Definition Of Surface Tension Research Articles

Condition of Mechanical Equilibrium at the Phase Interface with Arbitrary Geometry

The authors produced an expression for the mechanical equilibrium condition at the phase interface within the force definition of surface tension. This equilibrium condition is the most general one from the mathematical standpoint and takes into account the three-dimensional aspect of surface tension. Furthermore, the formula produced allows describing equilibrium on the fractal surface of the interface. The authors used the fractional integral model of fractal distribution and took the fractional order integrals over Euclidean space instead of integrating over the fractal set.

Surface thermodynamics reconsidered. Derivation of the Gokhshtein relations from the Gibbs potential and a new approach to surface stress

The terminology and definition of surface tension are discussed. In particular, the surface tension is defined as the partial derivative of the surface excess Gibbs energy with respect to an infinitesimal increment of surface area at constant temperature and pressure. The surface tension is also formulated as the sum of a stress-free component and a stress-containing component. The stress-containing component is defined as the surface stress. Finally, the case of charged surfaces is analyzed, and the Gokhshtein relations are derived from the Gibbs potential in the special case that the electrode/solution interface is ideally polarizable.

A surface tension study of liquid threads

According to symmetry of liquid threads, definitions of surface tension in axial direction and angular direction are given. The formulas of surface tension in axial direction γ z and surface tension in angular direction γ θ are derived. A scheme to calculate Δγ = γ z − γ θ is designed. We investigate seven different systems (the numbers of molecules N are 1600, 2240, 2880,3360,4000,4800 and 5280) by molecular dynamics simulations. For liquid threads, Δγ increases with the decreasing radius of dividing surface. It shows that there exists surface tension anisotropy for liquid threads. The results obtained by molecular dynamics simulations support that surface tension is dependent on the dividing surface curvature.

A theory of a curved vapor-liquid separation boundary: The lattice gas model

Molecular theory of curved vapor-liquid interphase boundaries was considered in terms of the lattice gas model. The theory uses the quasi-thermodynamic concept of curved layers of a separation boundary with a large radius. The transition from a rectangular lattice to such layers is performed by the introduction of a variable number of the nearest neighbors. The problems (1) of the transition from distributed molecular models to layer models reflecting macroscopic symmetry of the interphase boundary and (2) of a minimum linear size of the surface region to which thermodynamic approaches are applicable were considered. Equations for the quasi-equilibrium distribution of molecules at the vapor-liquid boundary in a metastable system were constructed in the quasi-chemical approximation taking into account direct correlations between the nearest interacting molecules. A metastable state is maintained by a pressure jump described by the macro-scopic Laplace equation on a separation surface inside the interphase region. Equations for local mean pressure values and normal and tangential pressure tensor components inside the interphase region were constructed. These equations were used to obtain microscopic difference mechanical equilibrium equations for curved boundaries of spherical and cylindrical drops in the metastable state. The relation between the micro-scopic difference mechanical equilibrium equations and similar differential equations and the macroscopic Laplace equation, which described pressure jump in a metastable system, was considered. Various definitions of surface tension are discussed.

Surface Tension and Wulff Shape for a Lattice Model without Spin Flip Symmetry

We propose a new definition of surface tension and check it in a spin model of the Pirogov-Sinai class without symmetry. We study the model at low temperatures on the phase transitions line and prove: (i) existence of the surface tension in the thermodynamic limit, for any orientation of the surface and in all dimensions $ d \geq 2 $; (ii) the Wulff shape constructed with such a surface tension coincides with the equilibrium shape of the cluster which appears when fixing the total spin magnetization (Wulff problem).

Striking World of Nanostructures

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Striking World of Nanostructures

