SURFACE AND INTERFACIAL-TENSIONS OF IRON-BASED SYSTEMS

A description is given where surfaces are treated as separate phases with a thickness corresponding to a monolayer. The surface tension of liquids is a measure of the excess chemical potential of the surface atoms relative to the bulk atoms. Equations for the calculation of the surface composition and surface/interfacial tensions of liquid mixtures are developed. Excellent correspondence between calculated and experimental surface/interfacial tension values was obtained for several non-ideal iron based systems, including Fe-Si, Fe-Cu, Fe-O and Fe-slag systems. When a low surface tension solute (Si) is added to a solvent with a high surface tension (Fe), the solute generally tends to concentrate on the surface and the surface tension of the mixture is decreased. However, in cases with strong chemical interaction such as between Fe and Si, Si is drawn into the bulk of the Fe. This results in surface tension values with positive deviation from the additive rule. In terms of iron-slag interfacial tensions, the presence of slag components which increases the activity of oxygen due to iron-slag exchange reactions, will reduce the interfacial tension. These slag or slightly higher than that of FeO.