石墨烯剪纸和多孔石墨烯的力学性能研究
发布时间：2018-07-26 07:49
【摘要】：石墨烯是单原子层厚度的新型二维纳米碳材料,被誉为新一代战略材料,自从2004年被发现就一直是研究人员眼中炙手可热的研究对象。目前,人们已经可以应用化学气相沉积等方法生产制备大面积、高质量的石墨烯。对于完美石墨烯的各种研究已趋于成熟,包括它卓越的力学,热学,磁学,以及电学性能等,这使它有望在高性能纳米电子器件,复合材料,能量储存等领域都获得广泛应用。另外,对于石墨烯结合块体金属、环氧树脂等的石墨烯复合材料的研究也已取得明显进展。值得注意的是,含缺陷石墨烯的性能研究刚刚起步就得到了广泛关注,例如基于古老剪折工艺的石墨烯剪纸能改善石墨烯极限应变偏小的局限,加强它的延展性;多孔石墨烯优异的使用性能将石墨烯的应用拓展到了DNA分子检测等微观过滤的领域。分子动力学是一种成熟的数值模拟方法,它可以对微纳材料进行基本真实的机械模拟从而得到材料的多种机械性能,现已广泛应用于细观材料的性能研究,并获得了广泛的认同。本文主要以单/双层石墨烯剪纸和多孔石墨烯为研究对象,使用分子动力学工具LAMMPS对结构施加单轴拉伸荷载直至结构破坏,辅以成像软件VMD,观察了结构的破坏过程,并绘制了不同结构的拉伸应力应变曲线,得到了两种石墨烯的拉伸变形及破坏机制。最后,对两种石墨烯分别定义三个不同含义的无量纲几何参数来建立不同的结构,通过模拟得到结构的拉伸力学参数随几何参数的变化规律。通过比较,我们证实剪纸工艺确实能有效提高石墨烯的拉伸极限应变3到6倍,即有效地提高了石墨烯的延展性。另外,我们通过对力学参数变化趋势的研究,得到了有效调控石墨烯剪纸极限应变大小的方法,即实现力学性能参数的可控性。这将为石墨烯在柔性器件中的使用奠定理论基础。对双层石墨烯剪纸结构的研究证明剪纸工艺也能增大双层石墨烯的极限应变,且双层石墨烯剪纸的变形规律和单层石墨烯剪纸的基本类似。对多孔石墨烯的研究表明,虽然多孔石墨烯中的纳米孔的存在降低了石墨烯的强度,但是合理减小孔的密度仍然可以保持石墨烯高强度的优势,且通过合理改变几何参数的大小可以人为地调控结构力学参数的大小。多孔石墨烯的极限应变,极限应力和杨氏模量均随着垂直于拉伸方向上孔的密度的增大而减小。另外,结构的刚度严格随孔密度的增大而减小。这将为石墨烯在过滤等高强度要求的应用领域的设计提供参考。
[Abstract]:Graphene is a new two-dimensional nano-carbon material with the thickness of single atomic layer. It is praised as a new generation of strategic materials. It has been a hot research object in the eyes of researchers since it was discovered in 2004. At present, large area and high quality graphene can be produced by chemical vapor deposition. All kinds of research on perfect graphene have become mature, including its excellent mechanical, thermal, magnetic and electrical properties. It is expected to be widely used in high performance nanoelectronic devices, composite materials, energy storage and other fields. In addition, the research of graphene bonded bulk metal, epoxy resin and other graphene composites has also made remarkable progress. It is worth noting that the study on the properties of graphene containing defects has been paid more and more attention at the beginning. For example, the paper-cut of graphene based on the ancient shear folding process can improve the limit of the limit strain of graphene and strengthen its ductility. The excellent performance of porous graphene extends the application of graphene to microfiltration such as DNA molecular detection. Molecular dynamics is a mature numerical simulation method. It can be used to simulate the mechanical properties of micro and nano materials and obtain a variety of mechanical properties. It has been widely used in the study of properties of meso-materials. And has been widely recognized. In this paper, single / double layer graphene paper-cut and porous graphene were used to apply uniaxial tensile load to the structure and the imaging software VMD was used to observe the damage process of the structure. The tensile stress-strain curves of different structures were plotted and the tensile deformation and failure mechanisms of two graphene were obtained. Finally, three dimensionless geometric parameters with different meanings are defined for the two graphene to establish different structures, and the variation of tensile mechanical parameters with geometric parameters is obtained by simulation. By comparison, it is proved that paper-cut process can effectively increase the tensile limit strain of graphene by 3 to 6 times, that is, the ductility of graphene can be improved effectively. In addition, through the study of the changing trend of mechanical parameters, we have obtained an effective method to control the limit strain of graphene paper-cut, that is, to realize the controllability of mechanical properties. This will lay a theoretical foundation for the use of graphene in flexible devices. The study on the paper-cut structure of bilayer graphene proves that the paper-cutting process can also increase the limit strain of bilayer graphene, and the deformation law of double-layer graphene paper-cut is similar to that of monolayer graphene paper-cut. The study of porous graphene shows that the strength of graphene can be reduced by the existence of nano-pore in porous graphene, but the advantage of high strength of graphene can be maintained by reasonably decreasing the density of pore. The size of structural mechanics parameters can be adjusted artificially by changing the geometric parameters reasonably. The ultimate strain, ultimate stress and Young's modulus of porous graphene decrease with the increase of pore density perpendicular to the tensile direction. In addition, the stiffness of the structure decreases strictly with the increase of the hole density. This will provide reference for the design of graphene in high strength applications such as filtration.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O613.71
