An important challenge for PEMFC is stability and durability of the membrane separator. In this dissertation, we applied both experimental and modeling methods to investigate the chemical durability of PFSA membranes for fuel-cell applications. Degradation data were collected after Fenton's tests and the membrane samples were analyzed by XPS after Fenton's test; FTIR was also invoked to validate the XPS results. The effects of Fe2+ concentration and temperature on membrane degradation were discussed. The experimental results provide evidence of chemical attack of the CF2 backbone. Since the level of H2O2 was found to be key to membrane degradation, we designed a novel spectrophotometric method to quantitatively determine H2O2 concentration in a fuel cell by using a multilayer MEA. In addition, a model for H2O2 formation, transport, and reaction in PEMFCs is established for the first time to validate experimental data and study formation mechanism. The humidity effect on membrane degradation was studied by collecting vent water during the tests. The membrane conductivities and mechanical properties were measured by ex-situ high-throughput instruments. FTIR was applied to study both the formation of new groups and the relative abundance of existing groups in the degraded membrane. The thermal stability of degraded membranes was determined by TGA. The cross section of a degraded MEA sample was imaged with SEM to investigate the mechanical structure change. The effect of temperature on membrane degradation was also investigated. XPS spectra were collected from both anode and cathode sides of fuel-cell membrane to compare the effect of temperature on each side. Atomic analysis was performed to study the impact of temperature on both backbone decomposition and side group degradation. A multilayer MEA was used to study the effects of location and thickness on membrane degradation. An improved kinetic model of membrane degradation was built to simulate the experimental data. Finally, an attempt to mitigate membrane degradation by using peroxide decomposition reagent was performed. OCV curves were recorded during two fuel-cell durability tests with and without the addition of this additive. Both FER and TER were compared. Recommendations for the improvement of peroxide decomposition additive were suggested.

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第24002号 / エネ博第438号 / 新制||エネ||83(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)准教授 高井 茂臣, 教授 萩原 理加, 教授 佐川 尚 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Joseph B. Schlenoff, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Feb. 1, 2006). Document formatted into pages; contains xvii, 167 pages. Includes bibliographical references.

Le silicium se présente comme un bon candidat d’électrode négative pour améliorer la densité d’énergie des accumulateurs Li-ion ou rendre les microaccumulateurs compatibles avec le procédé de brasure à refusion qui nécessite un recuit à 260 °C. En effet, il présente une forte capacité spécifique (3759 mAh.g-1) et sa température de fusion est élevée (1410°C). Néanmoins, de fortes variations volumiques se produisent lors du processus de lithiation/délithiation pouvant atteindre 280 %, ce qui constitue un frein majeur à son développement. Ces travaux de thèse se focalisent sur l’étude approfondie du comportement électrochimique du silicium préparé sous forme de couche mince par pulvérisation cathodique. Cette nanostructuration limite la décrépitation de la matière active, et évite l’utilisation de charges et de liants. Ainsi, elle permet d’étudier plus finement le comportement intrinsèque du matériau et révèle des phénomènes en général non détectables avec les électrodes composites. / Silicon which has a theoretical capacity of 3579 mAh.g-1 and low insertion/deinsertion potentials is one of the most promising candidates to replace graphite as a negative electrode in lithium-ion batteries. Moreover, silicon could replace lithium in microbatteries to make them compatible with the solder-reflow. However, this high capacity associated with a dense material leads to high volumetric variations which are a starting point to various issues resulting in poor cycle performances. During this thesis, electrochemical behavior of silicon is evaluated on thin films electrodes. This allows avoiding the use of binder and charges, and it leads to better cycle performances which emphasizes slow phenomenon, not yet measurable on conventional composite electrode.

