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)、材料内的固-气界面(内部空隙)以及当组成或原子结构/排列突然变化时出现的内部固-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更高，因此它们发挥着更关键的作用。表面和晶界的重要特征是它们的能量，以及这些能量如何取决于原子在各自界面上的具体排列。在传统的模型实验中，只产生并检验一个表面或晶界。拟议的工作将寻求开发一种新的灵活而高效的实验工具，用于生成大量非常特定几何形状的不同晶界，这些晶界在单个受控化学样本中与高度受控的表面相交。这些样品专为简化和大大加快各种材料的表面和晶界特性的测量而设计。一种成功的制备方法的发展将促进表面和晶界性质知识的快速发展，这些性质在设计具有改进性能特性的材料方面具有基础价值。这项工作将涉及研究生、本科和高中水平的学生，从而促进训练有素的高级学位科学家的发展，并鼓励年轻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培训。技术描述：材料中的表面(固-蒸气界面)和晶界(固-固界面)是深刻影响性能和性能的基本微观结构组件。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，其重要性被放大。生成、优化和稳定这种结构将需要表面和界面属性的基本知识。晶界和表面能量学的测量是必要的，但困难和繁琐。在这项工作中，将探索一种新的方法，将选择性和局部受阻的单晶种子生长到牺牲多晶层中，并在单个样品中产生不同取向不同的双晶岛状颗粒阵列。这些样品将为系统(组合)研究陶瓷中的晶界和表面性质提供理想的工具。测量单个样品中可能有数百个晶界沟槽的几何形状，再加上分析相关的表面取向，提供了一种快速获得表面能量-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(结晶学)-能量关系的知识的快速增长，并鼓励旨在类似影响晶界性质研究的额外扩展。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.