氮气环境中水氧含量对于CNx薄膜超低摩擦界面转移膜的形成具有决定性作用。为了澄清转移膜在CNx薄膜超低摩擦行为中的作用机理，本课题针对极限水氧含量（ppm级别）氮气下超低摩擦界面孤岛状转移膜的形成机制、演化规律和人为调控等三项内容开展研究。利用极限环境-球盘摩擦-拉曼光谱-原子力扫描测试系统进行CNx薄膜的超低摩擦实验，对孤岛状转移膜的成分、结构、分布形态和力学特性分别进行拉曼光谱和原子力扫描准原位测试，在此基础上对孤岛状转移膜几何形状和局部结构的演变进行纳米接触力学解析。通过稳态摩擦下转移膜的表征，揭示界面剪切诱导下孤岛状转移膜局部结构相变机理。通过磨合过程中转移膜的解析，阐明临界摩擦距离随孤岛状转移膜表面最大接触应力的变化规律。通过初始磨合的控制，实现ppm到百分比级别水氧含量氮气环境中CNx薄膜的稳定超低摩擦。研究结果将为碳基薄膜界面转移膜减摩理论和节能摩擦学系统设计提供基础支持。

Water and oxygen content in nitrogen gas environment is a key point for the formation of tribo-film at the contact interface in the super-low friction of CNx coatings. To clarify the role of tribo-film in the super-low frictional behavior of CNx coatings, this application tends to carry out studies in three aspects: formation mechanism, evolution, and artificial control of isolated tribo-film islands at the contact interface in the super-low friction of CNx coatings under nitrogen gas environment with extreme water and oxygen content (ppm level). Super-low friction tests of CNx coatings are conducted by using an Extreme environment-Ball-on-disk tribometer-Raman-AFM system. The composition, the structure, the topography, and the mechanical behavior of isolated tribo-film islands are semi in-situ analyzed by Raman spectroscopy and atomic force microscopy (AFM), respectively, and then the evolution of geometric shape and local structure of isolated tribo-film islands is analyzed by using nano-scale contact mechanical method. By characterizing the tribo-film under the steady state, the local structural phase transition mechanism of isolated tribo-film islands induced by shearing force at the contact interface is revealed. By analyzing the tribo-film during the running-in process, the variation of critical rubbing distance with the maximum contact stresses on the surface of isolated tribo-film islands is elucidated. By controlling the initial running-in process, stable super-low friction of CNx coatings under nitrogen gas environment with water and oxygen content in the levels from ppm to percentage is obtained. The achievement of this project will provide research basis for friction reduction theory of tribo-film at the contact interface in the carbon-based coatings and design of energy-saving tribo-systems.