定向生长阵列化纳米碳管研究进展

本文介绍了目前有关定向纳米碳管制备的一些主要方法，并概述了定向纳米碳管的形态结构特征。定向生长的纳米碳管阵列由于其优越的电子发射特性，因而在平面显示器等方面具有良好的应用前景。     

熔融纺丝方法制备纳米碳管/聚丙烯复合纤维及其拉伸性能

采用传统的熔融纺丝技术大量制备了定向性良好的纳米碳管／聚丙烯复合纤维。扫描电镜观察证实了纳米碳管在纤维里的定向性以及分散性都得到了较大的改善。通过拉伸实验测试了纳米碳管／聚丙烯复合纤维的力学性能，采用weibull统计分析发现纳米碳管的添加显著提高了复合纤维的拉伸强度，当添加纳米碳管的质量分数达到3％时，纤维强度最高，达到61MPa，超过聚丙烯纤维强度120％。复合纤维拉伸断口的形貌特征也证实了纳米碳管添加对复合纤维拉伸性能影响存在临界现象。     

定向纳米碳管微观结构的观察和生长机制探讨

SiO2表面溅射铁膜后用CVD法制备了定向纳米碳管。用扫描电镜、透射电镜和高分辨透射电镜对顶部催化剂及包裹于管内的催化剂、纳米碳管的结构和所形成的竹节状形貌进行了观察。以液态生长纳米碳管为基础提出了一种纳米碳管生长机制。     

化学气相沉积法快速生长定向纳米碳管

利用化学气相沉积法，采用二甲苯为碳源，二茂铁为催化剂，氮气作保护气，在石英基底上催化裂解生长定向纳米碳管，试验结果表明：在775℃，120min的条件下，可生长出长达200μm厚的定向纳米碳管薄膜；在775℃，反应时间为60min～120min时，纳米碳管的长度为100μm～200μm，而纳米碳管的直径变化不明显。而无氢气，较高的反应温度和连续的催化剂供给对快速生长定向纳米碳管有重要的影响。     

定向纳米碳管表面有机和无机膜的制备

在AAO ( 阳极氧化铝 ) 模板上的定向纳米碳管表面制备了有机和无机膜。一种是采用真空蒸镀的方法沉积酞菁铜 ( CuPc ) 有机膜,另一种是用电沉积的方法在碳管表面沉积钴金属膜。对所镀的膜层进行了扫描电镜和透射电镜观察,结果表明:在纳米碳管表面获得了均匀的有机和无机涂层。它们的区别是蒸镀方法使纳米碳管背面不能获得涂层,而电镀方法能在整根纳米碳管上获得均匀涂层。      

气相沉积生长单壁纳米碳管束

采用流动催化热解碳氢化合物方法制备出具有一定取向的单壁纳米碳管束。研究了单壁纳米碳管束的生长过程,发现单壁纳米碳管的生长过程是在气流飘浮单个催化剂颗粒中完成。这与热解碳氢化合物制备定向的多壁纳米碳管在基体催化上生长过程有所不同。根据单壁纳米碳管生长过程,推测出单壁纳米碳管束生长速度的数量级为10^-5m/s。     

多壁纳米碳管电极电吸附脱盐性能的研究

利用透射电镜(TEM)和X射线衍射(XRD)对多壁纳米碳管形貌和晶型结构进行分析,发现多壁纳米碳管管径分布范围窄,其层间距大于高定向石墨,且随着管径的增大逐渐减小;利用多壁纳米碳管对氮气吸附实验分析其表面结构,发现其比表面积和孔容随管径的增大而减小,所形成的空隙绝大部分为中孔;将多壁纳米碳管处理后,压制成电极,组装成电吸附脱盐器,研究纳米碳管管径对电极电容和脱盐性能的影响,结果表明多壁纳米碳管管径越小,电极比电容越高,脱盐能力越强,随着中孔比表面积增大电极比电容和电极单位脱盐量均呈线性增加。     

单壁纳米碳管/聚酰亚胺复合材料的制备及导电特性

采用熔融聚合法和反复机械拉伸法,制备出定向排列单壁纳米碳管(SWNTs)/聚酰亚胺(PI)复合材料。研究了纳米碳管在复合体中的排列和分散情况。讨论了填充纳米碳管的质量分数对复合材料导电性能的影响,发现SWNTs填充质量分数很少时,复合体系呈现渗流行为,表现出良好的导电性和各向异性,其电导率随着填充纳米碳管的质量分数增加,电导率增大,而且在其拉伸方向比其垂直方向显示出较高的电导率,沿着其拉伸方向的渗流阈值比其垂直方向要低,说明单壁碳纳米管在复合物材料中呈现出良好的排列和均匀分散。     

