IMR: Development of an Electrostatic Levitation Facility for Materials Research and Education

Iowa State University, Ames IA

Investigators

Abstract

Technical Abstract A team of scientists and students at Iowa State University, Washington University and the University of Massachusetts, Amherst will develop an Electrostatic Levitation (ESL) facility at Iowa State University that will allow 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) at temperatures up to 3000K. The absence of a container or gas flow around the samples allows the liquids to be supercooled, a feature that has already enabled new high-impact investigations of the relationship between the liquid and solid phase structures in metals and alloys. A portable chamber, optimized for synchrotron x-ray diffraction measurements, will be constructed at Washington University in St. Louis. These two complementary facilities will allow studies of the development of short and medium range order in equilibrium and metastable liquids to be correlated with changes in their thermophysical, electrical and magnetic properties. The Iowa State facility 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. The ability to determine, in-situ¬, both the structure and properties of these metastable phases, their formation with composition and temperature, and their role in the formation or inhibition of stable phases at lower temperatures, will add tremendously to our understanding of stable phase formation in complex systems. General 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. Further, the glass transition, i.e. how a liquid turns into a glass, has significant practical consequences that have been recognized for thousands of years. It allows, for example, silicate glasses to be worked and blown into beautiful and practical intricate shapes. Like supercooling, the glass transition is ubiquitous, but what underlies it remains one of the outstanding problems in condensed matter and materials physics. A team of scientists and students at Iowa State University, Washington University and the University of Massachusetts, Amherst will develop a novel facility at Iowa State University that will enable 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. To avoid contamination during the measurements, the liquids will be levitated in an electric field (electrostatic levitation, ESL) and heated in vacuum. Taken together with a sister ESL chamber, designed for x-ray studies of liquids, to be constructed at Washington University in St. Louis, they will be able to correlate measurements of atomic structure and physical properties, which will add tremendously to our understanding of these complex systems.