Bulk and Surface Properties of Liquid Al-Li and Li-Zn Alloys
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INTRODUCTION
SEVERAL different types of Li-based rechargeable batteries have attracted substantial interest. This results from an expectation of high specific energies and energy densities for such batteries system.[1] The attention has been paid for an even longer time to the use of lithium alloys as an alternative to elemental lithium. Especially interesting are the batteries working with molten salt electrolytes that operate above the melting point of lithium, the lithium-aluminum alloys,[2] for example. Apart from these, metallic systems: Li-Zn, Li-Sn, Li-Pb, etc. with organic solvent-based electrolytes at ambient temperatures were also investigated.[3,4] Thermodynamic properties of both investigated liquid alloys Al-Li[5] and Li-Zn[6,7]: indicate a negative deviation from Raoult’s law due to large number of intermetallic compounds being present in the solid state.[8, 9] An associative tendency in the liquid state can be observed.[10] This energetic effect can be explained by studying the concentration dependence of mixing functions, for which a well-pronounced peak is positioned in the vicinity of the stoichiometric compositions of the intermetallic compounds.[11–14] Thermodynamic modeling in the framework of CFM formalism[15,16] showed that Al2Li3 and LiZn2 clusters can exist and stabilize the liquid Al-Li and Li-Zn alloys. The nature of ordering in liquid investigated binaries was described and quantified using Bhatia-Thornton theory.[17,18] The degree of
ordering in the melts has been studied applying Warren-Cowley short-range order parameter (a1).[19,20] However, physicochemical properties such as density, viscosity, and surface tension of liquid Al-Li and Li-Zn alloys were not measured and they are unknown. These properties were only determined for pure liquid constituents: Al, Li, and Zn. They were reported for Al and Zn metals by many authors, e.g., Keene[21] and Gancarz et al.[22,23] etc. Data for liquid lithium are more scarce than for Al and Zn elements and were taken from.[24] Thus, the aim of this work was to (a) measure the three physicochemical properties: density, surface tension, and viscosity of liquid Al-Li and Li-Zn alloys using Draining Crucible method[25–27] over a broad temperature range (from 773 K (500 C) to 973 K (700 C)) (b) calculate them by applying CFM formalism[15,16] (c) explain and understand the influence of short-range ordering on measured properties. Surface tension modeling was also performed using the Butler model[28] but viscosity by applying common known empirical models e.g., Kucharski,[29] Kaptay,[30] Kozlov et al.[31] As final result we plan to obtain a complete database of physicochemical properties for liquid Al–Li and LiZn alloys.
II.
METHODS: EXPERIMENTAL AND MODELING
A. Draining Crucible Method
MARCELA TRYBULA, Ph.D. Student, TOMASZ GANCARZ, Assistant Professor, and WLADYSLAW GASIOR, Professor, are with the Institute of Metallurgy and Materials Science, Polish Academy of Sciences, Reymonta 25 St., 30-059 Krakow, Poland. Contact e-mail: [email protected] ALAIN PA
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