Victoria University

Synthesis of Multi-Walled Carbon Nanotubes by Chemical Vapour Deposition and Post-Synthesis Treatment by Dielectrophoresis

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dc.contributor.advisor Kaiser, Alan
dc.contributor.advisor Spencer, John Liu, Xianming 2009-01-08T22:02:32Z 2009-01-08T22:02:32Z 2006 2006
dc.description.abstract Carbon nanotubes (CNTs) are a group of pure carbon solid materials that possess one-dimensional structures with diameters down to less than one nanometre. They have interesting physical properties such as very high tensile strength, metallic and semiconducting conductivity, and great potential for applications. This work investigates the synthesis, alignment and purification of multi-walled carbon nanotubes, which were characterized by Electron Microscopy, measurement of electrical properties and Raman scattering. Synthesis of multi-walled carbon nanotubes (MWNTs) was carried out by Chemical Vapour Deposition, using three different precursors: Fe(NO3)3, ferrocene and iron phthalocyanine. Vertically aligned "forests" of large numbers of MWNTs were achieved using ferrocene and iron phthalocyanine as precursors. Products from iron phthalocyanine yield more graphitic CNT nanostructures, as determined by Scanning Electron Microscopy, Transmission Electron Microscopy, Thermogravity Analysis, Raman microscopy and Energy Dispersive X-ray spectroscopy. Patterned growth of vertical MWNTs arrays with a resolution of 2 microns was also obtained, using a predeposited substrate. A High Resolution Transmission Electron Microscope was employed to investigate the inner structures of individual MWNTs, giving well-resolved images of concentric nanostructures with inter-lattice spacings of 0.34 nm. Techniques for purification and manipulation of CNTs are required before CNTs' excellent properties can be exploited. In this thesis, dielectrophoresis (DEP) under high-frequency AC voltages using an array of micron-scale electrodes was adopted as the technique to align MWNTs between these, electrodes. This technique is effective for MWNTs since their long cylindrical structure and the high mobility of their charge carriers allow them to be electrically polarised. As a result, MWNTs experience large DEP forces in an AC electric field. In our experiments, inter-digitated electrodes were used to apply the electric field to CNT suspensions in various solvents. Alignment of CNTs along their axis was achieved within the gaps between adjacent electrodes at a frequency larger than 1.1 MHz, The AC admittance changes between the electrodes were monitored and were observed to be a clear reflection of the accumulation process of MWNTs. Also it was identified that distilled water was a better solvent than ethanol and isopropanol for DEP purpose on MWNTs. In addition, a prototype device was built to selectively purify MWNTs from as-grown samples by combining DEP and re-circulating fluid flow. It was found that this device is able to decrease the impurity content of MWNTs, which is collected on the electrode array, from the suspension of as-grown samples. en_NZ
dc.language.iso en_NZ
dc.publisher Victoria University of Wellington en_NZ
dc.subject Nanostructured materials en_NZ
dc.subject Dielectrophoresis en_NZ
dc.subject Carbon en_NZ
dc.subject Chemical vapor deposition en_NZ
dc.subject Nanotubes en_NZ
dc.title Synthesis of Multi-Walled Carbon Nanotubes by Chemical Vapour Deposition and Post-Synthesis Treatment by Dielectrophoresis en_NZ
dc.type Text en_NZ
vuwschema.contributor.unit School of Chemical and Physical Sciences en_NZ
vuwschema.subject.marsden 250101 Chemical Thermodynamics and Energetics en_NZ
vuwschema.subject.marsden 250301 Organic Chemical Synthesis en_NZ
vuwschema.subject.marsden 250403 Electroanalytical Chemistry en_NZ
vuwschema.type.vuw Awarded Doctoral Thesis en_NZ Chemistry en_NZ Victoria University of Wellington en_NZ Doctoral en_NZ Doctor of Philosophy en_NZ
vuwschema.subject.anzsrcfor 039999 Chemical Sciences not elsewhere classified en_NZ

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