Orientador: Adriano Alves dos Reis / Coorientadora: Polyana Alves Radi Gonçalves / Banca: Marcos Yutaka Shiino / Banca: Maria Margareth da Silva / Resumo: Embora o titânio e suas ligas sejam amplamente utilizados como materiais de implante, estudos para acelerar a osseointegração têm sido realizados. Uma das técnicas em estudo é o tratamento alcalino e térmico. Este trabalho tem como objetivo avaliar a formação de uma superfície bioativa em titânio comercialmente puro grau 4 após tratamento alcalino e térmico a 600 °C e 900 °C. Técnicas de caracterização via MEV, AFM, Raman, DRX, molhabilidade, nanoindentação e aderência à indentação foram realizadas para avaliar modificações superficiais e na seção transversal além disso, teste in vitro via imersão em SBF (fluido corporal simulado) para avaliar o crescimento de apatita. O tratamento alcalino formou hidrogenotitanato de sódio (1 µm de espessura) e o tratamento alcalino e térmico formou titanato de sódio (1 µm de espessura), enquanto o rutilo (TiO2) aumentou com o aumento da temperatura do tratamento, atingindo até 5 µm de espessura. A superfície passou de ligeiramente hidrofílica para totalmente hidrofílica. A rugosidade e a área de superfície aumentaram, especialmente em tratamento alcalino e térmico a 900 °C. A dureza da camada superficial aumentou significativamente com o tratamento térmico, e a aderência da indentação mostrou que o tratamento alcalino e térmico a 900 °C apresenta maior delaminação da superfície. Testes in vitro confirmaram que o tratamento alcalino e térmico acelera o crescimento da apatita, mas que o tratamento alcalino e térmico a 600 °C é o tratamento qu... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Although titanium and its alloys are widely used as implant materials, studies for rapid osseointegration have been performed. One of the techniques currently in study is the alkali and heat treatment. This work aims to evaluate the formation of a bioactive surface in titanium commercially pure grade 4 after alkali and heat treatment at 600 °C and 900 °C. Characterization techniques via SEM, AFM, Raman, XRD, wettability, nanoindentation and indentation adhesion were performed to evaluate surface and cross sectional modifications. In addition, in vitro test via SBF (simulated body fluid) soaking was performed to evaluate apatite growth. Alkaline treatment formed sodium hydrogen titanate (1 μm thick), and alkali and heat treatment formed sodium titanate (1 μm thick), while rutile TiO2 increased with increasing treatment temperature, reaching up to 5 μm thick. The surface went from slightly hydrophilic to fully hydrophilic. Roughness and surface area increased, especially in alkali and heat treatment at 900 °C. The hardness of the surface layer was significantly increased by the heat treatment, and the indentation adhesion showed that the alkali and heat treatment at 900 °C presented higher surface delamination. In vitro tests have confirmed that alkali and heat treatment accelerate apatite growth, but that alkali and heat treatment at 600 ° C is the treatment that has the highest mechanical strength and is best suited to accelerate osseointegration. / Mestre

Recentemente, observamos na comunidade científica o despertar de um interesse pelo estudo de lantanídeos com base em titânio; neste ínterim, as amostras Sm2Ti2O7 e Nd2Ti2O7 se destacam por terem sido pouco exploradas, especialmente a baixas temperaturas. Análises cristalográficas de monocristais de Sm2Ti2O7 e Nd2Ti2O7 nos permitiram confirmar inicialmente características de rede como a geometria cúbica e monoclínica, respectivamente, enquanto as análises magnéticas e calorimétricas forneceram a temperatura de transição, até então inédita no caso do Nd2Ti2O7 (aproximadamente T=0,62K), além de ordenamento do tipo antiferromagnético e presença de anisotropia a altas temperaturas, na amostra de Sm2Ti2O7, e por toda a extensão de temperaturas trabalhadas, na amostra de Nd2Ti2O7. Por fim, identificamos também a entropia esperada para spins do tipo Ising em ambas as amostras. / Recently the scientific community has shown interest for titanium lanthanides, with the titanates Sm2Ti2O7 and Nd2Ti2O7 being poorly approached, specially at low temperatures. Crystallographic analysis were performed on the single crystal samples of Sm2Ti2O7 and Nd2Ti2O7, which allowed us to confirm its expected cubic and monoclinic structures, respectively; Magnetic and calorimetric data displayed the transition temperature, not previously seen in case of Nd2Ti2O7, of T=0.35K and T=0.62K, respectively, and the antiferromagnetic behaviour of both samples; Anisotropy was observed at high temperatures on the Sm2Ti2O7 data and along all the temperature range studied for the Nd2Ti2O7 sample. Finally, we have identified the entropy of Ising spins on both samples.

