A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 1998. / Experiments have been conducted at around 17000C to determine the whether carbothermic reduction of alumina is possible at these temperatures. Total pressure of the system was reduced to around 30 kPa and various metallic solvents such as copper, nickel, iron and tin were used to dissolve the metallic aluminium produced. The use of a solvent (and hence decreasing the activity of metallic aluminium) and a lower pressure are thermodynamic requirements to increase the extent of reduction under a given set of conditions. This enables the use of lower temperatures than are required under atmospheric conditions. The highest recovery of aluminium was achieved with the nickel solvent decreasing in order from iron, copper and tin. This ranking was also in accord with the extent of deviation from ideality in the respective binary solutions of these solvents with aluminiur, The nickel-aluminium system displays the largest negative deviation from ideality whereas the till, aluminium system showed a positive deviation. The rate and extent of the reduction was found to be highly dependent on temperature and pressure. The pseudo first order reaction rate was found to be the primary order for the reduction of aluminium in all the solvents used. It is also suggested that the reduction rate was controlled primarily by chemical reaction rate father than by transport processes. This is due to the extreme sensitivity of the rate and extent of the reaction to temperature. / AC2017

This project was a joint venture between Loughborough University, the academic investigator, and ICI, the industrial sponsor. The aim was to develop and validate filter cycle scale-up methodologies, based on laboratory experiments at Loughborough and full-scale plant work at several ICI sites. Two ICI products, which experience processing problems during filtration, were chosen for assessment. They were a catalyst material (predominately iron oxide), processed by Synetix using rotary vacuum filters (RVFs), and titanium dioxide (TiO2) processed by Tioxide using a diaphragm filter press. A number of objectives were originally highlighted: (1) to develop and validate scale-up methodologies for a pressure filter and vacuum filter; (2) to develop models required to provide accurate predictions of filter performance; (3) to produce PC simulations of RVF and diaphragm filter press; (4) to produce reliable filter cycle data for process feeds of interest to ICI.

Thesis (M.Phil.)--Chinese University of Hong Kong. / Bibliography: leaves 161.

Lai Kam Kwong. / Thesis (M.Sc.)--Chinese University of Hong Kong. / Bibliography: leaves 86-89.

Digitized by Kansas Correctional Industries

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Kwong Kwan Wai = 氧化鋅基低維納米結構之生長與分析 / 鄺筠慧. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 75-79). / Text in English; abstracts in English and Chinese. / Kwong Kwan Wai = Yang hua xin ji di wei na mi jie gou zhi sheng zhang yu fen xi / Guang Yunhui. / Acknowledgement --- p.i / Abstract --- p.ii / 摘要 --- p.iii / Table of Contents --- p.iv / List of Figures --- p.vii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Background --- p.3 / Chapter Chapter 3 --- Instrumentation --- p.6 / Chapter 3.1 --- Tube furnace system --- p.6 / Chapter 3.2 --- X-ray Diffraction (XRD) --- p.8 / Chapter 3.3 --- Scanning Electron Microscopy (SEM) --- p.9 / Chapter 3.4 --- Transmission Electron Microscopy (TEM) --- p.12 / Chapter 3.4.1 --- General Review --- p.12 / Chapter 3.4.2 --- Low-magnification imaging --- p.14 / Chapter 3.4.3 --- Transmission electron diffraction (TED) --- p.14 / Chapter 3.4.4 --- High-resolution electron microscopy (HREM) --- p.15 / Chapter 3.4.5 --- Experimental --- p.15 / Chapter Chapter 4 --- Oxygen partial pressure effect on the morphology of ZnO nanostructures --- p.17 / Chapter 4.1 --- Introduction --- p.17 / Chapter 4.2 --- Experimental --- p.17 / Chapter 4.3 --- Results --- p.19 / Chapter 4.3.1 --- SEM study for general morphology --- p.21 / Chapter 4.3.2 --- TEM study for detailed microstructures of the tetrapods and the nanocombs --- p.28 / Chapter 4.3.2.1 --- Tetrapods --- p.28 / Chapter 4.3.2.2 --- Nanocombs --- p.29 / Chapter 4.4 --- Discussions --- p.34 / Chapter 4.4.1 --- Thermal reduction and oxidation to form ZnO --- p.34 / Chapter 4.4.2 --- Vapor-Solid (VS) growth mechanism of low-dimensional nanostructures --- p.34 / Chapter 4.4.3 --- The oxygen partial pressure effect on the morphology of the ZnO nanostructures --- p.35 / Chapter 4.4.4 --- Transition from tetrapod to nanocomb --- p.36 / Chapter 4.4.5 --- Decreasing size effect --- p.39 / Chapter Chapter 5 --- Self-assembly of periodical ZnO/C multilayers on Zn nanowire --- p.40 / Chapter 5.1 --- Introduction --- p.40 / Chapter 5.2 --- Experimental --- p.42 / Chapter 5.3 --- Results and Discussion --- p.46 / Chapter 5.3.1 --- Freshly synthesized Zn nanowires --- p.46 / Chapter 5.3.2 --- Introducing carbon into the Zn nanowires一Solid phase diffusion --- p.50 / Chapter 5.3.3 --- Introducing carbon into the Zn nanowires一Gas phase reaction --- p.52 / Chapter 5.3.3.1 --- Diffusion of the gas molecules through the ZnO sheath to the Zn/ZnO interface --- p.60 / Chapter 5.3.3.2 --- Chemical reaction(s) --- p.60 / Chapter 5.3.3.3 --- Phase separation of ZnO and C --- p.61 / Chapter 5.3.3.4 --- Self-organized multilayers --- p.62 / Chapter 5.3.3.5 --- Factors affecting SAM formation --- p.64 / Chapter 5.3.3.5.1 --- Crystallinity of original oxide sheath (series A) --- p.64 / Chapter 5.3.3.5.2 --- Temperature (series B) --- p.66 / Chapter 5.3.3.5.3 --- Gas molecules (series C) --- p.69 / Chapter Chapter 6 --- Conclusions --- p.72 / Appendix --- p.74 / References --- p.75

