Levitated Liquids

LB Skinner, P Kidkunthod & AC Barnes

Collaborators: L Hennet (CNRS-Orleans)

We are also interested in studying high temperature levitated liquids in situ. Aerodynamic levitation, which is simply floating of the sample on an upwards gas stream (see fig), combined with laser heating allows sample temperatures up to 3500K to be accessed. The floating of the sample eliminates both container derived contamination and chemical reactions. This means we can easily melt and study materials that were previously very difficult to melt and keep pure. Levitation also allows us to study the supercooled liquid state, as the crystal nucleation rate is reduced by the absence of a solid container. In situ study of supercooled liquids is vital for understanding many aspects of polyamorphism, crystallisation and the glass transition. Levitation allows us to extend research to in high melting point and chemically aggressive materials.

Schematic of an aerodynamic levitator.

One aspect of these studies is in situ diffraction and aerodynamic levitation studies, that we are involved with at ILL and ESRF through collaboration with Louis Hennet at CNRS-Orleans (visit his website).

Contactless electrical conductivity of levitated liquids

A second in-situ measurement we have developed is electrical conductivity. For many substances electrical conductivity is trivial to measure, however for several very high melting point liquids, and chemically aggressive liquids, a non-contact technique is needed to avoid contamination of the sample. We have developed an oscillating inductive coil method to make such measurements on levitated samples.

Schematic (a) and photo (b) of coil and pivot system. coil moves up above sample for effectie empty coil calibration, then around sample for resistivity/conductivity measurement via change in inductance and resistance of coil, due to presence of sample.

This measures change in resistance and inductance of a coil due to the eddy currents induced in the sample by the coil's field. Oscillation of the coil allows continuous recalibration for heating effects on the coil. This technique us to make measurements on metallic and semiconducting liquids at temperatures up to 3000 K in the stable liquid and supercooled liquid regimes.

Results for liquid and solid Ge are shown in fig below (from [1])

References

[1] L.B. Skinner & A.C. Barnes, An oscillating coil system for contactless electrical conductivity measurements of aerodymically levitated liquids. Rev. Sci. Instrum., 77, 123904 (2006).