水基碳管纳米流体制备及其热物性实验研究

采用添加表面活性剂阿拉伯胶(GA)的方法制备碳管纳米流体,并对不同长径比以及经球磨、酸化处理的碳管纳米流体热物性进行了研究。通过透射电子显微镜和扫描电子显微镜观察表明,所制备的碳管纳米流体具有很好的分散性和稳定性。碳管纳米流体热物性实验结果表明,碳管的比表面积和直线度是碳管长径比影响纳米流体热导率的主要因素。碳管经球磨处理时,随球磨时间延长,碳管长径比和直线度先后对纳米流体热导率提升起主导作用,碳管酸化处理后,改善了其分散性并降低了接触热阻,这是纳米流体热导率提高的主要因素。但随着碳管酸化时间的延长,碳管长径比起主导作用。碳管纳米流体的粘度主要受碳管分散性和直线度的影响。     

中国纳米功能材料研究取得重大成果

中国科学家在纳米管和其他功能纳米材料研究方面取得了７项具有重要影响的成果。这７项重要成果是：（１）大面积定向碳管阵列合成。研究人员发展了利用化学气相法高效制备纯净碳纳米管技术,用这种创新技术合成的纳米管,孔径基本一致,约２０纳米,长度约１００微米,纳米管阵列面积达到３毫米×３毫米。其定向排列程度高,碳纳米管之间间距为１００微米。这种大面积定向纳米碳管阵列,在平板显示的场发射阴极等方面有重要应用前景。（２）超长纳米碳管制备。研究人员利用改进后的基底,成功地控制了碳纳米管的生长模式,实现了催化剂颗料…     

Doping of carbon nanotubes with nitrogen improves protein coverage whilst retaining correct conformation

Relevant parameters for non-covalent protein functionalization of carbon nanotubes are explored. Multiwalled carbon nanotubes are carboxylated and functionalized with metalloproteins. Using atomic force microscopy (AFM) we quantitatively determine that coverage with nitrogen-doped multiwalled carbon nanotubes is superior compared to coverage with un-doped multiwalled carbon nanotubes, due to enhanced carboxylation. Conformational analysis using a combination of AFM, antibody binding assays, circular dichroism and UV-visible spectroscopy demonstrates that the metalloproteins retain their native structure when adsorbed to nitrogen-doped multiwalled carbon nanotubes irrespective of their size, charge or folding motif.     

Multiwalled carbon nanotube reinforced polymer composites

Due to their high stiffness and strength, as well as their electrical conductivity, carbon nanotubes are under intense investigation as fillers in polymer matrix composites. The nature of the carbon nanotube/polymer bonding and the curvature of the carbon nanotubes within the polymer have arisen as particular factors in the efficacy of the carbon nanotubes to actually provide any enhanced stiffness or strength to the composite. Here the effects of carbon nanotube curvature and interface interaction with the matrix on the composite stiffness are investigated using micromechanical analysis. In particular, the effects of poor bonding and thus poor shear lag load transfer to the carbon nanotubes are studied. In the case of poor bonding, carbon nanotubes waviness is shown to enhance the composite stiffness.     

DNA-assisted dispersion and separation of carbon nanotubes

Carbon nanotubes are man-made one-dimensional carbon crystals with different diameters and chiralities. Owing to their superb mechanical and electrical properties, many potential applications have been proposed for them. However, polydispersity and poor solubility in both aqueous and non-aqueous solution impose a considerable challenge for their separation and assembly, which is required for many applications. Here we report our finding of DNA-assisted dispersion and separation of carbon nanotubes. Bundled single-walled carbon nanotubes are effectively dispersed in water by their sonication in the presence of single-stranded DNA (ssDNA). Optical absorption and fluorescence spectroscopy and atomic force microscopy measurements provide evidence for individually dispersed carbon nanotubes. Molecular modelling suggests that ssDNA can bind to carbon nanotubes through pi-stacking, resulting in helical wrapping to the surface. The binding free energy of ssDNA to carbon nanotubes rivals that of two nanotubes for each other. We also demonstrate that DNA-coated carbon nanotubes can be separated into fractions with different electronic structures by ion-exchange chromatography. This finding links one of the central molecules in biology to a technologically very important nanomaterial, and opens the door to carbon-nanotube-based applications in biotechnology.     

