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首页> 外文学位 >Analysis of irradiation induced defects on carbon nanostructures and their influences on nanomechanical and morphological properties using molecular dynamics simulation.
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Analysis of irradiation induced defects on carbon nanostructures and their influences on nanomechanical and morphological properties using molecular dynamics simulation.

机译：分子动力学模拟分析了辐照引起的碳纳米结构缺陷及其对纳米力学和形态学特性的影响。

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摘要

Mechanisms such as nanomechanics, changes in chemical structure, and van der Waals interactions are difficult to observe on the atomic scale by experimental methods. It is important to understand the fundamentals of these processes on a small scale to reach conclusions of results that are observed on a larger scale. Computational methods may be readily applied to investigate these mechanisms on models a few nanometers in dimension and the results can give insights to processes that occur during real time experiments. The classical molecular dynamics simulations here utilize the reactive empirical bond-order (REBO) or adaptive intermolecular REBO (AIREBO) potentials, to model short range behavior, coupled with the Lennard Jones potential (and torsion for AIREBO), to model long range interactions of carbon nanostructures and hydrocarbons.;The bond order term in the REBO/AIREBO potential allows for the realistic treatment of these materials as it correctly describes carbon (and silicon and germanium) hybridizations, and allows for bond breaking and reformation unlike basic molecular mechanics. This is a key feature for simulating irradiation and pullout mechanics on graphite and carbon nanotube and their composites.;The irradiation simulations on graphite, with the same conditions as the experimental irradiation of highly pyrolythic graphite, provide insight to the types of defects that were observed on a larger scale by Scanning Transmission Microscopy (STM) images. Experimental characterization from collaborators mapped out the surface of irradiated graphite while computational theory further described the defects and observed the evolution of the defects during the irradiation procedure.;Multi walled carbon nanotubes (MWNT) were irradiated with different particles to compare the effect that incident species have on the nanotubes' surfaces as well as the crosslink distribution of the radial cross sections. Irradiation is a common technique to modify the interfacial areas between the fiber and matrix to improve compatibility in polymer composites. Inducing crosslinks between shells of the MWNT by irradiation drastically decreased the sword in sheath deformation, where inner shells slip out with respect to outer shells, that was computationally demonstrated.;A similar procedure was also carried out on carbon nanotube - polystyrene composites. Argon irradiation was simulated for three different types of nanotubes: double-walled, single-walled, and a bundle of four single-walled nanotubes, in a polystyrene matrix. The polymer emission, depth of particle penetration, and nanotube pullouts were observed, it was shown that the presence of carbon nanotubes limited these processes.;Atomic Force Microscopy (AFM) and X-Ray Diffraction (XRD) images in conjunction with AIREBO molecular dynamics simulation trajectories of C60 and pentacene films of various ratios gave theoretical and experimental insight on the molecular evolution of donor and acceptor aggregation for optimizing the design of effective organic semiconductors.;Atomic-scale simulations are thus shown to be a powerful computational tool to better understand the properties of carbon nanostructures and hydrocarbons. This dissertation illustrates how effective they are for providing insight on chemical modification, nanomechanical deformation, and equilibration mechanisms on the atomic scale.
机译：诸如纳米力学，化学结构变化和范德华相互作用等机制很难通过实验方法在原子尺度上观察到。重要的是要小范围地了解这些过程的基础，以得出大范围观察到的结果的结论。计算方法可以很容易地应用于研究尺寸为几纳米的模型上的这些机制，并且结果可以为实时实验中发生的过程提供深刻见解。这里的经典分子动力学模拟利用反应性经验键序（REBO）或自适应分子间REBO（AIREBO）势来模拟短程行为，并与Lennard Jones势（以及AIREBO的扭转）耦合，以模拟REBO / AIREBO电势中的键序术语可以正确地描述碳（以及硅和锗）的杂化，从而可以对这些材料进行实际处理，并且可以实现不同于基本分子力学的键断裂和重整。这是模拟石墨和碳纳米管及其复合材料的辐照和拉拔力学的关键特征。;在与高热解石墨的实验辐照相同的条件下，对石墨的辐照模拟可提供对观察到的缺陷类型的洞察力通过扫描透射显微镜（STM）图像进行更大规模的测量。合作者的实验表征将辐照石墨的表面绘制出来，而计算理论则进一步描述了缺陷并观察了辐照过程中缺陷的演变。;用不同的粒子辐照了多壁碳纳米管（MWNT），以比较入射物种的影响在纳米管的表面上以及径向截面的交联分布上具有辐照是一种常用的技术，可以改变纤维和基质之间的界面区域，以提高聚合物复合材料的相容性。通过辐照诱导多壁碳纳米管壳之间的交联极大地减少了鞘变形中的剑，鞘的变形使内壳相对于外壳滑落，这在计算上得到了证明。在聚苯乙烯基质中模拟了三种不同类型的纳米管的氩气照射：双壁，单壁和一束四个单壁纳米管。观察到聚合物的发射，粒子穿透的深度和纳米管的拉出，这表明碳纳米管的存在限制了这些过程。原子力显微镜（AFM）和X射线衍射（XRD）图像结合AIREBO分子动力学不同比例的C60和并五苯薄膜的模拟轨迹提供了用于优化有效有机半导体设计的供体和受体团聚分子演化的理论和实验洞察力;因此，原子级模拟被证明是一种有效的计算工具，可以更好地理解碳纳米结构和碳氢化合物的特性。本文说明了它们在提供化学修饰，纳米机械变形和原子尺度平衡机理方面的有效性。

著录项

  • 作者

    Pregler, Sharon Kay.;

  • 作者单位

    University of Florida.;

  • 授予单位 University of Florida.;
  • 学科 Physics Condensed Matter.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 132 p.
  • 总页数 132
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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