Wetting, prewetting and surface freezing transitions in fluid Ga-based alloys: a surface light scattering study

Abstract

The surface energy and entropy of liquid Ga–Bi and Ga–Pb alloys have been studied by means of surface light scattering measurements at various compositions and temperatures between the respective eutectic and monotectic points. Analysis of these results using the Gibbs adsorption equation gives evidence for wetting and prewetting transitions in these alloys completely consistent with a tetra-point wetting scenario (Dietrich S and Schick M 1997 Surf. Sci. 382 178). Surface freezing transitions are observed for conditions near the liquidus curves. In view of their viscoelastic properties and their relation with the wetting film characteristics, we suggest a simple explanation for the observed surface freezing phenomena in terms of nucleation of strongly undercooled wetting films.

Perspective: Surface freezing in water: A nexus of experiments and simulations

“…Such frozen monolayers have also been observed in other chain molecules, including dry and hydrated linear alcohols [22,25]. Frozen monolayers have also been observed in some alloys, such as Au-Si [26,27], Ga-Bi [28] and Ga-Pd [28,29]. A related phenomenon, known as surface ordering, occurs in materials that form liquid crystals, where, at temperatures above T bulk o , the bulk isotropic-to-liquid crystalline transition temperature, a liquid crystalline layer forms at the vapor-liquid interface [30].…”

“…In other words, the thermodynamics of the confined system deviates so drastically from the bulk that it allows for a complete decoupling of structure and dynamics. There is a wide variety of experimental techniques that can be used for detecting liquid-to-solid structural transformation at the surface, and approaches such as surface tensiometry [20,21,[23][24][25], X-ray scattering [21,[24][25][26][27], light scattering [29], polarized video microscopy [30], elipsometry [23], surface vibrational spec- troscopy [22] and second harmonic and plasma generation spectroscopy [28] have been used to detect surface freezing in n-alkanes, n-alcohols, and metallic alloys. The type of surface freezing that only involves an enhancement of nucleation kinetics close to a vapor-liquid interface is, however, far more difficult to detect and characterize experimentally, as its only distinction with respect to bulk nucleation is in the spatiotemporal distribution of nucleation events in the confined system, and not in the final outcome of the nucleation process.…”

“…In other words, the thermodynamics of the confined system deviates so drastically from the bulk that it allows for a complete decoupling of structure and dynamics. There is a wide variety of experimental techniques that can be used for detecting liquid-to-solid structural transformation at the surface, and approaches such as surface tensiometry [20,21,[23][24][25], X-ray scattering [21,[24][25][26][27], light scattering [29], polarized video microscopy [30], elipsometry [23], surface vibrational spec-…”

Oscillatory wetting instability induced by liquid–liquid decomposition in a Ga–Pb alloy

“…[8][9][10][11] Their bulk phase behavior is characterized by a liquid-liquid miscibility gap, which in the case of the Ga-Pb alloy ranges from the monotectic T mono ϭ586 K to the critical T c ϭ879 K temperatures 12 and covers a wide composition range ͑see Fig. 1͒.…”

Aspects of prewetting at nonplanar surfaces

“…For example, Freyland et al used surface light scattering measurements to determine surface energy and entropy of liquid Ga-Bi and Ga-Pb alloys. 22 On the theoretical side prewetting transitions have been studied by a variety of methods. Here the overwhelming number of studies to date focuses on thermodynamical aspects and structural properties.…”