碳纳米管的力学性能及碳纳米管复合材料研究

对碳纳米管力学行为和碳纳米管复合材料的研究文献进行了综述.首先介绍了碳纳米管结构稳定性和力学性能的研究进展,包括理论模拟和实验的研究结果.结果表明,碳纳米管有着优异的力学性能,其在复合材料应用方面有着巨大的潜力.然后,系统地总结了碳纳米管在增强高分子材料、金属材料和陶瓷材料方面的应用,指出外场力传递效应是值得关注的课题.最后,对该领域工作做了一些讨论和展望.      

基于粗粒化方法的类超级碳纳米管自由振动研究

超级碳纳米管是在碳纳米管结构基础上，将每一根碳-碳键替换为碳纳米管而形成的新型结构。类超级碳纳米管是超级碳纳米管对应的宏观结构，在保持外观结构的基础上将尺度放大到宏观尺度。本文建立了类超级碳纳米管的粗粒化模型。基于粗粒化方法，研究了类超级碳纳米管的自由振动。分析了内外管半径以及长度对类超级碳纳米管振动行为的影响。与原结构有限元进行对比，结果表明粗粒化方法能有效的计算类超级碳纳米管的振动行为。     

基于粗粒化方法的类超级碳纳米管自由振动研究

超级碳纳米管是在碳纳米管结构基础上，将每一根碳-碳键替换为碳纳米管而形成的新型结构。类超级碳纳米管是超级碳纳米管对应的宏观结构，在保持外观结构的基础上将尺度放大到宏观尺度。本文建立了类超级碳纳米管的粗粒化模型。基于粗粒化方法，研究了类超级碳纳米管的自由振动。分析了内外管半径以及长度对类超级碳纳米管振动行为的影响。与原结构有限元进行对比，结果表明粗粒化方法能有效的计算类超级碳纳米管的振动行为。     

基于辛理论的载流碳纳米管能带分析

基于连续介质力学理论和辛弹性理论,将载流碳纳米管等效为铁木辛柯梁,采用哈密顿变分原理建立了载流碳纳米管的振动控制方程;引入对偶变量将振动控制方程从拉格朗日体系导入到哈密顿体系下;通过波传播方法分析了载流碳纳米管的能带结构;研究了流体密度、流速对载流碳纳米管能带结构的影响;同时计算了载流碳纳米管的散射矩阵. 研究发现:管内流速以及流体密度对剪切频率和弯曲频率有着非常重要的影响. 研究结果表明:载流碳纳米管的剪切频率和弯曲频率因流体的加入而减小,并随流速及流体密度的增大而减小;通过对数值结果的分析发现:载流碳纳米管由于管内流体、流速以及流体密度的作用,会使得载流碳纳米管变的更“软”. 其中,哈密顿体系下所得出的载流碳纳米管弯曲频率随管内流体密度的增加而变小,有别于在拉格朗日体系下非局部梁理论所得的结论. 同时,数值结果表明散射矩阵是酉矩阵,辛体系下的入射波功率流与反射波功率流相等,即功率流守恒,体现了辛弹性力学理论的优越性.      

硅基表面稀土改性碳纳米管/氨基硅烷自组装复合膜的摩擦磨损性能

配置稀土溶液对碳纳米管进行表面改性,采用自组装膜技术在单晶硅表面制备了稀土改性碳纳米管复合薄膜,考察了其表面形貌、化学组成和摩擦学性能。扫描电子显微镜观察发现单晶硅表面附着了大量不规则排列碳纳米管,X射线光电子能谱仪分析发现稀土元素与薄膜表面的磷酸基发生了化学反应,从而使碳纳米管组装到基片表面。UMT-2MT摩擦试验机测试结果表明在给定的试验条件下,复合薄膜的摩擦系数较低,随载荷和速度的增加变化不大。由于稀土改性碳纳米管复合薄膜的存在,与未处理碳纳米管复合薄膜、硅烷薄膜相比,基片表面摩擦系数显著降低,并表现出了优异的耐磨性及摩擦稳定性。     

