Philosophiae Doctor - PhD / Metal matrix composites harness the superior attributes of their individual constituents to form high performance materials that would rather be impossible from monolithic substances. Owing to many possible combinations, a myriad of metal matrix composite systems can be fabricated with a metal (or a metal alloy) as a matrix (continuous) phase and a ceramic as a reinforcement (discontinuous) phase. The current study focuses on two matrices, namely Nickel Aluminide and Austenitic Steel as well as two reinforcements namely, Titanium Carbide and Oxynitrides. NiAl alloys are candidates for high temperature structural materials due to their high melting temperature, low density, good thermal conductivity, and excellent oxidation resistance.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第22990号 / 理博第4667号 / 新制||理||1670(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 山本 潤, 教授 石田 憲二, 教授 田中 耕一郎 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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Within in this work, I present the successful synthesis of Ba6Yb2Ti4O17 in a powder form. To the best of my knowledge, this is the first instance in which this has been achieved. I also show that single crystal synthesis experiments using the floating zone synthesis (FZS) technique have yet to produce single crystals. The magnetic characterization of Ba6Yb2Ti4O17 powder is also presented. DC susceptibility measurements reveal no spin freezing or ordering down to 0.5K and inverse susceptibility shows antiferromagnetic coupling between spins. A cold neutron scattering experiment was performed at low temperatures with and without an applied magnetic field on Ba6Yb2Ti4O17 powder. This experiment shows the possibility of spinon-like excitations with a band width of approximately 0.3meV, but this is inconclusive due to the signal to noise ratio. The powder averaged g-tensor for Ba6Yb2Ti4O17 was also experimentally estimated to be approximately 2.4. Further work required to complete this study is also discussed. Synthesis of phase pure ErMgGaO4 has yet to be reported in the literature. Here, I show that small amounts of phase pure polycrystalline ErMgGaO4 can be produced using the FZS technique. Through using FZS, 0.85g of phase pure ErMgGaO4 powder was produced and supplemented using 1.26g of ErMgGaO4 powder containing approximately 1% Er3Ga5O12 magnetic impurity. To estimate the effect of this magnetic impurity on the magnetic signatures exhibited by ErMgGaO4, DC susceptibility measurements were performed between 0.5K and 50K. The magnetic impurity in such small quantity was shown to have negligible effect on the bulk ErMgGaO4 magnetic features. Cold neutron scattering conducted on this material revealed a spinon excitation continuum similar to the one observed in YbMgGaO4.[1] Also present at low temperatures was a diffuse elastic magnetic feature that was used to estimate an order parameter for the material. Analysis of this diffuse feature also revealed a Warren line shape, indicative of two dimensional correlations within the Er3+ triangular planes. Analysis of the spinon excitation continuum revealed a gapless spinon continuum overall. Results presented for both Ba6Yb2Ti4O17 and ErMgGaO4 will be discussed and compared to neutron scattering experiments performed on YbMgGaO4 / Thesis / Master of Science (MSc)

<p> In a study of the structures of some polyatomic cations of Group VI and VII, the compound Se4(HS2O7)2 has been prepared and its structure determined by single crystal X-ray diffraction. The bonding in the square planar cation has been discussed in terms of molecular orbital and valence bond theory. The anion geometry has been discussed and simple rules proposed to predict the changes which occur in bond length and bond angle when one or more oxygen in an SO4 tetrahedron is bonded to another atom or group.</p> <p> A θ/θ vertical diffractometer has been constructed, and computer programmes written, so that cation structures could be determined in solution. The structures of the Se4 2+ and Te4 2+ cations have been determined in fluorosulphuric acid, and are shown to be square planar.</p> <p> Liquid diffraction studies of 3:1, I2/S2O6F2 solutions have shown the presence of a cation containing a linear chain of three iodine atoms.</p> / Thesis / Doctor of Philosophy (PhD)

<p> The symmetries and unit cell dimensions of crystals of Na4P2O7, δ-Ba2P2O7 and H4P2O7 have been determined by X-ray diffraction methods. Changes in symmetry and unit cell dimensions of Na4P2O7 as a function of temperature have been described and a model has been proposed describing the statistics of these changes. The existence of disorder in the crystal structure of δ-Ba2P2O7 has been established and the unit cell dimensions of a previously unreported low temperature form are reported.</p> / Thesis / Master of Science (MSc)

Metal halide perovskites (MHPs) have attracted the attention of researchers particularly in the photo-absorption field. These materials rival traditional semiconductors with their cost-effective ease of synthesis, tunable bandgaps, and excellent photophysical properties. Single-junction MHP solar cells have rivaled current silicon-based photovoltaic devices, boasting a 25.2% light absorption conversion. Recently, MHPs have proven to be effective in x-ray detection. In this paper an investigation of three titanium-based MHPs was conducted. The goal of this research was to characterize the MHPs and determine if they are feasible materials to incorporate in x-ray detectors. After completing the research, two MHP species, FA2TiI6 and MA3TiCl7, were able to be synthesized and characterized. Their crystal systems were determined to be tetragonal with a P4/mmm space group. However, due to equipment limitations, their feasibility in x-ray detectors could not be determined.

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