Synthesis Of Multi-walled Carbon Nanotubes Research Articles

Synthesis of Multi-Walled Carbon Nanotubes by Spray-Pyrolysis Using a New Iron Organometallic Complex as Catalytic Agent

An organometallic catalytic agent ([(Hexyl)4N]3FeCl3Br3) has been synthesized through the reaction of tetrahexylammonium bromide ((Hexyl)4NBr) and iron chloride (FeCl3) aqueous solutions. Multi-walled carbon nanotubes (MWCNTs) were obtained by spray pyrolysis of toluene (carbon source) using the new organometallic compound as catalyst. The synthesized catalytic agent was characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), and thermal analysis (TA) techniques. Spectroscopic results indicated that the new iron organometallic compound has suitable characteristics to grow MWCNTs by spray pyrolysis. The MWCNTs were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The MWCNTs grow in a disordered way without orientation with diameters ranging from 20 to 50 nanometers. XRD patterns exhibit the 2-H graphite characteristics peaks of the MWCNTs.

Simplified Route to Multi-Walled Carbon Nanotube Synthesis by Aerosol Assisted Chemical Vapor Deposition

Uniform multi-walled carbon nanotubes (MWCNTs) were obtained decomposing toluene inside of fused silica tubing previously covered with Co oxide thin film. The two-step process, ruled successively in the same aerosol assisted chemical vapor deposition (AACVD) set up, constitutes a simplified route to the synthesis of MWCNTs. First, Co oxide thin film was deposited inside of fused silica tubing at 723 K, using a precursor solution of Co acetate in absolute methanol. After Co oxide deposition, the covered tubing was heated up to 1173 K under Ar flow, then a mist of toluene was injected inside the tubing, using also Ar as carrier gas, consequently MWCNTs were obtained in the internal wall of the tubing. The Co oxide film and the MWCNTs were analyzed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). Uniform and very long MWCNTs (several tens of microm) with diameters around 20 to 100 nm were observed, with the advantage that the content of Co particles inside the nanotube was very low.

Simple Synthesis of Multiwalled Carbon Nanotubes from Natural Resources

Bucket-and-spade chemistry: An environmentally friendly and highly efficient method for growing multiwalled carbon nanotubes (T) on a large scale has been developed which uses naturally abundant resources, namely garnet sand (G) as a catalyst precursor and support, and city gas as the carbon source. The as-produced carbon nanotubes have a well-crystallized wall structure and are easily separated from the garnet sand by sonication.

Synthesis of carbon nanotubes by pyrolysis of solid Ni(dmg) 2

We describe the high yield synthesis of multi-walled carbon nanotubes (MWCNTs) and the determination of the optimum production conditions. The method involves the catalytic pyrolysis of solid Ni(dmg) 2 under an Ar atmosphere. The obtained materials were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy and thermogravimetry analysis (TGA). The data revealed the formation of MWCNTs surrounded by a varying quantity of byproducts such as amorphous carbon and metallic particles, depending mainly on the reaction temperature. Pyrolysis of Ni(dmg) 2 at 900 °C results in the production of nanotube material with the highest degree of crystallinity.

Synthesis of multi-wall carbon nanotubes by copper vapor laser

Synthesis of multi-wall carbon nanotubes in a 1473 K furnace using a copper vapor laser (CVL) is reported. The operating parameters of this laser, i.e. a high fluence at the focal point and an extremely high frequency of 10 kHz, distinguished it from common laser sources in the synthesis of CNTs. Therefore, the unexpected experimental findings, the formation of MWNTs instead of the generally reported SWNTs, would be verified by these two notable parameters. Electron microscopy beside Raman spectroscopy illustrates the presence of multi-wall carbon nanotubes in the resulting product.

D-Fructose detection based on the direct heterogeneous electron transfer reaction of fructose dehydrogenase adsorbed onto multi-walled carbon nanotubes synthesized on platinum electrode

Multi-walled carbon nanotubes (MWCNTs) were synthesized on platinum plate electrodes by the chemical vapor deposition (CVD) method. From the results of X-ray photoelectron spectroscopy and voltammetric investigation, the iron nanoparticles used as a catalyst for the MWCNT synthesis were enclosed with MWCNTs. The MWCNTs synthesized on the Pt plate (MWCNTs/Pt) electrode were immediately immersed into solutions of d-fructose dehydrogenase (FDH) to immobilize the enzyme onto the MWCNTs/Pt electrode surfaces. After the FDH was immobilized onto the MWCNTs/Pt electrode, a well-defined catalytic oxidation current based on FDH was observed from ca. −0.15 V (versus Ag/AgCl/sat’d KCl), which was close to the redox potential of heme c as a prosthetic group of FDH. From an analysis of a plot of the catalytic current versus substrate, the calibration range for the fructose concentration was up to ca. 40 mmol dm −3, and the apparent Michaelis–Menten constant was evaluated to be 11 ± 1 mmol dm −3.

