多壁碳纳米管载体的改性及应用

多壁碳纳米管独特的结构和性质(纳米尺寸、介孔结构和大比表面积)使其成为催化剂的良好载体.侧重于催化领域的应用,结合改性的多壁碳纳米管为载体的催化剂在各催化反应中的应用,综述了催化领域中多壁碳纳米管载体的改性方法,指出针对不同的催化反应需采用不同的方法或多种方法相结合对碳纳米管进行表面改性修饰.     

碳纳米管增强陶瓷基复合材料研究进展

碳纳米管因其独特的结构而具有许多独特的性能,除了在半导体器件、储氢、传感器、吸附材料、电池电极、催化剂载体等领域具有非常广阔和诱人的应用前景外,碳纳米管在制备结构、功能以及结构/功能一体化复合材料方面也将大有作为.本研究对国内外碳纳米管增强陶瓷基复合材料的研究状况进行了综合分析,指出了存在的问题及以后的发展方向.     

碳纳米管及其复合材料在固体火箭推进剂中的应用研究进展

文章从碳纳米管、碳纳米管复合物及储氢碳纳米管三方面综述了碳纳米管及其复合材料在推进剂中的应用研究进展,总结了碳纳米管、碳纳米管复合物对推进剂及其组分的不同催化效果,指出碳纳米管复合物是推进剂燃烧催化剂未来研究的重点方向,同时分析了储氢碳纳米管的研究现状,提出储氢碳纳米管作为新型含能材料添加物是发展高能推进剂的可能途径之     

科研

碳纳米管储氢技术研究获新突破 清华大学吴德海教授所领导的碳纳米材料研究小组,近日发现一种经处理后表现出显著储氢性能的碳纳米管,它有望成为新的清洁能源——氢能电池的制备材料。 课题小组对定向碳纳米管的电化学储氢特性进行了系统研究,发现这种碳纳米管具有许多全新的力学、电学、热学和光学性能,尤其是将它混以铜粉后表现出的显著的储氢性能。课题小组将碳纳米管制成电极,进行恒流充放电电化学实验,结果表明,混铜粉定向多壁碳纳米管电极的储氢量是石墨电极的10倍,是非定向多壁碳纳米管电极的13倍,比电容量高达1625mAh/g,对应储氢量为5.7wt％（质量分数）,具有优异的电化学储氢性能。     

乙醇催化燃烧法制备竹节形碳纳米管

乙醇催化燃烧法可以方便的制备出碳纳米管和碳纳米纤维。介绍采用该方法制备出一种独特的竹节形的碳纳米管，利用乙醇作为碳源和燃料，提供材料生长所需的能量；利用Cu薄片作为基底；利用FeCl3或Fe（NO3）3作为催化剂先体。通过扫描电子显微镜（SEM），透射电子显微镜（TEM），对黑色絮状的沉积产物进行表征。实验结果表明，产物中的碳纳米管具有较好的竹节形结构。实验也表明制备的竹节形碳纳米管的形貌和微结构与其独特的制备条件有关，如：火焰的抖动，催化剂先体溶液的浓度，制备时间等。并对竹节形碳纳米管的形貌和生长机制进行了详细的讨论。     

碳纳米管的宏量制备及产业化

碳纳米管作为纳米材料的代表之一,因其独特的一维结构具备了优异的力学、电学、热学、光学和反应性能,使其在能源存储与转化、复合材料、多相催化、环境保护及生物医药等领域具有大量的应用潜力。本文简单介绍了碳纳米管及其制备方法,并总结了多种类型碳纳米管宏量制备的化学及工程原理以及对宏量制备方法进行了阐述。     

碳纳米管的应用

自 1991年碳纳米管被发现特别是单层碳纳米管的发现和宏观量的合成成功以来 ,引起了人们的广泛兴趣 ,已成为富勒烯领域的一个主要的研究特点 ,是物理、化学和材料科学等学科中最前沿的研究领域之一。由于其独特的结构 ,碳纳米管的研究具有重大的理论意义和潜在的应用价值 ,如 :其独特的结构是理想的一维模型材料 ;巨大的长径比使其有望用作坚韧的碳纤维 ,其强度为钢的 10 0倍 ,重量则只有钢的 1/6 ;同时它还有望用分子导线 ,纳米半导体材料 ,催化剂载体 ,分子吸收剂和近场发射材料等。科学家们认为碳纳米管有以下应用领域 :储氢材料、场致发…     

