Made available in DSpace on 2014-12-17T15:42:20Z (GMT). No. of bitstreams: 1 AdilaPGR_DISSERT.pdf: 1981953 bytes, checksum: be68a9256a00a195734cb22cb0bdc5b2 (MD5) Previous issue date: 2014-12-11 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The ferrite composition Ni1 - xCoxFe2O4 (0 ≤ x ≤ 0.75) were obtained by the method of microwave assisted synthesis and had their structural and magnetic properties evaluated due to the effect of the substitution of Ni by Co. The compounds were prepared: according to the concept of chemical propellants and heated in the microwave oven with power 7000kw. The synthesized material was characterized by absorption spectroscopy in the infrared (FTIR), Xray diffraction (XRD) using the Rietveld refinement, specific surface area (BET) , scanning electron microscopy (SEM) with aid of energy dispersive analysis (EDS) and magnetic measurements (MAV). The results obtained from these techniques confirmed the feasibility of the method of synthesis employed to obtain the desired spinel structure, the ferrite, nickel ferrite as for nickel doped with cobalt. The results from XRD refinement ally showed the formation of secondary phases concerning stages α - Fe2O3, FeO, (FeCo)O e Ni0. On the other hand, there is an increase in crystallite size with the increase of cobalt in systems, resulting in an increased crystallinity. The results showed that the BET systems showed a reduction in specific surface area with the increase of cobalt and from the SEM, the formation of irregular porous blocks and that the concentration of cobalt decreased the agglomerative state of the system. The magnetic ferrites studied showed different characteristics according to the amount of dopant used, ranging from a very soft magnetic material (easy magnetization and demagnetization ) - for the system without cobalt - a magnetic material with a little stiffer behavior - for systems containing cobalt. The values of the coercive field increased with the increasing growth of cobalt, and the values of saturation magnetization and remanence increased up to x = 0,25 and then reduced. The different magnetic characteristics presented by the systems according to the amount of dopant used, allows the use of these materials as intermediates magnetic / As ferritas de composi??o Ni1−xCoxFe2O4 (0≤x≤0,75) foram obtidas atrav?s do m?todo de s?ntese assistida por microondas e tiveram suas propriedades estruturais e magn?ticas avaliadas em fun??o do efeito da substitui??o do Ni pelo Co. Os compostos foram preparados de acordo com o conceito da qu?mica dos propelentes e aquecidos em forno micro-ondas com pot?ncia 7000kw. O material sintetizado foi caracterizado por espectroscopia de absor??o na regi?o do infravermelho (FTIR), difra??o de raios X (DRX), com o uso do refinamento pelo m?todo de Rietveld, ?rea superficial espec?fica (BET), microscopia eletr?nica de varredura (MEV) com aux?lio de an?lise por dispers?o de energia (EDS) e medidas magn?ticas (MAV). Os resultados obtidos, a partir destas t?cnicas confirmaram a viabilidade do m?todo de s?ntese empregado para a obten??o da estrutura espin?lio desejada, tanto para a ferrita de n?quel quanto para as ferritas de n?quel dopadas com cobalto. Os resultados do DRX, aliado ao refinamento, mostraram a forma??o de fases secund?rias tais como as fases α - Fe2O3, FeO, (FeCo)O e Ni0. Por outro lado, observou-se um aumento no tamanho do cristalito com o incremento do cobalto nos sistemas, implicando em um aumento da cristalinidade. Os resultados do BET mostraram que os sistemas apresentaram uma redu??o da ?rea superficial espec?fica com o incremento do cobalto e a partir do MEV observou-se a forma??o de blocos porosos irregulares e que o aumento da concentra??o de cobalto dimunuiu o estado de aglomera??o dos sistemas. As ferritas estudadas apresentaram caracter?sticas magn?ticas diferenciadas de acordo com a quantidade do dopante utilizado, variando de um material magn?tico bastante mole (f?cil magnetiza??o e desmagnetiza??o) - para o sistema sem cobalto - a um material magn?tico com comportamento um pouco mais duro - para os sistemas contendo cobalto. Os valores do campo coercitivo aumentaram com o crescente incremento do cobalto, e os valores de magnetiza??o de satura??o e reman?ncia aumentaram at? x=0,25 e depois reduziram. As caracter?sticas magn?ticas diferenciadas apresentadas pelos sistemas, de acordo com a quantidade de dopante utilizado, permite o uso desses materiais como magn?ticos intermedi?rios

