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1
Morelli, Marcio Raymundo. "Liquid phase sintering of perovskite." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297279.
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SETZ, LUIZ F. G. "Obtencao de Lasub(1-x)Srsub(x)Crsub(1-y)Cosub(y)Osub(3) por reacao de combustao." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11237.
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Dissertacao (Mestrado)
IPEN/D
Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP
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SETZ, LUIZ F. G. "Processamento coloidal de cromito de lantanio." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11522.
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IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Huang, Ming-Hsien. "Preparation of some Mg-doped lanthanum chromites for solid oxide fuel cell applications." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46828.
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Jorgensen, Mette Juhl. "Lanthanum manganate based cathodes for solid oxide fuel cells." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343243.
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Esquirol, Audrey. "Characterisation of doped lanthanum ferrite cathodes for intermediate temperature solid oxide fuel cells." Thesis, Imperial College London, 2003. http://hdl.handle.net/10044/1/12007.
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Zheng, Feng. "Phase stability and processing of Sr and Mg doped lanthanum gallate /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/10604.
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Kimpton, Justin Andrew, and jkimpton@physics unimelb edu au. "Conductivity and microstructural characterisation of doped Zirconia-Ceria and Lanthanum Gallate electrolytes for the intermediate-temperature, solid oxide fuel cell." Swinburne University of Technology, 2002. http://adt.lib.swin.edu.au./public/adt-VSWT20060727.084311.
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Lowering the operating temperature of the high-temperature, solid oxide fuel cell (SOFC) improves both the thermodynamic efficiency and the lifetime of this energy efficient technology. Unfortunately the rate of oxygen-ion transport through the solid electrolyte is temperature dependent, and materials previously employed as electrolytes in the high-temperature SOFC perform poorly at intermediate temperatures. Therefore new oxygen-ion conductors with enhanced ionic conductivity at intermediate temperatures are required. The bulk of the existing literature on high-temperature SOFCs has focussed on zirconia-based binary systems as electrolytes, due to their high ionic conductivity and negligible electronic conductivity. Only select compositions within the zirconia-scandia system have demonstrated acceptable ionic conductivity levels at intermediate temperatures; however unstable phase assemblage and the high economic cost of scandia are clear disadvantages. Ceria-based binary systems have demonstrated improved oxygen-ion conductivity at intermediate temperature compared to many zirconia systems, however significant levels of n-type electronic conductivity are observed at low oxygen partial pressures. Consequently it was thought unlikely that significant increases in ionic conductivity would be found in existing zirconia- and ceria-based binary systems, therefore another approach was required in an attempt to improve the performance of these established fluorite systems. The fluorite systems Zr0.75Ce0.08M0.17O1.92 (M = Nd, Sm, Gd, Dy, Ho, Y, Er, Yb, Sc) were prepared and investigated as possible, intermediate-temperature SOFC electrolytes in an attempt to combine the higher conductivity found in the ceria systems with the low electronic conductivity observed in the zirconia systems. Also it was anticipated that systems containing dopants not previously observed to confer high ionic conductivity in either zirconia- and ceria-based binary systems, might exhibit enhanced ionic conductivity with expansion of the zirconia lattice resulting from the addition of ceria. All the as-fired Zr0.75Ce0.08M0.17O1.92 compositions possessed the face-centred cubic structure and lattice parameter measurements revealed the anticipated unit cell enlargement as the size of the dopant cation increased. No unusual microstructural parameters were identified that could be expected to interfere with the ionic transport properties in the as-fired compositions. The electrical conductivity was found to be influenced by the dopant-ion radius, the presence of ceria, low oxygen partial pressures and, in some compositions, the formation of poorly conducting, ordered-pyrochlore microdomains dispersed amongst the cubic defect-fluorite matrix. In a second approach to the formulation of new oxygen-ion conductors suitable for the intermediate-temperature SOFC, compounds possessing structures other than the fluorite structure were considered. An examination of the literature for oxides having the pyrochlore, scheelite and perovskite structures showed that the Sr+2- and Mg+2-doped LaGaO3 perovskites (LSGM) possessed ionic conductivity equal to the highest conducting, zirconia and ceria binary compounds. Therefore the perovskite systems La0.9Sr0.1Ga(0.8-x)InxMg0.2O2.85 (X = 0, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8) (I-LSGM) were prepared and examined, the objective being to favourably influence structural parameters believed responsible for optimal ionic conductivity, namely the unit cell symmetry and volume. It was found that In+3 systematically substituted for Ga+3 on to the B-site of LSGM at least up to the X = 0.4 composition. While In+3 was found to replace the Ga+3 as expected, Mg+2, which occupies the same crystallographic site, was also replaced by In+3. Up to the X = 0.2 composition, at least two trace level secondary phases were observed to form along with the bulk I-LSGM phase. For I-LSGM compositions with X > 0.2, significantly larger concentrations of the secondary phases were identified. Evidence of a strontium-rich, high-temperature liquid phase was observed also near the grain boundaries on as-sintered and thermally etched surfaces in LSGM and I-LSGM compositions. It is believed that the observed, high sintered density in the complex, doped-LaGaO3 systems is due to the formation of this high-temperature liquid phase. Increasing levels of diffuse scatter and superstructure formation were observed in electron diffraction patterns in the I-LSGM bulk phase (up to X = 0.2), indicating a possible decrease in vacancy concentration and reduced, localised unit cell symmetry. The electrical conductivity in the I-LSGM compositions was believed to be influenced by the distortion of the oxygen-ion conduction path, a reduction in vacancy concentration, formation of stronger dopant-vacancy associates at low temperature and the presence of ordered structures. In addition, phase instability, in the form of subtle ordering in specific crystalline planes, was observed to influence the electrical conductivity as a function of time at intermediate temperatures.