CaCu3Ti4O12 (CCTO), an unusual perovskite-like material, is known for extraordinarily high (often reaching 104) and relatively frequency independent dielectric constant. Recently, it has drawn a lot of attention, because of its potential applications in microelectronics and microwave devices. / In this investigation, CCTO powders were synthesized by two routes, a conventional solid-state reaction and a wet-chemistry method. Three kinds of materials, polyvinyl alcohol (PVA, an organic binder), boric oxide (B 2O3, a well-known glass former), hafnium oxide (HfO 2, a material with high dielectric constant ∼25), were added to the pre-reacted CCTO powder and sintered into ceramics. The effects of these additives on the microstructures, or electric and dielectric properties of CCTO ceramics were investigated. In addition, CCTO thin films were also successfully prepared. The AC conductivity, impedance, and complex dielectric permittivity were used to analyze the data. These observations were well explained in terms of an internal barrier layer capacitor (IBLC) model with Maxwell-Wagner (MW) dielectric relaxation. / Yuan, Wenxiang = 高介電常數材料CaCu₃Ti₄O₁₂χχχ / 苑文香. / Adviser: S.K. Hark. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Yuan, Wenxiang = Gao jie dian chang shu cai liao CaCu₃Ti₄O₁₂ de yan jiu / Yuan Wenxiang.

Recentemente, observamos na comunidade científica o despertar de um interesse pelo estudo de lantanídeos com base em titânio; neste ínterim, as amostras Sm2Ti2O7 e Nd2Ti2O7 se destacam por terem sido pouco exploradas, especialmente a baixas temperaturas. Análises cristalográficas de monocristais de Sm2Ti2O7 e Nd2Ti2O7 nos permitiram confirmar inicialmente características de rede como a geometria cúbica e monoclínica, respectivamente, enquanto as análises magnéticas e calorimétricas forneceram a temperatura de transição, até então inédita no caso do Nd2Ti2O7 (aproximadamente T=0,62K), além de ordenamento do tipo antiferromagnético e presença de anisotropia a altas temperaturas, na amostra de Sm2Ti2O7, e por toda a extensão de temperaturas trabalhadas, na amostra de Nd2Ti2O7. Por fim, identificamos também a entropia esperada para spins do tipo Ising em ambas as amostras. / Recently the scientific community has shown interest for titanium lanthanides, with the titanates Sm2Ti2O7 and Nd2Ti2O7 being poorly approached, specially at low temperatures. Crystallographic analysis were performed on the single crystal samples of Sm2Ti2O7 and Nd2Ti2O7, which allowed us to confirm its expected cubic and monoclinic structures, respectively; Magnetic and calorimetric data displayed the transition temperature, not previously seen in case of Nd2Ti2O7, of T=0.35K and T=0.62K, respectively, and the antiferromagnetic behaviour of both samples; Anisotropy was observed at high temperatures on the Sm2Ti2O7 data and along all the temperature range studied for the Nd2Ti2O7 sample. Finally, we have identified the entropy of Ising spins on both samples.

Thesis (Ph.D.) - University of St Andrews, March 2008. / Restricted until 14th March 2009.

