Preparation and characterization of multi-walled carbon nanotubes grown on transition metal catalysts (original) (raw)
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Physical Chemistry Chemical Physics, 2000
Catalytic synthesis and transmission electron microscopy (TEM) of multi-wall carbon nanotubes are presented. Silica, zeolite and alumina supported cobalt catalysts were prepared by di †erent methods (impregnation and ion-adsorption precipitation) and were used to produce nanotubes. The synthesis was carried out in a Ðxed bed Ñow reactor and the process was optimized in order to produce carbon nanotubes on a gram scale. The inÑuence of various parameters such as the method of catalyst preparation, the nature of the support, cobalt concentration and reaction conditions on the formation of nanotubes was investigated. The carbon deposits were measured and the quality of nanotubes was determined by low and high resolution TEM. Multi-wall straight and coiled nanotubes were found to be fairly regular with an average inner (outer) diameter of 4È7 nm (8È23 nm) and with lengths up to 0.1 mm.
Diamond and Related Materials, 2008
The crucial role of precursor gas (PG) and of catalyst support (CS) in the growth of multi-walled C nanotubes (MWCNTs) by iron-catalysed chemical vapour deposition (CVD) is evidenced. This is accomplished by comparing structural and morphological properties of MWCNTs synthesised by the use of different PGs (ethane and isobutane) and CSs (silica and alumina). The results of analyses, carried out on catalysts and C deposits by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS), thermo-gravimetry (TG) and X-ray diffraction (XRD), demonstrate that Al 2 O 3 -supported catalysts are more efficient than SiO 2 -supported ones in decomposing hydrocarbons. The use of i-C 4 H 10 as PG allows reducing Fe-encapsulation and improving yield (Y C ) and selectivity, so as the largescale production (Y C N 900 wt.%) of high-quality nanotubes can be operated even at moderate reaction temperature (600°C) after proper calibration of Fe-load (29 wt.%) and catalyst reduction temperature (500°C).
Purification of Multi-Walled Carbon Nanotubes Grown by Thermal CVD on Fe-Based Catalyst
Advances in Science and Technology, 2006
Aiming at the purpose of using carbon nanotubes as secondary phase in composite materials, removal of metal catalyst, catalyst support and amorphous carbon is crucial to make the most of the required properties. A purification method was developed to remove the metal catalyst from multi-walled nanotubes grown by thermal CVD. A nanosized Fe-based catalyst, prepared by coprecipitation of iron and aluminum ions, followed by solid state reaction, was used to catalyze the growth. Carbon nanotubes were subjected to acid purification and a comparison between nitric acid and a mixture of nitric and hydrochloric acid for the removal of Fe and Fe oxides is provided. Morphological and spectroscopic analyses of the materials were performed, both before and after the purification processes.
Production of carbon nanotubes on different metal supported catalysts
Reaction Kinetics and Catalysis Letters, 2001
Multiwall carbon nanotubes have been prepared by catalytic chemical vapor deposition (CCVD) method in high yield using various metals supported on different supports. Measurements by transmission electron microscopy (TEM) revealed the presence of high quality nanotubes on each catalyst, however, comparing the different catalysts in nanotube production it can be stated that beyond metals, the support also affects both the quality and the quantity of nanotubes.