Hung Ngar Chun = 氧化鋅納米棒的生長和表徵 / 洪雅真. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Hung Ngar Chun = Yang hua xin na mi bang de sheng zhang he biao zheng / Hong Yazhen. / Acknowledgements --- p.i / Abstract --- p.ii / 摘要 --- p.iii / List of Tables --- p.iv / List of Figures --- p.v / Table of contents --- p.vii / Chapter Chapter 1 --- Introduction / Chapter 1.1. --- Objectives --- p.1-1 / Chapter 1.2. --- Background --- p.1-1 / Chapter 1.2.1. --- Nanomaterials --- p.1-1 / Chapter 1.2.1.1. --- From three-dimensional to one-dimensional --- p.1-1 / Chapter 1.2.1.2. --- One-dimensional nanomaterials --- p.1-2 / Chapter 1.2.2. --- Characteristics and potential applications --- p.1-2 / Chapter 1.2.3. --- Growth mechanisms --- p.1-4 / Chapter 1.2.3.1. --- The VLS growth --- p.1-4 / Chapter 1.2.3.2. --- The VS growth --- p.1-5 / Chapter 1.2.4. --- ZnO --- p.1-6 / Chapter 1.2.4.1. --- Characteristics and potential applications --- p.1-6 / Chapter 1.2.4.2. --- Recent works performed by the others --- p.1-7 / Chapter 1.2.4.2.1. --- Different fabrication systems --- p.1-7 / Chapter 1.2.4.2.2. --- Different morphologies and shapes --- p.1-8 / Chapter 1.3. --- Our work --- p.1-9 / Chapter 1.3.1. --- Advantages of our fabrication method --- p.1-9 / Chapter 1.4. --- Thesis layout --- p.1-9 / References --- p.1-10 / Figures --- p.1-13 / Tables --- p.1-14 / Chapter Chapter 2 --- Methodology and Experiments / Chapter 2.1. --- Introduction --- p.2-1 / Chapter 2.2. --- The setup --- p.2-1 / Chapter 2.2.1. --- Preparation of substrate --- p.2-1 / Chapter 2.2.2. --- Chamber pressure and gas flow rate --- p.2-2 / Chapter 2.2.3. --- Heating profile --- p.2-2 / Chapter 2.3. --- The two important growth parameters --- p.2-3 / Chapter 2.3.1. --- Substrate compositions --- p.2-3 / Chapter 2.3.2. --- Temperature --- p.2-3 / Chapter 2.4. --- Methods of characterizations --- p.2-4 / Chapter 2.4.1. --- Morphology --- p.2-4 / Chapter 2.4.1.1. --- SEM --- p.2-4 / Chapter 2.4.1.2. --- TEM --- p.2-5 / Chapter 2.4.2. --- Phases and Microstructures --- p.2-5 / Chapter 2.4.2.1. --- XRD --- p.2-5 / Chapter 2.4.2.2. --- HRTEM --- p.2-5 / Chapter 2.4.3. --- Cathodoluminescence --- p.2-6 / References --- p.2-7 / Figures --- p.2-8 / Chapter Chapter 3 --- Results / Chapter 3.1. --- Introduction --- p.3-1 / Chapter 3.2. --- General Morphologies --- p.3-1 / Chapter 3.3. --- Microstructural analysis --- p.3-2 / Chapter 3.4. --- Samples sintered using substrate of different composition --- p.3-2 / Chapter 3.5. --- Samples sintered at different temperatures --- p.3-4 / Chapter 3.6. --- The cathodoluminescence of the ZnO nanorods --- p.3-4 / References --- p.3-6 / Figures --- p.3-7 / Chapter Chapter 4 --- Discussions / Chapter 4.1. --- Introduction --- p.4-1 / Chapter 4.2. --- Proposed growth model --- p.4-1 / Chapter 4.2.1. --- Chemical reactions --- p.4-1 / Chapter 4.2.2. --- Justification on the effect of residue oxygen and leakage --- p.4-2 / Chapter 4.2.3. --- Justification on the possibility of VLS growth --- p.4-3 / Chapter 4.2.4. --- Coarsening mechanisms --- p.4-3 / Chapter 4.2.4.1. --- Oswald Ripening --- p.4-4 / Chapter 4.2.4.2. --- Preferential growth direction --- p.4-4 / Chapter 4.3. --- The effects of substrate composition --- p.4-5 / Chapter 4.3.1. --- Roles of Si and Si02 --- p.4-5 / Chapter 4.4. --- The effects of temperature --- p.4-6 / Chapter 4.4.1. --- Range of sintering temperature --- p.4-6 / Chapter 4.4.2. --- Diameter of the rods --- p.4-7 / Chapter 4.4.3. --- Luminescence behavior --- p.4-7 / References --- p.4-10 / Figures --- p.4-11 / Chapter Chapter 5 --- Conclusions and future works

