O titanato de estrôncio (SrTiO3) possui estrutura cristalina do tipo perovsquita. Materiais com este tipo de estrutura são utilizados para diversas aplicações, tais como, sensores, atuadores, em células a combustível de óxido sólido, entre outros. Devido as suas interessantes propriedades físicas, o SrTiO3 vem sendo intensamente estudado, em especial com a introdução de dopantes. Portanto, neste trabalho foi investigada a influência de diferentes teores de Ca (1; 2,5 e 5% mol) e Pr (0,025; 0,050; 0,075 e 1% mol) na microestrutura e propriedades elétricas e dielétricas do SrTiO3, assim como o material sem aditivos (puro). Os resultados mostram que após a sinterização do SrTiO3 puro, a microestrutura consiste de grãos poligonais com tamanho médio micrométrico, além de texturas lisas e rugosas. A condutividade elétrica das amostras sintetizadas sinterizadas a 1450 e 1500ºC é máxima para 2 horas de patamar. Apenas as amostras de SrTiO3 contendo 1% em mol de Ca apresentam fase única. O tamanho médio de grãos das amostras contendo 1% em mol de Ca é 10,65 ± 0,28 µm e para teores acima deste valor ocorre crescimento significativo dos grãos. As medidas de condutividade elétrica mostraram que as amostras contendo a adição de 1% em mol de Ca possuem maior condutividade dos grãos em relação ao material puro. Para as amostras contendo teores de até 0,075% mol de Pr, pode-se observar alguns grãos lisos e outros rugosos e não há variação considerável do tamanho médio de grãos. As amostras contendo menor teor de Pr (0,025% mol) apresentam maior condutividade dos grãos e contornos de grãos. As amostras de SrTiO3 sintetizado sinterizadas a 1450ºC/10 h apresentaram permissividade elétrica colossal em temperatura ambiente em altas frequências. / Strontium titanate (SrTiO3) exhibits cubic perovskite type crystalline structure at room temperature. Polycrystalline ceramics with this structure are potential candidates for a number of applications including sensors, actuators and in solid oxide fuel cells. Several properties of SrTiO3 are strongly dependent on addition of both donors and acceptors additives. Then, there is a growing interest for studying its properties as a function of type and concentration of additives. In this study, the effects of Ca (1, 2.5 and 5 mol%) and Pr (0.025 to 1 mol%) additions on microstructure and electric and dielectric properties of SrTiO3 were investigated. The microstructure of pure SrTiO3 consists of polygonal grains with average grain size in the micrometer range, and the electric conductivity is maximized after sintering for 2 h at 1450 and 1500ºC. Specimens containing 1 mol% Ca are single phase and the average grain size is 10.65 ± 0.28 µm, but for higher additive contents grain growth is observed. The electric conductivity of SrTiO3 with 1 mol% Ca is higher than that of the pure ceramic. Specimens containing Pr do not show significant grain growth, and the higher conductivity of grains and grain boundaries was achieved with 0.025 mol% Pr. Pure SrTiO3 sintered at 1450ºC for 10 h shows colossal dielectric permittivity (> 1.000) at room temperature, in contrast to specimens prepared with commercial powder (dielectric permittivity = 300), at high frequencies.

The aim of this work has been to use atomistic computer simulation methods to calculate the thermal conductivity and investigate factors that will modify the behaviour when applied to three different oxide materials: MgO, SiO2 and SrTiO3. These were chosen as they represent distinct classes of materials and are substrates for thermoelectric devices, where one of the primary goals is to tailor the system to reduce the thermal conductivity. Chapter 1 introduces thermoelectric concepts, gives a background of the theory and a review of various important thermoelectric materials. In Chapter 2 an overview of the interatomic interactions is presented along with details on the implementation of these interactions in a simulation of a 3D periodic crystal. Chapter 3 outlines the importance of phonon processes in crystals and several approaches to the calculation of thermal conductivity are presented. MgO results are given in Chapter 4. Both the Green-Kubo and Boltzmann transport equation (BTE) methods of calculating thermal conductivity were used. The effect on thermal conductivity of two different grain boundary systems are then compared and finally extended to MgO nanostructures, thus identifying the role of surfaces and complex nanostructure architectures on thermal conductivity. In Chapter 5 two different materials with the formula unit SiO2 are considered. The two materials are quartz and silicalite which show interesting negative thermal expansion behaviour which may impact upon the thermal transport within the material. Chapter 6 presents results on the promising thermoelectric material STO. Once again the results from both Green-Kubo and BTE calculations are compared. Grain boundaries are also studied and the effect of inter-boundary distance and boundary type on the thermal conductivity is explored. Finally, a nanostructured STO system (assembled nanocubes) with promising thermoelectric applications is studied. Chapter 7 outlines the conclusions made from this work and suggests areas for future study.

