Understanding Surface Reactivity of Bimetallic Alloys

在涉及金属的应用中，腐蚀是一个关键问题，例如核反应堆容器、管道、船体、喷气发动机涡轮叶片、生物金属植入物和桥梁。腐蚀科学中的一个长期挑战是需要根据特定合金或涂层的成分和暴露条件准确地预测其退化。保护性氧化膜的形成是金属获得耐腐蚀性的一种常见机制，但这些氧化膜的形成机理还不是很清楚。化学、表面条件和材料敏感性等因素控制着氧化行为，但经典的氧化模型无法预测给定的合金成分是否能为特定的使用环境形成连续的保护层。造成这一认识差距的一个主要原因是缺乏能够观察氧化最早阶段的实验工具。该奖项支持开发实用的预测模型所需的原子和纳米级合金氧化过程的基础研究。这一科学理解将加快与许多需要在高温下持续耐腐蚀的技术领域相关的材料创新，包括发电、材料加工和化学转化过程。这项研究计划将通过开发新材料和技术来提高国家经济竞争力，并通过对研究生和博士后的培训和指导、跨学科课程以及强调女性和代表性较低的少数民族的参与来促进具有竞争力的STEM劳动力的发展。在腐蚀过程中导致保护性氧化膜建立的进化过程至关重要，但取决于许多内在和外在变量，包括温度、总压力、反应物种的性质和丰度、结构和化学因素、竞争成核和界面现象。这项研究将系统地评估这些变量之间的关系，以详细了解在恶劣环境中，包括高温和多种氧化气体环境中保护性结垢的形成。金属氧化物的成核和生长将利用原位环境透射电子显微镜在原子水平上进行可视化。最终形成的鳞片的生长动力学和结构将使用热重分析和各种电子显微镜技术进行表征。这些关键的实验工作，通过补充的理论计算，将阐明在与服务相关的环境中影响保护性氧化膜形成的反应路径的原子起源和关键参数。这种原位和非原位表征的组合跨越了从初始阶段的氧化到热力学稳定氧化物的发展的大的时间和空间尺度范围。开发的方法学所产生的知识将在这一重要的气固表面反应领域产生新的范例。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Corrosion is a crucial concern in applications involving metals, such as nuclear reactor vessels, pipelines, ship hulls, jet engine turbines blades, bio-metallic implants, and bridges. A longstanding challenge in corrosion science is the need to predict accurately the degradation of a given alloy or coating based on its composition and the exposure conditions. The formation of a protective oxide scale layer is a common mechanism by which metals achieve corrosion resistance, but the formation of these scales is not well understood. Factors such as chemistry, surface conditions, and material sensitivity control oxidation behavior, but classical oxidation models lack the ability to predict whether a given alloy composition can form a continuous protective scale for a specific service environment. A primary reason for this gap in knowledge is the lack of experimental tools capable of observing the earliest stages of oxidation. This award supports the fundamental research into the atomic- and nano-scale process of alloy oxidation needed to develop practical, predictive models. The scientific understanding will accelerate materials innovations relevant to many technological areas that require sustained corrosion resistance at elevated temperatures, including energy generation, materials processing, and chemical conversion processes. This research program will contribute to national economic competitiveness through the development of novel materials and technologies, and to the development of a competitive STEM workforce through training and mentorship of graduate students and postdocs, interdisciplinary courses, and an emphasis on the participation of women and underrepresented minorities.The evolutionary processes leading to the establishment of protective oxide scales during corrosion are critically important but depend on many intrinsic and extrinsic variables, including temperature, total pressure, nature and abundance of the reacting species, structural and chemical factors, and competitive nucleation and interfacial phenomena. This research will systematically assess the relationships among these variables to develop a detailed understanding of the establishment of protective scale formation in harsh environments including environments of high temperature and multiple oxidizing gases. The metal oxide nucleation and growth will be visualized at the atomic level using in situ environmental transmission electron microscopy. The growth kinetics and structure of the scales that eventually form will be characterized using thermal gravimetric analysis and a variety of electron microscopy techniques. These key experimental efforts, enhanced by complementary theoretical calculations, will explicate the atomic origins and critical parameters affecting the reaction pathways of protective oxide-scale formation in service-relevant environments. This combination of in situ and ex situ characterizations bridges large temporal- and spatial-scale ranges, from initial-stage oxidation to the development of the thermodynamically stable oxide. The knowledge resulting from the methodologies developed will lead to new paradigms in this important field of gas-solid surface reactions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.