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Showing papers on "Surface tension published in 1978"


Journal ArticleDOI
TL;DR: In this article, the Casimir van der Waals forces between dielectrics with plane, parallel surfaces for arbitrary temperature were investigated using the methods of source theory, and the general results of Lifshitz are confirmed, and are shown to imply the correct forces on metal surfaces.

363 citations


Journal ArticleDOI
TL;DR: In this paper, a mechanism for growth instability is discussed, which is based on surface tension gradients due to the concentration gradient of a surface active impurity in front of a growing crystal.

278 citations


Journal ArticleDOI
TL;DR: In this article, the effects of alcohol and other system parameters on surfactant chemical potential and hence on interfacial tension are noted, and the conditions necessary for optimum low tension and phase behavior at high surfactants concentrations are identical to those required for a tension minimum at low surfactor concentrations, where solibilization effects may not be visible.
Abstract: Perturbations of system parameters are shown to affect the surfactant partitioning between oil and water through changes in the relative standard chemical potentials of the surfactant in the 2 phases. For the systems investigated, low interfacial tensions are associated with near-unity values of the partition coefficient. The conditions necessary for optimum low tension and phase behavior at high surfactant concentrations are identical to those required for a tension minimum at low surfactant concentrations, where solibilization effects may not be visible. The effects of alcohol and other system parameters on surfactant chemical potential and hence on interfacial tension are noted. (18 refs.)

161 citations


Journal ArticleDOI
TL;DR: In this paper, spontaneous movements induced by the direct transformation of chemical into mechanical energy at an oil water interface are studied and correlations between the observed variations of the interfacial tension, the pH and the potential difference between both phases lead to the assumption that a chemical oscillating reaction is the determining process.

155 citations


Journal ArticleDOI
Eva Tornberg1
01 May 1978
TL;DR: In this article, a new procedure for the application of the drop volume technique to measurements of the rate of adsorption of proteins at interfaces has been developed, and the mode of adaption of the proteins lysozyme, β-lactoglobulin and bovine serum albumin (BSA) at the air-water interface has been measured with the Drop volume method and has been compared to measurements with the Wilhelmy plate technique.
Abstract: A new procedure for the application of the drop volume technique to measurements of the rate of adsorption of proteins at interfaces has been developed. The mode of adsorption of the proteins lysozyme, β-lactoglobulin and bovine serum albumin (BSA) at the air-water interface has been measured with the drop volume method and has been compared to measurements with the Wilhelmy plate technique. Due to surface enlargement of the drop throughout the process of the surface tension decay, slower kinetics of the adsorption process is obtained by the drop volume method compared to the Wilhelmy plate technique, and the proteins investigated were differently sensitive to this surface expansion. The adsorption process of the proteins has been evaluated in terms of different rate-determining processes. Different intermediate states between the native and the denatured forms have been observed.

137 citations


Journal ArticleDOI
TL;DR: In this paper, the role of the combination of a surfactant and a cosurfactant is seen in their leading to a decrease in the interfacial tension to potentially negative values.
Abstract: Microemulsions can be regarded as thermodynamically stable dispersions of droplets of one phase in another phase. There are continuous transitions to swollen micelles, when the droplets become extremely small, and to coarse emulsions when the droplets are large. The mechanism leading to the formation of microemulsions is the tendency to extend the interfacial area until the concentrations of surfactants are sufficiently low that non-negative interfacial tension is achieved. The role of the combination of a surfactant and a cosurfactant is seen in their leading to a decrease in the interfacial tension to potentially negative values. An expression is given for the Gibbs energy of the whole system, for the special case of an ionized surfactant and a non-ionized cosurfactant. The minimization of this Gibbs energy leads to the stability conditions for the microemulsion. The factors which promote O/W and W/O emulsions, respectively, are briefly discussed. The electrical contribution to the interfacial tension depends on the particle size. This leads to a narrow size distribution. It is finally pointed out that, in principle, fine dispersions of solids in a liquid may be thermodynamically stable in the presence of large amounts of easily adsorbed compounds.