Conforme pesquisas realizadas na literatura, o estudo do Titanato de Bário (BTO) na dosimetria é inédito, este material foi escolhido porque exibe propriedades luminescentes, demonstradas em experimentos de medidas de espectros de emissão. Para a confecção do BTO fez-se o uso da técnica química Sol-Gel, foi produzido amostras de BTO Puro, BTO dopado e co-dopado com diversas terras-raras. Todas as amostras produzidas sofreram calcinações com temperaturas definidas em 800, 1000 e 1200°C. As dopagens foram realizadas com os seguintes elementos terras-raras: Nd, Tb, Eu, Yb, Er, Pr, e as amostras co-dopadas foram com Tb/Eu e Yb/Er; no total foram confeccionadas trinta e uma amostras. No estudo de redução de massa foi constatada uma redução de metade das massas das amostras durante o processo de calcinação. Nas análises de Termoluminescência (TL) pelo menos uns dos tipos de calcinações apresentaram picos TL, com exceção das amostras co-dopadas com Tb/Eu. As amostras dopadas com Eu e Tb se destacaram nas análises das respostas termoluminescentes. A amostra com Tb e calcinada a 1200°C forneceu pico TL entre 90 a 200°C, e a dopada com Eu (1mol%) e calcinado a 1000°C apresentou picos TL em 110°C e 370°C. A mínima dose detectável para o pico de 110°C foi de 119 mGy e para o pico de 370°C foi de 143 mGy. As análises de MEV mostraram que as micrografias das amostras de BTO dopado tanto com Tb, quanto com Eu apresentaram superfícies porosas, diferentemente das Puras, que apresentaram superfície mais lisa. As análises de DRX indicaram uma fase tetragonal para as amostras Pura e dopadas com Eu (1 mol%), ambas calcinadas a 1000°C. / According to the literature, the study of Barium Titanate (BTO) for dosimetry is unpublished yet, this material was chosen because it exhibits luminescent properties, demonstrated in emission spectra experiments. To make the BTO samples the chemical sol-gel technique was used. Samples of BTO Pure, doped and co-doped with different rare earths were made. All produced samples were calcinated with temperatures at 800, 1000 and 1200°C. The doping was performed with the following rare earths: Nd, Tb, Eu, Yb, Er, Pr, and some samples were co-doped with Tb / Eu and Yb / Er; in total were made thirty-one samples. In the study of weight reduction, a reduction, by half of the mass of raw material, was observed during the calcination process. In the TL analysis, at least one of the types (temperature) of calcinations provides TL peaks formation, except for the samples co-doped with Tb / Eu. The BTO: Eu and Tb provided the best TL response. The BTO: Tb and calcined at 1200°C showed TL peak at 90 to 200°C and the one doped with Eu (1mol%) and calcined at 1000°C supplied peaks at 110°C and 370°C. The minimum detectable dose to the TL peak at 110°C was 119 mGy and for TL peak at 370°C was 143 mGy. SEM analyzes showed that the micrographs of BTO samples doped with both Tb and Eu supplied porous surfaces, unlike the pure sample, that showed smoother surface. XRD analyzes indicated a tetragonal phase to pure sample and the one doped with Eu (1 mol%), both calcined at 1000°C.

