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Visualizing dislocation nucleation by indenting colloidal crystals.

机译：通过缩进胶体晶体可视化位错成核。

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摘要

The formation of dislocations is central to our understanding of yield, work hardening, fracture, and fatigue of crystalline materials. While dislocations have been studied extensively in conventional materials, recent results have shown that colloidal crystals offer a potential model system for visualizing their structure and dynamics directly in real space. Although thermal fluctuations are thought to play a critical role in the nucleation of these defects, it is difficult to observe them directly. Nano-indentation, during which a small tip deforms a crystalline film, is a common tool for introducing dislocations into a small volume that is initially defect-free. Here, we show that an analogue of nano-indentation performed on a colloidal crystal provides direct images of defect formation in real time and on the single particle level, allowing us to probe the effects of thermal fluctuations. We implement a new method to determine the strain tensor of a distorted crystal lattice and we measure the critical dislocation loop size and the rate of dislocation nucleation directly. Using continuum models, we elucidate the relation between thermal fluctuations and the applied strain that governs defect nucleation. Moreover, we estimate that although bond energies between particles are about fifty times larger in atomic systems, the difference in attempt frequencies makes the effects of thermal fluctuations remarkably similar, so that our results are also relevant for atomic crystals.
机译：位错的形成是我们了解晶体材料的屈服，加工硬化，断裂和疲劳的关键。虽然对位错已在常规材料中进行了广泛的研究，但最近的结果表明，胶体晶体提供了一种潜在的模型系统，可直接在真实空间中可视化其结构和动力学。尽管人们认为热波动在这些缺陷的形核中起着关键作用，但很难直接观察到它们。纳米压痕是一种用于将位错引入到最初没有缺陷的小体积中的常用工具，在该过程中，小尖端会使晶体膜变形。在这里，我们证明了在胶体晶体上进行纳米压痕的类似物可以实时实时地在单个颗粒水平上提供缺陷形成的直接图像，从而使我们能够探究热涨落的影响。我们实施一种新方法来确定扭曲晶格的应变张量，并直接测量临界位错环的大小和位错成核的速率。使用连续体模型，我们阐明了热涨落与控制缺陷成核的外加应变之间的关系。此外，我们估计尽管在原子系统中粒子之间的键能大约大50倍，但尝试频率的差异使热涨落的影响非常相似，因此我们的结果也与原子晶体有关。

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  • 来源
    《Nature》 |2006年第7082期|P.319-323|共5页
  • 作者

    Schall P; Cohen I; Weitz DA; Spaepen F;

  • 作者单位

    Division of Engineering and Applied Sciences, Harvard University, 9 Oxford Street, Cambridge, Massachusetts 02138, USA. pschall@science.uva.nl;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 基础医学;
  • 关键词

    Atom; SIZES; allowing; structure; particle;

    机译：原子;尺寸;允许;结构;颗粒;

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