京都大学 / 新制・論文博士 / 博士(理学) / 乙第13460号 / 論理博第1577号 / 新制||理||1683(附属図書館) / (主査)教授 北川 宏, 教授 吉村 一良, 教授 竹腰 清乃理 / 学位規則第4条第2項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23508号 / 工博第4920号 / 新制||工||1768(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 乾 晴行, 教授 安田 秀幸, 教授 辻 伸泰 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Ce travail de recherche porte sur l'étude d'un nouveau matériau issu de la combinaison de deux oxydes perovskites ferroélectriques Sr2Ta2O7 et La2Ti2O7 ; la solution solide résultante est formulée selon (Sr2Ta2O7)100 x(La2Ti2O7)x (STLTO). Notre étude comprend la synthèse de poudres, la réalisation de céramiques, le dépôt de films minces et leur caractérisation structurale, morphologique, élémentaire, optique, diélectrique et ferroélectrique. L'objectif visé à moyen terme pour ce matériau est son intégration dans des dispositifs hyperfréquences miniatures et reconfigurables. Pour cela, sont recherchées des permittivités élevées, variables sous champ électrique, afin d'atteindre une accordabilité du matériau, puis une reconfigurabilité en fréquence des antennes, par exemple. L'analyse structurale par diffraction des rayons X a confirmé, par la variation linéaire des paramètres de maille, la formation de la solution solide pour les compositions x ∊ [0-5]. Les analyses diélectriques menées à basses fréquences (1 100 kHz) sur les céramiques STLTO ont montré des valeurs maximales de permittivité (375) et d'accordabilité (55 % à 3 kV/mm), associées à des tangentes de pertes faibles (0,01), pour la composition x = 1,65. Les mesures en hautes fréquences (200 MHz – 18 GHz) sont en accord avec les résultats obtenus en basses fréquences. Le dépôt de films minces par pulvérisation cathodique réactive, réalisé à partir d'une cible de composition x = 1,65, produit des films s'apparentant à la phase Sr2,83Ta5O15, ce qui dénote une perte en strontium. Cependant, à basses fréquences, les films présentent des permittivités relativement élevées (130) pour des pertes faibles (0,01) avec une accordabilité modérée (A = 14,5% à 340 kV/cm à f =100 kHz). Le dépôt de films minces oxynitrures (Sr,La)(Ta,Ti)O2N, réalisé en atmosphère réactive Ar + N2, mènent à des échantillons colorés ayant des permittivités élevées (jusqu'à 3000 environ), mais avec des pertes également élevées (jusqu'à 2) et sans accordabilité. Par ailleurs, l'étude de films SrTaO2N a montré que ces composés sont adaptés pour la décomposition de l'eau sous lumière visible. / This research focuses on the study of a new material resulting from the combination of two ferroelectric perovskite oxides Sr2Ta2O7 and La2Ti2O7; the resulting solid solution is formulating according to (Sr2Ta2O7)100 x(La2Ti2O7)x (STLTO). Our study includes the synthesis of powders, the realization of ceramics, thin film deposition and their structural, morphological, elemental, optical, dielectric and ferroelectric characterizations. The medium-term objective for this material is its integration into miniature and reconfigurable microwave devices. For this, high permittivity, variable under electric field, is required in order to achieve a tunability of the material, then a reconfigurability of the antennas, for example. Structural analysis by X-ray diffraction confirmed, by the linear variation of the cell parameters, the formation of the solid solution for the compositions x ∊ [0-5]. The dielectric analyzes carried out at low frequencies (1 - 100 kHz) on STLTO ceramics showed maximum values of permittivity (375) and tunability (55% at 3 kV/cm), associated with weak loss tangents (0,01), for the composition x = 1.65. The measurements at high frequencies (200 MHz – 18 GHz) are in agreement with the results obtained at low frequencies. The deposition of thin film by reactive sputtering, made from a target of composition x = 1.65, produces films similar at Sr2.83Ta5O15 phase, which denotes a loss of strontium. However, at low frequencies, the films have relatively high permittivity (130) for low losses (0.01) with moderate tunability (A= 14.5% at 340 kV/cm at f = 100 kHz). Deposition of oxynitride thin film (Sr,La)(Ta,Ti)O2N, carried out in Ar + N2 reactive atmosphere, leads to coloured samples having high permittivity (up to about 3000), but with equally high losses (up to 2) and without tunability. Moreover, the study of SrTaO2N showed that these compounds are suitable for the decomposition of water under visible light.

