Levitation techniques offer unique opportunities for the accurate determination of thermophysical properties of liquid metals and alloys at high temperatures. Supercooled liquid metals can be studied at temperatures 200-500 K below their freezing points.
1. Introduction
Some of the most elusive thermophysical properties are those of undercooled liquid metals at high temperatures, including enthalpy increments, heats of fusion, heat capacities, spectral emissivities and reflectivities, indices of refraction, dielectric constants, surface tensions, viscosities, thermal conductivities, thermal diffusivities, densities, thermal expansion coefficients and compressibilities [1]. In order to realize a wide range of temperature for the accurate establishment of these properties, one needs a rapid heating-cooling technique with minimum likelihood of contamination yet with maximum opportunity for visual, photographic or video observation and ease of mechanical manipulation. Also, one needs a high precision calorimeter for evaluating thermodynamic properties.
An almost perfect answer to these requirements is the technique of electromagnetic levitation. Although early patents described usable levitation systems [2[, it was not until the 1950s when engineers and scientists at Westinghouse devised a practical system for levitation and heating of kilogram samples of titanium aimed at the production of ultrapure metal [3]. Interest in the applications of levitation was still minimal, however, when a review paper describing experimental designs of levitation coils and some quantitative studies of the Fe-C-O system was presented in 1964 [4]. Some typical coil designs which have been used for levitation techniques are presented in Fig. 1. Improved designs