Catalysis has an effect on almost every aspect of our lives. They are used to help grow the food we eat, clean the water we drink and produce the fuels our civilisation is so dependent upon. Homogeneous catalysts, those in the same phase as the reaction medium, are highly selective as a result of their tuneable nature, for example through changes to ligands in a metal complex. However, their separation from the reaction medium can become a problematic, costly, non-green issue, overcome through the use of heterogeneous catalysts which can be removed and recycled by simple separation techniques such as filtering and sedimentation. A major limitation on understanding the behaviour of heterogeneous catalysts is the presence of different active sites due to different exposed crystal surface, concentration of defects and morphological variations. With such considerations, the first section of this thesis focuses on the synthesis of discrete and well-defined nanostructured materials (ceria and titanate) using a single-step hydrothermal method. Nanostructured ceria with different morphologies (particles, rods and cubes), present a high oxygen storage capacity and thermal stability. Their oxidation catalytic activity was assessed using CO oxidation as a model reaction as a function of their physical and chemical properties, tuned by morphological control at the nanoscale. An inverse relationship is observed between crystallite size and rates of reaction normalised per surface area. Smaller crystallites present a constrained geometry resulting in a higher concentration of defects, highly active catalytically due to their unsatisfied coordination and high surface energy. The surface to bulk oxygen ratio generally increased as the surface area increased, however, ceria nanorods present a higher surface oxygen content than that which would be predicted according to their surface area, likely due to the selective exposure of the (110) and (100) dominating crystal surfaces presenting more facile oxygen atoms in their surface. Additionally a relationship between surface to bulk oxygen ratios and activation energies was also ascribed to the more facile nature of oxygen atoms on these surfaces and their more readily formed oxygen vacancies as a result. This activity is as a result of the formation of oxygen vacancies being the rate-controlling step. The thermal stability of nanostructured ceria (particles, rods and cubes) was also studied to investigate their performance under cyclic high temperature applications. For this, the materials were pre-treated at 1000 °C under different atmospheres (inert, oxidative and reducing). In all cases, the materials sinter, consequently resulting in a dramatic decrease in surface area. Interestingly, their catalytic activity per surface area towards CO oxidation, seems to be maintained, although those materials pre-treated under inert and oxidising atmospheres became inactive in consecutive catalytic runs. However, nanostructured ceria pre-treated at 1000 °C under hydrogen appeared to maintain its activity per surface area. The presence of hydrogen during thermal treatment does not only facilitate the removal of surface oxygen, but also the bulk oxygen, resulting in a rearrangement of the structure that facilitates its catalytic stability. Titanate nanotubes were shown to be inactive for CO oxidation and thus were used in the second part of this thesis as a support for platinum nanoparticles to study the effect of the structure and metal-support interaction on the resulting catalytic activity. The study focuses on the effect of different loading methods (ion exchange and incipient wetness impregnation) of platinum nanoparticles on the resulting metal particle size, dispersion, metal-support interaction and consequently their resulting catalytic activity. Ion exchange consistently resulted in smaller nanoparticles with a lower dispersion of sizes and more active catalyst, both in terms of turnover frequency values and activation energy, compared with incipient wetness impregnation. The catalytic activity of the platinum supported on titanate nanotubes increases as the metal particle size decreases to a size value (between 1 and 2.5 nm) below which a dramatic decrease in activity is observed. Despite initial differences in catalytic activity between the different catalysts, it was observed that after initial reactions to 400 °C, the activation energy was independent of metal loading weight and was instead inherent of the loading method, suggesting the presence of similar active sites.

