| Nanotechnology has been considered as one of the most promising technologies that will revolutionize our everyday life. Among various low dimensional nanostructures, one-dimensional (1D) nanomaterials have attracted extensive interests due to their distinct anisotropic shape, unique properties, and great potential in different applications, such as catalytic, electronic, optic, optoelectronic, magnetic, mechanical and biological nanoscale realms.;Key words: Nanomaterials, Carbon Nanotubes, Nanowires, Characterization, Chemical Vapor Deposition;In this Ph.D. thesis, multi-walled carbon nanotubes (MWCNTs), nitrogen-doped carbon nanotubes (CNx-NTs) and titanium oxide nanowires have been investigated as the typical hollow and solid 1D nanostructures considering their potential as catalyst supports for fuel cells, sensors and solar cells. Parametric effects on the nanostructure growth were carried out with respect to the involved factors such as temperature, time, catalyst, dopant, substrate and atmosphere. Main information and achievements were summuried as following: (1) Effects of buffer layer and water vapor on the pristine MWCNTs growth were studied in both floating catalyst chemical vapor deposition (FCCVD) and aerosol assisted chemical vapor deposition (AACVD) synthesis methods. Both Al buffer layer and water vapor can improve the growth rate, quality and crystallinity of CNTs. (2) For the CNx-NTssynthesized via FCCVD, the structure and morphology changes from smooth tubular to corrugated structure with the nitrogen content from 0 to 8.4 %. The relationship between the nitrogen content, structure, morphology, bonding environment and crystal lattice vibration were systematically scrutinized. Thermal and chemical stability of the nitrogen within the CNx-NTs was also studied. Results indicated that the nitrogen was stable against high temperatures up to 630°C and exhibited superior stability in acid environment. Interestingly, a new phase was detected at a high pressure of 6.82 GPa. (3) Effects of co-catalysts (Fe-Wand Fe-Mo) on the CNx-NTs growth by AACVD were studied, Due to the complexity of AACVD, growth parameters were firstly optimized. Temperature, hydrogen flow rate and aerosol flow rate were found the prominent factors affecting nitrogen content and morphology of the nanotubes. The influence of binary co-catalysts (Fe-Wand Fe-Mo) on the CNx-NTs growth was carried out. (4) Finally, TiO2 nanowires and carbon-covered TiOx nanostructures were synthesized by chemical vapor deposition. Temperature played an essential role in controlling the nanostructures. Their growth mechanisms were proposed. |
