The "Water Wave Effect" In Graphene And Its Connecting Structures

In the last several decades, research on low-dimensional carbon materials has gained rapid development in some aspects, especially for the two-dimensional carbon material, graphene, which has set off unprecedented research interests in this area. Graphene, as a new type of carbon nanomaterials, has very broad application prospects due to its excellent performance in mechanical, electrical, optical and thermal aspects. Ripples on the surface of graphene, as one kind of inherent attributes, can affect its mechanical, electrical and magnetic properties. However, the intrinsic ripples of graphene, are spontaneously formed and distributed disorderly, which limits the application to a great extent. So it will extend the application range and increase the practical value if the structures and distribution of graphene ripples can be artificially controlled and designed. Therefore, it is of great theoretical significance and potential practical value to explore the method of synthesizing well-ordered ripples and study the characteristics.In this work, the method of molecular dynamics (MD) simulations have been performed to respectively study the "Water Wave Effect" in the single layer perfect graphene, defective graphene, and two graphene sheets connected by one-dimensional carbyne or the graphene nanoribbon. Some properties of graphene, defects, carbyne and graphene nanoribbons have been revealed from the perspective of deformation and energy, which enrich the research of ripples in carbon nanomaterials and provide theoretical reference for their potential applications. The main results of this thesis are given as follows:(1) The "Water Wave Effect" emerged in the graphene after the impact by C6o molecule. The contours of the dynamic ripples went through changing processes from initial hexagon to polygon until the final close circular. On the analysis of the displacements of the ripples, it was found that ripple propagation in the graphene presented damping characteristics, and the the ripple peaks underwent a fast damping as an exponential function with the increasing distance from the impact point. Ripple propagation was accompanied by an energy transfer. The strain energy concentrated in the impact point propagated to the surrounding areas radially in the form of dynamic ripples, which could effectively avoid local energy concentration. Good buffer performance exhibited in the simulations makes it possible for graphene sheets to serve as surface protection devices.(2) The introduction of the Stone Wales (SW) defect and vacancy defects could affect the ripple propagation in the graphene and make the contours of the displacement distribution irregular. Moreover, the results showed that both the SW defect and vacancy defects might be more capable of absorbing energy from the ripples and storing in itself, but have less capability to spread the gained energy out again, which meant the application prospect in the field of energy storage. In addition, the effect of the temperature on the "Water Wave Effect" was explored as well, and it was found that the rising temperature not only increased the amplitudes of the ripples and the propagation speed, but also enhanced the effect of defects on ripple propagation.(3) In the models composed of two graphene sheets connected by one-dimensional carbyne or graphene nanoribbon, the "Water Wave Effect" emerged in the small graphene sheet after the impact by C6o, and ripples could propagate to the big graphene sheet through the middle connective carbyne or graphene nanoribbon, but the intensity of the wave decrease obviously. The analysis results of the deformation and energy distribution showed that the graphene nanoribbon could spread the ripples faster and more effectively from the small graphene sheet to the big graphene sheet than the carbyne. Therefore, from the perspective of transmitting mechanical waves, whether considering the propagation speed or the efficiency, the graphene nanoribbon had better mechanical transmission performance than the carbyne.In this work, we obtained new research results in properties of graphene and its defects, provided theoretical supports for the potential application in surface protection and energy storage. The comparative studies of mechanical transmission performance between the graphene nanoribbon and carbyne, enriched the research results in ripple propagation in carbon nanomaterials and had theoretical reference value in their potential application.