Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Vita. / Includes bibliographical references. / by Normand Denis Corbin. / M.S.

Thesis (M.Sc. (Physics)) -- University of Limpopo, 2020. / This dissertation presents the results of the ab-initio based computational studies of spinel lithium manganese oxide (LiMn2O4) bulk, surfaces, and the adsorption of an organic electrolyte, ethylene carbonate. The spinel LiMn2O4 is one of the most promising cathode materials for Lithium-ion batteries because of its affordability, nontoxicity, and improved safety compared to commercially used LiCoO2. However, it also suffers from the irreversible capacity due to the electrolyte-cathode interactions which lead to manganese (Mn) dissolution. Using the spin-polarized density functional theory calculations with on site Coulomb interactions and long-range dispersion corrections [DFT+U−D3−(BJ)], we investigated the bulk properties, surface stability and surface reactivity towards the ethylene carbonate (EC) during charge/discharge processes. Firstly, we explored the structural, electronic, and vibrational bulk properties of the spinel LiMn2O4. It was found that the bulk structure is a stable face-centred cubic structure with a bandgap of 0.041 eV and pseudo-gap at the Fermi level indicating electronic stability. Calculated elastic constants show that the structure is mechanically stable since they obey the mechanical stability criteria. The plotted phonon curves show no imaginary vibrations, indicating vibrational stability. To study the charge/discharge surfaces, we modelled the fully lithiated and the partially delithiated slabs and studied their stability. For the fully lithiated slabs, Li-terminated (001) surface was found to be the most stable facet, which agrees with the reported experimental and theoretical data. However, upon surface delithiation, the surface energies increase, and eventually (111) surface becomes the most stable slab as shown by the reduction of the plane in the particle morphologies. Finally, we explored the surface reactivity towards the ethylene carbonate during charge/discharge processes. The ethylene carbonate adsorption on the fully lithiated and partly delithiated facets turn to enhance the stability of (111) surface. Besides the strong interaction with the (111) surfaces, a negligible charge transfer was calculated, and it was attributed by a large charge rearrangement that takes place within the surfactant upon adsorption. The wavenumbers of the C=O stretching showed a red shifting concerning the isolated EC molecule

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 1977 / Vita. / Includes bibliographical references. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Materials Science and Engineering

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 315-334. / Ph.D.

Size and Shape Controlled Synthesis and Superparamagnetic Properties of Spinel Ferrites Nanocrystals Qing Song 216 pages Directed by Dr. Z. John Zhang The correlationship between magnetic properties and magnetic couplings is established through the investigations of various cubic spinel ferrite nanocrystals. The results of this thesis contribute to the knowledge of size and shape controlled synthesis of various spinel ferrites and core shell architectured nanocrystals as well as the nanomagnetism in spinel ferrites by systematically investigating the effects of spin orbital coupling, magnetocrystalline anisotropy, exchange coupling, shape and surface anisotropy upon superparamagnetic properties of spinel ferrite nanocrystals. A general synthetic method is developed for size and shape control of metal oxide nanocrystals. The size and shape dependent superparamagnetic properties are discussed. The relationship between spin orbital coupling and magnetocrystalline anisotropy is studied comparatively on variable sizes of spherical CoFe2O4 and Fe3O4 nanocrystals. It also addresses the effect of exchange coupling between magnetic hard phase and soft phase upon magnetic properties in core shell structured spinel ferrite nanocrystals. The role of anisotropic shapes of nanocrystals upon self assembled orientation ordered superstructures are investigated. The effect of thermal stability of molecular precursors upon size controlled synthesis of MnFe2O4 nanocrystals and the size dependent superparamagnetic properties are described.

In this presentation it is demonstrated that the unique magnetic properties of superparamagnetic cobalt-spinel ferrite nanoparticles can be employed in several novel applications. A method to selectively capture and remove pathogens from infected organisms to improve longevity is presented. Evidence is provided to show that automated methods using modified forms of hemofiltration or peritoneal dialysis could be used to eliminate the particle/pathogen or particle/infected cell conjugates from the organism postoperatively. It is shown that disparately functionalized nanoparticles can be used in concert as drug carrier and release mechanisms. Lastly, we provide preliminary evidence to support the use of magnetic nanoparticles for controlling reaction kinetics.