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JOYCE SILVA
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MEMBRANAS ELETROFIADAS DE POLIACRILONITRILA RECOBERTAS COM POLIPIRROL PARA REMOÇÃO DE GLIFOSATO
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Leader : CELSO PINTO DE MELO
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MEMBRES DE LA BANQUE :
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CELSO PINTO DE MELO
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EDUARDO HENRIQUE LAGO FALCAO
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CARLOS THIAGO CANDIDO CUNHA
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Data: 17 janv. 2023
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Afficher le Résumé
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O crescimento populacional e o consequente aumento da demanda por alimentos ocasionaram uma demanda por novas técnicas agrícolas, dentre elas a utilização de agrotóxicos. Em suas diversas formulações, o glifosato é o agrotóxico mais usado mundialmente, apesar dos riscos que oferece à saúde humana e animal e ao meio ambiente. Dentre as tecnologias usadas para a remoção dessas substâncias, a adsorção surge como uma alternativa eficiente e de baixo custo. O objetivo do presente trabalho foi o de preparar membranas de poliacrilonitrila (PAN) recobertas com o polímero condutor polipirrol (PPi), através de uma polimerização química in situ, que se mostrassem eficientes na remoção do agrotóxico glifosato disperso em um meio aquoso. Essas membranas foram caracterizadas através das técnicas de MEV, FTIR, UV-vis, medidas do ponto de carga zero e do ângulo de contato, e ensaio mecânico de tração. Em seguida, foram realizados estudos dos mecanismos de adsorção, pela colocação das membranas, em sistemas individuais, em um meio aquoso contendo glifosato. Com isso, foram analisadas as isotermas de adsorção, e realizados os estudos cinético e termodinâmico correspondentes. Os melhores resultados de remoção foram obtidos para o pH 4,0, quando uma capacidade de adsorção (qe) de aproximadamente 47 mg/g foi alcançada, com o equilíbrio do processo sendo alcançado em 90 minutos. O processo de adsorção se ajustou melhor aos modelos de isoterma de Langmuir e de pseudo-segunda-ordem, o que indica ser ele controlado pelo mecanismo de quimissorção, ou adsorção em monocamada, e é favorecido com a diminuição da temperatura. Os resultados obtidos sugerem que a membrana compósita PAN/PPi é um eficiente agente ativo a ser usado em protocolos para a remoção do glifosato.
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2
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LILLYANE RAISSA BARBOSA DA SILVA
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DEVELOPMENT OF SUSTAINABLE NANOCATALYSTS BASED ON SILVER NANOPARTICLES FOR ORGANIC CHEMISTRY
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Leader : MARIA GORETI CARVALHO PEREIRA
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MEMBRES DE LA BANQUE :
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MARIA GORETI CARVALHO PEREIRA
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ARMANDO JUAN NAVARRO VAZQUEZ
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LAIS ARAUJO SOUZA
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Data: 31 janv. 2023
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Afficher le Résumé
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Materials have been developed and used with specific characteristics that meet the needs of a modern and complex society. Among the types of materials, we have nanomaterials that are within the advanced materials. Among these materials, a group that stands out for its wide range of applications is metallic nanoparticles, such as silver nanoparticles (AgNPs). AgNPs have excellent characteristics, which are responsible for optical, electronic, and antibacterial properties. AgNPs are also efficient nanocatalysts, showing efficiency in several reactions, such as the catalytic reduction of organic pollutants. Thus, this work had as its main objective the synthesis of metallic nanocatalysts based on silver nanoparticles in water, and to evaluate their catalytic activity in the degradation of 4-nitrophenol (4-NF). The AgNPs were prepared in spherical format, through the chemical reduction method using sodium borohydride. As stabilizers, we used polymers: poly 4-styrene sulfonate, polyvinyl alcohol, sodium polyphosphate, and sodium alginate; and minor ligands: ascorbic acid, succinic anhydride, glycine, tyrosine, and sodium citrate. AgNPs were characterized by UV-Vis spectroscopy, dynamic light scattering, Zeta potential, and ICP-OES. The obtained results indicate the formation of silver nanoparticles with spherical morphology, colloidal stability, and good size distribution. The catalytic reduction of 4-NF to 4-aminophenol in the presence of silver nanocatalysts was studied by UV-Vis spectroscopy, in the presence of sodium borohydride. The catalytic studies were performed using different volumes of AgNPs (0.5, 0.25, and 0.1 µL), and the analysis was performed at 0, 5, 15, and 30 min. Complete degradation of 4-NF was observed in less than 30 minutes with all catalysts, and this catalytic efficiency is dependent on the amount of AgNP used. Thus, the AgNPs studied here have the potential to be used as nanocatalysts in the degradation of organic pollutants.
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3
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LUCAS RODRIGUES DE OLIVEIRA
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SYNTHESIS OF PALLADIUM NANOCATALYST SUPPORTED ON GRAPHENE DERIVATIVES FOR HYDROGEN PRODUCTION VIA FORMIC ACID DECOMPOSITION
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Leader : BRAULIO SILVA BARROS
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MEMBRES DE LA BANQUE :
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BRAULIO SILVA BARROS
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EDUARDO PADRON HERNANDEZ
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KLEBER GONCALVES BEZERRA ALVES
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Data: 14 févr. 2023
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Afficher le Résumé
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Hydrogen is considered by many to be the energy vector of the future, capable of playing a significant role in the decarbonization of the world's energy matrix. However, its use still needs to be improved due to the unavailability of more effective and secure storage technologies than commercially available ones. Among the new hydrogen storage and transport technologies under development, organic liquids as molecular hydrogen containers have gained prominence in recent years. In this context, this work aims to develop nanocatalysts based on palladium supported by graphene derivatives and their use in the formic acid (FA) dehydrogenation reaction for hydrogen production. Thus, graphene oxide was previously prepared using the modified Hummers method, followed by functionalization with arginine (GO-ARG) and (3- aminopropyl)triethoxysilane (GO-APTES). These samples were used as supports for palladium nanoparticles originating three catalytic systems, Pd/rGO, Pd/ARG-rGO, and Pd/APTES-rGO, characterized by XRD, FTIR, SEM, and EDS. The results confirmed the obtainment of graphene oxide and the success of the functionalization with arginine and APTES, also indicating that the functionalization provided a better dispersion and control of the size of the palladium nanoparticles later deposited on these supports. Furthermore, according to the data obtained by gas chromatography, the two modified catalysts are 100% selective and completely inhibited the formation of CO. In contrast, the Pd/rGO catalyst showed a larger metallic nanoparticle size, which significantly affected the performance of this system. Thus, among the three evaluated systems, the catalyst modified with arginine presented the best result, producing a total of 78 mL of gas at 45°C (60 minutes of reaction), with an apparent activation energy value of 19.93 Kj.mol-1 and hydrogen production rate equivalent to 65 mL.H2.min-1 .g-1 . In recycling tests, the catalyst showed activity up to the fourth reaction cycle.
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4
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ERILENE GRANGEIRO TELES RIBEIRO
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Synthesis and characterization of tri and tetrabasic lead sulfate and its application in lead-acid accumulators
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Leader : ANDRE GALEMBECK
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MEMBRES DE LA BANQUE :
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ALDO JOSE GORGATTI ZARBIN
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ANDRE GALEMBECK
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EDUARDO HENRIQUE LAGO FALCAO
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Data: 27 févr. 2023
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Afficher le Résumé
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Lead-acid batteries have been used since more than a century in many applications. The longevity of the technology is explained by several factors, including reliability, safety, recyclability and relatively low cost. However, one of the biggest problems is the low energy density, related, partly to the high density of the components (Pb) and partly to the low effective use of the active material. Another problem is related to cycle life, partially related to the degradation of the positive electrode, which occurs both, by corrosion of the current collector and by disaggregation, or shedding of the positive active material. In this sense, improving the use of active material and searching for strategies to hinder the shedding of positive active material turns into increase in efficiency, considering the two aspects mentioned above. The use of additives in the production of positive paste, such as 3BS and 4BS seeds,can improve the durability and increase the effective use of the active material. These are the aspects studied in the present work: the synthesis of 3BS and 4BS and subsequent application as additives in paste preparation, and then the use as the positive electrode of prototypes of lead-acid cells. The synthesisof the additives was achieved by mixing industrially lead oxide with adequate amounts of H2SO4, in aqueous medium, at temperatures up to 100oC. The positive plates containing the additives were used in the manufacture of 2 V prototypes and the results showed an increase in the use of the active material, around 3%, which can be explained, at least in part, by the change in the porosity of the plate. Apparently modest, this improvement may result in a decrease in the use of raw material to produce positive plates, which can reach more than a million reais per year. The reduction of costs is an attribute always welcomed by the industry and justifies the efforts involved in the investigation.
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5
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AMANDA CAROLINE DE OLIVEIRA DINIZ
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PRODUÇÃO E CARACTERIZAÇÃO DE CELULOSE BACTERIANA EM MEIO CONTENDO SUCO DO FRUTO DO MANDACARU (Cereus jamacaru)
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Leader : GLORIA MARIA VINHAS
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MEMBRES DE LA BANQUE :
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GLORIA MARIA VINHAS
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JOSÉ FRANCIELSON QUEIROZ PEREIRA
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YEDA MEDEIROS BASTOS DE ALMEIDA
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Data: 28 févr. 2023
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Afficher le Résumé
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A celulose bacteriana (CB) é um biopolímero promissor para substituição de materiais de origem fóssil devido à sua alta pureza, biocompatibilidade, biodegradabilidade, alta elasticidade, resistência mecânica, alta área de superfície específica e porosidade. No entanto, os custos de produção e a inatividade biológica ainda são desafios para produção em escala industrial. Portanto, investigou-se a polpa do Cereus jamacaru, um fruto da região nordeste, subutilizado e pouco explorado comercialmente, visando identificar um sistema de baixo custo e rico em nutrientes que proporcione a bactéria Komagataeibacter hansenii rendimento e propriedades iguais ou superiores ao meio padrão HS (Hestrim-Schramm). Para tanto, foi realizada inicialmente uma caracterização físico-química da polpa do fruto do mandacaru, que demonstrou as seguintes médias de carboidratos (0,70 mol.mL-1), ácido cítrico (0,51%) e pH (4,31). Visto isso, confeccionou-se por via in situ em condições estáticas os meios com o suco do fruto P60 (60% m/v), P80 (80% m/v), P100 (100% m/v) e o meio padrão HS sobre a mesma quantidade de volume. Após os 15 dias de fermentação as amostras foram secas, caracterizadas e analisadas por espectroscopia na região do infravermelho, difratometria de raios-X, microscopia eletrônica de varredura, análise termogravimétrica e permeabilidade ao vapor de água. Verificou-se que o melhor rendimento e produtividade das membranas secas, foi obtido para as amostras P80 (11,10 ± 0,51 g/L e 0,74 ± 0,04 g. L-1.dia-1) e HS (10,84 ± 0,82 g/L e 0,72 ± 0,05 g. L-1.dia-1), que foram estatisticamente semelhantes, favorecendo a substituição do meio HS por um meio com redução quase total de custo. Todas as amostras apresentaram alta capacidade de retenção de água (≈ 97%). As membranas, apresentaram importantes grupos funcionais pertencentes a estrutura química da celulose do tipo I, o maior percentual de cristalinidade conferiu para P80 (78,05%) o que favoreceu um material termicamente mais estável, confirmado pela sua morfologia fibrilar, e pela permeabilidade com coeficiente de permeação de (1,28 ± 0,11 x 10-10 g s-1m-1Pa). Assim, com bases nos resultados, a CB produzida com o suco do fruto Cereus jamacaru sem adição extra de nutrientes se mostrou promissora, de baixo custo e com potencial a ser explorado em diversas aplicações como na indústria alimentícia, embalagens, cosmético, material adsorvente de contaminantes, entre outros.
