Les verres du système binaire Ag₂S-As₂S₃ sont connus pour être de très bons conducteurs ioniques et l’ajout de HgI₂ permet d’envisager une application des verres du pseudo-ternaire HgI₂-Ag₂S-As₂S₃ en tant que membrane ionique spécifique dédiée au dosage du mercure en solution aqueuse. Les limites de son domaine vitreux ont été vérifiées à l’aide de la diffraction des rayons X. Les évolutions des propriétés macroscopiques des verres, incluant les densités et les températures caractéristiques (Tg, Tc et Tf) ont été analysées de façon systématique. Les propriétés de conduction des verres HgI₂-Ag₂S-As₂S₃ ont été évaluées à l’aide de la spectroscopie d’impédance complexe et de la diffusion du traceur radioactif 108mAg. Un des résultats les plus marquants dans ces verres conducteurs ioniques est l’augmentation de la conductivité lorsque Ag₂S est substitué par HgI₂. Afin de comprendre les mécanismes de conduction mis en jeu, des études structurales ont été menées par spectroscopie Raman, diffusion de neutrons et diffraction des rayons X haute énergie. Pour appréhender la structure de ces verres complexes, des études préalables sur les deux systèmes pseudo-binaires Ag₂S-As₂S₃ et HgI₂-As₂S₃ ont aussi été menées. Les différentes techniques utilisées ont notamment permis de montrer que des réactions d’échanges se produisaient lors de la synthèse. Enfin, la dernière partie de cette thèse est entièrement consacrée à la caractérisation de nouveaux capteurs chimiques pour la détection des ions Hg²+ en solution. Différentes compositions sont testées afin de définir la sensibilité, la limite de détection et les coefficients de sélectivité en présence d’ions interférents. / Glasses of the pseudo-binary system Ag₂S-As₂S₃ are well known to be good ionic conductors and the addition of HgI₂ allows considering the glasses of the pseudo-ternary system HgI₂-Ag₂S-As₂S₃ as ion-membrane dedicated to mercury sensing in aqueous solution. The limits of its vitreous domain were verified by X-ray diffraction. Changes in macroscopic properties of glasses, including density and characteristic temperatures (Tg, Tc et Tm) were systematically investigated. Conduction properties of HgI₂-Ag₂S-As₂S₃ glasses were evaluated using the complex impedance spectroscopy and 108mAg tracer diffusion measurements. One of the most interesting results concerns the conductivity increase if Ag₂S is substituted by HgI₂. To understand the conduction mechanisms involved, structural studies were carried out by Raman spectroscopy, neutron scattering and high-energy X-ray diffraction. To understand the structure of these complex glasses, preliminary studies on the two pseudo-binary systems Ag₂S-As₂S₃ and HgI₂-As₂S₃ were also undertaken. These techniques have underlined exchange reactions that occur during the synthesis. The last part of this research work is entirely devoted to the characterization of new chemical sensors for the detection of Hg²+ ions in solution. Different compositions were tested to determine the sensitivity, detection limit and selectivity coefficients in the presence of interfering ions.

