MPCVD法在碳纤维上制备碳纳米管

利用微波等离子体化学气相沉积（MPCVD）法在碳纤维上制备了碳纳米管,并在此基础上系统地研究了微波功率、反应时间、催化剂前驱体的吸附时间以及吸附浓度对碳纳米管生长的影响.采用扫描电子显微镜（SEM）对样品的表面形貌进行表征.结果表明,微波功率、反应时间对碳纳米管的形貌有很大影响,此外,随着吸附时间的增加,碳纳米管的生长速度快且产量高;吸附浓度很大时,碳纤维表面上产生了大量的无定形碳和石墨,严重影响了碳纳米管的生长质量.     

碳纳米管薄膜的制备及场发射特性研究

在镀铝硅片上电沉积Ni催化剂,采用催化热解法制备了多壁碳纳米管薄膜,反应气体为乙炔、氢气和氮气。实验表明在电沉积液中加入正硅酸己酯作催化剂载体并进行退火后处理能有效减小碳纳米管管径．分析表明该纳米管直径在50～70nm间。测试了其场发射特性,其开启场强为8V／μm。最大发射电流密度为2mA／cm^2,已基本满足场发射平面显示器对发射电流密度的要求。     

大内径碳纳米管的制备研究

采用化学气相沉积法（chemical vapor deposition）制备碳纳米管．在高温裂解甲烷制备碳纳米管的反应体系中，比较研究了碳酸钠、碳酸钾、碳酸钙和碳酸钡等碳酸盐作为毒物对镍基催化剂和碳纳米管的影响；另外，还考察了裂解温度对碳纳米管的产率和管型的影响。实验中采用气相色谱（gas chromatography）在线检测甲烷的转化率，从而比较镍基催化荆的催化活性；采用透射电子显微镜（transmission electron microscopy）对合成的碳纳米管的外部形貌进行观察。结果发现，无论是从碳纳米管的产率还是形貌，碳酸钠均优于其它几种碳酸盐，内管径可达到70-80nm，另外还发现，750℃为此法制备碳纳米管的最佳裂解温度。     

垂直定向碳纳米管的化学气相沉积法制备及其应用进展

垂直定向碳纳米管独特的结构和性能使其成为碳纳米管领域的研究热点,而可控制备是其重点研究方向之一。概述了近年来垂直定向碳纳米管的常用制备方法(热化学气相沉积和等离子体增强化学气相沉积)及其影响因素,以及垂直定向碳纳米管在热界面、光电、场发射和传感器方面的研究进展,重点介绍了一些具有优异性能的研究领域以及存在的问题。     

金属基底上定向碳纳米管阵列的生长及其场发射性质

在金属基底上,以铁为催化剂,硅做过镀层,乙烯为源气体,通过普通的化学气相沉积方法生长出垂直基底排列的碳纳米管(CNT)阵列.扫描电子显微镜和透射电镜观察表明,生长的CNT具有阵列形貌和多缺陷的结构.对CNT阵列的场发射性质进行了测量,在10 μA/cm2时不锈钢和镍基底上的开启电场分别为1.25 V/μm 和1.57 V/μm.     

定向/有序碳纳米管制备的研究进展

综述了国内外有序、定向碳纳米管制备的研究进展。着重介绍了模板法和等离子体增强化学气相沉积技术在碳纳米管制备方面的应用，并就制备原理、影响因素等作了简单介绍。     

定向碳纳米管薄膜的制备研究

采用化学气相沉积法制备了定向碳纳米管薄膜,研究了向反应室载入水、氨水对定向碳纳米管薄膜的影响,并用SEM、TEM、XRD对碳纳米管进行了表征。结果表明：向反应室载入水的量增大,定向碳纳米管的长度先增加后减小。载入水的氩气流量为400ml／min,定向碳纳米管的长度1750μm;向反应室载入氨水,得到疏密相间排列的定向碳纳米管薄膜,氨水量增加,定向碳纳米管薄膜的厚度减小。     

树状取向碳纳米管阵列的制备

采用在Ar气氛保护下裂解FePc制备出一种树状取向碳纳米管阵列(ACNTA),这种种特殊结构是由ACNTA裂缝自组装而成.在生长过程中裂缝处能获得更多的催化剂和碳源,因此自身能够持续发展,且裂缝以60°或120°夹角再次分裂,最终形成树状结构.     