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6
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FLÁVIO JOSÉ DE ABREU MOURA
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NEW NANOCOMPOSITES OF SILICA AEROGEL WITH LANTANIDE OXIDES FOR EMISSION OF INTENSE WHITE LIGHT BY UPWARD ENERGY CONVERSION
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Leader : RICARDO LUIZ LONGO
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MEMBRES DE LA BANQUE :
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LEONIS LOURENÇO DA LUZ
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LUÍS ANTÓNIO FERREIRA MARTINS DIAS CARLOS
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OSCAR MANOEL LOUREIRO MALTA
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Data: 10 mars 2023
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Afficher le Résumé
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Several studies with lanthanide oxides have been attempting to develop materials for efficient energy upconversion, due to its innumerous possibilities of applications in the field of photovoltaic energy. These efficient materials will be able to take advantage of a large part of the solar spectrum (infrared) that is lost in conventional photovoltaic panels and convert it into visible light, increasing the efficiency of these panels. Thus, the present work aimed at investigating the influence of a thermal insulating matrix coated with PrO2 and Yb2O3 oxides exposed to a near-infrared (NIR) laser in upconversion processes. The oxides and nanocomposites with silica, SiO2/PrO2 and SiO2/Yb2O3, were synthesized via Pechini method. These materials exhibit intense absorption from the visible to NIR, resulting in high temperatures upon excitation at 980 nm with power densities ranging from 0,5 to 4,5 W cm−2 and emitting very bright white light by thermal irradiation. The steady-state temperatures were estimated by the blackbody (Planck) distribution, which were higher than 2000 K for the SiO2/Yb2O3 hybrids under low pressures. It was also observed that for the SiO2/PrO2 hybrids, the concentration of oxides did not affect the emission intensities, in contrast to the SiO2/Yb2O3 hybrids for which the concentration increase directly affects the rise of the emission intensity for the same excitation power density. In general, the increase in excitation power results in an increase in local temperature and, consequently, the brightness of the broadband emission intensity, ascribed to blackbody emission. For the SiO2/Yb2O3 hybrids, it was observed the formation of micro spheres under irradiation at 980 nm, which could lead to a new synthetic approach to ytterbium oxides. Additional efforts are needed to develop these new materials into efficient thermophotovoltaic applications. However, it was shown that the incorporation of thermal insulating materials with high chemical stability still make viable the process of photoinduced thermal bright emissions.
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7
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ÍTALO MACÊDO GONÇALVES
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SÍNTESE COLOIDAL, CARACTERIZAÇÃO ESTRUTURAL, ÓPTICA E MAGNÉTICA DE NANOPARTÍCULAS DE ÓXIDO DE ZINCO DOPADAS COM METAIS DE TRANSIÇÃO
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Leader : GIOVANNIA ARAUJO DE LIMA PEREIRA
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MEMBRES DE LA BANQUE :
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GIOVANNIA ARAUJO DE LIMA PEREIRA
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EDUARDO PADRON HERNANDEZ
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JOSÉ FERNANDO DAGNONE FIGUEIREDO
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Data: 13 mars 2023
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Afficher le Résumé
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O óxido de zinco (ZnO) é um material semicondutor do tipo n da classe II-VI que vem ganhando destaque nas últimas décadas devido às possibilidades de aplicações nas mais diversas áreas científicas, tais como a fotônica, optoeletrônica, magnetismo e nanomedicina. Nesse contexto, a comunidade científica busca metodologias sintéticas alternativas às já consagradas na literatura, como a síntese por coprecipitação, que enfatizam o uso de solventes orgânicos como meio dispersante, visando maior eficiência, baixo custo e fácil reprodutibilidade. Assim, o presente trabalho propôs um método de síntese via química coloidal em meio aquoso, utilizando sais de cloreto (Zn1− xCoxO-Cl) e de nitrato (Zn1− xCoxO-N) como precursores de zinco e de cobalto à uma fração molar de acordo com a expressão, Zn1− xCoxO (x = 0,05, 0,075, 0,10), e ácido mercaptosuccínico (MSA) como agente estabilizante de superfície para a produção de nanopartículas de óxido de zinco dopadas com cobalto (NPs Co:ZnO) em diferentes concentrações. Os resultados confirmaram a formação de NPs de Co:ZnO a partir de algumas técnicas de caracterização. As propriedades estruturais e composicionais, das nanopartículas de ZnO foram avaliadas a partir da difratometria de raios-X (DRX), espectroscopia de emissão óptica com plasma indutivamente acoplado (ICP-OES), microscopia eletrônica de transmissão (TEM) e microscopia eletrônica de varredura (MEV) acoplada a espectroscopia de raios-X em energia dispersiva (EDS). O tamanho médio obtido para as NPs de Zn1− xCoxO-Cl e Zn1− xCoxO-N ficou na faixa entre 18-8 nm diminuindo com o aumento da concentração de dopante e variando com o tipo de precursor, conforme dados de DRX. As análises por TEM mostraram NPs com morfologias quase-esféricas e as técnicas de ICP-OES e EDS comprovaram, ainda que semi-quantitativamente, a dopagem do ZnO com Co. Estes resultados promissores, sugerem boas perspectivas para o desenvolvimento de novos sistemas nanoestruturados em água de ZnO dopado com metais de transição da primeira série da tabela periódica a partir do uso de diferentes moléculas organossulfuradas como agentes estabilizadores de superfície e da modificação das condições sintéticas (pH, precursores, temperatura de síntese, temperatura de calcinação, etc.) para a obtenção de NPs com tamanhos menores e morfologias bem definidas, visando a otimização das propriedades das NPs para aplicações nanotecnológicas.
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8
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SUELEN CATHERINE FARIAS PEREIRA
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Complex [Eu(mppdOH)3]: from UV radiation dosimeter to molecular thermometer
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Leader : SEVERINO ALVES JUNIOR
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MEMBRES DE LA BANQUE :
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ADELMO SATURNINO DE SOUZA
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MARCELLA AUXILIADORA DE MELO LUCENA
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SEVERINO ALVES JUNIOR
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Data: 27 mars 2023
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Afficher le Résumé
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This work reports the synthesis, characterization, luminescent properties and photo-oxidation chemical reaction of the β-diketonate complex [Eu(mppd)3] (mppd = anion 1,3-Bis-(1-methyl-1H-pyrrol-2-yl) propan-1,3- dionate). In addition, we have investigated the preliminar UV dosimeter and molecular thermometer applications of its photo-oxidized form, [Eu(mppdOH)3]. Initially, the protonated ligand Hmppd (1,3-Bis-(1-methyl-1H-pyrrol-2-yl) propan-1,3-dione) was synthesized from the reaction between N-methylpyrrole and malonyl chloride. The Hmppd was characterized by 1H NMR, thermogravimetric analysis and gas chromatography-mass spectrometry. The complex [Eu(mppd)3] shows photoluminescence in the red region (5D0 7FJ, J = 0, 1, 2, 3 and 4) and undergoes photo-oxidation when exposed to UV radiation at 344 nm, resulting in the intensification of the luminescence of the Eu3+ ion. After 15 minutes of irradiation, the emission intensification reaches a plateau that is maintained for 10 minutes until it starts to fall. Attempts were made to produce luminescent devices by inserting the mppd ligand or the [Eu(mppd)3] complex in a supramolecular matrix of hydrogel and in a polymeric matrix of polyvinylpyrrolidone. However, these procedures have not produced satisfactory results. Furthermore, the photostability of the photo-oxidized complex, [Eu(mppdOH)3], under UV radiation exposure (λirr = 343 nm) was evaluated. The emission intensity had a loss of 80% after 60 minutes of exposure, evidencing its photodegradability. Moreover, the thermometric behavior of the [Eu(mppdOH)3] complex was investigated in the physiological temperature range, 303 to 323 K, using the ratio between the integrated emission intensities of the Eu3+ ion and the ligand (IEu/EiLig) as the thermometric parameter. The activation energy found by the Mott-Seitz model was 4,239 cm-1, assuming, therefore, that the Eu3+ charge transfer band is the main mechanism of luminescence deactivation.
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9
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JULIE ANNE PEREIRA CAVALCANTE
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DESIGN OF A BIOPOLYMER SYSTEM BACTERIAL CELLULOSE MEMBRANE AND MICRONEEDLE WITH METHOTREXATE RELEASE FOR DERMATOLOGICAL APPLICATIONS
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Leader : SEVERINO ALVES JUNIOR
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MEMBRES DE LA BANQUE :
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MARCOS VINICIUS DA SILVA PAULA
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SEVERINO ALVES JUNIOR
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YEDA MEDEIROS BASTOS DE ALMEIDA
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Data: 28 mars 2023
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Afficher le Résumé
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Due to the complexity and high cost of treatment, some dermatological diseases are not treated by patients, as in the case of psoriasis, which affects millions of people around the world. This pathology follows different therapies with medications administered topically, orally and parenterally. However, they have problems in all three forms. And so, transdermal administration of methotrexate, the main drug for psoriasis and other dermatological pathologies, avoids the negative effects of other routes and increases efficacy. Thus, it is important to have a matrix for incorporating the drug, as well as an agent to overcome the corneal barrier of the skin. Thus, in this work, a transdermal delivery system of methotrexate was developed with a biopolymeric matrix of bacterial cellulose membrane, which has been used on a large scale for medical applications due to its relevant properties, and with polymeric microneedles of carboxymethylcellulose, as a physical agent for overcome the skin barrier and the release of the drug by this route is efficient. Analyzes were carried out Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Infrared Spectroscopy (FTIR), Thermogravimetry (TGA), X-Ray Diffraction (DRX), swelling test, mechanical compression test and insertion of in vitro skin, cytotoxicity test and in vitro drug release assay. The incorporation of MTX, by the mechanical method, was successful in the CB/MTX bacterial cellulose membrane, with confirmation from the FTIR, XRD and SEM analyses. The BC membrane incorporated with MTX (BC/MTX) and the complete system (BC/MTX/MN) showed similar thermal stability. The membrane with MTX (BC/MTX) showed satisfactory morphology, with morphological aspects of both materials. The microneedle (MN) showed good mechanical resistance for insertion into the skin and good swelling quality. The BC/MTX/MN system showed controlled release of the drug. Finally, the system produced showed potential for future application in the biomedical sector, with relevant biological properties, such as biocompatibility, mechanical resistance, dissolution and good delivery of the drug to the skin, being a good material for use in different dermatological diseases, with good adhesion and low cost.
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10
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ALESSANDRA DE SOUSA LIMA
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STUDY OF THE INFLUENCE OF THE PARTIAL REPLACEMENT OF FINE AGGREGATE BY GLASS WASTE IN MORTARS
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Leader : NATHALIA BEZERRA DE LIMA
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MEMBRES DE LA BANQUE :
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FELIPE MENDES DA CRUZ
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NATHALIA BEZERRA DE LIMA
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TIAGO FELIPE DE ABREU SANTOS
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Data: 29 mars 2023
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Afficher le Résumé
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In this work, the influence of partial replacement of fine aggregate by glass waste was investigated in the mechanical property of compressive strength in mortars, as well as on the manufacturing stages. Mortars with glass waste substituting sand in the proportions of 10%, 20% and 30% in relation to the proportion adopted between cement and sand were manufactured, as well as mortars without this substitution. For the four cases 6 kg of cement, 2.9 kg of lime, 21 kg of sand and 4 kg of waste glass were used, using a water/cement ratio of 1.3. The compressive strength results revealed that the strength of mortars with glass waste decreased compared to the strength of the reference mortar, at both ages. Despite this decrease, the difference in mechanical behavior was small (< 1 MPa). Although it has caused a slight decrease in mortar strength values, the incorporation of glass waste in the mixtures has promoted a better workability of the mixtures, since the material does not absorb water. Additionally, chemical, structural, and microstructural characterization of the precursor materials and the obtained products was performed. Thus, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and thermogravimetry (TG) analyses were performed. From the XRD analyses it was possible to identify the use of calcitic mortar, as well as the presence of systems such as quartz and hydrated calcium silicates. Through the SEM/EDS results it was possible to notice the good formation of the cement hydration products ettringite and portlandite, and with the thermogravimetric analysis the effect of high temperatures on the mortars. The results also showed that the mortars without glass waste showed the highest compressive strength values when compared to the cases where the sand was replaced by waste. Finally, when evaluating all the different types of mortars produced in this dissertation, the additions of 10% and 20% of glass waste lead to mortars with greater potential for applications in civil construction.