Esta tese apresenta os resultados do estudo de eletrólitos poliméricos protônicos obtidos a base de gelatina e quitosana, modificadas através da adição de glicerol e formaldeído - ácidos acético ou clorídrico foram adicionados para promover a condutividade iônica dos filmes. Foram também preparadas blendas a partir de gelatina com quitosana, assim como filmes a base de gelatina e nanopartículas. Com exceção dos filmes com nanopartículas, todos eles possuem boa transparência, estabilidade térmica, maleabilidade, aderência ao vidro e apresentam uma superfície homogênea, sem trincas ou rachaduras. As temperaturas de transição vítrea (Tg) dos eletrólitos foram obtidas do estreitamento de linha de RMN. A taxa de relaxação spin-rede do \'ANTPOT. 1 H\' em função da temperatura mostrou um máximo bem definido cuja posição depende da concentração de ácido no caso da gelatina e da quantidade de glicerol no caso da quitosana, refletindo a alta mobilidade do próton nestes eletrólitos. As técnicas de RPE, onda contínua e pulsada, foram utilizadas para o estudo de eletrólitos dopados com \'CU\'CL\'O IND.4\'. Os valores de condutividade iônica dos eletrólitos são da ordem de \'10 POT.-5\' S/cm para os filmes de gelatina (com ácido acético ou clorídrico), quitosana e blendas e entre \'10 POT.-6\' a \'10 POT.-8\' para os eletrólitos de gelatina com nanopartículas. Estes estudos revelaram que a concentração de ácido acético ou clorídrico (na gelatina), influencia a condutividade iônica dos eletrólitos, mas, para o caso das blendas esta influência é pequena. No caso dos filmes de gelatina com nanopartículas, a condutividade diminui de forma significativa. Em relação aos eletrólitos de quitosana a condutividade iônica é influenciada pela quantidade de glicerol adicionado. Verificou-se que o aumento da temperatura até 80°C promove o aumento da condutividade iônica para todos os filmes estudados. / This thesis shows the results from the study of protonic polymer electrolytes obtained from gelatin and chitosan, modified by the addition of glycerol and formaldehyde - acetic and hydrochloric acids are added to promote the ionic conductivity of the films. Blends based on chitosan and gelatin were also prepared, as well as films based on gelatin and nanoparticles. With the exception of the films with nanoparticles, all samples presented good transparency, thermal stability, flexibility, adhesion to glass and homogeneous surface without cracks. The glass transition temperature (Tg) of the electrolytes were obtained from the NMR line narrowing. The spin-lattice relaxation rate of the \'ANTPOT. 1 H\' spin-network as a function of temperature showed a well-defined maximum whose position depends on the concentration of acid in the case of gelatin and on the glycerol content in the case of chitosan, reflecting the high mobility of the protons in the electrolytes. Continuous wave and pulsed EPR techniques were used to study the electrolytes doped with \'CU\'CL\'O IND.4\'. The values of the ionic conductivity of the electrolytes are of the order of \'10 POT.-5\' S/cm for the films of gelatin (with acetic or hydrochloric acids), chitosan and blends and from \'10 POT.-6\' to \'10 POT.-8\' for the electrolytes of gelatin with nanoparticles. These studies revealed that the concentration of acetic or hydrochloric acids (in gelatin), influences the ionic conductivity of the electrolytes but, in the case of blends, this influence is small. In the case of the films based on gelatin with nanoparticles, the ionic conductivity decreases significantly. In relation to the electrolyte based on chitosan, the ionic conductivity is influenced by the amount of glycerol added. It was found that increasing the temperature to 80°C promotes the increase of ionic conductivity for all films studied.

No description available.

The yttria-stabilized zirconia (YSZ) system has been extensively studied because of its critical applications, like solid oxide fuel cells (SOFCs), oxygen sensors, and jet engines. However, there are still important questions that need to be answered and significant thermodynamic information that needs to be provided for this system. There is no predictive tool for the ionic conductivity of the cubic-YSZ (c-YSZ), as an electrolyte in SOFCs. In addition, no quantitative diagram is available regarding the oxygen ion mobility in c-YSZ, which is highly effective on its ionic conductivity. Moreover, there is no applicable phase stability diagram for the nano-YSZ, which is applied in oxygen sensors. Phase diagrams are critical tools to design new applications of materials. Furthermore, even after extensive studies on the thermodynamic database of the YSZ system, the zirconia-rich side of the system shows considerable uncertainties regarding the phase equilibria, which can make the application designs unreliable. During this dissertation, the CALPHAD (CALculation of PHase Diagrams) approach was applied to provide a predictive diagram for the ionic conductivity of the c-YSZ system. The oxygen ion mobility, activation energy, and pre-exponential factor were also predicted. In addition, the CALPHAD approach was utilized to predict the Gibbs energy of bulk YSZ at different temperatures. The surface energy of each polymorph was then added to the predicted Gibbs energy of bulk YSZ to obtain the total Gibbs energy of nano-YSZ. Therefore, a 3-D phase stability diagram for the nano-YSZ system was provided, by which the stability range of each polymorph versus temperature and particle size are presented. Re-assessment of the thermodynamic database of the YSZ system was done by applying the CALPHAD approach. All of the available thermochemical and phase equilibria data were evaluated carefully and the most reliable ones were selected for the Gibbs energy optimization process. The results calculated by the optimized thermodynamic database showed good agreement with the selected experimental data, particularly on the zirconia-rich side of the system.