Systematic synthetic investigations of the quaternary systems Ag - Bi - Q - X (Q = S, Se; X = Cl, Br) led to a variety of quaternary phases that exhibit considerable structural diversity with increasing complexity. These include Ag1.2Bi17.6S23Cl8, AgBi4Se5Br3 and numerous members of the homologous double series Agx(N+1)Bi2+(1-x)(N+1)Q2+(2-2x)(N+1)X2+(2x-1)(N+1) denoted (N, x)P. N represents the order number of a given homologue and x is the degree of substitution of Bi by Ag with 1/2 <= x <= 1. Their structures are built up from two alternating types of modules denoted A and B that are stacked parallel to (001). In module A, rows of edge-sharing [MZ6] octahedra (Z = X and/or Q); M = Ag and/or Bi) running parallel to [010] alternate along [100] with parallel chains of paired monocapped trigonal prisms around Bi atoms. The module type denoted B represents NaCl-type fragments of varying thickness. It is defined by the number N of octahedra within the chain of edge-sharing octahedra running diagonally across it in the (010) plane of the structure. The thickness of module B for current members of the series extends from N = 0 to N = 7. All structures exhibit Ag/Bi disorder in octahedrally coordinated metal positions and Q/X (Q = S, Se; X = Cl, Br) mixed occupation of some anion positions. Some of these compounds are narrow gap semiconductors.

<p>Commercial alloys are continuously developed to improve their performance. Therefore it is important to develop new optimisation software, which could be used in development of new materials or in materials selection. In this study the mechanical properties which are important in materials selection in mechanical design are investigated. Two types of materials are analysed, aluminium alloys and stainless steels but focus will be on the aluminium alloys.</p><p>Thermodynamic analysis has been used to evaluate the effect of the microstructure. Solid solution hardening has been successfully modelled for both aluminium alloys and stainless steels and follows the theories by Labusch and Nabarro. The precipitation hardening is most dominant for the hardenable aluminium alloys, but the non-hardenable alloys also increase their strength from precipitation hardening. The non-hardenable alloys are divided into tempers, which differ in the amount of strain hardening. This has also been modelled successfully.</p><p>Combining these fundamental results with multiple regression, models for mechanical properties have been created. Separate models are developed for wrought aluminium alloys and stainless steels. For the aluminium alloys this includes the solid solution hardening and the precipitation hardening. For the stainless steels the thickness, nitrogen content and ferrite content are included together with the solid solution hardening.</p>

In der vorliegenden Arbeit wird dargestellt, wie sich mit Methoden der nuklearen Festkörperphysik Defekte und Deformationen selbst in kristallographisch komplexen Materialien wie den MAX-Phasen, einer Klasse von Komplexcarbiden bzw. -nitriden, in-situ nachweisen lassen. Die sensitive Messgröße bildet dabei der elektrische Feldgradient (EFG), der ein Maß für die Asymmetrie der den jeweiligen Sondenkern umgebenden Ladungsverteilung darstellt. Es werden zwei Wechselwirkungsmechanismen zwischen Defekt und EFG diskutiert: Einerseits die langreichweitigen Auswirkungen elastischer Verzerrungen, andererseits der direkte Einfluss eines Defektes auf seine lokale elektronische Umgebung. Die Bestimmung der elastischen Antwort des Feldgradienten erfolgt mittels Ab-initio-Methoden im Rahmen der Dichtefunktionaltheorie. Der dabei vorgestellte Ansatz erlaubt es, die Ursachen der Dehnungsabhängigkeit zu klären und andere, speziellere Dehnungsabhängigkeiten wie die Volumenabhängigkeit oder die Strukturabhängigkeit des Feldgradienten zu bestimmen. Die in der Umgebung bestimmter Defekte oder Deformationen auftretenden EFG-Verteilungen werden anhand der allgemeinen Dehnungsabhängigkeit mittels Monte-Carlo-Simulationen bestimmt. Die so vorhergesagten Verteilungen werden durch ein Experiment im Rahmen der gestörten $\gamma$-$\gamma$-Winkelkorrelation (PAC) sichtbar gemacht, indem polykristalline MAX-Phasen unter uniaxialer Last verformt werden. Eine quantitative Auswertung erlaubt es schließlich, Defektdichten in-situ abzuschätzen. Die lokalen Auswirkungen auf den EFG werden anhand verschiedener MAX-Phasen-Mischkristalle systematisch untersucht. Im Zuge dessen wird die Synthese eines bisher unbekannten MAX-Phasen-Mischkristalls, Ti$_2$(Al$_{0,5}$,In$_{0,5}$)C, beschrieben. Die Zugehörigen Gitterkonstanten werden mittels Röntgendiffraktometrie im Rahmen der Rietveld-Methode bestimmt.

