石墨纳米片/聚乙烯复合物分子动力学模拟

通过分子动力学模拟对石墨纳米片（GNP）/聚乙烯（PE）复合物的结构、力学和气体输运性质进行计算研究,分析其随模拟温度和GNP填充量的变化规律,探讨纳米界面形成、复合机制及结构与特性的关系。GNP/PE复合物呈现二维结构,GNP趋向于平面取向排列并通过范德华力和纳米石墨片层表面上的碳氢-π键使周围几个原子尺度内的PE分子固化为有序原子层,而PE基体仍然为各向同性的无定形结构。GNP/PE界面上纳米复合作用使体系能量降低,与PE体系相比,GNP/PE的杨氏模量和泊松比分别显著增高和降低。GNP平面取向导致GNP/PE的力学特性表现出二维各向异性的弹性常数张量,在石墨纳米片层平面方向上的杨氏模量明显增高,并且随温度的降低和GNP填充量的提高而增大,填充GNP有效改善了GNP/PE的力学性质。GNP/PE复合物的气体输运性质明显受到填充GNP的气体阻隔和取向的影响并且对3种气体渗透没有明显的选择性。GNP与基体的纳米复合导致N₂、O₂和CO₂的分子输运呈现二维各向异性,随着石墨纳米颗粒填充量的增加,取向GNP层面方向的扩散系数比垂直方向高5~8倍,可用于气体分子屏障与渗流控制。     

聚乙烯热裂解行为的分子动力学模拟

基于AMBER力场,采用周期性边界条件对聚乙烯模化物的热解过程进行了分子动力学模拟,模拟温度为300～1200 K.模拟结果表明,当温度高于600K时,C-C键开始发生断裂,整个分子链发生解聚,形成各种大分子碎片,随着温度的进一步升高,大分子碎片进一步分解成小分子碎片.聚乙烯的热解是典型的无规裂解,运用自由基链反应理论分析了各种热解主要产物的形成机理.     

碳纳米管／导电聚合物纳米复合物的合成与表征

为实现制备出导电性能优良的有机透明导电涂层,需要把具有导电性的碳纳米管在树脂中组装成一体化导电结构网络.运用可以在树脂中自组装的导电聚乙撑二氧噻吩和聚苯胺来实现碳纳米管自组装的方法,分别合成出了导电聚乙撑二氧噻吩和聚苯胺薄膜均匀覆盖的碳纳米管/聚乙撑二氧噻吩复合物与碳纳米管/聚苯胺纳米复合物,并运用透射电镜(TEM)、傅立叶红外光谱(FTIR)和四探针法对其进行了分析与表征,结果发现这种复合物的导电性较碳纳米管和聚乙撑二氧噻吩以及聚苯胺自身导电性都有一定程度的提高.     

碳纳米管增强聚醚醚酮/聚四氟乙烯摩擦学性能分子动力学模拟

基于分子动力学模拟研究方法,构建不同质量分数下碳纳米管(CNT)/聚醚醚酮(PEEK)/聚四氟乙烯(PTFE)复合材料分子体系。采用恒应变法计算复合材料的力学性能和摩擦学性能参数。将CNT官能化,官能团分别为氨基(—NH₂)、酯基(—COOCH₃)和羧基(—COOH),获得相应的力学性能和摩擦学性能参数,探析官能化CNT对PEEK/PTFE界面补强机理。模拟结果表明,加入CNT可以提高PEEK/PTFE基体的力学性能、降低磨损率,其中3%CNT/10%PEEK/PTFE复合材料的摩擦学性能表现最优。官能化CNT的加入在提高复合材料力学性能的同时,摩擦系数和磨损率均有所降低,其中,COOH-CNT/PEEK/PTFE复合材料摩擦学特性最优。文中制备了10%PEEK/PTFE,3%CNT/10%PEEK/PTFE和3%COOH-CNT/10%PEEK/PTFE复合材料,对3种复合材料进行了力学性能测试、摩擦磨损性能及扫描电镜磨损形貌分析。通过试验和分子动力学的双向表征,为PTFE基复合材料的研发和应用扩展提供理论依据。     