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Price, Robert. "Metal/metal oxide co-impregnated lanthanum strontium calcium titanate anodes for solid oxide fuel cells." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/16018.
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Solid Oxide Fuel Cells (SOFC) are electrochemical energy conversion devices which allow fuel gases, e.g. hydrogen or natural gas, to be converted to electricity and heat at much high efficiencies than combustion-based energy conversion technologies. SOFC are particularly suited to employment in stationary energy conversion applications, e.g. micro-combined heat and power (μ-CHP) and base load, which are certain to play a large role in worldwide decentralisation of power distribution and supply over the coming decades. Use of high-temperature SOFC technology within these systems is also a vital requirement in order to utilise fuel gases which are readily available in different areas of the world. Unfortunately, the limiting factor to the long-term commercialisation of SOFC systems is the redox instability, coking intolerance and sulphur poisoning of the state-of-the-art Ni-based cermet composite anode material. This research explores the ‘powder to power' development of alternative SOFC anode catalyst systems by impregnation of an A-site deficient La0.20Sr0.25Ca0.45TiO3 (LSCT[sub](A-)) anode ‘backbone' microstructure with coatings of ceria-based oxide ion conductors and metallic electrocatalyst particles, in order to create a SOFC anode which exhibits high redox stability, tolerance to sulphur poisoning and low voltage degradation rates under operating conditions. A 75 weight percent (wt. %) solids loading LSCT[sub](A-) ink, exhibiting ideal properties for screen printing of thick-film SOFC anode layers, was screen printed with 325 and 230 mesh counts (per inch) screens onto electrolyte supports. Sintering of anode layers between 1250 °C and 1350 °C for 1 to 2 hours indicated that microstructures printed with the 230 mesh screen provided a higher porosity and improved grain connectivity than those printed with the 325 mesh screen. Sintering anode layers at 1350 °C for 2 hours provided an anode microstructure with an advantageous combination of lateral grain connectivity and porosity, giving rise to an ‘effective' electrical conductivity of 17.5 S cm−1 at 850 °C. Impregnation of this optimised LSCT[sub](A-) anode scaffold with 13-16 wt. % (of the anode mass) Ce0.80Gd0.20O1.90 (CGO) and either Ni (5 wt. %), Pd, Pt, Rh or Ru (2-3 wt. %) and integration into SOFC resulted in achievement of Area Specific Resistances (ASR) of as low as 0.39 Ω cm−2, using thick (160 μm) 6ScSZ electrolytes. Durability testing of SOFC with Ni/CGO, Ni/CeO2, Pt/CGO and Rh/CGO impregnated LSCT[sub](A-) anodes was subsequently carried out in industrial button cell test rigs at HEXIS AG, Winterthur, Switzerland. Both Ni/CGO and Pt/CGO cells showed unacceptable levels of degradation (14.9% and 13.4%, respectively) during a ~960 hour period of operation, including redox/thermo/thermoredox cycling treatments. Significantly, by exchanging the CGO component for the CeO2 component in the SOFC containing Ni, the degradation over the same time period was almost halved. Most importantly, galvanostatic operation of the SOFC with a Rh/CGO impregnated anode for >3000 hours (without cycling treatments) resulted in an average voltage degradation rate of < 1.9% kh−1 which, to the author's knowledge, has not previously been reported for an alternative, SrTiO3-based anode material. Finally, transfer of the Rh/CGO impregnated LSCT[sub](A-) anode to industrial short stack (5 cells) scale at HEXIS AG revealed that operation in relevant conditions, with low gas flow rates, resulted in accelerated degradation of the Rh/CGO anode. During a 1451 hour period of galvanostatic operation, with redox cycles and overload treatments, a voltage degradation of 19.2% was observed. Redox cycling was noted to briefly recover performance of the stack before rapidly degrading back to the pre-redox cycling performance, though redox cycling does not affect this anode detrimentally. Instead, a more severe, underlying degradation mechanism, most likely caused by instability and agglomeration of Rh nanoparticles under operating conditions, is responsible for this observed degradation. Furthermore, exposure of the SOFC to fuel utilisations of >100% (overloading) had little effect on the Rh/CGO co-impregnated LSCT[sub](A-) anodes, giving a direct advantage over the standard HEXIS SOFC. Finally, elevated ohmic resistances caused by imperfect contacting with the Ni-based current collector materials highlighted that a new method of current collection must be developed for use with these anode materials.
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CHIBA, RUBENS. "Obtencao e caracterizacao de manganito de lantanio dopado com estroncio para aplicacao em celulas a combustivel de oxido solido." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11234.
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Dissertacao (Mestrado)
IPEN/D
Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP
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Cooper, Matthew E. "Energy production from coal syngas containing H₂S via solid oxide fuel cells utilizing lanthanum strontium vanadate anodes." Ohio : Ohio University, 2008. http://www.ohiolink.edu/etd/view.cgi?ohiou1219867679.
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Cooper, Matthew E. "Energy Production from Coal Syngas Containing H2S via Solid Oxide Fuel Cells Utilizing Lanthanum Strontium Vanadate Anodes." Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1219867679.
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Yang, Jun. "Studies on Polarization Behavior and Microstructure of Strontium-doped Lanthanum Manganite Cathodes for Solid Oxide Fuel Cells." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/151984.
