Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-03-31T22:25:53Z No. of bitstreams: 1 CarolineGomesMoura_DISSERT.pdf: 2102873 bytes, checksum: c954d6aaea1a58ccd102a726f8bae793 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-04-01T23:05:31Z (GMT) No. of bitstreams: 1 CarolineGomesMoura_DISSERT.pdf: 2102873 bytes, checksum: c954d6aaea1a58ccd102a726f8bae793 (MD5) / Made available in DSpace on 2016-04-01T23:05:31Z (GMT). No. of bitstreams: 1 CarolineGomesMoura_DISSERT.pdf: 2102873 bytes, checksum: c954d6aaea1a58ccd102a726f8bae793 (MD5) Previous issue date: 2015-06-25 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / O PSFC (Pr0.5Sr0.5Fe1-xCuxO3-?) ? um novo ?xido misto com estrutura perovskita que vem sendo estudado para aplica??o como catodo de c?lulas a combust?vel de ?xido s?lido de temperatura intermedi?ria (600-750 ?C), principalmente devido a sua elevada condutividade i?nica e eletr?nica abaixo de 800 ?C. Neste trabalho, p?s de PSFC com duas composi??es diferentes (Pr0,5Sr0,5Fe0,8Cu0,2O3-PSFC5582 e Pr0,5Sr0,5Fe0,6Cu0,4O3-PSFC5564) foram sintetizados pelo m?todo dos citratos utilizando uma nova rota. Os p?s obtidos foram caracterizados por an?lise t?rmica (Termogravimetria e Calorimetria Diferencial Explorat?ria), e os materiais calcinados a 800, 900 e 1000 ?C por 5h foram analisados por difratometria de raios X (DRX), com refinamento Rietveld dos dados de difra??o e dilatometria. Filmes de composi??o PSFC5582 foram obtidos por serigrafia do p? calcinado a 1000 ?C. Os filmes foram depositados em substrato de c?ria dopada com gadol?nia (CGO) e sinterizados a 1050 ?C por 2h. O desempenho eletroqu?mico dos eletrodos foi avaliado por espectroscopia de imped?ncia e a interface eletrodo/eletr?lito foi observada por microscopia eletr?nica de varredura (MEV). A resist?ncia espec?fica por ?rea (ASR) foi 0,44 ?.cm? a 800 ?C, um valor pouco inferior aos reportados na literatura para catodos contendo cobalto. Os coeficientes de expans?o t?rmica (CET) do PSFC de ambas as composi??es variaram entre 13 e 15 x 10-6 ?C-1 , numa faixa de temperatura de 200 a 650 ?C, demonstrando a boa compatibilidade t?rmica destes catodos com eletr?litos de Ce0,9Gd0,1O1,95 (CET = 12 x 10-6 ?C). / The PSFC (Pr0.5Sr0.5Fe1-xCuxO3-?) is a new mixed oxide perovskite and has been studied and evaluated the cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs), mainly due to its good compatibility with the electrolyte (CGO) and its high ionic conductivity and electronic in intermediate temperature. In this work, PSFC powders with two different compositions (Pr0,5Sr0,5Fe0,8Cu0,2O3- PSFC5582 and Pr0,5Sr0,5Fe0,6Cu0,4O3-PSFC5564) were synthesized by the citrate method using a new route. The powders obtained were characterized by thermal analysis (Differential Scanning Calorimetry and Thermogravimetry), and the material calcined at 800, 900 and 1000 ?C for 5h were analyzed by X-ray diffractometry (XRD), with the Rietveld refinement of the diffraction data and dilatometry. PSFC5582 composite films were obtained by screen printing of powder calcined at 1000 ?C. The films were deposited on substrate ceria doped with gadolinia (CGO) and then sintered at 1050 ?C for 2h. The electrochemical performance of the electrodes was evaluated by impedance spectroscopy and the interface electrode/electrolyte was observed by scanning electron microscopy (SEM). The specific resistance area (ASR) was 0.44 ?.cm? at 800 ?C, slightly lower than those reported in the literature for cathodes containing cobalt. The thermal expansion coefficients of both the PSFC compositions were obtained and varied between 13 and 15 x 10-6 ?C-1 , in a temperature range of 200 to 650 ?C, demonstrating the good thermal compatibility of cathodes with Ce0,9Gd0,1O1,95 electrolytes (CET = 12 x 10-6 ?C).

