MRI-R2: Development of Electrostatic Levitation Facility for Neutron Scattering Studies of Liquids to be used in Fundamental Research and Education

Washington University, Saint Louis MO

Investigators

Abstract

0959465 Kelton Washington U. Technical Abstract: This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). A team of scientists and students from Washington University in St. Louis, Iowa State University in Ames, Iowa, the University of Tennessee in Knoxville, Tennessee, and the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, will develop a novel facility for neutron scattering studies of high temperature liquids (NESL, Neutron ElectroStatic Levitation). The liquids will be levitated in high vacuum using electrostatic levitation, thus avoiding container contamination. Liquids and glasses are probably the least understood phases of matter, with many outstanding questions concerning their physical properties and atomic structures. An understanding of how they crystallize and, in some cases, become glasses with cooling is incomplete. Furthermore, novel phase behavior and phase transitions in liquids at temperatures below their melting temperatures (supercooled) are largely unexplored. Since most elements are liquids only at elevated temperatures and react strongly with container materials, experimental studies of their structures and properties are difficult or impossible to accomplish. NESL will allow structural and dynamical studies of high-temperature liquids, both above and below their equilibrium melting temperatures. NESL will be optimized for elastic and inelastic neutron scattering studies, and used on the recently completed SNS, the world's most intense pulsed accelerator-based neutron source. NESL will have a tremendous impact on fundamental and basic research, and will serve as a catalyst for expanded national and international collaborations. It will allow pioneering studies of evolving short and medium range order in and liquid dynamics, addressing fundamental questions that have profound applied as well as basic interest. When coupled with specialized ESL chambers at Washington University and Iowa State University, NESL will create a unique opportunity for coordinated structural and property studies of solids, liquids and metastable phases, for sample temperatures up to 3000K. Layman Abstract: This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). While liquids and glasses have been subjects of study for millennia, they are probably the least understood states of matter. Key questions center on their structure at an atomic level, and how this structure determines their properties and their ability to change to other states. For example, in 1721, Fahrenheit discovered that under proper conditions liquids can be held at temperatures below their melting temperature without crystallizing (a common example of crystallization is when liquid water turns into ice). Surprisingly, almost 300 years later we still don't completely understand the origin of this resistance to form the crystal phase, nor do we understand the atomic processes that occur during crystallization and their relations to the liquid atomic structure. In addition to discontinuous transformations like crystallization, if they are cooled fast enough, liquids can also solidify by a continuous process to become a glass, where the atoms are frozen into the structure of the liquid. While cooling through the glass transition has been a technique commonly used by glassblowers for centuries to make intricate and beautiful glass objects, the process is poorly understood, claimed to be the most challenging unsolved problem in the physics of materials. Neutron scattering studies of liquids offer a unique way to unravel these and related questions. However, a key problem is that the liquid cannot be held in a container, since contact with the container will induce crystallization before measurements of the supercooled liquid (i.e. liquid below its melting temperature) can be made. Building on their successes in the development of techniques for x-ray scattering studies of liquids, a team of scientists at Washington University in St. Louis, Iowa State University in Ames, Iowa, the University of Tennessee in Knoxville, Tennessee, and the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, will develop a facility that is unique in the world, to be used at the SNS for neutron scattering studies of levitated liquids, thus avoiding the need for a container. In addition to their importance to basic understanding, the capabilities that this facility offers will have profound practical technological importance, leading to refined methods for materials development.