding to the previous results in literature [6]. For contact angle θ >15°, a novel efficient semi-analytic approach was proposed to extract the contact angle from experimental data. The given approach can be used as theoretical basis of determining surface tension of fluids based on a sessile drop on a fiber.

Journal ArticleDOI
TL;DR: The relationship among contact angles, surface tension, and surface roughness is reviewed in this paper, and various numerical formulae related to contact angles are used to predict the surface tension and wetting behavior of polymer surfaces.
Abstract: The relationships among contact angles, surface tensions, and surface roughness are reviewed. The various numerical formulae related to contact angles were used to predict the surface tension and wetting behavior of polymer surfaces. The apparent contact angle of a droplet deposited on a textured surface is presented, and the characteristics required for a superhydrophobic surface are described. This study also presents the effect of the sliding angles of liquid droplets on smooth and rough surfaces. The contact angle hysteresis was found to be very important in understanding the drop motion on a surface. Contact angle hystereses increased on a Wenzel-type surface, while a Cassie-Baxter type surface reduced the hystereses for the same surface roughness and surface tensions.

Journal ArticleDOI
TL;DR: In this article, the isothermal dissolutive wetting behavior of various Bi-Sn alloys on pure Bi substrates was studied using the sessile drop technique, and the contact line mobility relationship, based on apparent dynamic contact angle, showed certain similarities to a universal correlation for partially wetting inert systems.

Journal ArticleDOI
TL;DR: In this paper, a polypropylene hollow fiber microporous membrane (PPHFMM) was surface modified by the immobilization of poly(N -vinyl-2-pyrrolidone) (PVP) through air plasma treatment.

Journal ArticleDOI
TL;DR: Anisotropic wetting behavior was established for a range of crystalline systems: paracetamol polymorphs, aspirin, and ibuprofen racemates, and the hydrophilicity/hydrophobicity of facets reflects the presence of functional groups at surfaces to form hydrogen bonds with external molecules.
Abstract: The purpose of this study was to establish the link between the wetting behavior of crystalline pharmaceutical solids and the localized surface chemistry. A range of conventional wetting techniques were evaluated and compared with a novel experimental approach: sessile drop contact angle measurements on the individual facets of macroscopic (>1 cm) single crystals. Conventional measurement techniques for determining surface energetics such as capillary rise and sessile drops on powder compacts were found not to provide reliable results. When the macroscopic crystal approach was used, major differences for advancing contact angles, theta(a), of water were observed-as low as 16 degrees on facet (001) and as high as 68 degrees on facet (010) of form I paracetamol. theta(a) trends were in excellent agreement with X-ray photoelectron spectroscopy surface composition and known crystallographic structures, suggesting a direct relationship to the local surface chemistry. Inverse gas chromatography (IGC) was further used to probe the surface properties of milled and unmilled samples, as a function of particle size. IGC experiments confirmed that milling exposes the weakest attachment energy facet, with increasing dominance as particle size is reduced. The weakest attachment energy facet was also found to exhibit the highest theta(a) for water and to be the most hydrophobic facet. This anisotropic wetting behavior was established for a range of crystalline systems: paracetamol polymorphs, aspirin, and ibuprofen racemates. theta(a) was found to be very sensitive to the local surface chemistry. It is proposed that the hydrophilicity/hydrophobicity of facets reflects the presence of functional groups at surfaces to form hydrogen bonds with external molecules.

Journal ArticleDOI
TL;DR: In this paper, the surface tension of molten silicon was measured using both the oscillating drop method and an improved sessile drop method, and the result was expressed by the following equation: γ = −733 −−−0.062(T −−1687) where T is the temperature.

Journal ArticleDOI
TL;DR: In this paper, the effect of flux on the wetting characteristics of four lead-free solders, Sn-3.5Ag, sn-0.7Cu and Sn-1.8Cu, on copper substrates at 240, 260, and 280°C were studied.
Abstract: The effect of flux on the wetting characteristics of four lead-free solders, Sn-3.5Ag, Sn-0.7Cu, Sn-3.5Ag-4.8Bi, and Sn-3.8Ag-0.7Cu (wt.%), on copper substrates have been studied at 240, 260, and 280°C. The fluxes investigated were rosin (R), mildly activated rosin (RMA), and activated rosin (RA). The wetting tests were conducted using the sessile-drop method. Results showed that fluxes significantly affect the wetting properties of the solders. Contact angles ranging from 10° to 30° for RMA, 20° to 30° for RA, and 35° to 60° for R were obtained. The effect of temperature on contact angle depended on the type of flux used. The contact angle decreased with increasing temperature; however, in some cases the contact angle was independent of temperature. The Sn-3.5Ag-4.8Bi exhibited the lowest contact angles indicating improved wettability with addition of bismuth. The microstructure of the solder/copper interface was analyzed by scanning electron microscopy.

