Zhao Xin, Papageorgiou Dimitrios G, Zhu Liyan, Ding Feng, Young Robert J
National Graphene Institute and School of Materials, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
Nanoscale. 2019 Aug 1;11(30):14339-14353. doi: 10.1039/c9nr04720d.
The deformation and fracture behaviour of one-atom-thick mechanically exfoliated graphene has been studied in detail. Monolayer graphene flakes with different lengths, widths and shapes were successfully prepared by mechanical exfoliation and deposited onto poly(methyl methacrylate) (PMMA) beams. The fracture behaviour of the monolayer graphene was followed by deforming the PMMA beams. Through in situ Raman mapping at different strain levels, the distributions of strain over the graphene flakes were determined from the shift of the graphene Raman 2D band. The failure mechanisms of the exfoliated graphene were either by flake fracture or failure of the graphene/polymer interface. The fracture of the flakes was observed from the formation of cracks identified from the appearance of lines of zero strain in the strain contour maps. It was found that the strength of the monolayer graphene flakes decreased with increasing flake width. The strength dropped to less than ∼10 GPa for large flakes, thought to be due to the presence of defects. It is shown that a pair of topological defects in monolayer graphene will form a pseudo crack and the effect of such defects upon the strength of monolayer graphene has been modelled using molecular mechanical simulations.
人们已经详细研究了单原子厚的机械剥离石墨烯的变形和断裂行为。通过机械剥离成功制备了具有不同长度、宽度和形状的单层石墨烯薄片，并将其沉积在聚甲基丙烯酸甲酯（PMMA）梁上。通过使PMMA梁变形来跟踪单层石墨烯的断裂行为。通过在不同应变水平下进行原位拉曼映射，根据石墨烯拉曼2D带的位移确定石墨烯薄片上的应变分布。剥离石墨烯的失效机制要么是薄片断裂，要么是石墨烯/聚合物界面失效。从应变等高线图中零应变线的出现所识别出的裂纹形成情况观察到薄片的断裂。研究发现，单层石墨烯薄片的强度随着薄片宽度的增加而降低。对于大尺寸薄片，强度降至约10 GPa以下，认为这是由于存在缺陷所致。结果表明，单层石墨烯中的一对拓扑缺陷将形成一个伪裂纹，并且已经使用分子力学模拟对这类缺陷对单层石墨烯强度的影响进行了建模。
