Multiwalled Nanotubes: Their Formation by Irradiating Graphite with High Doses of Electrons

Abstract

We report the production of carbon nanotubes by high dose of electron irradiation. The irradiation was performed with a 2 MeV Van de Graaff accelerator, while the irradiation conditions were the following: voltage 1.3 MeV, current 5 µA, dose rate 25 kGy/min, and total dosage 1000 kGy. The samples were analyzed in a high‐resolution transmission electron microscope. The main features observed on the samples, were huge nanotubes of several nanometer long and few nanometer wide, which are capped at one end. It is good to point out, that at this level of irradiation, we were not able to find either onion‐like or particle structures throughout the material, as it is usual in similar hexagonal structures. This behavior could be attributed to the level of irradiation used to create the nanotubes under investigation.     

Effect of intense laser and energetic ion irradiation on Raman modes of Multiwalled Carbon Nanotubes

The effects of intense laser and energetic ion irradiation on Raman vibrational modes of Multiwalled Carbon Nanotubes have been investigated. The intensity ratio of D and G modes decreases with increase in laser power density and remains almost constant with decrease of laser power density. The intensity ratio of D mode to G mode for ion irradiated Multiwalled Carbon Nanotubes decreases at low fluence (4 × 10¹¹ ions/cm²) and increases further with increase in ion fluence. The results show that ion irradiation at low fluence and laser irradiation lead to purification/ordering of the nanotubes.     

An attempt to prepare carbon nanotubes by carbonizing polyphosphazene nanotubes with high carbon content

Polyphosphazene nanotubes with about 20 nm in inner diameter and 100-200 nm in outer diameter were fabricated easily and then carbonized at 800 °C in a nitrogen atmosphere. Scanning electron microscopy and transmission electron microscope results showed that the bulk morphology of polyphosphazene nanotubes was retained after carbonization. The carbon content of the carbonized samples reached 93.28%. X-ray diffraction and Raman spectrum showed that the carbonized samples had low graphitization state. The present method can be used for a mass production of carbon nanotubes.     

Selective Formation of Metal Nanoparticles on the Sidewalls of Carbon Nanotubes

Pt and Au nanoparticles spontaneously form on the sidewalls of single-walled carbon nanotubes (SWNTs) and multiwall carbon nanotubes (MWNTs) in a selective manner. Scanning electron microscope (SEM) and transmission electron microscope (TEM) studies reveal that metal ions are first absorbed on the sidewalls of carbon nanotubes (CNTs) and then are reduced by ethanol. This mechanism is tentatively proposed and discussed.     

Synthesis of binary and triple carbon nanotubes over Ni/Cu/Al2O3 catalyst by chemical vapor deposition

Novel binary and triple carbon nanotubes (CNTs) with one common catalytic particle encapsulated have been synthesized using Ni/Cu/Al₂O₃ catalyst, which was produced by a sol-gel method. But when using Ni/Al₂O₃ as catalyst, a mass of common CNTs, that is, one CNT with one catalytic particle encapsulated, was obtained. The results showed that copper-element doping to the Ni/Al₂O₃ catalyst played a key role in the synthesis of CNTs, signifying a novel approach to modify the Ni/Al₂O₃ catalyst. Based on the transmission electron microscopy observations, a simple growth mechanism was developed to describe the growth of the binary or triple CNTs, which could be well explained by a diffusion segregation process.     

Preparation of Cu nanoparticles on carbon nanotubes by solution infusion method and calcining in ambient atmosphere

Copper nanoparticles were synthesized using carbon nanotubes as a template. The process involved neither pre-purification nor an additional reducing agent. This method was simple and the Cu nanoparticles were uniformly loaded on the carbon nanotubes. TEM, SEM, XRD and EDX were used to examine the morphology of the Cu particles. The diameter of the carbon nanotubes is about 70-90 nm and the size of the nanoparticles is about 50-70 nm.     