129 citations


Journal ArticleDOI
TL;DR: In this paper, a simple phenomenological theory is outlined, based on the hypothesis that this excess order resides solely in the degree of alignment of the molecules, the conventional nematic order parameter being larger near the surface than in the bulk.
Abstract: The surface tension γ has been measured for two cyanobiphenyls (5CB and 8CB) at temperatures near the nematic-isotropic transition temperature T c, using the Wilhelmy plate method. Reproducible results were obtained, but only by the exercise of considerable patience: for reasons that are discussed at the end of the paper, it took up to four days for equilibrium to be re-established whenever the temperature was changed. The results suggest that in both materials the equilibrium value of γ increases discontinuously (by approximately 0·3 dyne cm−1) on heating through T c, and that (dγ/dT) is positive both for the isotropic phase just above T c and for the nematic phase just below it. A positive value of (dγ/dT) implies excess order in the surface layers. A simple phenomenological theory is outlined, based on the hypothesis that this excess order resides solely in the degree of alignment of the molecules, the conventional nematic order parameter being larger near the surface than in the bulk. The pre...

126 citations


Journal ArticleDOI
TL;DR: A novel means of generating and detecting surface waves at liquid-gas interfaces has been successfully developed using Electrocapillarity through specular reflection of a laser beam from the fluid surface to a position sensitive photodiode.
Abstract: A novel means of generating and detecting surface waves at liquid–gas interfaces has been successfully developed. Electrocapillarity is used to generate the waves which are detected via specular reflection of a laser beam from the fluid surface to a position sensitive photodiode. Such a scheme is compact, sensitive, and does not mechanically touch the fluid surface. A preliminary study of highly damped waves on the magnetically oriented liquid crystal MBBA is reported.

90 citations


Journal ArticleDOI
01 Dec 1978
TL;DR: In this paper, a strong synergistic lowering of the surface tension was found at concentrations below the point at which precipitation, micellization, or complex formation in solution occurred, which could be fully explained by Gibbs' adsorption equation.
Abstract: Equilibrium surface tension measurements have been carried out on mixed solutions of poly l -lysine hydrobromide and sodium dodecyl sulfate. A strong synergistic lowering of the surface tension was found at concentrations below the point at which precipitation, micellization, or complex formation in solution occurred. Several aspects of the surface tension behavior in this low concentration region could be fully explained by Gibbs' adsorption equation. For example, above a certain, small, polylysine concentration, the equilibrium surface tension was virtually only determined by the dodecyl sulfate concentration and was practically independent of variations in the polylysine concentration. On the other hand, the rate of equilibration was mainly determined by the polylysine concentration, except at very low dodecyl sulfate concentrations. From the experimental results it could be deduced that the adsorbed polylysine molecules in the mixture were probably in the β (“near extended”) conformation with dodecyl sulfate having replaced nearly all bromide as counterions in the electroneutral Gibbsian surface. Some implications of similar synergistic interactions in biological systems are discussed.

89 citations


Journal ArticleDOI
01 Nov 1978
TL;DR: The surface tension of aqueous solutions of hydroxypropyl cellulose has been measured using the pendant drop method as discussed by the authors, and the results showed that the surface tension was 42.4 ± 1.0 mN/m for all concentrations ranging from 2 ppm to 32% by weight.
Abstract: The surface tension of aqueous solutions of hydroxypropyl cellulose has been measured using the pendant drop method. Hydroxypropyl cellulose samples with molecular weights greater than 100,000 gave a steady-state surface tension of 42.4 ± 1.0 mN/m for all concentrations ranging from 2 ppm to 32% by weight. Samples of lower MW hydroxypropyl cellulose also gave this surface tension at all but the lowest (

82 citations


Journal ArticleDOI
TL;DR: In this paper, the interfacial tension α between water and hexane solution of 1-octadecanol has been measured as functions of temperature T, pressure p, and mole fraction in hexane x10 by the pendant drop method.
Abstract: The interfacial tension α between water and hexane solution of 1-octadecanol has been measured as functions of temperature T, pressure p, and mole fraction of 1-octadecanol in hexane x10 by the pendant drop method. The curves of γ vs. T, γ vs. p, and γ vs. x10 show noticeable break points. Calculated thermodynamic quantities such as energy changes, entropy changes, and volume changes associated with the adsorption show the points of discontinuity at a certain temperature, pressure, and composition, corresponding to the above breaking points. It has been clarified that the first order phase transition between the expanded and condensed states takes place at the interface like that of monomolecular films spread on water surfaces. The expanded state is characterized by a relatively high energy, high entropy, and large volume, while the condensed state by low energy, low entropy, and small volume.

