Efeito da Gália como aditivo de sinteriza����o em eletr��litos cer��micos �� base de céria sintetizados pelo m��todo de complexação de c��tions

Fuel cells are considered one of the most promising ways of converting electrical energy due to its high yield and by using hydrogen (as fuel) which is considered one of the most important source of clean energy for the future. Rare earths doped ceria has been widely investigated as an alternative material for the electrolyte of solid oxide fuel cells (SOFCs) due to its high ionic conductivity at low operating temperatures compared with the traditional electrolytes based on stabilized zirconia. This work investigates the effect of gallium oxide (Gallia) as a sintering aid in Eu doped ceria ceramic electrolytes since this effect has already been investigated for Gd, Sm and Y doped ceria electrolytes. The desired goal with the use of a sintering aid is to reduce the sintering temperature aiming to produce dense ceramics. In this study we investigated the effects on densification, microstructure and ionic conduction caused by different molar fraction of the dopants europium (10, 15 and 20%) and gallium oxide (0.3, 0.6 and 0.9%) in samples sintered at 1300, 1350 and 1450 0 C. Samaria (10 and 20%) doped ceria samples sintered between 1350 and 1450 ��C were used as reference. Samples were synthesized using the cation complexation method. The ceramics powders were characterized by XRF, XRD and SEM, while the sintered samples were investigated by its relative density, SEM and impedance spectroscopy. It was showed that gallia contents up to 0.6% act as excellent sintering aids in Eu doped ceria. Above this aid content, gallia addition does not promote significant increase in density of the ceramics. In Ga free samples the larger densification were accomplished with Eu 15% molar, effect expressed in the microstructure with higher grain growth although reduced and surrounded by many open pores. Relative densities greater than 95 % were obtained by sintering between 1300 and 1350 ��C against the usual range 1500 - 1600 0 C. Samples containing 10% of Sm and 0.9% of Ga reached 96% of theoretical density by sintering at 1350 0 C for 3h, a gain compared to 97% achieved with 20% of Sm and 1% of Ga co-doped cerias sintered at 1450 0 C for 24 h as described in the literature. It is found that the addition of gallia in the Eu doped ceria has a positive effect on the grain conductivity and a negative one in the grain boundary conductivity resulting in a small decrease in the total conductivity which will not compromise its application as sintering aids in ceria based electrolytes. Typical total conductivity values at 600 and 700 ��C, around 10 and 30 mS.cm -1 respectively were reached in this study. Samples with 15% of Eu and 0.9 % of Ga sintered at 1300 and 1350 ��C showed relative densities greater than 96% and total conductivity (measured at 700 ��C) between 20 and 33 mS.cm -1 . The simultaneous sintering of the electrolyte with the anode is one of the goals of research in materials for SOFCs. The results obtained in this study suggest that dense Eu and Ga co-doped ceria electrolytes with good ionic conductivity can be sintered simultaneously with the anode at temperatures below 1350 ��C, the usual temperature for firing porous anode materials

Efeito da Gália como aditivo de sinteriza����o em eletr��litos cer��micos �� base de céria sintetizados pelo m��todo de complexação de c��tions

