碳纳米管力学行为研究的新进展

详细介绍了碳纳米管的独特结构、性能及其在力学方面的应用,并从试验研究与计算仿真两个方面较全面的综述了国内外学者在该领域的研究现状及最新研究方法。综述结果表明:碳纳米管力学行为的试验与仿真研究主要表现在采用不同的试验方法与势函数对其弹性模量、抗剪强度、抗拉强度等参数进行测试与计算仿真,分析了这些方法用于研究碳纳米管力学行为的优缺点。从分析中可得出:采用合理的描述C-C共价键的势函数对碳纳米管的力学行为进行分子动力学仿真,是一种易于实现并行之有效的方法。     

连续介质理论在研究碳纳米管力学性能中的应用进展

综述连续介质理论在微尺度力学，尤其是在碳纳米管力学性质研究中的应用及进展。介绍近期发展的用于模拟碳纳米管力学行为的各种连续介质模型的理论框架与典型算例。重点阐明各连续介质模型实现宏微观关联的基本思想，详述碳纳米管的桁架模型、Yakobson和Ru等人的壳模型(shell model)、Arroyo和Belytschko的薄膜模型(membrane model)以及Tadmor、Ortiz和Phillips的准连续介质理论；归纳、总结这些理论模型的基本假设、主要结论及其局限性；分析指出它们所涉及的理论推导与数值算法中的一些关键因素；简要介绍这些理论在微尺度力学中的应用。最后，预测连续介质理论应用于微尺度现象分析的发展趋势，指出今后的研究方向。     

微尺度实验力学研究中微拉曼光谱技术的应用分析

对光栅色散型拉曼光谱仪进行了介绍,对碳纳米管纤维材料多尺度结构进行了分析,并利用宏观拉伸试验、原位微拉曼试验等对碳纳米管纤维进行多尺度试验,研究了微拉曼光谱技术在微尺度实验力学中的应用。     

纳米增强体在镁基复合材料中的应用现状

对近年来国内外有关纳米增强体在镁基复合材料中的应用进行了综述,着重介绍了SiC、Y_2O_3、Al_2O_3、AlN等纳米颗粒以及碳纳米管对镁基复合材料显微组织和力学性能的影响,并对相关的增强机理进行了归纳和总结;针对目前纳米增强体强化镁基复合材料研究领域存在的问题,对该领域今后的研究方向进行了展望。     

碳纳米管增强聚合物复合材料的界面脱黏及应力分布

碳纳米管和复合材料基体间的界面力学行为是影响复合材料宏观力学性能的重要因素,为此本文利用有限单元法对单壁碳纳米管增强聚合物复合材料的界面脱黏、切应力分布及拔出载荷进行了数值模拟。建立了一个轴对称三圆柱壳模型,引入ABAQUS中的Cohesive单元模拟了单壁碳纳米管和聚合物基体之间的界面层,分析了单壁碳纳米管的长细比、界面强度以及热残余应力等因素对碳纳米管与聚合物基体间的界面切应力以及拔出载荷的影响。模拟结果表明：当单壁碳纳米管的长度变化为50~100 nm、与基体之间的界面强度为50~100 MPa、环境温度变化为100℃ 时,碳纳米管的长细比、界面强度以及由于热失配所引起的残余应力对单壁碳纳米管与聚合物基体间的界面切应力以及拔出载荷有着显著的影响。     

关于异形簧—锁圈（锁销环）的优化设计计算

本文介绍了异形簧－锁圈（锁销环）在装配和使用工况时的力学特征，对锁圈结构形状参数与力学特征之间的关系进行了分析，推导，论证。并着重对锁圈结构形状参数的优化设计及其在使用状态时力的计算公式和应力校核公式进行了推导，论证。     

碳纳米管填充多孔聚合物材料含油性能研究

基于碳纳米管所特有的表面效应、管状结构以及极高的力学强度,将碳纳米管引入到多孔聚合物材料中,采用冷压烧结方法成功制备出不同碳纳米管含量的多孔聚酰亚胺聚合物材料,并对聚合物材料的孔隙性能、微观结构和含油性能进行研究。结果表明:碳纳米管的加入对多孔聚合物材料的孔隙率有一定的提高,填充碳纳米管的多孔聚酰亚胺聚合物材料孔隙率最高达到了42.2%;碳纳米管可以粘附在聚酰亚胺微球表面,有助于提高聚合物孔隙表面的吸附性能;与不含碳纳米管的多孔聚合物材料相比,添加碳纳米管后材料的含油率和含油保持率有较大的提高。     

