Doctor of Philosophy / Department of Chemical Engineering / Placidus B. Amama / Advances in synthesis and processing of nanocarbon materials, particularly graphene, have presented the opportunity to design novel Li-ion battery (LIB) anode materials that can meet the power requirements of next-generation power devices. This thesis presents three studies on electrochemical behavior of three-dimensional (3D) nanostructured anode materials formed by pure graphene sheets and graphene sheets coupled with conversion active materials (metal oxides). In the first project, a microgel-templated approach for fabrication of 3D macro/mesoporous reduced graphene oxide (RGO) anode is discussed. The mesoporous 3D structure provides a large specific surface area, while the macropores also shorten the transport length of Li ions. The second project involves the use of a novel magnetic field-induced method for fabrication of wrinkled Fe3O4@RGO anode materials. The applied magnetic field improves the interfacial contact between the anode and current collector and increases the stacking density of the active material. The magnetic field treatment facilitates the kinetics of Li ions and electrons and improves electrode durability and the surface area of the active material. In the third project, poly (methacrylic acid) (PMAA)-induced self-assembly process was used to design super-mesoporous Fe3O4@RGO anode materials and their electrochemical performance as anode materials is also investigated. To establish correlations between electrode properties (morphological and chemical) and LIB performance, a variety of techniques were used to characterize the samples. The significant improvement in LIB performance of the 3D anodes mentioned above is largely attributed to the unique properties of graphene and the resulting 3D architecture.

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Abstract Experimental synchrotron radiation induced electron- and ion spectroscopies together with electron-ion and ion-ion coincidence techniques as well as electron energy loss spectroscopy have been used to study the electronic properties of several vapor phase samples. In this thesis studies of the electronic structure and fragmentation of Sb4 clusters, photo- and Auger electron spectroscopy of atomic Si and Pb as well as ultra high resolution VUV absorption of vapor phase KF molecules have been performed. The instrumentation and techniques used in the studies, especially the electron energy loss apparatus and the newly built ultra high resolution FINEST beamline branch, are presented.

Li-ion batteries have become the more dominant battery type used in portable electronic devices such as cell phones, computers and more recently their application in full electric vehicles (EV). Li-ion batteries have many advantages over the traditional rechargeable systems (Pb-acid and Ni-MH) such as their higher energy density, low self-discharge, long capacity cycle life and relatively maintenance free. Due to their commercial advantages, a lot of research is done in developing new novel Li-ion electrode materials, improving existing ones and to reduce manufacturing costs in order to make them more cost effective in their applications. This study looked at the cathode material chemistry that has a typical spinel manganese oxide (LiMn2O4) type structure. For comparison the study also considered the influence of doping the phase with various metals such as Al, Mg, Co and Ni that were made as precursors using various carboxylic acids (Citric, Ascorbic, Succinic and Poly-acrylic acid) from a sol-gel process. Traditional batch methods of synthesizing the electrode material is costly and do not necessarily provide optimized electrochemical performance. Alternative continuous less energy intensive methods would help reduce the costs of the preparation of the electrode materials. This study investigated the influence of two synthesis techniques on the materials physical and electrochemical characteristics. These synthesis methods included the use of a typical batch sol-gel method and the continuous spray-drying technique. The spinel materials were prepared and characterized by Powder X-Ray Diffraction (PXRD) to confirm the formation of various phases during the synthesis process. In addition, in-situ PXRD techniques were used to track the phase changes that occurred in the typical batch synthesis process from a sol-gel mixture to the final crystalline spinel oxide. The materials were also characterized by thermal gravimetric analysis (TGA), whereby the materials decomposition mechanisms were observed as the precursor was gradually heated to the final oxide. These synthesized materials prepared under various conditions were then used to build suitable Li-ion coin type of cells, whereby their electrochemical properties were tested by simple capacity tests and electrochemical impedance spectroscopy (EIS). EIS measurements were done on the built cells with the various materials at various charge voltages. TG analysis showed that the materials underwent multiple decomposition steps upon heating for the doped lithium manganese oxides, whereas the undoped oxide showed only a single decomposition step. The results showed that all the materials achieved their weight loss below 400 °C, and that the final spinel oxide had already formed. The in-situ PXRD analysis showed the progression of the phase transitions where certain of the materials changed from a crystalline precursor to an amorphous intermediate phase and then finally to the spinel cathode oxide (Li1.03Mg0.2Mn1.77O4, and LiCo1.09Mn0.91O4). For other materials, the precursor would start as an amorphous phase, and then upon heating, convert into an impure intermediate phase (Mn2O3) before forming the final spinel oxide (Li1.03Mn1.97O4 and LiNi0.5Mn1.5O4). The in-situ study also showed the increases in the materials respective lattice parameters of the crystalline unit cells upon heating and the significant increases in their crystallite sizes when heated above 600 °C. Hence the results implied that a type of sintering of the particles would occur at temperatures above 600 °C, thereby increasing the respective crystallite size. The study showed that the cathode active materials made by the sol-gel spray-drying method would give a material that had a significantly larger surface area and a smaller crystallite size when compared to the materials made by the batch process. The electrochemical analysis showed that there was only a slight increase in the discharge capacities of the cells made with the spray-drying technique when compared to the cells made with the materials from the batch sol-gel technique. Whereas, the EIS study showed that there were distinct differences in the charging behavior of the cells made with the various materials using different synthesis techniques. The EIS results showed that there was a general decrease in the cells charge transfer resistance (Rct) as the charge potential increased regardless of the synthesis method used for the various materials. The results also showed that the lithium-ion diffusion coefficient (DLi) obtained from EIS measurements were in most of the samples higher for the cathode materials that had a larger surface area. This implied that the Li-ion could diffuse at a faster rate through the bulk material. The study concluded that by optimizing the synthesis process in terms of the careful control of the thermal parameters, the Li-ion batteries‟ cathode active material of the manganese spinel type could be optimized and be manufactured by using a continuous flow micro spray process.