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-12-01T23:25:10Z No. of bitstreams: 1 GrazieleLopesDeSouza_DISSERT.pdf: 2319933 bytes, checksum: 41ca637533facb729220921e1dc4c6ce (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-12-05T20:18:40Z (GMT) No. of bitstreams: 1 GrazieleLopesDeSouza_DISSERT.pdf: 2319933 bytes, checksum: 41ca637533facb729220921e1dc4c6ce (MD5) / Made available in DSpace on 2017-12-05T20:18:40Z (GMT). No. of bitstreams: 1 GrazieleLopesDeSouza_DISSERT.pdf: 2319933 bytes, checksum: 41ca637533facb729220921e1dc4c6ce (MD5) Previous issue date: 2017-01-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / As c?lulas a combust?vel de ?xido s?lido s?o os dispositivos mais eficientes at? ent?o inventados para a convers?o de combust?veis qu?micos diretamente em energia el?trica. Estes dispositivos ainda apresentam como desvantagem o funcionamento em temperatura relativamente elevada. Catodos da s?rie La2-xNiO4+d com estrutura K2NiF4 t?m se mostrado promissores condutores mistos a temperaturas intermedi?rias. O interesse por estes ?xidos como material funcional para catodo deve-se principalmente ? sua permeabilidade a oxig?nio e sua estabilidade qu?mica e t?rmica. Este material tem coeficiente de expans?o t?rmica compat?vel com eletr?litos pertencentes a fam?lia La10-x(SiO4)6O2+-d com estrutura apatita. Estes eletr?litos t?m condutividades superiores aos eletr?litos ? base de zirc?nia, se utilizados na mesma faixa de temperatura que o catodo acima citado. Este trabalho reporta a s?ntese de p?s de silicato de lant?nio tipo apatita de composi??o La10Si6O27 e niquelato de lant?nio (La2NiO4) para serem usados como materiais de eletr?lito e catodo, respectivamente, em c?lulas a combust?vel de ?xido s?lido. O silicato de lant?nio foi obtido a partir de uma rota qu?mica de co-precipita??o, enquanto o catodo foi obtido pelo m?todo do citrato. O procedimento de s?ntese proposto neste trabalho para a obten??o do material de eletr?lito ? vantajoso por reduzir o consumo de energia e o tempo de processamento, elementos chaves para reduzir o custo total de manufatura. Ao termino das s?nteses os p?s precursores foram caracterizados por an?lise termogravim?trica. Os p?s de silicato de lant?nio foram calcinados entre 500 e 900 ?C e caracterizados por difratometria de raios X com refinamento Rietveld dos dados de difra??o e microscopia eletr?nica de varredura (MEV). O niquelato de lant?nio foi calcinado em uma ?nica temperatura, 1200 ?C, por 4h e caracterizado por MEV. A caracteriza??o estrutural do eletr?lito indicou a forma??o de material com fase secund?ria ap?s calcina??o a 900 ?C. O efeito da temperatura de sinteriza??o, variada entre 1400 a 1450 ?C, nas propriedades el?tricas foram investigados por espectroscopia de imped?ncia entre 400 e 800 ?C em atmosfera de ar. O eletr?lito de silicato de lant?nio sinterizado a 1450 ?C apresentou condutividade el?trica total de 2,12x10-3 S.cm-1 a 700 ?C, pr?ximos aos da literatura para amostras sinterizadas a 1500 ?C. O desempenho eletroqu?mico como material de catodo foi avaliado em uma configura??o de c?lula sim?trica (catodo/substrato/catodo) usando a t?cnica de espectroscopia de imped?ncia. Catodos de niquelato de lant?nio obtidos por serigrafia e sinterizados a 1300 ?C por 4 h apresentaram uma resist?ncia espec?fica de ?rea (REA) de 2,85 ohm.cm2 a 800 ?C em atmosfera de oxig?nio. O niquelato de lant?nio foi misturado com o material do eletr?lito e sinterizado na mesma temperatura usada para sinteriza??o do filme de catodo a fim de avaliar poss?veis rea??es qu?micas entre estes materiais. Os materiais mostraram bons resultados eletroqu?micos se comparados com a literatura e estabilidade qu?mica at? a temperatura de 1300 ?C. / Solid oxide fuel cells are the most efficient devices ever invented for the conversion of chemical fuels directly into electrical energy. These devices still have the disadvantage of operating at relatively high temperature. La2-xNiO4+d cathode, series materials with structure K2NiF4, have been considered as very promising materials due to their high mixed ionic electronic to intermediate temperature. The interest in these oxides as functional material for cathode increased because of its oxygen permeability and its stability. This material has coefficient of thermal