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11
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LARISSA KEROLLAINE MAIA GOMES
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FIBERS OF PBAT WITH CINNAMON OIL PRODUCED BY SOLUTION BLOW SPINNING (SBS) - CHARACTERIZATION AND ANTIMICROBIAL STUDY.
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Leader : YEDA MEDEIROS BASTOS DE ALMEIDA
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MEMBRES DE LA BANQUE :
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EDUARDO HENRIQUE LAGO FALCAO
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ELITON SOUTO DE MEDEIROS
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YEDA MEDEIROS BASTOS DE ALMEIDA
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Data: 24 juil. 2023
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Afficher le Résumé
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The Solution Blow Spinning (SBS) technique is a method that allows obtaining nonwoven mats of polymeric fibers that can be used in various biomedical applications such as scaffolds, dressings, and controlled drug release devices. Considering that cinnamon essential oil (C. Cassia) possesses antimicrobial properties, the aim of the present study was to develop poly(butylene adipate-co-terephthalate) (PBAT) nanofiber mats incorporated with cinnamon essential oil (CE) produced by SBS for their application in controlled release systems. The mats were produced from solutions containing 15% and 20% w/v PBAT in chloroform, and the effects of adding 20% mass of CE on the morphology and structural properties of the obtained mats were studied. The mats were characterized for their morphological properties (by SEM), thermal properties (by TGA and DSC), diffraction properties (by XRD), spectroscopic properties (by FTIR), and antimicrobial properties (by agar diffusion). SEM analysis revealed a cylindrical, smooth, and entangled morphology for all PBAT compositions, with fiber diameters ranging from an average of 242 to 314 nm for pure PBAT mats. After the addition of CE, these average diameters increased, ranging from 323 to 461 nm. CE acted as a plasticizer for PBAT, reducing its glass transition temperature (Tg), melting point (Tm), crystallization temperature (Tc), and crystallinity. XRD patterns of the mats showed that the incorporation of CE was not sufficient to induce any new phase formation in PBAT. FTIR results, with the aid of Principal Component Analysis (PCA), confirmed the presence of CE in the PBAT nanofibers. The nanofibers exhibited antimicrobial activity, with average inhibition zones ranging from 2.6 to 2.1 ± 0.1 mm for Escherichia coli and 1.4 to 1.6 ± 0.2 mm for Staphylococcus aureus.
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12
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DJALMA ALVES DE OLIVEIRA
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THERMAL RESPONSIVE BLENDS FORMED BY POLY(N-VINYLCAPROLACTAM) AND POLYURETHANE
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Leader : CAROLINA LIPPARELLI MORELLI
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MEMBRES DE LA BANQUE :
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JULIANO MARINI
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CAROLINA LIPPARELLI MORELLI
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SEVERINO ALVES JUNIOR
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Data: 26 juil. 2023
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Afficher le Résumé
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Smart polymeric materials capable of responding to external stimuli have great potential for application in the industrial or biomedical area as sensors, electronic devices, packaging, dressings, systems for controlled drug release, support for cell growth, among others. Poly(N- vinylcaprolactam), PNVCL, is a thermoresponsive polymer, whose change from hydrophilic to hydrophobic behavior occurs by changing the temperature, and shows promise due to its non-toxicity, biocompatibility and for having a phase transition temperature of hydrophilic to hydrophobic close to physiological temperature. However, the production of finished products with PNVCL is difficult due to its high mechanical fragility. The improvement of PNVCL properties can be achieved through physical mixing with other polymers, making a polymer blend. In addition, mixing with other polymers also allows changing the phase transition temperatures of PNVCL, which can broaden its application spectrum. In the present work, thermoresponsive plastic films produced by molding in solution from polymeric blends containing different mass proportions of PNVCL and thermoplastic polyurethane (TPU) in the proportions 90/10 70/30 and 50/50, respectively, were made. The films were resistant, flexible and with varied thermal responsiveness depending on the formulated composition. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy by attenuated total reflection (FTIRATR), thermogravimetry (TGA) and differential scanning calorimetry (DSC) analysis confirmed the miscibility of the blends formed and the angle analysis contact test showed that the films present thermal response. It was possible to induce a change in solid films from transparent to opaque by varying the temperature and verify the reversibility of this change. In addition, mechanical tests of traction/deformation were carried out, which proved the mechanical improvement of the PNVCL blends when incorporating TPU. The material developed in this work is innovative and has potential for application in many areas.
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13
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RHODIVAM LUCAS MENDES FEITOSA
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Thermoresponsive polymeric films with antimicrobial property.
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Leader : CAROLINA LIPPARELLI MORELLI
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MEMBRES DE LA BANQUE :
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CAROLINA LIPPARELLI MORELLI
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DAYANNE DINIZ DE SOUZA
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FERNANDO HALLWASS
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Data: 7 août 2023
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Afficher le Résumé
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The thermoresponsive polymers are macromolecules capable of reversibly changing their characteristics with temperature variation. This uniqueness makes these materials useful in a wide range of applications such as controlled release of molecules (such as drugs), dressings, scaffolds, tissue engineering and sensors. Poly(N-vinylcaprolactam), PNVCL, is a thermoresponsive and biocompatible polymer whose hydrophilic/hydrophobic transition temperature depends on the molar mass. However, this material does not have good mechanical properties. Poly(butylene adipate co-terephthalate) (PBAT) is a flexible and biocompatible polymer. The production of blends is an interesting route to improve properties by joining different polymers. Cinnamon bark essential oil (CEO) has antimicrobial characteristics and can be used as an additive to polymers to impart this property. In the present work, PNVCL was synthesized by two different routes, one using 3-mercaptopropionic acid (MPA) as chain transfer agent and the other without MPA. PNVCL films were made by casting method. Then, a blend of the thermoresponsive polymer with PBAT was produced by casting in order to improve the mechanical properties. In addition, CEO was added to the polymeric films produced to form potential materials with antimicrobial properties. The obtained materials were characterized by infrared spectroscopy, nuclear magnetic resonance, X-ray fluorescence, X-ray energy dispersive (EDS), differential scanning calorimetry, thermogravimetry, viscosimetry, gel permeation chromatography, cloud point, turbidity test of films, relaxometry, contact angle, scanning electron microscopy, mechanical dynamic analysis, antimicrobial analysis, cytotoxicity. The polymers were obtained by the performed syntheses. There was also success in the formation of polymeric films by casting. The different characterization techniques confirmed the production of thermoresponsive polymers. There was the formation of a partially miscible blend and the addition of essential oil conferred good antimicrobial properties to the materials against Gram-negative and Grampositive bacteria tested. The present research contributes to the dissemination of knowledge about the thermoresponsive polymer PNVCL, and the production of intelligent materials with antimicrobial properties.
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14
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TEREZA RAQUEL RODRIGUES MARQUES
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DEVELOPMENT AND CHARACTERIZATION OF POLYMERS BASED ON POLYCAPROLACTONE (PCL) AND GINGER POWDER WITH PROTEOLYTIC PROPERTIES.
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Leader : GLORIA MARIA VINHAS
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MEMBRES DE LA BANQUE :
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GLORIA MARIA VINHAS
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SEVERINO ALVES JUNIOR
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VIVIANE FONSECA CAETANO
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Data: 17 août 2023
Ata de defesa assinada:
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As technologies evolve, functions other than conventional ones are required of plastic materials. In this sense, there is a growing demand for new polymers with specific functions, and one way to add these functionalities to polymers is through the use of natural additives, such as ginger, for example. Ginger rhizomes (Zingiber officinale) contain substances with several properties of interest, including enzymes with proteolytic activity, called Zingibaine. The interaction of enzymes with polymers can enable biological functions to be transferred to polymeric materials and bring improved functionality to these materials. In the present study, the extrusion technique was used to add ginger powder to the biodegradable polymer Polycaprolactone (PCL), with the objective of developing a functional polymer with proteolytic property, using the protease of ginger powder (Zingibaína) as a proteolytic agent and PCL as a polymeric matrix. The developed materials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), mechanical assay and scanning electron microscopy (SEM). Furthermore, the presence of proteolytic activity in the formed polymers was evaluated. The results indicated the feasibility of using extrusion processing to incorporate the protease present in ginger powder into the polymer, where the three studied compositions showed proteolytic activity. FTIR analysis indicated that the matrix material was preserved after the addition of ginger powder. The TGA thermal analyzes showed that the PCL formulation with 3% ginger powder showed similar behavior to pure PCL. However, the formulations with 5% and 7% ginger showed a decrease of approximately 7.0°C and 7.5°C, respectively, in the initial degradation temperature. The DSC results showed that the concentrations used did not produce relevant thermal changes in these properties. The tensile tests showed that the elastic modulus did not vary significantly in any of the studied compositions. The values of stress at rupture and deformation at rupture decreased for samples with 5% and 7% of ginger powder, corroborating the SEM images. Therefore, with this study it was possible to develop a functional polymer, bringing the biological functions of the enzymes present in the ginger powder to the PCL matrix, without major changes in the matrix properties, thus expanding the applications of this biodegradable polyester.
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15
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RAFAELA OLIVEIRA HOLANDA DA SILVA
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DEVELOPMENT OF GLUE MORTAR WITH ADDITION OF CHITOSAN: PRODUCTION, MICROSTRUCTURE AND STRENGTH OF ADHESION TO TENSION
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Leader : PATRICIA MARIA ALBUQUERQUE DE FARIAS
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MEMBRES DE LA BANQUE :
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ELIANA CRISTINA BARRETO MONTEIRO
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PATRICIA MARIA ALBUQUERQUE DE FARIAS
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YEDA MEDEIROS BASTOS DE ALMEIDA
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Data: 24 août 2023
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Afficher le Résumé
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The development of sustainable cementitious composites is urgent and urgent, mainly due to the production of Portland cement, which is responsible for up to 7% of global CO2 emissions, one of the main gases that generate the greenhouse effect. Thus, the search for sustainable materials that can provide good performance as partial or complete substitutes for cement is a topic of growing interest and importance. Daily large amounts of shells (exoskeletons) of crustaceans are discarded in the environment. However, these shells contain chitin, the most abundant biopolymer on Earth after cellulose. Through the deacetylation of chitin, chitosan is obtained, which in the present work is used as a partial substitute for Portland cement in adhesive mortars. The viability of such a replacement is evaluated here through the microstructural study and the tensile adhesion strength property. For this, four modified adhesive mortars with different levels of powdered chitosan (0%, 0.1%, 0.3% and 0.4%) were produced to replace the cement mass. These mixtures were applied to standard substrates and added to 10 ceramic plates for each sample. The results indicate that the partial replacement of cement by chitosan, in the production of adhesive mortar, is feasible for additions of up to 0.3%. New cementitious composites with the addition of chitosan as a partial substitute for Portland cement, even in low concentrations, have the potential to bring greater sustainability to the production of materials for civil construction.
