• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Nano-scale characterization of oxide materials by atomic resolution Z-contrast imaging and eels.
【24h】

Nano-scale characterization of oxide materials by atomic resolution Z-contrast imaging and eels.

机译：通过原子分辨率Z对比成像和鳗鱼对氧化物材料进行纳米级表征。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

In this thesis, novel techniques have been developed in scanning transmission electron microscopy that can be used to analyze the atomic scale structure-property relationships in oxides, both at room and elevated temperatures. In particular, by using correlated Z-contrast imaging and electron energy loss spectroscopy, the structure, composition and bonding can all be characterized directly. In this thesis, it will be demonstrated that these techniques can be used to analyze a wide range of materials, and examples from dielectrics, electronic- and ionic conductors and catalysts will be shown. The majority of this thesis will address the atomic scale characterization of oxygen vacancy structures and point defect diffusion in ionic and electronic conducting ceramic membranes and at grain boundaries in model perovskite oxides. It is found that at high oxygen vacancy concentration the individual vacancies start to interact and associate to form arbitrarily oriented domains of Brownmillerite structures inside the bulk material. These domains continuously grow with increasing reducing conditions and ultimately, the structure collapses due to the high oxygen deficiency. Throughout the reduction, adjacent atomic planes exhibit a drastic difference in the oxygen vacancy formation energy, which causes a selective reduction of bulk. Further, oxygen vacancy and acceptor segregation towards the homo-interfaces was observed, that appears to be responsible for the formation of the widely observed grain boundary potential. This potential can be explained by the inherently larger oxygen vacancy segregation energy of the interfacial structural units rather than the phenomenological Schottky-barrier picture. At the metal-oxide interfaces in model catalysts, metal surface oxidation layers at higher calcination temperatures and reduction of the oxide support at the hetero-interfaces at lower calcination temperature was found. The effects of this oxygen vacancy segregation and surface oxidation on the catalysts performance will be the aim of future experiments.
机译：在这篇论文中，已经开发了扫描透射电子显微镜中的新技术，该技术可用于分析在室温和高温下氧化物的原子尺度结构-性质关系。特别地，通过使用相关的Z-对比度成像和电子能量损失谱，可以直接表征结构，组成和键合。在本文中，将证明这些技术可用于分析各种材料，并显示了电介质，电子和离子导体以及催化剂的实例。本论文的大部分内容将讨论氧空位结构的原子尺度表征以及离子和电子导电陶瓷膜中以及钙钛矿型氧化物模型中晶界处的点缺陷扩散。发现在高氧空位浓度下，各个空位开始相互作用并缔合，从而在块状材料内部形成了布朗米尔结构的任意取向的畴。这些结构域随着还原条件的增加而持续增长，最终由于高氧缺乏而导致结构崩溃。在整个还原过程中，相邻的原子平面在氧空位形成能上表现出极大的差异，这导致了体积的选择性减小。此外，观察到氧空位和受体向均质界面的偏析，这似乎是导致广泛观察到的晶界电势形成的原因。这种潜力可以用界面结构单元固有的更大的氧空位偏析能来解释，而不是用现象学上的肖特基势垒图来解释。在模型催化剂的金属-氧化物界面处，发现在较高煅烧温度下的金属表面氧化层和在较低煅烧温度下的异质界面处的氧化物载体的还原。这种氧空位偏析和表面氧化对催化剂性能的影响将是未来实验的目的。

著录项

  • 作者

    Klie, Robert F.;

  • 作者单位

    University of Illinois at Chicago.;

  • 授予单位 University of Illinois at Chicago.;
  • 学科 Physics Condensed Matter.; Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 194 p.
  • 总页数 194
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号