碳纳米管与有机小分子官能团相互作用的分子动力学研究

利用Material Studio软件先对不同半径的碳纳米管进行结构优化,再对优化后的纳米管进行分子动力学模拟。得到如下结论：经过优化后小半径纳米管结构基本不变,但是随着半径增大纳米管形变越来越明显。同时通过对多根管簇研究后发现也有相似动力学特性。在以上纳米管结构外面加上一定密度随机排列的对苯二甲酸二辛酯（DOTP）有机分子,发现DOTP有机分子与不同结构、不同半径的纳米管之间都存在相互作用,纳米管半径越大相互作用力也越大,同时DOTP分子在纳米管周围排列也逐渐从无序趋于有序。通过计算以上结构的径向分布函数（RDF）等热力学特性,定性和定量地验证了以上结果。     

碳纳米管的结构、对称性及晶格动力学

本文介绍了单层碳纳米管的结构,对称性和晶格动力学,描述了单层碳纳米管结构的表征方式,碳纳米管的晶格振动模的对称性分类和声子色散曲线。     

Molecular Dynamics Study of Effects of Si-Doping Upon Structure and Mechanical Properties of Carbon Nanotube

In this paper, a Si-doped single-walled carbon nanotube (SWCNT) (7,7) and several perfect armchair SWCNTs are investigated using the classical molecular dynamics simulations method. The inter-atomic short-range interaction is represented by empirical Tersoff bond order potential. The computational results show that the axial Young's modulus of the perfect SWCNTs are in the range of 1.099 ± 0.005 TPa, which is in good agreement with the existing experimental results. From our simulation, the Si-doping decreases the Young's modulus of SWCNT, and with the increased strain levels, the effect of Si-doped layer in enhancing the local stress level increases. The Young's modulus of armchair SWCNTs are weakly affected by tube radius.     

一种高效的用含水乙醇制备单壁碳纳米管的方法

本文采用流化床反应器,利用MgO作为催化剂载体,以Mo和Fe为催化剂。让Ar气流携带含水的乙醇蒸汽进入反应器,通过化学气相沉积(CCVD)法合成了单壁碳纳米管(SWCNTs)。利用拉曼光谱和透射电镜(TEM)对所合成的单壁碳纳米管质量进行检测。实验结果表明无水乙醇中加入7%的水反应温度在950℃时,制备的单壁碳纳米管的质量最好而且管径分布非常均匀。     

热激励下碳纳米管与水混合体系传质传热的分子动力学模拟

爆发沸腾换热和纳米流体传热具有很重要的理论和实用意义.但由于爆发沸腾传热过程中,液体内部空间温度梯度大,相变速度快,表现出一定的特殊性,纳米流体传热对其传热过程机理的研究,往往需要在实验条件难以实现的空间和时间极限下,充分研究液相和气相内部的温度、压力和运动状态及其空间分布.采用分子动力学的方法,通过对比研究纯水和碳纳米管/水混合体系爆发沸腾过程,对两种体系密度分布、温度场和应力场研究和对比分析,揭示碳纳米管/水混合体系的强化换热机理,探究碳纳米管对混合体系爆发沸腾换热和纳米流体传热的促进作用.     

单壁碳纳米管的快速、高效提纯方法研究

本文采用改进的流化床装置对碳纳米管进行空气氧化处理、浓盐酸浸泡处理、空气氧化、浓盐酸浸泡组合处理, 利用扫描电镜和拉曼光谱方法检测了四种处理方法对碳纳米管提纯的效果, 结果发现, 在873 K经空气氧化30分钟, 再用浓盐酸浸泡10分钟, 这种组合处理方法下, 得到的单壁碳管纯度最高, 产率最大。     

Analysis of Single-Walled Carbon Nanotubes Using a Chemical Bond Element Model

提出了一种纳米尺度的有限元方法,碳纳米管中的碳-碳化学键被模拟为键单元．按照平衡关系,根据有限元理论,作用于每个碳原子上的作用力可以写成键单元的刚度矩阵与每个碳原子位移的乘积．在分子力学的基本假设下,键单元刚度矩阵的每个元素可以写为分子力学中力场常数的函数,这样建立起了宏观力学方法(有限元)与纳米尺度力学方法(分子力学)之间的联系．应用该方法模拟了扶椅型与锯齿型单壁碳纳米管的力学行为从而验证了该方法的有效性．分析结果说明单壁碳纳米管的弹性模量与管厚度的选取直接相关．此外,弹性模量对所选取的分子力学中的力场常数非常敏感,管的弹性模量显示出对半径的尺度依赖性,但是管长度对弹性模量的影响小到可以被忽略．     