Reactivity of perovskite-type precursor in MWCNTs synthesis

Ni catalysts were tested in the synthesis of multi-wall carbon nanotubes (MWCNTs) by catalytic decomposition of methane at low temperature. The selectivity of MWCNTs formation was determined using transmission electron microscopy (TEM). The catalytic performance of the supported-Ni catalysts obtained by perovskite reduction was discussed based on the X-ray diffraction (XRD), TEM and scanning electronic microscopy (SEM) results. The characteristics of the nanotubes obtained by decomposition of methane were mainly dependent on the homogeneity of nickel particles and less on the reaction conditions.

Low temperature synthesis of multi-walled carbon nanotubes via a sonochemical/hydrothermal method

In this investigation, multi-walled carbon nanotubes (MWCNTs) have been prepared by a facile sonochemical/hydrothermal method. MWCNTs have been hydrothermally fabricated with using dichloromethane, cobalt chloride and metallic lithium as starting materials in 5 mol/lit NaOH aqueous solution. Ultrasonic pre-treatment of the solution mixture had an important step prior to the hydrothermal condition, which could generate a considerable amount of multi-walled carbon nanotubes for the subsequent hydrothermal growth. Finally, high pure MWCNTs with lengths of 2–5 μm and diameters of 60 ± 20 nm could be synthesized at as low temperature as 160 °C. As a matter of fact, the method of sonochemical/hydrothermal guarantees the production of multi-walled carbon nanotubes (MWCNTs) for different applications, especially reinforcement materials.

The Influences of H2Plasma Pretreatment on the Growth of Vertically Aligned Carbon Nanotubes by Microwave Plasma Chemical Vapor Deposition

The effects of H2flow rate during plasma pretreatment on synthesizing the multiwalled carbon nanotubes (MWCNTs) by using the microwave plasma chemical vapor deposition are investigated in this study. A H2and CH4gas mixture with a 9:1 ratio was used as a precursor for the synthesis of MWCNT on Ni-coated TaN/Si(100) substrates. The structure and composition of Ni catalyst nanoparticles were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The present findings showed that denser Ni catalyst nanoparticles and more vertically aligned MWCNTs could be effectively achieved at higher flow rates. From Raman results, we found that the intensity ratio of G and D bands (ID/IG) decreases with an increasing flow rate. In addition, TEM results suggest that H2plasma pretreatment can effectively reduce the amorphous carbon and carbonaceous particles. As a result, the pretreatment plays a crucial role in modifying the obtained MWCNTs structures.

Direct synthesis of hBN/MWCNT composite particles using spray pyrolysis

Abstract A spray-pyrolysis technique for the direct synthesis of multi-wall carbon nanotubes (MWCNTs) on a hexagonal boron nitride (hBN) matrix has been developed. Cobalt palladium (CoPd) nanoparticles, hBN nanoparticles, and ethanol were used as the catalyst, matrix, and carbon source, respectively. The materials were mixed by ultrasonication and then sprayed into a vertical tubular reactor at 900 °C under an argon flow of 2 L/min. As the aerosol passed through the reactor, the following processes occurred sequentially: solvent evaporation; formation of spherical particles composed of hBN and CoPd nanoparticles; catalytic decomposition of ethanol; and CNT growth on the surface of the CoPd nanoparticles. As a result, spherical-hairy particles were obtained, and both the hBN hexagonal phase and primary particle diameter were maintained during the reaction pathway because of the short residence time (1 s). The results showed that the spray-dried particle size and population of MWCNTs depended on the residence time within the heating zone and on the initial CoPd concentration. The novel synthesis technique described in this paper can be broadly applied to the production of various types of functional inorganic material/CNT composite particles.

Nature of the Catalyst Particles in CCVD Synthesis of Multiwalled Carbon Nanotubes Revealed by the Cooling Step Study

The true chemical nature and physical state of the catalyst particles in Catalytic Chemical Vapor Deposition (CCVD) synthesis of carbon nanotubes are the subject of intense discussions, as it is one of the keys to understand their growth mechanisms. The CCVD method considered in this article involves pyrolysis of mixed liquid aerosols and leads to the synthesis of large carpets of multiwalled nanotubes (MWNTs) partially filled with iron-based materials. The experimental approach consists in studying the influence of the cooling procedure applied at the end of the synthesis. Both slow standard cooling or quenching were performed, and the structure and chemical state of the iron-based particles were compared through complementary local and global investigations involving X-ray diffraction, electron microscopy, electron diffraction, as well as electron energy loss spectroscopy. We clearly demonstrate that iron-based catalyst particles are carbon-rich and oxygen-free in quenched samples, and that they oxidize during the slow cooling step. It is inferred that they are very probably molten supersaturated carbon-metal particles during the NT growth.

Controlling the dimensions, reactivity and crystallinity of multiwalled carbon nanotubes using low ethanol concentrations

We study the role of ethanol in the thermolytic synthesis of multiwalled carbon nanotubes. We show that low concentrations of ethanol control the length and diameter, as well as the crystalline quality of the produced nanotubes. We statistically evaluated the dimensions of the tubes as the concentration of ethanol is increased. The quality of the samples results in more crystalline products when low concentrations of ethanol (∼1–2%) are used in the experiments. In addition, the introduction of ethanol during the synthesis seems to incorporate coordination groups on the surface of nanotubes that cause an enhanced reactivity and a better solubility.

