A Combinatorial Approach to Grain Boundary Studies: Bicrystal Arrays via Lithographically Modulated Seed Growth

非技术描述：在广泛的工程应用中，许多材料的性能受到定义其整体形状的外表面（固-气界面）、材料内部的固-气界面（内部空隙）以及当成分或原子结构/排列突然变化时产生的内部固-固界面（晶界）的影响。在纳米材料中，表面和界面的空间密度比传统材料高，因此它们起着更加关键的作用。表面和晶界的重要特征是它们的能量以及这些能量如何依赖于各自界面上原子的特定排列。在传统的模型实验中，只生成一个表面或晶界并对其进行检验。提出的工作将寻求开发一种新的灵活高效的实验工具，用于在受控化学的单个样品中产生大量非常特定几何形状的不同晶粒边界，这些边界与高度受控的表面相交。样品是专门设计的，以简化和大大加快测量的表面和晶界性质在广泛的材料。一种成功的制造方法的发展将促进表面和晶界特性知识的快速发展，这对设计具有改进性能特征的材料具有基本价值。这项工作将涉及研究生、本科生和高中阶段的学生，从而促进具有高级学位的训练有素的科学家的发展，并鼓励年轻的学生在这个令人兴奋和重要的领域继续深造和研究生水平的训练。技术描述：材料的表面（固-气界面）和晶界（固-固界面）是深刻影响材料性能的基本微观结构组成部分。在当前感兴趣的纳米结构材料中，这些界面的空间密度非常高，它们的重要性被放大了。生成、优化和稳定这种结构需要对表面和界面性质有基本的了解。晶界和表面能量学的测量是必要的，但困难而繁琐。在这项工作中，一种涉及选择性和局部阻碍单晶种子生长到牺牲多晶层的新方法将被探索和利用，以在单个样品中产生不同取向的双晶岛颗粒阵列。这些样品将为陶瓷的晶界和表面特性的系统（组合）研究提供理想的载体。对单个样品中可能存在的数百个晶界凹槽的几何测量，加上对相关表面取向的分析，提供了一种快速获得表面能取向关系的方法，并将这种结果与更繁琐的直接方法得出的结果进行比较。如果成功，这种方法将适用于所有材料类型，促进我们对表面结构（晶体学）-能量关系的知识的快速增长，并鼓励更多的扩展设计，以类似地影响晶界特性的研究。反过来，这些基本信息可以用来设计性能更好的材料。

NON-TECHNICAL DESCRIPTION: The performance of many materials in a wide range of engineering applications is influenced by the external surfaces (solid-vapor interfaces) that define their overall shape, solid-vapor interfaces within the material (internal voids), and by internal solid-solid interfaces (grain boundaries) that arise when the composition or the atomic structure/arrangement changes abruptly. In nanoscale materials, the spatial density of surfaces and interfaces is higher than in conventional materials, and therefore they play an even more critical role. Important characteristics of surfaces and grain boundaries are their energy and how these energies depend upon the specific arrangement of atoms at the respective interfaces. In conventional model experiments, one surface or grain boundary is generated and examined. The proposed work will seek to develop a new flexible and efficient experimental vehicle for generating large numbers of distinct grain boundaries of very specific geometry that intersect highly-controlled surfaces in a single sample of controlled chemistry. The samples are specifically designed to simplify and greatly accelerate measurements of surface and grain boundary properties in a wide range of materials. The development of a successful fabrication approach would promote rapid advances in the knowledge of surface and grain boundary properties that have fundamental value in designing materials with improved performance characteristics. This work will involve students at the graduate, undergraduate, and high-school levels, and thereby promote the development of trained scientists with advanced degrees, and encourage younger students to pursue further study and graduate-level training in this exciting and vital area.TECHNICAL DESCRIPTION: Surfaces (solid-vapor interfaces) and grain boundaries (solid-solid interfaces) in materials are essential microstructural components that profoundly impact properties and performance. In the nanostructured materials of current interest, the spatial density of these interfaces is extremely high, and their importance is amplified. Generating, optimizing and stabilizing such structures will require fundamental knowledge of the surface and interface properties. Measurements of grain boundary and surface energetics are essential, but difficult and tedious. In this work, a novel approach involving selectively and locally impeded single crystal seed growth into a sacrificial polycrystalline layer will be explored and exploited to generate arrays of bicrystal island grains of varying misorientation in a single sample. The samples will provide an ideal vehicle for systematic (combinatorial) studies of grain boundary and surface properties in ceramics. Measurements of the geometry of potentially hundreds of grain-boundary-grooves in a single sample, coupled with analysis of the relevant surface orientations provides a rapid method of obtaining the surface energy-orientation relationship, and comparisons will be made between such results and those derived from more tedious direct methods. If successful, such an approach would have applicability to the full range of material types, promote rapid gains in our knowledge of surface structure (crystallography)-energy relationships, and encourage additional extensions designed to similarly impact studies of grain boundary properties. In turn, this fundamental information can be used to design materials with improved performance.