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16
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LYARA FERREIRA PEREIRA
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NANOCOMPOSITES OF METAL-ORGANIC FRAMEWORKS FOR APPLICATION IN SUPERCAPACITOR ELECTRODES
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Leader : JOANNA ELZBIETA KULESZA BARROS
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MEMBRES DE LA BANQUE :
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EUZEBIO SKOVROINSKI
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JOANNA ELZBIETA KULESZA BARROS
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KLEBER GONCALVES BEZERRA ALVES
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Data: 31 août 2023
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Afficher le Résumé
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As the economies develop and prosper, we will face challenge to feed the demand of more than two-fold energy increase in this century. The increasing demand created fierce worldwide competition for the gradually depleting fossil fuel reserves. Meanwhile, increasing greenhouse emission results in global climate change. All these situations require our society to move towards sustainable and renewable energy resources, such as solar and wind energy. However, due to intermittent feature of solar and wind source, energy storage systems play a key role to the proper utilization of solar and wind energy. Effective chemical storage (e.g. lithium-ion battery and supercapacitors) thereby becomes imperative in the future energy technologies to provide electrical transportation power for commuters and to store energy from intermittent solar or wind power. The electrode is a critical component for controlling the performance of such devices. The fabrication of a high-performance electrode material involves some critical properties such as high conductivity, large specific surface area, temperature stability, good distribution of pores with optimized size, good corrosion resistance, and cost effectiveness. In this sense, porous materials, including Metalorganic Frameworks (MOFs), have been very promising in their application in energy storage devices; however, the problem of low electrical conductivity of such materials needs to be overcome. The association of MOFs with carbonaceous materials has been proposed as an efficient alternative to improve the electrochemical performance of such materials. Therefore, this work aims to synthesize metalorganic frameworks as well as their composites with carbon nanotubes (CNTs) and apply them in supercapacitor electrodes. The Metalorganic Frameworks were synthesized via sonochemical method, from zinc and copper salts coordinated to benzenedicarboxylate ligands. The formation of the composites was carried out by the method of Pickering emulsion, which consists of the formation of an emulsion stabilized by solid particles. The Metalorganic Framework of zinc (ZnMOF) or copper (CuMOF) was dispersed in dichloromethane, oil phase, and the functionalized carbon nanotubes dispersed in distilled water, water phase. The samples were characterized by the X-ray diffraction method, absorption spectroscopy in the infrared region with Fourier transform, scanning electron microscopy and thermal analysis. The electrochemical behavior of Metalorganic Frameworks and their composites was evaluated by the cyclic voltammetry technique using coin cell devices.
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17
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LUIS VINICIUS GONÇALVES DE MELO
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Synthesis of Sulfonatobisperilenimides as Chromonic Mesogens for the Preparation of Lyotropic Liquid Crystals as Alignment Medium in NMR
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Leader : FERNANDO HALLWASS
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MEMBRES DE LA BANQUE :
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FERNANDO HALLWASS
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JULIANA ECCHER
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RICARDO OLIVEIRA DA SILVA
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Data: 1 sept. 2023
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Afficher le Résumé
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Lyotropic liquid crystals have been used, among other applications, as alignment media in Nuclear Magnetic Resonance spectroscopy (NMR) experiments to generate anisotropy in the sample. In this way, the anisotropic NMR observables, such as dipolar coupling, quadrupolar coupling and chemical shift anisotropy, can be partially recovered, providing new geometric information about the molecular structure. In this work, three bisperilenimides were synthesized with peripheral solubilizing agents, containing sulfonates, to form chromonic phases soluble in aqueous medium. The synthesis of these compounds was carried out from the conjugation of perylenetetracarboxylic dianhydride with: aminoethanesulfonic acid, sulphanilic acid and aminomethanesulfonic acid, forming di(ethanesulfonic) perylene-3,4,9,10- bis(dicarboximide) disodium (BPI-ES), di(p-benzenesulfonic) perylene-3,4,9,10-bis(dicarboximide) diimidazole (BPI- pBS) and di(methanesulfonic) perylene-3,4,9,10-bis(dicarboximide) disodium (BPIMS), respectively. The reaction yields were 74 % for BPI-ES, 86% for BPI-p-BS and 73 % for BPI-MS. The compounds were characterized by NMR, Infrared and Ultraviolet-visible spectroscopy. The formation of the mesophase was evaluated by splitting the 2 H NMR signal at different concentrations at 25o C and 50o C, as well as analysing the textures of Polarized Light Microscopy images obtained in this work. The studied conditions of temperature and concentrations studied, it was observed the formation of the mesophase in the BPI-ES system at 0.2 M aqueous solution, indicating that this mesogen could be used as an alignment medium for anisotropic NMR measurements.
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18
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RENATA PEREIRA DA SILVA
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Nanocatalisadores à base de cobre para a produção de hidrogênio via desidrogenação do borohidreto de sódio
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Leader : JOANNA ELZBIETA KULESZA BARROS
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MEMBRES DE LA BANQUE :
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JOANNA ELZBIETA KULESZA BARROS
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MARIANA PAOLA CABRERA
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JARLEY FAGNER SILVA DO NASCIMENTO
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Data: 29 sept. 2023
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Afficher le Résumé
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A produção de hidrogênio tem sido um campo de intensa investigação devido ao seu potencial como vetor energético limpo e versátil. Este trabalho se concentra na utilização de nanocatalisadores de cobre, baseados em estruturas metal-orgânicas (MOFs), para a produção de hidrogênio via desidrogenação do borohidreto de sódio. O objetivo principal é avaliar o potencial desses nanocatalisadores e compreender seu desempenho na reação de desidrogenação. O estudo inicia-se com a análise da eficiência dos nanocatalisadores de cobre/MOFs como promotores da reação de desidrogenação do borohidreto de sódio. Avaliações detalhadas incluem a determinação dos rendimentos, taxas de formação e a frequência de rotação (TOF) em diferentes temperaturas (25 °C, 35 °C e 45 °C). Além disso, é investigada a viabilidade de reutilização dos nanocatalisadores/MOFs, visando avaliar a sua atividade catalítica em ciclos consecutivos. Outro ponto de interesse é a avaliação da estabilidade dos nanocatalisadores/MOFs em um meio alcalino. Este estudo oferece uma contribuição significativa para a pesquisa em produção de hidrogênio, ao explorar os nanocatalisadores de cobre/MOFs na desidrogenação do borohidreto de sódio. As caracterizações em FTIR dos catalisadores/MOFs foram realizadas antes e depois da reação de hidrólise, para observar ou identificar mudanças na estrutura molecular e em ligações químicas. Todas as análises foram conduzidas em triplicata para reduzir erros sistemáticos e determinar o desvio padrão dos resultados obtidos. A estabilidade catalítica foi um ponto de destaque na análise dos ciclos de reutilização do catalisador/MOF. Notou-se que, embora o Cu-BDC tenha mantido uma produção estável do segundo ao quinto ciclo, o ponto negativo dessa estabilidade tornou-se evidente no primeiro ciclo. Além disso, a introdução de NaOH no sistema apresentou um efeito inesperado, resultando em uma drástica queda na produção de hidrogênio.
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19
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LEDJANE MARIA ALVES OLIVEIRA
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CHEMICAL AND CRYSTALLOGRAPHIC CHARACTERIZATION OF PHOTOVOLTAIC WASTE OBTAINED BY MECHANICAL SEPARATION
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Leader : NATHALIA BEZERRA DE LIMA
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MEMBRES DE LA BANQUE :
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NATHALIA BEZERRA DE LIMA
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MARIA SUELY COSTA DA CÂMARA
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JOSÉ FERNANDO DAGNONE FIGUEIREDO
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Data: 25 oct. 2023
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Afficher le Résumé
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Climate change challenges our way of life, consumption and production. Among the various solutions that have been suggested, we have the energy transition in search of cleaner, renewable energies such as solar power. The expected installed capacity of photovoltaic energy by 2050 is 5,000 GW. However, the increase in solar energy will result in a significant increase in photovoltaic waste by 2050, estimated between 60 and 78 million tons. Recycling said materials is essential for environmentally proper management. Identifying and chemically characterizing the components of solar panels is crucial for assessing the purity and feasibility of recycling, increasing the economic value of recoverable raw materials and promoting a circular economy. There are currently research groups and companies developing separation processes for photovoltaic materials, using physical and chemical techniques and advanced separation technologies. Due to the aforementioned scenario, the present work identified and chemically and crystallographically characterized mechanically separated photovoltaic materials in the recycling industry, using X-ray Fluorescence Spectroscopy and X-ray Diffraction techniques, analyzing the level of purity of each component and its structural alteration after the recycling process, in order to subsequently enable the appropriate reinsertion of the materials in various segments of the industry. The results indicate that when photovoltaic materials are subjected to a mechanical separation process, contamination occurs and the physical-chemical characteristics of the materials are altered. However, in the case of EVA, which contains greater quantities of other materials such as glass and aggregated semiconductors, the reduction in particle size results in greater purity of the material. With regard to the presence of heavy metals that could contaminate the environment, the additional application of magnetic separation methods or the use of density-based techniques allows for a significant reduction in the concentration of these metals.
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20
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JOSEFA LUANA DA SILVA SOUSA
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MECHANOCHEMICAL SYNTHESIS OF NITROGENATED GRAPHENE: IMPACT ON CULTIVATING MODELS IN THE ADMINISTRATION OF MACROELEMENTS
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Leader : PETRUS D AMORIM SANTA CRUZ OLIVEIRA
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MEMBRES DE LA BANQUE :
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ETELINO JOSÉ MONTEIRO VERA CRUZ FEIJÓ DE MELO
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PETRUS D AMORIM SANTA CRUZ OLIVEIRA
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RICARDO SCHNEIDER
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Data: 24 nov. 2023
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Afficher le Résumé
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Graphite is used in mechanized agriculture as a natural lubricant. Graphite powder is added to the seeds with the sole aim of reducing friction with the mechanics of mechanical seeders. In this study, a system was developed to perform the direct exfoliation of graphite powder Grafsolo® (Nacional de Grafite Ltda.) under high nitrogen pressure to obtain few-layer graphene (FLG) with the incorporation of nitrogen at the edges to add value with the functionalization of the lubricating material. Among N, P, and K, Nitrogen was chosen as a macroelement model, and an entire indoor cultivation system was designed and automated to choose a cultivar model as a plant ideotype for the tests. Based on the established parameters, santa cruz okra was chosen as a cultivar model, and the first trials were planned and carried out at this master's project. This approach established a proof of concept (PoC) for introducing high-pressure nitrogen while adhering to a solvent-free and environmentally friendly process. As a raw material, the choice of Grafsolo® was strategic, as this type of powdered graphite is widely used in various crops by the agroindustry and is commercially available, which favors the feasibility of scaling production. Focusing on agricultural applications, the research explored nitrogenous graphene as a coating for okra seeds of the santa cruz 47 type (ISLA Sementes Ltda.) during planting, aiming to provide more nitrogen as a primary macronutrient. For this, optimizations were carried out in the milling system to obtain nitrogenous graphene and the indoor cultivation system, guaranteeing an environment in conditions similar to the natural one for seed germination. The detailed characterization of the material was conducted using infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-Ray Diffraction (XRD), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). Based on the results obtained, the efficiency of graphite exfoliation and the presence of nitrogen were verified through FTIR analysis. SEM images demonstrated the viability of producing nitrogenous graphene using the high-pressure mechanochemical method.
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21
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EWELLYN SILVA SOUZA
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Carbon material modified with transition metal oxides applied to energy storage systems.
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Leader : ANDRE GALEMBECK
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MEMBRES DE LA BANQUE :
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ANDRE GALEMBECK
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GILBERTO AUGUSTO DE OLIVEIRA BRITO
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JOANNA ELZBIETA KULESZA BARROS
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Data: 30 nov. 2023
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Afficher le Résumé
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In recent years, the automotive industry has required more efficient and reliable leadacid batteries. This demand arises from the use of electrical systems providing various functions to the vehicles, aiming to enhance the driver convenience and some systems to reduce fuel consumption. An example is the start-stop technology that shuts off the combustion engine when the vehicle stops. The batteries used in these vehicles must be robust and efficient enough to withstand numerous engine ignition and keep the electrical systems operational during stops. To meet these demands, the battery industry has been constantly introducing developments to the lead-acid accumulators. For instance, some of the new additives applied to the negative electrodes, such as high specific surface area carbons. Generally, these carbons facilitate the battery's charging and discharging processes due to various modifications in the negative electrode characteristics, which improves the battery charge acceptance. However, many of these carbons increases the evolution of H2 on the negative electrode, increasing water consumption and reducing the device's lifespan. As a strategy to improve charge acceptance performance and reduce the water consumption, it is proposed here the carbon modification with low exchange current for the H2 evolution reaction metal oxides such as Nb and Zn. The oxide was incorporated into the carbon through a hydrothermal treatment using an aqueous solution of soluble metal precursors, followed by drying and thermal treatment in N2 atmosphere. The results obtained in 5 Ah lead-acid cells showed that the carbon modification led to a considerable reduction, approximately 66%, in water loss and a significant increase in charge acceptance efficiency, approximately 89%, compared to the respective pristine carbon. The modified carbon exhibited highly desirable characteristics for application as an additive to the negative electrode of lead-acid batteries and is a strategy to be considered for improving the performance and efficiency of this type of accumulator.