expansion compatible with electrolytes from the La10-x(SiO4)6O2+-d family and apatite structure. These electrolytes have higher conductivities than zirconia-based electrolytes if used in the same temperature range as the above-mentioned cathode. This work reports the synthesis of apatite-type lanthanum silicate powders with nominal composition La10Si6O27 and Lanthanum nickelate (La2NiO4) for using as electrolyte and cathode materials, respectively, in solid oxide fuel cells. The lanthanum silicate was obtained from a co-precipitation chemical route, while the cathode was obtained by the citrate method. The herein proposed synthetic procedure is advantageous in reducing energy consumption and processing time, key elements to decrease the total manufacturing cost. At the end of the syntheses, the precursors powders were characterized by thermogravimetric analysis. The lanthanum silicate powders as prepared were calcined between 500 and 900 ?C and characterized by X-ray diffraction (XRD), Rietveld refinement and scanning electron microscopy (SEM). Already the lanthanum nickelate was calcined in a single temperature 1200 ?C for 4h and characterized by SEM. The structural characterization of the electrolyte indicated the formation of biphasic material after calcination at 900 ?C. The effect of sintering temperature, ranging from 1400 to 1450 ?C, on the electrical properties was investigated by impedance spectroscopy. Electrical measurements were recorded in the 400 ? 800 ?C temperature range in air. The lanthanum silicate electrolyte sintered at 1450 ?C exhibited total electrical conductivity 2.12 x 10-3 S.cm-1 in 700 ?C comparable with samples from literature prepared and sintered at 1500 ?C. The electrochemical performance as cathode material was evaluated in a symmetrical cell configuration (cathode/substrate/cathode) using the electrochemical impedance spectroscopy. Lanthanum nickelate cathodes obtained by screen printing and sintered at 1300 ? C for 4 h had an area specific resistance (ASR) of 2.85 ohm.cm2 at 800 ? C under oxygen atmosphere. Lanthanum nickelate was mixed with the electrolyte material and sintered at the same temperature used to sinter the cathode film, in order to evaluate possible chemical reactions between them. The materials showed good electrochemical results compared to the literature and chemical stability up to 1300 ? C.

Made available in DSpace on 2014-12-17T14:06:59Z (GMT). No. of bitstreams: 1 LucianoLMS.pdf: 2498297 bytes, checksum: 4e0c9395aebdb6d0be7a37737a51ca92 (MD5) Previous issue date: 2008-04-29 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Oxide type spinel AB2O4 presents structure adjusted for application in the automobile industry. The spinel of cobalt has many practical applications had its excellent physical and chemical properties such as catalyst in hydrocarbon oxidation reaction. The CeO2 has been used in many of these processes because it assigns to a material with excellent thermal resistance and mechanics, high capacity of oxygen stockage (OSC) among others properties. This work deals with the synthesis, characterization and catalytic application of spinel of cobalt and CeO2 with fluorita structure, obtained for method of Pechini and method of Gel-Combustion. The process of Pechini, the puff was obtained at 300 ?C for 2 h in air. In the process of Gel-Combustion the approximately at 350 ?C material was prepared and burnt for Pyrolysis, both had been calcined at 500 ?C, 700 ?C, 900 ?C and 1050 ?C for 2 h in air. The materials of the calcinations had been characterized by TG/DTA, electronic microscopy of sweepings (MEV), spectroscopy of absorption in the infra-red ray (FTIR) and diffraction of X-rays (DRX). The obtained material reaches the phase oxide at 450 oC for Pechini method and 500 ?C for combustion method. The samples were submitted catalytic reaction of n-hexane on superficies of materials. The reactor function in molar ration of 0, 85 mol.h-1.g-1 and temperature of system was 450 ?C. The sample obtained for Pechini and support in alumine of superficial area of 178,63 m2.g-1 calcined at 700 ?C, give results of catalytic conversions of 39 % and the sample obtained for method of gel-combustion and support in alumina of 150 mesh calcined at 500 ?C result 13 % of conversion. Both method were selective specie C1 / O espin?lio de cobalto tem muitas aplica??es pr?ticas devido as