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。     

化学气相沉积法制备多壁碳纳米管

以带程序升温装置的管式电阻炉为实验装置,采用化学气相沉积法,在一定的工艺条件下裂解二茂铁与双鸭山精煤的混合物制备出多壁碳纳米管.采用透射电镜、Raman光谱以及X射线衍射技术对碳纳米管产物进行表征,同时研究了碳纳米管的生长机理.     

Nitrogen-doped carbon nanotube arrays grown on graphene substrate

Nitrogen-doped carbon nanotube (N-doped CNT) arrays have been synthesized on graphene substrate by chemical vapor deposition process, in which iron nanoparticles (NPs) assembled on the graphene sheet were generated in situ from the reduction of Fe₃O₄ NPs/reduced graphene oxide (RGO) and were used as catalyst. The morphology and structure of the N-doped CNT arrays were investigated by field emission scanning electron microscope and high-resolution transmission electron microscope. The N-doped CNTs were bamboo-shaped and the density can be controlled by modulating the density of catalyst NPs on RGO sheets. The concentration and incorporation of nitrogen were studied by elemental analysis, X-ray photoelectron spectroscope and Raman analysis, and the results showed that the nitrogen content was around 3 wt.%. Because of the good conductivity of graphene structure, N-doped CNT arrays grown on graphene substrate may be promising candidates as noble metal-free electrodes for oxygen reduction reaction in the future.     

Cell viability and adhesion on as grown multi-wall carbon nanotube films

This work studies cell viability and cell adhesion on as-grown dense films of vertically aligned carbon nanotubes. Microwave plasma CVD reactor was used to produce quite pure carbon nanotubes. Fibroblast L929 mouse cells were used. MTT assay was used for the study of cell viability. The results show very high cell viability, close to 100% after 96 h of incubation. Cell adhesion was observed by scanning electron microscopy, which shows a first cell layer spreading flat on the surface formed by the nanotube tips. This first layer seems to block cell interaction with the nanotubes since next layers present normal globular growth.     

原位生长缺陷碳纳米管化学修饰电极的研制

利用浸渍法将碳纳米管(CNT)催化剂附着在石墨电极表面,用化学气相沉积法制备得到原位生长碳纳米管化学修饰电极(GSCNT-CME).通过控制催化剂及反应气体的配比,在石墨电极表面得到的管壁多缺陷的CNT,研究表明这种 GSCNT-CME具有良好的电化学检测性能.研究还发现这种GSCNT-CME具有高稳定性的原因是CNT是基于石墨电极上碳原子的晶格而生长的.     

不同催化剂作用下生长的碳纳米管和碳纳米纤维复合膜的电吸附性能

采用低压低温气相沉淀法在不同催化剂(Fe和Ni)作用下制备碳纳米管-碳纤维复合薄膜,并研究其电容去离子行为,结果表明:在Ni催化作用下石墨上生长的碳纳米复合薄膜电极的去离子能力比Fe催化作用下生长的碳纳米复合薄膜电极的强;并且碳纳米复合薄膜的电吸附遵循langmuir单层等温吸附.     

X-ray image resolution of carbon nanotube emitters grown with resist-assisted patterning process

We obtained X-ray images using carbon nanotube arrays. The electron emitter was fabricated using the resist-assisted patterning (RAP) process. The X-ray image was obtained with a current of 300 μA at an anode bias of 30 kVp. The emitter had a pattern width of 5 μm and a pitch of 40 μm producing a turn-on field of 1.5 V/μm with a field emission current of 10 μA/cm². The resulting X-ray image clearly shows micrometer scale lines on an integrated circuit chip bonded in a printed circuit board.     