Submitted by MARCIA ROVADOSCHI (marciar@unifra.br) on 2018-08-16T18:59:45Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_JoseFranciscoZavagliaMarques.pdf: 2049396 bytes, checksum: 211f0a7be1dce3b826d2fc80c01e126e (MD5) / Made available in DSpace on 2018-08-16T18:59:45Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_JoseFranciscoZavagliaMarques.pdf: 2049396 bytes, checksum: 211f0a7be1dce3b826d2fc80c01e126e (MD5) Previous issue date: 2014-03-27 / The photocatalytic and photoelectrochemical degradation of Rhodamine 6G dye was studied using TiO2 , TiO2 doped with N , TiO2 thin films prepared by thermal decomposition of polymeric precursors and titanates prepared by hydrothermal synthesis method. The materials synthesized by thermal decomposition of polymeric precursor method were heat-treated at 450 ° C and in the hydrothermal synthesis TiO2 in anatase phase in 40 g / L NaOH at 20 bar was thermally treated at 200 ° C. The obtained compounds were characterized by X- ray diffraction, nitrogen adsorption using the BET method and the morphology was observed by using atomic force microscopy and scanning electron microscopy. The results demonstrate that the obtaining nanostructures are titanium dioxide in the pure anatase phase and titanates, with specific areas ranging from 45 to 63 m2/g for TiO2 and 120 to 510 m2/g for titanates. Adsorption tests were performed to determine the equilibrium parameters and with the photocatalytic tests the kinetic parameters were determined. The adsorption capacity was correlated with the specific area and TiO2 in the anatase phase exhibits the higher efficiency for dye degradation and in removal of total organic carbon. The galvanostatic method with the TiO2 electrode illuminated with UV radiation shows higher degradation rate and higher removal of total organic carbon. / Neste trabalho foi estudada a degradação fotocatalítica e fotoeletroquímica do corante rodamina 6G utilizando TiO2, TiO2 dopado com N, filmes finos de TiO2 preparados pelo método da decomposição térmica de precursores poliméricos e titanatos preparados por síntese hidrotermal. Os materiais sintetizados pelo método da decomposição térmica de precursores poliméricos foram tratados termicamente a 450 °C e na síntese hidrotermal o TiO2 anatase foi tratado em meio de NaOH 40 g/L a 20 bar e 200 °C. Os compostos obtidos foram caracterizados por difração de raios-X, adsorção de nitrogênio pelo método BET e a morfologia foi observada por microscopia de força atômica e microscopia eletrônica de varredura. Os resultados comprovam a obtenção de nanoestruturas de dióxido de titânio na fase anatase pura e titanatos, com áreas específicas variando entre 45 a 63 m2/g para o TiO2 e 120 a 510 m2/g para os titanatos. Foram realizados testes de adsorção com a determinação dos parâmetros de equilíbrio e testes fotocatalíticos com a determinação dos parâmetros cinéticos. A capacidade de adsorção esta correlacionada com a área específica e TiO2 na fase anatase puro apresentou maior eficiência na degradação do corante e na remoção do carbono orgânico total. O processo galvanostático com o eletrodo de TiO2 iluminado com radiação UV mostrou maior velocidade de degradação do corante e maior remoção do carbono orgânico total.

ZnO and ZnO-TiO2 ceramics have intriguing electronic and mechanical properties and find applications in many fields. Many of these properties and applications rely on the understanding of defects and defect processes in these oxides as these defects control the electronic, catalytic and mechanical behaviors. The goal of this dissertation is to systematically study the defects and defects behaviors in Wurtzite ZnO and Ilmenite ZnTiO3 by using first principles calculations and classical simulations employing empirical potentials. Firstly, the behavior of intrinsic and extrinsic point defects in ZnO and ZnTiO3 ceramics were investigated. Secondly, the effect of different surface absorbents and surface defects on the workfunction of ZnO were studied using DFT calculations. The results show that increasing the surface coverage of hydrocarbons decreased the workfunction. Lastly, the stacking fault behaviors on ilmenite ZnTiO3 were investigated by calculating the Generalized Stacking Fault (GSF) energies using density functional theory based first principles calculations and classical calculations employing effective partial charge inter-atomic potentials. The gamma-surfaces of two low energy surfaces, (110) and (104), of ZnTiO3 were fully mapped and, together with other analysis such as ideal shear stress calculations.

The purpose of this study was two-fold: firstly, the MOCVD deposition behavior of Pb(thd)2 was studied in detail and a one-dimensional kinetic model was proposed to successfully predict the effect of processing conditions on the deposition rate profile for PbO. Assuming the surface reaction is the rate-limiting step in the process, the effective activation energy for the process, Ea, was found to be 82 kJ/mol while the preexponential rate constant was found to be 33 g/cm2/min (0.15 moVcm2/min). The process was found to consistently produce a combination of the high temperature, orthorhombic modification of lead monoxide with randomly oriented plates of tetragonal lead monoxide. TEM electron diffraction was used to investigate the crystal orientation of the individual plates which was found to be in the plane normal to the <201> zone. Secondly, the deposition behavior of PbTi03 and the resulting film structure and properties were investigated. Pb(thd)2 was used in conjunction with titanium ethoxide (Ti(OEt)4) as a titanium source. Stoichiometric lead titanate films which were found to be smooth, specular and transparent, and well-adhered were deposited on a variety of substrates by careful control of the experimental conditions. Film structure, composition, and thickness were studied and correlated to changes in various experimental parameters. Additionally, a high temperature regime at which the film stoichiometry is relatively insensitive to experimental conditions was found to occur. The effects of post-annealing on the as-deposited films including compositional changes, morphological changes and crystal structure was also studied. Some problems were obtained with film peeling on the ruthenium oxide (Ru0₂)-coated substrates which could be alleviated somewhat by the use of (100) oriented silicon wafer rather than (111) oriented silicon; a possible mechanism to explain this behavior is also suggested. Optical properties were obtained using UV -VISNIR transmission and reflectance spectroscopy; the ferroelectric hysteresis behavior of the films was observed using standard R T -66 A test equipment. / Master of Science

Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Description based on contents viewed May 30, 2008; title from title screen. Includes bibliographical references (p. 50-51).