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22
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DOUGLAS GOMES DA SILVA
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COORDINATION ASYMMETRY AND ITS EFFECT ON THE INTENSIFICATION OF LUMINESCENCE OF EUROPIUM TERNARY COMPLEXES
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Leader : SIMONE MARIA DA CRUZ GONCALVES
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MEMBRES DE LA BANQUE :
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SIMONE MARIA DA CRUZ GONCALVES
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YEDA MEDEIROS BASTOS DE ALMEIDA
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IVANI MALVESTITI
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Data: 5 déc. 2023
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Afficher le Résumé
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The europium ternary complexes, coordinated with β-diketonate ligands, exhibit luminescent properties under ultraviolet radiation and find applications as luminescent thermometers, biological markers, and inorganic diodes. Highlighting the efficient synthetic routes, the Faster Synthesis method, developed at Lom, demonstrates high yields and reduced complex acquisition times. Advancing this methodology, the use of a microwave reactor results in a more sustainable approach with even shorter synthesis times and enhanced product purity. Our findings emphasize the crucial role of ligand addition order and the introduction of "symmetry-breaking" ligands in intensifying luminescence quantum efficiency. Current focus involves exploring luminescence properties with other symmetry-breaking ligands, adapting the Rapid Synthesis methodology to microwave reactors using different europium salts. In this dissertation, luminescent europium ternary complexes were synthesized in a microwave reactor with one or two symmetry-breaking ligands, with general formulas [EuX(β)2(L)2] and [EuX2(β)(L)3], where X = Cl- or NO3-, β = BTFA (4,4,4-trifluoro-1-phenylbutan-1,3-dionate) or TTA (4,4,4-trifluoro-1-thiophen-2-yl-butan-1,3-dionate), and L = TPPO (triphenylphosphine oxide) or PTSO (p-tolylsulfoxide). Our evaluation of Cl- and NO3- ligands' influence on complex structure, synthesis yields, and luminescence efficiency revealed generally higher yields with Cl- ligands, exemplified by [EuCl2(BTFA)(TPPO)3] and [Eu(NO3)2(BTFA)(TPPO)3] showing synthesis yields of 91% and 40%, respectively. Computational calculations of thermodynamic properties supported experimental results, indicating energetically favorable syntheses with Cl- ligands compared to NO3-. Luminescence property results highlighted the significant impact of the nitrate ligand on increased quantum efficiency, followed by the BTFA ligand in complexes such as [Eu(NO3)(BTFA)2(TPPO)2] (η = 57%), [Eu(NO3)2(BTFA)(TPPO)3] (η = 52%), [EuCl(BTFA)2(TPPO)2] (η = 51%), and [EuCl2(BTFA)(TPPO)3] (η = 49%). Conversely, the absence of nitrate or chloride led to lower quantum efficiency, as observed in the complex with three β-diketonates: [Eu(BTFA)3(TPPO)2] (η = 34%). These results indicate that inorganic ligands appear to disrupt the spherical symmetry of the complex, enhancing luminescence. Our study contributes to the development of simpler and more economical synthetic routes using microwave procedures and design strategies to enhance luminescence in europium complexes coordinated with β-diketonate ligands incorporating inorganic ligands.
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LILIAN KÁSSIA CAVALCANTE DA SILVA DE ASSIS
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MANUFACTURE OF NANOSTRUCTURES IN YTTRIUM IRON GARNET FILM ON SILICON SUBSTRATE FOR THE STUDY SPINTRONICS PHENOMENA
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Leader : EDUARDO PADRON HERNANDEZ
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MEMBRES DE LA BANQUE :
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EDUARDO PADRON HERNANDEZ
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GLORIA MARIA VINHAS
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ALVARO ANTONIO OCHOA VILLA
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JOSE ANGELO PEIXOTO DA COSTA
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ROBERTO LAZARO RODRIGUEZ SUAREZ
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Data: 9 mars 2023
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Afficher le Résumé
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The general objective of this work is to manufacture quality nanostructured YIG films for the study of spintronics phenomena. Specifically Obtain YIG films by the MOD wet chemical method, with sufficient quality for the study of spintronics phenomena. Also make a detailed structural study of each system using High Resolution Electron Microscopy (HREM) to verify the effects of surface disorder on the magnetic properties in nanometric systems manufactured by us. Manufacture slits and guides on the previously manufactured YIG films, from a nanomachining process by IBL in FIB to study the dispersion of spin wave dispersion dynamics. To produce arrays of elongated square, circular, rectangular nanostructures in YIG films on Si (100) by EBL and IBL processes to study spintronic phenomena observed in films obtained by conventional techniques. Using FIB and EBL techniques to form hybrid structures made of YIG and platinum films to simulate spintronic effects resulting in hybrid spintronic devices.
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ELIBE SILVA SOUZA
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Nanocomposites Based on Metalorganic Zinc Networks as Supports for Metallic Nanoparticles: Catalysts for Hydrogen Production and Biocidal Agents
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Leader : JOANNA ELZBIETA KULESZA BARROS
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MEMBRES DE LA BANQUE :
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EDUARDO PADRON HERNANDEZ
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GIOVANNIA ARAUJO DE LIMA PEREIRA
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JANILSON ALVES FERREIRA
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JOANNA ELZBIETA KULESZA BARROS
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LEONIS LOURENÇO DA LUZ
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Data: 19 avr. 2023
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Afficher le Résumé
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Nanotechnology, as an emerging field, is widely used in the areas of clean energy generation and public health, which are current and relevant global problems to be solved. In this sense, metallic nanoparticles (MNPs) have been extensively studied for their magnetic, electronic, optical, antimicrobial and catalytic properties. The manipulation of MNPs to create new materials with specific desired physicochemical properties has shown promise. The combination of MNPs with a porous nanomaterial, such as Metal-Organic Framework (MOF), suppresses the main problem of MNP applications, which is the aggregation resulting from high surface energies. This work presents the synthesis and characterization of nanocomposites based on zinc MOFs, [Zn₂(1,3-bdc)(Bzim)₂] and [Zn(mim)], as support for the incorporation of MNPs (M= Cu, Ag or Au) in order to avoid aggregation and improve properties with respect to their counterparts. For this proof of concept, the Ship in bottle and One-pot methods were used. The synthesized materials were characterized by XRD, SEM, FTIR, ICP-OES, TGA/DTA and BET. MNPs were characterized by absorption spectroscopy in the UVvisible region. The catalytic properties of the synthesized materials were evaluated using the water displacement method, measuring the volume of hydrogen gas generated in the dehydrogenation of the hydrogen storage molecule NH₃BH₃ with the dependence of time, varying temperature and NaOH. Antibacterial properties were evaluated from disc diffusion tests on bacteria against Gram-positive and Gramnegative bacterial strains. The incorporation of MNPs by the methods used did not alter the stability and structural crystalline characteristics of the nanomaterials. The nanocomposites OP:AuNPs@Zn(mim) and OP:AgNPs@Zn(mim) stood out as catalysts for presenting excellent catalytic activities in the hydrolysis of NH₃BH₃, with high rates of hydrogen generation (1979.53 mL min-1 gAu- 1 and 3352.71 mL min-1 gAg- 1) and high efficiency (69.16% and 98.5%). The activation energies were 19.6 kJ.mol- 1 for OP:AuNPs@Zn(mim) and 38.13 kJ.mol-1 for OP:AgNPs@Zn(mim), which are lower than for most of the catalysts containing Au/Ag-MOF used in the hydrolysis of NH₃BH₃ described in the literature. Furthermore, these catalysts showed good stability and reuse, preserving 71.42%, OP:AuNPs@Zn(mim), and 88.23%, OP:AgNPs@Zn(mim), of their initial catalytic activities after five cycles. As biocidal agents, the Zn₂(1,3-bdc) (Bzim)₂ support effectively prevented the aggregation of MNPs and the bactericidal properties of the nanocomposites were enhanced up to thirteen times greater than the nanoparticle without the metalorganic support and up to sixteen times greater than the antibiotic amoxicillin. Therefore, the materials presented here proved to be excellent candidates to produce hydrogen from NH₃BH₃, in particular, OP:AgNPs@Zn(mim), with the combination of a simple synthesis method, low reaction temperature, environmentally friendly solvent, low content of of MNPs, relatively low cost and mild dehydrogenation conditions. From another perspective, the nanocomposites of the Zn₂(1,3-bdc) (Bzim)₂ support with AgNPs and CuNPs showed promise as biocidal agents, being more economical and with a low content of MNPs.
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JOÃO RICARDO PEREIRA DA SILVA
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CEMENTARY COMPOSITES OF CHITOSAN AND PORTLAND CEMENT: PRODUCTION, ANALYSIS OF STRUCTURAL INTERACTIONS AND PROPERTIES OF INTEREST IN CIVIL CONSTRUCTION
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Leader : PATRICIA MARIA ALBUQUERQUE DE FARIAS
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MEMBRES DE LA BANQUE :
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EDUARDO PADRON HERNANDEZ
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GLORIA MARIA VINHAS
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JOSE ANGELO PEIXOTO DA COSTA
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YEDA MEDEIROS BASTOS DE ALMEIDA
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YÊDA VIEIRA PÓVOAS
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Data: 11 mai 2023
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Civil construction plays an important role in energy consumption worldwide and significantly influences the total consumption of natural resources and CO2 emissions. The use of renewable materials is intrinsically related to research and innovation. Reuse, recycling, as well as the development of new materials and the discovery of new applications for already known renewable materials, can significantly contribute to sustainable development. Chitosan (CS) is a biopolymer with a unique chemical structure and characteristics, combined with its abundant availability as a derivative of chitin, which means that its application possibilities in the most different technological fields have expanded considerably. In the present work, the use of chitosan for the production of cementitious composites is presented and discussed. The influence of chitosan incorporated in the composites through optimal levels was evaluated. The chitosan contents incorporated in the dosage were 0.1%; 0.3% and 0.4%, in relation to the cement mass. Also in concrete and mortar, compressive strength and consistency tests were carried out. The microstructures were examined using scanning electron microscopy (SEM), X-ray fluorescence (FRX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and TG/DSC. As a result, CS powder not only has a physical effect on cement hydration, but also has a chemical effect influencing the amount and type of hydrates formed. Also, relationships between chemically bound water, influence of supplementary cementitious material on cement hydration and durability are presented. No adverse effect was observed on the microstructural behavior of the composites due to the replacement of cement by CS powder. The results were favorable to the incorporation of chitosan (up to 0.4% substitution), being positive in terms of mechanical properties and durability for most of the techniques used, which strongly indicates that chitosan can be considered as a promising material to be incorporated in the production of concret.
