Spatial and Temporal Fluctuations in Coherent Electron Nanodiffraction from Metallic Glasses and Glass-forming Liquids

金属玻璃和玻璃形成液体的相干电子纳米衍射的空间和时间波动

• 批准号: 1205899
• 负责人: Paul Voyles
• 金额: $ 41.15万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-10-01 至 2015-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1205899&HistoricalAwards=false
• 关键词: Spatial; Temporal; Fluctuations; Coherent; Electron

TECHNICAL SUMMARYThis project supports investigation of the structure and atomic dynamics of metallic glasses and metallic-glass forming liquids using systematic coherent electron nanodiffraction in a scanning transmission electron microscope, in a technique called fluctuation electron microscopy. Time-resolved nanodiffraction experiments as a function of temperature will test the hypothesis that metallic glass forming liquids exhibit spatial heterogeneous dynamics which play an essential role in their glass transition. If spatial domains with different dynamics are found, their relaxation time and their internal structure will be determined experimentally. These potentially transformative experiments will be the first direct, structural probe of the existence, relaxation, and structure of spatially heterogeneous dynamics at the nanometer scale. This project will also support investigation of the room-temperature structure of a metallic glass of 75 at.% Ce and 25 at.% Al. This glass has a novel metastable high-pressure crystalline phase, which has been proposed to arise from long-range topological order quenched into the glassy state. Conventional TEM will be used to investigate the structure and defects of the high-pressure phase, and spatially-resolved nanodiffraction will be used to investigate the structure of the glassy phase.The project will support education and outreach about advanced characterization methods in STEM. The Electron Microscopy Database, an online collection of example data sets for teaching and learning advanced STEM techniques, will be enlarged, and the underlying database technology will be modernized. The researchers involved in this project will conduct public lectures and demonstrations of atomic-resolution STEM imaging and microanalysis using the remote operation capabilities of the STEM used for this project's research.NON-TECHNICAL SUMMARYGlasses are materials in which the atoms are jumbled up, in contrast to crystals, in which the atoms sit on a grid. Most metal alloys exist only as crystals, but a few special ones can be forced to make a glass by cooling them very quickly from their liquid, melted state. This project will investigate those special liquids and the metallic glasses they form to measure how the atoms fit together and how they move around with respect to one another. In both cases, it is clumps of 10-100 atoms which have the most important structure, which corresponds to a size of about 1 nanometer. The researchers supported by this project will make their measurements using an advanced electron microscope with a beam of electrons one nanometer in diameter - just matched to the size of the interesting clumps of atoms. Their discoveries will help scientists understand why some metal alloys form glasses and others do not, and may lead to the development of new metallic glasses with superior strength, ductility, or other properties.This project will also support education and outreach in advanced electron microscopy techniques required for the nation's burgeoning nanotechnology workforce. The researchers will maintain and enlarge the Electron Microscopy Database, an online collection of examples for teaching and learning. They will also do public demonstrations of advanced electron microscopy, including the ability to see single atoms, one at a time, in an effort share with young people their interest and excitement about science.

技术摘要这项项目支持研究金属玻璃和金属玻璃的结构和原子动力学，并在一种称为波动电子显微镜的技术中使用系统的相干电子纳米施加来形成液体。 时间分辨的纳米施法实验随温度的函数，将检验以下假设：金属玻璃形成液体表现出空间异质动力学，这些动力学在其玻璃转变中起着至关重要的作用。 如果发现具有不同动力学的空间结构域，则将通过实验确定其放松时间及其内部结构。 这些潜在的变换实验将是对纳米尺度上空间异质动力学的存在，松弛和结构的第一个直接的结构探测。 该项目还将支持对75个金属玻璃的室温结构。 该玻璃具有一种新型的亚稳态高压晶相，该玻璃已提出是由延入玻璃状态的远程拓扑顺序产生的。 常规TEM将用于研究高压阶段的结构和缺陷，并将使用空间分辨的纳米式曲线来研究玻璃阶段的结构。该项目将支持有关STEM中先进特征方法的教育和外展。 电子显微镜数据库将扩大用于教学和学习高级STEM技术的示例数据集的在线集合，并且将现代化基础数据库技术。 参与该项目的研究人员将使用用于该项目研究的STEM的远程操作能力进行原子分辨率的STEM成像和微分析的演示。没有技术摘要是原子与晶体相反的材料，在该材料中，原子位于网格上。 大多数金属合金仅作为晶体存在，但是一些特殊的合金可以通过从液体融化状态下快速冷却来制作玻璃。 该项目将调查它们形成的那些特殊液体和金属玻璃，以测量原子如何融合在一起以及它们如何相互移动。 在这两种情况下，它具有最重要的结构的10-100个原子的团块，对应于约1纳米的大小。 该项目支持的研究人员将使用高级电子显微镜进行测量，并具有直径为单位的电子束 - 仅与有趣的原子团的大小相匹配。 他们的发现将有助于科学家了解为什么某些金属合金形成眼镜，而另一些金属合金则不会，并且可能导致具有优势强度，延展性或其他特性的新金属眼镜的开发。该项目还将支持该国蓬勃发展的纳米技术工作所需的高级电子显微镜技术的教育和外展。 研究人员将维护和扩大电子显微镜数据库，这是一个在线教学示例的集合。 他们还将对高级电子显微镜进行公开演示，包括一次看到单个原子的能力，一次与年轻人分享他们对科学的兴趣和兴奋。