不同尺寸的碳纳米管接枝聚酰亚胺复合材料的分子动力学模拟

本工作利用分子模拟软件Materials Studio建立了聚酰亚胺(PI)模型、不同直径的多壁碳纳米管模型(MWCNT)、不同长度的多壁碳纳米管模型(MWCNT)以及MWCNT/PI复合材料模型,探究了不同尺寸的MWCNT对MWCNT/PI复合材料模型的力学性能和玻璃化转变温度(T_g)的影响。计算结果表明,当加入长度为10～20μm、直径为10～20 nm的MWCNT,复合材料MWCNT/PI-1的杨氏模量和剪切模量分别为24.935 4 GPa和7.977 GPa;加入直径为10～20 nm、长度大于50μm的MWCNT后,复合材料MWCNT/PI-7的力学性能提高最为显著,杨氏模量和剪切模量分别为26.671 GPa和9.246 2 GPa。这表明MWCNT的直径越小或长度越长,即长径比增加,其与PI之间的相互作用力越强,从而可提高PI复合材料的力学性能,且MWCNT/PI的玻璃化转变温度升高。     

石墨烯/聚乙烯复合材料致密区间密度变化的分子动力学模拟

石墨烯增强复合材料的性能受到粘结界面,致密区间等多种因素的影响.如果没有考虑到这些因素的影响,在分析石墨烯增强复合材料时可能会导致错误的结果.本文采用分子动力学模拟的方法进行石墨烯/聚乙烯复合材料致密区间密度变化的分析.首先对聚乙烯晶胞进行分子动力学计算,得到的聚乙烯晶胞密度为0.95 g/cm3,与聚乙烯实际密度吻合...     

水分子在碳纳米管中扩散结构的分子动力学模拟

利用分子动力学模拟受限于碳纳米管中的水在不同温度下的结构,在不同温度下观察水在碳纳米管中的结构分布。     

再生聚乙烯中挥发性气味物质扩散的分子动力学模拟

再生聚乙烯中挥发性气味物质的迁移是其用于食品包装的潜在风险之一。本研究使用分子动力学模拟的方法探讨了再生聚乙烯中甲苯、2,4-二甲基庚烷、α-蒎烯、柠檬烯、二苯醚和α-异甲基紫罗兰酮六种挥发性气味物质在不同温度下的扩散行为。通过气味物质分子的均方位移曲线计算了它们的扩散系数,并与实验值和Limm-Hollifield模型值进行了比较。从气味物质的拓扑结构参数、与聚乙烯的相互作用能、扩散活化能以及运行轨迹等方面分析它们的扩散行为。结果表明,这六种挥发性气味物质的扩散受多种因素综合影响。具有较大分子体积和回旋半径以及结构为球型的分子运动较为困难,因此有较小的扩散系数;当气味物质分子的溶解度参数与聚乙烯相近时,两者的相容性较好,分子也不容易扩散。从能量角度来说,气味物质与聚乙烯的相互作用能及其扩散活化能越大,分子运动所需的能量越大,扩散过程越缓慢。同一种物质在不同温度下的运动轨迹表现为长时间的振动与短时间的跳跃,但是在高温下的运动范围较大,轨迹点呈现明显的团簇。     

原位聚合法制备碳纳米管/PET复合物及其性能研究

在乙二醇(EG)与对苯二甲酸(PTA)酯化过程中加入经浓HNO3/浓H2SO4(1/3,体积比)氧化处理的多壁碳纳米管(MWCNTs),采用原位聚合法制备了不同MWCNTs含量(质量分数分别为0.2%、 0.6%和1.0%)的MWCNTs/PET纳米复合材料.扫描电子显微镜(SEM)观察发现当MWCNTs含量较低时,其在PET基体中分散良好;Instron 1122力学性能测试表明,经MWCNTs复合后,PET盯样品的拉伸强度与模量都有所提高;差示扫描量热(DSC)分析表明MWCNTs具有成核剂的作用,促进了PET熔体的结晶行为.     

