The growth of carbon nanotube with chemical vapor deposition under different process parameters

Whether the active catalytic species are in a liquid,solid phase,surface premelting or surface processes during CNT or other nanowire growth are controversial.In order to explore the mechanism for catalytically grown carbon nanotube (CNT),the mechanism for CNT grown under different temperatures was proposed tentatively.With ethanol chemical vapor deposition (CVD),carbon n.anotubes (CNTs) were synthesized controllably on Si substrates using cobalt (Co) as a catalyst.The effects of the Co particle size,growth...     

Study on the Pyrolytic Carbon Generated by the Electric Heating CVD Method

A new method of fabricating C/C composite materials, namely electric heating CVD method, was used, which electrified the carbon fiber directly by using the conductivity of itself. Acetylene was used as the carbon source with nitrogen as dilution gas, and the pyrolytic carbon started to deposit on the carbon fiber surface when the deposition temperature was reached. The morphology of pyrolytic carbon was characterized by SEM, and the surface properties of carbon fibers before and after CVD were characterized by Raman spectroscopy. The experimental results show that the electric heating method is a novel method to fabricate C/C composite materials, which can form a dense C/C composite material in a short time. The order degree and the average crystallite size of the carbon fiber surface were decreased after the experiment.     

微波合成PtRu/CNTs催化剂及其电催化性能

为了获得有良好电催化活性的碳负载铂钌合金的催化剂，提出一种快速均匀的微波辐射加热的多元醇方法.用氯铂酸和氯化钌的乙二醇溶液为前驱体，碳纳米管（CNTs）为载体，采用该方法合成了PtRu/CNTs电催化剂.利用透射电镜(TEM)、X-射线衍射(XRD)和能量散射X 射线能谱（EDX）对催化剂进行了表征,并用循环伏安实验评价了催化剂对甲醇电化学氧化的电催化活性．结果表明，PtRu合金纳米粒子具有均匀的粒径，在2.0~4.0 nm之间，平均粒径为3.4 nm，并高度分散在CNTs表面．PtRu/CNTs电催化剂对甲醇的电化学氧化具有良好的电催化活性.     

金属镍在碳纳米管薄膜上的电结晶

为了使碳纳米管表面产生某些含氧官能团,使其疏水性表面变为亲水性表面,采用兼具有酸性和氧化性的硝酸和硫酸水溶液对碳纳米管进行表面氧化处理,并利用红外光谱表征了碳纳米管的表面结构.制备了初始浓度为0.5g/L的碳纳米管悬浮液,运用复合电沉积方法在不锈钢基体表面制备碳纳米管薄膜,同时在硫酸镍基础电解液中研究了沉积时间对镍晶粒在碳纳米管薄膜上沉积的表面形貌和微观结构的影响.结果表明:经过混酸氧化处理后的碳纳米管表面拥有丰富的羧基和羟基等含氧官能团;沉积初期镍晶粒在碳纳米管薄膜中的结晶形态呈颗粒状,其结晶位置仅位于碳纳米管表面少数部位,随着沉积时间的延长,镍晶粒在碳纳米管薄膜中逐渐形成准连续的金属层.此外,碳纳米管的存在促进了镍晶粒(111)晶面的生长,影响了特征峰相对强度的变化及晶粒尺寸的减小.     

碳纳米管受介电泳作用三维运动仿真

利用溶于介电液中的碳纳米管在外加交变电场作用下极化产生介电泳力和液体粘滞阻力的共同作用,建立了碳纳米管受力和运动模型;对碳纳米管的运动过程进行了仿真,得到了碳纳米管从特定初始点开始的三维运动轨迹和可以实现组装的碳纳米管初始点分布区域.计算了碳纳米管运动过程中所受介电泳力和速度的变化规律,距离电极间隙越近,碳纳米管受力和速度越大,最大分别能达到10^-9 N和10⁵μm/s的数量级.仿真结果为碳纳米管介电电泳组装提供指导.     