Molecular Dynamics Simulations of Warm Dense Carbon

We present classical and DFT‐based molecular dynamics (MD) simulations of carbon in the warm dense matter regime (? = 3.7 g/cc, 0.86 eV < T < 8.62 eV [T < 100 eV for classical MD]). Two different classical interatomic potentials are used: 1. LCBOP, designed to simulate condensed (e.g. solid) phases of C, and 2. linearly screened Coulomb (Yukawa) potentials. It is shown that LCBOP over‐predicts minima and maxima in the pair correlation functions of liquid‐C in this regime when compared to the DFT‐MD results. The screened Coulomb model, while under‐correlating at low‐T, seems to produce the correct qualitative features in the static ionic pair distributions at the highest‐T. However, both approaches predict the decay in the ionic contribution of the specific heat as T → ∞ to be much slower than that predicted by a model based on DFT‐MD. These differences in the MD‐derived equations of state in warm dense regimes could have important consequences when using classical inter‐ionic forces such as these in large‐scale MD simulations aimed at studying, for instance, processes of relevance to inertial confinement fusion when C is used as an ablator material. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Molecular Dynamics Simulation of Water Confined in Carbon Nanotubes

Molecular dynamics simulations are performed for water confined in carbon nanotubes with various diameters （11.0-13.8 A ）. The simulations under an isobaric pressure （one atmosphere） by lowering temperatures from 300 K to 190K are carried out. Water molecules within variously sized tubes tend to transform from disorder to order with different configurations （four-water-molecule ring, six-water-molecule ring and seven-water-molecule ring） at phase transition temperatures, which may be lowered by the increasing tube radius. It is also found that the configurations of water in （10, 10） tube are not unique （seven-molecule ring and seven-molecule ring plus water chain）.     

Sieving of H2 and D2 Through End-to-End Nanotubes

We study the quantum molecular sieving of H₂ and D₂ through two nanotubes placed end-to-end. An analytic treatment, assuming that the particles have classical motion along the axis of the nanotube and are confined in a potential well in the radial direction, is considered. Using this idealistic model, and under certain conditions, it is found that this device can act as a complete sieve, allowing chemically pure deuterium to be isolated from an isotope mixture. We also consider a more realistic model of two carbon nanotubes and carry out molecular dynamics simulations using a Feynman-Hibbs potential to model the quantum effects on the dynamics of H₂ and D₂. Sieving is also observed in this case, but is caused by a different process.     

Studies on the Nonisothermal Crystallization Behavior of Polypropylene/Multiwalled Carbon Nanotubes Nanocomposites

Polypropylene/multiwalled carbon nanotubes (PP/MWNTs) nanocomposites were prepared by a melt compounding process. The morphology and nonisothermal crystallization of these nanocomposites were investigated by means of optical microscopy, scanning electron microscopy, and differential scanning calorimetry. Scanning electron microscope micrographs of PP/MWNTs composite showed that the MWNTs were well dispersed in the PP matrix and displayed a clear nucleating effect on PP crystallization. Avrami theory, modified by Jeziorny and Mo's method, was used to analyze the kinetics of the nonisothermal crystallization process. It was found that the addition of MWNTs improved the crystallization rate and increased the peak crystallization temperature of the PP/MWNTs nanocomposites as compared with PP. The results show that the Jeziorny theory and Mo's method successfully describe the nonisothermal crystallization process of PP and PP/MWNTs nanocomposites.     

单壁氮化硼纳米管压缩特性的分子动力学模拟

采用分子动力学方法,分别模拟完好的和含有缺陷的(7,7)扶手椅型氮化硼纳米管的轴向压缩过程.原子间的相互作用采用Tersoff多体势函数来描述.为验证结果的可靠性,同时针对(7,7)扶手椅型碳纳米管进行对比计算.结果表明,氮化硼纳米管的压缩失效模式同碳纳米管相同,均表现为管壁的局部屈曲.发现纳米管的压缩强度,如临界轴向内力在低温下受温度影响明显,并且和应变率的大小有关.然而,应变率对纳米管的弹性变形没有影响.另外,还发现空位缺陷降低了纳米管的力学性能.与完好的纳米管相比,含有缺陷的纳米管轴向压缩强度对于温度的影响并不敏感.     

四氟化碳分子电离解离过程中的异构化动力学

采用离子动量成像谱仪研究了能量为1.0 ke V的电子束碰撞条件下CF₄分子的解离动力学.实验上,对解离离子的三维动量进行了成像测量,通过离子飞行时间关联谱识别了CF₄²⁺异构化生成F₂⁺分子的两个通道:F₂⁺+CF₂⁺与CF⁺+F₂⁺+F,得到了两个通道的离子动能及动能释放分布.对于其中的三体解离通道,我们进一步采用Dalitz图与Newton图等三体动力学分析方法对解离碎片的动量关联进行了分析.该通道以两个带电离子的背对背出射为主,中性的F原子作为旁观者只得到极小的反冲动量.     