Au vu d’une demande croissante pour un stockage d’énergie à grande échelle, il est préférable de se tourner vers des matériaux peu coûteux et répandus. De ce point de vue, le sodium, qui présente des caractéristiques très proches de celles du lithium, présente également l’avantage d’être peu coûteux, abondant et réparti uniformément dans le monde. Cette thèse porte sur l’étude d’un système complet Na-ion constitué d’un carbone dur à l’électrode négative et d’un oxyde lamellaire à l’électrode positive. Un volet sur l’électrolyte a également été abordé.Concernant l’électrode négative, l’influence de la température de pyrolyse de la cellulose sur la structure des carbones durs et sur les performances électrochimiques a été étudiée. Une graphitisation localisée, une fermeture des pores et une évolution de la porosité interne avec la température de pyrolyse ont pu être observées. Les meilleures performances électrochimiques ont été obtenues pour le matériau synthétisé à 1600 °C : une capacité réversible d’environ 300 mAh.g-1 stable sur 200 cycles est atteinte à 37,2 mA.g-1 avec une efficacité coulombique initiale de 84 %. Pour mieux comprendre les mécanismes d’insertion du sodium dans ces matériaux, des études par spectroscopie d’impédance, SAXS et EDX ont été réalisées sur des carbones durs cyclés à différents potentiels.Le matériau d’électrode positive choisi est l’oxyde lamellaire Na0,6Ni0,25Mn0,75O2. L’influence de la température de calcination a permis de faire varier le nombre de défauts d’empilement de type P3 au profit d’une phase P2 plus cristalline. Après avoir optimisé l’électrolyte à base de carbonates pour garantir la reproductibilité des tests oxyde lamellaire//sodium métal, une capacité d’oxydation de 130 mAh.g-1 a pu être atteinte au premier cycle avant de chuter fortement sur les 40 cycles suivants. Cette perte de capacité a pu être en partie expliquée par des études de DRX operando. Enfin, ces travaux ont permis d’aboutir à des systèmes complets Na-ion dont les premiers résultats sont prometteurs. / Because of the development of renewable energy and electric vehicles, the need for a large scale energy storage has increased. This type of storage requires a large amount of raw materials. Therefore low cost and abundant resources are necessary. Consequently the use of sodium batteries is of interest because sodium’s low cost, high abundance, and worldwide availability. This PhD thesis deals with the study of a full Na-ion cell containing a hard carbon negative electrode, and a layered oxide positive electrode. A shorter part concerns the electrolyte.Concerning the negative electrode, the first objective was to understand in detail the influence of the pyrolysis temperature of a hard carbon precursor, cellulose, on the final structure of the material and its consequences on the electrochemical performance. Many techniques were used to characterize the hard carbon structure as a function of the pyrolysis temperature. Localized graphitization, pore closure, and an increase in micropore size have been observed with increasing temperature. The best electrochemical performance has been reached with the hard carbon synthesized at 1600°C: a reversible capacity of around 300 mAh.g-1 stable over 200 cycles is obtained at 37.2 mA.g-1 with an initial coulombic efficiency of 84%. To deeper understand sodium insertion mechanisms in hard carbon structures impedance spectroscopy, SAXS and EDX were carried out on hard carbon electrodes cycled at different voltages.The layered oxide Na0.6Ni0.25Mn0.75O2 was investigated as the positive electrode. It was observed that with increasing calcination temperature the number of P3-type stacking faults decreases in favor of a more crystalline P2 phase. Then, the carbonate-based electrolyte has been optimized to guarantee the reproducibility of the electrochemical tests performed in a layered oxide//sodium metal configuration. A first oxidation capacity of around 130 mAh.g-1 is reached. However this value drops quickly after 40 cycles. Operando XRD analysis did partially explain the capacity decrease. Finally, the results of these investigations were used to design an optimized full cell which demonstrated promising performance during initial testing.