Oxidation behavior of CNTs and the electric double layer capacitor made of the CNT electrodes

Electric double layer capacitors (EDLCs) have been widely used because they have large capacitance, and are free of maintenance and free from toxic materials. After NEC corporation developed activated carbon/carbon super capacitor, they are expected to be applied to electric vehicles[1]. A unit of EDLCs is based on the double layer capacitance at solid/solution interface of high surface material. As in the case with a traditional electrolytic capacitor, the electrical energy is stored thro…     

沉积法掺金改善碳纳米管电接触特性

研究了沉积法在碳纳米管中掺杂金属金对碳纳米管与金属电极间的电接触特性的影响。首先,采用酸回流方式在碳纳米管表面构造缺陷及亲水官能团并配制碳纳米管分散液;然后,采用柠檬酸钠和氯金酸配制金溶胶溶液,再将配制好的碳纳米管分散液滴入金溶胶溶液中,经震荡沉积得到掺杂金纳米粒子的碳纳米管样品。扫描电子显微图片及红外吸收光谱表明,酸回流成功地在碳纳米管管壁及端部构造了一些缺陷及亲水官能团。形貌表征及X射线光电子谱表明,在碳纳米管表面及端部成功地掺杂了金纳米粒子。掺金后碳纳米管拉曼光谱的G带波数增大,表明该掺杂类型为p型。最后,采用介电电泳法将原样与掺金碳纳米管分别组装到金电极之间,并实时测量接触电阻。结果表明,沉积法掺金可降低碳纳米管与金电极间的接触电阻,其阻值平均降幅高达71.49%。     

Optimizing electrophoretic deposition conditions for enhancement in electrical conductivity of carbon fiber/carbon nanotube/epoxy hybrid composites

The effectiveness of optimizing electrical conductivity of carbon fiber/carbon nanotube (CNT)/epoxy hybrid composites via Taguchi method was demonstrated.CNTs were induced on carbon fabric by electrophoretic deposition (EPD) technique.The essential deposition parameters were identified as 1) the deposition time,2) the deposition voltage,3) the mass fraction of CNTs in suspension,and 4) the distance between the electrodes.An experimental design was then performed to establish the appropriate levels for each factor.An orthogonal array of L9 (34) was designed to conduct the experiments.Electrical conductivity results were collected as the response.The relative influences of design parameters on the response were discussed.Using the model,signal to noise (S/N) ratio and response characteristics for the optimized deposition parameter combination were predicted.The results show clearly that the optimum condition of electrophoretic deposition (EPD) process improves the electrical conductivity of carbon/epoxy hybrid composites.     

Effect of radial heat conduction on effective thermal conductivity of carbon nanotube bundles

The effect of the radial heat conduction on the effective thermal conductivity of carbon nanotube (CNT) bundles is studied by the nonequilibrium molecular dynamics (NEMD) method. The hexagonal CNT bundle consists of seven (10, 10) single-walled carbon nanotubes (SWCNTs). The radial heat conduction is induced by creating the vacancy defects in some segments of the constituent CNTs. Combined with the temperature differences and the inter-tube thermal resistances at the different segments, the radial heat flow in the CNT bundle is calculated. The maximum percentage of the radial heat flow is less than 7% with the presence of four defective CNTs, while the resultant decrement of the effective thermal conductivity of the bundle is about 18%. The present results indicate that the radial heat flow can significantly diminish the axial heat conduction in the CNT bundles, which probably explains the smaller effective thermal conductivity in the CNT assemblies compared to that of the individual CNTs.     

Synthesis of carbon nanotubes with Ni/CNTs catalyst

Solid catalysts are widely used in industrial processes; their catalyses are closely related to not only the active elements but also support materials. The catalytic support plays the role of in-creasing surface area, dispersing active elements, improving heat resistance and mechanical strength. So it is requested that materials used as catalyst support should have excellent mechani-cal properties, enough thermal stability, proper pore structure and large surface area. The com-monly used supp…     

制备工艺对CNTs/EP复合材料性能的影响

采用溶液共混法制备碳纳米管(CNTs)/环氧树脂(EP)复合材料,主要研究丙酮用量、混合方式、超声时间、CNTs含量等制备工艺对复合材料的热性能和导电性能的影响.通过用SEM、DSC,TGA以及万用表对复合材料进行分析表征,结果表明,丙酮的加入量越多,超声时间越长,CNTs/EP的复合材料的导电性越好,CNTs在复合材料中分散性也好,而随着CNTs含量增加,复合材料的导电性按照逾渗理论的规律提高,且逾渗闶值出现在0.5 0A～1%范围内.利用超声处理伴随着搅拌这种混合方式所得复合材料的导电性最好,加入碳纳米管的复合材料玻璃转化温度Tg和热稳定性能较纯EP有显著提高.     

