Influence of oxygen on the growth of carbon nanotubes by the SiC surface decomposition method

The influence of oxygen on the development of carbon nanotubes (CNTs) during the annealing process of the surface decomposition method on SiC(000−1) surfaces was investigated. In the case of annealing a SiC substrate under ultra-high vacuum conditions, carbon nanofibers (CNFs) form between the CNT layer and the substrate. However, CNTs form without CNFs by annealing the substrate in an oxygen atmosphere. The mean length of CNTs is longer than those formed without an oxygen atmosphere. From cross-sectional transmission electron microscopy images, it was found that oxygen plays an important role in CNT growth by the surface composition method.     

Boron doped carbon nanotubes via ceramic catalysts

A facile metal catalyst free route to synthesize boron doped (0.6%–1.0%) carbon nanotubes via ceramic nanowires in which the formation of the nanowires (probably serving as templates), the carbon nanotubes and their doping all occur unanimously in the reaction, is presented.

     

Environmental transmission electron microscopy observations of the growth of carbon nanotubes under nanotube-nanotube and nanotube-substrate interactions

The growth process of carbon nanotubes (CNTs) under CNT-CNT and CNT-substrate interactions has been observed directly by environmental transmission electron microscopy. Even a free standing CNT occasionally swings during the growth until it touches the substrate. In addition, we show that the growth direction of CNTs changes due to the interaction between CNTs.     

Fabrication of well-aligned CdS nanotubes by CVD-template method

Well-aligned CdS nanotubes have been synthesized within the nanochannels of the porous anodic alumina (PAA) membranes by pyrolyzing cadmium bis(diethyldithiocarbamate) [Cd(S₂CNEt₂)₂] at 400 °C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the CdS nanotubes are highly ordered with uniform diameter in range of 80-150 nm and the length up to tens of microns. X-ray diffraction (XRD), Raman spectrum, energy-dispersive spectroscopy (EDS) and selected-area electron diffraction (SAED) demonstrate that the nanotubes are composed of pure hexagonal phase polycrystalline CdS. The synthetic route can, in principle, be extended to fabricate other nanotubes of a wide range of semiconductors.     

Growth of single-walled carbon nanotubes on silicon nanowires

Single-walled carbon nanotubes (SWNTs) have been grown on silicon nanowires (SiNWs) by ethanol chemical vapor deposition (CVD) with Co catalysts. We have found that a surface SiO_x layer of SiNWs is necessary for the formation of active Co catalysts. In fact, the yield of the SWNT/SiNW heterojunctions gradually decreases as the thickness of the surface SiO_x layer decreases. Since thin SiNWs are transparent to an electron beam, the Co nanoparticles on SiNWs can be easily observed as well as SWNTs by TEM. Therefore, the relationship between the diameters of each SWNT and its catalyst nanoparticle has been investigated. The diameters of SWNTs are equal to or slightly smaller than those of the catalyst nanoparticles.     

High yield incorporation and washing properties of halides incorporated into single walled carbon nanotubes

We describe here the high yield filling (i.e. >50%) of single walled nanotubes (SWNTs) with a variety of halides, achieved according to various modified filling procedures. Both bundles and discrete SWNTs can be filled continuously up to lengths of several hundred nm, often with filling yields approaching 60–70% or better. In addition some high yield filled SWNTs were subjected to long-term washing in either boiling or room temperature. aqueous media, which does not remove the filling from the tubules, but enables effective removal of water-soluble extraneous materials . Received: 10 May 2002 / Accepted: 25 October 2002 / Published online: 10 March 2003 RID="*" ID="*"Corresponding author. Fax: +44-1865/272-690, E-mail: jeremy.sloan@chem.ox.ac.uk     

Effect of nickel,iron and cobalt on growth of aligned carbon nanotubes

The effect of pure nickel, iron and cobalt on growth of aligned carbon nanotubes was systematically studied by plasma-enhanced hot-filament chemical vapor deposition. It is found that the catalyst has a strong effect on the nanotube diameter, growth rate, wall thickness, morphology and microstructure. Ni yields the highest growth rate, largest diameter and thickest wall, whereas Co results in the lowest growth rate, smallest diameter and thinnest wall. The carbon nanotubes catalyzed by Ni have the best alignment and the smoothest and cleanest wall surface, whereas those from Co are covered with amorphous carbon and nanoparticles on the outer surface. The carbon nanotubes produced from Ni catalyst also exhibit a reasonably good graphitization. Therefore, Ni is considered as the most suitable catalyst for growth of aligned carbon nanotubes. Received: 30 November 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002     

