The dissertation consists of the following three sections: 1. Hydroxyapatite (HA) coatings. In this work, we deposited HA precursor films from weak basic electrolytic solution (pH= 8-9) via an electrochemical approach; the deposits were changed into crystallite coatings of hydroxyapatite by sintering at specific temperatures (600-800 ºC). The formed coatings were mainly characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). XRD patterns show well-defined peaks of HA when sintered under vacuum conditions. FTIR measurements indicate the existence of hydroxyl groups, which were confirmed by the characteristic intensity of the stretching and bending bands at ~3575 and ~630 cm-1, respectively. The SEM shows an adhesive, crack free morphology for the double-layer coating surface of the samples sintered in a vacuum furnace. 2. Silver/polymer/clay nanocomposites. Silver nanoparticles were prepared in layered clay mineral (montmorillonite)/polymer (PVP: poly (vinyl pyrrolidone)) suspension by an electrochemical approach. The silver particles formed in the bulk suspension were stabilized by the PVP and partially exfoliated clay platelets, which acted as protective colloids to prevent coagulation of silver nanoparticles together. The synthesized silver nanoparticles/montmorillonite/PVP composite was characterized and identified by XRD, SEM, and TEM (transmission electron microscopy) measurements. 3. Ce-doped lead zirconate titanate (PZT) thin films. In this study, we fabricated cerium-doped PZT films (molar ratio of Zr/Ti:: 0.5:0.5) via cathodic electrodeposition on the indium tin oxide ( ITO) coated glass substrate. In the preparation process, the PZT films were modified by adding a small amount of cerium dopants, which led to the formation of Ce-doped PZT films after sintering at high temperatures. The fabricated PZT films on the ITO coated glass substrate may be used as electro-optic devices in the industrial application.

O poli(tereftalato de etileno), PET, é um material polimérico importante, largamente utilizado na produção de garrafas para refrigerante e água mineral. Entretanto, a destinação das embalagens de PET pós-consumo vem criando sérias preocupações econômicas e ambientais. Uma das alternativas de destino desse material é a reciclagem química por glicólise, tendo como objetivo a produção do monômero tereftalato de bis-hidroxietila (BHET). Esta reação, embora referenciada, ainda apresenta problemas como rendimento de BHET e tempo de reação, entre outros, tendo como desafio o desenvolvimento de novos catalisadores eficientes e altamente seletivos. Dentro deste contexto, o presente trabalho busca estudar a atividade catalítica de um material nanoestruturado, os nanotubos de titanatos (TNT), na glicólise de PET (virgem e pós-consumo) comparado ao acetato de zinco (catalisador mais utilizado citado em literatura), a otimização de alguns parâmetros reacionais (granulometria de PET pós-consumo, razão Etilenoglicol:PET, porcentagem molar de TNT) e uma modificação dos nanotubos com zinco (ZnTNT) na despolimerização do PET Para a caracterização dos produtos as principais técnicas utilizadas foram a Calorimetria Exploratória Diferencial (DSC), Análise Termogravimétrica (TGA) e Ressonância Magnética Nuclear (RMN), além de resultados de rendimento, turnover number (TON) e turnover frequency (TOF). A despolimerização ocorreu por reação de glicólise utilizando PET virgem e pós-consumo e etilenoglicol para diferentes tempos a uma temperatura de 196°C. Os principais resultados mostram os TNT como catalisadores promissores, apresentando rendimentos em BHET de 83,9 e 76,7%, para PET virgem e pós-consumo, respectivamente, para 3 horas de reação. Esses valores são equiparáveis aos obtidos quando utilizado acetato de zinco, em que foi alcançado 79,4% (PET virgem) e 80,8% (PET pós-consumo). Após a modificação dos TNT com zinco, os resultados de rendimento em BHET alcançaram 87,1% para 3 horas de reação na menor granulometria estudada, demonstrando ser um catalisador ainda mais eficiente para essa reação. / Polyethylene terephthalate, PET, is an important polymer material, widely used in the production of bottles for soda and mineral water. However, the disposal of post-consumer PET packaging has created serious economic and environmental concerns. One of the alternatives for the disposal of this material is the chemical recycling by glycolysis, aiming the production of the monomer bis-(2hydroxyethyl) terephthalate (BHET). This reaction, although referenced, still presents problems such as BHET yield and reaction time, among others, having as challenge the development of new efficient and highly selective catalysts. In this context, the present work aims to study the catalytic activity of a nanostructured material, the titanate nanotubes (TNT) in PET glycolysis (virgin and post-consumer) compared to zinc acetate (the most used catalyst cited in literature), the study of some reaction parameters (post-consumer PET granulometry, Ethylene glycol:PET ratio and TNT molar percentage) and a modification of the catalyst with zinc (ZnTNT) in the depolymerization of PET For the characterization of the products, the main techniques used were Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Nuclear Magnetic Resonance (NMR), as well as yield, turnover number (TON) and turnover frequency (TOF) results. The depolymerization occurred by glycolysis reaction using virgin and post-consumer PET and ethylene glycol at different times at a temperature of 196°C. The main results show TNT as promising catalysts, with yields of BHET yields of 83.9 and 76.7%, for virgin and post-consumer PET, respectively, for 3 hours of reaction. These values are similar to those obtained when zinc acetate was used, in which 79.4% (virgin PET) and 80.8% (post-consumer PET) were reached. After the modification of the TNT with zinc, the yield results in BHET reached 87.1% for 3 hours of reaction at the smaller particle size studied, proving itself to be an even more efficient catalyst for this reaction.