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Amani, Hamedani Hoda. "Investigation of deposition parameters in ultrasonic spray pyrolysis for fabrication of solid oxide fuel cell cathode." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26670.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Qu, Jianmin; Committee Co-Chair: Garmestani, Hamid; Committee Member: Haynes, Comas; Committee Member: Klaus-Hermann Dahmen; Committee Member: Liu, Meilin. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Ma, Yangzhou. "Modeling and development of new materials for fuel cells solid electrolyte." Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0286/document.
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Les piles à combustibles à électrolyte solide de type SOFC permettent de transformer directement l’énergie de la réaction chimique de formation de l’eau à partir de l’hydrogène et de l’oxygène, en énergie électrique. De nos jours, les apatites de type silicates de terres rares présentent beaucoup d’intérêt comme électrolyte solide en raison de leurs propriétés de transport élevées avec une forte conductivité ionique et une faible énergie d'activation. Ils peuvent fonctionner de manière stable à une température intermédiaire sur une large plage de pression partielle d'oxygène en maintenant d'excellentes performances. Ils sont ainsi considérés comme de bons candidats pour les électrolytes de piles de type IT-SOFC. Parmi cette série de conducteurs, le type La-Si-O possède une conductivité plus élevée et leur performance serait modifiée par différents éléments dopants.L'objectif de cette thèse est d'étudier les effets des éléments de substitution / dopage ainsi que les méthodes de synthèse sur les propriétés structurales ainsi que sur la conductivité des apatites de type silicates de lanthane. Dans cette étude, nous utilisons une double approche: une approche de simulation et une approche expérimentale pour optimiser la pureté et les performances des matériaux d'électrolyte.Dans l'approche de simulation, le calcul basé sur la DFT (Théorie de la fonctionnelle de la densité) a été réalisée en vue d’étudier l'effet des positions de dopage: dopant Sr à La position de La et dopant Ge à la position de Si. Les résultats obtenus par le calcul concernant la conductivité ionique confirment ceux obtenus par l’expérience.Avec l’approche expérimentale, nous présentons la synthèse et la caractérisation de La10Si6O27 (LSO) dopé par Sr et élaboré par des procédés sol-gel. Les résultats montrent que la conductivité ionique est activé thermiquement et que les valeurs se situent entre 4,5 × 10-2 et 1 x 10-6 S·cm-1 à 873 K et dépend des conditions d’élaboration et de la composition de la poudreThe Solid Oxide Fuel Cell (SOFC) defined by its ceramic and oxide electrolyte, is an electrochemical energy conversion device that produces electricity directly from the chemical reaction of fuel. Nowadays, apatite type rare earths silicates and germaniums attract many interests as the solid electrolyte due to the superior transport properties with high ionic conductivity and low activation energy. They can operate stably at intermediate temperature over a wide oxygen partial pressure range and maintain excellent performances, being considered as a candidate for IT-SOFC electrolytes. Among this series of conductors, the La-Si-O type has a higher conductivity and the performance would be modified by different doping elements.The objective of this thesis is to study the effects of element substitution/doping and synthesis methods on the structural and conductivity properties of apatite type lanthanum silicates. In this study, we use a double approach: a simulation approach and an experimental approach to optimize the electrolyte materials purity and performance.Using simulation approach, a first principle calculation based on DFT (Density Functional Theory) was carried out to investigate the effect on doping positions: Sr dopant at La position and Ge dopant at Si position. The calculation results give a connection to the ionic conductivity obtained by experiments.With experimental approach, we present the synthesis and characterization of Sr-doped La10Si6O27 (LSO) prepared through an optimized water-based sol-gel process. The results show that the ionic conductivity is thermally activated and values lies between 4.5×10-2 and 1×10-6 Scm-1 at 873 K as a function of the composition and powder preparation conditions
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Lu, Yunxiang. "Study of electrochemical performance of strontium doped lanthanum cobalt oxides using electrochemical impedance spectroscopy and microelectrode array cell design /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9818.
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Chen, Xiyong. "Thermo-mechanical/structural properties and oxygen permeation behavior of mixed ionic electronic conductors La(1-x)Sr(x)CoO(3-delta) /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9893.
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GOMES, THIAGO B. "Estudo da reação de redução do oxigênio utilizando eletrocatalisadores à base de platina e terras raras (La, Ce, Er) para aplicação em células a combustível tipo PEM." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10586.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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CORDEIRO, GUILHERME L. "Estudo de síntese de catalisadores de níquel suportados em alumina-lantânia para aplicação na produção de hidrogênio a partir da reforma a vapor do etanol." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23703.
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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ELIAS, DANIEL R. "Síntese e caracterização de pós de silicato de lantânio tipo apatita para eletrólito em SOFC." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10612.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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CHIBA, RUBENS. "Sintese, processamento e caracterizacao das meia-celulas de oxido solido catodo/eletrolito de manganito de lantanio dopado com estroncio/zirconia estabilizada com itria." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9503.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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RODRIGUES, RANIERI A. "Estudo da formação de fases secundárias no compósito LSM/YSZ." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11563.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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FLORIO, DANIEL Z. de. "Analise de eletrolitos de ZrO sub(2):Y sub(2) O sub(3) + B sub(2) O sub(3) e de eletrodos de La sub(0,8) Sr sub(0,2) Co sub (0,8) Fe sub (0,2) O sub (3-delta) por espectroscopia de impedancia." reponame:Repositório Institucional do IPEN, 2003. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11130.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Ivan, Stijepović. "Dobijanje lantan-galata za primenu u gorivnim ćelijama." Phd thesis, Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, 2012. https://www.cris.uns.ac.rs/record.jsf?recordId=85671&source=NDLTD&language=en.