化学镀耐磨自润滑Ni-P复合镀层的摩擦磨损性能

利用化学复合镀技术制备了Ni-P-碳纳米管(Ni-P-CNTs)和Ni-P-无机类富勒烯WS2[Ni-P-(IF-WS2)]复合镀层,考察了复合镀层的减摩抗磨性能.结果表明,Ni-P-CNTs和Ni-P-(IF-WS2)复合镀层的减摩抗磨性能优于化学镀Ni-P和Ni-P-石墨镀层,其原因在于Ni-P-CNTs化学复合镀层中的碳纳米管具有优异力学性能和同轴石墨纳米管结构,而Ni-P-(IF-WS2)化学复合镀层中的IF-WS2具有封闭层状类富勒烯球形结构,二者均具有优异的自润滑性能.     

碳纳米管应变传感器的性能分析：实验偏振模式的影响机制

碳纳米管作为一种拉曼力学传感介质具有优异的力学性质及共振、偏振拉曼特性。将碳纳米管散布在基体材料中,即可实现局部应力/应变的测量。受到光学衍射极限的限制,常规的远场拉曼光谱得到的是一定区域内众多碳管的平均散射信息。本文综合考虑了采样点内各方向碳管的影响,并对碳管散射的共振状态、碳管的分布状态、拉曼系统的偏振构型及偏振方向等实验因素对碳纳米管应变传感器性能的影响进行了深入分析,采用分峰和重构的方法定量地给出了不同实验模式下采样点内的拉曼信息组成以及各种实验模式的测量精度。分析和对比表明,采用双偏振构型且偏振方向沿荷载施加方向时的测量精度最高,即最优的实验模式。     

单壁碳纳米管的扭转力学特性研究

利用基于高阶Cauchy-Born准则所建立的单壁碳纳米管本构模型,针对不同手性的单壁碳纳米管的扭转力学特性进行了研究.研究发现结构呈现对称性的锯齿型和扶手型单壁碳纳米管具有完全对称的扭转特性,而结构不对称的手性型单壁碳纳米管具有正反相异的扭转特性.同时,针对一系列手性不同的单壁碳纳米管的扭转力学特性展开了详细的研究.研究的部分结果与采用其他方法得到的结果进行了对比,证实了所提出方法以及预测结果的有效性和可行性.     

碳纳米管纤维及其传感器力电性能实验研究

基于UTM T150微纳米力学测试系统搭建了纤维力电耦合测试平台,并对碳纳米管纤维进行了多组力电耦合作用下的拉伸性能实验研究。通过观察分析碳纳米管纤维的电阻-应变曲线,发现其电阻变化与应变大小密切相关,随着应变的不断变大,碳纳米管纤维的电阻也在逐渐增加。基于此,设计制作了碳纳米管纤维柔性应变传感器,并将其贴在标准试件上分别进行了弯曲变形测试、单次/循环加载性能测试以及标定实验。结果表明:当对试件进行加载时,碳纳米管纤维柔性应变传感器的电阻会随着载荷的增大而增大;当载荷逐渐消失时,其电阻会逐渐减小直至回归初始电阻值附近。这表明碳纳米管纤维具备优异的电学与力学特性,并且利用它所制作的柔性应变传感器也有着较好的灵敏度与稳定性。     

低维碳和氮化硼材料的物理力学研究进展

碳纳米管、石墨烯和六方氮化硼等低维材料具有优异的力学和电学性质,已经引起广泛的科学兴趣。然而由电荷、分子轨道、电子结构和自旋态构成的低维材料的局域场与力学变形、机械运动和物理化学环境等外场间往往存在强烈耦合,这导致低维材料会呈现出新颖独特的物理力学性能。论文对近年来碳纳米管、石墨烯和六方氮化硼等低维材料的力学性能、力电耦合与器件原理、表面和界面结构性能调控、层间相互作用、能量耗散和摩擦等物理力学方面的研究进展进行了简要综述,并讨论了利用低维材料多场耦合特性和结构性能关联发展新型功能器件的方法和途径,以及纳米力学和纳尺度物理力学的前沿和发展趋势。     

Carbon nanotubes/TiO2 nanotubes composite photocatalysts for efficient degradation of methyl orange dye