Made available in DSpace on 2017-07-21T20:42:44Z (GMT). No. of bitstreams: 1 GUILHERME BACCI.pdf: 2882047 bytes, checksum: 2bf1ae6f64200191aa823e1e72f2a368 (MD5) Previous issue date: 2011-11-28 / Over the years, BaTiO3 has been used in a wide variety of crystal types applications, ceramic structures, multilayer and thin films. Lately, the utilities techniques to obtain BaTiO3 are so diversified and was cited in several works. The picked method for the synthesis of BaTiO3 in this work was the non conventional method called freeze drying, which consist to obtain powders in low temperature. Nanoparticulated powders was produced with pure phase at 973K and characterized as positive temperature coefficient (PTC). / Ao longo dos anos, BaTiO3 tem sido usado numa ampla variedade de aplicações na forma de vários tipos de cristais, estruturas cerâmicas, multicamadas e filmes finos. Recentemente, as técnicas utilizadas pra obtenção do BaTiO3 são muito diversas e foram mencionadas em vários trabalhos. O método selecionado para síntese do BaTiO3 neste trabalho foi o método não convencional chamado liofilização que, são pós obtidos na desidratação dos pós a baixas temperaturas. Foram produzidos pós nanoparticulados com fase pura a 700°C e caracterizados como sensores de temperatura com coeficiente positivo (PTC).

O titanato de estrôncio (SrTiO3) possui estrutura cristalina do tipo perovsquita. Materiais com este tipo de estrutura são utilizados para diversas aplicações, tais como, sensores, atuadores, em células a combustível de óxido sólido, entre outros. Devido as suas interessantes propriedades físicas, o SrTiO3 vem sendo intensamente estudado, em especial com a introdução de dopantes. Portanto, neste trabalho foi investigada a influência de diferentes teores de Ca (1; 2,5 e 5% mol) e Pr (0,025; 0,050; 0,075 e 1% mol) na microestrutura e propriedades elétricas e dielétricas do SrTiO3, assim como o material sem aditivos (puro). Os resultados mostram que após a sinterização do SrTiO3 puro, a microestrutura consiste de grãos poligonais com tamanho médio micrométrico, além de texturas lisas e rugosas. A condutividade elétrica das amostras sintetizadas sinterizadas a 1450 e 1500ºC é máxima para 2 horas de patamar. Apenas as amostras de SrTiO3 contendo 1% em mol de Ca apresentam fase única. O tamanho médio de grãos das amostras contendo 1% em mol de Ca é 10,65 ± 0,28 µm e para teores acima deste valor ocorre crescimento significativo dos grãos. As medidas de condutividade elétrica mostraram que as amostras contendo a adição de 1% em mol de Ca possuem maior condutividade dos grãos em relação ao material puro. Para as amostras contendo teores de até 0,075% mol de Pr, pode-se observar alguns grãos lisos e outros rugosos e não há variação considerável do tamanho médio de grãos. As amostras contendo menor teor de Pr (0,025% mol) apresentam maior condutividade dos grãos e contornos de grãos. As amostras de SrTiO3 sintetizado sinterizadas a 1450ºC/10 h apresentaram permissividade elétrica colossal em temperatura ambiente em altas frequências. / Strontium titanate (SrTiO3) exhibits cubic perovskite type crystalline structure at room temperature. Polycrystalline ceramics with this structure are potential candidates for a number of applications including sensors, actuators and in solid oxide fuel cells. Several properties of SrTiO3 are strongly dependent on addition of both donors and acceptors additives. Then, there is a growing interest for studying its properties as a function of type and concentration of additives. In this study, the effects of Ca (1, 2.5 and 5 mol%) and Pr (0.025 to 1 mol%) additions on microstructure and electric and dielectric properties of SrTiO3 were investigated. The microstructure of pure SrTiO3 consists of polygonal grains with average grain size in the micrometer range, and the electric conductivity is maximized after sintering for 2 h at 1450 and 1500ºC. Specimens containing 1 mol% Ca are single phase and the average grain size is 10.65 ± 0.28 µm, but for higher additive contents grain growth is observed. The electric conductivity of SrTiO3 with 1 mol% Ca is higher than that of the pure ceramic. Specimens containing Pr do not show significant grain growth, and the higher conductivity of grains and grain boundaries was achieved with 0.025 mol% Pr. Pure SrTiO3 sintered at 1450ºC for 10 h shows colossal dielectric permittivity (> 1.000) at room temperature, in contrast to specimens prepared with commercial powder (dielectric permittivity = 300), at high frequencies.