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U ovom radu su sintetisani prahovi na bazi lantan-galata, citratnom sol-gelmetodom i hemijskom sintezom u parnoj fazi (CVS), a njihovim presovanjemi sinterovanjem su dobijeni keramički uzorci kontrolisane mikrostrukture. Ciljdisertacije je bio dobijanje guste keramike koja bi mogla da se primeni kaojonski provodni elektrolit u gorivnim ćelijama sa čvrstim elektrolitom (SOFC),a koje bi radile na srednjim temperaturama od 500–700 °C (IT-SOFC). Po prviput su sintetisani nanoprahovi lantan-galata u gasnoj fazi i utvrđeno je da ovakodobijeni polazni prahovi, zbog svojih superiornih karakteristika omogućavajusnižavanje temperature sinterovanja za 150 °C, što je veoma povoljno kako sastanovišta dizajniranja mikrostrukture, tako i zbog uštede energije u procesuproizvodnje gorivnih ćelija. Ipak, zbog nedovoljne kontrole hemijskog sastavai stehiometrije sintetisanih prahova, što je i najveći nedostatak CVS metodedobijanja perovskitnog LaGaO3, nije bilo moguće dobiti keramiku koja bi ispunjavala zahteve za primenu u SOFC. S druge strane, citratna sol-gel metodapruža veliku kontrolu pomenutih parametara zbog čega je bila moguća sintezačitavog niza čvrstih rastvora lantan-galata. Ovom metodom su tako sintetisaničist lantan-galat (LG) i dopirani prahovi kod kojih je deo lantana supstituisanstroncijumom, a deo galijuma magnezijumom: La0,85Sr0,15Ga0,85Mg0,15O3-La1-xSrxGa0,8Mg0,2O3-, gde je x = 0,10, 0,15 ili 0,20 (LSGM). Svi ovako sintetisaniprahovi su zahtevali naknadnu kalcinaciju na 900 °C, ali su potrebnegustine (>95% teorijske gustine) postignute sinterovanjem na temperaturiod 1450 °C već nakon 2 h, što je izuzetno kratko imajući u vidu literaturnepodatke. Takođe, sinterovani uzorci su po faznom sastavu bili čista LSGMkeramika, a impedansna merenja su pokazala da je najveću provodljivost imaouzorak La0,85Sr0,15Ga0,8Mg0,2O3-. Ovaj sastav je dalje korišćen u cilju proveremogućnosti za dodatno povećanje provodljivosti te su pripremljeni i uzorci kod kojih je izvršena parcijalna supstitucija magnezijuma sa niklom ili kobaltom:La0,85Sr0,15Ga0,8Mg0,2-yMyO3-, gde je M = Ni ili Co, a y = 0,03 ili 0,05 (LSGMN iLSGMC). Pokazano je da dodatak male količine prelaznih metala značajno utičena mehanizam provođenja, ali da je na višim temperaturama jonska provodljivosti dalje dominantna. Konstatovano je da se dodavanjem male količine Ni ili Co uLSGM mogu dobiti materijali koji bi služili kao elektroliti u IT-SOFC, pri čemu jepotencijal nikla kao dopanta nešto veći nego kobalta.Powders based on lanthanum-gallate have been synthesised in this work by using citrate sol-gel method in the liquid phase and by chemical vapour synthesis (CVS). As-synthesised powders were calcined, pressed and finally sintered in order to produce ceramic samples with controlled microstructure. The main goal of this dissertation has been obtaining of dense ceramics for application in ion conducting electrolyte for solid oxide fuel cells working at 500–700 °C (IT-SOFC). Lanthanum-gallate nanopowders have been synthesised in the gas phase for the first time and it has been determined that these starting powders posses superior properties which could lower down the sintering temperature for about 150 °C. This is very significant considering microstructure design, but also high energy consumption during the manufacturing process of fuel cells. However, it has not been possible to obtain ceramics with exact properties needed for SOFC application using CVS due to the lack of control of chemical composition and stoichiometry of the as-synthesised powders, which are the main drawbacks of this method. On the other hand, citrate sol-gel method offered a possibility to precisely control aforementioned parameters which enabled synthesis of a whole range of lanthanum-gallate sollid solutions. So, pure perovskite lanthanum-gallate (LG) has been synthesised by using this liquid phase method, but also doped powders where part of lanthanum and gallium was supstituted with strontium and magnesium, respectively: La0,85Sr0,15Ga0,85Mg0,15O3- and La1-xSrxGa0,8Mg0,2O3-, where x = 0.10, 0.15 or 0.20 (LSGM). Calcination at 900 °C was necessary step during the processing of these sol-gel powders but the sintering time at 1450 °C was only 2 h which is quite short in comparison with available literature data. Additionaly, the sintered samples were phase pure LSGM ceramics and impedance measurement showed that the highest conductivity had sample La0,85Sr0,15Ga0,8Mg0,2O3-. Accordingly, this composition has been used to check the possibility of further improvement of conductivity. A set of new samples has been prepared where one part of magnesium has been substituted with nickel or cobalt: La0,85Sr0,15Ga0,8Mg0,2-yMyO3-, where M = Ni or Co and y = 0.03 or 0.05 (LSGMN i LSGMC). It has been shown that addition of small amount of transition metals significantly influences conduction mechanism, but at higher temperatures the ionic conductivity is still dominant. It has been found that electrolyte materials for IT-SOFCs could be obtained by incorporation of small quantities of Ni or Co into LSGM and that nickel is more promissing for this purpose than cobalt.