甘氨酸在纳米碳管中的吸附及性质的分子模拟

采用分子力学、分子动力学方法模拟研究了甘氨酸分子在单壁纳米碳管中的吸附和扩散行为 ,并对甘氨酸分子在纳米碳管中的构象和能量进行了优化 .模拟计算结果表明 ,甘氨酸在纳米碳管中的构象发生了伸缩和扭转 ,这种构象的改变将会导致氨基酸生物性能的改变 ;纳米碳管对氨基酸分子具有较强的吸附作用 ,其中纳米碳管和甘氨酸分子之间的π -π相互作用增加了纳米碳管对氨基酸的吸附能 .模拟过程中氨基酸分子和纳米碳管之间的运动会保持很强的协同效应 ,使模拟体系构型在能量上处于最稳定的状态     

Study of the Nonisothermal Crystallization Kinetics and Melting Behaviors of Polypropylene Reinforced with Single-Walled Carbon Nanotubes Nanocomposite

Nonisothermal crystallization kinetics of polypropylene (PP) nanocomposite reinforced with 0.5 wt. % single-walled carbon nanotubes (SWNT) was characterized by differential scanning calorimetry at five different cooling and heating rates. The Avrami, Ozawa, and Seo-Kim kinetic models were used to describe the nonisothermal crystallization of the polymer and its nanocomposite. The addition of nano-filler, in general, improved the crystallization rate and increased the peak crystallization temperature of the nanocomposite as compared to PP. The results show that the Avrami and Seo-Kim models are suitable under different cooling rate conditions but that the Ozawa model is inappropriate for the nanocomposite. Equilibrium melting temperatures, derived from the linear Hoffman-Weeks equation, were shown to decrease in the nanocomposite. Additional analysis was performed based on the Thomson-Gibbs, Lauritzen-Hoffman, and Dobreva-Gutzowa theories, which were applied to take into account the lamellar thickness, nucleating agent, and nucleating activity of the nanocomposite in the nonisothermal melt crystallization process.     

BPL－RFQ加速器束流动力学设计研究

描述北京质子直线加速器ＲＦＱ的参数选择及束流动力学设计研究，给出了ＢＰＬ－ＲＦＱ的主要参数．     

Matlab编程的Hückel分子轨道法计算研究掺杂纳米碳管的化学反应性

使用Matlab自编简单Hückel分子轨道法（SHMO）计算程序,分析空位、Stone-Wales缺陷位、N和B原子掺杂的CNT（5,5）碳纳米管,计算π电子密度和前线分子轨道（HOMO和LUMO）为研究掺杂相对碳纳米管的化学反应性提供依据.具有不同电特性的掺杂相打破了碳纳米管的π电子、HOMO和LUMO的均衡分布.掺杂相和/或邻近的碳原子为HOMO或LUMO贡献了较其它原子更大的轨道系数,在不同的化学反应中表现出良好的亲核性或亲电性.此外,HOMO-LUMO能量差很好地反映了掺杂纳米碳管的导电性.计算结果与已报道的实验和理论结果吻合良好.     

以Y/Ni为催化剂制备的单壁碳纳米管的拉曼光谱研究

采用电弧放电法以Y/Ni为催化制备了单壁碳纳米管（SWNTs），对样品进行了扫描电镜、透射电镜和拉曼光谱的研究。所制备的样品中单壁碳纳米管的含量较高。对单壁碳纳米管的共振拉曼散射增强效应进行了观察，随激光波长的不同，单壁碳纳米管的拉曼光谱也随之变化，尤其是低频区径向呼吸模的变化比较明显。利用布里渊区折叠法计算了单壁碳纳米管的电子态密度曲线，根据SWNTs电子态密度尖峰之间的能量差、管子的直径和呼吸模频率建立了一个图表，并对SWNTs的呼吸模进行了归属。分析结果表明：样品中单壁碳纳米管的直径分布在0.79-1.76nm范围，金属管和半导体管均存在，并且直径在1.45nm附近的碳管居多。     

Molecular dynamics simulation of an argon cluster filled inside carbon nanotubes

The effects of the diameters of single-walled carbon nanotubes （SWCNTs） （7.83A to 27.40A） and temperature （20 K-45 K） on the equilibrium structure of an argon cluster are systematically studied by molecular dynamics simulation with consideration of the SWCNTs to be fixed. Since the diameters of SWCNTs with different chiralities increase when temperature is fixed at 20 K, the equilibrium structures of the argon cluster transform from monoatomic chains to helical and then to multishell coaxial cylinders. Chirality has almost no noticeable influence on these cylindrosymmetric structures. The effects of temperature and a non-equilibrium sudden heating process on the structures of argon clusters in SWCNTs are also studied by molecular dynamics simulation.     

单壁碳纳米管受压屈曲行为的数值模拟

采用以Tersoff Brenner势函数来描述碳纳米管中碳原子间的相互作用的分子动力学方法,模拟了单壁 碳纳米管(SWCNTs)的受压屈曲行为.计算结果表明,单壁碳纳米管的杨氏模量随着管径的增大而减小;碳纳米 管屈曲的临界应力和临界应变与碳纳米管细长比有关,不同的细长比决定了碳纳米管结构不同的屈曲模态;碳纳 米管的受压屈曲机理和连续介质力学中柱体壳的受压屈曲理论随细长比的不同而存在一些异同.