X型碳纳米管的可见光吸收特性研究

为了探索X型碳纳米管的介电性质和可见光吸收性质,建立了手性矢量分别为(5,5)和(8,0)的碳纳米管交合的X型碳纳米管模型。采用基于密度泛函的平面波赝势法对其进行几何结构优化和光学性质探索,运用广义梯度近似理论超软赝势对交换相关能进行近似。计算结果表明被交合而成的碳纳米管的介电常数曲线和可见光吸收曲线的峰值大小和峰值位置均发生了变化,这是因为碳纳米管结构的变化导致碳原子间的能级发生改变,从而改变了光子跃迁能量和吸收光子的波长。     

溶剂对碳纳米管/环氧树脂复合材料力热性能的影响

制备了碳纳米管／环氧树脂复合材料，分析了分散碳纳米管的溶剂对复合材料热学，力学行为的影响。溶剂效应由大到小依次为DMF，乙醇和丙酮，与三种溶剂的沸点顺序一致。溶剂效应被认为是未挥发完全的残留溶剂对环氧树脂固化反应的影响，从而导致了固化机理的不同。FTIR通过对比不同溶剂分散的复合材料的分子结构，证明了溶剂效应与复合材料中未反应完的环氧树脂及固化反应的完全程度有关，因而导致了不同的热、力学行为。     

碳纳米管的电子输运性

单壁碳纳米管存在非常有发展前景的电子输运性质。碳纳米管应用于制造场效应晶体管，可获得比硅基器件更高的驱动电流和跨导。然而一个主要悬而未决的问题就是接触电阻对传输性能的影响。这方面已有大量的实验和理论工作，然而实验工作只是局限于测量以源一漏间的电压和门电压为函数的电流，却没有提供对碳纳米管掺杂行为带来的电子空间扩展方面的信息。     

纳米实验力学中的相关测试技术

材料纳观力学特性与纳米材料力学特性的测试是纳米实验力学的基本内容。本文对纳米硬度技术、纳米云纹技术、扫描力显微镜(SFM)技术等主要的几种纳米实验力学测试技术进行概述,然后对目前纳米碳管力学特性试验测试的若干方法进行介绍。     

Wear Behavior of Multiwalled Carbon Nanotube/AZ31 Composite Obtained by Friction Stir Processing

Multiwalled carbon nanotubes were homogenously dispersed into a magnesium alloy (AZ31) using friction stir processing. The microstructural features, mechanical behaviors including microhardness, and wear properties were investigated. The results showed a significant improvement in wear resistance in the friction stir-processed AZ31 alloy containing multiwalled carbon nanotubes compared to that of the as-received alloy. This was attributed to its higher microhardness and lower coefficient of friction due to the presence of finer matrix grains and uniform dispersion of multiwalled carbon nanotubes.     

Fluid-solid interaction in electrostatically actuated carbon nanotubes

This paper deals with investigation of fluid flow on static and dynamic behaviors of carbon nanotubes under electrostatic actuation. The effects of various fluid parameters including fluid viscosity, velocity, pressure and mass ratio on the deflection and pull-in behaviors of the cantilever and doubly clamped carbon nanotubes are studied. Furthermore, the effects of temperature variation on the static and dynamic pull-in voltages of the doubly clamped carbon nanotubes are reported. The results reveal that altering the fluid parameters significantly changes the mechanical and pull-in behaviors. Hence, the proposed system can be applied properly as a nano fluidic sensor to sense the various parameters of the fluid.     

