Molten Alkali Halides: Straightforward Prediction of Surface Tension
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lten salts are substances that are solids at room temperature and liquids at high temperature. They are compounds formed by cations and anions. Consequently, their properties are determined by the electronic structure of these ions.[1] Molten alkali halides are of great importance in industry, and they possess a scientifically interesting behavior. The subject of surface tension determination is of great importance in many different fields of materials engineering. Information on the surface tension of molten salts is needed for hightemperature fuel cells, thermal-energy storage units, fusion reactors, and production of new materials in microgravity conditions. The surface tension of high-temperature melts is not well established.[2] Considerable efforts have been made in regard to the experimental measurement of the surface tension of molten salts, but the available data are limited due to experimental difficulties, such as strong chemical activity, that are corrosive to the materials of the container and sensors. Therefore, precise surface tension data for molten salts and the establishment of theoretical models are always required. Although there are reported models on the prediction of the surface tension of pure molten alkali halides,[3–11] it is still necessary to develop simple models or empirical relations capable of calculating such a thermophysical FATHI AQRA, Associate Professor, is with the Department of Chemistry, Faculty of Science and Technology, Hebron University, P. O. Box 40, Hebron, West Bank, Palestine. Contact e-mail: fathiaqra [email protected] Manuscript submitted November 22, 2013. Article published online March 25, 2014 METALLURGICAL AND MATERIALS TRANSACTIONS A
property. The present work shows a relation that correlates the surface tension with radius ratio, internuclear distance, and molar volume. The accuracy of this formula lies in the accuracy of the constants. It may be one of the acceptable tools in this respect and will be considered as a good scientific contribution. A simple calculation of the volume-dependent surface tension of molten alkali halide salts is the objective of this work. The force exerted on the liquid surface per unit length is referred to as the surface tension. In other words, it is the force (per unit length) required to change the surface shape of the liquid. Surface tension is a fluid property and is generally a function of temperature and the medium in contact with the fluid. The liquid surface usually takes an equilibrium configuration with minimum energy due to the high mobility of liquid molecules. Because the liquid fails with respect to elastic deformation resistance, surface tension equals surface stress when surface adsorption is not taken into account, which is defined as the reversible work per unit area involved in forming a new surface of a substance plastically. The development of scientific research leads to a rapid increase of experimental data. In order to make proper use of the information, a careful comparison with theoretical calculations must be done. Th
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