Many countries including Sweden are planning to replace fossil fuel-based vehicles with electric vehicles. This is one of the main reasons that companies all over the world are investing more and more money in the development of lithium-ion batteries, for electric vehicles. There are several different risks with the conventional lithium-ion batteries including the high flammability of the electrolytes, which can lead to high heat release rate, risk of explosion and high toxicity in the form of hydrogen fluoride gas. The hydrogen fluoride is lethal even at low concentration. These potential risks are based on the structure of the flammable electrolytes inside the lithium-ion batteries. Because of that, there is a big interest in finding an electrolyte with similar battery performance and better fire properties as compared with the conventional electrolytes commercially available on the market.   The intent with this work is to investigate the fire properties of different halogen-free electrolytes. The two newly developed salts Li[MEA] & Li[MEEA] as well as the available salt Li[BOB] will be compared with the commercially used halogen-containing electrolyte based on lithium hexafluorophosphate (LiPF6) salt.   Physical and electrochemical properties of these electrolytes such as solubility in different organic solvents, density, viscosity, ionic conductivity and electrochemical window will be studied in the first step. The electrolytes showing the most promising electrochemical properties will then be further investigated regarding fire properties, heat release rate, flash point and toxicity. The electrolytes will be compared with the conventional electrolyte containing LiPF6.   Li[BOB] was not dissolved in the solvents with the strongest dissolving properties, therefore it was not further tested. The electrolytes that were tested regarding fire properties were Li[MEA] and Li[MEEA] with the organic solvents of ethylene carbonate and dimethyl carbonate. Ionic liquid was also added to Li[MEEA] to investigate how it affected the fire properties for the electrolyte.   When examine the heat release rate for the newly developed salts, as well as LiPF6, it was observed that the highest peaks were similar to each other. The combustion time for the electrolyte containing LiPF6 was noticeable shorter than for the other three electrolytes. This is likely due to the fluorine content in LiPF6. The electrolytes undergoing the cone calorimeter test in this work was not charged so therefore the peaks of the heat release rate may look different. For further studies, it could be of interest to construct a complete lithium-ion battery using these electrolytes to see how the battery cells and the electrolytes behave in different set of charges.   Another essential point, is the ignition time that showed varied times for the tests containing Li[MEEA] together with the organic solvents and with the added ionic liquid. This is an interesting result that probably can be explained by the homogeneity of the electrolyte. The homogeneity was only verified with the help of the human eye and therefore it may not be fully dissolved.   The flashpoint for the different mixtures of electrolytes showed values of interest where the electrolyte containing ionic liquid that showed the lowest flashpoint. This was unexpected concerning that these types of additives are common for improving the fire resistance capacity.   The key aspect discussed when analyzing the result from the FTIR spectroscopy was how the Li[MEA], Li[MEEA] and LiPF6 salts varied. The ones that did not have any fluorine in its structure resulted in production of carbon dioxide. However, the electrolyte containing fluorine resulted, as expected, in values of hydrogen fluorine and carbon dioxide but also other combustion products that was hard to determine.   These salts and electrolytes need to be further studied and tested to see if it is possible to use them in an actual lithium-ion battery. Besides further tests of the salts and ionic liquid tested in this work, it is important that the work with conventional and newly developed electrolytes aims for improvements in fire resistance as well as toxicity. / Många länder inklusive Sverige planerar att byta ut fordon som använder fossila bränslen mot elfordon. Detta är en av huvudanledningarna till att företag runt om i världen satsar mer och mer pengar på att utveckla litiumjonbatterier för elfordon. Litiumjonbatterier medför en del risker såsom hög värmeutveckling, brandfarliga vätskor, risk för explosion och toxiska gaser samt produceringen av vätefluorid. Redan vid låga koncentrationer är vätefluoriden dödlig. Riskerna baseras på strukturen av elektrolyten som finns i litiumjonbatteriet. På grund av dessa risker så är det intressant att utveckla en elektrolyt som har liknande batteriegenskaper men bättre brandegenskaper än de elektrolyter som finns och används idag.   