THE INFLUENCE OF SYNTHESIS PARAMETERS ON THE PRODUCTION OF MULTIWALLED CARBON NANOTUBES BY THE FERROCENE CATALYZED PYROLYSIS OF TOLUENE

ABSTRACT

A high yield (～32?wt.%) of multiwalled carbon nanotubes was obtained in an iron catalyzed reaction. This was achieved in the temperature range 800–1000°C under an atmosphere of H₂/Ar by an improved solution injection method in a horizontal reactor using toluene as carbon source and ferrocene as catalyst precursor. The pyrolysis temperature, ferrocene concentration, solution feeding rate and carrier gas flow rate all influenced the yield of carbon nanotubes and the thickness of the aligned carbon nanotube films. The carbon nanotubes was prepared in high purity using optimized pyrolysis conditions.     

New synthesis of Cu2O and Cu nanoparticles on multi-wall carbon nanotubes

Cu₂O and Cu nanoparticles were deposited on the surface of multi-walled carbon nanotubes with a diameter range of 15–90 nm by the impregnate method. Multi-wall carbon nanotubes with a length of 200 μm and a diameter range of 70–110 nm were grown inside of quartz tubing by the spray pyrolysis method using ferrocene/benzene under argon flow. The nanotubes were then treated with nitric acid to clean the surface and generate carboxylic groups. The copper was impregnated on multi-walled carbon nanotubes using a xylene solution of copper(I) phenylacetylide as the precursor. Copper and cuprous oxide nanoparticles were obtained during thermal treatment.     

己烷低耗喷雾热解法大规模制备多壁碳纳米管

以己烷为碳源,二茂铁为催化剂前躯体,应用喷雾热解法,制备了多壁碳纳米管(MWCNTs).采用酸沥滤和空气氧化对MWCNTs进行纯化.利用SEM、TEM、XRD、EDS、TGA及Raman光谱分析等方法分别对原生和纯化MWCNTs进行表征.为制得优质、高产MWCNTs,对制备工艺参数作了优选,分别研讨了最佳制备参数,包括:二茂铁升华温度、己烷中二茂铁浓度、热解温度和时间,己烷与H2的流量比.MWCNTs具有典型的腊肠状(Sawsage-like)构型,长度大于数十微米,内、外管径分别为15nm～45nm及25nm～70nm,MWCNTs的纯度和产率的质量分数分别高于95%和70%.     

Synthesis of bamboo-shaped carbon-nitrogen nanotubes using acetonitrile-ferrocene precursor

We report the formation of bamboo-shaped carbon-nitrogen nanotubes by employing a simple, one-step and economically viable spray pyrolysis technique using new precursor; acetonitrile and ferrocene solution. By varying the concentration of ferrocene with respect to acetonitrile, it has been found that the optimum concentration of ferrocene in acetonitrile is 5 mg/ml. The special feature of the as-synthesized bamboo-shaped carbon-nitrogen nanotubes bundles is that they are produced in a high yield (1.25 gms/run). They also have long linear extents (approximately 430 microm) and are very clean. The average composition of carbon-nitrogen nanotubes comes out to be C26N.     

裂解温度,裂解时间和原料气流量对CVD法生产碳纳米管的影响

用ＣＶＤ法生产碳纳米管时，裂解温度、裂解时间和原料气流量大小对碳纳米管的产率、形态有很大影响，其中以裂解温度的影响最大。适宜的裂解温度、裂解时间和原料气流量有利于提高碳纳米管的产率和产量。在一定范围内提高裂解温度，可得到缺陷较少的碳纳米管     

Effect of ferrocene concentration on the synthesis of bamboo-shaped carbon-nitrogen nanotube bundles

We have investigated the effect of ferrocene concentration on the synthesis of carbon-nitrogen (C-N) nanotubes. The bamboo-shaped carbon-nitrogen nanotubes were synthesized by spray pyrolysis of Fe(C5H5)2 and CH3CN solution using argon as a carrier gas at the optimum temperature of approximately 900 degrees C. The effect of ferrocene concentration on the length and concentration of nitrogen in nanotubes was studied. Micro-structural features of the nanotubes were monitored employing scanning and transmission electron microscopic techniques. SEM studies reveal that with decreasing ferrocene concentration from 25 mg ml(-1) to 5 mg ml(-1), the length of the nanotubes vary from 80 microm to 430 microm. A feasible growth model has been described and discussed. X-ray photoelectron spectroscopic studies have confirmed the formation of nitrogen-doped carbon nanotubes. These studies reveal that the nitrogen concentration in the nanotubes decreases with the increase of ferrocene concentration. The present synthesis route also provides means of producing carbon nanotubes with different concentrations of nitrogen.     