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MONTEIRO, NATALIA K. "Síntese e caracterização de manganita-cromita de lantânio dopada com rutênio para anodos de células a combustível de óxidos sólidos." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10041.
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Made available in DSpace on 2014-10-09T12:34:06Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:00:10Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Chiba, Rubens. "Síntese, processamento e caracterização das meia-células de óxido sólido catodo/eletrólito de manganito de lantânio dopado com estrôncio/zircônia estabilizada com ítria." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-29082011-141252/.
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Os filmes cerâmicos de manganito de lantânio dopado com estrôncio (LSM) e de manganito de lantânio dopado com estrôncio/zircônia estabilizada com ítria (LSM/YSZ) são utilizados como catodos das células a combustível de óxido sólido de temperatura alta (CaCOSTA). Estes filmes cerâmicos porosos foram depositados sobre o substrato cerâmico denso de YSZ, utilizado como eletrólito, componente estrutural do módulo, assim conferindo uma configuração de meia-célula denominada auto-suporte. O estudo da meia-célula é fundamental, pois na interface catodo/eletrólito ocorre a reação de redução do oxigênio, conseqüentemente influenciando no desempenho da CaCOSTA. Neste sentido, o presente trabalho contribui para a síntese de pós de LSM e LSM/YSZ e para o processamento de filmes finos, utilizando a técnica de pulverização de pó úmido, adotada para a conformação dos filmes cerâmicos por permitir a obtenção de camadas porosas com espessuras variadas na ordem de micrômetros. Os pós de LSM foram sintetizados pela técnica de citratos e os pós de LSM/YSZ pela técnica de mistura de sólidos. Na etapa de conformação foram preparadas suspensões orgânicas de LSM e LSM/YSZ alimentada por gravidade em um aerógrafo manual. Para a conformação do substrato de YSZ utilizou-se uma prensa uniaxial hidráulica. Foram possíveis a obtenção das meia-células de óxido sólido catodo/eletrólito de estruturas cristalinas hexagonal para a fase LSM e cúbica para a fase YSZ. E as micrografias das meia-células mostram que o substrato YSZ é denso, suficiente para ser utilizado como eletrólito sólido, e os filmes de LSM e LSM/YSZ apresentam-se porosos com espessura de aproximadamente 30 μm e com boa aderência entre os catodos e o eletrólito. A presença do catodo compósito entre o catodo LSM e o substrato YSZ, possibilitou um aumento no desempenho eletroquímico na reação de redução do oxigênio.The ceramic films of strontium-doped lanthanum manganite (LSM) and strontiumdoped lanthanum manganite/yttria-stabilized zirconia (LSM/YSZ) are used as cathodes of the high temperature solid oxide fuel cells (HTSOFC). These porous ceramic films had been deposited on the YSZ dense ceramic substrate, used as electrolyte, structural component of the module, thus conferring a configuration of half-cell called auto-support. The study of the half-cell it is basic, therefore in the interface cathode/electrolyte occurs the oxygen reduction reaction, consequently influencing in the performance of the HTSOFC. In this direction, the present work contributes for the processing of thin films, using the wet powder spraying technique, adopted for the conformation of the ceramic films for allowing the attainment of porous layers with thicknesses varied in the order of micrometers. The LSM powders were synthesized by the citrate technique and the LSM/YSZ powders synthesized by the solid mixture technique. In the stage of formation were prepared organic suspensions of LSM and LSM/YSZ fed by gravity in a manual aerograph. For the formation of the YSZ substrate was used a hydraulical uniaxial press. The attainment of solid oxide half-cells cathode/electrolyte was possible of crystalline structures hexagonal for phase LSM and cubic for phase YSZ. The half-cells micrographs show that the YSZ substrate is dense, enough to be used as solid electrolyte, and the LSM and LSM/YSZ films are presented porous with approximately 30 μm of thickness and good adherence between the cathodes and the electrolyte. The presence of composite cathode between the LSM cathode and YSZ substrate, presented an increase in the electrochemical performance in the oxygen reduction reaction.
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Kimpton, Justin Andrew. "Conductivity and microstructural characterisation of doped Zirconia-Ceria and Lanthanum Gallate electrolytes for the intermediate-temperature, solid oxide fuel cell /." 2002. http://adt.lib.swin.edu.au/public/adt-VSWT20060523.090655.
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Thesis (Ph.D.) - School of Engineering and Science, Swinburne University of Technology, 2002.Submitted in fulfillment of the requirements for the degree of Doctor of Philosophy, School of Engineering and Science, Swinburne University of Technology, 2002. Typescript. Includes bibliographical references (p. 229-239).
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Cetin, Deniz. "Thermodynamic stability of perovskite and lanthanum nickelate-type cathode materials for solid oxide fuel cells." Thesis, 2016. https://hdl.handle.net/2144/19501.
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The need for cleaner and more efficient alternative energy sources is becoming urgent as concerns mount about climate change wrought by greenhouse gas emissions. Solid oxide fuel cells (SOFCs) are one of the most efficient options if the goal is to reduce emissions while still operating on fossil energy resources. One of the foremost problems in SOFCs that causes efficiency loss is the polarization resistance associated with the oxygen reduction reaction(ORR) at the cathodes. Hence, improving the cathode design will greatly enhance the overall performance of SOFCs.