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Desde o desenvolvimento da primeira cÃlula solar sensibilizada por corante em 1991, este campo de pesquisa vem crescendo consideravelmente. As nanopartÃculas de TiO2 tÃm sido o principal semicondutor aplicado neste tipo de cÃlula. PorÃm com o advento da nanociÃncia e nanotecnologia, novas estruturas semicondutoras com caracterÃsticas morfolÃgicas variadas tÃm sido bastante investigadas para este tipo de aplicaÃÃo. Nesse trabalho foi obtido nanotubos de titanato de sÃdio (NTT-Na+) com composiÃÃo Na2Ti3O7, a partir do TiO2 comercial, pelo mÃtodo hidrotÃmico em meio altamente alcalino e nanotubos de titanato protonados (NTT-H+) com composiÃÃo H2Ti3O7 a partir da lavagem dos Na2Ti3O7 em soluÃÃo de HCl 0,1 mol/L para realizaÃÃo da troca iÃnica Na+ por H+. Utilizou-se, tanto os produtos Na2Ti3O7 e H2Ti3O7 quanto o material de partida TiO2 em fotoeletrodos de cÃlulas solares sensibilizadas por mesoporfirina. Para isso, algumas lÃminas de vidro para microscopia receberam a aplicaÃÃo de filmes finos de SnO2-F por meio da tÃcnica de spray pirÃlise, adquirindo propriedades condutoras. ApÃs isso, as camadas de TiO2, Na2Ti3O7 e H2Ti3O7 foram depositadas com auxÃlio de um bastÃo de vidro sobre os substratos condutores para servirem como suportes durante a aplicaÃÃo do corante. ApÃs a adsorÃÃo do corante pelas camadas as cÃlulas foram fechadas por meio de um eletrÃlito com par redox (I3-/3I-) utilizando como contra eletrodos, vidros condutores com camadas contendo carbono em suas superfÃcies. As diferentes amostras de vidros condutores apresentaram resistÃncias elÃtricas de 4,66 â 8,66 Ω/□. As camadas de TiO2, Na2Ti3O7 e H2Ti3O7 sobre as lÃminas condutores foram analisadas por diversas tÃcnicas de microscopias e apresentaram, entre outras, caracterÃsticas porosas com superfÃcies bastantes irregulares. Por fim, ao expor as trÃs cÃlulas fotovoltaicas à radiaÃÃo solar de 1258 W/m2 foram verificados corrente elÃtrica de 13 ÂA e tensÃo de 370 mV para a cÃlula com eletrodo de Na2Ti3O7, corrente de 7,6 ÂA e tensÃo de 256 mV para a cÃlula com eletrodo de H2Ti3O7, corrente de 1,1 ÂA e tensÃo de 1,6 mV para a cÃlula com eletrodo de TiO2. / Since the development of the first dye sensitized solar cell in 1991, this field of research has grown considerably. TiO2 nanoparticles have been the main semiconductor on this kind of cell. With the advance in nanoscience and nanotechnology, new semiconductor structures with various morphological characteristics have been deeply studied for this sort of application. In this work, it was chosen to synthesize sodium titanate nanotubes (NTT-Na+) composed of Na2Ti3O7, by using anatase TiO2 associated with the hidrothermic method in high alkaline mean and titanate protonned nanotubes (NTT-H+) composed of H2Ti3O7 obtained by the washing of Na2Ti3O7 in 0,1mol/L HCl solution to perform the ionic trade, Na+ by H+. Both Na2Ti3O7 and H2Ti3O7 were used, as well as TiO2, on solar cell electrodes sensitized by mesoporfirin. In order to do that, some microscopy glass blades received the application of SnO2-F thin films by the use of the spray pyrolyse technique, acquiring conductive properties. After that, layers of TiO2, Na2Ti3O7 and H2Ti3O7 were deposited by using a glass stick over the conductive substrates, to work as support during the dye application. After the dye is adsorbed, the cells were closed using an electrolyte as redox pair (I3-/3I-) and conductive glass with layers of carbon in its surface, as counter electrode. The different samples of conductive glass showed electric resistance of 4,66 â 8,66 Ω/□. The layers of TiO2, Na2Ti3O7 and H2Ti3O7 over the conductive blades were analyzed through several microscopic techniques and presented, amongst others, porous characteristics with very irregular surfaces. While exposing the three photovoltaic devices to solar radiation of 1258 W/mÂ, the following values of current and tension were verified: 13 μA and 370 mV for the cell with Na2Ti3O7 electrode; 7,6 μA and 256 mV for the cell with H2Ti3O7 electrode; 1,1 μA and 1,6 mV for the cell with TiO2 electrode.

