本文采用分子动力学模拟，对石墨烯带（一维）、石墨烯片（二维）的热学和力学性质进行了研究。 石墨烯是由单层碳原子组成的纳米材料，具有优良的热学和力学性质。石墨烯被认为是世界上最硬的材料，其硬度是钢铁的200倍。为了使石墨烯能够应用在热导率可调节的热管理系统中，我们利用非平衡态分子动力学的方法研究了石墨烯带的热导率在不同应变情况下的变化。通过计算发现，石墨烯带的热导率对拉伸很敏感，在压缩应变下石墨烯的热导率变化很小。我们通过在不同应变（拉伸、压缩）情况下石墨烯的键长、键角以及其声子谱的态密度的变化对石墨烯在应变下热导率变化趋势作出了解释。 无缺陷的碳纳米管和石墨烯虽然具有良好的力学性质，但...In this dissertation, we have studied the thermal and mechanical properties of graphene (two-dimensional) and carbon nanotube (one-dimensional) materials. For the study of mechanical properties of graphene nanoribbons, a new nanostructure is proposed in this dissertation, namely, knitted graphene-nanoribbon sheet (KGS), which consists of zigzag and/or armchair graphene nanoribbons. The knitting te...学位：理学博士院系专业：物理与机电工程学院物理学系_理论物理学号：1982009015366

