Showing papers on "Surface tension published in 1977"

Principles of colloid and surface chemistry

Abstract: Colloid and surface chemistry - scope and variables sedimentation and diffusion and their equilibrium solution thermodynamics - osmotic and Donnan equilibria the rheology of dispersions static and dynamic light scattering and other radiation scattering surface tension and contact angle - application to pure substances adsorption from solution and monolayer formation colloidal structures in surfactant solutions - association colloids adsorption at gas-solid interfaces van der Waals forces the electrical double layer and double-layer interactions electrophoresis and other electrokinetic phenomena electrostatic and polymer-induced colloid stability appendix A - examples of expansions encountered in this book appendix B - units - CGS-SI interconversions appendix C - statistics of discrete and continuous distributions of data appendix D - list of worked-out examples

Surface rippling induced by surface‐tension gradients during laser surface melting and alloying

Abstract: During laser surface melting and alloying, temperature gradients on the melt surface between the laser‐beam impact point and the intersection line of the solid‐liquid interface with the surface generate surface‐tension gradients that sweep liquid away from beam impact point. The resulting flow of liquid creates a depression of the liquid surface beneath the beam and ridging of the liquid surface elsewhere. As the beam passes to other areas of the surface, this distortion of the liquid surface is frozen in, creating a roughened rippled surface. If the laser‐beam sweep velocity exceeds a critical velocity, the liquid does not have sufficient time to form ripples, and rippling from surface‐tension gradients can be avoided.

A grain boundary groove measurement of the surface tension between ice and water

Abstract: The surface tension between ice and water has been measured by observations of the equilibrium shape of grain boundary grooves at an interface stabilized by an imposed temperature gradient The experiments have been designed to minimize the perturbing effects of heat flow in the cell walls which contain the samples The observed grooves are in agreement with the theory of Nash and Glicksman (1971) which predicts groove shapes for the case of unequal thermal conductivities in the two phases The measurements give a value of 29·1±0·8 mJ m−2 for the ice-water surface tension

Analysis of Morphology Formation in Elastomer Blends

Abstract: Based on the assumption that an equilibrium particle size of dispersed phase will be reached when the breaking-down rate and the coalescence rate are balanced, a theoretical expression was obtained. The theory showed qualitatively that the equilibrium particle size becomes smaller when (1) the stress field is increased, (2) the interfacial tension between matrix and dispersed phase becomes smaller, and (3) the concentration of dispersed phase decreases. Qualitative verification of the theory was obtained by experimental examination of the NR-EPM blend system. In practice, in order to obtain a small particle size in a short time at above 20% volume fraction, the matching of rheological properties of the matrix and the dispersed phase is desirable. On changing from internal mixer to mill, the temperature became one of the most influential factors that control the particle size. Future work, such as the quantitative value of interfacial tension as a function of temperature, and macroscopic breaking ...

Formation of the hexagonal pattern on the surface of a ferromagnetic fluid in an applied magnetic field

Abstract: When a ferromagnetic fluid with a horizontal free surface is subjected to a uniform vertical applied magnetic field B0, it is known (Cowley & Rosensweig 1967) that the surface may be unstable when the field strength exceeds a certain critical value Bc. In this paper we consider, by means of an energy minimization principle, the possible forms that the surface may then take. Under the assumption that |μ − 1| [Lt ] 1 (where μ is the magnetic permeability of the fluid), it is shown that when B0 is near to Bc there are three equilibrium configurations for the surface: (i) flat surface, (ii) stationary hexagonal pattern, (iii) stationary square pattern. Configuration (i) is stable for B0 Bc and B0−Bc sufficiently small, and (iii) is stable for some higher values of B0. In each configuration the fluid is static, and the surface is in equilibrium under the joint action of gravity, surface tension, and magnetic forces. The amplitude of the surface perturbation in cases (ii) and (iii) is calculated, and hysteresis effects associated with increase and decrease of B0 are discussed.

The molecular dynamics simulation of a small drop

Abstract: Liquid microdrops with the Lennard-Jones potential have been investigated by the molecular dynamics technique. The temperature dependence of energy and the influence of temperature, volume, and the number of molecules on the density profile and the pressure tensor profile have been studied. The surface tension and the radii of the equimolecular surface and the surface of tension have been calculated. The surface tension has been shown to increase when the drop size decreases.

On deviations from Young's equation

Abstract: Although Young's equation, γS=γSL+γL cos θC, is one of the oldest and most-used equations of classical physics and chemistry, it is in a rather delicate position scientifically, in that it is virtually impossible to prove experimentally This is due, of course, to the uncertainties in the measurement of γS and γSL, the solid–air and solid–liquid surface tensions Recently the validity of Young's equation has been questioned as the result of a theoretical analysis of the three-phase contact region where the liquid–air surface tension, γL, may be modified by interaction with the nearby substrateThe present paper argues that Young's equation is a “macroscopic” equation which does not concern itself with the microscopic shape of the liquid surface in the vicinity of the three-phase contact region The concept of a microscopic contact angle θP is introduced θP is the angle that the free liquid surface makes with the substrate when the liquid thickness is ≪∼ 10 A, ie, microscopically near the three-phase contact line The contact angle θC given by Young's equation is shown to be the angle that the liquid surface makes with the substrate at microscopically large distances from the contact line where the modification of surface tensions by interaction is negligible (> 10 A) The connection between θP and θC is established by making only very general statements about the nature of this interaction and does not impose the unphysical restrictions on the profile shape in the neighbourhood of the three-phase contact line which lead to the conclusions of Jameson and del Cerro

