Lang Haojie, Peng Yitian, Zou Kun, Huang Yao, Song Chenfei
College of Mechanical Engineering, Donghua University, Shanghai 201620, China.
Shanghai Frontiers Science Center of Advanced Textiles, Donghua University, Shanghai 201620, China.
Langmuir. 2023 Aug 15;39(32):11363-11370. doi: 10.1021/acs.langmuir.3c01197. Epub 2023 Aug 2.
Graphene has enormous potential as a solid lubricant at sliding electrical contact interfaces of micro-/nanoelectromechanical systems that suffer severe wear. Understanding the velocity-dependent friction of graphene under different applied voltages contributes to the application of graphene in sliding electrical contact scenarios. The friction of graphene, measured by conductive atomic force microscopy, under low applied voltage increases logarithmically with sliding velocity─the same as when no voltage is applied but at a faster rate of increase. The variation of friction was explained by the thermally activated Prandtl-Tomlinson model with increased potential barrier and temperature because of the applied voltage. An opposite trend in which friction decreases with sliding velocity is observed under high applied voltage. Topography, adhesion measurements, and SEM characterization demonstrate the wear of the tip. Moreover, the tip wears more severely at low sliding velocity compared to a high sliding velocity. It was interpreted that the excessive Joule heat at the electrical contact interface under high applied voltage weakens the mechanical properties of the tip, resulting in wear and high friction. The increase in the sliding velocity could accelerate the Joule heat transfer and reduce wear and friction. The studies provide beneficial guidelines for the design of graphene-lubricated sliding electrical contact interfaces.
在遭受严重磨损的微纳机电系统的滑动电接触界面处，石墨烯作为一种固体润滑剂具有巨大潜力。了解不同施加电压下石墨烯与速度相关的摩擦力，有助于石墨烯在滑动电接触场景中的应用。通过导电原子力显微镜测量，在低施加电压下石墨烯的摩擦力随滑动速度呈对数增加，这与未施加电压时相同，但增加速率更快。摩擦的变化是由热激活的普朗特 - 汤姆林森模型解释的，由于施加电压，势垒和温度增加。在高施加电压下观察到相反的趋势，即摩擦力随滑动速度降低。形貌、粘附力测量和扫描电子显微镜表征表明了探针的磨损。此外，与高滑动速度相比，在低滑动速度下探针磨损更严重。据解释，高施加电压下电接触界面处过多的焦耳热削弱了探针的机械性能，导致磨损和高摩擦力。滑动速度的增加可以加速焦耳热传递并减少磨损和摩擦。这些研究为石墨烯润滑的滑动电接触界面设计提供了有益的指导。