Charge Transfer Complex of TTF-Carbon Nanotubes

The charge transfer complex of multi-walled carbon nanotubes (MWNTs) and tetrathiafulvalene (TTF) was prepared and characterized by x-ray photoelectron spectroscopy (XPS), and electron spin resonance (ESR) spectrometer. The results demonstrated that MWNTs could act as electron acceptors in the formation of charge transfer complex.     

Formation of Transition Metal Cluster Adducts on the Surface of Single-walled Carbon Nanotubes: HRTEM Studies

We report the formation of chromium clusters on the outer walls of single-walled carbon nanotubes (SWNTs). The clusters were obtained by reacting purified SWNTs with chromium hexacarbonyl in dibutyl ether at 100°C. The functionalized SWNTs were characterized by thermogravimetic analysis, XPS, and high-resolution TEM. The curvature of the SWNTs and the high mobility of the chromium moieties on graphitic surfaces allow the growth of the metal clusters and we propose a mechanism for their formation.     

Effect of FeOx loaded on CoOx/Al2O3 catalyst for the formation of thin-walled carbon nanotubes

Effects of FeO_x loaded on CoO_x/Al₂O₃ catalyst on the yield and morphology of the produced carbon nanotubes were studied. The findings showed that the addition of a small amount of FeO_x on the CoO_x/Al₂O₃ catalyst provoked the formation of carbon nanotubes with a thin wall structure. The results also revealed that an increase in FeO_x content decreased the yield of carbon nanotubes. An optimized weight ratio of CoO_x to FeO_x was found to be 8:2 (w/w) whereby the catalyst of this composition grew carbon nanotubes with a thin wall structure and not of diminutive carbon yield.     

Relation between Growth Parameters and Morphology of Vertically Aligned Fe-filled Carbon Nanotubes

Fe-filled multi-wall carbon nanotubes (MWNTs) were produced by pyrolysis of ferrocene in a dual furnace system. They grew vertically aligned on oxidized silicon substrates placed inside the reaction zone of a chemical vapor deposition reactor. A variation of the growth parameters has been performed in order to evaluate the possibility to control the Fe-filled nanotube growth process and thereby the nanotube- and the filling length, diameter and yield, and also the nanotube alignment. Electron microscopy studies show nanotubes with quite different morphologies. The relation between the aligned Fe-filled MWNTs growth and the most important growth parameters is discussed.     

化学气相沉积法制备碳纳米管

碳纳米管（CNTs）是一种具有独特理化性能和结构的一维纳米材料,也是当今纳米材料研究的焦点之一．在化学、生物、医药、能源、电子元件等诸多领域具有极高的应用价值．本文以有机溶剂环己烷为碳源．利用化学气相沉积法（CⅥ））在管式电阻炉内,以氩气为栽气,二茂铁为催化剂,一定温度条件下,制备了直径约为50nm,长度达几十微米以上的多壁碳纳米管（MWNTs）．采用拉曼光谱、扫描电镜、透射电镜、X-射线粉末衍射等测试手段,表征了碳纳米管的微观形貌和结构特征．通过对实验结果的分析和讨论,对CVD制备法中碳纳米管的生长机理进行了尝试性探讨。     

聚对苯二甲酸乙二醇酯共价接枝多壁碳纳米管及其表征

通过两步法将聚对苯二甲酸乙二醇酯(PET)分子链共价接枝到多壁碳纳米管(MWCNTs)表面,成功地制备了PET/MWCNTs复合材料。聚丙烯酰氯共价接枝MWCNTs的表面具有多个可反应的酰氯基团,通过与PET端羟基间的反应,以聚丙烯酰氯为中间聚合物层,成功将PET分子链接枝到了碳纳米管表面。采用傅立叶变化红外光谱(FT-IR)、透射电镜(TEM)、核磁(1H-NMR)和热失重分析(TGA)对接枝产物进行了表征,结果表明,PET分子已通过共价接枝的方式接枝到碳纳米管表面,被接枝聚合物的量约为MWCNTs的96%,该接枝聚合物层的存在将有利于多壁碳纳米管与PET树脂间相容性的提高,从而使PET/MWCNTs复合材料的性能得到提高。     