Lateral growth of aligned mutilwalled carbon nanotubes under electric field

In this work we report laterally aligned multi-walled carbon nanotube (MWNT) by an electric field during growth. The MWNTs were selectively grown between lateral sides of the catalytic metals on predefined electrodes by chemical-vapor deposition. The electric field distribution for various geometries was simulated using Maxwell 2D simulation in order to realize better alignment of laterally grown carbon nanotubes (CNTs). The experimental results show that the electric field direction at the vicinity of catalyst and nanotubes-substrate interactions are principal factor in aligning CNTs laterally.     

Synthesis of carbon nanotubes by CVD: Effect of acetylene pressure on nanotubes characteristics

The effect of acetylene partial pressure on the structural and morphological properties of multi-walled carbon nanotubes (MWCNTs) synthesized by CVD on iron nanoparticles dispersed in a SiO₂ matrix as catalyst was investigated. The general growing conditions were: 110 cm³/min flow rate, 690 °C synthesis temperature, 180 Torr over pressure and two gas compositions: 2.5% and 10% C₂H₂/N₂. The catalyst and nanotubes were characterized by HR-TEM, SEM and DRX. TGA and DTA were also carried out to study degradation stages of synthesized CNTs. MWCNTs synthesized with low acetylene concentration are more regular and with a lower amount of amorphous carbon than those synthesized with a high concentration. During the synthesis of CNTs, amorphous carbon nanoparticles nucleate on the external wall of the nanotubes. At high acetylene concentration carbon nanoparticles grow, covering all CNTs’ surface, forming a compact coating. The combination of CNTs with this coating of amorphous carbon nanoparticles lead to a material with high decomposition temperature.     

Nanoporous carbon spheres and their application in dispersing silver nanoparticles

Monodisperse nanoporous carbon spheres (NCS) were synthesized in large quantities via a facile hydrothermal synthesis. It is found that the NCS have rough surfaces with a large quantity of uniformly distributed protruding and concaving zones. Large quantities of nanopores of about 0.3 nm in diameter are distributed uniformly on the whole sphere surfaces. The effects of reaction parameters on the surface roughness, sphere diameter and pore size of NCS were investigated. Taking the NCS as substrates, silver nanoparticles (NPs) were deposited onto their surfaces using a one-step ultrasonic electrodeposition procedure. The deposited silver NP has a uniform distribution, a high particle density and a narrow size range of 12-16 nm in diameter. This study demonstrates an efficient approach to fabricate noble-metal/carbon nanocomposites.     

Growth and mechanism of titania nanowires

Anatase and rutile-phase titania nanowires have been prepared via an efficient molten salt-assisted and novel pyrolysis route, respectively. The growth of anatase nanowires is parallel to [010] direction. The anatase titanium oxide nanowires are obtained by exchange reaction between Na₂TiO₃ and HCl, whereas the formation of rutile titania nanowires is conventional vapor-liquid-solid growth mechanism.     

Adsorption of nicotine and tar from the mainstream smoke of cigarettes by oxidized carbon nanotubes

The adsorption of nicotine and tar from the mainstream smoke (MS) by the filter tips filled respectively with oxidized carbon nanotubes (O-CNTs), activated carbon and zeolite (NaY) has been investigated. O-CNTs show exceptional removal efficiency and their adsorption mechanism is investigated. Capillary condensation of some ingredients from MS in the inner hole of O-CNTs is observed and may be the primary reason for their superior removal efficiency. The effect of O-CNTs mass on the removal efficiencies is also studied and the results show that about 20-30 mg O-CNTs per cigarette can effectively remove most of nicotine and tar.     

Manipulation and soldering of carbon nanotubes using atomic force microscope

Manipulation of carbon nanotubes (CNTs) by an atomic force microscope (AFM) and soldering of CNTs using Fe oxide nanoparticles are described. We succeeded to separate a CNT bundle into two CNTs or CNT bundles, to move the separated CNT to a desirable position, and to bind it to another bundle. For the accurate manipulation, load of the AFM cantilever and frequency of the scan were carefully selected. We soldered two CNTs using an Fe oxide nanoparticle prepared from a ferritin molecule. The adhesion forces between the soldered CNTs were examined by an AFM and it was found that the CNTs were bound, though the binding force was not strong.     

