石墨烯—纳米探针黏结行为数值模拟及其实验研究

发布时间：2018-07-15 16:08

【摘要】：石墨烯(Graphene)是迄今为止人类测量过的强度最高的材料,具有优异的力学、电学、光学、和热学性能,成为最有深刻改变人类社会潜力的材料之一,也是固体润滑剂的重要备选材料。原子力显微镜(AFM)是在纳米尺度上研究物质性能的重要仪器,也是研究石墨烯性能的常用工具。研究AFM探针与石墨烯之间的接触、摩擦规律,对充分理解AFM探针与石墨烯之间的黏结行为特征,进一步利用原子力显微镜研究石墨烯和其他二维材料具有重要意义。本文基于AFM探针表面原子、石墨烯原子排列特征,针对黏结力和接触面积,应用连续介质力学理论和有限元方法(FEM),对AFM探针和石墨烯之间的黏结行为进行了数值模拟,并在硅基体进行了探针和石墨烯的黏结实验。本文主要研究内容如下:①根据黏结测试系统中石墨烯、探针、基体尺寸特征和作用体之间的物理、力学作用影响因素,结合力、接触面积、基体表面作用、厚度相互影响关系的测试目的,分析并抽取系统关键建模因素,建立了石墨烯-纳米探针黏结行为的有限元分析模型。②基于石墨烯单原子厚度的二维材料特征,分析连续介质力学理论与方法的适用性和特殊处理措施。结合碳纳米管和石墨烯间的几何关系,由碳纳米管力学参数计算单层碳原子膜的力学参数,建立了适用于石墨烯-纳米探针粘结行为数值模拟的等效弹性壳模型。③针对特定的原子间作用势,根据作用体不同的二维、三维原子排列结构,推导其界面势能和作用力。根据石墨烯中碳原子面密度和探针、基体中原子等效体密度,通过石墨和二氧化硅界面之间及其自身界面之间的黏结功,确定了石墨烯、探针、基体模型中各界面势能函数和作用力函数的基础参数。④在无法定量确定石墨烯层间摩擦状态情况下,针对层间零摩擦、层间无限大摩擦、层间有限摩擦三种情况,设定三类摩擦状态模型。⑤为解决复杂非线性力和接触状态下难以求得静态解的难题,应用动态求解方法并采取探针间歇式进给方式,使探针悬停过程中系统能量逐步耗散,求得难收敛模型的准静态解。⑥应用隐式和显式有限元分析方法,分别研究石墨烯厚度从一层增加至四层过程中,探针-石墨烯之间的作用力和黏结面积。通过求解不同基体表面影响因数、不同石墨烯厚度条件下的探针黏结力、黏结面积,研究不同强度基体影响情况下,石墨烯从薄变厚过程中,探针黏结力、黏结面积的变化关系。⑦用机械剥离法制备不同厚度的石墨烯,并在硅基体上用原子力显微镜进行黏结测试,与数值模拟结果进行对比分析。本论文取得的成果如下:①层间零摩擦、层间无限大摩擦、和层间有限摩擦三类模型结果,显示了石墨烯从单层增加至多层过程中,黏结力随层数和基体表面作用强度的变化趋势。变化趋势与理论分析和测试现象一致。②模拟计算和实验结果均显示出石墨烯与基体间的作用强度对探针黏结力和接触面积关系的重要影响。研究结果清晰展示了强、弱基体表面作用状态下,不同厚度石墨烯之间,黏结力与接触面积之间方向相反的两种变化趋势。两种相反趋势对应的强、弱基体表面作用强度之间没有明显过渡范围的情况,显示出随强度变化出现的黏结行为特征突变现象。③石墨烯与基体间作用强度对等值黏结力作用下石墨烯接触面积随厚度变化关系的影响,使实际摩擦实验中会产生摩擦力和厚度直接相关的显著表现,解释了以石墨烯为代表的二维材料普遍存在的摩擦性能厚度依赖现象。④单层石墨烯和多层石墨烯对应的黏结力在计算和实验中的差异,显示出探针表面粗糙度对单层和多层石墨烯的不同影响,为探针表面形貌和二维材料自身力学属性的深入研究提出更多启示。⑤计算和实验结果中薄、厚石墨烯的黏结性能特征,为表面非理想光滑的探针在与二维材料黏结过程中可能存在的时间效应现象提供了可能的机理基础。⑥石墨烯和纳米探针之间黏结特征与宏观尺度材料相应表现的明显不同,显示出范德华长程作用力在纳米尺度材料行为上的直接作用,为更深入的二维材料力学性能研究提供了参考。本研究实现了应用连续介质力学理论对石墨烯进行建模及力学性能的数值模拟,研究方法在一定条件下可推广应用至其它二维材料,为研究二维材料的力学性能提供了除分子动力学(MD)方法之外的参考途径。计算结果为用原子力显微镜测量石墨烯的力学性能提供了探索性研究依据。
[Abstract]:Shi Moxi (Graphene) is the most powerful material measured by mankind so far. It has excellent mechanical, electrical, optical and thermal properties. It has become one of the most profound materials to change the potential of human society, and is also an important alternative for solid lubricants. AFM is an important study of material properties at nanoscale. It is also a common tool to study the properties of graphene. The study of the contact between the AFM probe and graphene, the law of friction, the full understanding of the bonding behavior between the AFM probe and the graphene, and the further study of graphene and other two-dimensional materials by atomic force microscopy. Based on the surface atom of the AFM probe, graphite The arrangement characteristics of the alkene atoms, using the continuum mechanics theory and the finite element method (FEM), the bonding behavior between the AFM probe and the graphene is numerically simulated by using the continuum mechanics theory and the finite element method (FEM). The bonding experiment between the probe and the graphene is carried out on the silicon substrate. The main contents are as follows: 1. The graphite in the bonding test system The finite element analysis model of the bonding behavior of graphene nano probe was established. The finite element analysis model of graphene nano probe was established. The applicability and special treatment measures of the continuum mechanics theory and method are analyzed. The mechanical parameters of the single layer carbon atom film are calculated by the mechanical parameters of the carbon nanotube and the mechanical parameters of the carbon nanotube. The equivalent elastic shell suitable for the numerical simulation of the bonding behavior of the graphene nanomi probe is established. In accordance with the specific interatomic potential, the interfacial potential energy and force are deduced according to the different two-dimensional and three-dimensional atomic arrangement structure of the acting body. Based on the carbon atomic surface density and the probe, the atomic equivalent body density in the matrix and the bonding work between the graphite and silicon dioxide interface and its interface, the stone is determined. The basic parameters of the potential energy function and the force function of each interface in the model of the ink ene, probe and matrix. (4) in the case of inability to determine the frictional state of the graphene, three kinds of friction state models are set for the zero friction between layers, infinite friction between layers and finite friction between layers. 