Lanthanum nickelate, La2NiO4+δ (LNO), is a mixed ionic and electronic conductor that has competitive surface oxygen exchange and transport properties and excellent electrical conductivity compared to perovskite-type oxides. This makes it an excellent candidate for solid oxide fuel cell (SOFC) applications. It has been previously shown that composites of LNO with Sm0.2Ce0.8O2-δ (SDC20) as cathode materials lead to higher performance than standalone LNO. However, in contact with lanthanide-doped ceria, LNO decomposes resulting in free NiO and ceria with higher lanthanide dopant concentration.
In this study, the aforementioned instability of LNO has been addressed by compositional tailoring of LNO: lanthanide doped ceria (LnxCe1-xO2,LnDC)composite. By increasing the lanthanide dopant concentration in the ceria phase close to its solubility limit, the LNO phase has been stabilized in the LNO:LnDC composites. Electrical conductivity of the composites as a function of LNO volume fraction and temperature has been measured, and analyzed using a resistive network model which allows the identification of a percolation threshold for the LNO phase. The thermomechanical compatibility of these composites has been investigated with SOFC systems through measurement of the coefficients of thermal expansion. LNO:LDC40 composites containing LNO lower than 50 vol%and higher than 40 vol% were identified as being suitable to incorporate into full button cell configuration from the standpoint of thermomechanical stability and adequate electrical conductivity. Proof-of-concept performance comparison for SOFC button cells manufactured using LNO: La0.4Ce0.6O2-δ composite to the conventional composite cathode materials has also been provided. This thermodynamics-based phase stabilization strategy can be applied to a wider range of materials in the same crystallographic family, thus providing the SOFC community with alternate material options for high performance devices.
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Chen, Yu-Jen, and 陳佑任. "Investigation in Lanthanum Strontium Cobalt Zinc Iron Oxide of Solid oxide Fuel Cells cathode materials." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/16666073466547846840.
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碩士國立臺灣科技大學
機械工程系
96
This research was focused on the Cathode material, La0.6Sr0.4(Co1-x Znx)0.2Fe0.8O3-d(x=0.0、0.2、0.4、0.6、0.8、1.0), to go through the half-cell test with excellent electrical conductivity of the electrolyte Ce0.78Gd0.2Sr0.02O1.9-x(GDC+Sr) developed by our laboratory. The cathode porosity of test chip/fragment was controlled to be approximately 31.25±3% for evaluating the effect on polarization loss of cathode oxygen reduction reaction and electrical chemical reaction with electrochemical impedance spectroscopy (EIS). A combination of analytical techniques were applied X-ray diffraction for interpreting the crystal structure, scanning electron microscope (SEM) for examining micro-structures, thermo mechanical analyzer (TMA) for finding thermal expansion coefficient (TEC) and (DTA/TGA) thermal analyzers for analyzing the presence of Phase & Change. The variation in component of La0.6Sr0.4(Co1-x Znx)0.2Fe0.8O3-d analyzed by XRD was single-based Rhombohedral Perovskite, a=b=c. The lattice constant and volume were expanded when Zinc ionic substitutes for Cobalt ionic due to the radius of Zinc was 22% being wider than that of Cobalt. According to the statistics from (DTA/TGA) thermal analysis, there was no Phase & Change when x was 0.0~1.0 at 500~800℃ which meant the interface between cathode and electrolyte was stable. In addition, based on the statistics from thermo mechanical analysis, the thermal expansion coefficient of the bulk grew as the temperature increases. Moreover, the thermal expansion coefficient decreased from 16.8 to 13.31 10-6k-1 if Zinc substituted for Cobalt. On the basis of electrical chemical alternating electrical impedance atlas method (x = 0.4, 0.6, 0.8) when Cobalt was replaced by Zinc, the cathode electrical impedance of B-site in La0.6Sr0.4(Co1-x Znx)0.2Fe0.8O3-d series was low (0.273、0.240 & 0.15 Ωcm2，800℃). The difference of cathode electrical impedance (Co -> Zn) in the high frequency region was not obvious. However, among middle and low frequency regions, the imbalance of electric charge caused by adopting the valence two Zinc to B-site instead of Cobalt with floating valence created a lot of oxygen vacancies, accelerating the circulation. Electrons were provided by cobalt switching from valence two, three, to four as well, and therefore the electrical impedance of oxygen reduction reaction was low when coexistence of B-site Zinc and Cobalt. The trend of the testing result statistics was the same as that of electrochemical analysis; such as electric current-switched density of Tafel Curve, Polarization Curve, and Cyclic Voltammetry Curve. Among the components of LSCZF, La0.6Sr0.4(Co0.2 Zn0.8)0.2Fe0.8O3-d�� �nperformed the best because the cathode electrical impedance was quite low �v(0.15 Ωcm2，800℃) and the thermal expansion coefficient (13.95 10-6k-1) is lower than LSCZF0.0(16.8 10-6k-1). Additionally the catalysis was significantly imporoved, due to the higher electric current-switched density. The overall performance of La0.6Sr0.4(Co0.2 Zn0.8)0.2Fe0.8O3-d was found to be better than that of the precursor of La0.6Sr0.4Co0.2 Fe0.8O3-�����nand La0.6Sr0.4Zn0.2 Fe0.8O3-���n,and was proposed as an innovative solid oxide Cathode material with good compatibility and catalysis.
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Kan, Shih-hsuan, and 甘世暄. "Investigation of Lanthanum Praseodymium Strontium Cobalt Iron Oxide as Cathode Materials for Solid Oxide Fuel Cells." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/v4nun8.