Formation of carbon nanotubes without iron inclusion and their alignment through ferrocene and ferrocene-ethylene pyrolysis

So far carbon nanotubes grown from the method most common method at present, that is, pyrolysis of ferrocene, invariably contains Fe inclusion. In addition, they are generally grown in random configurations. In the present investigations CNTs without Fe inclusion and in aligned configurations have been prepared by the pyrolysis of ferrocene (C10H10Fe) as well as pyrolysis of ferrocene in the presence of ethylene (C2H4). This has been achieved through optimization of growth parameters, for example, heating rate of ferrocene, pyrolysis temperature, and flow rates of carrier gas argon (Ar) and ethylene (C2H4). The as-synthesized samples have been characterized by transmission and scanning electron microscopic techniques. The optimum results relating to synthesis of carbon nanotubes without Fe inclusion and in aligned configurations have been obtained at 1000 degrees C pyrolysis temperature under flow rates of Ar of approximately 1000 sccm and of C2H4 of approximately 100 sccm. These carbon nanotubes have been found to have an outer diameter between approximately 20 and 60 nm and lengths between approximately 15 and 20 microns.     

Carbon nanotubes from catalytic pyrolysis of deoiled asphalt

High purity and uniform carbon nanotubes with about 35 nm in diameter were produced by pyrolysis of deoiled asphalt in the presence of ferrocene in an atmosphere of hydrogen and argon at 1000 °C. Characterization of carbon nanotubes was carried out by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray energy dispersive spectroscopy (EDS), Raman spectroscopy and X-ray diffraction (XRD). The carbon nanotubes were highly graphitized with amorphous carbons covering the outside wall. The influence of temperature on the preparation of carbon nanotubes was also discussed.     

Synthesis of carbon nanotubes by swirled floating catalyst chemical vapour deposition method

A series of developments have been made in synthesizing Carbon Nanotubes (CNTs) by Catalytic Vapour Deposition (CVD) methods since its discovery as a possible route to the large scale and high quality production of CNTs. In this study, CNTs were synthesized continuously in a swirled floating catalytic chemical vapour deposition reactor using acetylene as carbon source, ferrocene as catalyst, with argon and hydrogen as carrier gases within the temperature range of 900-1050 degrees C. The effects of pyrolysis temperature, acetylene flow rate, hydrogen flow rate, and ratio of flow of acetylene to hydrogen on the rate of production of CNTs were investigated. The CNTs produced were purified with dilute nitric acid and the nature and quality of the CNTs were analysed by TEM, Raman spectrometer, EDX, and TGA. Results obtained revealed that a mixture of single and multi wall carbon nanotubes were produced continuously with a maximum yield rate of 0.31 g/min at 1000 degrees C and a flow ratio of acetylene to hydrogen of one to five.     

The growth of aligned carbon nanotubes on quartz substrate by spray pyrolysis of hexane

Vertically aligned multiwall carbon nanotubes were grown by spray pyrolysis of hexane as the carbon source in the presence of ferrocene as catalyst precursor on a quartz substrate. In recent work we used optimal experimental parameters for the feeding method, reactor conditions, reaction temperature and time, concentration of catalyst and flow rate of feed and gas. The process parameters were chosen so as to obtain multiwall carbon nanotubes and aligned multiwall carbon nanotubes. The tubes are around 15-80?nm in diameter. The morphology and structure of the samples were characterized by x-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy analyses.     

Synthesis of carbon and carbon–nitrogen nanotubes using green precursor: jatropha-derived biodiesel

The jatropha-derived biodiesel, a green precursor was found to be a new and promising precursor for the synthesis of carbon nanotubes (CNTs) and carbon–nitrogen (C–N) nanotubes. The CNTs and C–N nanotubes have been synthesised by spray pyrolysis of biodiesel with ferrocene and ferrocene–acetonitrile, respectively, at elevated temperature under an argon atmosphere. The typical length and diameter of as-grown CNTs are 20?µm and 20–50?nm, respectively. The C–N nanotubes are found in bundles with effective length of ～30?µm and diameter ranging between 30 and 60?nm with bamboo-shaped morphology. The as-grown CNTs and C–N nanotubes were characterised through scanning and transmission electron microscopes, X-ray photoelectron, Raman and Fourier transform infrared spectroscopic techniques. These investigations revealed that the nanotubes synthesised by jatropha-derived biodiesel are clean from carbonaceous impurities and the bamboo compartment formations in C–N nanotubes are due to nitrogen incorporation. The nitrogen concentration in C–N nanotubes decreases with the increase in synthesis temperature.     