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第22550号 / 人博第953号 / 新制||人||226(附属図書館) / 2019||人博||953(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 吉田 寿雄, 教授 内本 喜晴, 教授 田部 勢津久 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

Diese Arbeit beschäftigt sich mit den elektrischen Eigenschaften der resistiven Schaltmaterialien SrTiO3 und NbO2. Im ersten Teil werden NbO2 (001)-Dünnschichten untersucht. Bisher sind die für NbO2-Dünnschichten in der isolierenden Phase gemessenen spezifische Widerstände um einen Faktor von 200 niedriger als der in NbO2-Einkristallen gemessene 10 kΩ cm Widerstand. In dieser Arbeit wird der spezifische Widerstand von NbO2-Dünnschichten auf 945 Ω cm erhöht. Es wird gezeigt, dass leitfähige Perkolationspfade entlang der Korngrenzen für die Abnahme des spezifischen Widerstandes verantwortlich sind. Durch temperaturabhängige Leitfähigkeitsmessungen wurden Defektzustände identifiziert, die für die Verringerung des spezifischen Widerstandes gegenüber dem theoretischen Wert verantwortlich sind. Im zweiten Teil wird der Einfluss des Ti-Antisite Defekts auf das resistive Schalten in SrTiO3 Dünnschichten untersucht, welche mit metallorganischer Dampfphasenepitaxie gezüchtet wurden. Dabei werden sowohl stoichiometrische als auch Strontium defizitäre Schichten untersucht. Es wird über temperaturabhängige Permittivitätsmessungen gezeigt, dass durch Kristalldefekte die weiche Phononenmode gestört wird und bei stark strontiumverarmten Schichten polare Nanoregionen gebildet werden, was auf die Bildung des TiSr Defekts zurückgeführt wurde. Darüber hinaus wird gezeigt, dass stark strontiumdefiziente SrTiO3 -Schichten ein stabiles resistives Schalten mit einem Ein-Aus-Verhältnis von 2e7 bei 10 K aufweisen, während stöchiometrische Dünnschichten kein stabiles Schalten zeigen. Es wird ein diodenartiger Transportmechanismus, der im hochohmigen Zustand auf Schottkyemission beruht und ihm niederohmigen Zustand durch defektassistierten Tunnelstrom dominiert wird, identifiziert. Daraus wurde ein neues Modell für das resistive Schalten, basierend auf dem TiSr Defekt und der induzierten Ferroelektrizität, entwickelt. / In this work, the impact of crystal defects on the resistive switching materials SrTiO3 and NbO2 is investigated. The work is divided into two parts. In the first part, NbO2 (001) thin films are studied. So far, resistivities measured for NbO2 thin films in the insulating phase are by a factor of 200 lower than the 10 kΩ cm resistivity measured in NbO2 single crystals. To make this material applicable for resistive switching, the resistivity in the insulating phase has to be increased to effectively block the current in the high resistive state. Throughout the investigations presented in this work, the resistivity of NbO2 thin films is increased to 945 Ω cm. It is shown that conductive percolation paths along the grain boundaries are responsible for the decrease in resistivity. Temperature-dependent conductivity measurements identified defect states responsible for the reduction in resistivity from the theoretical value. In the second part of this work, the influence of the Ti anti-site defect on resistive switching in SrTiO3 thin films grown by metal-organic vapor phase epitaxy is studied. Both stoichiometric and strontium deficient thin films are studied. It is shown via temperature-dependent permittivity measurements that crystal defects harden the soft phonon mode and polar nano regions are formed in highly strontium deficient films, which was attributed to the formation of Ti antisite defects. In addition, highly strontium deficient SrTiO3 films are shown to exhibit stable resistive switching with an on-off ratio of 2e7 at 10 K, whereas stoichiometric thin-films do not show stable switching. A diode-like transport mechanism based on Schottky emission in the high-resistance state and dominated by defect-assisted tunneling current in the low-resistance state is identified. From this, a new model for resistive switching based on the Ti antisite defect and the induced ferroelectricity is developed.

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The topic of the thesis is preparation of ferroelectric and dielectric composite materials, particularly the work deals with the preparation of barium strontium titanate. In the theoretical part the possibilities of BST synthesis and its processing are described. The experimental part deals with precipitation synthesis of barium strontium titanate. Prepared powders were characterized in terms of morphology and phase composition. Further, pressureless sintering and hot isostatic pressing (HIP) were used for preparation of dense ceramics. Pure BST powders, that were formed and sintered, were prepared by sol-gel precipitation synthesis. The highest density was reached by slow sintering cycle (slow increase of temperature and delay during sintering) and sintering by HIP.

Final publication is available at http://link.springer.com/article/10.1007%2Fs10856-015-5612-2 / 京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19566号 / 医博第4073号 / 新制||医||1013(附属図書館) / 32602 / 京都大学大学院医学研究科医学専攻 / (主査)教授 安達 泰治, 教授 戸口田 淳也, 教授 鈴木 茂彦 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Barium Strontium Titanate (BST) was deposited on Pt/ZrO2 / SiO2/Si substrates using liquid source metal organic chemical vapor deposition. A stoichiometry series was deposited with various GrII/Ti ratios (0.658 to 1.022) and a temperature series was deposited at 550 to 700°C. The thin films were characterized using transmission electron microscopy. Both series of samples contained cubic perovskite BST and an amorphous phase. The grain size increased and the volume fraction of amorphous phase decreased with increasing deposition temperature. The electrical and microstructural properties improved as the GrII/Ti ratio approached 1 and deteriorated beyond 1. This research demonstrates that BST thin films are a strong candidate for future MOS transistor gate insulator applications.

No description available.