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碩士國立臺灣科技大學
機械工程系
95
The perovskite-structured oxide La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF) was widely used as cathodic electrode material in SOFC, but, according to the high thermal expansion coefficient, La0.6Sr0.4Co0.2Fe0.8O3-δ need to be modified for better thermal matchness and electrical properties. In this study, praseodymium element which has smaller ionic radius substituted La site and lattice structure, microstructure, thermal expansion coefficient, conductivity, electric over potential, electrochemical reaction and catalysis activation were researched. In order to estimate the durability, the cell was operated under high temperature (800 ℃) for a long time (200 hr) to investigate the performance of cathodic electrode. From the XRD results, the higher praseodymium element doped specimeus posses higher content of am orthorhombic phase and co-exist with a rhombohedra phase in specimen. From the Differential thermal analysis(DTA), Endothermic peaks was not found when the specimeus were tested under dopant quantity of (z) ranging from 0.0 to 0.5 and temperature ranged from 200 to 900 ℃. From thermal mechanical analysis, as the testing temperature raised, thermal expansion increased linearly and ranged in 14.7∼15.98×10-6K-1. The conductivity of LPSCF tested by four-point probe resistance measurement did not affected by Pr doping content in LSCF. While tested under 600 ℃∼800 ℃, the conductivity of LPSCFmaintained at 220 S/cm which is higher than those of LSM and LSF material systems performed. The overpotential behavior and AC impedance analysis of (La0.7Pr0.3)0.6Sr0.4Co0.2Fe0.8O3-δ under 800 ℃ showed the overpotential and polarization resistance of 11.7 mV and 2.3 Ω•cm2, respectively. As the specimens were tested in reduction environment, high density of exchanging current of about 20.05 mA/cm2 was achieved, suggesting that LPSCF provided high cathodic reaction zones junctions and numerous diffusing pathways for oxygen ions to access triple phase boundary. Specimens were tested under 800 ℃ for 200 hours to investigate the decaying condition, the performance of LPSCF, such as thermal expansion coefficient, conductivity, over potential, polarization resistance, catalysis activation and aging ability were superior to those of La0.6Sr0.4Co0.2Fe0.8O3-δ .
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Banner, Jane Elise. "Cathode polarization effects in rare Earth nickelate cathodes for solid oxide fuel cells." Thesis, 2020. https://hdl.handle.net/2144/41475.
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The US navy has a critical need for air independent advanced electric power sources to replace batteries in unmanned undersea vehicles (UUVs). Solid oxide fuel cells (SOFCs) are being considered as one potential replacement option. However, SOFCs typically operate using atmospheric air as their oxidant which is not an option for this underwater application. For this application, pure pressurized oxygen would be used as the oxidant which motivates the search for a cathode material which would be optimal for a high oxygen partial pressure environments.
Specifically, this research focuses on cathode materials which can exploit the unique operating conditions required for UUVs. The operation in 100% oxygen atmosphere rather than air provides a significant opportunity. This is because oxygen surface exchange and bulk transport through the cathode is mediated through point defects whose concentrations are sensitive to the partial pressure of oxygen in the atmosphere surrounding the cathode. Oxygen bulk transport along with oxygen surface exchange are the rate controlling steps in oxygen reduction and incorporation at the cathode. The focus of this research is to examine the relationship between oxygen partial pressure and its effect on SOFC cathode performance for two different families of cathode materials, namely strontium doped lanthanum manganite, and a relatively new class of cathode materials, rare-earth nickelates. The experimentally measured relationship between cathode polarization and oxygen partial pressure will be correlated with the underlying transport and surface exchange processes in both families of materials.
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Yu, Ho-Chieh, and 余河潔. "Investigation of Using Perovskite Sr-doped Lanthanum Cuprate as Cathode Materials for Intermediate-Temperature Solid Oxide Fuel Cells." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/04848309923654541755.
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博士國立成功大學
材料科學及工程學系碩博士班
93
ABSTRACT Oxygen-defifcent perovskite type oxides La1-xSrxCuO2.5-δ (LSCu) have been synthesized in the composition range of 0.15�Tx�T0.25. Due to their high electrical conductivity (800 S/cm at 800oC) and high oxygen vacancy concentration (��16.67%), these materials are characterized as new cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). First, the structural and electrical properties of lanthanum copper oxide were examined as a function of strontium addition. It was observed that the lanthanum oxide and copper oxide formed La2CuO4 with K2NiF4 structure and exceeds CuO when the powder mixture was calcined at 960oC in ambient pressure. As the strontium was doped from 0% to 25% , the calcined powder mixtures were phase transformation from La2CuO4/CuO mixture to orthorhombic perovskite La0.85Sr0.15CuO2.5-δ to tetragonal perovskite La1-xSrxCuO2.5-δ (x=0.2 and 0.25). Based on the titration analyses and pertinent defect reactions, the enhancement of perovskite stability is due to the presence of electron holes by strontium addition. As the strontium ions were added and occupied the lanthanum lattice sites, negative effective defects SrLa' were formed. The positive effective defects—electron holes were created and associated with divalent ions to form trivalent copper ions and balance the electrical charge by strontium doped. The formation of trivalent copper ions decrease the mean radius of the copper ions and increase the bonding strength of the copper ions toward their neighbor oxygen ions. Therefore, the perovskite structure of the LSCu was enhanced. When the Sr dopant exceeded its solubility limit of approximately 25% in the A-site sublattice, the Sr-rish second, La2SrCu2O6 and Cu2SrO3 appeared. Then the thermal expansion, cathodic overpotential, structural stability of LSCu against yittria-stabilized zirconia (YSZ) and the polarization resistance of the LSCu/YSZ interface were examined. The thermal expansion coefficients of LSCu, calculated by fitting the dilatometric curves, are in the range of 1.68�e10-5 to 1.79�e10-5 K-1 from 20 to 800oC. LSCu show no reaction against 8YSZ at 800oC for 1000 hours. However reaction between LSCu and YSZ occurred at 900oC. According to overpotential measurement and as impedance analyses, it can be suggested that the high oxygen vacancy concentration of LSCu provides numberous pathways for the diffusion of oxygen ions from electrode surface to air-electrode-electrolyte triple phase boundary and electrode/electrolyte interface. Hence, as the LSCu/YSZ/Pt half cell operating at 800oC and after passing a current of 200 mA/cm2 , it exhibits a good overpotential behavior of about 12.6 mV and a low polarization resistance of 0.25Ω at LSCu/YSZ interface. Lastly, the porous LSCu layers were applied on the anode-supported substrate with YSZ electrolyte thin film for the IT-SOFC single cell performance testing. The maximum power density of the cell operating at 800oC with 150 and 500 sccm of hydrogen and air flow, respectively, is about 0.65 W/cm2. For further improvement of the cell by applying a dense samaria-doped ceria (SDC) layer as cathode/electrode interlayer, the maximum power density of the cell was enhanced to 0.87 W/cm2. According to these results, LSCu is a potential new cathode material for IT-SOFC.