改性碳纳米材料在低温燃料电池中的应用

碳纳米材料(如炭黑、介孔碳、碳纳米管、石墨烯、碳纳米纤维、碳纳米角等)因其优异的电学性能和结构特性(良好的导电性能和超大的比表面积),被研究者广泛用作低温燃料电池贵金属催化剂的载体。然而,作为催化剂载体的这类碳纳米材料通常都存在电化学腐蚀的问题,碳载体的腐蚀通常会导致贵金属纳米催化剂的聚集,这将使催化剂的性能降低。为了改善碳载体的抗腐蚀性能,提高金属纳米粒子的活性和稳定性,许多研究工作致力于制备特殊结构的碳纳米材料,或对碳纳米材料进行表面修饰、掺杂等。与此同时,为了取代价格昂贵的贵金属催化剂,非贵金属催化剂的研究也成为一大热点,掺杂碳纳米材料就是研究热点之一。对近几年来围绕碳纳米材料制备、改性,以及这些改性碳纳米材料作为金属纳米粒子载体等的研究工作做了较为详细的综述,同时介绍了掺杂碳纳米材料作为氧还原催化剂的研究进展。     

改性碳纳米材料在低温燃料电池中的应用

碳纳米材料(如炭黑、介孔碳、碳纳米管、石墨烯、碳纳米纤维、碳纳米角等)因其优异的电学性能和结构特性(良好的导电性能和超大的比表面积),被研究者广泛用作低温燃料电池贵金属催化剂的载体.然而,作为催化剂载体的这类碳纳米材料通常都存在电化学腐蚀的问题,碳载体的腐蚀通常会导致贵金属纳米催化剂的聚集,这将使催化剂的性能降低.为了改善碳载体的抗腐蚀性能,提高金属纳米粒子的活性和稳定性,许多研究工作致力于制备特殊结构的碳纳米材料,或对碳纳米材料进行表面修饰、掺杂等.与此同时,为了取代价格昂贵的贵金属催化剂,非贵金属催化剂的研究也成为一大热点,掺杂碳纳米材料就是研究热点之一.对近几年来围绕碳纳米材料制备、改性,以及这些改性碳纳米材料作为金属纳米粒子载体等的研究工作做了较为详细的综述,同时介绍了掺杂碳纳米材料作为氧还原催化剂的研究进展.     

一种制备碳纳米管的新方法

以化学改性的膨润土为催化剂，利用化学气相沉积法催化裂解CH4，在高温条件下成功地制备了碳纳米管，并用透射电镜对其形貌与结构特征进行了表征。结果表明，所得产物形状弯曲，管径为15-20nm，长度达微米级的均匀碳纳米管；膨润土释放的金属铁起到了催化CH4的作用，在800℃条件下生长的碳纳米管质量最好、产率最高，若催化反应温度过高则会降低产品的质量，催化温度低于700℃时不能用来制备碳纳米管，与传统的过渡金属催化剂相比，这种矿物催化剂原料成本低廉，制备工艺简单，有利于碳纳米管的工业化生产。     

Tuning of vertically-aligned carbon nanotube diameter and areal density through catalyst pre-treatment

By controlling the timing and duration of hydrogen exposure in a fixed thermal process, we tuned the diameters of carbon nanotubes (CNTs) within a vertically aligned film by a factor of 2, and tuned the areal densities by an order of magnitude. The CNT structure is correlated with the catalyst morphology, suggesting that while chemical reduction of the catalyst layer is required for growth, prolonged H2 exposure not only reduces the iron oxide and enables agglomeration of the Fe film, but also leads to catalyst coarsening. Control of this coarsening process allows tuning of CNT characteristics.     

