Role of multigrain structure on friction of graphene layers
Role of multigrain structure on friction of graphene layers
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DOI：
10.1016/j.commatsci.2019.04.024
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发表时间：
2019-07-01
影响因子：
3.3
通讯作者：
Kim, Woo Kyun
中科院分区：
文献类型：
--
作者：
Li, Huyan;Kim, Woo Kyun
石墨烯是一种单原子厚度的二维材料，作为工业应用的固体润滑剂具有巨大的潜力。石墨烯通常通过化学气相沉积（CVD）合成，因为其简单性和可扩展性。然而，CVD生长的石墨烯片具有多晶粒结构，这可能对单晶石墨烯的上级性质具有不利影响。特别是，这种多晶结构对石墨烯摩擦的影响仍然远未完全理解。在这项研究中，我们调查多晶粒石墨烯层之间的摩擦，使用分子动力学（MD）模拟。MD模拟研究的关键因素，如晶粒尺寸和取向，和形态的晶界与几个不同的多晶粒配置。模拟结果表明，多晶粒石墨烯层表现出低，但不能完全忽略，摩擦。观察到的摩擦行为进行了分析，在晶粒和晶界（GB）之间的相互作用。在大多数模型中，颗粒间相互作用对总摩擦力的贡献可以忽略不计，但如果一些颗粒对由于取向上的小失配而配置相称界面，则它们表现出相对较大的摩擦。涉及晶界的相互作用往往表现出较大的摩擦力，其中最大的摩擦力出现在晶界与晶界的直接接触处。分析表明，晶界附近摩擦力的增加与晶界附近层间距离的减小直接相关，而层间距离的减小是由晶界附近层间翘曲引起的。
Graphene is a one-atom thick two-dimensional material and has a huge potential as a solid lubricant for industrial application. Graphene is often synthesized by chemical vapor deposition (CVD) because of its simplicity and scalability. However, CVD-grown graphene sheets have the multigrain structure, which may have detrimental effects on the superior properties of single-crystal graphene. In particular, the effects of this polycrystalline structure on graphene friction remain far from completely understood. In this study, we investigate the friction between multigrain graphene layers using molecular dynamics (MD) simulations. The MD simulations examine key factors such as grain size and orientation, and morphology of grain boundaries with several different multigrain configurations. The simulation results reveal that multigrain graphene layers exhibit low, but not completely negligible, friction. The observed frictional behaviors are analyzed in terms of the interactions between grains and grain boundaries (GB). In most models, the contribution of the grain-to-grain interaction to the total friction force is negligible, but some grain pairs exhibit relatively large friction if they configure the commensurate interface due to small mismatch in orientation. The interactions involving grain boundaries often exhibit large friction with the largest at the direct GB-to-GB contacts. An analysis shows that the increase in friction near the grain boundary region is directly related to the decrease in interlayer distance, which is caused by the warping of layers in the vicinity of grain boundaries.