Solid lubrication by carbon nanotubes: Understanding transfer layer formation and sliding at a fundamental level using atomistic simulations and experimental nano analytics

摩擦和磨损造成巨大的成本，约占高度工业化国家国内生产总值的5%。与此同时，出于环境原因和为了减少对化石油资源的依赖，人们正在努力将液体润滑剂改为固体润滑剂。然而，目前固体润滑剂只适用于液体润滑失效的地方。这是在真空、高温、高压和滑动速度等极端条件下的情况。因此，固体润滑系统的进一步开发和设计，特别是在高机械负荷下的固体润滑系统，具有很高的技术相关性。碳纳米管（Carbon nanotubes, CNTs）是由碳原子构成的圆柱形纳米结构，具有优异的机械、物理和化学性能，是与石墨或石墨烯密切相关的一类材料。结合精心准备和结构的摩擦表面，它们可以作为高效和耐用的固体润滑剂。另一方面，人们对决定CNTs摩擦学行为的微观机制了解甚少。尚未解决的主要问题涉及摩擦层和传递层的形成、润滑过程以及碳纳米管在机械和摩擦化学载荷下的降解。因此，碳纳米管润滑的控制设计需要进一步的研究活动。本研究计划的目标是在微观层面上更深入地了解摩擦力学和摩擦化学方面。我们的研究成果将用于制定高机械载荷下球轴承目标应用的设计规则。这意味着我们必须找出哪个参数一方面决定了传递层的形成另一方面决定了摩擦的减少。该研究计划将原子模拟与摩擦学实验以及物理和化学分析相结合。

Friction and wear cause tremendous costs which amount to about 5 % of the gross domestic product of highly industrialized countries. At the same time, there are many efforts to change from liquid to solid lubricants for environmental reasons and in order to reduce the dependence on fosil oil resources. However, at the moment solid lubricants are only applied where liquid lubrication fails. This is the case under extreme conditions as in vacuum, at high temperatures, pressures and sliding velocities. The further development and design of solid lubrication systems especially also under high mechanical loading is thus of high technological relevance.Carbon nanotubes (CNTs) are cylindrical nano structures made from carbon Atoms with excellent mechanical, physical and chemical properties and are as a materials class closely related to graphite or graphene. In combination with well prepared and structured tribo surfaces they can act as highly efficient and durable solid lubricants. On the other side, the microscopic mechanisms determining the tribological behaviour of CNTs is only poorly understood. The main unanswered questions concern the formation of tribo- and transfer layers, the lubrication processes and the Degradation of CNTs under mechanical and tribochemical loading. The controlled design of CNT lubrication therefore requires further Research activitites.Goal of this research proposal is a more in-depth understanding of the tribomechanical and tribochemical aspects at the microscopic level. The outcome of our research will be used to develop design rules for the target application of ball bearings under high mechanical loading. That means we have to find out which parameter determine the formation of transfer layers on one hand and the friction reduction on the other.The research proposal combines atomistic simulations with tribological experiments and physical as well as chemical analytics.