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JESSICA ITAIANE RAMOS DE SOUZA
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TOPOLOGICAL PROPERTIES OF NETWORKS OF HYDROGEN BONDS IN WATER UNDER DIFFERENT CONDITIONS
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Leader : RICARDO LUIZ LONGO
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MEMBRES DE LA BANQUE :
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MARCIA CRISTINA BERNARDES BARBOSA
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DENYS EWERTON DA SILVA SANTOS
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FILIPE DA SILVA LIMA
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RICARDO LUIZ LONGO
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SERGIO WLADEMIR DA SILVA APOLINARIO
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Data: 1 juin 2023
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Bulk and confined liquid water exhibit highly structured molecular arrangements related to their unusual (or "anomalous") properties. These characteristics are attributed to the structure and dynamics of the hydrogen bonding networks formed and maintained by this dominant intermolecular interaction. In this work, we performed a topological analysis based on complex networks (binary and weighted) and island statistics of hydrogen bonding networks of bulk water at different temperatures and of water confined in reverse micelles. The influence of temperature on liquid water structures and the effect of confinement on the topological properties of hydrogen bonding networks we investigated using Metropolis Monte Carlo and molecular dynamics simulations with TIP4P/2005 and TIP3P potential models, respectively. For bulk water at different temperatures, results showed that, at all temperatures evaluated, the hydrogen bonding network in water has a characteristic topology of a percolated network. However, the semi-global path length descriptor, L, shows a trimodal distribution with temperature-dependent areas. Considering the equilibrium between these three sets of networks, the standard enthalpy and entropy of equilibrium were determined for the first time, providing new insights into the structural heterogeneities of liquid water with exciting perspectives for modeling these quantitative properties of hydrogen bonding networks. For confined water, a bimodal distribution of L was observed only for water confined in the larger micelle , whose behavior is similar to bulk water. The water in the three confinements studied here exhibit characteristics of small-world networks, as they presented e . In particular, the water confined in the smaller micelle ( ) showed traces of a subclass of small-world networks, large-scale (broad-scale), and showed a significant restriction in the hydrogen bonds formed. Except for the path length, L, the topological properties of binary and weighted networks of all the systems studied here show similar behavior.
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DAIANE DE SOUZA CARVALHO
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Synthesis And Application Of Polymeric Gels As A Alignment Media In NMR.
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Leader : ARMANDO JUAN NAVARRO VAZQUEZ
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MEMBRES DE LA BANQUE :
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MASSIMO LAZZARI
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ARMANDO JUAN NAVARRO VAZQUEZ
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JUAN CARLOS FUENTES-MONTEVERDE
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VICTOR MANUEL SANCHEZ PEDREGAL
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YEDA MEDEIROS BASTOS DE ALMEIDA
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Data: 21 juil. 2023
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Neste trabalho foram desenvolvidos dois novos géis poliméricos aplicados à RMN em meios orientados para o estudo da elucidação estrutural de moléculas orgânicas pequenas a partir de parâmetros anisotrópicos, como o acoplamento dipolar residual (RDC) e anisotropia do deslocamento químico residual (RCSA). A eficiência do gel de N,N-dimetilacrilamida/acrilonitrila (DMA/AN), compatível com acetonitrila-d3 e metanol-d4 como meio de alinhamento, foi testada usando as moléculas α-santonina e brucina. O gel de acrilonitrila/ácido 2-acrilamida-2- metil-1-propano sulfônico (AN/AMPS), compatível com D2O, foi testado com as moléculas sacarose e lactose. Para isto foram realizados experimentos de RMN uni e bidimensionais. A determinação do espaço conformacional das moléculas foram explorados a partir de cálculos de mecânica molecular, usando o campo de força MMFF94. O gel de (DMA/AN) compatível com acetonitrila-d3 apresentou um bom desempenho para extração de medidas de RDCs. Para a molécula de α-santonina os valores de RDCs ficaram na faixa de -14,4 a 5,4 Hz e o fator de qualidade Q de 0,011. Para a molécula de brucina os valores de RDCs variaram de -9,9 a 23,1 Hz e fator de qualidade Q de 0,047. Com esses valores de RDCs foi possível determinar a configuração relativa das moléculas testes. Os resultados usando apenas dados de RCSAs não foram adequados para a discriminação correta das moléculas, devido aos sinais serem muito alargados nos espectros de RMN de 13C. O gel de (DMA/AN) compatível com metanol-d4 apresentou um comportamento adequado para extração de RDCs com valores na faixa de -15,1 a 15,9 Hz e fator de qualidade Q de 0,069, o que possibilitou a configuração relativa correta da brucina. Porém, devido ao alargamento dos sinais nos espectros de RMN de 13C poucas medidas puderam ser extraídas e, dessa forma, não foi possível obter resultados satisfatórios de RCSAs. Por fim, o gel de AN/AMPS apresentou um bom desempenho para extração de medidas de RDCs em D2O usando as moléculas de sacarose e lactose, com valores na faixa de -9,3 a 3,5 Hz e -6,8 a 2,0 Hz, respectivamente. Com os resultados da sacarose, o fator de qualidade Q de 0,127 foi obtido para o melhor conjunto de conformações. Para a α-lactose e β-lactose os valores do fator de qualidade Q foram 0,078 e 0,089, respectivamente.
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TALITA JORDANNA DE SOUZA RAMOS
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DISCRETE AND CONTINUOUS UPCONVERSION EMISSIONS IN OXIDES DOPED WITH LANTHANIDE IONS
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Leader : OSCAR MANOEL LOUREIRO MALTA
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MEMBRES DE LA BANQUE :
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OSCAR MANOEL LOUREIRO MALTA
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CID BARTOLOMEU DE ARAUJO
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SIDNEY JOSE LIMA RIBEIRO
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DANILO MANZANI
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VERÓNICA CORTÉS DE ZEA BERMÚDEZ
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LUÍS ANTÓNIO FERREIRA MARTINS DIAS CARLOS
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Data: 28 juil. 2023
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Afficher le Résumé
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In inorganic materials, based on or doped with lanthanides, energy upconversion (UC) luminescence can be mediated by different mechanisms, such as excited state absorption, energy transfer upconversion, and photon avalanche processes. However, these mechanisms lead to UC emission characterized by discrete spectra and, therefore, cannot explain the generation of white light characterized by continuous spectrum observed in pure, doped, or co-doped lanthanide oxides upon NIR excitation. In this thesis, we present our contribution to the elucidation of the mechanism that promotes the emission of white light, characterized by a continuous spectrum, upon excitation in the NIR, depending on the composition of the samples, thermal conductivity, distribution, and size of particles, as well as the conditions of excitation (wavelength, cycles, and excitation time). We elaborated a study of the photophysical behavior for mechanical mixtures of commercial oxides Gd2O3, Yb2O3 and Er2O3, and for synthesized nanoparticles with compositions: Yb2O3 and Er2O3 (pure); (Gd0,99Er0,01)2O3 and (Gd0,99Yb0,01)2O3 (doped); and (Gd0,89Yb0,10Er0,01)2O3 (co-doped), as a function of temperature, humidity, and pressure. The spectral and temporal behaviors observed for the emission characterized by broadband, namely, the fits of the emission in the visible region to the blackbody emission curve and the analysis of the temporal dynamics for different power densities (which show the patterns consistent with heating and cooling steps) suggest that the white light emission is of thermal origin. This is corroborated by the transition of the discrete to continuous UC emission caused by the optical heating of the sample. The synthesized nanoparticles (Gd0,89Yb0,10Er0,01)2O3 behave as primary luminescent thermometers (under NIR excitation) in the range of 299–363 K, using the Er3+ emission intensity ratio 2H11/2→4 I15/2/ 4S3/2→4 I15/2, and as a secondary luminescent thermometer in the range 1949–3086 K, based on the blackbody distribution curve of the observed white light emission. The results regarding the relationship between the temperature of the excitation region and the power density used to excite the sample will be useful for the development of theoretical models and for solving the differential equations that describe the emission of white light by laser heating.
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KARINA CARVALHO DE SOUZA
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PRODUCTION AND EVALUATION OF BACTERIAL CELLULOSE IN LOW COST CULTURE MEDIA FOR APPLICATION IN SUSTAINABLE PACKAGING
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Leader : GLORIA MARIA VINHAS
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MEMBRES DE LA BANQUE :
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CAROLINA LIPPARELLI MORELLI
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CRISTIANA MARIA PEDROSO YOSHIDA
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FELIPE PEDRO DA COSTA GOMES
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GLORIA MARIA VINHAS
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SARA HORACIO DE OLIVEIRA MACIEL
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Data: 2 août 2023
Ata de defesa assinada:
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Afficher le Résumé
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Cellulose, represented by the formula (C6H10O5)n, is a polysaccharide that can be of vegetable or microbial origin. Its bacterial production, due to its high degree of purity and properties, has potential for applications in the medical, pharmaceutical, cosmetics, food, packaging, composites industries, among others. The production of pure cellulose nanofibrils by bacteria of the genus Komagataeibacter occurs from the consumption of glucose in the medium, metabolized into cellulose by the microorganisms. In this study, the tests were divided into three stages: the first was performed using starch, present in rice and corn grains, as a carbon source for BC production. For this, the starch was hydrolyzed by fungi (Aspergillus oryzae) to obtain glucose, used for the production of BC. The results obtained showed a maximum yield of 2.80 ± 0.43 g / L of BC obtained with the hydrolyzed rice medium. In the second stage of the experiments, the production of BC was carried out using a saline solution, of its own composition, with the addition of carbohydrates and/or proteins (Glucose, Glycerol, Sucrose, Fructose, Peptone, Yeast Extract or Mannitol) as carbon sources . The maximum yield of 5.72 ± 0.01 g / L of BC was obtained with the medium containing Sucrose. In the third stage, the prototype of a sustainable package, with characteristics of a paper package, was developed. All materials produced were characterized in terms of morphology (Scanning Electron Microscopy - SEM), crystallinity (X- ray Diffraction - DRX), thermal stability (Thermogravimetric Analysis - TGA) and analysis of functional groups (Infrared with Fourier Transform - FTIR) . In the first stage of the characterizations, the FTIR confirmed the functional groups present in the BC, as well as the absence of contaminants from the production process. XRD evaluation showed crystallinity around 55%. The TGA analysis revealed that the polymers formed from the alternative media (Rice or Corn) obtained greater thermal stability. SEM showed a non-uniform structure with the random arrangement of nanofibrils. In the second stage of characterization, the diffractograms revealed a crystallinity that varied from 31% (CB-Yeast Extract) to 66% (CB-Fructose) and the FTIR analysis confirmed the existing functional groups in the bacterial cellulose, without possible contaminants. The TGA of the CB-Yeast extract and CB-Mannitol biopolymers revealed maximum degradation temperatures (Tmax.) of 350.7 oC and 322.0 oC, respectively. From the micrographs, CB-Glucose and CB-Sucrose had areas of more dispersed and visible fibrillar structures compared to the others. Finally, the characterizations of the CB-Paper used in the development of a packaging prototype presented Tmax. of 311.8 oC and crystallinity 86.42% with characteristic peaks of cellulose and calcium carbonate present in papers. In the SEM investigation, fibrous and nanometric morphology were observed together with calcite fillers. Therefore, studies like this present new culture media for the production of BC, as well as an important application for these biopolymers, in order to create alternatives to vegetable cellulose, used, for example, in the food packaging industry.
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SAMUEL JÔNATAS DE CASTRO LOPES
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INFLUENCE OF COMPOSITION MODULATION ON THE MICROSTRUCTURALAND MAGNETIC PROPERTIES OF Ni/Cu NANOWIRES.
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Leader : EDUARDO PADRON HERNANDEZ
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MEMBRES DE LA BANQUE :
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BARTOLOMEU CRUZ VIANA NETO
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EDUARDO PADRON HERNANDEZ
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GILVANIA LUCIA DA SILVA VILELA
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MICHAEL CABRERA BAEZ
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YUSET GUERRA DAVILA
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Data: 11 août 2023
Ata de defesa assinada:
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In the present work, continuous and composition-modulated magnetic nanowires were electrodeposited into commercial alumina porous membranes with pore diameters of approximately 250 nm. Initially, two samples were synthesized using the chronopotentiometry mode and a conventional working electrode (Au). To optimize the synthesis process, carbon conductive ink commonly used in electron microscopy was employed for the fabrication of the working electrode. To demonstrate the efficiency and reproducibility of this new method, continuous and composition-modulated nanowires were electrodeposited using the chronopotentiometry mode. Morphological characterization indicated the formation of continuous and composition-modulated nanowires. Furthermore, it was proven that the chronopotentiometry method, where the potential is kept constant while the current varies over time, is more efficient in obtaining wires with a more uniform morphology. EDS analysis confirmed that AM-1 and AM-4 consisted of continuous wires, while the other samples were composed of composition- modulated wires. XRD results confirmed that the metallic Ni and Cu present in the wires had a face- centered cubic structure. The W-H method was used to investigate how composition modulation modifies the structural parameters of nickel. Lattice parameter, crystallite size, lattice strain, and dislocation density were calculated. In terms of magnetic characterization, ferromagnetic resonance spectra revealed two distinct resonances. The lower intensity resonance corresponded to the excitation of spins at the material's surface, but further investigations are required. An angular dependence of the resonance field was also observed. Based on the ferromagnetic resonance results, a model was proposed to estimate the wire's anisotropy field and easy magnetization direction. Magnetization versus field curves were obtained using the vibrating sample magnetometry technique. The results demonstrated that the modulation process can influence the easy magnetization direction, coercivity values, and remanence. Additionally, it was possible to investigate how the structural modifications of nickel can influence the magnetic properties of the nanowires.