I detta arbete har brandegenskaper för olika halogenfria elektrolyter testats. De två nyutvecklade salterna Li[MEA] & Li[MEEA] har tillsammans med det existerande saltet Li[BOB] jämförts med det kommersiella saltet litium hexafluorfosfat (LiPF6) som används till många elektrolyter i dagens litiumjonbatterier.   De fysiska och elektrokemiska egenskaperna såsom löslighet i organiska lösningsmedel, densitet, viskositet, jonkonduktiviet och elektrokemiskt fönster har testats för elektrolyterna i den första delen av arbetet. Elektrolyterna som uppvisade de mest lovande elektrokemiska egenskaper har även testats med avseende på brandegenskaperna, så som värmeutveckling, flampunkt och toxicitet. Elektrolyterna jämfördes mot den vanligt förekommande elektrolyten som innehåller litium hexafluorfosfat.   Saltet Li[BOB] löstes inte i lösningsmedel med bra lösningsegenskaper, vilket var anledningen till att det inte genomfördes ytterligare tester på den. Elektrolyterna som det genomfördes tester på avseende på brandegenskaper innehöll Li[MEA] och Li[MEEA] tillsammans med de organiska lösningsmedlen etylenekarbonat och dimetylkarbonat. För Li[MEEA] tillsattes det även jonvätska för att undersöka hur jonvätskan påverkar brandegenskaperna för elektrolyten.   När värmeutveckling för det nyutvecklade salterna och LiPF6 undersöktes, så uppvisade de liknande värden. Anmärkningsvärt var dock att förbränningstiden för LiPF6 varade under en kortare period i jämförelse med de tre andra elektrolyterna. En trolig orsak till detta är att LiPF6 innehåller fluor. Elektrolyterna som provades i konkalorimeter i detta arbete var ej laddade, vilket kan medföra att värmeutvecklingen kan se annorlunda ut vid ett laddat tillstånd. För framtida studier kan det vara intressant att konstruera ett komplett litiumjonbatteri, för att se hur elektrolyterna fungerar och påverkas, beroende på laddningsnivå.   Antändningstiden för Li[MEEA] blandat med de organiska lösningsmedlen tillsammans med jonvätska varierade mycket. Detta är ett intressant resultat, som förmodligen kan förklaras av homogeniteten på elektrolyten. Homogeniteten verifierades enbart okulärt, vilket inte säkerställer att jonvätskan har löst sig fullständigt i elektrolyten.   Resultat för flampunkten för det olika elektrolyterna var intressant, då elektrolyten som innehöll jonvätska visade på lägst flampunkt. Detta var oväntat då tillsatser som jonvätska brukar förbättra brandmotståndet.   Resultatet för FTIR-spektroskopin analyserades för att se hur Li[MEA], Li[MEEA] och LiPF6 skiljde sig åt. De elektrolyter som inte innehöll fluor, producerade bara koldioxid. Medans elektrolyten som innehöll fluor producerade, som väntat, vätefluorid och koldioxid, men även andra gaser som var svåranalyserade.   De framtagna elektrolyterna i detta arbete behöver studeras vidare och fler tester bör genomföras för att se om det finns en möjlighet att använda dem i faktiska litiumjonbatterier. Förutom att testa elektrolyterna i just detta arbete är det viktigt att forskningen kring brandegenskaper och toxiska egenskaper för elektrolyter fortsätter i framtiden.

Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2012-11-19T18:59:36Z No. of bitstreams: 1 Atila dos Santos Batista. Papel dos receptores....pdf: 4517971 bytes, checksum: 2d9cb0d434dcb66027ca90861bbd1a75 (MD5) / Made available in DSpace on 2012-11-19T18:59:36Z (GMT). No. of bitstreams: 1 Atila dos Santos Batista. Papel dos receptores....pdf: 4517971 bytes, checksum: 2d9cb0d434dcb66027ca90861bbd1a75 (MD5) Previous issue date: 2012 / Fundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, Bahia, Brasil / Diferentes áreas do sistema nervoso central que participam da regulação cardiovascular recebem projeções de núcleos da rafe produtores de 5-HT. Diversos estudos têm também demonstrado a participação dos receptores serotoninérgicos nas respostas neuroendócrinas e emocionais ao estresse e no equilíbrio hidrossalino, assim os objetivos do referido trabalho foram: a) estudar o papel dos receptores do tipo 5-HT3 presentes na ASM (área septal medial) sobre as respostas cardiovasculares ao estresse de contenção em ratos; b) verificar a possível interação entre os receptores colinérgicos