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

技术摘要由爱荷华州州立大学、华盛顿大学和马萨诸塞州大学阿默斯特分校的科学家和学生组成的一个小组将在爱荷华州州立大学开发一种静电悬浮（ESL）装置，用于测量热物理性质（密度，表面张力，粘度和量热法）以及磁化率和电阻（使用新型隧道二极管谐振器技术）在高达3000 K的温度下。 样品周围没有容器或气流，使液体能够过冷，这一特征已经使金属和合金中液相和固相结构之间关系的新的高影响力研究成为可能。 位于圣路易斯的华盛顿大学将建造一个最适合同步加速器X射线衍射测量的便携式室。 这两个互补的设施将允许在平衡和亚稳液体中的短程和中程秩序的发展的研究与它们的热物理，电和磁特性的变化相关。爱荷华州的设施将提供有关液-液相变、凝固过程中的相变动力学及其对材料加工的影响、经历结构和磁性转变的系统中的演变顺序、亚稳相的检测和表征以及磁场对凝固过程的影响的新信息。 原位测定这些亚稳相的结构和性质、它们随组成和温度的形成以及它们在低温下稳定相的形成或抑制中的作用的能力，将极大地增加我们对复杂系统中稳定相形成的理解。 它们的原子结构、它们内部发生的相变以及它们的电和磁特性都不为人所知。 例如，在1721年，华氏发现了一种倾向，即水冷却到冰点以下（过冷液体），以抵抗结晶相冰的形成。 现在已经知道过冷在所有的液体中都是可能的。 然而，为什么会发生这种情况，以及在结晶之前，液体的过冷状态发生了什么变化，是目前感兴趣的问题。 此外，玻璃化转变，即液体如何变成玻璃，具有数千年来已被认识到的重要实际后果。 例如，它可以将硅酸盐玻璃加工和吹制成美丽而实用的复杂形状。 像过冷一样，玻璃化转变是普遍存在的，但它的基础仍然是凝聚态和材料物理学中的突出问题之一。 一个由爱荷华州州立大学、华盛顿大学和马萨诸塞州大学阿默斯特分校的科学家和学生组成的团队将在爱荷华州州立大学开发一种新的设备，该设备将能够测量高于和低于熔化温度的液体的热物理特性，如密度、表面张力、粘度以及电和磁特性。 为了避免测量过程中的污染，液体将在电场中悬浮（静电悬浮，ESL）并在真空中加热。 与姐妹ESL室一起，设计用于液体的X射线研究，将在圣路易斯的华盛顿大学建造，它们将能够将原子结构和物理性质的测量相关联，这将极大地增加我们对这些复杂系统的理解。

Technical AbstractA 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 AbstractLiquid 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.