Journal ArticleDOI
TL;DR: In this paper, the authors explain the thermodynamic stability of microemulsions is due to the fact that the total free energy change caused by these effects can become negative, which can explain the occurence of stable microemulsion for both non-ionic and ionic surfactants.

Journal ArticleDOI
Eva Tornberg1
TL;DR: The adsorption behaviour of three food proteins, a soy protein isolate, a sodium casein‐ate and a whey protein concentrate, at the air‐water interface has been studied by the drop volume method and indicates the following characteristics concerning the surface behaviour of the protein systems studied.
Abstract: The adsorption behaviour of three food proteins, a soy protein isolate, a sodium casein‐ate and a whey protein concentrate, at the air‐water interface has been studied by the drop volume method. The kinetics of surface tension decay were evaluated in terms of different rate‐determining steps at different ionic strengths and concentrations. This analysis indicates the following characteristics concerning the surface behaviour of the protein systems studied. The soy proteins diffuse slowly to the interface compared to the other proteins, probably due to the large particle size of the association complex of soy proteins. For the soy proteins, diffusion is slower in distilled water than in 0.2M‐NaCl solution and spreading of molecules at the interface is most easily performed in 0.2M‐NaCl solution. The whey proteins diffuse quickly to the interface, which is in accordance with their aqueous association; mainly small molecular complexes. Diffusion is slower and spreading easier in distilled water than in 0.2M‐NaCl solution. Although the caseinate has a complex quaternary structure, like the soy proteins, it has a very different surface behaviour. The diffusion step is rapid at concentrations above 10−3 wt % and contributes to a large extent to the interfacial tension decay, especially when the caseinate is dispersed in 0.2M‐NaCl solution. At a concentration of 10−3 wt % and below, the rate of the diffusion step is slowed down drastically, with an accompanying drop in the surface activity of the protein. This type of surface behaviour can be explained if the migration of the caseinates to the interface takes place via the casein monomers in the bulk phase. (Less)

Journal ArticleDOI
TL;DR: In this article, a finite element method is used to study the effect of Reynolds number and surface tension on the expansion and contraction of jets of Newtonian liquids, and it is shown that the surface tension has a considerable effect on low Reynolds number jet flows, becoming negligible at higher Reynolds numbers.

Journal ArticleDOI
TL;DR: In this paper, a finite-element numerical simulation of flow in a rotating, partially liquid-filled, rotating, horizontal cylinder is analyzed by means of finite element numerical simulation, and a boundary collocation scheme with Newton-Raphson iteration converges.
Abstract: Flow in a partly liquid-filled, rotating, horizontal cylinder is analysed by means of finite-element numerical simulation. Of alternative methods for locating the free surface, a boundary collocation scheme with Newton-Raphson iteration converges. This method forces the residual in the normal-stress boundary condition to zero at a finite set of points on the liquid meniscus. Solutions of the steady, two-dimensional, incompressible flow problem show circumferential variation of the liquid-film thickness and corresponding pressure and velocity fields, including recirculation zones. The complications of an unknown meniscus location and a nonlinear normal-stress condition when surface tension is significant are illustrated. The finite-element method proves an effective and convenient tool for such flows, in which inertial, gravitational, pressure, viscous and capillary forces are all important.

Journal ArticleDOI
A.R. Miedema1
TL;DR: In this article, it was shown that there is little difference between the values of the molar surface energies of solid and liquid pure metals, and a set of values for the surface energy of solid metallic elements is presented.
Abstract: It is demonstrated that there is little difference between the values of the molar surface energies of solid and liquid pure metals. This observation is explained and a set of values for the surface energies of solid metallic elements is presented. The relation between the surface energy, ..gamma..sub(o), and the electron density at the boundary of an atomic cell is discussed in some detail.