魏宁

Xiamen University Institutional Repository

   学校编码：10384                                分类号      密级       学号：19820090153661                                       UDC              博  士  学  位  论  文     石墨烯的力学和热学性质的分子动力学模拟 Mechanical and thermal properties of graphene: A molecular dynamics investigation   魏 宁     指导教师姓名：   郑金成 教授 专  业 名 称：   理 论 物 理 论文提交日期：   2012 年 6 月 论文答辩时间：   2012 年 7 月 学位授予日期：   2012 年   月      答辩委员会主席：           评    阅    人：           厦门大学博硕士论文摘要库   2012 年 7 月 厦门大学博硕士论文摘要库  厦门大学博硕士论文摘要库  厦门大学学位论文原创性声明 本人呈交的学位论文是本人在导师指导下,独立完成的研究成果。本人在论文写作中参考其他个人或集体已经发表的研究成果，均在文中以适当方式明确标明，并符合法律规范和《厦门大学研究生学术活动规范（试行）》。 另外，该学位论文为（                            ）课题（组）的研究成果，获得（               ）课题（组）经费或实验室的资助，在（               ）实验室完成。（请在以上括号内填写课题或课题组负责人或实验室名称，未有此项声明内容的，可以不作特别声明。）  声明人（签名）：                       年   月   日 厦门大学博硕士论文摘要库  厦门大学博硕士论文摘要库  厦门大学学位论文著作权使用声明 本人同意厦门大学根据《中华人民共和国学位条例暂行实施办法》等规定保留和使用此学位论文，并向主管部门或其指定机构送交学位论文（包括纸质版和电子版），允许学位论文进入厦门大学图书馆及其数据库被查阅、借阅。本人同意厦门大学将学位论文加入全国博士、硕士学位论文共建单位数据库进行检索，将学位论文的标题和摘要汇编出版，采用影印、缩印或者其它方式合理复制学位论文。 本学位论文属于： （     ）1.经厦门大学保密委员会审查核定的保密学位论文，于   年  月  日解密，解密后适用上述授权。 （     ）2.不保密，适用上述授权。 （请在以上相应括号内打“√”或填上相应内容。保密学位论文应是已经厦门大学保密委员会审定过的学位论文，未经厦门大学保密委员会审定的学位论文均为公开学位论文。此声明栏不填写的，默认为公开学位论文，均适用上述授权。）  声明人（签名）：                       年   月   日 厦门大学博硕士论文摘要库  厦门大学博硕士论文摘要库厦门大学博硕士论文摘要库 I摘 要本文采用分子动力学模拟，对石墨烯带（一维）、石墨烯片（二维）的热学和力学性质进行了研究。 石墨烯是由单层碳原子组成的纳米材料，具有优良的热学和力学性质。石墨烯被认为是世界上 硬的材料，其硬度是钢铁的 200 倍。为了使石墨烯能够应用在热导率可调节的热管理系统中，我们利用非平衡态分子动力学的方法研究了石墨烯带的热导率在不同应变情况下的变化。通过计算发现，石墨烯带的热导率对拉伸很敏感，在压缩应变下石墨烯的热导率变化很小。我们通过在不同应变（拉伸、压缩）情况下石墨烯的键长、键角以及其声子谱的态密度的变化对石墨烯在应变下热导率变化趋势作出了解释。 无缺陷的碳纳米管和石墨烯虽然具有良好的力学性质，但是由于其单层原子结构特征，力学性能表现对缺陷、位错、预应变等很敏感。我们研究了由石墨烯带编织成的石墨烯片的力学性质。为了研究石墨烯带之间成键对其力学性质的影响，我们考虑了石墨烯带边缘用氢钝化和没有钝化两种情况。通过计算发现，边缘用氢钝化的情况下编织的石墨烯片的力学性质甚至超过了没有编织的石墨烯带的力学性质，相反边界没有被氢钝化的情况下编织的石墨烯片的力学性质就比较差。 我们通过计算每个碳原子上的应力来得到整个编织的石墨烯片的应力分布并解释了这个结果。 本文还运用非平衡态分子动力学模拟研究了在富勒烯嵌入（10,10）碳纳米管的模型里，富勒烯在不同热流情况下的动力学行为。利用热泳力的原理，在碳纳米管上构造了由温度梯度形成的一维势垒。理论上，可以通过操纵冷、热源的位置来控制碳纳米管内富勒烯的位置。 我们 后总结和展望了关于石墨烯和碳纳米管的力学和热学性质研究。随着石墨烯和碳纳米管在应用上的广泛使用和发展，我们相信石墨烯和碳纳米管的力厦门大学博硕士论文摘要库                                        II  学和热学性质在未来将引起更加广泛的了解和重视。 关键词：石墨烯；热导率；力学性质                厦门大学博硕士论文摘要库 IIIAbstract In this dissertation, we have studied the thermal and mechanical properties of graphene (two-dimensional) and carbon nanotube (one-dimensional) materials. For the study of mechanical properties of graphene nanoribbons, a new nanostructure is proposed in this dissertation, namely, knitted graphene-nanoribbon sheet (KGS), which consists of zigzag and/or armchair graphene nanoribbons. The knitting technology is introduced to graphene nanotechnology to produce large area graphene sheets. Compared with pristine graphene, the chirality of a knitted graphene-nanoribbon sheet is much more flexible and can be designed on demand. The mechanical properties of KGS are investigated by molecular dynamics simulations, including the effect of vacancies. With hydrogen atoms saturating the ribbon edges, the structure (KGS+H) is found to be of significant mechanical robustness, whose fracture does not rely on the critical bonds. The fracture strain of KGS+H remains nearly unchanged as long as there keeps a single defect-free graphene nanoribbon in the tensile direction. This graphene nano knitting technique is experimentally feasible inspired by a recent demonstration, by Fournier et al [Phys. Rev. B, (2011) 84, 035435] of lifting a single molecular wire using a combined frequency-modulated atomic force and tunnelling microscope. Graphene is an outstanding material with ultrahigh thermal conductivity. Its thermal transfer properties under various strains are studied by reverse nonequilibrium molecular dynamics. Based on the unique two-dimensional structure of graphene, the distinctive geometries of graphene sheets and graphene nanoribbons with large flexibility and their intriguing thermal properties are demonstrated under strains. For example, the corrugation under uniaxial compression and helical structure under light torsion, as well as tube-like structure under strong torsion, exhibit enormously 厦门大学博硕士论文摘要库                                        IV  different thermal conductivities. The important robustness of thermal conductivity is found in the corrugated and helical configurations of graphene nanoribbons. Nevertheless, thermal conductivity of graphene is very sensitive to tensile strain. The relationship among phonon frequency, strain and thermal conductivity are analyzed. A similar trend line of phonon frequency dependence of thermal conductivity are observed for armchair graphene nanoribbons and zigzag graphene nanoribbons. Such unique thermal properties of graphene nanoribbons under strains suggest their great potentials for nanoscale thermal managements and thermoelectric applications. A method of nano-manipulation was proposed in this dissertation to manipulate nanoparticles through a thermal gradient. The motion of a fullerene molecule enclosed inside a (10, 10) carbon nanotube with a thermal gradient was studied by molecular dynamics simulations. We created a one-dimensional potential valley by imposing a symmetrical thermal gradient inside the nanotube. When the temperature gradient was large enough, the fullerene sank into the valley and became trapped. The escaping velocities of the fullerene were evaluated based on the relationship between thermal gradient and thermophoretic force. We then introduced a new way to manipulate the position of nanoparticles by translating the position of thermostats with desirable thermal gradients. Compared to nanomanipulation using a scanning tunneling microscope or an atomic force microscope, our method for nanomanipulation has a great advantage by not requiring a direct contact between the probe and the object. Keywords: Graphene; Thermal conductivity; Mechanical properties. 