Este trabalho, realizado junto ao Grupo de Novos Materiais e Dispositivos (GNMD) pertencente ao Laboratório de Microeletrônica (LME) da Universidade de São Paulo, teve como objetivo correlacionar algumas propriedades físico-químicas de filmes finos de Ba1-XSrxTiO3 (BST), obtidos pela técnica de pulverização catódica reativa (sputtering), com os parâmetros de deposição, visando a fabricação de defasadores inteligentes operando em 60 GHz. Propriedades como cristalinidade e composição química foram estudadas e relacionadas com o tipo de substrato sobre o qual os filmes finos de BST foram depositados, e com os diversos parâmetros de deposição variados. Foi observada uma forte influência dos parâmetros de deposição, principalmente da temperatura e do tipo de substrato, na cristalinidade dos filmes. Os filmes depositados sobre cobre são mais cristalinos do que aqueles depositados sobre Si. Já a composição química dos filmes não variou significativamente, mantendo-se próxima à do alvo de sputtering utilizado, independentemente do substrato ou das condições de deposição. As propriedades elétricas dos filmes fabricados foram extraídas de capacitores de placas paralelas construídos utilizando o BST como dielétrico linear. As curvas de capacitância vs tensão a 1 MHz destes capacitores permitiram determinar uma variação de tunabilidade de até 44 %, para uma permissividade elétrica relativa de 310, valores estes compatíveis com aqueles encontrados na literatura. As propriedades elétricas dos filmes produzidos permitiram projetar um defasador de 1,3 mm2, com uma figura de mérito de 30º/dB para uma defasagem de 360º. / This work, performed at the New Materials and Devices Group (GNMD) of the Microelectronics Laboratory of the Polytechnic School of the University of São Paulo, has the objective to correlate reactive sputtered-BST thin films to its deposition parameters, aiming to produce a 60 GHz tunable phase shifter. Thin film crystallinity and stoichiometry were correlated with sputtering deposition parameters and the type of substrate. A strong influence of the sputtering parameters was observed on BST crystallinity, mainly the temperature and the type of substrate. Thin films on copper are more crystalline than on Si (100). The stoichiometry, on the other hand, did not change as function of the deposition parameters or the substrate in both cases. The thin films electrical properties were obtained by capacitance vs voltage measurements, with the BST as linear dielectric of a parallel plate capacitor. The capacitors 1 MHz C-V characterization showed tunabilities as high as 44%, for an electrical permittivity of 310. These properties allowed a phase shifter project, resulting a 1,3 mm2 device with a figure of merit of 30 º/dB for 360 º phase shift.

