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付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」 / 京都大学 / 新制・課程博士 / 博士(工学) / 甲第23904号 / 工博第4991号 / 新制||工||1779(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 竹内 繁樹, 教授 川上 養一, 准教授 浅野 卓 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Silicon carbide and silicon nitride turbine engine components are susceptible to hot corrosion by molten sodium sulfate salts which are formed from impurities in the engine's fuel and air intake. Several oxide materials were identified which may be able to protect these components from corrosion and preserve their structural properties. Ta20, coatings were identified as one of the most promising candidates. Thermochemical calculations showed that the chemical vapor deposition(CVD) of tantalum oxide from O2 and TaCI5 precursors is thermodynamically feasible over a range of pressures, temperatures, and reactant concentrations. The deposition of Ta205, as a single phase is predicted in regions of excess oxygen, where the reaction is predicted to yield nearly 100% efficiency. CVD experiments were carried out to deposit tantalum oxide films onto SiC substrates. Depending on the deposition conditions, a variety of coating morphologies have been produced, and conditions have been identified which produce dense, continuous Ta205 deposits. Preliminary corrosion tests on these coatings showed no apparent degradation of the CVD deposited tantalum oxide coatings. The feasibility of depositing ZrTi04 as a coating material was also investigated based on thermochemical considerations. Since no data were available for this material, thermodynamic values were estimated. Thermochemical calculations indicated the chemical vapor deposition of zirconium titanate from O2, ZrCl4, and TiCl4 occurs over a range of temperatures in a very narrow region of the phase diagram. Deviations from the single phase region predicted the codeposition of either Zr02 or Ti02 with ZrTi04. These results suggested that the chemical vapor deposition of ZrTi04 may be difficult from a process handling perspective. Additionally, the process is predicted to be very inefficient, leaving substantial amounts of unreacted chlorides in the reactor exhaust. / Master of Science

Yes / Less than optimal particle isolation techniques have impeded analysis of orthopaedic wear debris in vivo. The purpose of this research was to develop and test an improved method for particle isolation from tissue. A volume of 0.018 mm3 of clinically relevant CoCrMo, Ti-6Al-4V or Si3N4 particles was injected into rat stifle joints for seven days of in vivo exposure. Following sacrifice, particles were located within tissues using histology. The particles were recovered by enzymatic digestion of periarticular tissue with papain and proteinase K, followed by ultracentrifugation using a sodium polytungstate density gradient. Particles were recovered from all samples, observed using SEM and the particle composition was verified using EDX, which demonstrated that all isolated particles were free from contamination. Particle size, aspect ratio and circularity were measured using image analysis software. There were no significant changes to the measured parameters of CoCrMo or Si3N4 particles before and after the recovery process (KS tests, p > 0.05). Titanium particles were too few before and after isolation to analyse statistically, though size and morphologies were similar. Overall the method demonstrated a significant improvement to current particle isolation methods from tissue in terms of sensitivity and efficacy at removal of protein, and has the potential to be used for the isolation of ultra-low wearing total joint replacement materials from periprosthetic tissues.

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This thesis presents a computational study of water and ion dynamics in modified hydrophobic silicon nitride (Si3N4) nanopores, aimed at enhancing protein sequenc- ing technologies. By employing molecular dynamics (MD) simulations, the research investigates the wetting-dewetting behavior within nanopores as an indirect measure of amino acid residue hydrophobicity, focusing on how post-translational modifications (PTMs) of lysine, particularly the acetylation of lysine residues, influence nanopore hydrophobicity and ionic conductance. The study reveals that nanopore radius and hydrophobicity significantly affect water and ion permeation, with smaller nanopores oscillating between open and closed states, while larger ones remain open.  Using umbrella sampling and the Weighted Histogram Analysis Method (WHAM), the potential of mean force (PMF) for potassium (K+), chloride (Cl−), and water within the nanopores was determined, showing distinct PMF profiles based on lysine and acetyl- lysine presence. The modulation of ionic currents as a tool for protein sequencing was explored, demonstrating that different amino acid residues affect ionic currents by par- tially blocking the pore and altering local permeability, thereby enabling differentiation based on size, shape, charge, and hydrophobicity.  The findings suggest that silicon nitride pore hydrophobicity can be tailored for nanopore sequencing, correlating changes in ionic currents with amino acid residue translocation. This research enhances the understanding of interactions within nanopore environments, potentially leading to more precise nanopore-based sequencing methods.

[Truncated abstract] This study investigates the thermal stability of Plasma Enhanced Chemical Vapor Deposited (PECVD) silicon nitride thin films. Effects of heat-treatment in air on the chemical composition, atomic bonding structure, crystallinity, mechanical properties, morphological and physical integrity are investigated. The chemical composition, bonding structures and crystallinity are studied by means of X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) Spectroscopy and Transmission Electron Microscopy (TEM). The mechanical properties, such as hardness and Young’s modulus, are determined by means of nanoindentation. The morphological and physical integrity are analyzed using Scanning Electron Microscopy (SEM) . . . The Young’s modulus (E) and hardness (H) of the film deposited at 448 K were measured to have E=121±1.8 GPa and H=11.7±0.25 GPa. The film deposited at 573 K has E=150±3.6 GPa and H=14.7±0.6 GPa. For the film deposited at 573 K, the Young’s modulus is not affected by heating up to 1148 K. Heating at 1373 K caused significant increase in Young’s modulus to 180∼199 GPa. This is attributed to the crystallization of the film. For the film deposited at 448 K, the Young’s modulus showed a moderate increase, by ∼10%, after heating to above 673 K. This is consistent with the much lower level of crystallization in this film as compared to the film deposited at 573 K. In summary, low temperature deposited PECVD SiNx films are chemically and structurally unstable when heated in air to above 673 K. The main changes include oxidation to SiO2, crystallization of Si3N4 and physical cracking. The film deposited at 573 K is more stable and damage and oxidation resistant than the film deposited at 448 K.