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

一个由爱荷华州立大学、华盛顿大学和马萨诸塞大学阿姆赫斯特分校的科学家和学生组成的团队将在爱荷华州立大学开发一个静电悬浮（ESL）设备，该设备将允许在高达3000K的温度下测量热物理特性（密度、表面张力、粘度和量热）以及磁化率和电阻（使用新型隧道二极管谐振器技术）。样品周围没有容器或气体流动，使得液体可以过冷，这一特征已经使金属和合金中液体和固相结构之间关系的新的高影响研究成为可能。在圣路易斯的华盛顿大学，将建造一个可携带的用于同步加速器x射线衍射测量的优化室。这两个互补的设施将允许研究平衡和亚稳液体的中短期秩序的发展与它们的热物理、电和磁性质的变化有关。爱荷华州立大学的设施将提供关于液-液相变、凝固过程中的相变动力学及其对材料加工的影响、经历结构和磁转变的系统的演化顺序、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，它们在组成和温度下的形成，以及它们在较低温度下形成或抑制稳定相中的作用的能力，将极大地增加我们对复杂系统中稳定相形成的理解。液体和眼镜每天都在我们身边，但在很多方面，我们对它们知之甚少。它们的原子结构、它们内部发生的相变以及它们的电学和磁性都不为人所知。例如，1721年华氏温度发现了一种趋势，即水会冷却到冰点以下（一种过冷的液体），从而阻止结晶阶段冰的形成。现在已知所有液体都可以过冷。然而，为什么会发生这种情况，以及在液体结晶之前的过冷状态下发生了什么变化，是目前人们感兴趣的问题。此外，玻璃化转变，即液体如何变成玻璃，具有重要的实际后果，已经被公认了数千年。例如，它允许硅酸盐玻璃被加工和吹成美丽而实用的复杂形状。像过冷一样，玻璃化转变无处不在，但其背后的原因仍然是凝聚态物质和材料物理学中的突出问题之一。爱荷华州立大学、华盛顿大学和马萨诸塞大学阿默斯特分校的一组科学家和学生将在爱荷华州立大学开发一种新型设备，用于测量熔化温度以上和以下液体的热物理性质，如密度、表面张力、粘度以及电和磁性质。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。与将在圣路易斯华盛顿大学建造的用于液体x射线研究的姊妹ESL室一起，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.