On the role of catalyst, catalyst support and their interaction in synthesis of carbon nanotubes by CCVD (original) (raw)
Related papers
The role of zeotype catalyst support in the synthesis of carbon nanotubes by CCVD
Studies in Surface Science and Catalysis, 2002
The effect of zeotype support on the selectivity of carbon nanotube formation in the catalytic decomposition of acetylene was investigated. Catalyst supports with various pore diameters were tested. Formation and the quality of carbon deposit were followed by transmission electron microscopy (TEM) and the state of supported catalyst particles was investigated by in situ X-ray photoelectron spectroscopy (XPS) measurements. It was found that only catalyst particles deposited on the external surfaces of poious support could efficiently take part in the catalytic carbon nanotube formation.
The catalytic growth of carbon nanotubes was investigated from the point of view of reaction mechanism. A great variety of catalyst supports (silica gel, zeotype materials, alumina, etc.) with different pore diameter was tested in acetylene decomposition at 1000 K. Quality and existence of carbon deposit was followed by transmission electron microscopy and the state of catalyst was investigated by in situ X-ray photoelectron spectroscopy measurements. It was proved that only catalyst particles deposited on the external surfaces of porous support could take part in the catalytic carbon nanotube formation.
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.
Effect of catalyst preparation on the yield of carbon nanotube growth
Physica B: Condensed Matter, 2009
Multi-wall carbon nanotubes (MWCNTs) were synthesized by catalytic chemical vapor deposition (CVD) on catalytic iron nanoparticles dispersed in a silica matrix, prepared by sol gel method. In this contribution, variation of gelation condition on catalyst structure and its influence on the yield of carbon nanotubes growth was studied. The precursor utilized were tetraethyl-orthosilicate and iron nitrate. The sols were dried at two different temperatures in air (25 or 80 1C) and then treated at 450 1C for 10 h. The xerogels were introduced into the chamber and reduced in a hydrogen/nitrogen (10%v/v) atmosphere at 600 1C. MWCNTs were formed by deposition of carbon atoms from decomposition of acetylene at 700 1C. The system gelled at RT shows a yield of 100% respect to initial catalyst mass whereas the yield of that gelled at 80 1C was lower than 10%. Different crystalline phases are observed for both catalysts in each step of the process. Moreover, TPR analysis shows that iron oxide can be efficiently reduced to metallic iron only in the system gelled at room temperature. Carbon nanotubes display a diameter of about 25-40 nm and several micron lengths. The growth mechanism of MWCNTs is base growth mode for both catalysts.
2006
Since the pioneering report of discovery of carbon nanotubes (CNTs) in 1991 by Iijima, scientists and researchers worldwide have carried out in depth investigations in this new family of carbon because of its myriad properties and potential applications. The synthesis of novel nanoscale material is the main target in current material science. This study investigates the effect of different types of cabon source and and catalyst on the type of CNTs formed via catalytic chemical vapour deposition (CCVD) method. Three types of carbon source i.e. acetylene, methane and ethanol were used for the synthesis of CNTs. The catalysts used in the synthesis of CNTs are monometallic, bimetallic and trimetallic derived from Fe, Co and Ni salts using wet impregnation method. The catalysts were characterized by scanning electron microscope (SEM) and energy-dispersive X-ray analysis (EDX). The analysis confirmed the presence of Fe, Co and Ni. The as-synthesized CNTs were characterized using SEM/field...
Synthesis of single- and multi-wall carbon nanotubes over supported catalysts
Applied Physics A-materials Science & Processing, 1998
Catalytic synthesis and some characterization of multi-and single-wall carbon nanotubes are presented. Supported transition-metal catalysts were prepared by different methods and were tested in the production of nanotubes by decomposition of hydrocarbons at 700 • C, using a fixed-bed flow reactor.
Synthesis of carbon nanotubes with and without catalyst particles
Nanoscale Research Letters, 2011
The initial development of carbon nanotube synthesis revolved heavily around the use of 3d valence transition metals such as Fe, Ni, and Co. More recently, noble metals (e.g. Au) and poor metals (e.g. In, Pb) have been shown to also yield carbon nanotubes. In addition, various ceramics and semiconductors can serve as catalytic particles suitable for tube formation and in some cases hybrid metal/metal oxide systems are possible. All-carbon systems for carbon nanotube growth without any catalytic particles have also been demonstrated. These different growth systems are briefly examined in this article and serve to highlight the breadth of avenues available for carbon nanotube synthesis. Figure 7 Schematic representation of the carbothermal reduction of silica to silicon carbide and carbon nanostructure formation: (a) SiO 2 is reduced to SiC via a carbothermal reaction, (b) SiC nanoparticles coalesce, (c) carbon caps form on the surface of the SiC particles through precipitation and/or SiC decomposition. Reproduced with permission from Bachmatiuk et al. [37].
Growth of Carbon Nanotubes from Supported Metal Catalysts
Microscopy and Microanalysis, 2005
The growth of carbon nanotubes (CNTs) from supported metal catalysts is under investigation using the chemical vapour deposition (CVD) method with CH 4 as the carbon feedstock. Studies include the effects of the structure of the support media, metal catalyst content and other experimental parameters on the CNTs produced. The effects of the surface structure on the catalyst particles and the CNTs produced are being investigated using various alumina-based supported iron catalysts. Supported catalysts have been prepared from ferric sulphate and either aluminium nitrate or deltaalumina nanoparticles in order to produce different substrate morphologies. Preliminary TEM studies indicate that under the same experimental conditions Fe supported on alumina nanoparticles produces mostly bundles of DWCNTs, whereas Fe supported on alumina derived from aluminium nitrate produces predominantly SWNCT bundles with some MWCNTs. The effects of catalyst content on the CNT production is also being investigated with Fe content varying between 5% and 30%. Preliminary TEM results show the presence of bundles of SWCNTs for all the Fe contents except 5% Fe; no CNTs have been observed in this sample.
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.