Fuel cells are considered one of the most promising ways of converting electrical energy due to its high yield and by using hydrogen (as fuel) which is considered one of the most important source of clean energy for the future. Rare earths doped ceria has been widely investigated as an alternative material for the electrolyte of solid oxide fuel cells (SOFCs) due to its high ionic conductivity at low operating temperatures compared with the traditional electrolytes based on stabilized zirconia. This work investigates the effect of gallium oxide (Gallia) as a sintering aid in Eu doped ceria ceramic electrolytes since this effect has already been investigated for Gd, Sm and Y doped ceria electrolytes. The desired goal with the use of a sintering aid is to reduce the sintering temperature aiming to produce dense ceramics. In this study we investigated the effects on densification, microstructure and ionic conduction caused by different molar fraction of the dopants europium (10, 15 and 20%) and gallium oxide (0.3, 0.6 and 0.9%) in samples sintered at 1300, 1350 and 1450 0 C. Samaria (10 and 20%) doped ceria samples sintered between 1350 and 1450 ��C were used as reference. Samples were synthesized using the cation complexation method. The ceramics powders were characterized by XRF, XRD and SEM, while the sintered samples were investigated by its relative density, SEM and impedance spectroscopy. It was showed that gallia contents up to 0.6% act as excellent sintering aids in Eu doped ceria. Above this aid content, gallia addition does not promote significant increase in density of the ceramics. In Ga free samples the larger densification were accomplished with Eu 15% molar, effect expressed in the microstructure with higher grain growth although reduced and surrounded by many open pores. Relative densities greater than 95 % were obtained by sintering between 1300 and 1350 ��C against the usual range 1500 - 1600 0 C. Samples containing 10% of Sm and 0.9% of Ga reached 96% of theoretical density by sintering at 1350 0 C for 3h, a gain compared to 97% achieved with 20% of Sm and 1% of Ga co-doped cerias sintered at 1450 0 C for 24 h as described in the literature. It is found that the addition of gallia in the Eu doped ceria has a positive effect on the grain conductivity and a negative one in the grain boundary conductivity resulting in a small decrease in the total conductivity which will not compromise its application as sintering aids in ceria based electrolytes. Typical total conductivity values at 600 and 700 ��C, around 10 and 30 mS.cm -1 respectively were reached in this study. Samples with 15% of Eu and 0.9 % of Ga sintered at 1300 and 1350 ��C showed relative densities greater than 96% and total conductivity (measured at 700 ��C) between 20 and 33 mS.cm -1 . The simultaneous sintering of the electrolyte with the anode is one of the goals of research in materials for SOFCs. The results obtained in this study suggest that dense Eu and Ga co-doped ceria electrolytes with good ionic conductivity can be sintered simultaneously with the anode at temperatures below 1350 ��C, the usual temperature for firing porous anode materials

S��nteses e caracteriza����es de TiO2 puro, dopado e co-dopado pelo m��todo sol-gel e suas atividades fotocatal��ticas

Nanopart��culas de di��xido de tit��nio v��m sendo extensamente empregadas como fotocatalisa-dores, j�� que s��o eficientes na degrada����o de diversos poluentes. Visando a obten����o de tit��-nias com diferentes propriedades, realizaram-se s��nteses atrav��s do m��todo sol-gel, a partir da hidr��lise do tetraisoprop��xido de tit��nio (IV) TIPP e seguindo-se os princ��pios da Qu��mica Verde, dispensando-se temperaturas e press��es elevadas. Foi estudada a influ��ncia de dife-rentes par��metros, como: pH, solvente, raz��o molar ��lcool/TIPP e ordem de adi����o dos rea-gentes. Foram obtidas tit��nias na forma cristalina anat��sio, nanom��tricas, com elevadas ��reas superficiais espec��ficas e predominantemente mesoporosas. Visando-se obter tit��nias com melhores propriedades ��ticas, isto ��, capazes de sofrer a fotoativa����o pela luz vis��vel, foram sintetizadas tit��nias dopadas e co-dopadas com os metais ferro e rut��nio (Fe3+ e Ru3+) e o a-metal N (N3). A s��ntese desses materiais tamb��m foi realizada atrav��s do m��todo sol-gel, sendo a dopagem realizada durante o processo de hidr��lise. As amostras foram caracterizadas na forma de p�� por difra����o de raios-X, adsor����o-dessor����o de nitrog��nio, microscopia ele-tr��nica de varredura e espectroscopia de reflet��ncia difusa no UV-Vis��vel. A tit��nia pura a-presentou como ��nica fase cristalina o anat��sio, quando calcinada at�� 400 C, com a presen��a de tra��os de brookita. A partir de 600 C, observou-se o aparecimento da fase rutilo, que em 900C foi a ��nica fase encontrada na tit��nia. A dopagem com Ru3+dificultou a transforma����o de fase anat��sio para rutilo, ao contr��rio da dopagem com Fe3+. O processo de co-dopagem acelerou a forma����o de rutilo, que se apresentou como ��nica fase nas amostras calcinadas a 600 C. As tit��nias dopadas apresentaram uma leve diminui����o na energia de bandgap, sendo os dopantes capazes de deslocar a absor����o para o vermelho. Foram realizados testes fotoca-tal��ticos visando �� degrada����o do azocorante Reactive Yellow 145 com l��mpada de vapor de merc��rio de 125 W a fim de se comparar as atividades fotocatal��ticas das tit��nias puras, dopa-das e co-dopadas, calcinadas a 300C. De todas as tit��nias sintetizadas, a tit��nia pura foi a que melhor degradou o corante, tendo um desempenho semelhante ao do TiO2 P25, da Evo-nik

