Fundamental In Situ Nano-Oxidation Mechanisms of Metals and Metallic Alloys

技术：表面氧化工艺在环境稳定性、高温腐蚀、电化学、催化反应、栅氧化物和薄膜生长以及燃料反应中起着关键作用。然而，目前，氧化的纳米级阶段--从金属氧化物的成核到热力学上稳定的氧化物的形成--代表着一个在科学上具有挑战性和在技术上具有重要意义的领域。其目的是通过协调实验(原位UHV-TEM)和理论努力从根本上了解纳米级氧化过程，其中影响可能是氧化的新范式。为了实现这一目标，将对铜和铜合金(铜-金和铜-镍)氧化的初始阶段进行直接相关的实验和理论研究。在过去，铜的初始阶段的原位实验都是用PI进行的。延伸到铜合金的氧化将在不同温度、压力和氧化气氛下的原位超高真空透射电子显微镜中进行，在杨的实验室中存在独特的原位超高真空透射电子显微镜。为了弥合模拟和实验之间的时间鸿沟，劳伦斯利弗莫尔国家实验室(LLNL)也将使用新开发的具有纳秒时间分辨率的动态瞬变电磁(DTEM)。用高分辨电子显微镜(HREM)、Z-衬度成像、层析成像和电子能量损失谱(EELS)等横截面和扫描电子显微镜(STEM)方法测定原位氧化形成的Cu/Cu2O界面结构，并与理论模拟进行比较，将对氧化转化机理提供重要的见解。样品制备和透射电子显微镜/STEM研究将在大学新的彼得森纳米科学与工程研究所(PINSE)进行。匹兹堡(UPitt)。原位和非原位的实验结果将直接与理论模型相关联，在理论模型中正在发展一种称为薄膜氧化(TFOx)的第一原理动力学蒙特卡罗。TFOx是目前模拟2D形核和生长的C++代码，将被开发来模拟3D岛的形成，其中将利用CMU和UF的计算机集群以及UPIT的超级计算机设施来显著提高模拟速度。这些模拟和现场实验之间的直接比较将带来新的知识。非技术性：UPIT、LLNL、UF和CMU之间的联合实验和理论合作将极大地丰富和拓宽参与该项目的所有研究生和本科生的教育。杨在为女学生提供咨询方面有着良好的记录。结果的传播将包括一个网址：www.tfox.org。杨将把她在薄膜、气体表面反应和电子显微镜方面的研究项目整合到机械工程和材料科学系(MEMS)的几个本科生和研究生课程中，例如本科生结晶学/衍射实验室和研究生纳米课程，如薄膜、纳米表征和电子显微镜以及纳米材料。

TECHNICAL: Surface oxidation processes play critical roles in environmental stability, high temperature corrosion, electrochemistry, catalytic reactions, gate oxides and thin film growth as well as fuel reactions. At present, however, the nanoscale stages of oxidation - from the nucleation of the metal oxide to the formation of the thermodynamically stable oxide - represent a scientifically challenging and technologically important terra incognito. The objective is to fundamentally understand nanoscale oxidation processes by coordinated experimental (in situ UHV-TEM) and theoretical efforts, where the impact is potentially a new paradigm for oxidation. To meet this objective, directly correlated experimental and theoretical investigations of the initial stages of Cu and Cu alloy (Cu-Au and Cu-Ni) oxidation will be performed. The in-situ experiments of the initial stages of Cu have been performed by PI in the past. The extension to Cu alloy oxidation will be conducted in an in situ UHV-TEM at various temperatures, pressures and oxidizing atmospheres in Yang's laboratory where a unique in--situ UHV TEM exists. To bridge the temporal gap between simulations and experiments, a newly developed dynamic TEM (DTEM) with nanoseconds time resolution, will be used as well at Lawrence Livermore National Lab (LLNL). Determination of the Cu/Cu2O interface structure formed by in-situ oxidation by cross-sectional TEM and scanning TEM (STEM) methods, including high-resolution electron microscopy (HREM), Z-contrast imaging, tomography and electron energy loss spectroscopy (EELS) and the comparison with theoretical simulations will provide critical insights into the oxidation transformation mechanisms. The sample preparation and TEM/STEM studies will be conducted in the new Peterson Institute of NanoScience and Engineering (PINSE) at Univ. of Pittsburgh (UPitt). The in-situ and ex-situ experimental TEM results will be directly correlated to theoretical models, where a first-principles kinetic Monte Carlo, called Thin Film Oxidation (TFOx) is being developed. TFOx is a C++ code that presently simulates 2D nucleation and growth, and will be developed to simulate 3D island formation where computer clusters at CMU and UF and the supercomputer facility at UPitt will be utilized for significantly enhanced simulation speed. The direct comparison between these simulations and in-situ experiments will lead to new knowledge. NON-TECHNICAL: The combined experimental with theoretical partnership between UPitt, LLNL,UF and CMU will significantly enrich and broaden the education of all of the graduate and undergraduate students involved in this program. Yang has a strong track record in advising women students. Dissemination of results will include a web-site: www.tfox.org. Yang will integrate her research program in thin films, gas surface reactions and electron microscopy into several of the Mechanical Engineering and Materials Science department (MEMS) undergraduate and graduate-level courses, such as undergraduate crystallography/diffraction laboratory and graduate nano-courses, such as thin films, nanocharacterization and electron microscopy as well as nanomaterials, at UPitt.