muscarínicos e 5-HT3 presentes na ASM no controle cardiovascular; c) verificar o papel dos receptores do tipo 5-HT3 na ASM sobre o controle hidrossalino. Foram utilizados ratos Wistar (280-300g) submetidos ao implante de uma cânula guia na ASM. Os animais destinados aos estudos cardiovasculares receberam implante de catéter carotídeo para análise da PA. No momento do experimento referente ao estresse os animais receberam injeção de m-CPBG e ondansetrona na ASM e 15 min após a microinjeção foram submetidos ao estresse de contenção com registro da PA. Para análise da interação entre os receptores muscarínicos e os receptores serotoninérgicos do tipo 5-HT3 os animais receberam previamente atropina, antagonista colinérgico muscarínico, e após 10 min receberam ondansetrona com registro constante da PA por mais 110min. No protocolo experimental para depleção de sódio os animais receberam microinjeções de furosemida 24h antes do experimento tendo disponíveis bebedouros de água destilada. No momento do experimento os animais receberam microinjeções de m-CPBG e ondansetrona e após 15 min os volumes de água e salina 1,5% foram registrados por 2h. Para análise do efeito do bloqueio dos receptores 5-HT3 sobre o comportamento de ingestão de água os animais foram submetidos a privação hídrica por 24h. No momento do experimento microinjeções de salina, m-CPBG ondansetrona foram feitas na ASM com medida dos volumes ingeridos ao longo de 2h. Verificamos que os receptores serotoninérgicos do tipo 5-HT3 presentes na ASM inibem o aumento da PA em animais submetidos ao estresse, além disso, verificamos também que a resposta hipertensiva decorrente do bloqueio dos receptores serotoninérgicos do tipo 5- HT3 depende da integridade funcional dos receptores colinérgicos muscarínicos. Por outro lado, tanto a ativação, quanto o bloqueio dos receptores serotoninérgicos do tipo 5-HT3 presentes na ASM parecem não mediar a ingestão de sódio em animais sódio-depletados nem a ingestão de água em animais sob privação hídrica. / Different areas of the central nervous system that participate in cardiovascular regulation receive the projections of rafe nuclei that product 5-HT. Several studies have also demonstrated the participation of serotoninergic receptors in neuroendocrine and emotional responses for stress and in fluid and electrolyte balance. Thus, the objectives of this work were: a) to study the role of type 5-HT3 receptors present in MSA (medial septal area) on the cardiovascular responses to stress of restraint in rats; b) to verify the possible interaction between muscarinic cholinergic receptors and 5-HT3 present in MSA in cardiovascular control; c) to verify the role of type 5-HT3 receptors in MSA on fluid and electrolyte control. There were used Wistar rats (280-300g) submitted to a guide cannula implant in MSA. The animals for cardiovascular studies received carotid catheter implant to AP analyses. At the time of stress experiment the animals received m-CPBG and ondansetron injection in MSA and, 15 minutes after microinjection were submitted to stress of restraint with the AP register. To analyses the interaction between the muscarinic receptors and 5-HT3 serotoninergic receptors, the animals previously received atropine, cholinergic muscarinic antagonist, and 10 minutes after received ondansetron with the constant register of AP for 110 minutes more. In the experimental protocol for sodium depletion animals received furosemide microinjections 24 hours before the experiment with distilled water drinking fountains available. At the time of the experiment the animals received m-CPBG and ondansetron injection and after 15 minutes the volumes of water and 1,5% saline were registered for two hours. To analyses the effect of 5-HT3 receptors blockade on the water ingestion behavior the animals had been submitted to water privation by 24 hours. At the time of the experiment microinjections of saline, m-CPBG and ondansetron were made in MSA with measurement of ingested volumes during two hours. We verified that the type 5-HT3 serotoninergic receptors present in MSA inhibit the increase of AP in animals on stress. In addition, we also verified that the hypertensive response due to the type 5-HT3 serotoninergic receptors blockade depends on the functional integrity of the muscarinic cholinergic receptors. On the other hand, both the activation as the blocking of type 5-HT3 serotoninergic receptors presents in MSA seem not to mediate sodium ingest in sodium-depleted animals nor the water ingestion in animals on water deprivation.