厦门大学博硕士论文摘要库 V目 录 摘 要 .................................................... I Abstract ............................................... III 第一章  绪论 ....................................... ..- 1 - 1.1 石墨烯的主要特性概述 ................................... - 1 - 1.2 石墨烯的力学性质研究现状 .............................. .- 6 - 1.3 石墨烯的热学性质研究现状 ........................... ...- 11 - 1.4 本论文的主要内容和结构安排 ........................... .- 15 - 1.5 参考文献 .............................................. - 17 - 第二章  编织的石墨烯带的力学性质 ................... .- 23 - 2.1 引言 .................................................. - 23 - 2.2 理论模型和计算方法 .................................... - 25 - 2.2.1 如何编织石墨烯带成为石墨烯片 ...................... - 25 - 2.2.2 模拟方法 .......................................... - 28 - 2.3 结果和讨论 ............................................ - 29 - 2.4 本章小结 .............................................. - 40 - 2.5 参考文献 .............................................. - 43 - 第三章 石墨烯在应变下的热学性质 .................... .- 47 - 3.1 引言 .................................................. - 47 - 3.2 计算方法 .............................................. - 51 - 3.3 计算结果 .............................................. - 55 - 3.4 本章小结 .............................................. - 68 - 3.5 参考文献 .............................................. - 70 - 第四章 非平衡态热泳力的研究 ........................ .- 75 - 4.1 引言 .................................................. - 75 - 4.2 模型和计算方法 ........................................ - 77 - 4.3 结果和讨论 ............................................ - 79 - 4.4 本章小结 .............................................. - 88 - 4.5 参考文献 .............................................. - 90 - 第五章  总结和展望 ................................. .- 93 - 厦门大学博硕士论文摘要库                                        VI  5.1 总结 .................................................. - 93 - 5.2 对未来工作的展望 ...................................... - 94 - 附录： 攻读博士学位期间发表论文 ................... ..- 97 - 致谢 ............................................... .- 98 -   厦门大学博硕士论文摘要库 VIITable of Contents Abstract in Chinese……………………………..……….………………I Abstract in English…………………………...……………………….III Chapter1  Introduction ······················································ 1 1.1 Properties of graphene ··································································· 1 1.2 Mechanical properties of graphene ··················································· 6 1.3 Thermal properties of graphene ····················································· 11 1.4 The main content and structural arrangements  ································ 15 1.5 References  ·············································································· 17 Chapter 2  Mechanical properties of knitted graphene sheet ······· 23 2.1 Introduction ············································································· 23 2.2 Modeling and methodology ··························································· 25 2.3 Results and discussions ································································ 29 2.4 Conclusions  ············································································· 40 2.5 References  ·············································································· 43 Chapter 3 Thermal properties of graphene under various strains ·· 47 3.1 Introduction ············································································· 47 3.2 Modeling and methodology ··························································· 51 厦门大学博硕士论文摘要库                                        VIII  3.3 Results  ··················································································· 55 3.4 Conclusions  ············································································· 68 3.5 References  ·············································································· 70 Chapter 4  Thermophoresis under NEMD  ···························· 75 4.1 Introduction ············································································· 75 4.2 Modeling and methodology ··························································· 77 4.3 Results  ··················································································· 79 4.4 Conclusions  ············································································· 88 4.5 References  ·············································································· 90 Chapter 5  Summary and outlook ········································ 93 5.1 Summary……………………………...………………………………………..93 5.2 Outlook………………………………………………………………………...94 Publications····································································· 97 Acknowledgment ······························································ 98厦门大学博硕士论文摘要库Degree papers are in the “Xiamen University Electronic Theses and Dissertations Database”. Fulltexts are available in the following ways: 1. If your library is a CALIS member libraries, please log on http://etd.calis.edu.cn/ and submitrequests online, or consult the interlibrary loan department in your library. 2. For users of non-CALIS member libraries, please mail to etd@xmu.edu.cn for delivery details.厦门大学博硕士论文摘要库

Mechanical and thermal properties of graphene: A molecular dynamics investigation

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Mechanical and thermal properties of graphene: A molecular dynamics investigation

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