Catalytic chemical vapor deposition of carbon nanotubes using Ni-La-O precursors

Carbon nanotubes (CNT) are synthesized by catalytic chemical vapor deposition with different compositions of Ni-La-O catalyst precursors obtained by citric acid complexometry. Only two compounds: LaNiO₃ (perovskite-type crystal structure, hexagonal system) and La₂NiO₄ (spinel-type crystal structure, orthorhombic system) in the obtained Ni-La-O catalyst precursors have the ability to grow CNT. Moreover, CNT obtained with the two different crystal structure catalyst precursors have different characteristics: different yield, pattern and oxidation resistance performance.     

Photolithographic fabrication of gated self-aligned parallel electron beam emitters with a single-stranded carbon nanotube

In this paper we report on the development of a photolithographic process to fabricate a gated-emitter array with single-stranded carbon nanotubes (CNTs) self-aligned to the center of the emitter gate using plasma-enhanced chemical vapor deposition (PECVD). Si tips are formed on a silicon wafer by anisotropic etching of Si using SiO(2) as a mask. Deposition of a SiO(2) insulating layer and Cr-W electrode layers creates protrusions above the Si tips. This wafer is polished, and the Cr-W on the tips is removed. Etching of the SiO(2) using hydrofluoric acid is performed to expose the gated Si tip. Incorporation of a novel diffusion process produces single-stranded CNTs by depositing a thin Ni layer on the Si tips and thermally diffusing the Ni layer to yield a catalyst particle for single-stranded CNT growth. The large surface to volume ratio at the apex of the Si tip allows a Ni particle to remain to act as a catalyst to grow a single-stranded CNT for fabricating the CNT based emitter structure. Diffusion of the Ni is carried out in situ during the heating phase of the PECVD CNT growth process at 600?°C. The diameters of the observed CNTs are on the order of 20?nm. The field emission characteristics of the gated field emitters are evaluated. The measured turn-on voltage of the gated emitter is 5?V.     

催化剂前驱体对碳纳米管生长影响的研究

采用柠檬酸络合法, 通过改变La和Ni的摩尔比例获得了一系列的La-Ni-O催化剂前驱体, 以H₂作为还原气体, N₂为保护气体, C₂H₂为碳源, 采用化学气相沉积法制备碳纳米管(CNT). 用XRD研究所得催化剂前驱体还原前后的结构, TEM观察所得CNT的形貌. 结果发现: 在所制备的一系列La-Ni-O催化剂前驱体中, 具有催化活性的物质只有: LaNiO₃和La₂NiO₄. 但由LaNiO₃所制备的CNT的产率却大大高于由La₂NiO₄所制备的CNT的产率. 经分析认为, 这主要是与两者被还原后的产物中的纳米级金属Ni的(111)晶面含量有关, 纳米级金属Ni的(111)晶面含量和晶粒度越大, 其CNT的产率和内径也就越大.     

Influence of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> buffer layer on catalyst morphology and spinnability of carbon nanotube arrays

Carbon nanotube (CNT) fibers spun from vertically aligned CNT arrays hold great promise in promoting CNT’s practical applications. Their production and properties strongly depend on the spinnability of the arrays. Herein, we study the influence of Al₂O₃ buffer layer on catalyst morphology and the spinnability of CNT arrays. Long and vertically aligned CNT arrays have been obtained from a wide range of Al₂O₃ buffer layer thickness, but the spinnable ones have only derived from a narrow range of the thickness. It is further found that the Al₂O₃ buffer layer can regulate the size and size distribution of the catalyst particles through balancing surface diffusion and inter-layer diffusion. Small, dense, and uniform-distributed nanoparticles are fingerprinted as the optimal catalyst for growing long and spinnable CNT arrays and can be obtained at a proper thickness of buffer layer. By using a tailored tri-layered Fe/Al₂O₃/SiO₂ catalyst, the obtained CNT arrays could reach a height of 500–800 µm and are highly spinnable.     