Journal ArticleDOI
TL;DR: In this article, the interfacial tension between liquid iron and slag was examined for CaO-SiO2 binary and CaO−SiO 2-Al2O3 ternary slag systems.
Abstract: Interfacial tensions between liquid iron and slag were examined for CaO–SiO2 binary and CaO–SiO2–Al2O3 ternary slag systems. The influences of FeO, MgO, B2O3, TiO2, BaO and ZrO2 in slag on the interfacial tension were also investigated by varying these oxides from 1–30 wt% in the CaO–SiO2 binary or CaO–SiO2–Al2O3 ternary slag systems.The interfacial tensions were determined by the sessile drop technique under argon atmosphere at 1 853 K. An X-Ray radiographic technique was employed to image the profile of molten iron drop in a slag bath and the interfacial tensions between slag and iron were obtained from the drop shape analysis.In examining the effect of slag composition on the interfacial tension, the oxygen in liquid iron and its impact on the interfacial tension was taken into consideration. The interfacial tension was found slightly increased with increasing CaO/SiO2 ratio in CaO–SiO2 slag, and with increasing MgO content in the slag. A decrease of interfacial tension was found with increasing FeO in slag. Only minor changes in the interfacial tension were observed with varying the slag composition in the CaO–SiO2–Al2O3 ternary slag system and the influences of B2O3, TiO2, BaO, and ZrO2 in slag on the interfacial tension were found insignificant.

Journal ArticleDOI
TL;DR: In this paper, surface modification of polyimide films such as Kapton E(N) and Upilex S by air plasmas was investigated for enhanced adhesive strength with sputtered coppers.
Abstract: Surface modification of polyimide films such as Kapton E(N) and Upilex S by air plasmas were investigated for enhanced adhesive strength with sputtered coppers. Peel tests demonstrate this improvement, with the peel strengths of 0.7 g/mm and 1.2 g/mm for unmodified Kapton E(N) and Upilex S and 99.3 g/mm and 91.5 g/mm for air plasma-modified Kapton E(N) and Upilex S at certain plasma conditions. This study reported that the enhanced adhesive strengths of polyimide films with sputtered coppers by air plasmas were strongly affected by the surface characteristics such as surface morphology and surface energy of polyimide films. Atomic force microscopy (AFM) and sessile drop method indicated the surface roughness and the surface energy of polyimide films were much increased by air plasmas that result in much increased peel strengths of polyimide films with sputtered coppers. Electron spectroscopy for chemical analysis (ESCA) observed the increased surface energy on polyimide films by air plasmas were due to the increased surface composition of O and the increased chemical bond of C–O.

Journal ArticleDOI
TL;DR: In this article, a theoretical model based on forces developed at the contact area between a liquid drop and hydrophobic smooth or nanoroughened surfaces was developed and compared with the existing models, which are based on force at the periphery between the drop and the solid surface.
Abstract: The effects of nanoroughness and chemical composition on the contact and sliding angles on hydrophobic surfaces were studied theoretically and experimentally. A theoretical model based on forces developed at the contact area between a liquid drop and hydrophobic smooth or nanoroughened surface was developed and compared with the existing models, which are based on forces developed at the periphery between the drop and the solid surface. The contact area based model gives rise to an interfacial adhesion strength parameter that better describes the drop-sliding phenomenon. Consequently, relationships were derived describing the dependence between the interfacial adhesion strength of the liquid drop to the surface of a given composition, the mass of the drop, the measured contact angles and the sliding angle. For a given surface chemistry, the sliding angle on a nanometric roughened surface can be predicted based on measurements of contact angles and the sliding angle on the respective smooth surface. Variou...