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LINDEMBERGUE PEREIRA COSTA JÚNIOR
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Effect of organoclay and corn straw on the properties of poly (butylene adipate-co-terephthalate)(PBAT) hybrid composites
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Leader : YEDA MEDEIROS BASTOS DE ALMEIDA
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MEMBRES DE LA BANQUE :
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YEDA MEDEIROS BASTOS DE ALMEIDA
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EDUARDO PADRON HERNANDEZ
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MICHELLE FÉLIX DE ANDRADE
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TATIARA GOMES DE ALMEIDA
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TOMAS JEFERSON ALVES DE MELO
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Data: 28 août 2023
Ata de defesa assinada:
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Afficher le Résumé
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The developed research delas with the production, characterization and determination of the properties of extruded films and injected test specimensofnanocomposites PBAT/organoclay C20A and a new hybrid composite material PBAT/clay C20A/cornstraw. The effect of incorporation and filler content on structure, thermal, rheological, mechanical, barrier, biodegradability and water sorption properties were analyzed. PBAT/C20A nanocomposites containing1, 3 and 5% (m/m) of organophilic clay and PBAT hybrid composites containing 2, 6 and 10%(m/m)ofreinforcement consisting of clay and corn straw in a 1:1 ratio were produced. After hot mixing, inatorque rheometer, the components were crushed in a knife mill and the granules were extrudedintheform of flat films and injected in the form of tensile specimens. The results show an improvement inthetensile strength of the extruded nanocomposite films with the addition of 1% clay in the polymericmatrixand of the injected systems with the addition of fillers at levels of 3% and 5%. In general, the elongationat break of composite and nanocomposite films was lower than that of injected specimens. Whenvegetable fiber is added to the polymer and clay systems, a trend of loss of tensile strength anddecreasein elongation is observed for all systems under study and an increase in the elastic modulus for injectedspecimens and a decrease for extruded films. The hybrid composite (PBAT/clay/corn straw) showedanincrease in biodegradability of 6.84% for the specimens and 3.47% for the flat films. The newhybridmaterial showed inefficiency in barrier properties, by tripling the value of O2 permeability inthefilmsample in relation to pure PBAT, making its application difficult in food packaging and protectivecoatings, but can be indicated for permeable packaging that favors the freshness of some vegetablesandmeats. It is believed that the polymer-fiber interaction effects can be improved with a better processingofthe fiber, making it smaller in sprayers in an attempt to synthesize more homogeneous films. It wasalsopossible to observe, by means of torque rheometry, a slight increase in the degradation of the systemswith the addition of loads (clay and corn straw).
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JOSE VALMIR ALVES JUNIOR
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Study of the Structural, Microstructural and Magnetic Properties of the System [Gd1−xTRx ]3Fe5O12 with TR = Pr, Dy and Lu with x = 0.1, 0.5 and 1.0
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Leader : JOSE ALBINO OLIVEIRA DE AGUIAR
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MEMBRES DE LA BANQUE :
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EDUARDO PADRON HERNANDEZ
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FLAVIA PORTELA SANTOS
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IVAN GARCÍA FORNARIS
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JOSE ALBINO OLIVEIRA DE AGUIAR
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SEVERINO ALVES JUNIOR
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Data: 1 sept. 2023
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Rare earth garnets (TR3Fe5O12) have excellent manetic-electrical and optical properties allowing them to have many applications such as transformers, microwave devices and data storage. Such applications depend on their structure and morphology, which are greatly influenced by the substitution of cationic sites. The system [Gd1−xTRx ]3Fe5O12 with TR = Dy, Lu and Pr with x = 0.1, 0.5 and 1.0 for TR = Dy and Lu and x = 0.1 for TR = Pr was produced using the solid state reaction technique. The material produced after mixing the reagents was pressed into tablets, heat treated and exposed to different conditions of time and temperature. The structural and morphological characterization of the samples were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Which proved the characteristic structure and composition of the garnet-type structure. Magnetic characterization was performed using a vibrating sample magnetometer (VSM). The magnetic responses of the synthesized material were also measured using ZFC-FC (Zero Field Cooling) conditions with constant applied field (1.0, 5.0, 10.0, 20.0 and 25.0 KOe) between temperature ranges from 50 to 350 K; magnetic hysteresis measurements at low temperatures between -30.0 ≤ H ≤ 30.0 KOe fields for certain temperature values. The characterizations allowed comparing the structure and magnetic properties of the rare earth garnet produced in this work.
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MAXWELL ARAGAO MARQUES NOGUEIRA
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NONLINEAR OPTICAL SPECTROSCOPY OF MESOIONIC COMPOUNDS
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Leader : CID BARTOLOMEU DE ARAUJO
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MEMBRES DE LA BANQUE :
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CELSO PINTO DE MELO
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CID BARTOLOMEU DE ARAUJO
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LUCIO HORA ACIOLI
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PETRONIO FILGUEIRAS DE ATHAYDE FILHO
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RICARDO LUIZ LONGO
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Data: 15 sept. 2023
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Afficher le Résumé
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Recent developments in nonlinear optical materials generally search for systems with improved second and third order optical properties, aiming at their use in optoelectronic devices, all-optical limiters, among other applications. In this context, important works focused on the exploration of new organic molecules have been published, focusing mainly on molecules with large nonlinear optical coefficients, fast response times, direct synthesis and processability. In particular, molecules with push-pull electronic structure, which give rise to the delocalization of π-electrons, present high optical hyperpolarizabilities and fast response to non-resonant excitation. Mesoionic compounds (MICs) belong to a class of materials that have great potential for nonlinear optics, as proposed more than two decades ago. Typical MICs have planar heterocyclic dipole structures in which the positive and negative charges are separated and delocalized within a π-electron system, resulting in permanent electric dipole moments that can reach 5D. In this work, we synthesize, characterize, and measure the second- and third-order nonlinearities of MICs from the 1,3-thiazolium-5-thiolate group, dissolved in dimethyl sulfoxide (DMSO) at room temperature. In measuring the second-order polarizability (first hyperpolarizability), we used the hyper-Rayleigh scattering (HRS) technique, operating at in the nanoseconds regime. The measured hyperpolarizability, was used to calculate the static hyperpolarizability, by applying the classical two-level model. By the measures of the first hyperpolarizability and the calculation of the fundamental limits we discuss the second-order optical performance of mesoionic molecules. The second-order nonlinearity of these molecules turned out to be relatively high compared to molecules of similar size. In third-order refraction and absorption measurements, we used the Z-scan technique in the picosecond (at 532 nm) and the femtosecond (at 800 nm) regimes. Under excitation at 532 nm, we observed a refractive behavior with self-defocusing, in the presence of nonlinear dissipative effects: two-photon absorption (2PA) and excited state absorption (ESA). Analysis of the results by the Fast Fourier BPM method, based on a three energy level model, revealed that the ESA cross section is one of the largest ever reported in the literature, being approximately 10 times larger than the linear absorption cross section starting from the ground state . Also noteworthy is the large value of the two-photon absorption cross section (3,7 x 104 GM), consistent with previous results. Normalizing this 2PA cross section, we quantified and discussed the molecular nonlinear optical performance, which indicated a great potential for applications in all-optical limiting and all-optical switching. On the other hand, applying the Z-scan technique, operating at 800 nm, the dependence of the non-linearity with the wavelength is evidenced from the three-photon absorption excitation (3PA).
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ELTON MARLON DE ARAÚJO LIMA
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DEVELOPMENT OF A MAGNETIC NANOCOMPOSITE BASED ON IRON OXIDE AND CONDUCTIVE POLYMER (γ-Fe2O3-POLYTHIOPHENE) AS A PROPOSED THERAPEUTIC PLATFORM AGAINST TEGUMENTARY LEISHMANIASIS
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Leader : CELSO PINTO DE MELO
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MEMBRES DE LA BANQUE :
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JOSMARY RODRIGUES SILVA
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RICARDO BENTES DE AZEVEDO
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BEATE SAEGESSER SANTOS
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CELSO PINTO DE MELO
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FABIO ROCHA FORMIGA
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Data: 22 sept. 2023
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Afficher le Résumé
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In this work, we propose a new nanobiotechnological therapeutic platform, based on the use of a nanocomposite of magnetic iron oxide (γ-Fe2O3) and a conductive polymer (Polythiophene - PTh), developed to overcome the limits of the conventional treatment of cutaneous leishmaniasis. After being synthesized via the Fenton reaction, the hybrid magnetic nanocomposite γ-Fe2O3/PTh was characterized by UV-Vis, FTIR, SEM-EDS, and magnetization and particle size measurement techniques. The effective coating of PTh on the particles of the γ-Fe2O3/PTh nanocomposite was confirmed by spectroscopic measurements, which showed an average size of 41 nm and superparamagnetic behavior, with a magnetization saturation of 15.7 emu/g at room temperature. Then, the cytocompatibility profile of the nanocomposite with mammalian cells and human erythrocytes was investigated, as well as its antiLeishmania potential against two species that cause tegumentary leishmaniasis (L. amazonensis and L. braziliensis) in their two stages of development (promastigotes and amastigote). When we implemented the cytocompatibility studies, we verified that the γ-Fe2O3/PTh nanocomposite did not reduce the viability of the cells tested (peritoneal macrophages, fibroblasts, and vero), having shown a low capacity to cause rupture in human red blood cells of different phenotypes, which indicates a good hemocompatibility. Overall, the in vitro cytotoxicity studies of the γ-Fe2O3/PTh nanocomposite showed it to have a promising cytocompatibility profile, opening the possibility of its use in therapeutic formulations. Finally, it was also possible to show that this nanocomposite significantly inhibited the growth of promastigotes of L. amazonensis (with IC50 = 117.63 μg/mL). For the intracellular amastigote cell form, the one most pathogenic for the human host, the γ-Fe2O3/PTh nanocomposite showed a significant inhibition effect, with an IC50 of 27.1 μg/mL (L. amazonensis) and 16.6 μg /ml (L. braziliensis). It was also verified that the γ-Fe2O3/PTh nanocomposite can cause a more intense depolarization of the mitochondrial membrane on the promastigote forms of L. amazonensis. Our results indicate that the γ-Fe2O3/PTh nanocomposite emerges as a promising material for advances in the treatment of tegumentary leishmaniasis through the proposal of a nanobiotechnological product that would offer good efficacy against different species of parasites without causing damage to the host cell (macrophage).
