Cold-wall CVD carbon nanotube synthesis on porous alumina substrates

Carbon nanotubes were synthesized by chemical vapor deposition (CVD) using ethanol vapor as carbon source. Catalysts were Co and Mo metallic particles obtained from the corresponding acetates dissolved in ethanol. Acetate solutions are deposited on porous alumina substrates by dip coating. A dense array of aligned carbon nanotubes perpendicular to the substrate surface grow with 20 min exposure to ethanol vapor flow for substrate temperatures between 650 and 830 °C. Sample analysis is performed with scanning electron microscopy and Raman spectroscopy.     

Bundles of carbon nanotubes grown on sapphire and quartz substrates by catalytic hot filament chemical vapor deposition

Carbon nanotubes were deposited on non-conductive optically transparent sapphire substrates of various crystallographic orientations and on amorphous quartz glass. The substrates were covered by catalysts in which trivalent iron, Fe(III), was the dominant component. The nanotubes were synthesized by catalytic hot filament chemical vapor deposition. During their production, they form bundles composed of multiwalled carbon nanotubes and have a length of up to several tens of micrometers, thickness between 1 and 4 μm, and a non-circular cross-section. The growth of these bundles on a non-porous non-conducting optically transparent substrate was confirmed by scanning electron microscopy and by Raman spectroscopy.     

Synthesis of Well-Crystalline Lattice Carbon Nanotubes via Neutralized Cooling Method

In this contribution, vertically aligned carbon nanotubes were synthesized by chemical vapor deposition (CVD). The effects of intrinsic disorders constructed by mobile surface contaminants on the structural perfection of carbon nanotubes (CNTs) were investigated. The results indicated a complete picture on the effect of the involved parameters on the lattice defects of modulated CNTs based on the cooling step. Raman scattering showed that the different cooling methods of the CVD preforms altered the bound complex defects of the structure of the CNTs. Moreover, an array of CNTs was removed from the silicon substrate by applying the neutralized cooling method on the CVD, while the vertical and parallel orientations were retained. The FESEM images, coupled with Raman spectroscopy results, confirm the morphological improvements of the growth CNTs based on the neutralized cooling method.     

Structure of multiwalled carbon nanotubes grown by chemical vapor deposition

Carbon nanotubes have been grown by chemical vapor deposition at 650°C in an argon atmosphere using a butane-propane mixture and a nickel catalyst and have been characterized by scanning and transmission electron microscopy and Raman spectroscopy. The results indicate that the multiwalled nanotubes have an imperfect graphite-like structure with a conical supramolecular configuration. A phenomenological technique is proposed for statistical analysis of the state of carbon nanotubes in measurements of the intensity of the defect zone D in their Raman spectra.     

催化化学气相沉积法制备螺旋形多壁碳纳米管(英文)

以乙炔为碳源、FeMo/MgO催化剂为模板,采用催化化学沉积法制备了螺旋状多壁碳纳米管(hs-MWC-NTs)。其中FeMo/MgO模板,由作为发泡和助燃剂的柠檬酸燃烧而制成。FeMo/MgO催化剂的XRD谱图揭示其具有微晶的通性。应用SEM、TEM和Raman光谱剖析了合成的炭材料。SEM和TEM观察表明获得了hs-MWC-NTs;Raman光谱的D峰和G峰确认了所获碳纳米管(CNTs)的结晶状态。结果表明:此法乃是合成直径10nm～20nm螺旋形多壁碳纳米管的最容易和简便方法。     

Selective growth of boron nitride nanotubes by plasma-enhanced chemical vapor deposition at low substrate temperature

Hexagonal boron nitride nanotubes (BNNTs) were synthesized at a low substrate temperature of 800?°C on nickel (Ni) coated oxidized Si(111) wafers in a microwave plasma-enhanced chemical vapor deposition system (MPCVD) by decomposition and reaction of gas mixtures consisting of B(2)H(6)-NH(3)-H(2). The 1D BN nanostructures grew preferentially on Ni catalyst islands with a small thickness only. In situ mass spectroscopic analysis and optical emission spectroscopy were used to identify the gas reactions responsible for the BNNT formation. The morphology and structural properties of the deposits were analyzed by SEM, TEM, EDX, SAD and Raman spectroscopy. The growth mechanism of the BNNTs was identified.     

Carbon helixes produced by hot filament assisted chemical vapor deposition

Carbon helix nanofibers were synthesized by a hot filament assisted chemical vapor deposition at a substrate temperature of 600 °C. It was observed that the formation of a carbon helix structure was attributed to the mixing of cobalt catalyst particles with copper. The diameter of carbon helixes varied from 20 to 500 nm. The growth mechanism and the structure of these carbon helix nanofibers are discussed based on scanning electron microscopy and Raman spectroscopy measurements.     

