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

9317680巴布科克这项研究计划探索晶界偏析元素影响金属和氧化物中晶界原子结构的方式。表征技术包括高分辨率、相衬电子显微镜成像、高分辨率Z-衬度扫描电子显微镜成像、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)平行于晶界和垂直于晶界的偏析溶质的原子尺度分布，以及(B)偏析溶质对宿主晶界原子堆积单元的影响。这些研究是在控制晶界结晶学、控制掺杂和简单但具有代表性的几何结构的双晶样品上进行的。我们选择了掺铅的氧化镍和掺金的铁作为初步实验。这两个合金系统是模型材料，其行为代表了广泛的化合物和合金的行为。实验结果将与现有的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个基本的结构机制，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广泛的晶界以及工程材料中的块体性质的机制是基本的。***

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. ***