碳纳米管异质结构的 ECR-CVD法制备

使用电子回旋共振微波等离子体化学气相沉积方法（ECR-CVD），以Fe3O4纳米粒子为催化剂，多孔硅为基底，采用CH4／H2和CH4／B2H6／H2两种气源在连续的CVD过程中大量合成了一种新型的纳米管异质结构．扫描电镜（SEM）和透射电镜（TEM）观察表明：合成的异质结构一端是类竹节状的掺硼碳纳米管，另一端是光滑中空的纯碳纳米管．异质结构采用底端生长模式，先行生长的掺硼纳米管处于纳米管结构的顶端．     

碳纳米管/聚苯乙炔复合材料的导电性

用AlCl₃ 作催化剂制备了聚苯乙炔( PPA) , 用浓H₂SO₄ 进行磺化改性, 通过共混制得碳纳米管(CNT) /PPA 及磺化CNT/ PPA 复合材料, 进行导电性能、XRD 等测试。当CNT 含量增加时, 复合材料的电导率升高, 磺化CNT/ PPA 的导电阈值比CNT/ PPA 的导电阀值降低了1 %, 前者达到极限电导率所需CNT 的量是后者的10 %; 分析了随着温度变化影响复合材料电阻变化的因素; XRD 测试表明, 在CNT 界面上的磺化PPA 有新的晶型产生。      

Catalytic-free growth of VACNTs for energy harvesting

Abstract

The present study introduces a process to grow micro-honeycomb (µ-HC) vertically aligned carbon nanotubes (VACNTs) using thermal chemical vapor deposition technique. Methane is used as a source of carbon and hydrogen gas as a reducing agent. Where, the fabricated µ-HC structure reported in literature involves complex synthesis process and requires a catalyst layer, the novelty of the process used here lies in the fact that no catalyst layer is used for the growth of CNT network, rather copper foil is used as a substrate. The in-situ cracking of CNTs due to water treatment leads to the formation of µ-HC CNT network, which is confirmed by Raman spectroscopy. Further scanning electron microscopy analysis shows that the length of developed µ-HC CNT is ～5?µm. Hexagonal µ-HC network shows more than 94% absorption in UV-Vis-NIR wavelength region. The designed process provides high-yield with a low-cost synthesis of vertically aligned CNTs having 3?D microarchitecture. The fabricated CNT network can be used as an electrode for supercapacitor, as an active layer in a photovoltaic cell and most of the energy harvesting devices.     

Manufacturing polymer/carbon nanotube composite using a novel direct process

A direct process for manufacturing polymer carbon nanotube (CNT)-based composite yarns is reported. The new approach is based on a modified dry spinning method of CNT yarn and gives a high alignment of the CNT bundle structure in yarns. The aligned CNT structure was combined with a polymer resin and, after being stressed through the spinning process, the resin was cured and polymerized, with the CNT structure acting as reinforcement in the composite. Thus the present method obviates the need for special and complex treatments to align and disperse CNTs in a polymer matrix. The new process allows us to produce a polymer/CNT composite with properties that may satisfy various engineering specifications. The structure of the yarn was investigated using scanning electron microscopy coupled with a focused-ion-beam system. The tensile behavior was characterized using a dynamic mechanical analyzer. Fourier transform infrared spectrometry was also used to chemically analyze the presence of polymer on the composites. The process allows development of polymer/CNT-based composites with different mechanical properties suitable for a range of applications by using various resins.     

Effect of Ni loading and reaction temperature on the formation of carbon nanotubes from methane catalytic decomposition over Ni/SiO<Subscript>2</Subscript>

Since their discovery carbon nanotubes (CNT) have attracted much attention due to their singular physical, mechanical and chemical properties. Catalytic chemical vapor deposition (CCVD) of hydrocarbons over metal catalysts is the most promising method for the synthesis of CNT, because of the advantages of low cost and large-scale production and the relatively low temperature used in the process, compared to the other methods (laser ablation and discharge between graphite electrodes). In this study, CNT were synthesized by CCVD using Ni supported on SiO₂ as a catalyst. The carbon deposited in the reaction was analyzed by Raman spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of reaction temperature and Ni loading on the carbon nanotube formation were evaluated. The catalyst with 5% Ni favored high yield of CNT at lower temperature, with abundant “multi-walled carbon nanotubes” (MWNTs) at 625 °C, while single-walled carbon nanotubes (SWNTs) and MWNTs were obtained at 650 °C. With an increase in the reaction temperature a marked decrease in the yield of CNT was observed, probably due to the sintering of the catalyst. The catalyst with 1% Ni gave SWNTs with a high degree of order at all reaction temperatures, but in low quantity.