碳纳米管的特性及应用

介绍了巴基球及碳纳米管的发现和历史 ,重点介绍了碳纳米管的基本性能和晶体结构 ,描述了碳纳米管电传导和热传导的机理。文中还介绍了碳纳米管的主要生产方法和各自的优点。根据全球碳纳米管应用研究的方向 ,对碳纳米管的应用领域进行了探讨 ,展望了碳纳米管的应用前景及商业开发价值     

纳米碳管电化学储氢的研究进展

纳米碳管的储氢是近年来纳米碳管领域研究的一个热点。纳米碳管储氢研究有两种方法，一种是气相法，另一种是电化学法。本文对纳米碳管电化学储氢的基本原理、纳米碳管电化学储氢的理论计算以及氢与纳米碳管的相互作用机制，特别是目前单壁和多壁纳米碳管电化学储氢的实验研究进展进行了综述，展望了利用其电化学储氢特性作为高性能电池的可能性。     

Analysis of elastic properties of carbon nanotube reinforced nanocomposites with pinhole defects

Due to their unique molecular structure, carbon nanotubes exhibit outstanding properties. They are regarded as ideal reinforcements of composites. In this paper, the effects of pinhole defects on mechanical properties are investigated for wavy carbon nanotubes based nanocomposites using 3-D Representative Volume Element with long carbon nanotubes. The carbon nanotubes are modeled as continuum hollow cylindrical shape elastic material with pinholes, having some curvature in its shape. These defects are considered on the single walled carbon nanotubes. The mechanical properties like Young’s modulus of elasticity are evaluated for various values of waviness index, as well as type and number of pinhole defects. The effects of interactions between both defects as well as their influence on the nanocomposites are studied under an axial loading condition. Numerical equations are used to extract the effective material properties for the different geometries of Representative Volume Elements with non-defective carbon nanotubes. The finite element method results obtained for non-defective carbon nanotubes are consistent with analytical results for cylindrical Representative Volume Elements, which validate the proposed model. It is observed that the presence of pinhole defects as well as waviness, can significantly reduces the effective reinforcement, when compared with nanotubes without pinhole defects and this reinforcement decreases with the increase of the number of pinhole defects.     

流动催化法连续制备碳纳米管及其形态和结构的研究

以二茂铁作为催化剂来源、以苯作为碳源、氢气和氩气分别作为载气和稀释气体,在１１００℃连续地合成了碳纳米管．碳纳米管的生成分二个过程：催化生长和表面无定形碳的生成．所得到的碳纳米管的内径为３～６ｎｍ,而外径约为２０～７０ｎｍ碳纳米管的外径随气体流速的增加而变细,在较细的碳纳米管中观察到了由催化生长而成的具有光滑薄壁的原始碳纳米管．生成的碳纳米管的长度达数十微米、直径较均匀,其端部大多为圆形,但也观察到其他的形状的端部．     

In situ fabrication of carbon nanotube/mesocarbon microbead composites from coal tar pitch

Carbon nanotube/mesocarbon microbead composites have been synthesized from coal tar pitch with carbon nanotubes. How the carbon nanotubes affect the growth and the structure of mesocarbon microbeads are studied. The result shows that the size of beads decreases when more carbon nanotubes are added, and when the ratio of carbon nanotubes is set at 5%, we get the smallest sample with quite uniform shape. Carbon nanotubes exist both on the surface and inside of the samples and they will inhibit the growth and coalescence of these spheres. The addition of carbon nanotubes decreases the graphitization degree of the samples and makes their microtexture tend to be disordered.     

镀Ni-P和Ni-N合金碳纳米管的磁性能及其复合材料的微波吸收性能

用竖式炉流动法,以二茂铁为催化剂,噻吩为助催化剂,苯为碳源通过催化裂解反应在1100~1200℃制备了直线形碳纳米管,外径为20~50 nm,内径10~30 nm,长度50~1000 μm。用化学镀工艺在碳纳米管表面均匀包覆了Ni-P和Ni-N合金,研究了它们的磁性能及其环氧树脂基复合材料在2~18 GHz的微波吸收性能。与纯碳纳米管相比,镀Ni-P合金碳纳米管复合材料的吸收峰向高频移动,镀Ni-P和Ni-N合金碳纳米管经热处理后,复合材料的吸收峰向低频移动。镀Ni-P合金碳纳米管以及镀Ni-P和Ni-N合金经热处理碳纳米管的矫顽力分别为304.34 Oe、 81.65 Oe、 183.85 Oe。随着矫顽力的增加,在2~18 GHz,复合材料的微波吸收峰向高频移动。在复合材料中,碳纳米管以及镀Ni-P和Ni-N合金的碳纳米管作为偶极子吸收微波。      

碳纳米管气敏传感器响应机理研究进展

碳纳米管以其优异的表面化学性能和良好的电学性能成为制作化学传感器的理想材料.论述了碳纳米管的结构特点及其气敏响应机理的最新进展,包括气敏吸附和电学传感机理和复合型碳纳米管气敏材料响应机理研究的进展.