Book ChapterDOI
Souheng Wu1
01 Jan 1978
TL;DR: In this article, the authors discuss interfacial energy, structure, and adhesion between polymers as related to the properties of polymer blends and provide an overview of surface tension and interfacial tension.
Abstract: Publisher Summary Most small-molecule organic liquids are mutually miscible and their mixtures do not form stable interfaces. Polymers are, however, usually immiscible and their mixtures form multiphase structures with stable interfaces. The dispersion, morphology, and adhesion of the component phases are affected by the interfacial energies, which thereby play an important role in determining the mechanical properties of a multiphase polymer blend. This chapter discusses interfacial energy, structure, and adhesion between polymers as related to the properties of polymer blends. It provides an overview of surface tension and interfacial tension, and discusses various theories of interfacial tension such as Antonoff's rule, theory of Good and Girifalco, theory of fractional polarity, and lattice theories. The interfacial tension varies more slowly with temperature than the surface tension and arises mainly from the disparity between the polarities of two phases. The extent of non-polar (dispersion) interaction between the two phases does not vary greatly from system to system but that of polar interactions can vary greatly. The polar interactions largely determine the magnitude of the interfacial tension. The polarity of a polymer can be calculated from the interfacial tension between the polymer and a non-polar polymer such as polyethylene, which can be regarded to be completely nonpolar. Thus, if the interfacial tension of a polar polymer against polyethylene is known, the polarity of the polar polymer can be calculated. Adhesion is the bonding or joining of dissimilar bodies, while autohesion or cohesion refers to joining of identical bodies. Several adhesion theories have been proposed. They have been a subject of much controversy. Most theories deal with the formation of the adhesive bond. The chapter reviews various factors affecting the formation and the fracture of adhesive bonds.

Journal ArticleDOI
TL;DR: In this article, the authors compared eight possible definitions of the surface thickness for two density profiles, and then the 10-90 thickness t was shown to be in satisfactory agreement with the other six.
Abstract: We compare eight possible definitions of the surface thickness for two density profiles. One definition is eliminated, and then the 10–90 thickness t is shown to be in satisfactory agreement with the other six. Our earlier work on the liquid-vapour interface is taken further, with a physical interpretation of the slowly varying density limit for the surface energy ∈; an improved estimate of t using experimental values of ∈ and the bulk energy; and an estimate of t using experimental values of ∈ and the surface tension. We obtain t ≈ 1.3d (d is the atomic diameter) for Ar, Kr and Xe near their triple points. A comparison is made with other estimates for t/d. These vary from 1 to above 3. Our results are in best agreement with Monte-Carlo simulations of the interface. The results for liquid 4He at zero temperature are discussed briefly.

Journal ArticleDOI
TL;DR: In this article, the necessary condition for spontaneous electrocapillary emulsification to take place was found to be that the ionic strength, and hence the reciprocal double-layer thickness, of the inner phase be higher than that of the outer phase.

Journal ArticleDOI
TL;DR: In this paper, an approximation of the rigorous expression for the interfacial tension of multicomponent, polyatomic fluids was obtained to provide accurate and simple estimates of the composition dependence of the surface tension of nonaqueous, binary solutions at low vapor pressures.
Abstract: Formulas obtained by approximation of the rigorous expression for the interfacial tension of multicomponent, polyatomic fluids are shown to provide accurate and simple estimates of the composition dependence of the surface tension of nonaqueous, binary solutions at low vapor pressures. Similar formulas are recommended for multicomponent (that is, more than two components) solutions.


Journal ArticleDOI
TL;DR: In this article, explicit expressions for the Green's functions due to a point force in one of two half space fluids are presented for the case when inertial effects of the fluid are negligible (Stokes flow) and the interface between the two fluids is considered to be flat due to the action of surface tension.
Abstract: Explicit expressions for the Green's functions due to a point force in one of two half space fluids are presented for the case when inertial effects of the fluid are negligible (Stokes flow) and the interface between the two fluids is considered to be flat due to the action of surface tension. The analytic expressions are discussed in terms of singularity diagrams. For the case of a force parallel to the interface a first approximation to the interface displacement is made.

