Synthesis of carbon nanotubes by catalytic chemical vapour deposition: A review on carbon sources,catalysts and substrates

Carbon nanotubes (CNTs) have been extensively studied during the past two decades and Catalytic Chemical Vapour Deposition (CCVD) technique has been untiredly employed by researchers to produce CNTs of various crystallographic configurations. In this paper the material aspects carbon sources, catalysts and substrates with regard to CCVD synthesis of carbon nanotubes are reviewed in light of latest developments and understandings in the field. The role of these materials in synthesis of CNTs is explained keeping the upto date literature in view. Latest research reports and their findings are presented with regard to effects of growth control aspects such as temperature, vapour pressure and catalyst concentration on CNT formation. Besides recent understandings with regard to preferential growth of CNTs are also discussed. From this literature review it is found that carbon diffusibility and carbon solubility of any catalyst are two important factors in determining CNT nucleation and growth. Moreover, addition of catalyst species to any transition metal catalyst can improve the catalyst performance and addition of water, air, alcohol etc. during CCVD process can increase the activity and lifetime of the catalyst besides enhances the production of CNTs.     

碳纳米管分散形态的电镜研究

未经处理的碳纳米管常呈现团聚形态。然而，团聚形态对进一步深入研究碳纳米管的性能与应用造成了很大的局限．所以，碳纳米管的有效分散至关重要。现在国内虽已对碳纳米管的分散进行了一定的探索，但却未能对分散务件进行定量标定。本文采取超声波振荡的方法进行分散，并细致、深入地探讨了不同分散务件对碳纳米管分散形态的影响，从而说明选用适当的碳纳米管原料、延长超声振荡时间以及降低悬浮液浓度都将有利于碳纳米管的充分分散。     

Controlling the formation of nanoparticles for definite growth of carbon nanotubes for interconnect applications

Our interest is the integration of carbon nanotubes (CNT) in electronic devices (IC, NEMS). In the scope of this work, we present a study on the preparation of the catalyst Ni particles from ultrathin films and the synthesis of carbon nanotubes by the chemical vapour deposition method. For the preparation, we use a cold-wall CVD reactor especially designed for handling samples up to a size of a 4” wafer. We show the influence of different process conditions like temperature, initial layer thickness of catalyst and substrate on particle formation characterized by scanning electron microscopy (SEM). We show that the optimization of process conditions in the catalyst preparation phase is constitutive for dense CNT films. Regarding the application of CNTs as electrical interconnects, we studied the arrangement of nanoparticles on Al and TiN supporting layer. Furthermore, we fabricated the first test structures for the selective growth of CNTs out of contact holes on a Cu/TiN metallization layer system.The growth of multi-walled nanotubes (MWNTs) was performed with thermal CVD with ethylene as a precursor gas and hydrogen as supporting gas mixed in a nitrogen gas flow. The effects of growth condition on the quality and morphology of the CNTs were characterized by scanning electron microscopy, transmission electron microscopy (TEM) and Raman spectroscopy. The influence of temperature, gas composition and substrate on CNT growth will be presented. We managed to grow dense CNTs even at temperatures as low as 500 °C.     

RF-PECVD法研究碳纳米管的生长特性

采用射频等离子体增强化学气相沉积(RF-PECVD),以Fe作为催化剂,在Si基片上生长了碳纳米管(CNT),采用扫描电子显微镜(SEM),高分辨透射电子显微镜(HR TEM)以及显微Raman光谱等对制备的CNT的形貌及结构进行了表征.结果表明:700℃和800℃温度下生长的CNT均取向无序、弯曲缠结,由整齐排列的圆...     

Field electron emission of multiwalled carbon nanotubes and carbon nanofibers grown from Camphor

Vertically aligned carbon nanofibers (CNF) and multiwalled carbon nanotubes (MWCN) were synthesized from camphor by catalytic thermal chemical vapor deposition on Co and Co/Fe thin films (for CNF) and on silicon substrates using a mixture of camphor and ferrocene (for MWCN). CNF and MWCN were studied by scanning and transmission electron microscopy, visible Raman spectroscopy, X-ray diffraction in order to get insight into the microstructure and morphology of these materials. Field electron emission study indicates turn-on field of about 1.52, 2.3 and 4.3 V/μm for MWCN, Co/CNF and Co/Fe/CNF films, respectively; and threshold field of about 2.48, 3.1 and 6 V/μm, respectively. Our study indicates a better performance for field electron emission compared with some of the earlier published reports which might be due to higher aspect ratio, good graphitization and suitable density.     

