Interfacial Properties of Liquid Alloys :An Expérimental study on Ga-Bi and Ga-Ge

Interfacial phase like wetting and prewetting transitions are of considérable interest in physics and chemistry of condensed marier since the represent phase transition is reduced dimensionality. Besides this. interfacial properties are of profound practical and technological interest. Most Systems studied experimentally in this respect are characterized by Van der Waals intermolecular interactions. However, in the last few years is shown that Coulomb liquids like liquid alloys or métal molten salt solutions exhibit interfacial phase transition similar to those known in Van der Waals Systems.
In order to get more insight into thèse phenomena the fluid-vapor interface of two différent alloy systems hâve been studied using ellipsometry. Ga-Bi is binary ally, with large positive déviations from Raoult’s law, exhibiting a distinct miscibility gap. Approaching liquid-liquid coexistence a bi-rich film completely wets the fluid-vapor interface. As can be estimated from ellipsometric results the film thickness jumps, at the monotectic température to a value of about 50 A . In contrast, Ga-Ge shows continuous miscibility and déviâtes much less from idéal mixing. As the Ge concentration in liquid Ga increases along the solid-liquid coexistence curve the optical properties at the surface also vary continuously, which can be modeled within a simple effective médium approach.

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