Dans le cadre de ce travail, des composés de formulation Ce1−xFexO2−x2 ont été synthétisésà l’aide de deux protocoles : co-précipitation et synthèse assistée par chauffage micro-ondes.L’utilisation de cette dernière a ainsi conduit à l’obtention de nanoparticules de morphologiescubiques ou « bâtonnets » et ceci pour des temps de synthèse relativement courts. L’analysepar diffraction X a montré notamment que le paramètre de maille diminue en fonction de lateneur en fer, x. L’environnement local et le degré d’oxydation du fer ont été analysés parspectroscopies Mössbauer, RPE et XANES mettant ainsi en évidence la présence d’ions Fe3+isolés au sein de sites octaédriques distordus et sous forme de clusters. Une comparaison entreles deux voies de synthèse a montré que des différences apparaissent à l’échelle locale. Lessolutions solides obtenues ont ensuite été caractérisées au cours du traitement thermique etsous différentes atmosphères. Indépendamment de l’atmosphère de recuit, une démixtion dela solution solide intervient pour des températures proches de 600°C. / This work deals with the synthesis and characterization of Ce1−xFexO2−x2 nanoparticles.Two different synthesis routes were used : the coprecipitation technique and the microwaveassisted synthesis route. This later allowed the obtention of controled morphologies such asnanocubic or nanorod particles, characterized by HRTEM. Compared to hydrothermal synthesisroute the time of reaction was limited to one hour. X-Ray Diffraction analysis showedthat the lattice parameter decreases versus the iron content. Local environment and oxidationstate of iron were analyzed by Mössbauer, EPR and XANES spectroscopies showingthe presence of two kinds of iron sites : isolated (distorted) octahedral sites and clusters. Acomparison between both synthesis routes shows clearly the differences at a local scale. Thenanoparticles were then further characterized during annealing and under different atmospheres.The solid solution undergoes a demixtion phenomenon around 600°C which does notdepend on the atmosphere conditions.

Submitted by Maike Costa (maiksebas@gmail.com) on 2016-05-12T13:11:00Z No. of bitstreams: 1 arquivo total.pdf: 5933598 bytes, checksum: f90080e0529915a4c5c37308259bee89 (MD5) / Made available in DSpace on 2016-05-12T13:11:01Z (GMT). No. of bitstreams: 1 arquivo total.pdf: 5933598 bytes, checksum: f90080e0529915a4c5c37308259bee89 (MD5) Previous issue date: 2015-03-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Zinc stannate (Zn2SnO4) and zinc titanate (Zn2TiO4) are inverse spineltype oxides and stand out due to their optical, electrical, magnetic, semiconductor and photocatalytic properties. In this work, the two materials were combined in order to obtain a solid solution, Zn2Sn1-xTixO4 (x= 0; 0.25; 0.50; 0.75; 1.0), using the modified-Pechini method, in order to evaluate the influence of the Sn4+ ions substitution by Ti4+ ones in the spinel lattice for application as catalysts in the photodiscoloration of the golden yellow remazol. Catalysts were characterized by the X-ray diffraction (XRD), infrared spectroscopy (IR), ultraviolet-visible spectroscopy (UV-Vis), Raman spectroscopy and surface area measurements (BET). XRD results showed that the materials presented a high long range order when heat treated at 700 °C, using zinc acetate and pH = 1. IR and Raman spectra confirmed the presence of the [TiO6] and [SnO6] octahedra and (ZnO4) tetrahedron. The parameters used in the dye discoloration were: catalyst mass and irradiation times. The results showed that a higher irradiation time provided a better efficiency. Zn2SnO4 presented the best result, with 81 % of discoloration after 4 h of irradiation. As tin was replaced by titanium in the spinel structure, the catalyst efficiency decreased, achieving 37 % for the Zn2TiO4. / O estanato (Zn2SnO4) e o titanato de zinco (Zn2TiO4) são óxidos do tipo espinélio inverso, destacam-se devido a suas propriedades óticas, elétricas, magnéticas, semicondutoras e fotocatalíticas. Nesse trabalho, os dois materiais foram combinados com a finalidade de obter uma solução sólida, Zn2Sn1-xTixO4, (x= 0; 0,25; 0,50; 0,75; 1,0), utilizando o método Pechini modificado, de modo a investigar a influência da substituição dos íons Sn4+ por íons Ti4+ na rede do espinélio para aplicação como catalisadores na fotodescoloração do corante amarelo remazol ouro. Os catalisadores foram caracterizados pelas técnicas de difração de raios-X (DRX), espectroscopia na região do infravermelho (IV), espectroscopia na região do ultravioleta visível (UV-Vis), espectroscopia Raman e medida de área superficial por BET. Os resultados de DRX mostraram que os materiais apresentaram alta organização a longo alcance, quando calcinados a 700 °C, utilizando acetato de zinco e pH 1. Os espectros de IV e Raman confirmaram a presença dos octaedros [ZnO6], [TiO6],[SnO6] e tetraedro (ZnO4). Os parâmetros utilizados na descoloração do corante foram: massa fixa de catalisador e tempos de radiação. Os resultados mostraram que um maior tempo de radiação proporcionou maior eficiência. O Zn2SnO4 apresentou o melhor resultado, com descoloração de 81% após 4 h de radiação. À medida que o estanho foi substituído pelo titânio na estrutura do espinélio, a eficiência do catalisador foi decrescendo, chegando a 37% para o Zn2TiO4.