一种新的测定多壁碳纳米管中无定形碳含量方法的研究

目前,碳纳米管（CNTs）中无定形碳含量的测定方法很多,但由于测试样品方法不完善和样品预处理的方式不同,导致测量结果有较大差别,实验的可重现性也不好。本文对一种新的测定多壁碳纳米管（MWCNTs）中无定形碳含量的方法进行了研究。该方法基于不同形态碳与CO2反应活性的差异,利用CO2柔性氧化法氧化CNTs,采用热重法（TG）测定CNTs中无定形碳含量。并且,结合拍摄CNTs高分辨电子显微（HRTEM）像,证实通过该方法可使粗品中CNTs相和无定形碳相得以区分,达到了对CNTs中无定形碳进行定量分析的目的。本文也讨论了TG测试过程中的各个影响因素。     

双壁碳纳米管的电子显微学研究

本文分析研究了甲酸镍二水合物作为催化剂前驱体,多壁管为原料,采用氢电弧放电法制得的双壁碳纳米管样品中不同管壁数目碳纳米管的分布及双壁碳管直径分布,发现样品中单壁和双壁碳管占主要地位,双壁管的内径主要分布在1.67 nm～3.67 nm之间,外径主要分布在2.33 nm～4.33 nm之间.此外,精确测定了三个双壁碳纳米管的螺旋指数,分别为[(28,3)(29,17)],[(19,8)(29,6)]及[(23,15)(28,22)],其电学性能分别为[半导体性,金属性],[半导体性,半导体性]及[半导体性,金属性].同时,观察了在不同条件下的电子辐照效应.结果表明,经辐照碳管的最内层管壁先发生断裂,其形变速度逐渐变慢,单根碳管易依附于大块物质.在相同的辐照条件下,管壁数目越多碳管越稳定.当管壁数目相同时,直径小的管比直径大的管稳定.高加速电压能够加速碳管的变形.     

长脉冲强流碳纳米管阴极重频发射特性初步研究

在不锈钢环形阴极基体上,采用高温热解方法直接生长石墨化程度较高的碳碳纳米管阴极,当脉冲电压达到800kV 时,发射相对论电子束流强度高达9.1kA;以5Hz 重复频率发射模式时,发射稳定、其发射阈值介于石墨不锈钢阴极之 间而等离子体扩张速度最低;多次发射后,界面无脱附现象发生。     

阵列式碳纳米管制备研究

CVD工艺制备碳纳米管阵列,二甲苯(C6H4(CH3)2)作为碳源气体,二茂铁(C10H10Fe)作为催化剂前驱体,反应温度为700～800℃,碳纳米管直径30～60nm,长度50～60μm。     

碳纳米管中纳米空间的物质结构

填充碳纳米菅不但能改变碳纳米管本身的电学和力学性质,而且能改变被填充物质的性质.本文就有关多层、双层、单层碳纳米管的管内填充,主要以TEM为表征技术,对碳纳米管内纳米限域空间中物质的结构、性质等的研究作了简要的总结.     

制样溶剂及基底对原子力显微镜观测单壁碳纳米管的影响

本文选用不同基底和溶剂进行单壁碳纳米管(SWNTs)样品制备,采用原子力显微镜(atomic force microscope,AFM)观察进行表征和观测。结果表明,溶剂和基底对样品制备十分重要,会直接影响AFM观测效果。以去离子水为溶剂进行样品分散时,SWNTs在石英、硅片和云母三种基底上都出现了不同程度的聚积和重叠,影响观测效果。而采用乙醇为溶剂,在石英或云母为基底进行成像时,均可获得质量良好的图像。选择云母作为基底,可以大大减少基底处理时间,制样方便快速,并且能够获得理想的观测效果。     

用场发射显微镜测量单壁碳纳米管的逸出功

该文利用场发射显微镜对单壁碳纳米管的逸出功进行了研究和测量。未进行加热除气的单壁碳纳米管的表面吸附大量气体,此时测量的逸出功不是清洁表面单壁碳纳米管的逸出功。实验首先加热除气得到单壁碳纳米管的场发射清洁像,然后利用场发射显微镜测量I-V曲线,得到Fowler-Nordheim直线斜率;再利用透射电镜观测单壁碳纳米管微束形貌像,测量管束半径,通过三种公式估算比例因子,最后计算得到单壁碳纳米管的逸出功。     

碳纳米管团聚结构的电镜研究

纳米聚团床催化裂解法制得的碳纳米管均以团聚体形式存在，本文利用电子显微镜观察了两种碳纳米管团聚体的团聚结构，分散形态及微观结构，研究表明，纳米聚团床催化裂解法制备的碳纳米管具有多级团聚结构，范德华力及缠绕作用共同造成了多级团聚体的形成，细长的碳纳米管分散困难，易絮凝；短小弯曲的碳纳米管易于分散。     