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-08-10T15:19:49Z No. of bitstreams: 1 SergioAzevedo.pdf: 3063334 bytes, checksum: ac4355642257682013f550aad3b1a89a (MD5) / Made available in DSpace on 2017-08-10T15:19:49Z (GMT). No. of bitstreams: 1 SergioAzevedo.pdf: 3063334 bytes, checksum: ac4355642257682013f550aad3b1a89a (MD5) Previous issue date: 2015-07-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Strontium titanate, SrTiO3 (ST) is a mixed oxide from the group of perovskites, has a cubic structure and a band gap of 3.2 eV. In this study systems SrTiO3(ST), SrTi0,90Fe0,10O3(STF), Sr0,90Ag0,10TiO3(SAT) and Sr0,95Ag0,05Ti0,90Fe0,10O3(SATF) were synthesized by the Pechini method in which the same, favor the production of nanostructured materials with a high stoichiometric accordingly. The precursors used were titanium isopropoxide, citric acid, strontium nitrate, ferric nitrate, silver nitrate and ethylene glycol. For the formation of the precursor powder, the resin is calcined at 300 °C for 1 hour with a ramp of 10 °C min-1. The precursor powder was characterized by TG/DTA. For the formation of calcined systems we used different temperatures of 400 °C / 500 °C/ 600 °C/ 700 °C/ 2h with a ramp of 10 °C min-1. The sample composition was calcined in ST 550 °C/ 2h to examine the formation of the phase. The samples were characterized by X-Ray Diffraction (XRD) spectroscopy, FTIR, UV-Vis spectroscopy, Raman spectroscopy and B.E.T. the sample STF showed a peak shift DTA higher intensity to lower temperature, resulting in a more rapid decomposition. The x-ray diffractograms show the formation of perovskite phase at low temperature of 600 °C with secondary phase SrCO3 and TiO2, the SAT and SATF samples occurred and formation of metal pranta as a secondary phase. Infrared spectra show that the material exhibits short-range organization and having SrCO3 as a secondary phase. Raman spectra show first order band which is characteristic of tetragonal structure ST. The samples are mesoporous, the substitution Ti / Fe and Sr / Ag promoted the reduction of the surface area of the samples. The addition of iron as a substituent ST caused a reduction of the optical band gap 3.21(2) to 2.31(2) in PBS and 2.16(1) composition in SATF composition. It can be concluded that the method is efficient in the synthesis of structural organization samples with short and long range, using calcination temperatures above 600 °C, and that the substitution by Ti/Fe promotes the reduction of the band gap and the surface area of the ST. / O Titanato de estrôncio, SrTiO3 (ST) é um óxido misto do grupo das perovskitas, apresenta estrutura cúbica e um “band gap” de 3,2 eV. Neste estudo, os sistemas SrTiO3(ST), SrTi0,90Fe0,10O3(STF), Sr0,90Ag0,10TiO3(SAT) e Sr0,95Ag0,05Ti0,90Fe0,10O3(SATF) foram sintetizados pelo método Pechini, o mesmo favorece a obtenção de materiais com alta conformidade estequiométrica. Os precursores utilizados foram: isopropóxido de titânio, ácido cítrico, nitrato de estrôncio, nitrato férrico, nitrato de prata e etileno glicol. Para a formação do pó precursor, calcinou-se a resina a 300ºC por 1 hora com rampa de 10 ºC.min-1. O pó precursor foi caracterizado por TG/DTA. Para a formação dos sistemas calcinados utilizou-se diferentes temperaturas de 400 ºC/500 ºC/600 ºC/700 ºC/2h com rampa de 10 ºC.min-1. A amostra com composição ST foi calcinada em 550 ºC/2h para analisar a formação da fase. As amostras foram caracterizadas por Difração de Raios-X (DRX), Espectroscopia FTIR, Espectroscopia UV-VIS, Espectroscopia Raman e B.E.T. A amostra STF apresentou um deslocamento do pico DTA de maior intensidade, para temperatura menor, resultando em uma decomposição mais rápida. Os difratogramas de Raios-x comprovam a formação da fase perovskita a partir da temperatura de 600ºC, com fase secundaria de SrCO3 e TiO2, nas amostras SAT e SATF ocorreu e formação de pranta metálica como fase secundaria. Os espectros infravermelhos mostram que o material apresenta organização a curto alcance e que apresenta SrCO3 como fase secundária. Os espectros Raman apresentam banda de primeira ordem que é característico da fase tetragonal da estrutura ST. As amostras são mesoporosas, as substituições Ti/Fe e Sr/Ag promoveram a redução da área superficial das amostras. A adição de ferro como substituinte promoveu a redução do band gap óptico do ST de 3,21(2) para 2,31(2) na composição STF e 2,16(1) na composição SATF. Pode se concluir que o método é eficiente na síntese das amostras com organização estrutural a curto e longo alcance, utilizando temperaturas de calcinação acima de 600 ºC, e que a substituição Ti por Fe promove a redução do “band gap” e da área superficial do ST.