Synthesis of Heterogenous Multi-Walled Carbon Nanotubes in a Carbon Arc in Water

Boron-doped multi-walled carbon nanotubes (MWCNTs) were generated by arc discharge in water by using B-doped graphite electrodes. The product morphology was studied by SEM and HRTEM microscopy. The electronic features were determinated by Raman and EELS spectroscopy. Optical emission spectroscopy (OES) was used to evaluate the temperature and C₂ content distributions in arc plasma.     

聚合物接枝碳纳米管的研究进展

本文综述了线性聚合物及超支化聚合物接枝碳纳米管的研究现状,着重介绍了直接引入法、表面引发聚合法、分步增长法及与点击化学技术相结合的方法,并指出了其发展前景.     

Preparation of floral-patterned ZnO/MWCNT heterogeneity structure using microwave irradiation heating method

HNO₃-treated multi-walled carbon nanotubes enclosed by flower-like zinc oxide particles were prepared by a microwave irradiation heating method. The product was characterized by X-ray diffraction and scanning electron microscopy. It was found that the flower-like zinc oxide grows around the multi-walled carbon nanotubes to form a floral-patterned structure. Multi-walled carbon nanotubes play a role as a template for the growth of ZnO and they can link ZnO particles together as a complex fabrication. This discovery is useful for nano-electronic applications.     

甲烷化学气相沉积法合成小直径双壁碳纳米管

采用化学气相沉积法（CVD）以甲烷与氢气为原料,在900℃合成了大量的小直径双壁碳纳米管。我们用硝酸铁和氧化镁粉末的混合物作催化剂,三氧化二铝和钼酸铵作条件催化剂,研究表明条件催化剂的使用有利于双壁碳纳米管的选择性生长,可提高双壁碳纳米管的质量及其在产品中的比例,用扫描电子显微镜（SEM）、高分辨透射电镜（HRTEM）、热失重分析（TGA）和拉曼光谱（Raman）等分析纳米管的形貌和结构,结果发现其内径范围在0．62～0．88nm,外径范围在1．21～1．33nm之间。     

Multi-walled carbon nanotubes grow under low pressure hydrogen,air, and argon ambient by arc discharge plasma

Multi-walled carbon nanotubes (MWCNTs) were grown on cathode deposit by arc discharge plasma under H₂, Ar, and air ambient environment. The influence of ambient gas pressure on the structure and physical properties of carbon nanotube were compared. Herein, we highlight the influence of ambient environment and pressure to grow high quality carbon nanotubes. Field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction were used for structural characterization and yield determination. The result revealed that background gas and pressure were crucial factor for growing highly crystalline and highly graphitic with I_D/I_G ratio 0.237 obtained for MWCNTs' synthesized in H₂ environment with extreme low defects.     

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。     

化学气相沉积法合成碳纳米管的研究进展

本文主要评述了化学气相沉积法合成碳纳米管的最新研究进展，结合我们在这方面的工作，重点讨论了催化剂、碳源、反应温度对合成碳纳米管质量和产率的影响，并对这一领域的发展趋势作了展望。     

利用场发射显微镜研究单壁碳纳米管的场发射特性

利用场发射显微镜研究了单壁碳纳米管(SWCNTs)的场发射特性.由于实验中所用的SWCNTs的长度基本一致,因此能同时观察到多根SWCNTs的场发射像.SWCNTs的场发射像随着热处理温度的升高而变化,直至热处理温度过高而塌缩.在一定的实验条件下,观察到了具有精细结构的单根碳纳米管顶端"帽子"的场发射像.电流-电压(I-U)曲线分析表明,SWCNTs的电流来源于场发射.