L'objectif de cette thèse est de développer et d'optimiser un électrolyte organique performant et sécuritaire pour supercondensateur. En effet, l'acétonitrile est un solvant couramment employé dans la conception des électrolytes, mais celui-ci étant inflammable, il faut lui trouver une alternative performante. Différentes familles de solvants ont été évaluées. Les solvants stables d'un point de vue électrochimique ont été sélectionnés en vue de leur utilisation dans des électrolytes. Dans le but de trouver un compromis entre mobilité et concentration ionique, des mélanges de solvants ont été réalisés. L'addition de solvants peu visqueux comme des esters ou le méthoxypropionitrile dans l'éthylène carbonate et le sulfolane ont permis d'obtenir des électrolytes performants. L'étude des interactions solvant / solvant et solvant / sel ont été menées par des mesures calorimétriques, viscosimétriques et spectroscopiques. Ces interactions, bien que de très faible amplitude, permettent d'augmenter notablement la température d'évaporation du solvant volatil de l'électrolyte, donc son point éclair. / The aim of this work is to to develop and optimize an efficient and safe organic electrolyte for supercapacitor. Indeed, acetonitrile is the solvent commonly used in supercapacitor electrolytes. Due to its flammable character, innovative solvents have to be developed. Several solvent families have been investigated. Thanks to an electrochemical study, stable solvents have been selected to be used in electrolytes. In order to find a compromise between mobility and ionic concentration, solvent mixtures have been studied. The addition of low viscous solvents, as ester and methoxypropionitrile in ethylene carbonate or sulfolane based electrolytes, permits to develop efficient electrolytes. The study of the interactions solvent / solvent and solvent / salt has been performed by calorimetric, viscosimetric and spectroscopic studies. Even if they are very weak, the interactions lead a neat increase of the boiling temperature of the more volatile solvent, thus the flash point.

La thèse est orientée à la production d'une membrane proton conductrice pour la pile à combustible à membrane proton électrolyte (PEMFC) comme un but principal. L'originalité et le challenge de l'élaboration de la membrane consistent en procédure multi-étape : commencer avec la synthèse de l'unité simple – un monomère ionique, continuer avec la polymérisation et l'estimation générale de performance en échelle de laboratoire de polymère ; et finir avec la production des matériaux en échelle industrielle et tester en conditions réelles. Toutes les étapes, sauf la dernière, sont étudiées en détail. Premièrement, beaucoup d'attention est portée à la description du protocole de production et purification de monomères ioniques. C'est à cause de la complexité des interactions ioniques dans un système ‘produit-solvant' et dû à l'exigence principale pour la haute pureté du monomère que la synthèse et traitement attentifs des monomères doivent être faits. En total, trois nouveaux monomères, portants les chaines acides perfluorosulfoniques, sont proposés. Ensuite, plusieurs réactions de polymérisation avec les différents monomères non-ioniques commerciaux sont décrites. Deux familles différentes des membranes proton conductrices sont décrites : poly(arylene ether)s (PAEs) statistiques et poly(arylene ether sulfone)s statistiques et en bloc. Elles sont synthétisées en séries de CEI différentes pour pouvoir suivre l'impact du groupe ionique sur les propriétés des matériaux. De plus, la nouvelle structure d'ionomère est proposée, où le copolymère à bloc contient le bloc hydrophile, synthétisé de deux monomères, portants les groupes perfluorosulfoniques (PFSA). Ça permet d'approcher au maximum les groupes latéraux superacides le long de la chaîne, ce qui, le plus probablement, contribue vers la meilleur organisation t interaction entre les sites ioniques. Pour la caractérisation suivante des nouveaux polymères ils sont coulés en membranes par la méthode de coulée-évaporation de ses solutions en dimethylacétamide (DMAc). Influence de la température du processus est décrite brièvement. Les membranes de différentes séries sont comparées entre eux-mêmes et à Nafion comme le matériau de référence. C'est connu que Nafion acquiert sa haute performance dû à : i) présence du groupe latéral superacide PFSA et ii) organisation des chaînes de polymère aux domaines bien séparés de conducteurs de protons (hydrophiles) et stables mécaniquement (hydrophobes). Par contre, la production de ce matériau contient les procédures dangereuses et chères de manipulation avec les gases fluorés, car cet ionomère contient une chaîne de base de Teflon. De plus, la température de transition de squelette perfluorée est plus basse que la température de fonctionnement de ionomère dans PEMFC. Les nouveaux ionomères sont ensuite caractérisés pour les propriétés