One-step solid-state thermolysis of a metal–organic framework: a simple and facile route to large-scale of multiwalled carbon nanotubes

We report a simple and facile solid-state approach to large-scale synthesis of multiwalled carbon nanotubes (MCNTs), for the first time, by one-step direct thermolysis of a metal-organic framework [Ni(3)(btc)(2).12H(2)O] (btc = benzene-1,3,5-tricarboxylato) in a one-end closed conventional horizontal tube furnace under relatively low temperature without using any additional carrier gas or catalyst.

Use of Saccharides as Solid-state Precursors for the Synthesis of Carbon Nanotubes

ABSTRACTSaccharides, ranging from simple table sugar (sucrose) to lactulose were successfully used as solid-state precursors for the synthesis of multi-walled carbon nanotubes (MWCNT). Dehydrated saccharide residues mixed with catalyst powders were subjected to pyrolysis at high temperatures (up to 1300°C) under flowing Argon atmosphere. Pyrolysis products were investigated using TEM, SEM, Raman spectroscopy and EDS. Images taken using the S/TEM and bright field mode of TEM showed the presence of helical multi-walled carbon nanotube (H-MWCNT) and regular MWCNT formation. More than two or three catalyst particles were observed to be present inside the hollow core of some of the nanotubes synthesized, suggesting a high level of capillary activity inside the tubes during synthesis.

Synthesis and Optimization of MWCNTs on Co-Ni/MgO by Thermal CVD

Multiwalled carbon nanotubes (MWCNTs) were prepared by the thermal chemical vapor deposition (CVD) technique. Monometallic and bimetallic Co and Ni combinations were used as a catalyst on MgO support. The mixer ofH2/C2H2was used as a carbon source. The prepared CNTs were found to possess different shapes, morphologies, and sizes. Maximum yield was found for 50% Co (MgO: 50% and Ni: 0%) catalyst at 600°C. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) techniques were used for structural analysis. Raman spectra were taken to investigate the quality and crystalline perfection of the prepared CNTs. The ratio of D- and G-bands (ID/IG) was measured from these spectra.

Direct conversion of highly aromatic phthalonitrile thermosetting resins into carbon nanotube containing solids

A method for the in situ synthesis of multi-walled carbon nanotubes in a bulk solid composition from the pyrolysis of a mixture formulated from Co2(CO)8 and various high temperature phthalonitrile resins is presented. Carbon nanotube containing compositions in various forms (solid, fiber, and film) can be readily fabricated by this method utilizing slight modifications to the standard resin processing techniques. The formation of carbon nanotubes occurs during the carbonization process at ambient pressure. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy studies show the presence of a copious amount of multi-walled carbon nanotubes in the carbonaceous composition.

Synthesis of multi-wall carbon nanotubes by simple pyrolysis

A new pyrolysis technique has been developed for the synthesis of multi-walled carbon nanotubes (MWCNTs). In this simple method diethyl ether and nickelocene is pyrolysized in a reaction quartz tube without using carrier gas. The samples are prepared at pyrolysis temperatures of 650 and 950 ∘C and the effect of temperature on the tube morphology investigated. Purification has been done following the standard oxidation and acid bath treatment. The as-synthesized and purified nanotubes have been characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA) and micro-Raman spectroscopy. The technique has great advantages such as low cost and easy operation for the production of CNTs.

Hydrothermal Synthesis of Multi-Walled Carbon Nanotube Added Lithium Iron Phosphate Cathode Materials for Lithium Polymer Batteries

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Synthesis of MWNTs using Fe–Mo bimetallic catalyst by CVD method for field emission application

Multiwalled carbon nanotubes (MWNTs) were synthesized by chemical vapor deposition technique using MgO supported bimetallic Fe–Mo catalyst. The role of Mo on the quality of as-synthesized CNTs and their application in field emission has been investigated. The field emission properties of the device fabricated from the CNTs synthesized with Fe–Mo catalyst was found to be better than the similar device prepared with CNTs synthesized with Fe catalyst alone.

Growth of Carbon Nanotubes on Nanoporous Titania Templates

This work reports the synthesis of multiwalled carbon nanotubes (MWCNTs) on nanoporous titanium dioxide (TiO2) templates. TiO2 nanotubular templates for MWCNTs are produced by anodization of titanium followed by pulsed electrodeposition (PED) of cobalt inside the TiO2 nanotubes. Cobalt acts as a catalyst for the growth of MWCNTs using chemical vapor deposition (CVD) technique. The cobalt catalyst initiates the growth of well graphitized MWCNTs inside the titania pores as well as beyond the titania pores. These materials have been characterized by SEM, EDS, GXRD, XPS, TEM, and ED techniques. The MWCNTs were about 10 mu in length and 80-120 nm in diameter.