大规模制备定向排列的碳纳米管阵列

采用一种无模板的化学气相沉积法 ,在石英衬底上制备了大面积 ,高定向性、自支撑的碳纳米管阵列。二甲苯和二茂铁分别作为碳源和催化剂 ,连续进给到反应装置中 ,在一定温度条件下 ,碳纳米管自组织生成垂直于衬底方向的定向阵列。这种方法可以获得很高的生长速度 ,其最大长度可以达到几个毫米。拉曼光谱和高分辨透射电镜检测显示这种方法制备的碳纳米管具有较高的纯度和石墨化程度     

Structural and optical properties of functionalized multi-walled carbon nanotubes

Herein, we report the functionalization of multiwalled carbon nanotubes (MWCNTs) using meta-Chloroperoxybenzoic acid (mCPBA) as an oxidizing agent. Epoxy groups are incorporated into the sidewall of MWCNTs and the prepared functionalized multiwalled carbon nanotubes (F-MWCNTs) were characterized using FT-IR spectroscopy, X-ray diffraction, Raman spectroscopy and UV–visible spectroscopy. Morphology of MWCNTs and F-MWCNTs was determined using Scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM results clearly indicated that the diameter of F-MWCNTs is increased by 120% as compared to neat MWCNTs. From UV–visible spectroscopy data, band gap of F-MWCNTs was calculated using Tauc equation and it was found to be 3.9 eV. Photo emission property of F-MWCNTs was analyzed using photoluminescence spectroscopy. F-MWCNTs showed nice emission in the visible region and it depended upon the excited wavelength. These functionalized carbon nanotubes could find use as tunable optoelectronic devices in future nanotechnology.     

硅基底表面上多种形态碳纳米管的生长

以Fe/Ru双金属纳米颗粒为催化剂,在含有一层自然氧化层的硅基底上制备单分散碳纳米管,并用原子力显微镜进行表征。实验结果表明在同一基底上碳纳米管具有多种形态,如环形、树枝状分叉形、锥形,单根和成束等。这种多种形态碳纳米管的出现,为更进一步了解碳纳米管的生长机制以及对控制碳纳米管制备有着重要意义。     

碳纳米管应用研究进展

简要介绍了碳纳米管的基本性能和主要生产方法,综述了碳纳米管应用研究在各领域的进展,展望了碳纳米管的应用前景。     

碳纳米管冷阴极电子枪的电子光学设计

基于皮尔斯电子枪设计理论,提出了一种碳纳米管场致发射阴极电子枪的电子光学设计方案。电子枪阴极半径为0.5 mm,保持阴阳极电压不变,动态调整栅极电压,并利用计算机技术仿真软件（CST）对其进行仿真优化研究;结果表明,栅极最佳电压值为-14 kV,对应阴极发射电流为15.08 mA,阳极处电子束半径约为0.1 mm。研究为碳纳米管冷阴极栅极结构的设计提供了一种新的思路。     

碳纳米管对Ni60激光熔覆层的耐蚀性影响

利用自动送粉激光熔覆技术,在A3钢表面进行了Ni60合金添加碳纳米管的激光熔覆实验,采用静态浸泡法对相同工艺条件下获得的纯Ni60熔覆层和碳纳米管/镍基熔覆层的耐腐蚀性进行研究,在光学显微镜下观察样品表面腐蚀形貌,并对碳纳米管/镍基熔覆层的腐蚀机理进行了分析.结果表明:当碳纳米管的含量为0.3 wt%时,碳纳米管/镍基激光熔覆层的耐腐蚀性能最好,与纯Ni60激光熔覆层相比,耐腐蚀性提高1倍多.碳纳米管/镍基激光熔覆层耐腐蚀的原因在于熔覆层保留的碳纳米管使熔覆层更加致密,隔离了腐蚀介质,促进了镍基合金的钝化,从而提高了熔覆层的耐蚀性;同时,熔覆层中保留下来的碳纳米管和被分解的碳纳米管与金属基体形成碳化物,作为增强相均匀弥散在熔覆层中,它们的存在阻止了腐蚀坑的长大,因而蚀坑较小,耐腐蚀性得到提高.     

Photovoltaic properties of multi-walled carbon nanotubes deposited on n-doped silicon

Multi-wall carbon nanotubes (MWCNTs), grown by catalytic chemical vapor deposition (CCVD) over Fe supported on alumina catalyst, using isobutane as feedstock, are dispersed in aqueous solutions of sodium dodecyl sulfate. Stable and highly photosensitive heterojunctions are developed by liquid-phase deposition of MWCNTs/surfactant mixtures on the top of n-doped monocrystalline silicon wafers. Electrical measurements performed in the dark and under broad-band visible light, show that the hybrid solar cells, despite their non-optimized design, have conversion energy efficiency of the order of 3%.