Journal ArticleDOI
TL;DR: In this article, the surface tension in metallic alloy systems is modelled by applying a direct Gibbs energy minimisation technique to the surface monolayer model, and the model results are compared with previously published experimental values for the Bi-Sn system as well as surface tension values determined by the sessile drop method for the ternary Ag-Au-Cu system.
Abstract: The surface tension in metallic alloy systems is modelled by applying a direct Gibbs energy minimisation technique to the surface monolayer model. The model results are compared with previously published experimental values for the Bi–Sn system as well as surface tension values determined by the authors using the sessile drop method for the ternary Ag–Au–Cu system.

Journal ArticleDOI
TL;DR: In this paper, the hydrophilicity of RF sputtered thin films of pure TiO 2 and doped with 0.3% Ce, 0.4% Nb, and 0.5% N N (atomic percents) was investigated by measurements of the contact angle between water and film surface.

Journal ArticleDOI
TL;DR: In this article, an atomic force microscopy (AFM) based technique was developed to measure the wetting properties of probe tips and the water contact angle was determined from the meniscus force.
Abstract: An atomic force microscopy (AFM) based technique was developed to measure the wetting properties of probe tips. By advancing and receding the AFM tip across the water surface, the meniscus force between the tip and the liquid was measured at the tip?water separation. The water contact angle was determined from the meniscus force. The obtained contact angle results were compared with that by the sessile drop method. It was found that the AFM based technique provided higher contact angle values than the sessile drop method. The mechanisms responsible for the difference are discussed.

Journal ArticleDOI
TL;DR: In this article, the wettability of polycrystalline rutile TiO 2 by molten aluminum in purified Ar, Ar-3% H 2 and vacuum over a wide temperature range was investigated.

Journal ArticleDOI
TL;DR: In this paper, microscopic drops of liquids were deposited onto atomic force microscope cantilevers to monitor the evaporation kinetics of drops from solid surfaces, and to investigate the interaction between liquids and solids.
Abstract: To monitor the evaporation kinetics of drops from solid surfaces, and to investigate the interaction between liquids and solids, microscopic drops of liquids were deposited onto atomic force microscope cantilevers. Due to the surface tension of the liquid, the Laplace pressure inside the drop, and the change of the interfacial stress at the solid–liquid boundary, the cantilever bends and is deflected by typically a few hundred nanometers. We used liquids with different vapour pressures and surface tensions, in order to vary the evaporation time and also the magnitude of the surface forces exerted by the drops. For fast evaporating drops the cantilever bending along the longitudinal axis was measured versus time. In the case of non-evaporating drops the overall bending was recorded with optical methods. We developed a FEM model for cantilever bending as an improvement to a previously presented analytical model. FEM simulations are confirmed by experimental results.

Journal ArticleDOI
TL;DR: The results are compared with previously published results when Alkenyl Succinic Anhydride (ASA) was brought into contact with SiO2 under water and preferential surface vapour pressure and liquid spreading of the one liquid over the solids in the absence and presence of a saturated liquid vapour were evaluated as sources of errors.

