An Atomic-Resolution Evaluation of the Mechanism by which Segregated Solute Influences Grain Boundary Structures

小行星9317680 本研究计划探讨晶界偏析元素影响金属和氧化物晶界原子结构的方式。 表征技术包括高分辨率、相衬透射电子显微镜（TEM）成像、高分辨率Z衬度扫描TEM成像、高空间分辨率X射线和电子能量损失谱以及高速位置敏感原子探针显微镜，以确定： (a)平行和垂直于晶界的偏析溶质的原子尺度分布，以及（B）偏析溶质对主晶界的原子堆积单元的影响。 这些研究是在受控晶界晶体学、受控掺杂和简单但具有代表性的几何形状的双晶样品上进行的。 铅掺杂的氧化镍和金掺杂的铁已被选择用于初始实验。 这两种合金系统是模型材料，其行为代表了广泛的化合物和合金。 实验结果将与当代晶界结构模型进行比较。 这些分析的主旨是确定是否存在一种基本的结构机制，通过这种机制，偏析原子影响晶界性质。 这些知识对于理解晶界偏析溶质控制宽范围晶界的机制以及工程材料中的本体性质是至关重要的。 ***

9317680 Babcock This research program explores the ways in which grain boundary segregated elements affect the atomic structure of grain boundaries in metals and oxides. Characterization techniques include high resolution, phase-contrast transmission electron microscopy (TEM) imaging, high resolution Z-contrast scanning TEM imaging, high spatial resolution x-ray and electron energy loss spectroscopy, and high speed position-sensitive atom probe microscopy to determine: (a) the atomic-scale distribution of the segregated solute both parallel and perpendicular to the grain boundary, and (b) the influence of the segregated solute on the atomic packing units of the host grain boundary. These studies are conducted on bicrystalline samples of controlled grain boundary crystallography, controlled doping, and simple, but representative, geometry. Lead- doped nickel oxide and gold-doped iron have been chosen for the initial experiments. These two alloy systems are model materials whose behavior represent that of a broad range of compounds and alloys. The experimental results will be compared with contemporary models for grain boundary structure. The thrust of these analyses is to determine whether or not a fundamental structural mechanism exists by which segregated atoms influence grain boundary properties. %%% Such knowledge is fundamental to understanding the mechanisms by which grain boundary segregated solutes control a broad range of grain boundary and, therefore, bulk properties in engineering materials. ***