Wetting Transitions in Fluid K x KCl1− x Revisited

Abstract

Abstract Spectroscopic ellipsometry and reflectometry were employed to study the wetting behaviour of the metal–molten salt system K x (KCl)1− x at the interface to an inert sapphire wall. We present new results on the wetting film spectra and on the film thickness at solid–liquid coexistence and in the homogeneous liquid phase. The film spectra clearly show the typical absorption of the liquid state F-centre. The wetting film thickness strongly increases approaching the monotectic temperature along the liquidus line. In the homogeneous regime the film thickness decreases at constant composition with increasing temperature and at constant temperature with decreasing salt concentration in agreement with complete wetting. For the interpretation within the framework of tetra point wetting we have developed a quantitative description of the excess Gibbs energy of the system.