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Gasparyan, Hripsime. "Apatite based materials for solid oxide fuel cell (SOFC) and catalytic applications." Thesis, 2011. http://hdl.handle.net/10889/5563.
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Low cost silicates with apatite-structure (general formula of apatite A10-xM6O26±δ, where A = rare earth or alkaline earth and M= Si, Ge, P, V..) have been proposed recently as promising solid electrolyte materials (oxygen ion conductors) for use at intermediate temperature solid oxide fuel cells (SOFCs). These materials exhibit sufficiently high ionic conductivity (e.g. ~ 0.01 S cm-1 at 700 oC), which is dominated by the interstitial site mechanism and can exceed that of yttria-stabilized-zirconia (YSZ), the solid electrolyte used in state-of-the-art SOFCs. The apatite structure is tolerant to extensive aliovalent doping, which has been applied for improving ionic conductivity. In this work are presented results concerning synthesis, conductivity and catalytic characterization of Fe- and/or Al-doped apatite type lanthanum silicates (ATLS) of the general formula La10-zSi6-x-yAlxFeyO26±δ as well as electrochemical characterization of interfaces of ATLS pellets with perovskite and Ni-based electrodes. The aim was to investigate the properties of these ATLS material, in particular as it concerns their potential use as SOFC components or as catalysts in oxidation reactions.
The conductivity of pellets prepared from ATLS powders synthesized via four different methods and having different grain size was measured under air and at different temperatures in the range 600 -850 oC, aiming to identification of the effect of composition (doping), method of synthesis, grain size and pellet sintering conditions. For electrolytes of the same composition, those prepared via mechanochemical activation exhibited the highest conductivity, which was improved with increasing Al- and decreasing Fe-content.
In state-of-the-art SOFCs perovskite electrodes are used as cathodes and Ni-based electrodes as anodes, thus electrochemical characterization of perovskite and Ni-based/ATLS interfaces was carried out. As it concerns perovskite/ATLS interfaces, the characterization focused on the study of the open circuit AC impedance characteristics of a La0.8Sr0.2Ni0.4Fe0.6O3-δ/La9.83Si5Al0.75Fe0.25O26±δ interface, at temperatures 600 to 800 oC and oxygen partial pressures ranging from 0.1 to 20 kPa. Under the aforementioned conditions, it was observed that the impedance characteristics of the interface were determined by at least two different processes, corresponding to two partially overlapping depressed arcs in the Nyquist plots. The polarization conductance of the interface was found to increase with increasing temperature as well as with increasing oxygen partial pressure, following a power law dependence. The electrochemical characterization of Ni-based electrodes/ATLS interfaces involved study of the electrochemical characteristics of NiO-apatite cermet electrodes as well as a Ni sputtered electrode interfaced with Al- or Fe-doped apatite electrolytes, under hydrogen atmospheres. The impedance characteristics of these electrodes were found to be determined by up to three different processes, their relative contribution depending on the electrode microstructure, Ni content (as it concerns the cermet electrodes), temperature, hydrogen partial pressure and applied overpotential.
Aiming to investigation of potential catalytic properties of ATLS materials the catalytic activity for CO combustion of a series of ATLS powders was studied. For this purpose, two series of apatite-type lanthanum silicates La10-xSi6-y-zAlyFezO27-3x/2-(y+z)/2 (ATLS), undoped or doped with Al and/or Fe, were synthesized via sol-gel and modified dry sol-gel methods and tested as catalysts for CO combustion. The experiments revealed that the ATLS powders were catalytically active for CO combustion above approximately 300 oC, with light-off temperatures T50 (50% conversion of CO) ranging from 505 to 629 oC. The study focused on the effect on catalytic activity of the synthesis method and doping with Al and/or Fe. Non-doped ATLS with stoichiometric structure, namely La10Si6O27 prepared via the sol-gel method, exhibited the highest catalytic activity for CO oxidation among all tested compositions, the comparison being based on the measured catalytic rate (expressed per surface area of the catalyst) under practically differential conditions. Compared to La-Sr-Mn-O and La-Sr-Co-Fe-O perovskite powders, the tested ATLS powders exhibited lower catalytic activity for CO oxidation.-