thermo-mécaniques, stabilité, conductivité, morphologie. Ils montrent : i) hautes températures de transitions, ce qui permet l'utilisation de ces polymères aux conditions de la fonctionnement de PEMFC ; ii) le phénomène de la séparation de phases, ce qui propose les matériaux d'avoir la morphologie avec les domaines bien définis pour la conduction des protons, iii) la structuration avec une organisation importante, ce qui est rare d'apercevoir pour les matériaux aromatiques ; iv) haute conductivité protonique même à l'humidité réduite pour plusieurs séries des polymères proposées. Par conséquent, les matériaux montrent la performance prometteuse, ce qui doit être vérifiée aux conditions réelles de la pile à combustible. De plus, ce travail est innovant par la procédure de production des ionomères, c'est pourquoi plus des différentes séries des polymères sont prévues à être synthètisées à partir des monomères ioniques proposés ici. La variation des monomères ioniques peut être élargie aussi par changement de PFSA groupes aux perfluorosulfonimides. / The current work is directed to production of a proton conducting membrane for a proton electrolyte membrane fuel cell (PEMFC) as a main goal. The originality and the challenge of the membrane elaboration lie in the multi-step procedure: starting with the synthesis of a simple unit – an ionic monomer, continuing with polymerization and overall estimation of the polymer performance at laboratory scale, and ending with production of the required material of industrial quantity and testing in real conditions. All the steps, except the last one, are explicitly studied. Firstly, much attention in the dissertation is paid to description of a protocol for production and purification of the ionic monomers. It is due to complexity of ionic interactions in a system ‘product-solvent' and due to the main requirement of high purity for a monomer that attentive synthesis and treatment of the monomers must be provided. In total three new monomers, bearing perfluorosulfonic acid chains, are reported. Then, a number of polymerization reactions with different commercial non-ionic monomers are proposed. Two main families of proton conducting ionomers are described: random poly(arylene ether)s (PAEs) and poly(arylene ether sulfone)s (PAESs), both random and block-copolymers. They are synthesized in series of different IEC in order to follow the impact of the ionic group to the properties of the material. Additionally, a new structure of the ionomer is proposed, where the block-copolymer contains a hydrophilic block, synthesized from two monomers, bearing perfluorosulfonic acid (PFSA) groups. It allows maximally approximating the superacid lateral groups along the polymer chain that, most probably, contributes to better organization and interaction between the ionic sites. For further characterization of the novel polymers, they are cast to membranes by casting-evaporation method from their solutions in dimethylacetamide (DMAc). The influence of production temperature is described briefly. The membranes of different series are compared between each other and to Nafion as a reference material. It is known that Nafion acquires its high performance due to: i) presence of superacid PFSA lateral groups, and ii) organization of polymer chains into well-separated proton-conductive (hydrophilic) and mechanically stable (hydrophobic) domains. However, production of this material comprises dangerous and expensive procedures of manipulation with fluorinated gases, since this ionomer contains a Teflon-type backbone. Moreover, transition temperature of the perfluorinated main chain is lower, than the required temperature of the ionomer functioning in a PEMFC. The novel ionomers are further characterized in terms of thermo-mechanical properties, stability, conductivity, bulk morphology. They exhibit: i) high transition temperatures, which allows utilization of these polymers at conditions of a PEMFC functioning; ii) phase separation phenomenon, which suggests the materials to have morphology with distinct domains for proton conduction, iii) highly organized structuring, which is rare to clearly evidence on aromatic materials; iv) high proton conductivity for several polymer series, which over-perform Nafion even at reduced humidity. Based on these results, some of the synthesized materials are considered to be promising in a PEMFC, but further study in real conditions must be provided. Additionally, the current work is pioneering in the way of production of the ionomers, therefore, more different series of polymers are previewed to be synthesized out of the ionic monomers, proposed here. Variety of the ionic monomers may be enlarged as well by changing the PFSA groups to perfluorosulfonimide ones or by searching for other fluorinated commercial materials that might be modified into monomers with two functional groups for polycondensation. Thus, the main objectives, set for the current work, are fulfilled.