Tunable MEMS capacitors using vertical carbon nanotube arrays grown on metal lines

In this work, tunable MEMS capacitors are realized using a vertically grown carbon nanotube array. The vertical CNT array forms an effective CNT membrane, which can be electrostatically actuated like the conventional metal plates used in MEMS capacitors. The CNT membrane is grown on titanium nitride metal lines, with a Al/Fe bi-layer as buffer layer and catalyst material respectively, using chemical vapor deposition process. Two different anchor configurations are investigated. A maximum capacitance of 400 fF and maximum tunability of 5.8% is extracted from the S-parameter measurements. Using the tunable MEMS vertical array capacitor a voltage controlled oscillator (VCO) is demonstrated showing promise for integrating CNTs for communications applications.     

硅基底上热解法生长CNT薄膜的强流脉冲发射特性

采用酞菁铁高温热解方法在直径为5cm的硅基底上生长了定向CNT薄膜,并对其强流脉冲发射特性进行了表征.测试结果表明,在单脉冲条件下,当宏观场强为11.7V/μm时,发射脉冲电流的峰值约为109.4A;而在双脉冲模式下,当第一脉冲峰值宏观场强为8.6V/μm,第二脉冲峰值宏观场强为5.4V/μm时,第一脉冲和第二脉冲峰值...     

Root growth of multi-wall carbon nanotubes by MPCVD

This work examines the relationships among the growth and interlayer reactions of carbon nanotubes (CNTs) to develop an effective process for controlling the nanostructure, orientation and characteristics of CNTs. Vertically oriented CNTs were successfully synthesized by microwave plasma chemical vapor deposition (MPCVD) with CH₄/H₂ as source gases. Additionally, the Ti and SiO₂ barrier layers and the Co catalyst were used in an experiment on the growth of CNTs on the Si wafer. Then, the SiO₂ barrier layer was deposited by low-pressure chemical vapor deposition (LPCVD). The Ti barrier layer and Co catalyst films were deposited on the Si wafer by physical vapor deposition (PVD). The deposited nanostructures were characterized by scanning and transmission electron microscopy, the results of which reveal that the deposited MWCNTs were grown under the influence of a catalyst on Si substrates with or without a barrier layer, by MPCVD. Vertically grown, dense MWCNTs attached to a catalytic film demonstrate that various MWCNTs penetrated the root particles. The diameter of the root particles, of approximately in the order of 100 nm, is larger than those of the tube, 10–15 nm. The well-known model of the growth of CNTs includes base- and tip-root growth. The interaction between the catalytic film and the supporting barrier layer is suggested to determine whether the catalytic particles are driven up or pinned down on the substrate during the growth.     

Dynamics of carbon nanotube growth from fullerenes

The growth of double-walled carbon nanotubes from peapods was studied. The transformation was monitored by the decrease of fullerene Raman lines, the growth of inner tube Raman lines, and the development of X-ray diffraction patterns. A visual check of the growth process by HRTEM provided additional information. From the difference in time constants for the bleaching of fullerene Raman lines and for the growth of nanotube Raman lines, the existence of an intermediate phase was concluded that was eventually observed in X-ray diffraction and HRTEM. Time constants for the growth of large diameter inner tubes were up to a factor two larger than for small diameter inner tubes. The results fully support the fullerene coalescence growth model triggered by Stone-Wales transformations.     

Electrochemical characterization of carbon nanotube forests grown on copper foil using transition metal catalysts

Growth of vertical, multiwalled carbon nanotubes (CNTs) on bulk copper foil substrates can be achieved by sputtering either Ni or Inconel thin films on Cu substrates followed by thermal chemical vapor deposition using a xylene and ferrocene mixture. During CVD growth, Fe nanoparticles from the ferrocene act as a vapor phase delivered catalyst in addition to the transition metal thin film, which breaks up into islands. Both the thin film and iron are needed for dense and uniform growth of CNTs on the copper substrates. The benefits of this relatively simple and cost effective method of directly integrating CNTs with highly conductive copper substrates are the resulting high density of nanotubes that do not require the use of additional binders and the potential for low contact resistance between the nanotubes and the substrate. This method is therefore of interest for charge storage applications such as double layer capacitors. Inconel thin films in conjunction with Fe from ferrocene appear to work better in comparison to Ni thin films in terms of CNT density and charge storage capability. We report here the power density and specific capacitance values of the double layer capacitors developed from the CNTs grown directly on copper substrates.