碳纳米管/聚乙烯咪唑纳米复合材料的制备与表征

采用化学改性手段制备了一类新型的碳纳米管／聚乙烯咪唑(CNTs／PVI)纳米复合材料。并通过红外光谱、扫描电镜、透射电镜和X射线衍射等手段表征CNTs／PVI产物。有机杂环聚合物引入碳纳米管材料体系以后,会显著改善碳纳米管在有机溶剂中的分散均匀性和可加工性,并将碳纳米管具有的优异力学、热稳定性能和杂环聚合物具有的优良溶解性等结合起来,得到一种新型的综合性能优异的光电功能材料。     

Mechanical properties of carbon nanotube by molecular dynamics simulation

The mechanical properties of single-walled carbon nanotube (SWCNT) are computed and simulated by using molecular dynamics (MD) in this paper. From the MD simulation for an armchair SWCNT whose diameter is 1.2 nm and length is 4.7 nm, we get that its Young modulus is 3.62 TPa, and tensile strength is 9.6 GPa. It is shown that the Young modulus and tensile strength of armchair SWCNTs are 12 order higher than those of ordinary metal materials. Therefore we can draw a conclusion that carbon nanotubes (CNT) belong to a particular material with excellent mechanical properties.     

Molecular dynamics simulation on diffusion of 13 kinds of small molecules in polyethylene terephthalate

Understanding the diffusion of migrants in polyethylene terephthalate (PET) and calculating the diffusion coefficients are very important for migration research. In this study, the diffusion coefficients of 13 kinds of small molecules with molecular weights ranging from 32 to 339 g/mol in amorphous PET are calculated based on molecular dynamics (MD) simulation. By comparison of diffusion coefficients simulated by MD simulation techniques, predicted by the Piringer model and by experiments, the accuracy of the Piringer model and MD simulation techniques for the estimation of diffusion coefficients of migrants in PET is evaluated. The MD simulation shows that D_simu is very close to D_exp, within one order of magnitude of the experimental diffusion coefficients except for a few samples. The possible reasons for the differences among D_simu, D_pred and D_exp are analysed from the molecular weight and temperature. The results show that the Piringer‐model‐predicted values at high temperatures overestimate significantly higher than that at lower temperatures. The activation energy is calculated by the Arrhenius equation, which shows the relationship between diffusion coefficient and temperature. It is shown that the MD simulation yields acceptable activation energy. The study suggests that MD simulation may be a useful approach to calculate the diffusion coefficients of small molecules in PET. Copyright © 2010 John Wiley & Sons, Ltd.     

石墨/树状大分子复合材料的分子动力学模拟

在COMPASS(Condensed-phase optimized molecular potentials for atomistic simulation studies)力场下, 对以氨(Amine)、 丁二胺(Butanediamine)为核的1代~3代(1G~3G)石墨/树状大分子纳米复合材料进行了分子动力学模拟(Molecular dynamics simulation)。介绍了复合体系的构建过程及分子动力学模拟细节, 从微观构形、 能量变化研究了正则系综(恒定的NVT)中6种插层复合物的稳定性及其机理, 最后利用径向分布函数(Radial distribution function)对能量变化结果进行了分析。结果表明, 当树状大分子体积较小时, 石墨层容易弯曲, 体系能量较高, 导致复合体系不稳定; 随着树状大分子代数的增加, 石墨层形变减小, 体系能量降低, 3代时树状大分子体系最稳定。      

Molecular dynamics simulation of polarizable carbon nanotubes

This paper is aimed to develop a modified force field for molecular dynamics (MD) simulations of polarizable carbon nanotubes (CNTs). The effects of electrical polarization and the associated electronic degrees of freedom are represented by a network of negative charged shell particles which move relative to the surrounding positively charged carbon atoms in response to an applied electric field. In this setting, the negative and positive charges are exactly balanced so that the total system remains electrically neutral, and the motion of the shell particles relative to their equilibrium positions leads to polarization within the nanotube. Potential applications of the proposed model include simulations of controlled translocation of ions, water and polymers through solid-state CNT membranes.     

