Phase Transformations in Crystalline Ceramic Oxides

这笔赠款是对dmr-8521834的续展奖项，该奖项卓有成效：开发了新的分析技术，以研究近原子分辨率下两种不同氧化物陶瓷之间的基本相变和化学反应，开发了使用卢瑟福背散射光谱来确定这些体系中的反应动力学，并证实了在这些材料中，拓扑和外延生长一次发生在几个单位细胞的层中，而不是像以前认为的那样，一次只生长一个原子层。这项工作的重点是利用这些新的分析技术来了解相界面的结构和化学对不同晶体结构的两种氧化物之间界面运动的影响。正在使用的分析技术包括：将使用透射式电子显微镜的所有方面(例如，化学分析、原子晶格成像)。会聚束电子衍射)、电子探针、可见光显微镜、卢瑟福背散射光谱和X射线衍射。感兴趣的材料包括：镍铝尖晶石、镁铝尖晶石、镁铬氧化铝尖晶石和铁铝尖晶石。这项研究有两个主要目标：界面的几何形状，以及了解界面的形态和化学如何影响界面发展的动力学。

This grant is a renewal award for DMR-8521834, which was highly productive: development of new analytical techniques to study the fundamental phase transformations and chemical reactions between two different oxide ceramics at near atomic resolution, development of the use of Rutherford backscattering spectroscopy to determine the kinetics of reactions in these systems, and confirmation that topotaxial and epitaxial growth in these materials occurs in layers of several unit cells at a time rather than one atomic layer at a time, as previously believed. The emphasis of this work is to use these new analytical techniques to understand the effect of the structure and chemistry at the phase boundary upon the movement of the interface between two oxides of different crystal structure. Analytical techniques being used include: all aspects of transmission electron microscopy will be used (e.g., chemical analysis, atomic lattice imaging. converging beam electron diffraction), electron microprobe, visible light microscopy, Rutherford backscattering spectroscopy, and x-ray diffraction. Materials if interest include: nickel-aluminum oxide spinels, magnesium-aluminum oxide spinels, magnesium-chromium-aluminum oxide speinels, and iron-aluminum oxide spinels. The research has two main objectives: geometry of the interface, and to understand how the morphology and the chemistry of the interface affect the kinetics with which the interface develops.