Influenza viral infection causes several hospitalizations and claims the lives of many people each year. The threat of epidemic and pandemic are more pressing than ever with newly mutated strains developing every year. Understanding the mechanism of infection of influenza can help identify new potential drug targets and help progress the development of antivirals. Currently there are two classes of FDA approved drugs, neuraminidase inhibitors and M2 ion channel inhibitors, to combat influenza infection. Unfortunately, viral resistance to M2 ion channel blockers has caused them to stop being used for treatment. This paper focuses on understanding influenzas ability to mutate and it mechanism of infection to develop new M2 ion channel blockers.

This thesis reports the development of a model to explain the electrical properties of Si implanted GaAs. The results show that most of the implanted silicon atoms occupy lattice sites and are electrically active. The net carrier concentration is determined by the relative concentration of silicon atoms on gallium and arsenic lattice sites respectively. The activation mechanism is shown to involve the breaking up of complex defects in the form of substitutional silicon with vacancies. The energy required for this process is about 1 to 1.5 eV. A lower value of activation energy (about 0.5 eV) has also been measured and is suggested to be associated with the site switching of silicon from arsenic to gallium sites, when a gallium vacancy diffuses close to a silicon on an arsenic site. This process has diffusion energy of about 2.5 to 3.0 eV. The activation energy obtained from sheet carrier concentration measurements corresponds to a combination of the two activation mechanisms. Which of these mechanisms is observed in an experiment depends on various parameters, such as the implantation conditions, the quality of the encapsulant and the annealing conditions. The model can explain the variations in activation energy (0.5 to 1.5 eV) reported in the literature.

The use of radio frequency (rf) plasma techniques to produce fine structures of precise geometry is widespread in the microelectronics industry. An important factor influencing the functionality of fabricated devices is the wall angle of these structures. In certain applications vertical walls are required - for example to minimise mask degradation and maximise gate densities; in others a sloping sidewall is preferred - to minimise stress in metal coatings when making electrical contact through 'via' holes, for instance. This fine control cannot be achieved on micron and sub-micron scale devices using conventional 'wet' chemical processing techniques and has led to the adoption of so-called 'dry' processing techniques using plasmas. Both vertical and sloping wall profiles can be produced depending upon the plasma conditions. It is apparent, therefore, that a thorough understanding of the processes affecting the etch profile is important. Reactive ion etching (RIE) has been employed to produce micron, and sub-micron size structures in polyimide using an oxygen plasma. Present models of etch directionality all make the initial assumption that the directional component of the etching process can be attributed solely to O2+ ion bombardment of the exposed horizontal surface of the wafer driven by the electric 'sheath' field developed above the electrode. Whether species such as O+ and even multiply charged reactive species such as O++ and O+++ can legitimately be neglected in formulating such a model has yet to be established. That such multiply ionized species exist, however, is highly probable given that plasmas are well known to emit strongly in the ultraviolet. The etching system developed to investigate these problems was equipped with diagnostic techniques including optical emission spectroscopy, mass spectrometry, and a grid energy analyser. The optical emission spectrometer was novel in being capable of measuring emission from the far-ultraviolet emission spectrum of the plasma and was therefore able to detect the high energy ultraviolet light and the singly and multiply ionised species from which this radiation is emitted. Using this technique the role of multiply-ionised species in controlling etch anisotropy was investigated. Results are also presented, obtained from a retarding grid, particle energy analyser built into the surface of the earth electrode, which indicate increased charged particle flux and energy at low pressure providing further information with regard to the process dynamics. The influence of gas pressure and rf excitation frequency on the resultant etch profile have been investigated. Results are presented showing the presence of doubly-ionised atomic oxygen O++ in the plasma. It is shown in this work that O++ also has a role in etch anisotropy at low pressure. This and other more highly charged species need to be considered, therefore, in formulating models of etch anisotropy, etch rate, and etch chemistry and reaction mechanisms. The role of ultraviolet irradiation which is itself of sufficient energy to induce surface reactions must also be considered.

Plasma Immersion Ion Implantation has several unique advantages over conventional implantation, such as low cost, large area capability, non-line-of-sight features and high dose rate implantation. However, it is still far from use in routine production because of problems such as the ability to control the ion depth profile in targets, the ion dose and contamination. In this thesis, a PIII system has been systematically calibrated, and a computer simulation code for PIII has been developed in order to understand more clearly the physics of the PIII process and to optimise the experimental conditions. In the second part of this thesis, a new application of PIII has been explored, where the PIII technique has been used as a high dose-rate implant treatment to form amorphous silicon nitride/oxide films on both crystalline and amorphous silicon substrates. The electrical properties of these films have been characterized. It shows that low dose nitrogen/oxygen implantation leads to the modification of Schottky barrier heights or the introduction of charged defects in the materials. As the ion dose is increased, alloying effects take over, forming silicon nitride/oxide alloys. The a-SiNx:H films synthesized via PIII have electrical characteristics similar to those grown by PECVD, but a-SiOx:H has different electrical properties from a-SiNx:H.