Effect of Pressure on Interfacial Tension between Oil and Water

Abstract: The interfacial tension of hexane, octane, carbon tetrachloride and benzene against water was measured as a function of pressure up to 150 MPa at 30315 K, using a newly designed apparatus The interfacial tension showed definite increase with pressure and positive volume change was found on interface formation

Molten Salts: Volume 4, Part 3, Bromides and Mixtures; Iodides and mixtures—Electrical conductance, density, viscosity, and surface tension data

Abstract: Data on the electrical conductance, density, viscosity, and surface tension of bromide mixtures and iodide mixtures have been systematically collected and evaluated. Results are given for eighty‐five binary mixtures over a range of compositions and temperatures. Values of the above properties for twenty‐three single bromide and iodide salts are also given.

Interfacial tensions in Zn, Zn-Sn and Zn-Sn-Pb systems

Abstract: Intergranular and solid-liquid interfacial tensions have been determined for Zn-Sn and Zn-Sn-Pb systems. The temperature coefficient of the intergranular tension of solid zinc is negative. Solid-liquid interfacial tension for the Zn-Sn system increases as the tin content increases; the σsl values fit an equation derived from statistical thermodynamics which allows us to calculate the solid-liquid interfacial tension of pure Zn. The isotherm at 330 °C of liquid-solid interfacial tension in the ternary Zn-Sn-Pb system shows a decrease in σsl as the Zn content in the liquid phase increases, which is in qualitative agreement with theoretical predictions.

Measurement of surface tension by lattice parameter changes: theory for faceted microcrystals

Abstract: A number of workers have estimated surface tensions of solids from measurements of the differences in the lattice parameters of bulk crystals and microcrystals. The data are then analysed by an expression valid only for spherical, isotropic microcrystals. The author discusses problems arising from the fact that real microcrystals are generally faceted. A general expression is given for the change in volume of a microcrystal for an arbitrarily anisotropic surface tension and arbitrary crystal habit; common special cases are also given. The discussion of the relation between the volume change and the change in X-ray lattice parameter includes the effects of the dispersions in crystalline sizes and shapes, and the possible non-uniformity in internal strain produced. It is concluded that any errors will be small.

On the Variability of Surface Tension with Mean Wind Speed

Abstract: In situ measurements of surface tension obtained by R.V. Gauss under coastal (North Sea of the Island of Sylt) and by R.V. Meteor under open sea conditions (GATE area) are Compared with time variations of the surface mean wind speed. The results indicate that the surface tension of the sea surface may attain values which are 21 dyn cm−1 below the values obtained from the Fleming-Revelle formula, if the mean wind speed decreases steadily to less than 5 m s−1 and the biological productivity within the upper layers of the water is significant.

Critical review of concepts common to cohesive energy density, surface tension, tensile strength, heat of mixing, interfacial tension, and butt joint strength

Abstract: A simple but crude theoretical model involves summation of the pair potential function by integration and the use of dispersion, polar, and induction interactions for establishing the pair potential. For single-component systems the cohesive energy density, δ2, the surface tension, γ, and the molar volume, Vm, are important. The theoretical model, as related to single-component systems, predicts a proportionality between δ2 and γ/V m 1 3 for molten metals and organic liquids, an increasing trend of γ with δ for polymers, and a maximum ideal tensile strength equal to about one-fourth of δ2 for polymers and metals. Most of the experimental results are reasonably consistent with the theoretical predictions. For two-component interactions the model must be further modified. The δA or γA values are measures of the intensity of interactions within component A. For predicting the A–B interactions, the nature of the interactions within A and B must also be defined in terms of the fractional polarities pA and pB. The value of pA can be determined either from the ionization potential, the polarizability, and the dipole moment of A or by interacting the polar material A with a nonpolar material B. The theory allows the prediction of the heat of mixing and of the ideal butt joint strength from δA, δB, pA, and pB and the prediction of interfacial tension from γA, γB, pA, and pB. While most of the available experimental data are poorly suited for exact quantitative testing of the theory, they are semiquantitatively consistent with it. The theory is useful for interpreting experimental data on polymer solubility, adhesive bond strength, wettability of polymers, and interfacial tension involving organic liquids and water or mercury. In particular, the interfacial tension between mercury and non-hydrogen-bonding organic liquids can be calculated quite accurately with the aid of the fractional polarities.

Lung surface tension and air space dimensions from multiple pressure-volume curves

Abstract: Pressure-volume (PV) curves of excised cat, dog, rabbit, and rat lungs were determined in a sequence of three conditions: 1) normal-surface, air-filled; 2) saline-filled; and 3) polyoxyethylene (20) sorbitan monolaurate-(Tween 20) surface, air-filled. Since the surface tension of lung washings containing 2% Tween 20 is constant, the Tween-surface air-filled lungs presumably exhibit the pressure-volume behavior of lungs with constant surface tension. These data along with the assumption of equivalent geometry in the three conditions permit calculation of the variation of surface tension in the normal lung as a function of volume without assuming a specific surface area vs. volume function or a maximum surface tension. The calculated surface tension dropped during deflation from a high of 50 dyn/cm total lung capacity (TLC) to a low of 4 dyn/cm (less than 25% TLC) with the species being roughly similar. The PV behavior of Tween-surface lungs appears to fit a simple model of alveolar expansion. Air dimensions calculated for the four species on the basis of this model are ordered in the same sequence as morphological measurements, but larger in magnitude.