Investigations of Deeply Undercooled Liquids and High Temperature Phase Formation using Electrostatic Levitation and Contactless Measurement Techniques.

*技术摘要*爱荷华州立大学的一组科学家和学生将利用新建的静电悬浮(ISU-ESL)设备研究深度过冷液体和亚稳定结晶相的结构、电子和磁性。可以在高达2500 K的温度下测量热物理性质(密度、表面张力、粘度和热量计)以及磁化率和电阻(使用新型隧道二极管谐振器技术)。这些性质测量将与在高级光子源和散裂中子源使用专门为散射测量而设计的ESL室进行的微观结构性质的X射线和中子散射测量相关联。这些设备的协同使用将提供有关液-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的演化顺序、亚稳态相的检测和表征以及磁场对凝固过程的影响的新信息。非技术摘要*液体和玻璃每天都在我们身边，但在许多方面人们对它们知之甚少。无论是它们的原子结构，它们内部发生的相变，还是它们的电学和磁学性质，都不是很清楚。例如，1721年华氏发现了一种将水冷却到冰点以下(一种过冷的液体)的趋势，以阻止结晶相冰的形成。现在已知在所有液体中过冷都是可能的。然而，为什么会发生这种情况，以及在液体结晶之前，液体的过冷状态会发生什么变化，都是目前感兴趣的问题。当一些液体凝固时，它们会形成只在高温下存在的亚稳相。这些亚稳态相的性质相对来说仍未被探索，它们可以强烈地影响最终产品的具体路径。一个由科学家和学生组成的团队将使用爱荷华州立大学最近投入使用的一种新型设备，该设备可以测量液体的密度、表面张力、粘度以及高于和低于其熔化温度和高温亚稳固体相的电学和磁学性质。为了避免测量过程中的污染，液体被悬浮在电场中(静电悬浮，ESL)并在真空中加热。与高级光子源(阿贡国家实验室)的姊妹ESL设施(专为液体的X射线研究而设计)以及散裂中子源(橡树岭国家实验室)的中子散射调查一起，它们将能够将原子结构和物理性质的测量结果关联起来，这将极大地增加我们对高温下复杂系统的理解。

****Technical Abstract****A team of scientists and students at Iowa State University will study the structural, electronic, and magnetic properties of deeply undercooled liquids and metastable crystalline phases using a newly constructed Electrostatic Levitation (ISU-ESL) facility. 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) can be done at temperatures up to 2500 K. These property measurements will be correlated with x-ray and neutron scattering measurements of microscopic structural properties performed at the Advanced Photon Source and Spallation Neutron Source using ESL chambers specifically designed for scattering measurements. The coordinated use of these facilities 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.****Non-Technical Abstract****Liquid 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. As some liquids solidify, they can form metastable phases that exist only at high temperature. The properties of these metastable phases remain relatively unexplored, and they can strongly influence the specific path to the final product. A team of scientists and students will use a novel facility recently commissioned at Iowa State University that enables 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 and high temperature metastable solid phases. To avoid contamination during the measurements, the liquids are levitated in an electric field (electrostatic levitation, ESL) and heated in vacuum. Taken together with a sister ESL facilities at the Advanced Photon Source (Argonne National Laboratory), designed for x-ray studies of liquids, and neutron scattering investigations at the Spallation Neutron Source (Oak Ridge National Laboratory), they will be able to correlate measurements of atomic structure and physical properties, which will add tremendously to our understanding of complex systems at high temperatures.