Processes of depositing platinum on carbon nanotubes and their effecton performance of proton exchange membrane fuel cell

The ultrafine platinum nanoparticles deposited on the surfaces of carbon nanotubes (Pt/CNTs) were prepared by a chemical precipitation method and used as the catalyst of proton exchange membrane fuel cell. The depositing process parameters such as the solution pH value, Pt content and treatment temperature were analyzed. The experimental results show that the optimum process parameters to prepare Pt/CNTs are the solution pH value of 7.0, the theoretical Pt content of 25% (mass fraction) and the heating temperature of 500~C, under the conditions the best performance of the proton exchange membrane fuel cell can be obtained and its voltage can reach 580 mV at a current density of 500 mA/cm2.     

碳纳米管负载金属纳米粒子的研究进展

碳纳米管(carbon nanotubes, CNTs)具有优异的导电性能、导热性能和高的热稳定性。将具有独特催化性能、导电导热性能的金属纳米粒子(metal nanoparticles, M-NPs)负载至CNTs表面形成复合材料,可以广泛应用于催化和热管理领域。综述了国内外制备负载M-NPs的CNTs的研究现状,包括共价和非共价两种方式功能化CNTs再负载M-NPs和直接通过化学气相、物理和电化学沉积等方法将M-NPs负载至CNTs上。共价功能化的CNTs表面虽然可以将其他物质分子永久稳定地连接,但是sp~2到sp~3的杂化过程导致电子结构重组,改变了CNTs原有的电子离域,破坏了CNTs的热学、光学等本征特性,因此使用非共价改性的方法,不仅可以保持CNTs原有的结构和性能,而且不会破坏π共轭体系。M-NPs直接负载至CNTs表面的方法中绿色简便,可大规模推广制备的是混合加热法,不需要添加其他溶剂,也不需要任何精密仪器,就可以使金纳米粒子均匀密集高效地负载至CNTs表面生成复合材料。由此可见,更加绿色高效的M-NPs修饰的CNTs复合材料制备方法在能源、环境和热管理领域的应用前景越来越光明。     

接触热阻对相变耦合温差发电系统的影响

在汽车尾气温差发电系统中, 热量在传递的过程中通常要经过若干个接触界面。而界面间的接触热阻影响 着热量的传递效率和热电器件冷热两侧的实际温差, 进而影响到系统的发电性能。利用工业热风机模拟汽车运行实 际工况, 使用装载有相变材料(phase change material, PCM) 的温差发电系统, 通过涂抹不同导热系数的导热硅脂来 调节热电器件与系统间的接触热阻, 研究了接触热阻对PCM 以及系统输出电压的影响。研究发现, 同时减小热电 器件两侧与系统间的接触热阻会削弱PCM 的储热能力; 相较于减小热电器件热面与系统间的接触热阻, 减小热电 器件冷面与冷端换热器间接触热阻, 对温差发电系统输出电压的提升效果更为显著。     

Laser tuned field emission of the carbon nanotube arrays grown on an optical fiber

Laser was coupled into an optical fiber,on which covered a layer of well-aligned carbon nanotubes(CNTs)serving as cathode,to tune the field emission of the cathode.CNT arrays as field emission cathode were synthesized by chemical vapor deposition(CVD)on a naked fiber core.When the laser was coupled into the fiber,the turn-on voltage(Vto at a current density of 1 mA cm?2)decreased from 1.0 to 0.9 kV and the emission current density increased from 0.83 mA cm?2(at a 1 kV bias voltage)to3.04 mA cm?2 on 40μm diameter fiber.A photon absorption mechanism is attributed to the field emission improvement.The estimated effective work function of CNT arrays on the optical fiber decrease from 4.89 to 4.29 eV.The results show the possibility of constructing a waveguide type laser modulated field emission cathode.     