Journal ArticleDOI
TL;DR: In this paper, a PFTS-modified Cu surface (PFTS/Cu) was characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR), which confirmed the presence of perfluorinated alkyl chains.
Abstract: Polished copper (Cu) surfaces modified with 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFTS) have been shown to be very hydrophobic and stable. Mechanically polished, oxidized, and PFTS-reacted Cu surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy, which confirmed the presence of perfluorinated alkyl chains. For a PFTS-modified Cu surface (PFTS/Cu), the sessile drop static contact angle of pure water at ambient temperature and high relative humidity (RH) was measured to be more than 125° and the Zisman critical surface energy to be typically less than 16 mN/m. Ellipsometry showed the thickness of the PFTS/Cu film to be typically less than 25 nm. Stability tests indicated that the PFTS/Cu film could survive in pure boiling water for one hour, boiling nitric acid (pH 1.5 or 1.8) for 30 min, sodium hydroxide solution (pH 12, 70 °C) for 30 min, and autoclave conditions (steam at 134 °C and 3 atm) for 15 min. The more commonly used self-assembled monolayer (SAM) modifications of Cu surfaces, e.g. thiol compounds, are significantly less stable than PFTS/Cu. The extremely hydrophobic and stable PFTS/Cu could be a very good candidate for corrosion inhibition and/or heat exchangers exploiting condensation. Copyright © 2005 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, the role of carbonaceous material in the dissolution of carbon from the refractory composite was investigated and the results were supplemented with wettability measurements and microscopic investigations on the interfacial region.
Abstract: Due to their excellent thermal shock and wear resistance at high temperatures, alumina-carbon based refractories are used extensively in the steel industry. A clear understanding of factors affecting the dissolution of carbon from refractories is of crucial importance, as carbon depletion from the refractory can significantly deteriorate refractory performance and metal quality. Atomistic simulations on the alumina-graphite/liquid iron system have shown that nonwetting between alumina and liquid iron is an important factor inhibiting the penetration of liquid metal in the refractory matrix and limiting carbon dissolution. This study investigates the role played by the carbonaceous material in the dissolution of carbon from the refractory composite. Two carbonaceous materials, namely, petroleum coke and natural graphite, respectively, containing 0.35 and 5.26 pct ash, were used in this study. Substrates were prepared from mixtures of alumina and carbon over a wide concentration range. Using a sessile drop arrangement, carbon pickup by liquid iron from alumina-carbon mixtures was measured at 1550 °C and was compared with the carbon pickup from alumina-synthetic graphite mixtures. These studies were supplemented with wettability measurements and microscopic investigations on the interfacial region. For high alumina concentrations (>40 wt pct), carbon dissolution from refractory mixtures was found to be negligible for all carbonaceous materials under investigation. Significant differences however were observed at lower alumina concentrations. Carbon dissolution from alumina-petroleum coke mixtures was much lower than the corresponding dissolution from alumina synthetic graphite-mixtures and was attributed to poor wettability of petroleum coke with liquid iron, its structural disorder, and the presence of sulfur. Very high levels of carbon dissolution, however, were observed from alumina-natural graphite mixtures, with carbon pickup by liquid iron from mixtures with up to 30 wt pct alumina reaching saturation. A sharp reduction to near zero levels was observed in the 30 to 40 wt pct alumina range. Along with implications for commercial refractory applications, these results are discussed in terms of material characteristics, interactions between ash impurities and alumina, and formation of complexes in the interfacial region.

Journal ArticleDOI
TL;DR: The wetting of MgO by molten magnesium was measured between 973 and 1273 K using an improved sessile drop method as mentioned in this paper, where molten magnesium is set around the sample droplet to prevent oxidation of the magnesium droplet.
Abstract: The wetting of MgO by molten magnesium was measured between 973 and 1273 K using an improved sessile drop method. In this method, molten magnesium was set around the sample droplet to prevent oxidation of the magnesium droplet. A significant volume loss of the droplet was observed over 1073 K due to the high vapor pressure, and the contact angle was underwent an unusual change over 1173 K. The contact angle first decreased and then increased. This phenomenon occurred due to the pinning of the three-phase line at deep ditch. This change in the contact angle is an apparent change in contact angle. The intrinsic contact angle should be decided using the initial value or the maximum value just before the disappearance of the droplet. For any high vapor pressure system, such a change in contact angle can be observed at high temperatures.

Journal ArticleDOI
TL;DR: In this paper, the wetting properties of thermally bonded polyester nonwoven fabrics with different basis weights were studied, and it was shown that the pore structure played a dominant role in the surface porosity of these fabrics.
Abstract: The wetting properties of thermally bonded polyester nonwoven fabrics with different basis weights were studied. These nonwovens had the same composition: 85% poly(ethylene terephthalate) and 15% poly(butylene terephthalate) fibers. Two techniques, the 3S wicking test and sessile drop method, yielded similar water contact angles for all the nonwovens, but these results differed from the values obtained with the single fibers. In the nonwoven fabrics, the pore structure played a dominant role in the wetting properties: the existence of large pores in the thinner nonwovens reduced the dimensions of the liquid–solid interfacial perimeter. Compared with the water contact angle of the constituent single fibers, the contact angle of the fabrics was increased. A crenellated surface model was created to quantify the influence of pores on the wettability of nonwovens. It was possible to deduce the surface porosity of the fabric with this model, but only in the case of contact with nonwetting liquids such as water: this surface porosity corresponded only to the outermost layers of the fabric structure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 387–394, 2006