Self-referencing thermometry in the nanoscale

Na ��ultima d��ecada emergiu uma linha de investiga��c��ao muito activa em term��ometros n��ao invasivos e precisos que possam determinar temperatura `a escala nanom��etrica. Esta investiga��c��ao foi fortemente estimulada pelas numerosas solicita��c��oes da nanotecnologia e da biomedicina, por exemplo. Uma das abordagens mais promissoras prop��oe o uso de i��oes trivalentes de lantan����deos que apresenta propriedades fotoluminescentes que dependem da temperatura. Neste trabalho demonstra-se que esta t��ecnica combina as vantagens de te um limite de detec��c��ao de 0.5 graus com sensibilidade at��e 4.5 % �� K���1. Este term��ometro molecular pode ser processado em filmes finos ou nanopart����culas, abrindo os campos de aplica��c��ao a diferentes utiliza��c��oes. As nanopart����culas de s����lica produzidas s��ao caracterizadas na presen��ca e na aus��encia de i��oes lantan����deos. Sem o metal, as nanopart����culas de APTES/TEOS demonstram ser luminescentes sob excita��c��ao UV sem necessidade de utilizar qualquer tratamento t��ermico. O rendimento qu��antico de emiss��ao depende apenas da propor��c��ao dos silanos e pode atingir o valor de 0.15 �� 0.02. A co-dopagem destas nanopart����culas com Eu3+ e Tb3+ permite obter sondas com resposta raciom��etrica, com a possibilidade de ajustar a gama de temperaturas de opera��c��ao e a sensibilidade, via desenho inteligente da matriz de suporte e dos ligandos de ��-dicetona que est��ao coordenados ao i��ao met��alico. Quando processados como filmes, este term��ometro permite o mapeamento de temperaturas com resolu��c��ao espacial 1.8 ��m. A racionaliza��c��ao da depend��encia de temperatura ��e uma ferramenta ��util para desenvolver term��ometros que operam em gamas de temperatura espec����ficos (e.g. gama de temperatura fisiol��ogica, 290-340 K) com sensibilidade acima de 0.5 % �� K���1. A combina��c��ao de esfor��cos de um grande n��umero de diversas disciplinas ir��a previsivelmente permitir o surgimento de term��ometros moleculares novos e sofisticados, preenchendo os principais requisitos das nanociencias.

Desenvolvimento de redes de pol��meros interpenetrantes (IPN) para a aplica����o como eletr��lito polim��rico