A series of carbon nanotubes/TiO2 nanotubes （CNTs/TNTs） composite photocatalysts were successfully prepared by incorporation of CNTs in HNO3 washing process. These photocatalysts were characterized by XRD, N2 physical adsorption, UV-vis diffuse reflectance spectroscopy, TEM and Raman spectroscopy, respectively, and their photocatalytic activities were tested by using methyl orange （MO） as a model compound. Also, the effects of amount of CNTs incorporated, calcination temperature and amount of catalyst on the photocatalytic activity of the composite photocatalyst were systematically investigated. The results show that the CNTs/TNTs composite exhibits much higher photocatalytic activity than that of the TNTs or CNTs alone.     

功能梯度碳纳米管增强复合材料结构建模与分析研究进展

功能梯度碳纳米管增强复合材料是一种新一代的先进复合材料。在这种材料中,碳纳米管作为增强体在空间位置上梯度排布。功能梯度碳纳米管增强复合材料的力学行为已成为近年来材料科学与工程科学的研究热点。本文对功能梯度碳纳米管增强复合材料结构的建模与分析的研究进展进行评述,集中讨论功能梯度碳纳米管增强复合材料梁、板、壳在各种载荷条件下,边界条件下和环境条件下的线性和非线性弯曲、屈曲和后屈曲、振动和动力响应。文中所列成果可以看作是进一步研究的基石。最后,提出需要进一步研究的方向。     

Nonlinear in-plane thermal buckling of rotationally restrained functionally graded carbon nanotube reinforced composite shallow arches under uniform radial loading

The nonlinear in-plane instability of functionally graded carbon nanotube reinforced composite (FG-CNTRC) shallow circular arches with rotational constraints subject to a uniform radial load in a thermal environment is investigated. Assuming arches with thickness-graded material properties, four different distribution patterns of carbon nanotubes (CNTs) are considered. The classical arch theory and Donnell’s shallow shell theory assumptions are used to evaluate the arch displacement field, and the analytical solutions of buckling equilibrium equations and buckling loads are obtained by using the principle of virtual work. The critical geometric parameters are introduced to determine the criteria for buckling mode switching. Parametric studies are carried out to demonstrate the effects of temperature variations, material parameters, geometric parameters, and elastic constraints on the stability of the arch. It is found that increasing the volume fraction of CNTs and distributing CNTs away from the neutral axis significantly enhance the bending stiffness of the arch. In addition, the pretension and initial displacement caused by the temperature field have significant effects on the buckling behavior.     

Modeling and analysis of functionally graded carbon nanotube reinforced composite structures: A review

功能梯度碳纳米管增强复合材料是一种新一代的先进复合材料.在这种材料中,碳纳米管作为增强体在空间位置上梯度排布.功能梯度碳纳米管增强复合材料的力学行为已成为近年来材料科学与工程科学的研究热点.本文对功能梯度碳纳米管增强复合材料结构的建模与分析的研究进展进行评述,集中讨论功能梯度碳纳米管增强复合材料梁、板、壳在各种载荷条件下,边界条件下和环境条件下的线性和非线性弯曲、屈曲和后屈曲、振动和动力响应.文中所列成果可以看作是进一步研究的基石.最后,提出需要进一步研究的方向.     

Buckling analysis of multi-walled carbon nanotubes: a continuum model accounting for van der Waals interaction

Explicit formulas are derived for the van der Waals (vdW) interaction between any two layers of a multi-walled carbon nanotube (CNT). Based on the derived formulas, an efficient algorithm is established for the buckling analysis of multi-walled CNTs, in which individual tubes are modeled as a continuum cylindrical shell. The explicit expressions are also derived for the buckling of double-walled CNTs. In previous studies by Ru (J. Appl. Phys. 87 (2000b) 7227) and Wang et al. (Int. J. Solids Struct. 40 (2003) 3893), only the vdW interaction between adjacent two layers was considered and the vdW interaction between the other two layers was neglected. The vdW interaction coefficient was treated as a constant that was not dependent on the radii of the tubes. However, the formulas derived herein reveal that the vdW interaction coefficients are dependent on the change of interlayer spacing and the radii of the tubes. With the increase of radii, the coefficients approach constants, and the constants between two adjacent layers are about 10% higher than those reported by Wang et al. (Int. J. Solids. Struct. 40 (2003) 3893). In addition, the numerical results show that the vdW interaction will lead to a higher critical buckling load in multi-walled CNTs. The effect of the tube radius on the critical buckling load of a multi-walled CNT is also examined.     

