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

技术摘要：该奖项由2009年美国复苏和再投资法案(公共法律111-5)资助。来自圣路易斯华盛顿大学、爱荷华州艾姆斯爱荷华州立大学、田纳西州诺克斯维尔田纳西大学和橡树岭国家实验室散裂中子源(SNS)的科学家和学生组成的团队，将开发一种用于高温液体(NESL，中子静电悬浮)中子散射研究的新型设施。液体将利用静电悬浮在高真空中悬浮，从而避免容器污染。液体和玻璃可能是人们最不了解的物质相，有许多关于它们的物理性质和原子结构的悬而未决的问题。对它们是如何结晶的，在某些情况下，随着冷却而变成玻璃的理解是不完整的。此外，液体在低于其熔化温度(过冷)时的新的相行为和相变在很大程度上是未被探索的。由于大多数元素只有在高温下才是液体，并且与容器材料发生强烈反应，因此很难或不可能完成对其结构和性能的实验研究。NESL将允许对高于和低于平衡熔化温度的高温液体进行结构和动力学研究。NESL将被优化用于弹性和非弹性中子散射研究，并用于最近完成的SNS，世界上最强的基于脉冲加速器的中子源。NESL将对基础和基础研究产生巨大影响，并将成为扩大国内和国际合作的催化剂。它将使中短期有序演化和液体动力学的开创性研究成为可能，解决具有深远应用和基本兴趣的基本问题。当与华盛顿大学和爱荷华州立大学专门的ESL室相结合时，NESL将创造一个独特的机会，对固体、液体和亚稳定相进行结构和性质的协调研究，样品温度高达3000 K。莱曼摘要：该奖项是根据2009年美国复苏和再投资法案(公共法律111-5)资助的。尽管液体和玻璃数千年来一直是研究的对象，但它们可能是最不被理解的物质状态。关键问题集中在它们在原子水平上的结构，以及这种结构如何决定它们的性质以及它们改变到其他状态的能力。例如，1721年，Fahrenheit发现，在适当的条件下，液体可以保持在低于其熔化温度的温度而不结晶(结晶的一个常见例子是液态水变成冰)。令人惊讶的是，近300年后，我们仍然不完全了解这种形成晶相的阻力的起源，也不了解结晶过程中发生的原子过程及其与液体原子结构的关系。除了结晶等不连续的转变外，如果冷却速度足够快，液体还可以通过连续的过程凝固成玻璃，在那里原子被冻结在液体的结构中。尽管几个世纪以来，通过玻璃转变进行冷却一直是吹制玻璃工人常用的一种技术，以制造复杂而美丽的玻璃物体，但人们对这一过程知之甚少，据称这是材料物理学中最具挑战性的悬而未决的问题。液体的中子散射研究为解开这些问题和相关问题提供了一种独特的方法。然而，一个关键的问题是，液体不能保存在容器中，因为在测量过冷液体(即低于其熔化温度的液体)之前，与容器接触会导致结晶。圣路易斯的华盛顿大学、爱荷华州艾姆斯的爱荷华州立大学、田纳西州诺克斯维尔的田纳西大学和橡树岭国家实验室的散裂中子源(SNS)的科学家团队在开发液体X射线散射研究技术的成功基础上，将开发出一种世界上独一无二的设施，供SNS用于悬浮液体的中子散射研究，从而避免了对容器的需要。除了它们对基本理解的重要性外，该设施提供的能力将具有深远的实际技术重要性，导致材料开发的改进方法。

0959465KeltonWashington 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.