Synthesis of carbon nanofibers by ethanol catalytic combustion technique

A general, simple and economic synthetic method for synthesizing carbon nanofibers was presented. In the method, ethanol was employed as carbon source; metal salts such as nickel nitrate, ferric nitrate and ferric chloride were used as catalyst precursor respectively; copper plate was employed as the support material. A lot of products were obtained by catalytic combustion deposition of ethanol vapor. Then the as-prepared carbon nanofibers were characterized by field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, energy dispersion X-ray spectroscopy and selected-area electron diffractometry. By analyzing the results of characterization, the conclusions are as follows： 1） the large catalyst particles tend to form large-diameter CNFs, small catalyst particles are inclinable to form small-diameter CNFs; 2） the morphology of the catalyst can affect the final morphology of the CNFs. Moreover, the possible growth mechanisms were proposed and the degree of graphitization of samples was estimated by Raman spectroscopy characterization.     

以焦化苯为碳源制备碳纳米管的研究

以工业副产品—焦化苯为碳源,以二茂铁为催化剂前躯体,以噻吩为生长促进剂,采用催化裂解（CVD）法,在合适的工艺条件下,制备了碳纳米管（CNTs）,采用TEM,XRD和Raman对所得碳纳米管进行表征,考察其形貌及石墨化程度,结果表明：在一定工艺条件下,以焦化苯为碳源可以制备出形貌规整、长径比大、缺陷少且纯度高的碳纳米管。还探讨了反应温度和反应时间对碳纳米管形貌和产率的影响。     

化学气相沉积法制备碳纳米管有序阵列

采用化学气相沉积法（CVD）在覆盖有催化剂薄膜的硅片表面直接制备出碳纳米管阵列,使用透射电镜（TEM）和场发射扫描电镜（FESEM）对其进行了检测,并探讨了实验条件对碳管形貌的影响。结果表明：所制备的碳管具有明显的取向性,能够形成致密有序的碳纳米管阵列;制备催化剂所用的硝酸铁溶液浓度为2mol／L时,最适宜碳管阵列的生长;匀胶机的转速提高,可减小催化剂颗粒直径,增强颗粒分散性,有利于碳管生长;碳纳米管的直径随反应温度的升高和时间的延长而增加,680℃为最佳反应温度;碳管生长模式为顶部生长和底部生长。     

无定形纳米碳管的合成、表征及其纯化后的电化学性能

以焦粉制备的碳棒为碳源,以镍为催化剂,在负压条件下,于乙炔和氦气气氛中,采用电弧法合成了无定形纳米碳管（ACNT）。利用扫描电镜、透射电镜,X-射线衍射仪和拉曼光谱对产物进行表征。采用微波辅助硝酸纯化法对制备的ACNT进行纯化,并进一步在空气中纯化。用纯化后的纳米碳管修饰碳糊电极,利用循环伏安法测试了电极的电化学性能。结果表明,电极具有良好的电化学稳定性,ACNT管壁上的羟基基团被氧化而减少,导致无定形纳米碳管／碳糊电极电子传递速度减慢。     

Growth of Ag nanocrystals on multiwalled carbon nanotubes and Ag-carbon nanotube interaction

The experimental investigations on the interaction between Ag-nanocrystal particles (Ag-NCPs) and carbon nanotubes (CNTs) in Ag-nanocrystal particles/carbon nanotubes (Ag-NCPs/CNTs) hybrid structures were reported. The growth of Ag-NCPs on multiwalled carbon nanotubes (MWCNTs) was carried out by thermal evaporation deposition. High-resolution transmission electron microscopy and X-ray diffraction analyses revealed that Ag-NCPs had the crystal lattice feature of face-centered cube (fcc). The growth of Ag-NCPs on MWCNTs induced the cross-section deformation of MWCNT. The experimental results also showed that the synthesized Ag-NCPs/CNTs hybrid structure appeared as quasi-one dimensional nanowires containing the Ag-NCP/CNT hetero-junction. There was local cross-section deformation on MWCNTs at the interface of hetero-junction. These results involve the important topic about fundamental and practical studies for structure of MNCPs on CNTs and also find clues to further research of Ag nanocrystal growing on MWCNTs and related Ag-CNT interaction.