suas excelentes propriedades f?sicas e qu?micas tal como catalisador nas rea??es de oxida??o de hidrocarboneto. O CeO2 tem sido utilizado em muitos processos porque designa um material com excelente resist?ncia t?rmica e mec?nica, alta capacidade de estocagem de oxig?nio (OSC) entre outras propriedades. Este trabalho trata da s?ntese e caracteriza??o e aplica??o catal?tica dos ?xidos de cobalto com estrutura espin?lio e CeO2 com estrutura fluorita, obtidos pelo m?todo de Pechini e pelo m?todo de gel-combust?o. No processo Pechini o puff foi obtido a 300 ?C por 2 h em atmosfera ambiente. No processo de gel-combust?o o material foi preparado e queimado a aproximadamente 350 ?C por igni??o espont?nea e, posteriormente, ambos os p?s foram calcinados a 500 ?C, 700 ?C, 900 ?C e 1050 ?C por 2 h em atmosfera ambiente. Os p?s-resultantes das calcina??es foram caracterizados por TG/DTA, microscopia eletr?nica de varredura (MEV), espectroscopia de absor??o no infravermelho (FTIR) e difra??o de raios X (DRX). O material obtido deve atingir a fase ?xida a 450 ?C, para Pechini e 500 ?C para gel-combust?o. As amostras foram submetidas a rea??es catal?ticas de n-hexano sobre os catalisadores de Ce/Co. O reator operou a uma raz?o F/W fluxo molar de reagente por grama de catalisador de 0,85 mol.h-1.g-1 e temperatura no leito de 450 ?C. Para amostras obtidas por Pechini calcinadas a 700 ?C e suportada em alumina com ?rea superficial de 178,63 m2.g-1 obteve-se 39 % de convers?o catal?tica. Para as amostras obtidas pelo m?todo de gel-combust?o calcinadas a 500 ?C e suportada em alumina da Porogel com 150 mesh obteve cerca de 13 % de convers?o catal?tica. Ambos os m?todos foram seletivos a esp?cie C1.

Made available in DSpace on 2014-12-17T14:07:01Z (GMT). No. of bitstreams: 1 SamaraMV_DISSERT.pdf: 3021267 bytes, checksum: 443b2ba79e877562b95c18cd66a9716c (MD5) Previous issue date: 2012-03-22 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Cells the solid oxide fuel are systems capable to directly convert energy of a chemical reaction into electric energy in clean, quiet way and if its components in the solid state differentiate of excessively the techniques for having all. Its more common geometric configurations are: the tubular one and to glide. Geometry to glide beyond the usual components (anode, cathode and electrolyte) needs interconnect and sealant. E the search for materials adjusted for these components is currently the biggest challenge found for the production of the cells. The sealants need to present chemical stability in high temperatures, to provoke electric isolation, to have coefficient of compatible thermal expansion with the excessively component ones. For presenting these characteristics the glass-ceramics materials are recommended for the application. In this work the study of the partial substitution of the ZrO2 for the Al2O3 in system LZS became it aiming at the formation of system LZAS, this with the addition of natural spodumene with 10, 20 and 30% in mass. The compositions had been casting to a temperature of 1500?C and later quickly cooled with the objective to continue amorphous. Each composition was worn out for attainment of a dust with average diameter of approximately 3?m and characterized by the techniques of DRX, FRX, MEV, dilatometric analysis and particle size analysis. Later the samples had been conformed and treated thermally with temperatures in the interval between 700-1000 ?C, with platform of 10 minutes and 1 hour. The analyses for the treated samples had been: dilatometric analysis, DRX, FRX, electrical conductivity and tack. The results point with respect to the viability of the use of system LZAS for use as sealant a time that had presented good results as isolating electric, they had adhered to a material with similar ? of the components of a SOFC and had presented steady crystalline phases / Pilhas a combust?vel de ?xido s?lido (PaCOS) s?o sistemas capazes de converter energia de uma rea??o qu?mica diretamente em energia el?trica de maneira limpa, silenciosa e se diferenciam das demais t?cnicas por ter todos os seus componentes no estado s?lido. Suas configura??es geom?tricas mais comuns s?o: a tubular e a planar. A geometria planar al?m dos componentes usuais (anodo, catodo e eletr?lito) necessita de interconectores e selantes. E a busca por materiais adequados para esses componentes ? atualmente o maior