Probing Fluctuations and Nanoscale Dynamics in Glasses and Other Complex Materials

探测玻璃和其他复杂材料中的波动和纳米级动力学

• 批准号: 9877069
• 负责人: Nathan Israeloff
• 金额: --
• 依托单位: Northeastern University
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-08-01 至 2002-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9877069&HistoricalAwards=false
• 关键词: Probing; Fluctuations; Nanoscale; Dynamics; Glasses

9877069IsraeloffIn this research novel scanning probe microscopy (SPM) techniques will be used to measure the fluctuations in the dielectric and visco-elastic properties of organic glasses, polymers, and other materials as a function of frequency, time, field and position. The direct study of nano-scale fluctuations in glasses could provide a detailed picture of the dynamical processes leading to non-exponential relaxation, diverging relaxation times, and scaling at the glass transition. These investigations will address critical issues such as the length scale and nature of the molecular cooperativity, and the importance of heterogeneity and its time evolution. Statistical measures which characterize glassy cooperativity can be directly compared with those provided by simulations. Dielectric fluctuations will also be used to investigate predicted violations of the fluctuation-dissipation theorem (FDT) in macroscopic aging glasses. Although never observed in experiments, these non-equilibrium FDT violations may provide a means to probe the equilibrium glass order parameter, and are strongly model dependent. These researches address a fundamental unresolved issue in non-equilibrium statistical mechanics as well as test various glass transition models. Graduate students and postdocs participate in these investigations.%%% This research deals with fundamental problems of how liquids and polymers freeze into disordered solids, i.e., glasses. Though much work in the past has been done on these problems, present technology employing scanning probe microscopy now allow such studies to be performed on a near-atomic/molecular level. In this manner it was found that the physical properties of complex materials can vary dramatically when probed at near molecular length scales. This research stands at the forefront of one of the areas of contemporary condensed matter physics and is expected to make significant contributions to our understanding on the behavior of complex materials and thus to future technology. This research provides excellent opportunities for the training of graduate students and post doctoral research associates in an emerging area of condensed matter physics and materials science, and thereby contributes to the creation of an expert cadre of physicists and materials scientists for employment in the 21st Century. ***

9877069Israeloff 在这项研究中，新型扫描探针显微镜 (SPM) 技术将用于测量有机玻璃、聚合物和其他材料的介电和粘弹性特性随频率、时间、场和位置的变化。对玻璃纳米级波动的直接研究可以提供导致非指数弛豫、发散弛豫时间和玻璃化转变缩放的动态过程的详细图像。 这些研究将解决关键问题，例如分子协同性的长度尺度和性质，以及异质性及其时间演化的重要性。 表征玻璃协同性的统计测量可以直接与模拟提供的测量进行比较。 介电波动还将用于研究宏观老化玻璃中预测的波动耗散定理（FDT）违反情况。 尽管从未在实验中观察到，这些非平衡 FDT 违规可能提供一种探测平衡玻璃序参数的方法，并且强烈依赖于模型。 这些研究解决了非平衡统计力学中尚未解决的基本问题，并测试了各种玻璃化转变模型。 研究生和博士后参与了这些研究。%%% 这项研究涉及液体和聚合物如何冻结成无序固体（即玻璃）的基本问题。 尽管过去已经在这些问题上做了很多工作，但目前采用扫描探针显微镜的技术现在允许在近原子/分子水平上进行此类研究。 通过这种方式，人们发现，当在近分子长度尺度上进行探测时，复杂材料的物理性质可能会发生巨大变化。 这项研究处于当代凝聚态物理领域之一的前沿，预计将为我们对复杂材料行为的理解以及未来技术做出重大贡献。 这项研究为凝聚态物理和材料科学这一新兴领域的研究生和博士后研究员的培训提供了极好的机会，从而有助于培养21世纪就业的物理学家和材料科学家专家队伍。 ***