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This dissertation summarises the study of different aspects of the aerosol-assisted chemical vapour deposition (AACVD) technique for the production of multi-wall carbon nanotubes (MWCNTs). Upscaling the synthesis while retaining the quality of MWCNTs has been a prime objective throughout the work. A key aspect of this work was the study of different growth parameters and their influence on the homogeneity of the products across the reactor. The effect of the precursor composition on the yield and quality of MWCNTs were also investigated. It was shown that the synthesis rate can be significantly (60 – 80 %) increased by tuning the composition of the precursor. Moreover, by optimising the synthesis recipe and using a larger reactor, the synthesis rate and efficiency of the precursor were increased fivefold (up to 14 g/hr) and twice (up to 88 %) respectively. Large area (up to 90 cm²), mm-thick carpets of MWCNTs which were both free-standing and on substrate were produced. The carpets could withstand normal handlings without tearing apart, making them suitable for macroscopic characterisations and applications. By in-situ qualitative and quantitative gas analysis of the atmosphere of the reactor, the thermocatalytic cracking behaviour of 25 precursors was investigated and a mechanism for successive formation of different hydrocarbon fragments inside the reactor was proposed. A number of dedicated gas analysis methods and apparatuses such as a probe for zone-by-zone gas analysis of reactor and a heated chamber for preparation of standard gas analysis samples were developed to explore some of the least investigated aspects of the thermocatalytic cracking of precursors. Mapping the reactor revealed that some single-wall and double-wall carbon nanotubes (SWCNTs and DWCNTs) were also produced near the exhaust of the reactor. The SWCNTs were partly covered by fullerene-like species and resembled different forms of carbon nanobuds. In addition, the effect of the electron beam on the interaction of the SWCNTs and the fullerene-like species was studied in situ using high-resolution transmission electron microscopy (HRTEM).

The successful utilization of carbon nanomaterials in future electron spin-based technologies is highly dependent upon the ability to control their assembly at the nanoscale to form tailored solid-state architectures. Spin active metallofullerenes (MFs), Sc@C₈₂ and La@C<sub>82,/sub>, can be self assembled in 3D fullerene crystals or inside a carbon nanotube to form peapod structures. Single walled carbon nanotubes (SWCNTs) are an architect material to potentially allow the formation of 1-D spin chains. SWCNTs should be optimised to allow formation of spin chains and free of magnetic catalyst and carbon impurities, which have previously limited investigations of SWCNT spin properties. To address this, SWCNTs produced by laser ablation with a non-magnetic PtRhRe catalyst were purified through a multiple step centrifugation process in order to remove amorphous carbon and catalyst impurities. Centrifugation of SWCNT solutions resulted in sedimentation of carbon nanotube bundles containing clusters of catalyst particles, while isolated nanotubes with reduced catalyst particle content remained in the supernatant. Electron paramagnetic resonance (EPR) signals were detected only for samples which contained catalyst particles, with the ultracentrifuged SWCNTs showing no EPR signal at X-band (9.4 GHz) and fields ≤0.4 T. Integration of MFs into future devices requires a clear understanding of the nature of the spin and spin-spin interactions. Evaluating the spin properties of MFs, in both 3D (crystals) and 1D (peapods), will identify the spin-spin interactions and the affect of the surrounding SWCNT. Diluting spin active Sc@C₈₂ and La@C₈₂ MFs in a diamagnetic C₆₀ matrix, between 0.4% and 100%, permitted the tuning of the mean fullerene separation and thus interfullerene spin interactions. In dilute concentrations of MFs the hyper ne structure was resolved in EPR and with increasing concentration exchange narrowing was observed as a single narrow EPR peak. Encapsulation of Sc@C₈₂ MFs, of varying dilutions, into purified SWCNTs allowed formation of highly ordered 1-D array of metallofullerenes. Changing the spin environment from 3D crystal to 1D peapod resulted in the loss of the observed hyperfine structure in EPR. A single narrow peak was observed for Sc@C₈₂:C₆₀ peapods, indicating significant affect of the surrounding SWCNT structure upon the spin interactions of 1D metallofullerenes. Peapods of Ce@C₈₂ showed a similar EPR signal, suggesting that the observed narrow peak arises from charge transfer between the MF cage and the surrounding SWCNT.

Cubic-phase silicon carbide (andamp;acirc;-SiC) nanostructures were successfully synthesized by the reaction of silicon monoxide (SiO) powder with multi-walled carbon nanotubes (MWCNTs) at high temperatures. Experiments were conducted under vacuum or in the presence of argon gas in a high-temperature furnace and the fabrication parameters of temperature (1300 -1500andamp;deg;C), time, and reactant material mass were varied to optimize the material. The resulting samples were then physically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD analysis revealed the presence of dominant andamp;acirc;-silicon carbide phases. SEM images depicted morphologies similar to the starting MWCNTs, having relatively larger diameter sizes, shorter lengths and reduced curvature. TEM observations showed the presence of solid and hollow nanostructures with both crystalline and amorphous regions. Additional experiments were performed to investigate de-aggregation and dispersion procedures for the andamp;acirc;-SiC nanostructures fabricated. Optimum results for these experiments were achieved by ultrasonication of 0.01 wt.% andamp;acirc;-SiC in N,N dimethyl formamide (DMF) and dispersion using a spin coater. A methodology for electrical testing of andamp;acirc;-SiC nanostructures was developed using the de-aggregation and dispersion process established. SEM observations revealed that the random nature of the dispersion procedure used was not efficient in forming contacts regions that would allow electrical measurements of andamp;acirc;-SiC nanostructures on the pre-patterned silicon substrate.