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JORGE ADRIANO ALVES COELHO
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Theoretical analysis of energy transfer between transition metals and lanthanides in heterometallic complexes
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Leader : OSCAR MANOEL LOUREIRO MALTA
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MEMBRES DE LA BANQUE :
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CID BARTOLOMEU DE ARAUJO
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HERMI FELINTO DE BRITO
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OSCAR MANOEL LOUREIRO MALTA
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SIDNEY JOSE LIMA RIBEIRO
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WAGNER DE MENDONCA FAUSTINO
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Data: 9 nov. 2023
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Afficher le Résumé
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There is an increasing interest in alternatives to the sensitizers of lanthanides ions (Ln3+) for in vivo usage, especially in bio-optical applications. The transition metals (M) are good candidates as chromophores, due to their high absorption rates, and their emission bands that cover a large range of visible, and Near Infrared spectra. Despite the importance of theoretical models for the design of M-Ln3+ with higher efficiency, few works had dedicated efforts to theoretically elucidate the process of Energy Transfer (ET) between M and Ln3+ ions. In this sense, this work has the goal to adapt and apply the theory of intramolecular energy transfer developed by Malta, and collaborators to treat with ET in M-Ln3+ heterometallic complexes. Additionally, another goal is to evaluate the ET model for isotropic exchange interaction between M, and Ln3+ ions, by investigating the overlap orbital of the valence's subshell of the transition metal with the 4f subshells of the Ln3+. The overlap integrals were calculated by the coefficients of molecular orbitals for the diatomic M-Ln3+, acquired in the DFT calculations. Parameters such as the dipole strength, and the overlap spectral factor (F factor) were calculated based on the spectroscopic data available in the literature for the complexes considered. Moreover, the theoretical intensity parameters (Ωλ) were calculated by using the web application JOYSpectra. The results have shown that the exchange interaction is not relevant for typical intermetallic distances (> 5 Å) in complexes of M-Ln3+. On the other hand, the theoretical estimations of ET rates for the dipole-dipole, and dipole-quadrupole mechanisms were in reasonable agreement with the energy transfer rates observed in the systems evaluated, especially in the cases with spectral resonance (complexes of Cr-Nd, Ru-Nd). For the systems that have low spectral resonance, such as the ones with Cr-Eu, and Cr-Yb, the model was extended to consider the phonon assistance in the energy transfer process, based on the approach of Miyakawa-Dexter. The fit of the experimental data was gained for the typical values of Huang-Rhys factors of the lanthanide and Cr3+ ions. In the current stage, the model provided can be useful to predict and explain photophysical properties driven by the transfer of energy between the Ln3+, and transition metal ions.
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KAMILLA VERONIKA RODRIGUES DE ANDRADE SILVA
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BIOFUNCTIONALIZATION OF TITANIUM SURFACE AND ITS ALLOYS FOR BIOMEDICAL APPLICATIONS
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Leader : EDUARDO PADRON HERNANDEZ
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MEMBRES DE LA BANQUE :
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DENISE GRANATO CHUNG
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EDUARDO PADRON HERNANDEZ
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HEBER CLAUDIUS NUNES SILVA
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MARCELLA AUXILIADORA DE MELO LUCENA
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RAMÓN RAUDEL PEÑA GARCIA
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Data: 10 nov. 2023
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Prostheses can be used to replace, mimic or repair parts of bone tissue that have been lost due to systeinic diseases and/or injuries. Titanium and its alloys are the most studied and used materials in the application of this type of implant due to their mechanical characteristics, corrosion resistance and biocompatibility. However, despite its high quality, it is estimated that in the first five years after the implant there is around 10% failure due to problems with osseointegration. Several recent studies have sought different solutions to reduce problems related to bone implants due to osseointegration. Part of these solutions involves the biofunctionalization of the surface of titanium and its alloys. In this sense, we developed this work, which is divided into three aspects, aiming to obtain Titanium discs and some of its alloys with different coatings that enable the functionalization of these surfaces. The first stage of this work relates to the manufacturing and characterization, in addition to biological tests of Ti6A14V and TNZT (Titanium-Niobium-Zirconium-Tantalum) discs. The next step was the deposition of T1O2 and SiO2 followed by their characterization. Finally, the third stage consisted of characterizing the condensed tannin obtained from the bark of the species of Mimosa Tenuiflora and Anadenanthera macrocarpa, trees typical of the caatinga of northeastern Brazil. This material was chosen due to its bactericidal potential. Firstly, the physical-chemical characterization of condensed tannin was carrled out using FTIR, UV-Vis, C RMN, H RMN, EPR and TGA techniques.
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16
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DÁRIO CÉSAR DE OLIVEIRA CONCEIÇÃO
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SÍNTESE AND CHARACTERIZATION OF MESOPOROUS NANOSPHERES OF MAGNETITE AND COBALT FERRITE FOR BIOMEDICAL APPLICATIONS
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Leader : EDUARDO PADRON HERNANDEZ
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MEMBRES DE LA BANQUE :
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ALVARO ANTONIO OCHOA VILLA
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DULCIENE KARLA DE ANDRADE SILVA
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EDUARDO PADRON HERNANDEZ
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JOSE ANGELO PEIXOTO DA COSTA
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RAMÓN RAUDEL PEÑA GARCIA
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Data: 13 nov. 2023
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Magnetic nanoparticles have garnered significant interest in the biomedical field due to their unique properties, such as their size being comparable to cellular structures and their ability to respond to magnetization gradients. In the medical context, these applications encompass a wide range of functionalities, ranging from their use as contrast agents to serving as vehicles for drug delivery. The primary objective of this study revolves around the synthesis and characterization of spherical and mesoporous nanoparticles of Cobalt Ferrite (CoFe2O4) and Magnetite (Fe3O4) for biomedical applications, including their role as drug delivery systems, biological sensors, and in magnetic hyperthermia therapy. The synthesis of the particles was conducted using the solvothermal method assisted by Cetyltrimethylammonium Bromide (CTAB), which acted as a templating agent, creating mesopores within the nanoparticles. The morphology of the particles was characterized using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), revealing the formation of mesoporous spheres with an average size of 132,49 ± 21 nm for the Cobalt Ferrite samples and 75,90 ± 12,55 nm for the Magnetite samples. Chemical composition and crystal structure characterization were performed using X-ray Diffraction, confirming the formation of an inverse spinel structure, characteristic of both Cobalt Ferrite and Magnetite materials. Furthermore, Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed a peak around 580 cm-1, corresponding to the metal-oxygen bond in the Ferrite and Magnetite structures, which was further confirmed by diffraction. Drug absorption assays, based on absorbance measurements, allowed for the assessment of nanoparticle drug storage capacity. It was observed that Cobalt Ferrite nano-spheres were capable of storing 46,85% of the drug in solution, while Magnetite nanoparticles stored 36,91%. Notably, regarding drug release, significant efficiency was observed at a temperature of 43°C, with 62,68% drug release for Cobalt Ferrite particles and 88,12% for Magnetite particles. In hyperthermia assays, Cobalt Ferrite particles demonstrated efficacy as hyperthermia-inducing agents, exhibiting a temperature variation of 9,2°C. The magnetic profile of the particles was confirmed using a technique quantifying saturation magnetization values. Cobalt Ferrite particles showed potential as components of a biosensor system, evidenced by their positive response when antibodies were immobilized on them. The assay involving the conjugation of Cobalt nanoparticles with immunoglobulins and their application in lateral flow tests holds promising prospects for the development of a lateral flow biosensor.
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17
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NATHAN BEZERRA DE LIMA
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Adhesion mechanism for plaster mortars with metakaolin applied to concrete blocks
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Leader : EDUARDO PADRON HERNANDEZ
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MEMBRES DE LA BANQUE :
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EDUARDO PADRON HERNANDEZ
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KLEBER GONCALVES BEZERRA ALVES
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LILIAN KÁSSIA CAVALCANTE DA SILVA DE ASSIS
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ELIANA CRISTINA BARRETO MONTEIRO
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LEONARDO BARBOSA TORRES DOS SANTOS
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Data: 8 déc. 2023
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In the present work, characteristics of the adhesion capacity of plaster mortars applied to buildings were evaluated by combining ultrasonic wave propagation testing, infrared thermography (IRT), flexural traction and adhesion tensile strength. The investigation was carried out for mortars with metakaolin incorporated by addition and partial replacement of Portland cement in proportions of 5%, 10% and 15%. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and stereoscopy analyzes were also carried out. They were used to investigate the morphological characteristics of the mortar surface. A simple theoretical model was made based on the strength of hydrogen bonds and the stoichiometric ratio SiO2/(Ca(OH)2 is used to advance a chemical approach to the adhesion capacity of plaster mortars. The results revealed that the model was useful for predicting aspects of the adhesion capacity of plaster mortars with the substrate. Furthermore, the XRD and SEM results showed the presence of important phases in the microstructures of the mortars, such as Portlandite and CSH, the adhesion resistance tests agreed with what was predicted by the model simple theoretical, where: average values similar to the reference were obtained, and the mortars prepared with the addition of metakaolin, which are superior to the corresponding adhesion strengths of the mortars prepared with cement replaced by metakaolin. The stereograms of the rupture interfaces revealed a non-homogeneous adhesion when the mortar is applied directly to the concrete substrate and homogeneous adhesion when the mortar is applied to the slab/concrete block substrate. Considering the tensile strength behavior in flexion, only the plaster mortar with 10% metakaolin incorporated presents better mechanical performance than the reference mortar. Furthermore, the propagation speed of the incident ultrasonic waves was useful in calculating the Young's modulus, which is associated with the adhesion capacity of plaster mortars. Furthermore, IRT results revealed significant water absorption by the substrate when a layer of roughcast was applied before the metakaolin plaster mortar. When plaster mortars are applied directly to the concrete substrate, there is a lower capacity to transfer water to the solid surface. The stereoscopy results showed heterogeneity in the interface area between the mortar applied directly to the concrete surface and homogeneity in the interface between the mortar and the surface of the plaster/concrete block. In conclusion, the characteristics of the ability of metakaolin plaster mortars to transfer water molecules to solid substrates.
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JOSE EWERTON DA SILVA
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AQUEOUS ELECTROSYNTHESIS OF TERNARY QUANTUM DOTS CADMIUM CALCOGENIDES
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Leader : MARCELO NAVARRO
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MEMBRES DE LA BANQUE :
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ANDERSON CAIRES DE JESUS
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EDUARDO PADRON HERNANDEZ
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LIZETH CAROLINA MOJICA SANCHEZ
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MARCELO NAVARRO
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SEVERINO ALVES JUNIOR
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Data: 12 déc. 2023
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In this study, quantum dots (QDs) of CdS, CdSe, CdTe, as well as ternary compounds of CdSxSe1-x, CdSxTe1-x and CdTexSe1-x (where x varies from 0.15 to 0.85) were synthesized by electrochemical method in a cavity cell in aqueous medium, using 3- mercaptopropionic acid (MPA) as stabilizer, pH 9 and thermal treatment of 2 hours. The electrochemical process involved a paired electrolysis, in which elemental sulfur, selenium and tellurium were reduced in a graphite powder macroelectrode, simultaneously generating S2- /Se2- ;S2- /Te2- and Te2- /Se2- ions, while a cadmium rod was oxidized, producing Cd2+ for the efficient formation of the QDs in the desired ratio. The CdSxSe1-x QDs were characterized by means of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), UV-Vis absorption and emission spectroscopies, as well as cyclic and linear voltammetric analyses. The XRD analysis revealed lattice parameters that showed a linear reduction tendency as the molar ratio of sulfide increases in the crystalline structure. The HRTEM analysis allowed the determination of the nanoparticle sizes, which were 3.94 ± 0.70 nm (CdS), 4.23 ± 1.00 nm (CdS0.5Se0.5) and 4.12 ± 0.78 nm (CdSe). The band gap energy (Egopt) of the CdSxSe1-x QDs was determined by UV-Vis absorption spectroscopy and ranged from 2.42 eV to 2.84 eV, showing an increase with sulfide addition in the structure. The same behavior was observed for the Eg Elect, determined by cyclic and linear voltammetric analyses, indicating the nanoalloy nature of the ternary QDs electrosynthesized. For the CdSxTe1-x and CdTexSe1-x QDs, characterizations were performed by means of XRD and UV-Vis absorption and emission spectroscopies. The XRD analysis of CdSxTe1-x and CdTexSe1-x also revealed lattice parameters with a linear reduction tendency as the molar ratio of selenide and sulfide increased, respectively, in the crystalline structure. The Egopt of the CdSxTe1-x and CdTexSe1-x QDs presented values from 2.29 eV to 2.84 eV, and 2.30 eV to 2.83 eV, respectively. The results obtained demonstrate that the electrochemical method used allows the preparation of mixed cadmium chalcogenides with controllable properties.
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