desafio encontrado para a produ??o das pilhas. Os selantes precisam apresentar estabilidade qu?mica em altas temperaturas, provocar isolamento el?trico e ter coeficiente de dilata??o t?rmica compat?vel com os demais componentes. Por apresentarem essas caracter?sticas os materiais vitrocer?micos s?o os mais recomendados para a aplica??o. Neste trabalho fez-se o estudo da substitui??o parcial da Zr02 pela Al2O3 no sistema LZS visando a forma??o do sistema LZAS, isso com a adi??o 10, 20 e 30% em massa de espodum?nio natural. As composi??es foram fundidas a uma temperatura de 1500?C e depois resfriadas rapidamente com o objetivo de continuarem amorfas. Cada composi??o foi mo?da para obten??o de um p? com di?metro m?dio de aproximadamente 3?m e caracterizada pelas t?cnicas de DRX, FRX, MEV, dilatometria e granulometria. Posteriormente as amostras foram preparadas por compacta??o e tratadas termicamente com temperaturas no intervalo entre 700-1000 ?C, com patamar de 10min e 1h. As an?lises para as amostras tratadas foram: dilatometria, DRX, FRX, condutividade el?trica e ader?ncia. Os resultados apontam para a viabilidade do sistema LZAS para uso como selante uma vez que apresentaram bons resultados como isolante el?trico, aderiram a um material com coeficiente de dilata??o t?rmica (?) semelhante a dos componentes de uma PaCOS e apresentaram fases cristalinas est?veis / 2020-01-01

Made available in DSpace on 2014-12-17T14:07:02Z (GMT). No. of bitstreams: 1 MichelineRA_DISSERT.pdf: 3734590 bytes, checksum: b9c518dbcf57b2b63cf9d386db2a5df1 (MD5) Previous issue date: 2012-02-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Continuous Synthesis by Solution Combustion was employed in this work aiming to obtain tin dioxide nanostructured. Basically, a precursor solution is prepared and then be atomized and sprayed into the flame, where its combustion occurs, leading to the formation of particles. This is a recent technique that shows an enormous potential in oxides deposition, mainly by the low cost of equipment and precursors employed. The tin dioxide (SnO2) nanostructured has been widely used in various applications, especially as gas sensors and varistors. In the case of sensors based on semiconducting ceramics, where surface reactions are responsible for the detection of gases, the importance of surface area and particle size is even greater. The preference for a nanostructured material is based on its significant increase in surface area compared to conventional microcrystalline powders and small particle size, which may benefit certain properties such as high electrical conductivity, high thermal stability, mechanical and chemical. In this work, were employed as precursor solution tin chloride dehydrate diluted in anhydrous ethyl alcohol. Were utilized molar ratio chloride/solvent of 0,75 with the purpose of investigate its influence in the microstructure of produced powder. The solution precursor flux was 3 mL/min. Analysis with X-ray diffraction appointed that a solution precursor with molar ratio chloride/solvent of 0,75 leads to crystalline powder with single phase and all peaks are attributed to phase SnO2. Parameters as distance from the flame with atomizer distance from the capture system with the pilot, molar ratio and solution flux doesn t affect the presence of tin dioxide in the produced powder. In the characterization of the obtained powder techniques were used as thermogravimetric (TGA) and thermodiferential analysis (DTA), particle size by laser diffraction (GDL), crystallographic analysis by X-ray diffraction (XRD), morphology by scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area (BET) and electrical conductivity analysis. The techniques used revealed that the SnO2 exhibits behavior of a semiconductor material, and a potentially promising material for application as varistor and sensor systems for gas / A S?ntese Cont?nua por Combust?o em Solu??o (SCCS) foi empregada na obten??o de p?s de di?xido de estanho nanoestruturados. Basicamente, uma solu??o precursora ? preparada, sendo posteriormente atomizada e aspergida na chama, onde ocorre a combust?o, levando ? forma??o das part?culas. A t?cnica apresenta um grande potencial na produ??o de nanopart?culas, principalmente pelo baixo custo de insumos e equipamentos. O di?xido de estanho (SnO2) nanoestruturado tem sido amplamente utilizado em diversas aplica??es, principalmente