5. To solve complex nonlinear forces and contact states. It is difficult to obtain the difficult problem of static solution. The dynamic solution method is applied and the probe batch feed is adopted to make the system energy dissipate gradually during the probe suspension process and obtain the quasi-static solution of the difficult convergence model. 6. The probe graphite is studied by using implicit and explicit finite element methods to study the Shi Moxi thickness from one layer to four layers. Force and bonding area between alkenes. By solving the influence factors of different substrate surface, the bonding area of the probe and the adhesion area under the different thickness of graphene, the relationship between the bonding force and the adhesion area of the probe in the thin thickness process, the bond force and the adhesive area of the probe. Graphene is tested on the silicon substrate by atomic force microscopy, and the results are compared with the numerical simulation results. The results obtained in this paper are as follows: (1) the results of three types of models, zero friction, infinite friction between layers, and interlayer finite friction, show that the bonding force varies with the number of layers and the matrix in the process of the increase of graphene from the monolayer to the multilayer. The change trend of the surface action strength. The change trend coincide with the theoretical analysis and the test phenomenon. 2. Both the simulated calculation and the experimental results show the important influence of the action strength between the graphene and the matrix on the relationship between the bond force and the contact area of the probe. The results clearly show the strong, weak base surface action state, the different thickness of the graphene Between the two trends in the opposite direction between the bonding force and the contact area. The strength of the two opposite trends is strong. There is no obvious transition range between the strength of the weak matrix surface and the phenomenon of the bonding behavior with the change of strength. 3. The peer-to-peer interaction between the interaction strength of graphene and the matrix The influence of the contact area of the contact with the thickness of the ink makes the friction force and the thickness directly related to the actual friction experiment. It explains the common friction thickness dependence of the two-dimensional material represented by graphene. (4) the bonding force corresponding to the single graphene and the multilayer calculus is in the calculation and experiment. The difference shows that the surface roughness of the probe has different effects on the monolayer and multilayered graphene, and puts forward more enlightenment for the deep study of the surface morphology of the probe and the mechanical properties of the two-dimensional material. The possible mechanism basis for the possible time effect is provided. 6. The bonding characteristics between the graphene and the nanoscale probe are obviously different from the macroscopic scale materials, which shows the direct effect of the van Edward's long-range force on the behavior of nanoscale materials, which provides a reference for the further study of the mechanical properties of the two dimensional materials. In this study, the numerical simulation of the modeling and mechanical properties of graphene by using the continuum mechanics theory is realized. The study method can be applied to other two-dimensional materials under certain conditions. It provides a reference for the study of the mechanical properties of two dimensional materials. The result is atomic force microscopy. The measurement of the mechanical properties of graphene provides an exploratory research basis.
【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ127.11;TB383.1

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