基于表面力仪的摩擦能耗机理的实验研究

The fundamental problem of Tribology is the origin of the friction force between two objects sliding to each other. So far, there is no theoretical model that can quantitatively describe the energy dissipation caused by friction. The project employs two mutually sliding graphene films as a research objective based on that the phonon dispersion relations strongly depend on the graphene layer number. In theoretical research, molecular dynamics simulation method is used to model the friction force between the two mutually sliding graphene films. A surface force apparatus is used to measure the friction force. Through investigating the friction forces dependent on the graphene layer number, temperature and sliding velocity, a relationship between the friction force and the phonon dissipation is expected to be set up, which will be used to explain the friction phenomenon in nanoscale. The other aim of the project is to look into the structure lubrication through measuring the friction force and the adhesion force between the two mutually sliding graphene films at the same time. In this way, it can in situ evaluate the variations of the surface potential quantitatively and provide the direct proof for the structure lubrication, which is attributed to the reduction of the surface potential when two incommensurate surfaces contact.

摩擦的能耗机理是摩擦学的基本问题，它涉及到摩擦力的起源，迄今为止，仍没有一个理论模型能够定量描述摩擦的能耗。基于石墨烯薄膜的声子色散曲线依赖于石墨烯的层数，项目提出以两片石墨烯薄膜相互滑动为研究对象，采用分子动力学进行理论建模和应用表面力仪进行实验测量，研究石墨烯薄膜相互滑动时的摩擦力与石墨烯层数、温度、滑动速度和外加激励的相关性，建立基于声子耗散的摩擦能耗的理论模型。将利用声子耗散模型解释纳尺度条件下滑动速度、温度对摩擦力的影响机理。项目也将同时测量石墨烯薄膜相互滑动时的摩擦力和粘附力，通过对粘附力在线测试，试图从实验上定量验证势能面减小是结构润滑的理论假说。

摩擦的能耗机理是摩擦学的基本问题，它涉及到摩擦力的起源，迄今为止，仍没有一个理论模型能够定量描述摩擦的能耗。基于石墨烯薄膜的声子色散曲线依赖于石墨烯的层数，项目组提出以两片石墨烯薄膜相互滑动为研究对象，采用分子动力学进行理论建模和应用表面力仪进行实验测量，研究石墨烯薄膜相互滑动时的摩擦力与石墨烯层数、温度、滑动速度和外加激励的相关性，建立基于声子耗散的摩擦能耗的理论模型。.本项目采用分子动力学对硅和石墨烯的摩擦特性进行了研究，发现摩擦引起的界面内声子模式和界面外的声子模式是一致的，且在一定的范围内，温度的上升除了激发出石墨烯本征频率的声子外，并不会对摩擦引起的声子耗散模式产生影响，而温度的变化也不会改变速度对摩擦声子耗散模式的影响。通过比较界面能量耗散和热域累积能量的变化，验证了界面摩擦耗散的能量与传递界面的热能相等，提出了利用热域累积热能计算摩擦力的方法。项目还发现，滑动摩擦过程中能激发低频的界面声子模式，有助于界面热量传递。项目组还用分子动力学研究了基底支撑刚度梯度变化对石墨烯层间摩擦力的影响、石墨烯层之间从公度接触到非公度接触的摩擦演化以及多层石墨烯的摩擦力和刚度关系的分子动力学模拟等。 除了项目规定的研究内容以外，在项目执行过程中，课题组还把分子动力力学摩擦仿真引入了高超声速飞行器的气固界面摩擦和热防护方面。还研究了制备液栅MoS2场效应晶体管的简便方法。目前的研究对于揭示摩擦的起源有一定的意义。