como sensores de g?s e varistores. No caso dos sensores ? base de cer?micas semicondutoras, em que as rea??es de superf?cies s?o respons?veis pela detec??o dos gases, a import?ncia da ?rea superficial e do tamanho de part?culas ? ainda maior. A prefer?ncia por um material nanoestruturado deve-se ao fato de que essas entidades apresentam alguns pontos fundamentais tais como, o aumento significativo da ?rea superficial comparados aos p?s microcristalinos convencionais e o reduzido tamanho de part?cula, que pode beneficiar certas propriedades como alta condutividade el?trica, alta estabilidade t?rmica, mec?nica e qu?mica. Neste trabalho, foram empregados como solu??o precursora cloreto de estanho dihidratado dilu?dos em ?lcool et?lico anidro. Foi utilizada a raz?o molar cloreto/solvente de 0,75 no intuito de investigar sua influ?ncia na microestrutura do material obtido. O fluxo da solu??o precursora foi de 3 mL/min. A an?lise por difra??o de raios X da solu??o precursora com raz?o molar cloreto/solvente de 0,75 indicou a obten??o de um p? cristalino e monof?sico e todos os picos s?o atribu?dos a fase SnO2. Par?metros de s?ntese como dist?ncia da chama com o atomizador, dist?ncia do sistema de capta??o com a chama piloto, raz?o molar e fluxo da solu??o precursora n?o afetaram a fase di?xido de estanho no material obtido. Na caracteriza??o do p? obtido, foram utilizadas t?cnicas como an?lises termogravim?tricas (ATG) e termodiferenciais (ATD), granulometria por difra??o de laser (GDL), an?lise cristalogr?fica por difra??o de raios X (DRX), morfologia por microscopia eletr?nica de varredura (MEV), microscopia eletr?nica de transmiss?o (MET), medida de ?rea superficial espec?fica (BET) e ensaio de condutividade el?trica. O conjunto de t?cnicas revelaram que o SnO2 apresenta comportamento de um material semicondutor, sendo um material potencialmente promissor ? aplica??o como varistor e em sistemas de sensores ? gases

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

Made available in DSpace on 2014-12-17T14:07:09Z (GMT). No. of bitstreams: 1 FlaviaMA_TESE_partes_autorizadas.pdf: 1059426 bytes, checksum: e2aa7ae9084b3b21cbc8a9c274f271a1 (MD5) 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

Made available in DSpace on 2014-12-17T14:08:41Z (GMT). No. of bitstreams: 1 AnthonyARD_DISSERT.pdf: 2982432 bytes, checksum: 71a6d988a19819a67932642761ac3dda (MD5) Previous issue date: 2010-09-03 / In the last decades, the oil, gas and petrochemical industries have registered a series of huge accidents. Influenced by this context, companies have felt the necessity of engaging themselves in processes to protect the external environment, which can be understood as an ecological concern. In the particular case of the nuclear industry, sustainable education and training, which depend too much on the quality and applicability of the knowledge base, have been considered key points on the safely application of this energy source. As a consequence, this research was motivated by the use of the ontology concept as a tool to improve the knowledge management in a refinery, through the representation of a fuel gas sweetening plant, mixing many pieces of information associated with its normal operation mode. In terms of methodology, this research can be classified as an applied and descriptive research, where many pieces of information were analysed, classified and interpreted to create the ontology of a real plant. The DEA plant modeling was performed according to its process flow diagram, piping and instrumentation diagrams, descriptive documents of its normal operation mode, and the list of all the alarms associated to the instruments, which were complemented by a non-structured interview with a specialist in that plant operation. The ontology was verified by comparing its descriptive diagrams with the original plant documents and discussing with other members of the researchers group. All the concepts applied in this research can be expanded to represent other plants in the same refinery or even in other kind of industry. An ontology can be considered a knowledge base that, because of its formal representation nature, can be applied as one of the elements to develop tools to navigate through the plant, simulate its behavior, diagnose faults, among other possibilities / Nas ?ltimas d?cadas, o segmento de ?leo & g?s e petroqu?mica tem