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-08-08T14:30:34Z No. of bitstreams: 1 Disserta??o Luisa Alban.pdf: 1572475 bytes, checksum: 51e47c0f80b15d05eda24af2e3b8fde5 (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-08-09T11:13:00Z (GMT) No. of bitstreams: 1 Disserta??o Luisa Alban.pdf: 1572475 bytes, checksum: 51e47c0f80b15d05eda24af2e3b8fde5 (MD5) / Made available in DSpace on 2018-08-09T11:23:16Z (GMT). No. of bitstreams: 1 Disserta??o Luisa Alban.pdf: 1572475 bytes, checksum: 51e47c0f80b15d05eda24af2e3b8fde5 (MD5) Previous issue date: 2018-08-01 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / The interest in nanostructures such as titanate nanotubes (TNTs) has grown notably in recent years due to their biocompatibility and economic viability, which makes them promising for application in the biomedical field. Quercetin (Qc) has been reported to have great potential as a chemopreventive agent widely used in the study of the treatment of diseases such as bladder cancer. Therefore, this work aimed to study the incorporation of quercetin in sodium TNTs (NaTNT) and zinc (ZnTNT), as well as characterize the nanostructures formed. In addition, it was intended to conduct Qc release tests and biological and antitumor activities in T24 lineage cells. The nanostructures of TNTs were synthesized and characterized by FTIR, MEVFEG, EDS, MET DRX and TGA techniques. The results showed that the nanostructures have a tubular structure and the exchange of Na+ ions by Zn2+, as well as the incorporation of quercetin in the structure do not alter this morphology. In addition, the interaction established between Zn and Qc increases the thermal stability of nanostructures. The release test showed that the maximum delivery of Qc occurs after 24h and the presence of Zn controls the release of the flavonoid. Biological assays have shown that the NaTNTQc and ZnTNTQc nanostructures decrease the cellular viability of T24 after 48h in high concentrations. Furthermore, NaTNT, NaTNTQc and ZnTNT reduce the number of T24 lineage cells when combined with irradiation after 48h showing that the combination of nanostructures and ionizing energy is an attractive object of study in the treatment of bladder cancer. / O interesse por nanoestruturas como nanotubos de titanatos (TNTs) tem crescido notavelmente nos ?ltimos anos devido a sua biocompatibilidade e viabilidade econ?mica, o que os tornam promissores para a aplica??o na ?rea biom?dica. A quercetina (Qc) tem sido relatada como tendo grande potencial como agente quimiopreventivo amplamente utilizada no estudo do tratamento de doen?as como c?ncer de bexiga. Neste sentido, este trabalho pretendeu estudar a incorpora??o de quercetina em TNTs de s?dio (NaTNT) e de zinco (ZnTNT), bem como, realizar a caracteriza??o das nanoestruturas formadas. Al?m disso, pretendeu-se conduzir testes de libera??o de Qc e atividades biol?gicas e antitumorais em c?lulas da linhagem T24. As nanoestruturas de TNTs foram sintetizadas e caracterizadas por t?cnicas de FTIR, MEV-FEG, EDS, MET DRX e TGA. Os resultados mostraram que as nanoestruturas apresentam estrutura tubular, e a troca de ?ons Na+ por Zn2+, bem como a incorpora??o de quercetina na estrutura n?o alteram esta morfologia. Al?m disso, a intera??o estabelecida entre o Zn e Qc aumenta a estabilidade t?rmica das nanoestruturas. O ensaio de libera??o mostrou que a entrega m?xima de Qc ocorre ap?s 24h e apresen?a de Zn controla a libera??o do flavonoide para o meio. Os ensaios biol?gicos mostraram que as nanoestruturas NaTNTQc e ZnTNTQc diminuem a viabilidade celular de T24 ap?s 48h em altas concentra??es. Ainda, NaTNT, NaTNTQc e ZnTNT reduzem o n?mero de c?lulas da linhagem T24 quando combinadas com irradia??o ap?s 48h mostrando que a combina??o entre as nanoestruturas e energia ionizante se apresenta como um objeto de estudo atrativo no tratamento de c?ncer de bexiga.