Surface Tension of Liquid Alkali, Alkaline, and Main Group Metals: Theoretical Treatment and Relationship Investigations
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THE study of thermophysical properties is a continuous activity of many research groups. Data on thermophysical properties are needed not only to plan, conduct, and control technological processes but also to provide a ground to our understanding of the basic physics. Among these properties, the surface tension of liquid metals is a particularly interesting quantity. It is a scientifically and technologically interesting parameter and is one of the basic characteristics of matter in the liquid phase, which defines its behavior in the processes of wetting and others, and plays a central role in casting and welding processes. Unfortunately, the surface tension of liquid metals is difficult to measure accurately, and consequently, the available experimental data show a large scatter and the agreement is quite poor. The surface tension has been measured for most of the metallic elements.[1–16] The data reported in the literature are not in good agreement and suffer from experimental problems that are essentially due to the type of measuring apparatus, the degree of measurement accuracy, the use of incorrect density data, and the presence of surface-active impurities in the metal such as oxygen, and so they are strongly dependent on the oxygen concentration in the liquid phase. The effects of surface-active species on the surface tensions of liquid metals are important in numerous industrial applications. Partially due to the difficulty of their determination, there is a real dearth for reliable experimental data. FATHI AQRA, Associate Professor, and AHMED AYYAD, Assistant Professor, are with the Department of Chemistry, Faculty of Science and Technology, Hebron University, P.O. BOX 40, Hebron, West Bank, Palestine. Contact e-mail: [email protected] Manuscript submitted November 3, 2010. Article published online April 2, 2011 2680—VOLUME 42A, SEPTEMBER 2011
In view of this, establishing an accurate, successful, and universal theoretical model for calculating the surface tension of liquid metals is necessary.[17–27] Therefore, this article presents a sound theoretical examination and a unique and interesting approach to predicting the surface tension of liquid metals at different temperatures and at the corresponding melting point, based on thermodynamic fundamentals and properties. This model was tested before on pure liquid gallium,[28] bismuth,[29] and mercury.[30] To verify the model, this article contributes to the existing literature on surface tension determination of liquid alkali, alkaline, and main group metals at melting point, as well as to pure liquid lithium as a function of temperature, in the range of 454 K to 1300 K (181 °C to 1027 °C). The calculated values are strictly compared with the experimentally reported data. Moreover, the relations of the calculated surface tension of alkali metals to atomic radius, heat of fusion, and specific heat capacity are described. It is felt that this article describes the most accurate and appropriate theoretical method presently available for the calculation o
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