Load transfer of graphene/carbon nanotube/polyethylene hybrid nanocomposite by molecular dynamics simulation

Load transfer of the graphene/carbon nanotube (CNT)/polyethylene hybrid nanocomposite is studied here from molecular dynamics (MD) simulations. Simulations of this composite material under uniaxial tension were conducted by varying CNT’s position and diameter in the polymer matrix. The obtained results show that: (1) The peak strength of stress and strain evolution in the polymer matrix is lower than the peak strength of the graphene/graphene and graphene/polymer interfaces. Hence, the damage zone is always located in the polymer matrix. (2) Agglomerated two-layer graphenes do not possess an increased value in the peak strength compared with single-layer graphene-reinforced polymer nanocomposite (PNC), while two separate layers of graphene show slightly higher peak strength. (3) The largest peak strength is observed before CNT moves to the center of the polymer matrix. The damage location moves from the upper to the lower part of CNT when the CNT is located at the centre of polymer matrix. (4) The influence of the CNT diameter on the peak strength is not obvious, while the damage location and shape in the polymer matrix changes with respect to varying CNT diameters. In addition, the damage zone always falls outside the interphase zone.     

聚对苯二甲酸乙二醇酯/多壁碳纳米管复合材料制备与性能研究

通过微型双螺杆挤出机熔融共混制备了聚对苯二甲酸乙二醇酯(PET)/碳纳米管(CNT)复合材料。采用表面电阻仪、场发射扫描电镜(FESEM)和差示扫描量热仪(DSC)研究了多壁碳纳米管(MWNT)和羧基化多壁碳纳米管(MWNT-COOH)对复合材料导电性能与结晶性能的影响。结果表明,当CNT含量1%(质量分数)时,CNT在PET中形成三维导电网络,复合材料具有抗静电和导电功能,MWNT-COOH分散性好,与PET有较强的界面结合和相互作用,复合材料的导电性优于PET/MWNT。复合材料的结晶放热峰温度大幅提高,比PET高40多℃,0.1%(质量分数)含量的CNT就有非常明显的异相成核与诱导结晶作用。同时,复合材料的结晶度增加,熔点略微升高。     

聚苯胺/碳纳米管复合物的制备及其工艺研究

以低温原位静置法制备了聚苯胺包覆碳纳米管复合物,考察了碳纳米管含量和掺杂酸种类2个工艺参数对复合物的形貌、热稳定性、吸波性能的影响。研究表明:碳纳米管含量为10%时,两者完全包覆出现类似玉米棒形貌,有机酸掺杂制备出针形的聚苯胺且随单体浓度降低直径变小针状更明显;酸种类参数对热稳定性的影响更大,10%碳纳米管含量对氨基苯磺酸掺杂的样品热稳定性最好;有机酸掺杂样的损耗正切远小于盐酸掺杂样的,以盐酸掺杂的碳管含量为10%的样品在低频处有很好的吸收。     

Molecular Dynamics Study of Radial Corrugation in Carbon Nanotubes

Molecular dynamics simulations of multiwalled carbon nanotubes under hydrostatic pressure are performed to elucidate the novel class of radial buckling in the systems. It is revealed by all-atom simulations that the initial circular cross section transforms into a flower-like wavy configuration at critical pressure on the order of hundreds mega pascals or less. This kind of radial buckling, called radial corrugation, originates from the competition of the three relevant energies in the system: in-plane strain energy, van der Waals interaction energy between adjacent tubes, and out-of-plane bending energy. Their possible consequences for physical properties of carbon nanotubes are also discussed.