本文编号：2145348
[Abstract]:Graphene is a new two-dimensional nano-carbon material with the thickness of single atomic layer. It is praised as a new generation of strategic materials. It has been a hot research object in the eyes of researchers since it was discovered in 2004. At present, large area and high quality graphene can be produced by chemical vapor deposition. All kinds of research on perfect graphene have become mature, including its excellent mechanical, thermal, magnetic and electrical properties. It is expected to be widely used in high performance nanoelectronic devices, composite materials, energy storage and other fields. In addition, the research of graphene bonded bulk metal, epoxy resin and other graphene composites has also made remarkable progress. It is worth noting that the study on the properties of graphene containing defects has been paid more and more attention at the beginning. For example, the paper-cut of graphene based on the ancient shear folding process can improve the limit of the limit strain of graphene and strengthen its ductility. The excellent performance of porous graphene extends the application of graphene to microfiltration such as DNA molecular detection. Molecular dynamics is a mature numerical simulation method. It can be used to simulate the mechanical properties of micro and nano materials and obtain a variety of mechanical properties. It has been widely used in the study of properties of meso-materials. And has been widely recognized. In this paper, single / double layer graphene paper-cut and porous graphene were used to apply uniaxial tensile load to the structure and the imaging software VMD was used to observe the damage process of the structure. The tensile stress-strain curves of different structures were plotted and the tensile deformation and failure mechanisms of two graphene were obtained. Finally, three dimensionless geometric parameters with different meanings are defined for the two graphene to establish different structures, and the variation of tensile mechanical parameters with geometric parameters is obtained by simulation. By comparison, it is proved that paper-cut process can effectively increase the tensile limit strain of graphene by 3 to 6 times, that is, the ductility of graphene can be improved effectively. In addition, through the study of the changing trend of mechanical parameters, we have obtained an effective method to control the limit strain of graphene paper-cut, that is, to realize the controllability of mechanical properties. This will lay a theoretical foundation for the use of graphene in flexible devices. The study on the paper-cut structure of bilayer graphene proves that the paper-cutting process can also increase the limit strain of bilayer graphene, and the deformation law of double-layer graphene paper-cut is similar to that of monolayer graphene paper-cut. The study of porous graphene shows that the strength of graphene can be reduced by the existence of nano-pore in porous graphene, but the advantage of high strength of graphene can be maintained by reasonably decreasing the density of pore. The size of structural mechanics parameters can be adjusted artificially by changing the geometric parameters reasonably. The ultimate strain, ultimate stress and Young's modulus of porous graphene decrease with the increase of pore density perpendicular to the tensile direction. In addition, the stiffness of the structure decreases strictly with the increase of the hole density. This will provide reference for the design of graphene in high strength applications such as filtration.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O613.71
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