DLC-离子液体复合薄膜的微/纳织构化构筑及其抗粘减摩协同效应研究

Diamond-like carbon (DLC) films with high hardness, low friction coefficient and good wear resisitance have aroused particular interest as protective film. Ionic liquids (ILs) display better tribological properties than that of conventional lubricants,such as PFPE and X-1P. Micro/nano-textures fabricated on surface would change interface weeting behavior, ruduce real contact area between sliding pairs, trap wear particles and act as reserviors for lubricants so as to improve the tribological performances of materials. In order to solve the key factors including adhesion, friction and wear phenomenon which influence significantly the reability and stability of M/NEMS, taking advantage of surface texture and chemical modification, combined with hard and soft films, the DLC-IL composite films with micro/nano-structures which show superior anti-adhesion and friction reduction behaviors will be designed and fabricated. The effects of geometrical parameters (including texture shape, height, depth, width, surface roughness and fractional surface coverage) and chemical modification (surface chemistry and distribution) on the structure, physicochemical and nanotribological properties of DLC films will be systemically investigated. The corresponding synergetic anti-adhesion and friction reduction mechanisms of surface texture and chemical modification will be discussed and clarified with emphasis. The objective of this project is to understand and aid the design and selection of appropriate micro/nano-textures and surface chemistry for improving micro/nano-tribological properties in M/NEMS.

DLC薄膜具有高硬度、低摩擦系数和强耐磨性等优点而成为薄膜领域研究的热点。离子液体具有优异的抗磨减摩性能，性能优于传统润滑材料如PFPE和X-1P。在材料表面构筑微/纳织构可以起到改变界面润湿性、摩擦副之间的接触面积及捕获磨损粒子而减小犁沟的作用从而改善材料的摩擦学性能。本项目针对因界面粘着、摩擦和磨损现象制约M/NEMS系统可靠性和稳定性的关键问题，提出以DLC薄膜和离子液体为研究对象，以织构化和复合化为导向，将硬膜和软膜有机结合起来，设计和构筑具有优异抗粘减摩性能的DLC-离子液体复合薄膜。重点考察几何参数（包括织构形状、高度、深度、宽度、粗糙度和表面覆盖率）和表面化学修饰（离子液体薄膜组分和分布）对DLC薄膜表面结构、物化性能和抗粘减摩性能的影响规律，探讨微/纳织构和离子液体薄膜对DLC表面的协同抗粘减摩机制，提出一个改善表面微/纳摩擦学行为的织构化、复合化薄膜设计和制备的新途径。

通过在材料表面制备微/纳织构和低表面能涂层这两种方法可以有效降低接触界面的粘着力和摩擦力，对于提升微/纳机电系统运行的可靠性和稳定性非常有益。DLC薄膜具有高硬度、低摩擦系数和强耐磨性等优点而成为薄膜领域的研究热点。离子液体具有优异的抗磨减摩性能，优于传统润滑材料如PFPE和X-1P。因此，发挥固/液涂层协同润滑的优点，利用固体润滑涂层、微/纳织构和离子液体薄膜的独特性能，是一种非常有前景的改善润滑涂层寿命和可靠性的设计思路。. 在本项目中，我们结合等离子体刻蚀技术、磁控溅射技术和浸渍-提拉技术，成功制备了三种典型几何形貌特征的DLC-IL复合薄膜，包括凸柱、凹坑和沟槽。利用原子力显微镜、X射线电子能谱和拉曼光谱考察了DLC-IL复合薄膜的表面微/纳结构和化学组成。采用先进的胶体微球探针技术在接触模式下考察了复合薄膜的粘着和纳米摩擦学性能。利用UMT-3摩擦磨损实验机在球-盘往复模式测定了DLC和DLC-IL复合薄膜的微摩擦学特性。. 结果显示：DLC薄膜的粘着力和摩擦力随着微织构的密度增加而减小，离子液体薄膜的引入进一步降低了界面的粘着力和摩擦力，不同微观结构对其影响程度不一。本研究重点讨论和分析了表面微结构和化学修饰对于涂层界面协同抗粘减摩的机理。粘着力和摩擦力的有效降低主要归结为两个原因：（1）微纳结构的存在有效降低了DLC薄膜和胶体微球探针的有效解除面积；（2）离子液体薄膜的存在避免了DLC薄膜和摩擦对偶材料的直接接触，从而降低了界面的摩擦阻力。希望本研究能为微/纳机电系统中材料的选择和微纳结构构筑提供一定的帮助。