An Efficient Catalyst for the Large Scale Production of Multi-Walled Carbon Nanotubes
Industrial & Engineering Chemistry Research, 2011
The main objective of this work is to design an efficient catalyst for the synthesis of multiwalled carbon nanotubes (MWNTs) in our scalable, high quality with gram amount synthesis. The catalysts with composition of Fe, Mo, and MgO in the molar ratios 1:0.5:13, 1:1:13, and 1:1:50 were prepared by combustion method. The high acetylene conversion and carbon yield of chemical vapor deposition (CVD) reaction suggest the formation of MWNTs by 1:1:50 molar ratio catalysts under pyrolysis of the pure C 2 H 2 gas with the flow rate about 60 mL/min at 800 C for 30 min. The catalysts and the resulting CNT samples were analyzed by XRD, TGA, FT-Raman, SEM, and TEM to establish a relation between catalyst design and MWNT yield. Raman results indicate that CNTs are in multiwalled structure, since no single-walled characteristic features appear in the 200À400 cm À1 region. We give evidence that increased carbon conversion, carbon yields and % purity of more than 65%, 1000%, and 99%, respectively, with respect to our catalysts are directly related to ratio between FeÀMo and MgO. One g of acetylene containing 0.9231 g of carbon would enter the reaction chamber, which is responsible for the 1.96, 1.9842, and 2.2356 g of the carbon deposition per 200 mg of catalyst A, B, and C respectively.
Fe-Co bimetallic catalysts supported on CaCO3 were prepared by a wet impregnation, a deposition-precipitation and a reverse micelle method. The sizes of the Fe and Co particles were not affected by the Fe and Co sources (nitrate, acetate) when the wet impregnation and deposition-precipitation methods were used. 'Clean' multi-walled carbon nanotubes (MWCNTs) were obtained from all three Fe-Co synthesis procedures under optimal reaction conditions. The CNTs produced gave yields ranging from 623 % to 1215 % in 1 h under the optimal conditions, with similar outer diameters (o.d.) of 20-30nm and inner diameters (i.d.) ~10 nm. The Fe / Co catalyst formed in the wet impregnation method revealed that the yield, diameter and purity of the CNTs were influenced by the C2H2 / N2 ratio, time and temperature. All the methods gave high-quality CNTs after short reaction times but the quality deteriorated as the synthesis time was increased from 5 to 360 min. Indeed, the most influential par...
A novel method for fabrication Fe catalyst using for synthesis of carbon nanotubes
Carbon nanotubes (CNTs) have been grown by decomposition of propane over a nanocamposite catalyst by chemical vapour deposition (CVD). The catalyst was prepared from an aluminum/iron oxide/graphite mixture milled in a high-energy ball-milling equipment. Scanning and transmission electron microscopies, Raman spectroscopy and X-ray diffraction measurements have been carried out in order to investigate the catalyst and synthesized CNTs. The results show that iron nanoparticles are produced in an alumina and ball-milled graphite matrix. This produced nanocomposite is used as a catalyst to synthesize CNTs via CVD successfully. The yield of CNTs formation was greatly influenced by the milling time and deposition temperature.
Nanotechnologies in Russia, 2010
This paper is devoted to a survey of results obtained while investigating the growth processes of carbon nanotubes (CNTs) on different substrates using iron as the catalyst and CO as the carbon source. Three different approaches to the substrate coating by the catalyst are discussed: sputtering metallization and particle synthesis using the hot wire generator and its ex situ and in situ deposition. The possibility of growing ultralong one and double walled thick nanotubes and CNT flow alignment are demonstrated. The influence of the diameter of single wall CNTs on their deformation on the substrate surface is studied. The possibility of controlling the number of CNT walls depending on the experimental conditions is demonstrated. The role of etching agents during CNT synthesis is discussed.
A novel method for fabrication of Fe catalyst used for the synthesis of carbon nanotubes
Bulletin of Materials Science, 2014
Carbon nanotubes (CNTs) have been grown by decomposition of propane over a nanocamposite catalyst by chemical vapour deposition (CVD). The catalyst was prepared from an aluminum/iron oxide/graphite mixture milled in a high-energy ball-milling equipment. Scanning and transmission electron microscopies, Raman spectroscopy and X-ray diffraction measurements have been carried out in order to investigate the catalyst and synthesized CNTs. The results show that iron nanoparticles are produced in an alumina and ball-milled graphite matrix. This produced nanocomposite is used as a catalyst to synthesize CNTs via CVD successfully. The yield of CNTs formation was greatly influenced by the milling time and deposition temperature.