The report of the presence of LaC<sub>2</sub> and YC<sub>2</sub> encapsulated in carbon shell layers found in a carbonaceous deposit grown on a cathode surface of a carbon arc has attracted particularly great interest because encapsulating materials in the hollow core of carbon nanostructures (nanocapsules/nanotubes) had changed the physical properties of the encapsulated materials. Not only does the process offer an opportunity to investigate dimensionally confined systems, but also the encapsulated materials are likely to be immune to environmental effects or degradation, because of the protective carbon sheets around them. The formation of carbon encapsulated ferromagnetic nanoparticles and nanowires has been the goal of this research. Three novel techniques for the formation of carbon encapsulated ferromagnetic nanoparticles are introduced in this thesis: Carbon Arc in Localized Gas Pressure (CA), Water Arc Discharge (WA) and Pulsed Laser Deposition (PLD). In addition, a new technique of producing encapsulated ferromagnetic nanowires by nanotube-assisted oriented attachment is also introduced. The resultant materials have had their structural and magnetic properties assessed by High Resolution Transmission Electron Microscopy (HRTEM), X-Ray Diffraction (XRD) and Vibrating Sample Magnetometer (VSM) respectively. A carbon arc technique has been modified by creating a N<sub>2</sub> gas jet through the office of the anode, which resulted in a localized gas pressure in the arc region. The second technique successfully implemented has been that of the electric arc submerged in deionised water inside a 2.5 litre breaker. The third technique that has been explored is PLD. In our experiments, a KrF 248 nm Lambda Physique excimer laser was used to ablate two composite targets composed of Co + C (80 wt% Co) and Ni + C (80 wt% Ni) under the pressure of N<sub>2</sub> gas jet respectively. Pulsed laser respectively. Pulsed laser deposition coupled with the addition of N<sub>2</sub> gas jet has successfully been employed to grow carbon encapsulated Co and Ni nanoparticles with small means particle sizes of 12.4 and 15.5 nm respectively. Finally, a new technique in growing ferromagnetic nanowires encapsulated in carbon tubules through oriented attachment is presented. The process is based on the evaporation of fluorocarbon capsule (PCTFE in this case) over ferromagnetic particles dissolved in toluene onto lacey carbon TEM grids at 375°C for 72 hours.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:596121 |
| Date | January 2006 |
| Creators | Ang, K. H. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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