大气下单层石墨烯的热稳定性及纳米摩擦特性研究

发布时间：2018-05-01 23:01

本文选题：化学气相沉积 + 石墨烯　；参考：《江苏大学》2015年硕士论文

【摘要】：石墨烯是仅有一个碳原子层厚度的新型二维材料,具六角型蜂窝状晶格结构,由于其拥有诸如高电子迁移率、室温下的量子霍尔效应、高热导率与透光率等优异的物化性质而闻名于世。国内外研究者普遍认为石墨烯可取代硅,成为新一代半导体器件的基础材料,具有广泛的研究和应用价值。然而在石墨烯的应用中,仍有许多理论问题亟待解决。如石墨烯的热稳定性研究对石墨烯基器件的设计及在实际应用中的稳定性要求,都有着重要的指导性意义。另外,由于石墨烯具有较高的比表面积,与其表面相关的一些作用力都显著增强,且对周围环境极其敏感,所以研究不同环境下,石墨烯表面效应对石墨烯基器件的制备和装配都有极其重要的意义。本文将详细介绍石墨烯的主要物化性质、应用、常用制备方法和微观结构表征手段,探讨石墨烯的热稳定性与纳米摩擦学特性的国内外研究现状。通过对比分析目前主要的石墨烯制备方法,采用化学气相沉积(Chemical vapor deposition,CVD)法制备石墨烯样品。利用光学显微镜、原子力显微镜(Atomic force microscopy,AFM)、激光共聚焦拉曼(Raman)及X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)等对所制备的实验样品进行表征,为后续实验的开展奠定基础。利用Raman、XPS、AFM,重点研究了CVD方法制备的单层石墨烯在空气环境中的热稳定性。结果表明空气环境中热处理可以向石墨烯中引入缺陷,并使其晶粒发生细化;石墨烯表面出现类似于氧化石墨烯表面常见的C=O、C-OH化学键,表明空气环境中热处理后的石墨烯发生轻微的氧化作用;石墨烯在加热与冷却过程中,由于与衬底的热膨胀系数失配引起其内应力的释放,在一定程度上改善了石墨烯的表面形貌。另外,由于热氧化后的石墨烯表面的化学活性有了一定程度的增加,使得其表面能增大。这些结果将对石墨烯基器件在高温环境下工作的稳定性研究提供一定的理论基础。在石墨烯的热稳定性研究的基础上,结合基于AFM的纳米力学测试技术,根据纳米摩擦学理论以及接触力学的最新研究成果,深入探讨利用热氧化法调控石墨烯表面纳米摩擦学特性的基本原理及可行性。详细介绍了AFM在纳米摩擦学测试领域的原理及应用,并对热氧化前后的石墨烯样品进行纳米摩擦学测试。文中深入分析了样品表面粗糙度对测试结果的影响。实验结果表明热氧化的石墨烯表面的摩擦力明显增加。利用针尖与样品之间的接触理论研究表明,热氧化石墨烯降低的杨氏模量是其表面摩擦力显著增加的主要原因。另外,热氧化后的石墨烯表面呈现出类似于氧化石墨烯的亲水性能,从而引起其表面粘附力的显著增加。这些结果为石墨烯表面力学特性的调控提供了新思路,对石墨烯在微机械制造、装配和纳米润滑等领域中的应用提供了理论依据。
[Abstract]:Graphene is a new two-dimensional material with only one layer of carbon atom. It has hexagonal honeycomb lattice structure and quantum Hall effect at room temperature due to its high electron mobility. Excellent physical and chemical properties such as high thermal conductivity and light transmittance are well known around the world. Researchers at home and abroad generally think that graphene can replace silicon as the basic material of the new generation semiconductor devices, and has extensive research and application value. However, in the application of graphene, there are still many theoretical problems to be solved. For example, the study of the thermal stability of graphene has important guiding significance for the design of graphene based devices and the requirements of stability in practical applications. In addition, because graphene has a high specific surface area, some of the forces related to its surface are significantly enhanced, and extremely sensitive to the surrounding environment, so the study of different environments, The surface effect of graphene is very important for the fabrication and assembly of graphene based devices. In this paper, the main physicochemical properties, applications, preparation methods and microstructure characterization of graphene are introduced in detail, and the research status of thermal stability and nano-tribological properties of graphene at home and abroad are discussed. Graphene samples were prepared by chemical vapor deposition (CVD) method by comparing and analyzing the main methods of graphene preparation. The experimental samples were characterized by optical microscope, atomic force microscope (AFM), laser confocal Raman spectroscopy (Ram) and X-ray photoelectron spectroscopy (XPS), which laid a foundation for further experiments. The thermal stability of monolayer graphene prepared by CVD method in air environment was studied by means of Raman X PSN AFM. The results show that the defects can be introduced into graphene by heat treatment in air, and the grain size of graphene can be refined. The results show that the graphene after heat treatment in air has a slight oxidation and the internal stress is released due to the mismatch of thermal expansion coefficient with the substrate during the heating and cooling of graphene. The surface morphology of graphene was improved to some extent. In addition, the surface energy of graphene was increased due to the increase of the surface chemical activity of the thermally oxidized graphene. These results will provide a theoretical basis for the study of the stability of graphene based devices at high temperature. Based on the study of thermal stability of graphene, combined with the nano-mechanical testing technology based on AFM, according to the theory of nano-tribology and the latest research results of contact mechanics, The basic principle and feasibility of controlling nano-tribological properties of graphene surface by thermal oxidation were discussed. The principle and application of AFM in nano-tribological testing are introduced in detail. The nano-tribological tests of graphene samples before and after thermal oxidation are carried out. The influence of the surface roughness of the sample on the test results is analyzed in depth. The experimental results show that the friction on the surface of graphene is obviously increased. The theoretical study on the contact between the tip and the sample shows that the decrease of Young's modulus of graphene oxide is the main reason for the obvious increase of the surface friction. In addition, the surface of graphene after thermal oxidation exhibits hydrophilicity similar to that of graphene oxide, which leads to a significant increase in the surface adhesion of graphene. These results provide a new idea for the control of the surface mechanical properties of graphene and provide a theoretical basis for the application of graphene in the fields of micro-mechanical fabrication, assembly and nano-lubrication.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ127.11

【共引文献】