Submitted by Aelson Maciera (aelsoncm@terra.com.br) on 2017-06-05T20:20:51Z No. of bitstreams: 1 TeseELP.pdf: 16549429 bytes, checksum: 8564c0e7a4dbc3f95cb21b3270edf754 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-06-06T18:43:55Z (GMT) No. of bitstreams: 1 TeseELP.pdf: 16549429 bytes, checksum: 8564c0e7a4dbc3f95cb21b3270edf754 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-06-06T18:44:56Z (GMT) No. of bitstreams: 1 TeseELP.pdf: 16549429 bytes, checksum: 8564c0e7a4dbc3f95cb21b3270edf754 (MD5) / Made available in DSpace on 2017-06-08T19:45:20Z (GMT). No. of bitstreams: 1 TeseELP.pdf: 16549429 bytes, checksum: 8564c0e7a4dbc3f95cb21b3270edf754 (MD5) Previous issue date: 2016-12-19 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The study of solid electrolytes (SE) is important to the scientific and technological development of materials used in application related to clean energy generation, such as Solid Oxide Fuel Cells (SOFCs). Yttrium-doped Barium Cerate is a SE with perovskite structure and great potential for this application because of its high values of protonic conductivity in temperatures between 350 and 600°C, which would allow the replacement of the currently used Zirconia based SE that operate above 800 °C, reducing the manufacturing cost of SOFCs. In the present work, eighteen compositions of BaCe1-xYxO3-δ system with x ranging from 0 to 0.2 were synthesized via modified citrate process and for half of the compositions an addition of 1 wt% ZnO as sintering aid was made. With the goal of establishing a correlation between structure, microstructure and electrical conductivity with the yttrium concentration and in the presence or absence of the sintering aid, all compositions were characterized with X-ray Powder Diffraction, Raman Spectroscopy, Scanning and Transmission Electron Microscopy (TEM), Energy-dispersive X-ray Spectroscopy (EDS) and Impedance Spectroscopy. Secondary phases were characterized using TEM, EDS and Electron Diffraction. All samples presented relative bulk density values above 95%. The bulk electrical conductivity is proportional to the yttrium concentration in the grain and, in general, the ZnO addition promoted grain growth, increasing its average size up to five times in some compositions. The ZnO acts mainly at the grain boundary region and it is effective as sintering aid only when the composition has some yttrium content. Among all synthesized compositions, BaCe0.8Y0.2O3-δ without ZnO addition showed the highest electrical conductivity value at 600°C (≈ 31.5 mS/cm). In the group of samples with ZnO, the highest values (close to 18.4 mS/cm), were obtained for compositions with Yttrium content above 14 at.%. / O estudo de eletrólitos sólidos (ES) é importante para o desenvolvimento científico e técnológico de materiais para aplicações relacionadas à geração de energia limpa, como por exemplo, células a combustível de óxido sólido (CaCOS). O cerato de bário dopado com ítrio é um ES com estrutura perovskita com grande potencial de aplicação por apresentar valores altos de condutividade protônica em temperatura entre 350 e 600 °C, o que possibilitaria substituir os atuais ES à base de Zircônia que operam acima de 800 °C, reduzindo o custo de fabricação das CaCOS. Neste trabalho, dezoito composições do sistema BaCe1-xYxO3-δ com x variando entre 0 e 0,2 foram sintetizadas via processo citrato modificado e para metade das composições, uma adição de 1% em massa de ZnO como aditivo de sinterização foi feita. Visando estabelecer uma correlação entre estrutura, microestrura e condutividade elétrica com a concentração de ítrio e a presença ou não de aditivo de sinterização, todas as composições foram caracterizadas por meio de difração de raios X, espectroscopia Raman, microscopia eletrônica de varredura e transmissão (MET), espectroscopia de raios X por dispersão em energia (EDS) e espectroscopia de impedância. Fases secundárias foram caracterizadas por MET, EDS e difração de elétrons. Todas as composições apresentaram valores de densidade relativa acima de 95%. A condutividade elétrica do grão é proporcional a concentração de ítrio na matriz e, no geral, a adição de ZnO favoreceu o crescimento de grão, aumentando o seu tamanho médio em até cinco vezes. O ZnO atua principalmente na região de contorno de grão e é eficiente como aditivo apenas na presença ítrio. Dentre as composições sintetizadas, a BaCe0,8Y0,2O3-δ sem ZnO apresentou o maior valor de condutividade a 600°C (≈ 31,5 mS/cm). No grupo das amostras com ZnO, os valores mais altos, próximos a 18,4 mS/cm, foram obtidos para composições com teor de Y acima de 14% at. / CNPq: 207073/2014-7 / CNPq: 160534/2012-7