Structure and Interface Evolution in Self-Lubricating Coatings and Nanocomposites for Moving Mechanical Assemblies

移动机械组件（MMA），如微型滚动元件轴承，齿轮和其他精密部件，必须在设备运行中可靠和可预测地运行。MMA产品的进步要求减小这些设备的尺寸，从而增加了动态摩擦学表面相互作用对性能和可靠性的影响。目前，埋藏表面/界面上涂层的纳米尺度一致性和均匀性、全组装MMA涂层合成新途径的应用、剪切载荷下复杂涂层微结构和摩擦化学修饰界面的精确表征以及关键摩擦学表面涂层的选择性沉积等方面都存在一些不足和挑战。UNT和铁姆肯公司提出了一个双重研究策略来解决这些问题。首先，将开发利用原子层沉积（ALD）的新型涂层合成技术，目标是在完全组装的MMA器件上沉积纳米复合材料和纳米层合固体润滑剂，特别是有色氧化物和金属氮化物/硫化物。此外，还将研究等离子体放电气相沉积系统沉积的纳米复合摩擦学薄膜的基本结构和性能，包括在混合sp3/sp2碳基体中含有纳米级金属碳化物的薄膜。其次，研究摩擦学薄膜的组成/结构对性能的依赖关系，并探索摩擦化学反应在MMA应用中的膜改性机理。期望的结果包括薄膜初始纳米结构和性能与宏观尺度摩擦磨损性能的相关性，增加对这些现象的科学理解，并支持预测模型的发展。为了实现这些目标，UNT将利用新的诊断工具和方法来研究表面和亚表面区域的界面组成、周期性和形态变化，以及在不同接触应力和环境下的摩擦化学反应性，包括聚焦离子束横截面SEM、分析高分辨率TEM和局部电极3-D原子探针（LEAP）断层扫描。该提案将解决UNT与铁姆肯公司之间材料科学与工程的整合教育活动。在本课程的任期内，将为一名本科生和一名研究生提供适用于当前表面工程问题的摩擦学涂层的加工，结构和性能相互关系的全面背景知识。这将为学生提供在对未来行业需求至关重要的问题上进行外部合作的机会。PI目前和未来的一些学生包括少数民族和妇女，他们将参与合作的外部互动。这一合作企业将有助于弥合将技术从研究转移到商业应用方面的差距。夏季还将实施面向当地K-12年级的推广项目，包括教育和实践“材料营”项目。

Moving mechanical assemblies (MMA), such as miniature rolling element bearings, gears and other precision components, must function reliably and predictably in device operation. Advancements in MMA products have required a reduction in the dimensions of these devices, thereby increasing the influence of dynamic tribological surface interactions on performance and reliability. Presently, there are several shortcomings and challenges, including nanoscale conformality and uniformity of coatings on buried surfaces/interfaces, application of new routes to coating synthesis on fully assembled MMA, accurate characterization of complex coating microstructures and tribochemically-modified interfaces under shearing loads, and site-selective deposition of coating on critical tribological surfaces. UNT and Timken propose a two-fold research strategy to address these issues. First, novel coating synthesis techniques will be developed utilizing atomic layer deposition (ALD), with the goal of depositing nanocomposite and nanolaminate solid lubricants, especially lubricious oxides and metal nitrides/sulphides, on fully assembled MMA devices. In addition, the fundamental structure and properties of nanocomposite tribological films deposited with plasma-discharge vapor deposition systems will be examined, including films containing nanoscale metal carbides in mixed sp3/sp2 carbon matrices. Second, the research will address the composition/structure dependence of tribological thin films on performance and explore the mechanisms of film modification by tribo-chemical reactions in MMA applications. Desired outcomes include correlations of film initial nanostructure and properties to macro-scale friction and wear performance, increasing scientific understanding of these phenomena and supporting the development of predictive models. To accomplish these goals, new diagnostic tools and methods at UNT will be utilized to study interfacial composition, periodicity, and morphological changes occurring at the surface and in the subsurface regions, as well as tribochemical reactivity under varying contact stress and environments with focused ion beam cross-sectional SEM, analytical high resolution TEM, and local electrode 3-D atom probe (LEAP) tomography.This proposal will address educational activities with integration of Materials Science and Engineering between UNT and Timken. During the tenure of this program, one undergraduate and one graduate student will be provided a thorough background in the processing, structure and property interrelationships of tribological coatings applicable to current surface engineering issues. This will provide the students the opportunity to externally collaborate on issues critical to future industry needs. A number of the PI's current and future students include minorities and women, and they will participate in the collaborative external interaction. This cooperative venture will help bridge the gap in transferring technology from research to commercial application. Outreach programs to local K-12 levels will also be implemented in the summer with educational and hands-on 'Materials Camp' programs.