Investigations of Deeply Undercooled Liquids and High Temperature Phase Formation using Electrostatic Levitation and Contactless Measurement Techniques.

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****Technical Abstract****A team of scientists and students at Iowa State University will study the structural, electronic, and magnetic properties of deeply undercooled liquids and metastable crystalline phases using a newly constructed Electrostatic Levitation (ISU-ESL) facility. Measurements of the thermophysical properties (density, surface tension, viscosity and calorimetry) as well as magnetic susceptibility and electrical resistance (using a novel tunnel diode resonator technique) can be done at temperatures up to 2500 K. These property measurements will be correlated with x-ray and neutron scattering measurements of microscopic structural properties performed at the Advanced Photon Source and Spallation Neutron Source using ESL chambers specifically designed for scattering measurements. The coordinated use of these facilities will provide new information on liquid-liquid phase transitions, phase-transformation kinetics during solidification and their effect on materials processing, evolving order in systems undergoing structural and magnetic transitions, the detection and characterization of metastable phases and the influence of magnetic fields on the solidification process.****Non-Technical Abstract****Liquid and glasses are around us everyday, yet in many ways they are only poorly understood. Neither their atomic structures, the phase changes that occur within them, nor their electrical and magnetic properties are well known. For example, in 1721 Fahrenheit discovered a tendency for water cooled to below its freezing temperature (a supercooled liquid) to resist the formation of the crystalline phase, ice. Supercooling is now known to be possible in all liquids. Why it happens, however, and what changes occur in the supercooled state of the liquid before it crystallizes, are questions of current interest. As some liquids solidify, they can form metastable phases that exist only at high temperature. The properties of these metastable phases remain relatively unexplored, and they can strongly influence the specific path to the final product. A team of scientists and students will use a novel facility recently commissioned at Iowa State University that enables measurements of thermophysical properties, such as the density, surface tension, viscosity, as well as electrical and magnetic properties, of liquids above and below their melting temperatures and high temperature metastable solid phases. To avoid contamination during the measurements, the liquids are levitated in an electric field (electrostatic levitation, ESL) and heated in vacuum. Taken together with a sister ESL facilities at the Advanced Photon Source (Argonne National Laboratory), designed for x-ray studies of liquids, and neutron scattering investigations at the Spallation Neutron Source (Oak Ridge National Laboratory), they will be able to correlate measurements of atomic structure and physical properties, which will add tremendously to our understanding of complex systems at high temperatures.