Uma nova rede de pol��meros interpenetrantes (IPN) baseada em poliuretana de ��leo de mamona e poli(etileno glicol) e poli(metacrilato de metila) foi preparada para ser utilizada como eletr��lito polim��rico. Os seguintes par��metros de polimeriza����o foram avaliados: massa molecular do poli(etileno glicol) (PEG), concentra����o de PEG e concentra����o de metacrilato de metila. As membranas de IPN foram caracterizadas por calorimetria diferencial de varredura (DSC) e espectroscopia de infravermelho por transformada de Fourier (FT-IR). Os eletr��litos de redes de pol��meros interpenetrantes (IPNE) foram preparados a partir da dopagem com sal de l��tio atrav��s do inchamento numa solu����o de 10% em massa de LiClO4 na mistura de carbonato de etileno e carbonato de propileno na raz��o m��ssica de 50:50. As IPNEs foram caracterizadas por espectroscopia de impedância eletroqu��mica e Raman. As IPNEs foram testadas como eletr��lito polim��rico em supercapacitores. As c��lulas capacitivas foram preparadas utilizando eletrodos de polipirrol (PPy). Os valores de capacit��ncia e efici��ncia foram calculados por impedância eletroqu��mica, voltametria c��clica e ciclos galvonost��ticos de carga e descarga. Os valores de capacit��ncia obtidos foram em torno de 90 F.g-1 e efici��ncia variou no intervalo de 88 a 99%. Os valores de densidade de pot��ncia foram superiores a 250 W.kg-1 enquanto que a densidade de energia variou de 10 a 33 W.h.kg-1, dependendo da composi����o da IPNE. As caracter��sticas eletroqu��micas do eletr��lito formado pela IPN-LiClO4 (IPNE) foram comparadas aos eletr��litos polim��ricos convencionais, tais como poli(difluoreto de vinilideno)-(hexafluorpropileno) ((PVDF-HFP/LiClO4) e poliuretana comercial (Bayer��� desmopan 385) (PU385/LiClO4). As condutividades na temperatura ambiente foram da ordem de 10-3 S.cm-1. A capacit��ncia da c��lula utilizando eletrodos de PPy com eletr��lito de PVDFHFP foi de 115 F.g-1 (30 mF.cm-2) e 110 F.g-1 (25 mF.cm-2) para a c��lula com PU385 comparadas a 90 F.g-1 (20 mF.cm-2) para a IPNE. Os capacitores preparados com eletr��lito de IPNE apresentaram valores de capacit��ncia inferior aos demais, entretanto provaram ser mais est��veis e mais resistentes aos ciclos de carga/descarga. A interpenetra����o de duas redes polim��ricas, PU e PMMA produziu um eletr��lito com boa estabilidade mec��nica e el��trica. Um prot��tipo de supercapacitor de estado s��lido foi produzindo utilizando eletrodos impressos de carbono ativado (PCE) e o eletr��lito polim��rico de IPNE. A t��cnica de impress��o de carbono possui v��rias vantagens em rela����o aos outros m��todos de manufatura de eletrodos de carbono, pois a ��rea do eletrodo, espessura e composi����o s��o vari��veis que podem ser controladas experimentalmente. As c��lulas apresentaram uma larga janela eletroqu��mica (4V) e valores da capacit��ncia da ordem de 113 mF.cm-2 (16 F.g-1). M��todos alternativos de prepara����o do PCE investigados incluem o uso de IPNE como pol��mero de liga����o ao carbono ativado, estes eletrodos apresentaram valores de capacit��ncia similares aos produzidos com PVDF. A influ��ncia do n��mero de camadas de carbono usadas na produ����o do PCE tamb��m foi alvo de estudo. Em rela����o ao eletr��lito polim��rico, o plastificante e o sal de l��tio foram adicionados durante a s��ntese, formando a IPNGel. As c��lulas apresentaram alta capacit��ncia e boa estabilidade ap��s 4000 ciclos de carga e descarga. As membranas de IPN foram testadas tamb��m como reservat��rio de medicamento em sistemas de transporte transd��rmico por iontoforese. Os filmes, mecanicamente est��veis, formaram g��is quando inchado em solu����es saturadas de lidocaina.HCl, anest��sico local, em propileno glicol (PG), poli(etileno glicol) (PEG400) e suas misturas. O grau de inchamento em PG foi de 15% e 35% em PEG400. Agentes qu��micos de penetra����o foram utilizados para diminuir a resist��ncia da barreira causada pela pele, dentre eles o pr��prio PG, a 2-pirrolidinona (E1) e a 1-dodecil-2-pirrolidinona (E2). Os g��is foram caracterizados por espectroscopia de impedância eletroqu��mica e transporte passivo e por iontoforese atrav��s de uma membrana artificial (celofane). O sistema IPN/ lidocaina.HCl apresentou uma correla����o linear entre medicamento liberado e a corrente aplicada. Os melhores resultados de transporte de medicamento foram obtidos utilizando o PG como solvente.

