Colloids as Models for Crystals and Glasses

* 技术摘要 * 具有良好控制的尺寸和相互作用的胶体颗粒悬浮液将用于研究晶体和玻璃中的复杂结构、缺陷和转变。 使用共聚焦显微镜可以在空间和时间上高精度地跟踪这些粒子的运动。 这些粒子和单个原子之间的类比将使人们有可能在粒子/原子尺度上获得对复杂过程的独特视觉访问，例如过冷液体中晶核的形成，过热晶体中熔体的成核，位错与其他缺陷的相互作用，晶界的结构和运动，以及控制简单玻璃塑性流动的剪切转变区的性质和运动学。 这项工作旨在为材料的基础科学做出贡献，并将为该领域长期存在的“难题”提供新的动力，例如成核和玻璃科学。 这项工作是独特的跨学科，因为它结合了两个领域与自己独特的观点：在材料科学的专业知识补充，在胶体科学。 这项工作将提供一个非常丰富的学习环境，不仅为材料科学方面受过广泛训练的研究生，而且为本科甚至高中水平的研究项目提供学习环境。非技术摘要 * 原子尺度过程的物理建模在材料科学中有着悠久而古老的历史。 例如，在20世纪40年代，二维六边形肥皂泡筏的变形为位错在金属塑性变形中的作用提供了令人信服的证据。 我们现在可以在三维空间里做这件事。 共聚焦显微镜的出现使得在时间和空间上追踪悬浮液中的数十万个胶体颗粒成为可能。 通过将这些颗粒排列成类似于原子形成的晶体或玻璃结构，我们现在可以制作这些结构的形成或应变的“电影”，从而在原子/颗粒尺度上获得这些复杂过程的独特视图。 一个例子是在凝固过程中从液体中生长出小晶体，这似乎比迄今为止大多数理论所假设的球体的简单生长要复杂得多。 另一个例子是玻璃的变形，它具有非周期性结构，似乎是由大约100个原子的口袋重新排列而变形的;胶体技术将允许详细观察这些口袋的数量，大小和运动。 这两种现象-成核和玻璃科学-代表了材料科学中长期存在的“巨大挑战”，这种独特的跨学科方法应该提供新的见解和动力。 这项工作将为培养受过广泛教育的研究生提供一个非常丰富的学习环境。 与此同时，作品的直接、视觉性质使其非常容易为年轻学生所接受，甚至在高中阶段。

****TECHNICAL ABSTRACT****Suspensions of colloidal particles, with well-controlled size and interactions, will be used to study complex structures, defects and transformations in crystals and glasses. The motion of these particles can be tracked in space and time with high precision using confocal microscopy. The analogy between these particles and individual atoms will make it possible to obtain unique visual access at the particle/atomic scale to complex processes, such as the formation of crystal nuclei in a supercooled liquid, the nucleation of a melt in a superheated crystal, the interaction of dislocations with other defects, the structure and motion of grain boundaries, and the nature and kinematics of the shear transformation zones that govern plastic flow of simple glasses. This work aims to contribute to the fundamental science of materials and will give new impetus to long-standing "hard problems" in the field, such as nucleation and glass science. The work is uniquely interdisciplinary, in that it combines two areas with their own unique perspective: expertise in materials science complemented by that in colloid science. The work will provide a very rich learning environment, not only for broadly-trained graduate students in materials science, but also for research projects at the undergraduate or even high-school level.****NON-TECHNICAL ABSTRACT****Physical modeling of atomic-scale processes has a long and venerable history in materials science. In the 1940s, for example, the deformation of two-dimensional hexagonal raft of soap bubbles provided convincing evidence for the role of dislocations in plastic deformation of metals. We can now do this in three dimensions. The arrival of confocal microscopy has made it possible to track hundreds of thousands of colloidal particles in a suspension in time and space. By arranging this particles into crystalline or glassy structures, similar to those formed by atoms, we can now make "movies" of the formation or straining of these structures , and thereby obtain a unique view of these complex processes on the atomic/particle scale. An example is the growth of small crystal from a liquid during solidification, which appears to be much more complex than the simple growth of sphere that most theories have been assuming so far. Another example is the deformation of glasses, which have a non-periodic structure, and appear to deform by the rearrangement of pockets of about a hundred atoms; the colloid technique will allow a detailed look at the number, size and motion of these pockets. Both these phenomena -- nucleation and glass science -- represent long-standing "grand challenges" in materials science, to which this unique, interdisciplinary approach should provide new insights and impetus. This work will provide a very rich learning environment for the training of broadly educated graduate students. At the same time, the direct, visual nature of the work makes it highly accessible to younger students, even at the high-school level.