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：该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。一个由来自圣路易斯华盛顿大学、艾姆斯爱荷华州立大学、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中子散射研究的新型设备（NESL，中子静电悬浮）。液体将在高真空中使用静电悬浮，从而避免容器污染。液体和玻璃可能是最不为人所知的物质相，关于它们的物理性质和原子结构还有许多悬而未决的问题。对于它们是如何结晶的，在某些情况下，是如何通过冷却变成玻璃的，我们还不完全了解。此外，在低于其熔化温度（过冷）的温度下，液体中的新相行为和相变在很大程度上未被探索。由于大多数元素只有在高温下才会变成液体，并与容器材料发生强烈反应，因此对其结构和性质的实验研究很难或不可能完成。NESL将允许高温液体的结构和动力学研究，无论是高于还是低于其平衡熔化温度。NESL将针对弹性和非弹性中子散射研究进行优化，并用于最近完成的SNS，这是世界上最强烈的脉冲加速器中子源。NESL将对基础和基础研究产生巨大影响，并将作为扩大国家和国际合作的催化剂。它将允许发展中短期秩序和液体动力学的开创性研究，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的专业ESL实验室相结合时，NESL将为样品温度高达3000K的固体，液体和亚稳相的协调结构和性质研究创造一个独特的机会。摘要：本奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。几千年来，人们一直在研究液体和玻璃，但它们可能是最不为人所知的物质状态。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和它们改变到其他状态的能力。例如，1721年，华氏发现，在适当的条件下，液体可以保持在低于其熔化温度的温度下而不结晶（结晶的一个常见例子是液态水变成冰）。令人惊讶的是，近300年过去了，我们仍然不完全了解这种形成晶体相的阻力的起源，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。除了像结晶这样的不连续的转变，如果它们冷却得足够快，液体也可以通过连续的过程凝固成玻璃，其中的原子被冻结成液体的结构。几个世纪以来，玻璃吹制工经常使用冷却玻璃过渡的技术来制作复杂而美丽的玻璃制品，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未解决问题。液体的中子散射研究提供了一种独特的方法来解开这些和相关的问题。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，与容器接触会引起结晶。在成功开发液体x射线散射研究技术的基础上，圣路易斯华盛顿大学、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）的科学家团队将开发一种世界上独一无二的设备，用于悬浮液体的中子散射研究，从而避免了对容器的需要。除了对基本理解的重要性之外，该设施提供的能力将具有深远的实际技术重要性，从而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.