registrado uma s?rie de grandes acidentes. Influenciadas por esse contexto, as empresas tem sentido a necessidade de se engajar em processos de prote??o do ambiente externo, que se traduz na preocupa??o ecol?gica. No caso particular da ind?stria nuclear mundial, a educa??o sustent?vel e o treinamento, que dependem muito da qualidade e utilidade da base de conhecimento, t?m sido considerados pontos chave para utiliza??o desse tipo de energia com seguran?a. Dessa forma, a motiva??o dessa pesquisa foi aplicar o conceito de ontologia como ferramenta para melhorar a gest?o do conhecimento em uma refinaria, atrav?s da representa??o de uma planta de ado?amento de g?s combust?vel, condensando os v?rios tipos informa??es associados com o seu modo de opera??o normal. Em termos de metodologia, este estudo pode ser classificado como uma pesquisa aplicada e descritiva, em que foram analisadas, classificadas e interpretadas informa??es que possibilitaram criar a ontologia descritiva de uma planta real. A modelagem da planta DEA foi realizada de acordo com os fluxogramas de processo, fluxogramas de tubula??o e instrumenta??o, documentos descritivos de seu modo de opera??o e a rela??o de alarmes associados, que foram complementadas com uma entrevista n?o estruturada de um especialista em seu modo de opera??o. A valida??o aconteceu atrav?s da compara??o de grafos montados a partir da ontologia com a documenta??o original e debatidos com o grupo de trabalho. Os conceitos utilizados nesta pesquisa podem ser expandidos para representar outras plantas da pr?pria refinaria ou mesmo de outras ind?strias. A ontologia pode ser considerada uma base de conhecimento, que devido ao seu car?ter formal, pode ser aplicada como um dos elementos no desenvolvimento de ferramentas de navega??o da planta, simula??o de comportamento, diagn?stico de falhas, dentre outras possibilidades

Made available in DSpace on 2014-12-17T14:08:49Z (GMT). No. of bitstreams: 1 EdsonAA_DISSERT.pdf: 3674397 bytes, checksum: 68989b5d2aabcb74990cc326c009fbc6 (MD5) Previous issue date: 2012-02-17 / The method "toe-to-heel air injection" (THAITM) is a process of enhanced oil recovery, which is the integration of in-situ combustion with technological advances in drilling horizontal wells. This method uses horizontal wells as producers of oil, keeping vertical injection wells to inject air. This process has not yet been applied in Brazil, making it necessary, evaluation of these new technologies applied to local realities, therefore, this study aimed to perform a parametric study of the combustion process with in-situ oil production in horizontal wells, using a semi synthetic reservoir, with characteristics of the Brazilian Northeast basin. The simulations were performed in a commercial software "STARS" (Steam, Thermal, and Advanced Processes Reservoir Simulator), from CMG (Computer Modelling Group). The following operating parameters were analyzed: air rate, configuration of producer wells and oxygen concentration. A sensitivity study on cumulative oil (Np) was performed with the technique of experimental design, with a mixed model of two and three levels (32x22), a total of 36 runs. Also, it was done a technical economic estimative for each model of fluid. The results showed that injection rate was the most influence parameter on oil recovery, for both studied models, well arrangement depends on fluid model, and oxygen concentration favors recovery oil. The process can be profitable depends on air rate / O m?todo toe-to-heel air injection (THAITM) ? um processo de recupera??o de petr?leo avan?ado, que consiste na integra??o da combust?o in-situ com os avan?os tecnol?gicos na perfura??o de po?os horizontais. Este m?todo utiliza po?os horizontais como produtores de ?leo, mantendo po?os injetores verticais para a inje??o de ar. Este processo ainda n?o foi aplicado no Brasil, tornando necess?rio, avalia??o destas novas tecnologias aplicadas ?s realidades locais, por isso, este trabalho teve como objetivo principal realizar um estudo param?trico do processo de combust?o in-situ com produ??o de ?leo em po?os horizontais, usando um reservat?rio semi sint?tico, com caracter?sticas das encontradas no Nordeste Brasileiro. As simula??es foram realizadas em um programa comercial de processos t?rmicos, denominado STARS (Steam, Thermal, and Advanced Processes Reservoir Simulator), da empresa CMG (Computer Modelling