Orientador: Yoshitaka Gushikem / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T16:49:45Z (GMT). No. of bitstreams: 1 Magosso_HericaAparecida_D.pdf: 835979 bytes, checksum: 2898b43a1168c04ffdef965b55b067fa (MD5) Previous issue date: 2008 / Resumo: Este trabalho reporta a preparação, caracterização e aplicação de novos polímeros íon-trocadores denominados cloreto de 3-n-propil (3-metilpiridínio) silsesquioxano e cloreto de 3-n-propil (4-metilpiridínio) silsesquioxano, obtidos a partir da incorporação de quantidades variáveis de grupos metilpiridínio aos materiais. Os polímeros obtidos se mostraram insolúveis nos solventes mais comuns, inclusive água, o que representou uma vantagem, já que permitiu sua utilização na forma em que foram preparados, sem a necessidade de suportá-los sobre nenhum substrato sólido para serem utilizados. Os espectros de RMN C e infravermelho mostraram que as sínteses foram bem sucedidas. Os resultados de análise termogravimétrica mostraram que os materiais estudados são termicamente estáveis até valores próximos a 500 K, o que representa uma característica interessante dos materiais, já que o processo de regeneração dos mesmos envolve secagem a 373 K sob vácuo. Os polímeros obtidos a partir da incorporação do grupo funcional 3-metilpiridínio, denominados Si3-PicCl-A e Si3-PicCl-B, os quais se diferem somente pela quantidade de grupo funcionais fixados, apresentaram capacidades de troca iônica iguais a 1,91 e 0,90 mmol L, respectivamente, enquanto aqueles obtidos pela incorporação do grupo funcional 4-metilpiridínio, denominados Si4-PicCl-A e Si4-PicCl-B, apresentaram capacidades de troca iônica iguais a 1,46 e 0,81 mmol L, respectivamente. Os polímeros Si3-PicCl-B e Si4-PicCl-B foram usados no processo de adsorção de íons cobre e zinco de solução etanólica e o polímero Si4-PicCl-A foi usado na adsorção de íons mercúrio, cádmio e zinco de solução aquosa. A metodologia de cálculo utilizada para se obter os parâmetros de ajuste das isotermas de adsorção foi baseada no modelo dos centros bidentados fixos. Os resultados de adsorção obtidos mostraram a viabilidade do uso dos polímeros como eficientes materiais adsorventes. O último polímero reportado neste trabalho, denominado Si3-PicCl-A, foi aplicado no desenvolvimento de um sensor amperométrico altamente sensível a nitrito. Os resultados obtidos mostraram a viabilidade da aplicação do material no desenvolvimento de um novo sensor para a aplicação proposta / Abstract: This work reports the preparation, characterization and applications of the new ion-exchanger polymers named 3-n-propyl(3-methylpyridinium) silsesquioxane chloride and 3-n-propyl(4-methyl pyridinium) silsesquioxane chloride prepared by the fixation of different amounts of methylpyridinium groups into the materials. The obtained materials were insoluble in the most common solvents, including water. This property was considered as an advantage since it allowed their use as prepared, without the necessity to be supported on the solid substract surface before using. The C NMR and infrared spectra showed that the syntheses were successfully. Thermogravimetric analysis showed that the obtained materials are thermally very stable up to 500 K, an important characteristic since their regeneration process, after using, includes drying the solid at temperature of 373 K under low pressure. The two obtained materials having as functional group the 3-methylpyridinium ion, named Si3-PicCl-A and Si3-PicCl-B, which differ each other just by the amount of functional groups immobilized, presented ion exchanger capacity equal to 1.91 e 0.90 mmol L, respectively, and those obtained having as functional group the 4-methylpyridinium ion, named Si4-PicCl-A and Si4-PicCl-B, presented ion exchanger capacity equal to 1.46 e 0.81 mmol L, respectively. The materials Si3-PicCl-B and Si4-PicCl-B were used in the adsorption process of copper and zinc ions from ethanol solution and the polymer Si4-PicCl-A was used in the adsorption process of mercury, cadmium and zinc ions from aqueous solution. The calculation methodology used to obtain the fit parameters of the adsorption isotherms was based on the model of fixed bidentate centers. The obtained adsorption results showed the viability of using the polymers as efficient adsorvent materials. The last polymer reported in this work, named Si3-PicCl-A, was applied in the development of a highly sensitive amperometric sensor for nitrite. The obtained results showed the viability of the application of the material in the development of a new sensor for the proposed application / Doutorado / Quimica Inorganica / Doutor em Ciências