Synthesis of multi-walled and single-walled nanotubes, aligned-nanotube bundles and nanorods by employing organometallic precursors

 Pyrolysis of organometallic precursors such as metallocenes and iron pentacarbonyl as well as of their mixtures with hydrocarbons such as acetylene or benzene has been carried out under a variety of conditions to synthesize nanotubes. While the use of benzene as a hydrocarbon source generally yields multi-walled nanotubes, it has been possible to obtain single-walled nanotubes (∼1 nm diameter) by pyrolyzing a metallocene or a mixture of metallocenes along with acetylene under a high flow rate of Ar. These experiments show that the organometallic precursor produces small nanoparticles of ∼1 nm diameter which then catalyze the formation of the single-walled nanotubes. Copious quantities of aligned-nanotube bundles have been obtained by the pyrolysis of acetylene in the presence of high concentrations of ferrocene. Nanorods have been produced by the pyrolysis of ferrocene under vacuum. Single walled nanotubes can be filled or decorated by metals. Received: 31 July 1998 / Accepted: 28 August 1998     

环己烷浮游催化法在碳纤维表面生长碳纳米管

以环己烷为碳源、二茂铁为催化剂前躯,采用浮游催化法成功的在碳纤维表面生长了碳纳米管(CNT),制备了多尺度杂化材料CNTs/CF。实验重点考察了反应温度、二茂铁浓度、载气等参数对CNT在纤维表面生长的影响,通过扫描电镜(SEM)、投射电镜(TEM)研究了CNTs/CF的形貌及产物CNT的微观结构。当固定反应温度为820℃、二茂铁-环己烷浓度为2g/100mL时,随着氢气在载气中含量在0～100%范围内变化,产物CNT直径亦有86nm降低至39nm。通过单丝拉伸测试发现,相比初始碳纤维,不同长度的CNTs/CF单纤维强度下降幅度均在10%以内。     

Co催化热分解制备弯曲状碳纳米管的研究

用Ｃｏ催化剂催化热分解乙炔制备碳纳米管,考察了工艺参数对碳纳米管收率及其同结构的影响,得到了较好的工艺流程,同时运用ＴＥＭ、ＨＲＴＥＭ及拉曼光谱对其微观结构进行了分析,并对生长机理做了初步的探讨。     

工业级原料制备碳纳米管的研究

为降低碳纳米管批量制备的原料成本,以焦化苯和二茂铁为主要原料(工业级),采用浮游催化热解法制备碳纳米管,用TEM、SEM、Raman、XRD等对产物的形貌和结构进行观察和表征,着重讨论了二茂铁的分解温度和苯的挥发温度对碳纳米管的制备及其形貌的影响,并对其影响机理进行了分析.研究表明:在噻吩体积分数为0.55 mL/100 mL苯、炉膛反应温度为1170℃的前提下,当二茂铁的分解温度为150℃、苯的挥发温度为50℃时,用工业级原料完全可以制备出碳纳米管,此时,碳纳米管的内径分布在0.88~1.15 nm.     

Influence of the crystallinity of the iron catalysts on the formation of carbon nanotubes

In this work, carbon nanotubes and minor amount of Fe/C core-shell structure nanoparticles were simultaneously synthesized by catalytic pyrolysis of ferrocene. Through high-resolution TEM observation and ED characterization, the results showed that the well-crystallized iron nanoparticles could catalyze the formation of carbon nanotubes, while the amorphous iron nanoparticles could not catalyze the formation of carbon nanotubes but form the Fe/C core-shell nanoparticles.     

Bulk synthesis of carbon nanocapsules and nanotubes containing magnetic nanoparticles via low energy laser pyrolysis of ferrocene

A one-step synthesis route to carbon nanocapsules and nanotubes containing Fe and Fe₃C nanoparticles is reported. Low power laser assisted pyrolysis of ferrocene yielded carbon nanocapsules (30-100 nm in diameter) and multi-wall carbon nanotubes (30-80 nm in diameter). The developed route is fast and enables one to synthesize the products at a rate of 84 mg/min. The iron content in the product (10-42 wt.%) can be varied by modulating the buffer gas pressure during the synthesis process.     

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。      

Epoxy composite with milimetric carbon nanotubes

Composite of multi-walled carbon nanotubes (MWCNT) and epoxy resin DGEBA were obtained with DDM hardener. The MWCNT were synthesized with length of millimeters by camphor/ferrocene pyrolysis. Different cure temperatures of DGEBA/DDM with addition of up to 1% MWCNT were studied to evaluate eventual changes in cure kinetics by differential scanning calorimetry (DSC). No change was detected in glass transition temperature with insertion of MWCNT although the cure enthalpy has been reduced.     

Novel vapor phase reactions for the synthesis and modification of carbon nanotubes and inorganic nanowires

Several vapor phase methods have been developed for the preparation and modification of carbon nanotubes and inorganic nanowires. Thus, nebulized spray pyrolysis has been employed for the synthesis of carbon nanotubes and metal nanowires. Multi-walled carbon nanotubes (MWNTs) with fairly uniform diameters and aligned nanotube bundles have been obtained by nebulized spray pyrolysis using solutions of organometallics such as ferrocene in hydrocarbon solvents. Single-crystalline nanowires of zinc, cadmium, cobalt, and lead are obtained by the decomposition of metal acetates. By reacting acid-treated carbon nanotubes with vapors of metal halides, followed by reaction with water and calcination chemically-bonded oxide layers can be obtained on the nanotubes. A similar procedure has been employed to prepare chemically-bonded oxide layers on Al2O3, ZnO, and silicon nanowires by the reaction of the metal halides with the surface hydroxyl groups present on these nanowire surfaces.