Made available in DSpace on 2014-12-17T14:07:09Z (GMT). No. of bitstreams: 1 AmandaLM_DISSERT.pdf: 3676559 bytes, checksum: 256cb3ce22bbf3b5f114a2ff3021de96 (MD5) Previous issue date: 2013-02-06 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Fuel cells are electrochemical devices that convert chemical energy into electricity. Due to the development of new materials, fuel cells are emerging as generating clean energy generator. Among the types of fuel cells, categorized according to the electrode type, the solid oxide fuel cells (SOFC) stand out due to be the only device entirely made of solid particles. Beyond that, their operation temperature is relatively high (between 500 and 1000 ?C), allowing them to operate with high efficiency. Another aspect that promotes the use of SOFC over other cells is their ability to operate with different fuels. The CeO2 based materials doped with rare earth (TR+3) may be used as alternatives to traditional NiO-YSZ anodes as they have higher ionic conductivity and smaller ohmic losses compared to YSZ, and can operate at lower temperatures (500-800?C). In the composition of the anode, the concentration of NiO, acting as a catalyst in YSZ provides high electrical conductivity and high electrochemical activity of reactions, providing internal reform in the cell. In this work compounds of NiO - Ce1-xEuxO2-δ (x = 0.1, 0.2 and 0.3) were synthesized from polymeric precursor, Pechini, method of combustion and also by microwave-assisted hydrothermal method. The materials were characterized by the techniques of TG, TPR, XRD and FEG-SEM. The refinement of data obtained by X-ray diffraction showed that all powders of NiO - Cex-1EuxO2-δ crystallized in a cubic phase with fluorite structure, and also the presence of Ni. Through the characterizations can be proved that all routes of preparation used were effective for producing ceramics with characteristics suitable for application as SOFC anodes, but the microwave-assisted hydrothermal method showed a significant reduction in the average grain size and improved control of the compositions of the phases / C?lulas a combust?vel s?o dispositivos eletroqu?micos que convertem a energia qu?mica em el?trica. Em virtude do desenvolvimento de novos materiais, as c?lulas a combust?vel v?m se destacando como promissores na gera??o de energia de forma limpa. Dentre os tipos de c?lulas a combust?vel, classificadas de acordo com o tipo de eletr?lito, destacam-se as de ?xido s?lido (SOFC), por serem as ?nicas inteiramente constitu?das por s?lidos. Al?m disso, pela sua temperatura de opera??o ser relativamente elevada (entre 500 e 1000 ?C), estas c?lulas operam com alta efici?ncia. Outro aspecto que favorece o emprego de SOFC ? a sua habilidade de operar com diferentes combust?veis, como fontes de hidrog?nio.Os materiais a base de CeO2 dopados com terras raras (TR+3) podem ser utilizados como alternativas aos tradicionais anodos de NiO-YSZ. Al?m de maior condutividade i?nica maior e menores perdas ?hmicas, elas podem operar a temperaturas mais baixas (500- 800?C). Na composi??o do anodo, a concentra??o de NiO, atuando como catalisador confere alta condutividade el?trica e alta atividade eletroqu?mica das rea??es, proporcionando a reforma interna do combust?vel na c?lula. Neste trabalho compostos de NiO - Ce1-xEuxO2-δ (x = 0,1; 0,2 e 0,3), foram sintetizados a partir do m?todo dos precursores polim?ricos, Pechini, do m?todo de combust?o e, tamb?m, pelo m?todo hidrotermal assistido por micro-ondas. Os materiais obtidos foram caracterizados atrav?s das t?cnicas de TG, DRX, TPR e MEV-FEG. O refinamento dos dados obtidos pela difra??o de raios X indicou que todos os p?s de NiO - Ce1- xEuxO2-δ cristalizaram-se em uma fase c?bica com estrutura fluorita, e tamb?m a presen?a de NiO. Todas as rotas de prepara??o utilizadas mostraram-se eficientes para a produ??o de p?s com caracter?sticas adequadas para aplica??o como anodos de SOFC, por?m o m?todo hidrotermal assistido por micro-ondas apresentou significativa redu??o do tamanho m?dio de gr?os e melhor controle das composi??es das fases