Effect of catalysts and precursors in the synthesis of carbon nanotubes by catalytic chemical vapour deposition (original) (raw)
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A Study of Catalyst Preparation Methods for Synthesis of Carbon Nanotubes
Chemical Science Transactions, 2016
Carbon nanotubes (CNTs) have been rigorously studied during the past decade due to their extraordinary physical, chemical, mechanical, electrical and optical properties and nanosized catalysts plays an important role in the growth rate, purity and structural properties of the CNTs. In this paper we discuss various methods for the preparation of nanosized catalyst particles including electron bombardment, dc-sputtering, and magnetron sputtering, sol-gel and dip dry method in context to CNT synthesis. These methods are presented in a simplified manner so that the mechanism of formation of nanosized material can be illustrated. It is found that physical methods such as electron bombardment, dc-sputtering and magnetron sputtering prepare nanoparticles without any contamination; where as chemical methods such as sol-gel and dip dry methods are simplest and cheapest for the preparation of nanosized catalysts. Moreover, sol-gel method prepares monodisperse catalyst nanoparticles.
A Comparative Study of Carbon Nanotubes Synthesized from Co/Zn/Al and Fe/Ni/Al Catalyst
E-Journal of Chemistry, 2011
The catalyst systems Fe/Ni/Al and Co/Zn/Al were synthesized and used in the synthesis of carbon nanotubes. The carbon nanotubes produced were characterized by Field Emission Scanning Electron Microscope (FE-SEM), Energy Dispersive x-ray Spectroscopy (EDS), Raman spectroscopy, Thermogravimetric Analysis (TGA) and Transmission Electron Microscope (TEM). A comparison of the morphological profile of the carbon nanotubes produced from these catalysts indicates the catalyst system Fe/Ni/Al to have produced higher quality carbon nanotubes than the catalyst system Co/Zn/Al.
Polish Journal of Chemical Technology, 2014
Transition metal catalysts (mainly: iron, cobalt and nickel) on various supports are successfully used in a largescale production of carbon nanotubes (CNTs), but after the synthesis it is necessary to perform very aggressive purifi cation treatments that cause damages of CNTs and are not always effective. In this work a preparation of unsupported catalysts and their application to the multi-walled carbon nanotubes synthesis is presented. Iron, cobalt and bimetallic iron-cobalt catalysts were obtained by co-precipitation of iron and cobalt ions followed by solid state reactions. Although metal particles were not supported on the hard-to-reduce oxides, these catalysts showed nanometric dimensions. The catalysts were used for the growth of multi-walled carbon nanotubes by the chemical vapor deposition method. The syntheses were conducted under ethylene -argon atmosphere at 700°C. The obtained catalysts and carbon materials after the synthesis were characterized using transmission electron microscopy (TEM), X-ray diffraction method (XRD), Raman spectroscopy and thermogravimetric analysis (TG). The effect of the kind of catalyst on the properties of the obtained carbon material has been described.
Applied Catalysis A: General, 2007
The production of carbon nanotubes by the chemical catalytic vapour deposition, CCVD, process was examined over iron, cobalt, and a mixture of iron and cobalt supported on alumina catalysts synthesized by a one step sol-gel process. The catalysts were synthesized from several metal precursors, iron nitrate, cobalt and iron acetylacetonate, and cobalt acetate. Ethylene was used as the carbon source. The Co/Al 2 O 3 catalysts showed better activity and selectivity in carbon nanotubes synthesis than Fe/Al 2 O 3 and Fe-Co/Al 2 O 3 catalysts. The carbon deposit was found by TEM analysis to be rich in carbon nanotubes in the case of Co/Al 2 O 3 but to be very poor in the case of the Fe-Co/ Al 2 O 3 catalysts. The catalysts were characterized by TEM, XRD, and nitrogen adsorption. It was shown that iron and cobalt are in oxide form. Metal-support interactions and metal oxide particle size are influenced by the nature of the precursor and this nature is an important factor for the activity and selectivity of the catalysts. Moreover, a correlation has been found between the metal oxide particle sizes, the diameter of the carbon nanotubes, and the catalytic activity.
Journal of Nanoparticle Research, 2009
The effect of Fe and Ni catalysts on the synthesis of carbon nanotubes (CNTs) using atmospheric pressure chemical vapor deposition (APCVD) was investigated. Field emission scanning electron microscopy (FESEM) analysis suggests that the samples grow through a tip growth mechanism. High-resolution transmission electron microscopy (HRTEM) measurements show multiwalled carbon nanotubes (MWCNTs) with bamboo structure for Ni catalyst while iron filled straight tubes were obtained with the Fe catalyst. The X-ray diffraction (XRD) pattern indicates that nanotubes are graphitic in nature and there is no trace of carbide phases in both the cases. Low frequency Raman analysis of the bamboo-like and filled CNTs confirms the presence of radial breathing modes (RBM). The degree of graphitization of CNTs synthesized from Fe catalyst is higher than that from Ni catalyst as demonstrated by the high frequency Raman analysis. Simple models for the growth of bamboo-like and tubular catalyst filled nanotubes are proposed.
Carbon Nanotubes: Synthesis and Properties
Carbon nanotubes (CNTs) have been under scientific investigation more than fifteen years since their unique properties predestine them for numerous potential applications. The field of nanotechnology and nanoscience push their investigation forward to produce CNTs with suitable parameters for future applications. It is evident that new approaches of their synthesis need to be developed and optimized. In this chapter, brief history, types, structure and especially the different synthesis methods for CNTs preparation are reviewed. The attention is mainly aimed on various types of chemical vapor depositions as CVD methods for uniform vertically aligned CNT synthesis, liquid pyrolysis and solid state pyrolysis.
Synthesis of carbon nanotubes by CCVD of natural gas using hydrotreating catalysts
Egyptian Journal of …, 2013
Carbon nanotubes have been successfully synthesized using the catalytic chemical vapor deposition (CCVD) technique over typical refining hydrotreating catalysts (hydrodesulfurization and hydrodenitrogenation) containing Ni-Mo and Co-Mo supported on Al 2 O 3 catalysts at 700°C in a fixed bed horizontal reactor using natural gas as a carbon source. The catalysts and the as-grown CNTs were characterized by transmission electron microscopy, HRTEM, X-ray diffraction patterns, EDX and TGA-DTG. The obtained data clarified that the Ni-Mo catalyst gives higher yield, higher purity and selectivity for CNTs compared to Co-Mo catalyst. XRD, TEM and TGA reveal also that the Ni-Mo catalyst produces mostly CNTs with different diameters whereas the Co-Mo catalyst produces largely amorphous carbon.