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Surface tension
About: Surface tension is a research topic. Over the lifetime, 25410 publications have been published within this topic receiving 695471 citations.
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TL;DR: In this paper, the authors investigated how the vibrations of a non-rotating liquid droplet are affected by the asphericity and additional restoring forces that the levitating field introduces and showed that the expected single frequency of the fundamental mode is split into either three, when there is an axis of rotational symmetry, or five unequally spaced bands.
Abstract: In experiments to measure the surface energy of a magnetically levitated molten metal droplet by observation of its oscillation frequencies, Rayleigh's equation is usually used. This assumes that the equilibrium shape is a sphere, and the surface restoring force is due only to surface tension. This work investigates how the vibrations of a non-rotating liquid droplet are affected by the asphericity and additional restoring forces that the levitating field introduces. The calculations show that the expected single frequency of the fundamental mode is split into either three, when there is an axis of rotational symmetry, or five unequally spaced bands. Frequencies, on average, are higher than those of an unconstrained droplet; the surface tension appears to be increased over its normal value. This requires a small correction to be made in all analyses of surface energy. A frequency sum rule is derived from a simplified model of the magnetic field which allows the corresponding Rayleigh frequency to be evaluated from the observed frequencies of the fundamental and translational modes. A more detailed analysis shows a similar correction but one that is also sensitive to the position of the droplet in the field.
281 citations
TL;DR: In this paper, the authors apply fundamental geometrical and statistical mechanical principles to the terrace ledge kink (TLK) model of crystalline surfaces, and derive a two-parameter theory of the anisotropy of surface tension (specific free energy).
281 citations
15 Jun 1998
TL;DR: In this article, the authors describe the results of industrial emulsification by the mean droplet size and the flux of the disperse phase, which is defined as the ratio of the droplet density to the size of the emulsifier molecules.
Abstract: Conventional devices used in industrial emulsification processes disperse the inner phase by droplet disruption of high energetic laminar or turbulent flow. Membrane emulsification is different because small droplets are directly formed at the surface of a microporous membrane. Energy consumption of the process is lower, and the stresses on the system at the membrane surface and inside the pores are smaller. This allows processing of shear-sensitive substances. The result of the emulsification process can be described by the mean droplet size and the flux of the disperse phase. Among other parameters, pore size of the membrane, pressure of the disperse phase, and adsorption kinetics of the emulsifier influence the results of emulsification. The faster the emulsifier molecules adsorb at newly formed interfaces, the smaller the droplets of the emulsion produced. Transmembrane pressure greatly influences the flux but causes little change in droplet size.
281 citations
TL;DR: In this article, the critical micelle concentration (cmc) and area per molecule (Amin) are shown to deviate from the expected patterns of behavior as the number of carbon atoms in the alkyl chain (n) increases beyond a certain maximum.
Abstract: Bis(quaternary ammonium halide) surfactants (gemini surfactants) having, variously, diethyl ether, monohydroxypropyl, and dihydroxybutyl spacer groups have been investigated by surface tension, interfacial tension, and steady-state fluorescence techniques. The critical micelle concentration (cmc) and area per molecule (Amin) are shown to deviate from the expected patterns of behavior as the number of carbon atoms in the alkyl chain (n) increases beyond a certain maximum. This aberrant behavior is observed at the hydrocarbon/water as well as the aqueous/air interface. The unexpected values of the physicochemical parameters at long alkyl chain length have been interpreted on the basis of a concentration region in which submicellar or multilayer structures are forming. Fluorescence measurements provide confirmation of cmc values by an alternative technique. Comparison of the fluorescence emission maxima profiles of the gemini surfactants with those of their monoquaternary analogues demonstrates that there is...
281 citations
TL;DR: Pendant drop tensiometry enhanced by video-image digitization is shown to be a useful tool for the experimental measurement of the relaxation in interfacial tension due to the adsorption of surfactant at a fluid interface as discussed by the authors.
Abstract: Pendant drop tensiometry enhanced by video-image digitization is shown to be a useful tool for the experimental measurement of the relaxation in interfacial tension due to the adsorption of surfactant at a fluid interface Using this method, profiles of the relaxation in surface tension of a diffusion-controlled, nonionic polyethoxy surfactant were measured A diffusion coefficient was computed by comparing these profiles with numerical solutions of the bulk surfactant diffusion equation and a Frumkin equilibrium adsorption isotherm This comparison was made for the entire relaxation period This method establishes a more reproducible diffusion coefficient than current techniques that utilize only the short- or long-time parts of the relaxation spectrum In addition, lower bounds on the kinetic constants for the sorption process are inferred for the polyethoxy surfactant used by comparing numerical solutions of mixed diffusion and surface kinetic transfer with the diffusion-limited result
279 citations