Loss of adhesion strength of PVD Cu films on carbon substrates after heat treatment and correlated effects on the thermal interface properties

The study of coating-substrate systems consisting of a thin copper film on a flat carbon substrate is of great interest in order to get information on the interfacial behaviour of such systems. This work is focused on the mechanical adhesion strength and the correlated interfacial thermal contact resistance which are influenced by heat treatment. Using plasma-assisted pre-treatment of the carbon substrate prior to the deposition of copper coatings via physical vapor deposition (PVD), the adhesion strength between copper coatings and substrate has increased significantly, while the thermal contact resistance decreased in the as deposited state. After heat treatment at 800 °C for 1 h, considerably decreased adhesion strengths have been observed, accompanied by increased values of the thermal contact resistance.     

GISAXS study of carbon nanotubes grown by CVD

We report a quantitative Grazing Incidence Small Angle X‐ray Scattering (GISAXS) study of a dense film of mutually oriented carbon nanotubes (CNTs) grown by a catalytically‐activated DC HF CCVD process after dispersion of metallic catalytic (Co) islands on SiO₂/Si(100) substrates. The GISAXS pattern analysis is expanded to non‐correlated surface science systems and is based on CNTs density, characteristic lengths, atomic Co dispersion throughout the CNTs and roughnesses of uncorrelated particles. The results are closely compared to SEM and TEM observations. The GISAXS patterns, even dominated by envelope features of disordered objects, provide significant complementary quantitative data about CNTs films. The results underline that cobalt continuously fills the nanotube in the course of the growth and that the CNTs experience a large tendency toward mutual alignment. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Highly selective growth of vertically aligned double‐walled carbon nanotubes by a controlled heating method and their electric double‐layer capacitor properties

Vertically aligned double‐walled carbon nanotubes (DWCNTs) with the highest selectivity of 90% were synthesized by a controlled heating method and their electric double‐layer capacitor characteristics were evaluated. DWCNT arrays had a specific capacitance of 83 F/g, which is one of the highest values among CNT arrays in a nonaqueous solution and is almost equivalent to that for single‐walled CNT (SWCNT) arrays reported previously. At the same specific capacitance, DWCNTs with superior structural properties are more promising for practical capacitors than SWCNTs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Large-scale synthesis of rutile SnO2 nanorods

A high yield of tin oxide (SnO₂) nanorods was obtained via annealing a nanoscale precursor in the molten salt flux and surfactant. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction and infrared spectroscopy showed that the nanorods are composed of SnO₂ with rutile structure. The surfactant and temperature have a profound influence on the production of SnO₂ nanorods.     

Scalable synthesis of Sb(III)Sb(V)O4 nanorods from Sb2O5 powder via solvothermal processing

Scalable Sb(III)Sb(V)O₄ nanorods from Sb₂O₅ powder were prepared using solvothermal route. XRD and HRTEM demonstrate that the nanorods are single-crystal orthorhombic-Sb₂O₄ phase with several micrometers long and 200-300 nm diameter size. XPS result further shows that the antimony cations in the nanorods are composed of three valence and five valence antimony ions. The emission of the nanorods appears around 450 nm wavelength. The formation mechanism of the Sb(III)Sb(V)O₄ nanorods was discussed in detail.     

Bundles and foils of WS2 nanotubes

In this paper, the synthesis of multigram portions of WS₂ nanotubes and large foils consisting of aligned nanotubes is described. For this purpose, a fluidized bed reactor, in which WO₃ powder is fed from the top and the reaction gases are blown from below maintaining the powder aloft, is described. The reaction mechanism is briefly discussed. Received: 20 August 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002     

Imaging as-grown single-walled carbon nanotubes originated from isolated catalytic nanoparticles

Discrete catalytic nanoparticles with diameters in the range of 1–3 nm are obtained by placing controllable numbers of metal atoms into the cores of apoferritin. With nanoparticles placed on transmission electron microscope (TEM) grids coated with ultra-thin alumina membranes, isolated single-walled carbon nanotubes are grown by chemical vapor deposition and directly examined by TEM. The characterizations, carried out at single-tube and single-particle level, obtain clear evidence that the diameters of the nanotubes are determined by the diameters of catalytic nanoparticles. For the first time, both ends of an as-grown single-walled nanotube are imaged by TEM, leading to a microscopic picture of the nanotube-growth mechanism. Received: 19 September 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002