Les oxydes de métaux de transition (Ti, Fe, Mn, Cu, etc) présentent une multitude de fonctionnalités tout en cristallisant dans un nombre réduit de structures. C’est le cas par exemple dans la famille des pérovskites qui arborent de nombreux ordres électroniques (isolants, métaux, supraconducteurs) et magnétiques (ferro- et antiferromagnétiques). La compatibilité structurale de ces différents composés permet de les combiner au sein d'hétérostructures multifonctionnelles mais aussi, dans certains cas, de faire émerger de nouvelles propriétés aux interfaces. Un exemple typique découvert en 2004 est celui du gaz électronique bidimensionnel se formant à l'interface entre deux isolants de bande, LaAlO₃ et SrTiO₃ .S’inspirant de ce résultat majeur, ce travail de thèse a pour but de générer de nouvelles phases électroniques et magnétiques aux interfaces, non à partir d'isolants de bande mais d'isolants de Mott et d'isolants à transfert de charge. A l'interface entre ces deux types de composés, l’alignement de bande est rendu plus complexe par la présence de fortes corrélations électroniques.Ainsi, les reconstructions d’interface peuvent donner lieu à une déstabilisation de l'état fondamental, et à la génération de nouvelles phases magnétiques, conductrices ou supraconductrices absentes du diagramme de phase du matériau massif.Dans un premier temps, lors de ce travail nous avons synthétisé, par ablation laser pulsé des couches minces d'isolants de Mott, les titanates de terre-rare (RTiO₃ ). Nous avons caractérisé leurs propriétés magnétiques, optiques et électroniques.Dans un second temps, nous avons également optimisé des couches minces d’isolants à transfert de charge, les nickelates de terre-rare (RNiO₃ ). Nous avons étudié en détail l’effet du rayon ionique de la terre-rare sur la structure électronique à basse température de ces composés.Le cœur de ce travail de thèse a été l'étude des propriétés de l’interface formée par ces deux constituants via une combinaison de plusieurs techniques de spectroscopie (absorption de rayonnement synchrotron, XAS, dichroïsme linéaire et circulaire, XMCD, et spectroscopie de perte d’énergie, STEM-EELS) en lien avec des calculs ab-initio.Après avoir démontré l’apparition d’une nouvelle phase ferromagnétique dans les nickelates, nous discutons du rôle des corrélations dans les nickelates sur le transfert de charge et sur la reconstruction magnétique, observés à l’interface avec GdTiO₃ .Enfin, nous mettons en évidence la possibilité d’utiliser un paramètre de contrôle externe comme la lumière pour altérer le niveau de covalence dans les nickelates sans modifier la terre-rare. Ces résultats ouvrent la voie à de nouveaux dispositifs tirant partie du contrôle actif du niveau de covalence dans les isolants à transfert de charge. / Transition metal oxides (Ti, Fe, Mn, Cu, etc.) display a multitude of features while crystallizing in a reduced number of structures. This is the case for example of perovskites which exhibit many electronic (insulators, metals, superconductors) and magnetic (ferro- and antiferromagnetic) orders. Their structural compatibility offers a unique playground for combining them in the search for new interfacial properties. A typical example discovered in 2004 is LaAlO₃ and SrTiO₃ whose interface reveals a high-mobility electron gas although the parent constituents are two conventional band insulators.Following-up on this major achievement, this thesis aims at generating new electronic interfacial phases, not from band insulators but rather from Mott and charge transfer insulators. At the interface between these types of compounds, band alignment is made more complex by the presence of strong correlations between electrons.Hence, interfacial reconstructions can destabilize the ground state, and generate new phases absent from the phase diagrams of the two building blocks.Initially, we synthetized, by pulsed laser deposition, a typical Mott insulator, rare earth titanates (RTiO₃ ) in the form of thin layers, which were optimized and characterized on different substrates.Secondly, we also grew charge transfer insulators, rare earth nickelates (RNiO₃ ). We specifically studied the effect of the ionic radius of the rare earth on the electronic structure of these compounds at low temperature.The core of this thesis is to study the interface formed by these two constituents via a combination of spectroscopic techniques (synchrotron radiation-based absorption, XAS, linear and circular dichroism XMCD and energy loss spectroscopy, STEM-EELS) in connection with ab-initio calculations.After demonstrating the emergence of a new ferromagnetic phase in nickelates, absent of the bulk phase diagram, we discuss in particular the role of correlations in nickelates on the charge transfer and magnetic reconstruction, observed at the interface with GdTiO₃ .Finally, we will propose a new external knob, light, to alter the level of covalence in nickelates without changing the rare earth. These results open the way for new devices taking advantage of the active control of the level of covalence in charge transfer insulators.