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Carbon nanotubes and nanospheres: synthesis by nebulised spray pyrolysis and use in catalysis

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dc.contributor.advisor Prof. N.J. Coville Dr. R.W.M. Krause en
dc.contributor.author Cele, Leskey Mduduzi
dc.date.accessioned 2009-05-13T08:47:51Z
dc.date.available 2009-05-13T08:47:51Z
dc.date.issued 2009-05-13T08:47:51Z
dc.date.submitted 2007-11
dc.identifier.uri http://hdl.handle.net/10210/2536
dc.description Ph.D. en
dc.description.abstract This work presents a detailed study of the synthesis of carbon nanotubes and nanospheres by nebulised spray pyrolysis. This method has been used by other workers mainly for preparation of sub-micron particles and the deposition of thin films on various substrates. The effect of various synthesis parameters including the temperature, choice of the carbon source and the metal precursor as well as the carrier gas flow rate on the selectivity of the reaction and the properties of the carbon nanotubes produced was investigated. A major part of this work was devoted to a study of the effects of the addition of small quantities of oxygencontaining compounds (alcohols, esters and aldehydes) to the reaction mixture. The products were analysed using various methods including TEM, SEM, Laser- Raman spectroscopy and HRTEM. Furthermore, the possible use of carbon nanotubes and carbon nanospheres as supports for palladium in the hydrogenation of ethylene was investigated. Nebulised spray pyrolysis proved to be a suitable technique for the synthesis of well graphitized carbon nanotubes and carbon nanospheres with uniform diameters and it was demonstrated that good control of the carbon nanotube properties could be achieved by controlling the synthesis parameters. Better graphitization of the carbon nanotubes was observed at higher temperatures. Ferrocene, iron pentacarbonyl, nickelocene and cobaltocene were successfully used in carbon nanotube synthesis with the last two producing carbon nanotubes with diameters close to those on single-walled carbon nanotubes. Toluene (with and without acetylene as a supplementary carbon source), benzene, mesitylene, xylene and nhexane were successfully used to produce carbon nanotubes with a high degree of alignment while no success was achieved with ethanol. The poor yields obtained with ethanol appear to be a consequence of chemical changes in the ethanol induced by exposure to ultrasound irradiation. On the other hand, low concentrations of methyl acetate and ethyl acetate appear to enhance the production of carbon nanotubes. It was demonstrated that carbon nanotubes and nanospheres are suitable for use as supports for palladium in the hydrogenation of ethylene. Pd particles of uniform size were obtained and the conversion rates were slightly higher when the carbon nanotubes were pre-treated with a mixture of sulphuric acid and nitric acid. en
dc.language.iso en en
dc.subject Carbon en
dc.subject Nanotubes en
dc.subject Nanostructured materials en
dc.subject Pyrolysis en
dc.subject Organic compounds synthesis en
dc.subject Palladium catalysts en
dc.subject Hydrogenation en
dc.subject Ethylene en
dc.title Carbon nanotubes and nanospheres: synthesis by nebulised spray pyrolysis and use in catalysis en
dc.type Thesis en

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