En aéronautique, les structures en alliage d’aluminium 2024 sont protégées par un primaire anticorrosion fonctionnalisé par des pigments inhibiteurs permettant une cicatrisation rapide de la surface de l’alliage exposée à l’environnement extérieur lors d’un endommagement mécanique superficiel. Compte tenu de la perte de fonctionnalité des primaires par lessivage, il semble nécessaire d’évaluer les risques d’amorçage de la corrosion. En pratique, il a été envisagé de mettre en place des capteurs dits de « corrosion ».L’objectif de ce travail était de comprendre le fonctionnement d’un capteur censé représenter l’endommagement d’une peinture, dont le concept repose sur la compétition entre l’amorçage de la corrosion d’une surface d’un alliage d’aluminium mis à nu et le relâchement d’inhibiteurs (provenant de la peinture). Le comportement de l’alliage 2024 et de solutions solides (constituant le capteur) a été étudié en milieu chloruré en présence ou non d’inhibiteurs à différentes concentrations. En variant la taille d’électrodes peintes exposées sur leur tranche, on a pu quantifier l’efficacité des inhibiteurs sur ces deux types de matériaux, en détectant l’amorçage de la corrosion ou son inhibition, par mesure de pH de surface. Cette analyse chimique couplée à des observations in situ, a permis de déterminer les étapes limitantes qui définissent la compétition entre corrosion et passivation dans le cas de l’alliage 2024. Ces différentes analyses ont montré que, pour quantifier cette compétition, la cinétique d’amorçage de la corrosion microstructurale constitue un élément clé qui ne peut pas être représenté par la réponse des électrodes du capteur constituées d’une solution solide. L’existence d’une distance maximale entre la source d’inhibiteurs et la zone pouvant être passivée a pu être confirmée par la simulation du transport des espèces inhibitrices qui dépend principalement du régime de lessivage du primaire. / The conventional aircraft paint scheme for corrosion protection of aluminum structures is partly based on application of a primer containing inhibitors. In such coatings, release of the inhibiting species enables fast healing of a bare metal surface after a mechanical damage of the protective layers. Nevertheless, considering possible depletion of inhibitors by uncontrolled leaching, it appears important to estimate the corrosion risk integrating “corrosion” sensors in the structure. The objective of this work was to understand the operating mode of a sensor simulating a damaged paint coating whose concept is based on the competition between the triggering of localized corrosion and the passivation of a bare 2024 alloy. The behavior of this massive alloy and Al-Cu solid solutions (the active metallic slots of the sensor) was studied in chloride solution in presence or not of inhibitor ions at different concentrations.Varying the size of a cut-edge electrode coated on both sides, the effectiveness of these inhibitors was demonstrated detecting the microstructural corrosion triggering or its inhibition, by mapping surface pH. Combining these chemical probing with in situ observations it was possible to confirm the nature of the limiting steps controlling the competition between corrosion and passivation. These analyzes highlighted that to quantify this competition, the triggering of the microstructural corrosion represents a key factor which is not possible to mimic by the response of the solid solutions.The existence of a threshold value for the distance between the inhibitor source and the area to be passivated has been confirmed by simulating the mass transport of inhibiting species which appear to be dependent of the release rate of inhibitors.