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Previous issue date: 2012-11-13 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Alternative and clean energy generation research has been intensified in last decades. Among the alternatives, fuel cells are one of the most important. There are different types of fuel cells, among which stands out intermediate temperature solid oxide fuel cell (IT-SOFC) matter of the present work. For application as cathode on this type of devices, the ceramic Ba0.5Sr0.5C0.8Fe0.2O3-? doped with rare earth ions (Nd, Sm) have been quite promising because they show good ionic conductivity and operate at relatively low temperatures (500 - 800?C). In this work, Ba0.5Sr0.5Co0.8Fe0.2O3-?, (BaSr)0.5Sm0.5Co0.8Fe0.2O3-? and (BaSr)0.5Nd0.5C0.8Fe0.2O3-? were obtained by modified Pechini method, making use of gelatin as polymerizing agent. The powders were characterized by X-Ray Diffraction (XRD), Temperature Programmed Reduction (TPR) and Scanning Electron Microscopy (SEM). The perovskite phase was observed in all X-ray patterns for the materials Ba0.5Sr0.5C0.8Fe0.2O3-? doped with rare earth ions (Nd, Sm). The SEM images showed that the materials have a characteristics porous, with very uniform pore distribution, which are favorable for application as cathodes. Subsequently, screen-printed assymmetrical cells were studied by impedance spectroscopy, to assess the kinetics of the cathode for the reduction reaction of oxygen. The best resistance to the specific area was found for the cathode BSSCF sintered at 1050 ?C for 4 hours with around 0.15 ?.cm2 at 750 ?C as well as cathodes BSNCF and BSCF obtained resistances specific area of 0.2 and 0.73 ?.cm2, respectively, for the same conditions. The polarization curves showed similar behavior to the best cathodes BSSCF and BSNCF, such combination of properties indicates that the film potentially depict good performance as IT-SOFC cathodes / Pesquisas voltadas para formas alternativas e n?o poluentes de gera??o de energia que v?m se intensificando. Entre essas, destacam-se as c?lulas a combust?vel de ?xido s?lido de temperatura intermedi?ria (IT-SOFC). Para aplica??o como catodo deste tipo de dispositivo, os ?xidos cer?micos Ba0,5Sr0,5C0,8Fe0,2O3-? dopadas com ?ons de terras raras (Nd, Sm) t?m se mostrado bastante promissores pelo fato de possu?rem boa condutividade i?nica e operarem em temperaturas relativamente baixas (500-800?C). Neste trabalho, Ba0,5Sr0,5C0,8Fe0,2O3-? (BSCF), (BaSr)0,5Sm0,5C0,8Fe0,2O3-? (BSSCF) e (BaSr)0,5 Nd0,5C0,8Fe0,2O3-? (BSNCF) foram obtidos pelo m?todo Pechini modificado, fazendo uso de gelatina que atua como agente polimerizante e coordenante. Os p?s obtidos foram caracterizados por Difra??o de Raios X (DRX), Redu??o ? Temperatura Programada (RTP) e Microscopia Eletr?nica de Varredura (MEV) e Microscopia Eletr?nica de Transmiss?o (MET). A fase perovsquita foi evidenciada em todos os difratogramas de raios X nos ?xidos Ba0,5Sr0,5C0,8Fe0,2O3-? dopados com ?ons de terras raras (Nd, Sm). As imagens de MEV evidenciaram que o p? obtido ? poroso, o que favorece seu uso como c?todos. Posteriormente, foram preparadas c?lulas assim?tricas por screen-pritting para estudos de microestrutura e de espectroscopia de imped?ncia, a fim de avaliar a cin?tica de c?todo da rea??o de redu??o do oxig?nio no c?todo. A melhor resist?ncia ? ?rea espec?fica foi encontrada para o c?todo BSSCF sinterizado a 1050 ?C durante 4 horas com 0,15 ?.cm2 na temperatura de 750?C, bem como os c?todos BSNCF e BSCF obtiveram resist?ncias ? ?rea espec?fica de 0,20 e 0,73 ?.cm2 , respectivamente, para as mesmas condi??es. As curvas de polariza??o demonstraram comportamentos semelhantes aos melhores c?todos BSSCF e BSNCF, sendo assim, adequados para aplica??o como material cat?dico nas SOFC
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/12800 |
| Date | 13 November 2012 |
| Creators | Aquino, Fl?via de Medeiros |
| Contributors | CPF:06117988320, http://lattes.cnpq.br/3318871716111536, Martinelli, Ant?nio Eduardo, CPF:15724520800, http://lattes.cnpq.br/0022988322449627, Teixeira, Leonardo Sena Gomes, CPF:67108059568, http://lattes.cnpq.br/5061261000226463, Pontes, Luiz Antonio Magalh?es, CPF:65440587772, http://lattes.cnpq.br/2865282329757428, Braga, Renata Martins, CPF:05165674460, http://lattes.cnpq.br/4603529162393328, Melo, Dulce Maria de Ara?jo |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Ci?ncia e Engenharia de Materiais, UFRN, BR, Processamento de Materiais a partir do P?; Pol?meros e Comp?sitos; Processamento de Materiais a part |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/embargoedAccess |
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