定向碳纳米管的化学气相沉积制备法

报道了一种简便有效的合成定向碳纳米管 (CNTs)的化学气相沉积 (CVD)制备方法。以铁为催化剂 ,乙炔为碳源 ,采用单一反应炉 ,直接在石英基底上沉积催化剂颗粒薄膜 ,成功合成了定向性好、管径均匀的高质量大密度的碳纳米管     

Carbon dioxide as a carbon source for synthesis of carbon nanotubes by chemical vapor deposition

Carbon dioxide was successfully used as carbon source in the synthesis of carbon nanotubes (CNTs) by chemical vapor deposition (CVD) over Fe/CaO catalyst. The product was evaluated using both transmission electron microscopy (TEM) and Raman spectroscopy. Crooked and branching structures of multi-walled carbon nanotubes (MCNTs) with diameters of around 50 nm were observed on the TEM micrographs. Raman spectrum results show that the nanotubes have small defects, which is in agreement with the results of TEM. The influence of reaction variable such as furnace temperature and types of support media was also studied and the reaction mechanism was then discussed in this paper.     

Growth of carbon nanofibers and related structures by combined method of plasma enhanced chemical vapor deposition and aerosol synthesis

Growth of carbon nanofibers and nanotubes by combination of aerosol synthesis and plasma-enhanced catalytic chemical vapor deposition with alcohol as carbon precursor is presented. Only a hollow cathode glow discharge (HCGD) is used as gas activation process without any specific heating of the substrate. Specially designed hollow cathode enables the evaporation of catalyst directly on the substrate for catalytic growth. Product of physical vapor deposition process was examined by energy dispersive X-ray spectrometer (EDS). Spectroscopic features of the plasma were monitored by optical emission spectroscopy (OES). Carbon deposition was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Catalytic nanofibers and multi-walled carbon nanotubes with outer diameters 20-60 nm have been observed.     

The effect of different temperature profiles upon the length and crystallinity of vertically-aligned multi-walled carbon nanotubes

We synthesized vertically-aligned multi-walled carbon nanotubes with an inner diameter of 1.6-7.5 nm and stack height of 80-28600 microm by chemical vapor deposition. The effects of synthesis conditions such as substrate position in the tube furnace, maximum temperature, temperature increasing rate and synthesis duration on the structure of nanotubes were investigated. It was found that slightly faster temperature increase rate resulted in significantly longer length, larger diameter and more defects of nanotubes. Structural parameters such as inner, outer diameters, wall thickness and defects were investigated using transmission electron microscopy and Raman spectroscopy.     

Graphene synthesis by thermal chemical vapor deposition using solid precursor

We report single layer to few layer graphene on polycrystalline nickel by chemical vapor deposition at ambient pressure using solid precursor, camphor. Investigating at a wide range of temperature, it was observed that 870 °C is better for the deposition of single layer graphene on nickel substrate. The percentage of single layer on the substrate reduced significantly with decreasing the deposition temperature. The full width half maximum of the synthesized single layer graphene was 21 cm^?1 and Raman intensity ratio of 2D to G peak was almost nine. The film was transferred to insulating substrate and measured transmittance was 85 %. Raman spectroscopy, Raman mapping, SEM and UV–visible spectrometer measurement were performed for characterization.     

The formation and characterization of palladium nanowires in growing carbon nanotubes using microwave plasma-enhanced chemical vapor deposition

Multi-wall carbon nanotubes were synthesized on electroplated palladium nanoclusters using a microwave plasma-enhanced chemical vapor deposition system in a mixture of methane and hydrogen as precursors. During the synthesis, Pd was melted to fill up the growing multi-wall carbon nanotubes. A growth mechanism was proposed to describe the Pd filling phenomenon. The multi-wall carbon nanotubes could be burned in oxygen plasma and the filled Pd nanowires could thus be collected. The surface morphology of electroplated Pd clusters and the nanostructure of multi-wall carbon nanotubes with filled Pd nanowires were examined by scanning electron microscopy and transmission electron microscopy, respectively. Raman spectra were used to study the first- and second-order signals of multi-wall carbon nanotubes. Bamboo-shaped carbon nanotubes free of filled Pd were observed under a pure methane atmosphere.     

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.     