Journal ArticleDOI
TL;DR: In this paper, the interfacial properties of a system of molten polymers at a temperature just below the critical temperature of demixing are studied in the framework of a mean field theory.
Abstract: 2014 The interfacial properties of a system of molten polymers at a temperature just below the critical temperature of demixing are studied in the framework of a mean field theory. The properties of the interface are very specific, the interface is much larger than those of usual binary liquids and the interfacial tension is much smaller so that only optical methods will permit experimental study. LE JOURNAL DE PHYSIQUE TOME 39, SEPTEMBRE 1978,

Journal ArticleDOI
01 Nov 1978
TL;DR: In this article, the Gibbs adsorption isotherm has been developed for aqueous solutions containing a weak base, HCl and NaCl, which behave as ideal solutions.
Abstract: The Gibbs adsorption isotherm has been developed for aqueous solutions containing a weak base, HCl and NaCl, which behave as ideal solutions. Expressions for surface excesses of weak base, sodium ion and chloride ion are derived as functions of derivatives of surface tension with respect to the concentrations of weak base, HCl and NaCl. Dimethyldodecylamine oxide is chosen as a base, and the surface tension of its aqueous solutions has been measured at different degrees of neutralization and at different NaCl concentrations. The surface excesses of surfactant, sodium ion, and chloride ion are obtained as functions of surfactant concentration by means of the derived equations. Furthermore, possible surface hydrolysis of the surfactant is evaluated on the basis of an appropriate postulate.


Patent
10 Aug 1978
TL;DR: In this article, the surface tension properties of a wet ink printed pattern and a liquid top coat composition are compared, and the difference in surface tension is such that the liquid top-coverage composition retracts from the wet ink pattern; subsequently the ink is dried and the top coat is cured.
Abstract: Decorative articles having a three-dimensional patterned surface are formed employing the different surface tension properties of a wet ink printed pattern and a liquid top coat composition; the difference in surface tension is such that the liquid top coat composition retracts from the wet ink pattern; subsequently the ink is dried and the top coat is dried and cured.

Journal ArticleDOI
TL;DR: In this paper, a surface phonon and surface roton branch of the elementary excitation spectrum were described in terms of a surface hydrodynamics in two dimensions and the surface rotons were characterized by an energy gap of 5.3 K.
Abstract: High-precision measurements of third-sound velocity in $^{4}\mathrm{He}$ films with surface densities between 0.16 and 5.25 atomic layers have been taken between 0.1 and 1.5 K. By reformulating Landau's quantum hydrodynamics in two dimensions we have been able to accurately describe these measurements in terms of a surface phonon and surface roton branch of the elementary excitation spectrum. In the thin-film limit surface tension falls to zero and the surface rotons are characterized by an energy gap of 5.3 K.

Journal ArticleDOI
TL;DR: In this paper, the surface tension of soil solution is estimated to be 63-64 erg cm -2 in the surface soils studied, which is slightly less than that of pure water.
Abstract: Summary Because of their organic matter content, the surface tension of water of soils is about 8 to 9 erg cm -2 (8 to 9 × 10 -7 J cm -2) less than that of pure water. It is estimated that the surface tension of soil solution is 63–64 erg cm -2 in the surface soils studied.

01 Feb 1978
TL;DR: In this paper, it was shown that the vapor pressure force dominates in the lower region and the surface tension in the upper region of electron beam welding cavities, and that the region where these two forces are approximately equal is unstable and this surface tension causes inward flow of liquid metal which tends to form a projection.
Abstract: On the basis of measured temperature distributions in electron beam welding cavities it is shown that the vapor pressure force dominates in the lower region and the surface tension in the upper region. The region where these two forces are approximately equal is unstable and the surface tension force causes inward flow of liquid metal which tends to form a projection. For a specific material this projection location was found to depend on cavity depth. By postulating that the formation of liquid metal projections at this location results in cavity instabilities, a physical model for predicting when spiking would occur was purposed. A procedure then developed for determining the spiking tendency for a specified material and set of weld parameters is described.

Journal ArticleDOI
TL;DR: In this paper, the Gibbs' adsorption isotherm was used to estimate the surface tension of aqueous solutions of dodecyldimethylammonium chloride.