S��ntese e caracteriza����o de NiO-CGO para anodo e eletr��litos s��lidos e base de Céria para SOFC

The direct use of natural gas makes the Solid Oxide Fuel Cell (SOFC) potentially more competitive with the current energy conversions technologies. The Intermediate Temperature SOFC (IT-SOFC) offer several advantages over the High Temperature SOFC (HT-SOFC), which includes better thermal compatibility among components, fast start with lower energy consumption, manufacture and operation cost reduction. The CeO2 based materials are alternatives to the Yttria Stabilized Zirconia (YSZ) to application in SOFC, as they have higher ionic conductivity and less ohmic losses comparing to YSZ, and they can operate at lower temperatures (500-800��C). Ceria has been doped with a variety of cations, although, the Gd3+ has the ionic radius closest to the ideal one to form solid solution. These electrolytes based in ceria require special electrodes with a higher performance and chemical and termomechanical compatibility. In this work compounds of gadolinia-doped ceria, Ce1-xGdxO2-δ (x = 0,1; 0,2 and 0,3), used as electrolytes, were synthesized by polymeric precursors method, Pechini, as well as the composite material NiO - Ce0,9Gd0,1O1,95, used as anode, also attained by oxide mixture method, mixturing the powders of the both phases calcinated already. The materials were characterized by X ray diffraction, dilatometry and scanning electronic microscopy. The refinement of the diffraction data indicated that all the Ce1-xGdxO2-δ powders were crystallized in a unique cubic phase with fluorite structure, and the composite synthesized by Pechini method produced smaller crystallite size in comparison with the same material attained by oxide mixture method. All the produced powders had nanometric characteristics. The composite produced by Pechini method has microstructural characteristics that can increase the triple phase boundaries (TPB) in the anode, improving the cell efficiency, as well as reducing the mass transport mechanism effect that provokes anode degradation

Sinteriza����o de Ce1-XEuXO2-(X/2) para aplica����o como eletr��lito s��lido em c��lulas a combust��vel de temperaturas intermedi��rias

Given the environmental concern over global warming that occurs mainly by emission of CO2 from the combustion of petroleum, coal and natural gas research focused on alternative and clean energy generation has been intensified. Among these, the highlight the solid oxide fuel cell intermediate temperature (IT-SOFC). For application as electrolyte of the devices doped based CeO2 with rare earth ions (TR+ 3) have been quite promising because they have good ionic conductivity and operate at relatively low temperatures (500-800 �� C). In this work, studied the Ce1-xEuxO2-δ (x = 0,1, 0,2 and 0,3), solid solutions synthesized by the polymeric precursor method to be used as solid electrolyte. It was also studied the processing steps of these powders (milling, compaction and two step sintering) in order to obtain dense sintered pellets with reduced grain size and homogeneous microstructure. For this, the powders were characterized by thermal analysis, X-ray diffraction, particle size distribution and scanning electrons microscopy, since the sintered samples were characterized by dilatometry, scanning electrons microscopy, density and grain size measurements. By x-ray diffraction, it was verified the formation of the solid solution for all compositions. Crystallites in the nanometric scale were found for both sintering routes but the two step sintering presented significant reduction in the average grain size

Investiga����o da estabilidade t��rmica e das propriedades el��tricas do TiO2 em fun����o da dopagem com Ce(SO4)2