Two classes of nanostructures produced by comminution of macroscopic bodied, by aggregation of free molecules or ions are characterized. Interfacial phenomena in the nanostructures are described. The definition of surface tension as an excess surface stress is given and the condition of mechanical equilibrium at an arbitrarily curved interface is formulated. The influence of interfacial phenomena on the dependence of properties of nanoparticles on their size is discussed. Thermodynamic equations are derived describing first-order and second-order phase transitions in nanoparticles. Polymorphous transformations of solid phases in the comminution process are analyzed. A chemical approach to description of solid nanoparticles, based on introduction of the chemical potential of a supramolecule and the chemical affinity of a process, is characterized. A theory of polymorphous transformations and solution of solid nanoparticles is formulated on the ground of the chemical approach. In the section devoted to aggregative systems, unusual properties of micelles and vesicles of surfactants are described: the dualism of their liquid-like and solid-like behavior and the absence of their macroscopic analog; the universal (with respect to various properties of solution) abruptness of the transition to formation of nanostructures as the critical micelle concentration is attained; the qualitative difference in the thermodynamic properties of aggregates corresponding to a maximum and a minimum in the curve of equilibrium size distribution of aggregates; and the decrease in the concentration of a surface-active ion in a micellar solution at adding its mother substance, a strong electrolyte, to the solution. An approach to specifying thermodynamic relationships for description of the lamellar (onion-like) structure of micelles is proposed.

Definition of surface tension at a non-spherical interface

The thermodynamic characteristics of a non-spherical interface are considered. Two definitions of surface tension and their relationship are analysed. It is shown that the classical Gibbs definition has a clearer physical meaning. The hydrostatic approach to the determination of the surface tension and to the first and second bending moments of an interface is applied. Within the framework of this approach the generalized Laplace equation is obtained and the strict definition is applied to the surface of tension.

Lung surfactant: How it does and does not work

Earlier analyses of the physical chemistry of lung surfactant (LS) are rejected on the grounds that the definition of surface tension is not complied with. Furthermore, with 1 or 2 exceptions the devices used to measure the properties of LS have given misleading information. On the other hand, a protein-free formulation of an artificial lung-expanding compound (ALEC) consisting of a 7:3 mole/mole mixture of dipalmitoylphosphatidylcholine and phosphatidylglycerol seems to function as a reasonably good substitute for natural LS in very premature babies. It has the following necessary properties. It spreads rapidly and spontaneously at an air/water interface at 37°C, reducing the surface tension of water by about 2/3. The unsaturated phosphatidylglycerol (PG) moiety can be squeezed out of the mixed monolayer by rapid overcompression (equivalent to exhalation) and is irreversibly lost to the surface system by reassembly into liposomes. The residual dipalmitoylphosphatidylcholine (DPPC) becomes progressively enriched to the point that, at 37°C, it condenses out as a solid phase so rigid that it prevents the alveolae from collapsing. The preparation is protein-free.

Surface tension in the two-dimensional Ising model

We examine several definitions of surface tension between oppositely magnetised phases in the two-dimensional Ising model. With nearest-neighbour attractive interactions, we prove that at low temperatures (large β) all the definitions agree with that of Onsager.

A Reexamination of Homogeneous Nucleation Theory: Thermodynamic Aspects

Abstract This paper presents a thermodynamic discussion of homogeneous nucleation. Some serious misconceptions are exposed concerning the proper thermodynamic energy representation that is required for the nucleation problem. The thermodynamic definition of surface tension is found, and the conditions for unstable equilibrium between a liquid drop and its vapor-air environment are developed. A derivation of Kelvin's equation is presented, and the free energy barrier that a cluster of molecules must surmount in order to become a growing drop is discussed. The conventional approach to this problem is compared with our treatment.

PRACTICAL APPLICATION OF SURFACE-ACTIVE DRUGS IN OPHTHALMOLOGY

<h3>WETTING AGENTS</h3> WITHIN the last twenty odd years there have been produced a number of synthetic chemicals analogous to soaps. These agents, like soaps, penetrate the "supposed tension of the surface" of any liquid but, unlike soaps, are not affected by hard water. The name ``surfaceactive agents" has been given to these synthetic preparations. The "Glossary of Physics"¹gives this definition of surface tension:... the peculiar effect of cohesion manifested at the free surface of a liquid or at the interface of two immiscible liquids, and giving the impression of a tense. elastic skin membrane. It is measured in units of force per unit length, e. g., dynes per centimeter along the line on the surface. A number of these surface-active agents have been prepared²to be used in such diverse industries as the manufacture of shampoos, dentifrices, inks, dyeing products, cosmetics, lubricating materials, the processing of leather,

Communication to the Editor. The Definition of Surface Tension.

Communication to the Editor. The Definition of Surface Tension.

XXX.The theory of electrocapillarity.—V. A note on the definition of surface tension

XXX.<i>The theory of electrocapillarity.—V. A note on the definition of surface tension</i>