Analytical and numerical investigation into the longitudinal vibration of uniform nanotubes

In recent years, prediction of the behaviors of micro and nanostructures is going to be a matter of increasing concern considering their developments and uses in various engineering fields. Since carbon nanotubes show the specific properties such as strength and special electrical behaviors, they have become the main subject in nanotechnology researches. On the grounds that the classical continuum theory cannot accurately predict the mechanical behavior of nanostructures, nonlocal elasticity theory is used to model the nanoscaled systems. In this paper, a nonlocal model for nanorods is developed, and it is used to model the carbon nanotubes with the aim of the investigating into their longitudinal vibration. Following the derivation of governing equation of nanorods and estimation of nondimensional frequencies, the effect of nonlocal parameter and the length of the nanotube on the obtained frequencies are studied. Furthermore, differential quadrature method, as a numerical solution technique, is used to study the effect of these parameters on estimated frequencies for both classical and nonlocal theories.     

管状波导−单壁碳纳米管太赫兹透射光谱研究

单壁碳纳米管是新一代透明导电材料，具有许多特殊的光学、电学和机械特性，在多种领域应用广泛。为此通过电弧法制备了单壁碳纳米管并进一步与有机玻璃（PMMA）管状波导集成，经实验和模拟研究了基于管状波导的单壁碳纳米管太赫兹透射光谱特性。研究结果表明，单壁碳纳米管可以使管状波导的太赫兹共振增强，可有效提高共振消光比，而石墨烯和炭黑对管状波导的太赫兹透射光谱几乎没有影响。     

Process optimization for PA12/MWCNT nanocomposite manufacturing by selective laser sintering

Nanocomposites produced through the addition of carbon nanotubes to a polymeric matrix can improve the material properties. The mobility of the polymer chains is usually affected, and this is also related to the properties. Parts produced with the free-form fabrication process using the selective laser sintering (SLS) technique can be used in different high-performance applications as they do not require expensive tools for their manufacture. A specific field of interest is the aerospace industry which is characterized by a low production volume and the need for materials with a high performance to weight ratio. In this study, the free-form fabrication by SLS of parts made from nanocomposites comprised of polyamide 12 and multiwalled carbon nanotubes (MWCNTs) was investigated. Specimens were manufactured by SLS to identify the appropriate processing parameters to achieve high mechanical properties for aerospace applications. Laser energy density was adjusted to improve the material density, flexural modulus, and stress at 10 % elongation. Design of experiments was used to identify and quantify the effects of various factors on the mechanical properties. The results obtained showed that there was a limit to the amount of MWCNTs which could be mixed with the polyamide powder to improve the mechanical properties since a higher content affected the laser sintering process.     

Predictive carbon nanotube models using the eigenvector dimension reduction (EDR) method

It has been reported that a carbon nanotube (CNT) is one of the strongest materials with its high failure stress and strain. Moreover, the nanotube has many favorable features, such as high toughness, great flexibility, low density, and so on. This discovery has opened new opportunities in various engineering applications, for example, a nanocomposite material design. However, recent studies have found a substantial discrepancy between computational and experimental material property predictions, in part due to defects in the fabricated nanotubes. It is found that the nanotubes are highly defective in many different formations (e.g., vacancy, dislocation, chemical, and topological defects). Recent parametric studies with vacancy defects have found that the vacancy defects substantially affect mechanical properties of the nanotubes. Given random existence of the nanotube defects, the material properties of the nanotubes can be better understood through statistical modeling of the defects. This paper presents predictive CNT models, which enable to estimate mechanical properties of the CNTs and the nanocomposites under various sources of uncertainties. As the first step, the density and location of vacancy defects will be randomly modeled to predict mechanical properties. It has been reported that the eigenvector dimension reduction (EDR) method performs probability analysis efficiently and accurately. In this paper, molecular dynamics (MD) simulation with a modified Morse potential model is integrated with the EDR method to predict the mechanical properties of the CNTs. To demonstrate the feasibility of the predicted model, probabilistic behavior of mechanical properties (e.g., failure stress, failure strain, and toughness) is compared with the precedent experiment results.     

碳纳米管/金属复合材料的研究现状与动向

碳纳米管/金属复合材料具有优异的理化和力学性能。综述了碳纳米管金属基复合材料的国内外研究现状,分析了制约碳纳米管金属基复合材料广泛应用的因素,即碳纳米管的分散状态及其与金属基体的界面结合问题。最后,对制备碳纳米管金属基复合材料存在的问题及今后的研究动向进行了分析。