An atomistic-based continuum theory for carbon nanotubes: analysis of fracture nucleation

Carbon nanotubes (CNTs) display unique properties and have many potential applications. Prior theoretical studies on CNTs are based on atomistic models such as empirical potential molecular dynamics (MD), tight-binding methods, or first-principles calculations. Here we develop an atomistic-based continuum theory for CNTs. The interatomic potential is directly incorporated into the continuum analysis through constitutive models. Such an approach involves no additional parameter fitting beyond those introduced in the interatomic potential. The atomistic-based continuum theory is then applied to study fracture nucleation in CNTs by modelling it as a bifurcation problem. The results agree well with the MD simulations.     

Mechanics of hydrogen storage in carbon nanotubes

A continuum mechanics model is established for hydrogen storage in single- and multi-wall carbon nanotubes (CNTs) and the bundle of single-wall CNTs. The model accounts for the deformation of CNTs, and van der Waals interactions among hydrogen molecules and between hydrogen and carbon atoms. The analytical expressions of hydrogen storage (number of hydrogen molecules per unit volume) in CNTs are obtained, and are validated by atomistic simulations. CNTs are categorized as tiny, small, medium and large CNTs; tiny CNTs cannot achieve the goals of hydrogen storage (62 kg/m³ and 6.5 wt% of hydrogen set by the US Department of Energy) without fracture; small CNTs are strained during hydrogen storage; medium CNTs can achieve the above goals without the strain and do not self collapse; and large CNTs may self collapse upon the release of hydrogen.     

纳米碳管/铝基复合材料的制备及摩擦磨损性能研究

利用粉末冶金法制备纳米碳管/铝基复合材料,研究不同纳米碳管含量对复合材料硬度和稳态摩擦磨损行为的影响,采用扫描电子显微镜观察复合材料的磨损表面形貌,并对其磨损机制进行探讨.结果表明:随着纳米碳管质量分数的增加,复合材料的硬度呈现先增大而后减小的趋势,含质量分数为2%的纳米碳管复合材料硬度比铝增加约80%;复合材料的摩擦系数逐渐降低,磨损率先减小而后增大;含质量分数为1%的纳米碳管复合材料磨损机制为磨粒磨损和粘着磨损,而含质量分数为2%的纳米碳管复合材料以剥层磨损和疲劳磨损为主.     

Mechanical behaviour of carbon nanotubes under combined twisting–bending

The main objective of this paper is to investigate the mechanical behaviour (strength and stiffness) of carbon nanotubes (CNTs) under combinations of bending and twisting. In order to achieve this goal, molecular dynamics (MD) simulations of bended and twisted CNTs are performed. The LAMMPS code is used, the AIREBO potential is considered for CC bonds, the temperature is kept at 300 K and incremental bending and twisting rotations are imposed to the CNT. Two types of CNTs are analyzed, including zig-zag (8,0) and armchair (5,5) CNTs with similar radius and length. The CNTs are also analyzed for pure bending and pure twisting. The main results are shown in the form of diagrams of energy and moment against imposed rotations. Some relevant conclusions are drawn concerning the influence of loading (bending and twisting) on the stiffness, strength and failure of CNTs: namely, it is concluded that armchair CNTs possess higher strength and fracture toughness under twisting–bending loading than zigzag CNTs; additionally, it is found that both CNTs (armchair and zigzag) still support moderate-to-high bending levels without failure after being extremely twisted and torsionally buckled, even for twisting angles four times those corresponding to torsional buckling; finally, the results prove that CNTs, mostly armchair ones, exhibit very high twisting–bending stiffness and strength and can be used with confidence as torsional spring elements in nanoelectromechanical systems (NEMS).