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In this study it was proposed to investigate the use of 3D metal oxides (specifically titanium oxides) as potential electrode materials for lithium ion batteries. Three different approaches were taken: mesoporous materials to increase the surface area and improve the capacity; nanocrystalline materials to increase the surface area and to investigate any changes that may occur using nanocrystals; and microporous materials that are more open, allowing rapid diffusion of lithium and higher capacities. Of the three categories of materials studies, mesoporous TiO2 was the least promising with low reversible capacities (20 mAh??g-1) due to densification resulting in a loss of surface area. In nanocrystalline rutile an irreversible phase change occurred upon initial intercalation, however after this intercalation occurred reversibly in a single phase mechanism giving capacities of 100 mAh??g-1. A trend in intercalation potential was observed with crystallite size that was related to the ability of the structure to relax and accept lithium. Doping of rutile yielded no real improvement. Brookite gave only low capacities from a single phase intercalation mechanism. TiO2 films produced by a novel electrochemical technique showed that while amorphous films give greater capacities, more crystalline (anatase) films give greater reversibility. Overall, microporous titanosilicates showed the most promise with sitinakite giving a reversible capacity of 80 mAh??g-1 after twenty cycles or double this when dried. The intercalation was found to occur by two steps that generate large changes in crystallite size explaining the capacity fade witnessed. While doping did not improve the performance, cation exchange has proven beneficial. The remaining titanosilicates did not perform as well as sitinakite, however a trend was observed in the intercalation potentials with the wavenumber of the Ti-O Raman stretch. This was due to the covalent nature of the bonding. Upon reduction an electron is added to the bond meaning the energy of the bond determines intercalation potential. Overall, most promise was shown by the microporous titanosilicates. The capacities of sitinakite after drying, are comparable to those of the "zero strain" material Li4Ti5O12. Investigation of the titanosilicates and their ion-exchanged derivatives is a promising path for new lithium-ion battery electrode materials.