Investigation of influence of synthesis parameters on length and purity of the carbon nanotubes

In this article, a systematic study was conducted to understand the influences of various synthesis parameters, such as catalyst pretreatment time, growth time, growth temperature, reaction gas flow rate on length and quality of the carbon nanotubes grown by thermal chemical vapor deposition (TCVD). Carbon nanotube (CNT) grown on Fe deposited on silicon substrates were characterized by scanning electron microscope and Raman spectroscopy. It was found that all of the synthesis parameters investigated had effects on both length and quality of the carbon nanotube. After optimizing the various thermal chemical vapor deposition synthesis parameters, long carbon nanotube arrays of up to 150 microm in length were successfully synthesized and possess the potential application in multi-level interconnects.     

Preparation of high yield multi-walled carbon nanotubes by microwave plasma chemical vapor deposition at low temperature

Vertically-aligned carbon nanotubes(CNTs) with multi-walled structure were successfully grown on a Fe-deposited Si substrate at low temperature below 330°C by using the microwave plasma chemical vapor deposition of methane and carbon dioxide gas mixture. This is apparently different from the conventional reaction in gas mixtures of hydrogen and methane, hydrogen and acetylene, and hydrogen and benzene ... etc. High quality carbon nanotubes were grown at lower temperature with CO₂ and CH₄ gas mixture than those used by the previous. After deposition, the microstructure morphology of carbon nanotubes was observed with scanning electron microscope and high-resolution transmission electron microscope. The characteristics of carbon nanotubes were analyzed by laser Raman spectroscopy. The results showed the variation of the flow rate ratio of CH₄/CO₂ from 28.5 sccm/30 sccm to 30/30 sccm and the DC bias voltage from –150 V to –200 V, at 300 W microwave power, 1.3–2.0 kPa range of total gas pressure, and substrate temperatures between 300°C and 350°C. Vertically aligned carbon nanotubes with the diameter of about 15 nm and multi-walled structure were illustrated by SEM and HRTEM. However, the highest yield of carbon nanotubes of about 50% was obtained at low temperature below 330°C by MPCVD for the CH₄/CO₂ gas mixture with properly controlled parameters.     

用DBD-PECVD方法合成碳纳米管

在大气压、较低温度下合成碳纳米管(CNTs),对于大规模的工业生产具有重要的意义.本文介绍了一种介质阻挡放电等离子体增强化学气相沉积(DBD-PECVD)的方法,并利用该方法制备碳纳米管.实验是在约0.5个大气压、700℃下,通入氢气和甲烷的混合气体(CH4/H2为1∶10～1∶20),产生DBD等离子体;衬底为硅片;催化剂是用磁控溅射制备的Ni/Al薄膜,厚度分别为3nm和10nm.在扫描电镜下观察发现,碳纳米管的生长符合底端生长模式.在透射电镜下观察,碳纳米管没有竹节状结构.拉曼光谱分析表明,这种碳纳米管的结构缺陷比较多.     

Effective Synthesis of Vertically Aligned Boron Nitride Nanotubes via a Simple CCVD

A simple catalytic chemical vapor deposition technique based on the combined logic of previously synthesized vertically aligned carbon nanotubes and pattern growth of boron nitride nanotubes (BNNTs) along with a few simple modifications in the experimental setup is successfully used for the synthesis of vertically aligned BNNTs. Field emission scanning electron microscope images show the top and side view of the as grown pure BNNTs. High-resolution transmission electron microscope images confirm the tubular structure as well as the highly crystalline nature of the tubes. X-ray photon spectroscopy and Raman spectroscopy indicate h-BN as a main constituent of BNNTs synthesized in the present work.     

Catalyst-free growth of oriented single-walled carbon nanotubes on mica by ethanol chemical vapor deposition

In this letter, it is reported for the first time that single-walled carbon nanotubes (SWNTs) can grow on mica substrate without additional catalyst by chemical vapor deposition (CVD) using ethanol as carbon source. The single-wall structure was characterized by Raman spectra and AFM (Atomic Force Microscopy) measurements. The growth of carbon nanotubes on mica surface contributes to the small amount of iron oxide in bare mica. The uniform dispersion and nanosized Fe particles formed from the reduction of iron oxide favor for the growth of SWNTs. Horizontally aligned superlong SWNTs arrays can be successfully generated on the mica surface, which is proved to be guided by the gas flow and under “kite growth mechanism”. The mica is a machinable material which can be easily cut and made a narrow slit on, thus the nanotubes can traverse the slit which can be in millimeter scale and long suspended SWNTs can be generated. This will provide an opportunity to manipulate individual SWNT for various purposes.