Probing Nanoscale Oxidation Mechanism of Metals under Applied Stress

该计划旨在通过在专门的原位环境TEM中耦合机械负载和气体表面反应来探测金属在施加应力下的纳米氧化特性，同时监测氧化过程中的结构和化学变化。该方案将审查：1）施加应力对氧化物岛的成核和生长的影响; 2）施加应力与氧化物岛的纳米级形态之间的相关性;以及3）施加应力对氧化物岛的聚结行为的影响。研究结果将为考虑环境影响构建原子氧化模型提供基础，环境影响不再仅由大气描述，而是由工程部件可能经历的各种约束（例如机械和热）描述。除了解决这些科学问题外，随着工程系统的尺寸不断缩小到纳米级，该研究也将具有重要的实际意义。由于该项目解决了有助于理解表面结构，反应性，质量传输和表面形态与施加应力的纳米级相关性的基本问题，这些研究将广泛影响许多领域，包括高温氧化，腐蚀，电化学、薄膜处理、多相催化和燃料电池，其中也出现基本过程的原型。作为该研究计划的一部分，研究生和本科生将参与学习最先进的电子显微镜技术和材料问题，这些技术和材料问题处于当前材料研究的最前沿。该项目将涉及与其他机构和行业的科学家的广泛合作，这将为学生提供看到各种研究环境的绝佳机会，并帮助他们发现未来在行业或学术界的职业机会。

This program is to probe nanoscale oxidation properties of metals under applied stresses by coupling mechanical loading and gas-surface reactions within a specialized in situ environmental TEM, while simultaneously monitoring the structural and chemical changes during the oxidation. This program will examine: 1) effect of applied stress on nucleation and growth of oxide islands; 2) correlations between applied stress and nanoscale morphologies of oxide islands; and 3) effect of applied stress on the coalescence behavior of oxide islands. The outcome of the study will provide the foundation for constructing atomistic oxidation models by taking into account environment effects, which are no longer described by the atmosphere only, but by all kinds of constraints (e.g. mechanical and thermal) an engineering component may undergo. In addition to addressing these scientific issues, the study will also have significant practical implications as dimensions of engineered systems continue to shrink to nanoscale.Because the project addresses fundamental issues that help understand nanoscale correlations of surface structure, reactivity, mass transport, and surface morphology with applied stresses, these studies will broadly impact on many fields including high temperature oxidation, corrosion, electrochemistry, thin film processing, heterogeneous catalysis, and fuel cells, where the prototypes of basic processes also occur. As part of this research program, students at the graduate and undergraduate levels will be involved in learning about state-of-the-art electron microscopy techniques and materials issues that are at the forefront of current materials research. This project will involve broad collaborations with scientists at other institutions and in industry, which will provide students outstanding opportunities to see a variety of research environments and help them discover future career opportunities in industry or academia.