Group). Foram realizadas an?lises dos par?metros operacionais: vaz?es de inje??o, configura??o dos po?os e concentra??o de oxig?nio. O estudo de sensibilidade dos fatores foi realizado com a t?cnica de an?lise de planejamento experimental, com uma combina??o de dois e tr?s n?veis (32x22), totalizando 36 simula??es, 18 para cada modelo, em fun??o da produ??o acumulada de ?leo (Np). Tamb?m foi realizada uma estimativa econ?mica de an?lise de custo para cada modelo de fluido. Os resultados mostraram que a configura??o de po?os e a vaz?o de inje??o foram o par?metro que apresentou maior influ?ncia no ?leo recuperado para os dois modelos de fluidos analisados, respectivamente, que a configura??o de po?os ? influenciada pelo modelo de fluido, e que um aumento da concentra??o de oxig?nio favorece a recupera??o de ?leo, no processo estudado. Tamb?m foi encontrado que o processo pode ser rent?vel dependendo da quantidade de ar injetado no processo

Made available in DSpace on 2014-12-17T14:08:52Z (GMT). No. of bitstreams: 1 RaoniBA_DISSERT.pdf: 2283831 bytes, checksum: 9e3bfc1213fc5b5ac439fb175ddc5631 (MD5) Previous issue date: 2012-12-14 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The retail fuel stations are partially or potentially polluters and generators of environmental accidents, potentially causing contamination of underground and surface water bodies, soil and air. Leaks in fuel retail stations? underground storage systems are often detected in Brazil and around the world. Monoaromatic hydrocarbons, BTEX (benzene, toluene, ethylbenzene and xylenes) and polycyclic aromatic hydrocarbons (PAHs) are an indication of the presence of contamination due to its high toxicity. This paper presents a case study of contamination in a Fuel Retail Station by petroleum derivative products in the city of Natal. For identification and quantification of the hydrocarbons, EPA analytical methods were used. The values of benzene quantified by EPA method 8021b CG-PID/FID, ranged from 1.164 to 4.503 mg.Kg-1 in soil samples, and from 12.10 to 27,639 μg.L-1 in underground water samples. Among the PAHs, naphthalene and anthracene showed the most significant results in soil samples, 0.420 to 15.46 mg.Kg-1 and 0.110 to 0,970 mg.Kg-1, respectively. In underground water samples, the results for Naphthalene varied between 0.759 and 614.7 μg.L-1. PAHs were quantified by EPA Method 8270 for GCMS. All of the results for the chemical analysis were compared with the values for the CONAMA 420/2009 resolution. The results for benzene (27,639 μg.L-1) showed levels highly above the recommended by the CONAMA 420 resolution, wherein the maximum permissible for underground water is 5 μg.L-1. This is a worrying factor, since underground water makes up 70% of the city of Natal?s water supply / The retail fuel stations are partially or potentially polluters and generators of environmental accidents, potentially causing contamination of underground and surface water bodies, soil and air. Leaks in fuel retail stations? underground storage systems are often detected in Brazil and around the world. Monoaromatic hydrocarbons, BTEX (benzene, toluene, ethylbenzene and xylenes) and polycyclic aromatic hydrocarbons (PAHs) are an indication of the presence of contamination due to its high toxicity. This paper presents a case study of contamination in a Fuel Retail Station by petroleum derivative products in the city of Natal. For identification and quantification of the hydrocarbons, EPA analytical methods were used. The values of benzene quantified by EPA method 8021b CG-PID/FID, ranged from 1.164 to 4.503 mg.Kg-1 in soil samples, and from 12.10 to 27,639 μg.L-1 in underground water samples. Among the PAHs, naphthalene and anthracene showed the most significant results in soil samples, 0.420 to 15.46 mg.Kg-1 and 0.110 to 0,970 mg.Kg-1, respectively. In underground water samples, the results for Naphthalene varied between 0.759 and 614.7 μg.L-1. PAHs were quantified by EPA Method 8270 for GCMS. All of the results for the chemical analysis were compared with the values for the CONAMA 420/2009 resolution. The results for benzene (27,639 μg.L-1) showed levels highly above the recommended by the CONAMA 420 resolution, wherein the maximum permissible for underground water is 5 μg.L-1. This is a worrying factor, since underground water makes up 70% of the city of Natal?s water supply