Solid-liquid interface surface Gibbs free energy

The cosine cannot exceed one. Then we might ask What happens, if 7s — 7sl — 7l > 0 or 7S - 7Si is higher than 7// Does this not violate Young s equation No, it does not because in thermodynamic equilibrium 7s — Ysl — 1l can never become positive. This is easy to see. If we could create a situation with 7s > 7SL + 7l, then the Gibbs free energy of the system could decrease by forming a continuous liquid film on the solid surface. Vapor would condense onto the solid until such a film is formed and the free solid surface would be replaced to a solid-liquid interface plus a liquid surface. 

Prediction of the adhesion forces lies beyond the scope of the present work however, certain observations are possible. Initially, deformation in a pressure drop field occurs, satisfying equation (4). Then, non-spherical deformation can occur whenever a ganglion is touching either the solid spheres or the overlying surface since there is adhesion between the ganglion and the solid. Separation of the two phases and transformation of the air-solid interface into separate air-liquid and liquid-solid interfaces requires an increase in the Gibbs free energy which, at constant temperature and pressure, becomes the work of adhesion per unit area, i.e.. 

Before approaching the problem of dynamics of contact line, we shall briefly review the equilibrium properties of gas-liquid interfaces and their dependence on the proximity to solid surfaces. We shall consider the simplest one-component system a liquid in equilibrium with its vapor. Thermodynamic equilibrium in a two-phase system implies equilibrium of the interphase boundary, which tends to minimize its area. The thermodynamic quantity that expresses additional energy carried by the interface is surface tension, defined as the derivative of the Helmholtz or Gibbs free energy with respect to interfacial area E ... 

The fact that a liquid can be supercooled is best understood qualitatively in the framework of classical nucleation theory (CNT) (see e.g. Ref. [3]). According to CNT the free energy of a spherical nucleus that forms in a supersaturated solution contains two terms. The first term accounts for the fact that the solid phase is more stable than the liquid. This term is negative and proportional to the volume of the nucleus. The second term is a surface term. It describes the free energy needed to create a solid/liquid interface. This term is positive and proportional to the surface area of the nucleus. The (Gibbs) free energy of a spherical nucleus of radius R has the following form ... 

Assumption 5 In the definition of the isotherm, the convention is adopted that the solvent (if pure) or the weak solvent (in a mixed mobile phase) is not adsorbed [8]. Riedo and Kov ts [9] have given a detailed discussion of this problem. They have shown that the retention in liquid-solid i.e., adsorption) chromatography can best be described in terms of the Gibbs excess free energy of adsorption. But it is impossible to define the surface concentration of an adsorbate without defining the interface between the adsorbed layer and the bulk solvent. This in turn requires a convention regarding the adsorption equilibrium [8,9]. The most convenient convention for liquid chromatography is to decide that the mobile phase (if pure) or the weak solvent (if the mobile phase is a mixture) is not adsorbed [8]. Then, the mass balance of the weak solvent disappears. If the additive is not adsorbed itself or is weakly adsorbed, its mass balance may be omitted [30]. 

In 1805 Young established a relationship between the contact angle of a drop of liquid and the interfacial tensions at the three-phase contact line between a solid, a liquid, and its vapor at equilibrium (Eq. 10.1). J. Willard Gibbs in 1928 then derived the contact angle 9, from thermodynamic quantities, the surface free energies for the three interfaces. Substantial refinements in terms of the nature of the forces involved in the wetting process have been made since then, and interested readers can consult fundamental texts on surface forces. ... 

---