Carbon based materials such as CNTs and graphene have been widely studied over the last few years. The outstanding electrical and mechanical properties of these materials attracted researchers to find ways to grow and use them in nano-devices. Among the different techniques, PECVD is a relatively simple and low temperature process. It facilitates the growth of CNTs and graphene on particular sites of the substrate. The objective of this research project was to study the growth of CNTs and graphene using PECVD system and to employ them in renewable energy devices. Excimer laser processed materials were also the focus for flexible material for fuel cells and other applications to show the way to a one step manufacturing process that lends itself to large area and low cost processing using standard tools.In the growth of CNTs, the roll of a buffer layer and catalyst materials were studied in depth. Different metals were tested for best results in optimising nanotube growth for the selected applications. The role of the buffer layer in the formation of nanoparticles and their surface adhesion was studied. Different materials were used as a catalyst and analysed for best performance in the PECVD system. Growth parameters such as temperature, pressure, gas flow rate and plasma power were studied during the growth of CNTs in the PECVD system. The growth of graphene has been conducted in two ways: firstly, by the traditional mechanical exfoliation technique (with the help of Manchester University) and second by PECVD techniques.Polymer materials are promising flexible substrates for electronic and energy devices. An excimer laser was used to transform thin metallic films into nanoparticles which could play the role of the catalyst in proton exchange membrane fuel cells. In this study experiments have been conducted into a single step process to convert the poly ethylene naphthalate (PEN) surface to a robust mesoporous carbon material that conducts electrons, whilst depositing the catalyst. Such a technique has been developed for the first time in this work. Laser modification here produced a conical carbon structure and dense arrays of well defined catalysts.A prototype fuel cell was designed and crafted to employ the laser processed PEN as a proton exchange membrane. Some experiments were conducted regarding the transport of protons through laser processed PEN and the conventionally used fuel cell electrolyte, Nafion. It has been observed that the hydrophilic property of Nafion allowed proton transport across this material. It was also observed that PEN is not a good membrane for protonic transport. This material does not have free sites for vehicle transport. The catalytic activity of laser ablated Ni nanoparticles on PEN substrate was studied in temperature programme reaction (TPR) and it was observed that the metallic nanoparticles had some activity at higher temperature. Both Ni and Pt nanoparticles were tested as catalysts on the standard Nafion electrolyte. It was observed that Pt is active for the hydrogen combustion reaction and Ni has less activity for this purpose.It was not expected in this work that efficient hydrogen transport through the polymer would occur, but that future modification of the internal chemistry of PEN can be developed.

Pour mieux comprendre leurs propriétés, diverses nanostructures individuelles ont été étudiées à l’aide d’une technique couplant microscopie à force atomique et spectroscopie Raman confocale. Sous excitation lumineuse polarisée, la composition chimique, la structure et la présence de défauts a pu être précisée dans des nanobâtonnets d’oxydes métalliques (ZnO et α-Fe2O3). Sous irradiation laser résonnante, les spectres de nanotubes de carbone monoparoi enrobés de polymères ont révélé notamment l’absence de transfert de charge polymère-nanotube et un effet de désolvatation. Finalement, des feuillets de graphène oxydé et des ADNs double-brin peignés ont pu être préparés et caractérisés par spectroscopie Raman exaltée par effet de pointe en atteignant une résolution spatiale latérale voisine du rayon de courbure de l’apex de la pointe utilisée (12 nm), bien plus faible que la limite de diffraction, ce qui ouvre la voie à de nouveaux travaux spectroscopiques à l’échelle nanométrique. / To better understand their properties, various nanostructures have been studied using a technique combining atomic force microscopy and confocal Raman spectroscopy. Under polarized light excitation, the chemical composition, the structure and the presence of defects has been described in metal oxides nanorods (ZnO et α-Fe2O3). Under resonant laser excitation, Raman spectra of polymer-wrapped single-walled carbon nanotubes have revealed the absence of polymer-nanotube charge transfer and an effect due to desolvation. Finally, graphene oxide sheets and combed double-stranded DNAs have been prepared and characterized using tip-enhanced Raman spectroscopy with a lateral spatial resolution down to the curvature radius of the apex of the used tip (12 nm), well below the diffraction limit, which opens new opportunities for spectroscopic works at the nanometer scale.

One of the most significant issues in nanocomposite performance is improving the dispersion of carbon nanotubes (CNTs) in thermosetting or thermoplastic polymers in order to gain good mechanical properties. Several studies have investigated the fabrication of nanocomposites based on carbon nanotubes and analysed properties, but there is still insufficient data on their structure-property relationships. This thesis has investigated the central importance of stress transfer Raman studies in epoxy composites reinforced with single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs) and multiwall carbon nanotubes (MWCNTs) to elucidate the reinforcing ability of the CNTs in an epoxy matrix. This project was undertaken to synthesise and characterize MWCNTs and determine the effect of different weight fractions of untreated MWCNTs on the stress transfer efficiency at the MWCNTS / epoxy interface and on the stiffness of the thermomechanical properties of the MWCNTS / epoxy composites. It was undertaken to assess the stress transfer efficiency at the CNT / epoxy interface and at the inter-walls of the CNTs with tensile deformation and with cyclic loading.Optimized conditions of the injection chemical vapour deposition method (CVD), such as long injection times were applied to produce MWCNTs with a high yield, high aspect ratio and well-defined G' Raman peak. The morphology and size of CNTs were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) while their thermal stability was examined by Thermogravimetric analysis (TGA). Both Raman spectroscopy and mechanical testing (static and dynamic) were utilized in this study. The Raman spectroscopy research consisted of following the G'-band frequency and linewidth as well as the intensity of radial breathing modes (RBMs) during tensile deformation. The stress-induced Raman shifts in the nanocomposites have been shown to be controlled by the number of carbon nanolayers. A theory has been developed to determine and simulate the stress transfer efficiency parameter, (k_i) for MWCNTs. Tensile tests and dynamic mechanical testing were used to assess the mechanical properties of the nanocomposites.The most obvious finding to be drawn from the present study is that the reinforcement of the epoxy resin with different loadings of MWCNTs is useful, but the best reinforcement was at low loadings of MWCNTs. One of the more significant findings to emerge from this study is that (k_i) between the inner walls of the DWCNTs and MWCNTs are quite similar (~0.7), which suggest that (k_i) may be similar for all CVD MWCNTs and DWCNTs. The second major finding was that there were RBM intensity variations for the SWCNTs and DWCNTs in the hot-cured epoxy composites and that for the DWCNTs both the inner and outer nanotube walls are stressed during deformation

No description available.