The metalic oxides have been studies due to differents applications as materials semiconductor in solar cells, catalysts, full cells and, resistors. Titanium dioxide (TiO2) has a high electric conductivity due to oxygen vacancies. The Ce(SO4)2.2H2O doped samples TiO2 and TiO2 pure was obtained sol-gel process, and characterized by X-ray diffractometry,thermal analysis, and impedance spectroscopy. The X-ray diffraction patterns for TiO2 pure samples shows at 700��C anatase phase is absent, and only the diffraction peaks of rutile phase are observed. However, the cerium doped samples only at 900��C rutile in the phase present with peaks of cerium dioxide (CeO2). The thermal analysis of the TiO2 pure and small concentration cerium doped samples show two steps weight loss corresponding to water of hydration and chemisorbed. To larger concentration cerium doped samples were observed two steps weight loss in the transformation of the doped cerium possible intermediate species and SO3. Finally, two steps weight loss the end products CeO2 and SO3 are formed. Analyse electric properties at different temperatures and concentration cerium doped samples have been investigated by impedance spectroscopy. It was observed that titanium, can be substituted by cerium, changing its electric properties, and increased thermal stability of TiO2 anatase structure

S��ntese e caracteriza����o de c��todos de perovskitas 'La IND.0,6''Sr IND.0,4''Fe IND.y''Co IND.1-y''O IND.3-'delta'', para c��lulas a combust��vel de eletr��lito s��lido (SOFC) operando em temperaturas intermedi��rias

Conselho Nacional de Desenvolvimento Cient��fico e Tecnol��gico (CNPq)

Estudo da corros��o de a��os de elevado limite el��stico e das suas uni��es com metais duros ou cermet e com a��o/WC-Co em 'NA''CL' 0,6 mol 'L POT. -1'

Coordena����o de Aperfei��oamento de Pessoal de N��vel Superior (CAPES)

Filmes de 'CO' obtidos por deslocamento galv��nico e suas propriedades magn��ticas

P��s-gradua����o em Qu��mica - IQ

Filmes de 'CO' obtidos por deslocamento galv��nico e suas propriedades magn��ticas

P��s-gradua����o em Qu��mica - IQ

Cimentos injet��veis �� base de fosfatos de c��lcio para vertebroplastia

O principal objectivo desta investiga����o foi o desenvolvimento cimentos de fosfatos de c��lcio com injetabilidade melhorada e propriedades mec��nicas adequadas para aplica����o em vertebroplastia. Os p��s de fosfato de tric��lcico (TCP) n��o dopados e dopados (Mg, Sr e Mn) usados neste estudo foram obtidos pelo processo de precipita����o em meio aquoso, seguidos de tratamento t��rmico de forma a obter as fases pretendidas, ����� e �����TCP. A substitui����o parcial de i��es Ca por i��es dopantes mostrou ter implica����es em termos de estabilidade t��rmica da fase �����TCP. Os resultados demonstraram que as transforma����es de fase alotr��picas ����������TCP s��o fortemente influenciadas por vari��veis experimentais como a taxa de arrefecimento, a presen��a de impurezas de pirofosfato de c��lcio e a extens��o do grau de dopagem com Mg. Os cimentos foram preparados atrav��s da mistura de p��s, �����TCP (n��o dopados e dopados) e fosfato monoc��lcico monidratado (MCPM), com meios l��quidos diferentes usando ��cido c��trico e a��ucares (sucrose e frutose) como agentes retardadores de presa, e o polietilenoglicol, a hidroxipropilmetilcelulose e a polivinilpirrolidona como agentes gelificantes. Estes aditivos, principalmente o ��cido c��trico, e o MCPM aumentam significativamente a for��a i��nica do meio, influenciando a injetabilidade das pastas. Os resultados tamb��m mostraram que a distribui����o de tamanho de part��cula dos p��s �� um factor determinante na injetabilidade das pastas ciment��cias. A combina����o da co-dopagem de Mn e Sr com a adi����o de sucrose no l��quido de presa e com uma distribui����o de tamanho de part��cula dos p��s adequada resultou em cimentos de brushite com propriedades bastante melhoradas em termos de manuseamento, microestrutura, comportamento mec��nico e biol��gico: (i) o tempo inicial de presa passou de ~3 min to ~9 min; (ii) as pastas ciment��cias foram totalmente injectadas para uma raz��o liquido/p�� de 0.28 mL g���1 com aus��ncia do efeito de ���filter-pressing��� (separa����o de fases l��quida e s��lida); (iii) ap��s imers��o numa solu����o durante 48 h, as amostras de cimento molhadas apresentam uma porosidade total de ~32% e uma resist��ncia a compress��o de ~17 MPa, valor muito superior ao obtido para os cimentos sem a����car n��o dopados (5 MPa) ou dopados s�� com Sr (10 MPa); e (iv) o desempenho biol��gico, incluindo a ades��o e crescimento de c��lulas osteobl��sticas na superf��cie do cimento, foi muito melhorado. Este conjunto de propriedades torna os cimentos excelentes para regenera����o ��ssea e engenharia de tecidos, e muito promissores para aplica����o em vertebroplastia.

