超薄纳晶石墨烯层诱导的近零磨合期低摩擦行为研究

Amorphous carbon film generally undergoes a long high-friction run-in period before reaching the stable low-friction stage. For application of low friction, shortening or eliminating the high-friction run-in period is still an important problem. This project proposes to solve the problem by depositing an ultrathin graphene nanocrystallite layer on the amorphous carbon film. During the friction, the ultrathin graphene nanocrystallite layer will induce the formation of graphene on the contact surface quickly, and the film reaches the low-friction stage with a near-zero-run-in period. Aiming at the scientific problem of “principle of near-zero-run-in-period low-friction behavior induced by ultrathin graphene nanocrystallite layer ”, this application tends to carry out studies in three aspects: triggering low friction with the formation of graphene, regulating near-zero-run-in period with nanocrystallite size, and the low friction mechanism under different friction conditions. More specially: (1) Through testing friction behaviors of the films with a Pin-on-Disk tribometer, and observing the formation of graphene induced by graphene nanocrystallite with Tip-Enhanced Raman Spectroscopy and Double Spherical Aberration-Corrected Transmission Electron Microscope, the triggering of low friction with the formation of graphene is revealed . (2) Through tuning the formation speed of graphene with nanocrystallite size, the regulatory mechanism of near-zero-run-in period is clarified. (3) Through analyzing the nanostructure evolution of graphene under different friction conditions, and the effect of graphene polycrystalline structure on the low friction behavior is studied, and the near-zero-run-in-period super-low-friction behavior is obtained. The research outcomes provide an new idea for the design and fabrication of near-zero-run-in-period low-friction films.

非晶碳膜在达到低摩擦状态前常会经历长时间的高摩擦磨合阶段，如何缩短乃至消除高摩擦磨合期是低摩擦应用中的重要难题。本项目提出在非晶碳膜上制造一层超薄纳晶石墨烯，来快速诱导摩擦界面上形成石墨烯，使碳膜在近零磨合期下达到低摩擦状态。针对“超薄纳晶石墨烯层诱导的近零磨合期低摩擦原理”这一核心科学问题，围绕石墨烯的形成对低摩擦的促发作用，纳晶尺寸对近零磨合期调控机制，不同摩擦条件对低摩擦的作用机理等三项内容开展研究。具体如下：（1）通过球盘型摩擦实验，结合原子力针尖增强拉曼光谱和双球差透射电镜辨析纳晶石墨烯层诱导下石墨烯的形成，揭示石墨烯的形成对低摩擦的促发作用；（2）利用纳晶尺寸控制石墨烯形成速度，澄清近零磨合期调控机制；（3）分析不同摩擦条件下石墨烯的结构演变规律，阐明石墨烯多晶结构对低摩擦行为影响机理，获得近零磨合期超低摩擦碳膜。本研究结果为具有近零磨合期低摩擦行为的薄膜设计制造提供新思路。

非晶碳膜在达到低摩擦状态前常会经历长时间的高摩擦磨合阶段，如何缩短乃至消除高摩擦磨合期是低摩擦应用中的重要难题。为此，本项目提出在非晶碳膜上制造一层超薄纳晶石墨烯，来快速诱导摩擦界面上形成石墨烯，使碳膜在近零磨合期下达到低摩擦状态。具体围绕石墨烯的形成对低摩擦的促发作用，纳晶尺寸对近零磨合期调控机制，不同摩擦条件对低摩擦的作用机理等三项内容开展研究。研究结果发现：（1）利用低能电子照射诱导沉积方法在非晶碳膜上实现了纳晶石墨烯覆盖层制造，并获得了近零磨合期低摩擦行为，通过透射电镜揭示了纳晶石墨烯覆盖层可诱导石墨烯化转移膜的快速形成，进而促发碳膜进入低摩擦状态的作用机制；（2）获得了磨合期随覆盖层中纳晶尺寸的变化规律，再结合纳米刻划，纳米压痕测试，以及高温退火实验结果，阐明了近零磨合期低摩擦机理为：相比于非晶碳，纳晶石墨烯覆盖层易于磨损，从而起到牺牲层的作用，并在摩擦力作用下纳晶石墨烯层能够快速重构，形成纳晶石墨烯化的转移膜，从而进入低摩擦状态；（3）通过元素掺杂在电子照射下实现了超光滑纳晶碳膜制造，提出超光滑机理为掺杂元素诱导碳膜内碳化物键合的形成，并使纳晶石墨烯的生长方向由垂直取向转变为随机取向。分析了不同元素掺杂条件下的纳晶碳膜快速低摩擦行为，澄清了摩擦氧化和石墨烯化对稳定低摩擦系数的影响，并在载流条件下获得了硅掺杂纳晶石墨烯碳膜的零磨合期低摩擦行为。以上研究结果为具有近零磨合期低摩擦行为的薄膜设计制造提供新思路。此外，将该项目的纳晶石墨烯碳膜精确可控制造技术，拓展至柔性传感应用领域，成功制造了一种具有超高灵敏系数和高拉伸性（最大应变15%）的柔性力学传感器，并实现了多种人体运动检测应用。因其具有远超常规应变片的灵敏系数，其在开发适用于超低摩擦实验的摩擦磨损试验机设计制造上具有可观的应用潜力