S��ntese e caracteriza����o de NiO-CGO para anodo e eletr��litos s��lidos e base de Céria para SOFC

The direct use of natural gas makes the Solid Oxide Fuel Cell (SOFC) potentially more competitive with the current energy conversions technologies. The Intermediate Temperature SOFC (IT-SOFC) offer several advantages over the High Temperature SOFC (HT-SOFC), which includes better thermal compatibility among components, fast start with lower energy consumption, manufacture and operation cost reduction. The CeO2 based materials are alternatives to the Yttria Stabilized Zirconia (YSZ) to application in SOFC, as they have higher ionic conductivity and less ohmic losses comparing to YSZ, and they can operate at lower temperatures (500-800��C). Ceria has been doped with a variety of cations, although, the Gd3+ has the ionic radius closest to the ideal one to form solid solution. These electrolytes based in ceria require special electrodes with a higher performance and chemical and termomechanical compatibility. In this work compounds of gadolinia-doped ceria, Ce1-xGdxO2-δ (x = 0,1; 0,2 and 0,3), used as electrolytes, were synthesized by polymeric precursors method, Pechini, as well as the composite material NiO - Ce0,9Gd0,1O1,95, used as anode, also attained by oxide mixture method, mixturing the powders of the both phases calcinated already. The materials were characterized by X ray diffraction, dilatometry and scanning electronic microscopy. The refinement of the diffraction data indicated that all the Ce1-xGdxO2-δ powders were crystallized in a unique cubic phase with fluorite structure, and the composite synthesized by Pechini method produced smaller crystallite size in comparison with the same material attained by oxide mixture method. All the produced powders had nanometric characteristics. The composite produced by Pechini method has microstructural characteristics that can increase the triple phase boundaries (TPB) in the anode, improving the cell efficiency, as well as reducing the mass transport mechanism effect that provokes anode degradation

Sinteriza����o de Ce1-XEuXO2-(X/2) para aplica����o como eletr��lito s��lido em c��lulas a combust��vel de temperaturas intermedi��rias

Given the environmental concern over global warming that occurs mainly by emission of CO2 from the combustion of petroleum, coal and natural gas research focused on alternative and clean energy generation has been intensified. Among these, the highlight the solid oxide fuel cell intermediate temperature (IT-SOFC). For application as electrolyte of the devices doped based CeO2 with rare earth ions (TR+ 3) have been quite promising because they have good ionic conductivity and operate at relatively low temperatures (500-800 �� C). In this work, studied the Ce1-xEuxO2-δ (x = 0,1, 0,2 and 0,3), solid solutions synthesized by the polymeric precursor method to be used as solid electrolyte. It was also studied the processing steps of these powders (milling, compaction and two step sintering) in order to obtain dense sintered pellets with reduced grain size and homogeneous microstructure. For this, the powders were characterized by thermal analysis, X-ray diffraction, particle size distribution and scanning electrons microscopy, since the sintered samples were characterized by dilatometry, scanning electrons microscopy, density and grain size measurements. By x-ray diffraction, it was verified the formation of the solid solution for all compositions. Crystallites in the nanometric scale were found for both sintering routes but the two step sintering presented significant reduction in the average grain size