L'objectif principal de ce travail est de développer une nouvelle vitrocéramique structurée par NASICON avec une conductivité Li-ion élevée. Par conséquent, ce travail présente une nouvelle série de compositions de type NASICON sur la base du système Li1+xCrx(GeyTi1-y)2-x(PO4)3. Dans un premier temps, une composition spécifique de ce système a été synthétisée par la méthode de fusion et refroidissement rapide, suivie d'une cristallisation. Le comportement de cristallisation du verre précurseur a été examiné par calorimétrie différentielle à balayage et spectroscopie infrarouge. Les principaux résultats indiquent que le verre précurseur présente une nucléation homogène, a une stabilité de verre considérable et cristallise une phase de type NASICON, qui permet d'obtenir des électrolytes solides par voie vitrocéramique. Dans une deuxième étape, on examine l'effet de la substitution de Ti par Cr et Ge sur la stabilité de verre du verre précurseur, sur les paramètres structuraux de la phase cristalline NASICON et sur les propriétés électriques des vitrocéramiques. Par conséquent, un ensemble de seize compositions de ce système est synthétisé. Les principaux résultats indiquent que la stabilité de verre augmente lorsque Ti est remplacé par Ge et Cr. Après cristallisation, toutes les vitrocéramiques présentent une phase de type NASICON, et leurs paramètres de maille décroissent avec Ge et augmentent avec la teneur en Cr, ce qui permet de régler le volume de la cellule unitaire de la structure de type NASICON. De plus, la conductivité ionique et l'énergie d'activation pour la conduction du lithium dans les vitrocéramiques dépendent notamment du volume de la cellule unitaire de la structure de type NASICON. Enfin, la fenêtre de stabilité électrochimique de la vitrocéramique à structure NASICON de conductivité ionique la plus élevée est étudiée. Les mesures de voltampérométrie cyclique sont suivies par spectroscopie d'impédance électrochimique in situ, permettant de déterminer l'effet des réactions d'oxydation et de réduction sur les propriétés électriques des vitrocéramiques en question. La spectroscopie photoélectronique par rayons X, à son tour, est appliquée pour déterminer quelles espèces chimiques subissent une réduction/oxydation. Nos résultats révèlent que la stabilité électrochimique de ce matériau est limitée par la réduction des cations Ti+4 dans les faibles potentiels et par l'oxydation des anions O-2 dans les hauts potentiels. Aux hauts potentiels, un comportement similaire a également été rencontré pour d'autres conduites Li-ion de type NASICON bien connues, suggérant que le comportement électrochimique dans les potentiels oxydatifs pourrait être généralisé pour les phosphates à structure NASICON. / The primary goal of this work is to develop a new NASICON-structured glass-ceramic with high Li-ion conductivity. Therefore, this work introduces a new series of NASICON-type compositions based on the Li1+xCrx(GeyTi1-y)2-x(PO4)3 system. At first, a specific composition of this system is synthesized by the melt-quenching method, followed by crystallization. The crystallization behavior of the precursor glass is examined by differential scanning calorimetry and infrared spectroscopy. The main results indicate that the precursor glass presents homogeneous nucleation, has considerable glass stability and crystallizes a NASICON-like phase, which allows solid electrolytes to be obtained by the glass-ceramic route. As a second step, we examine the effect of substituting Ti by Cr and Ge on the glass stability of the precursor glass, on the structural parameters of NASICON-like phase and the electrical properties of the glass-ceramics. Hence, a set of sixteen compositions of this system is synthesized. The main results indicate that the glass stability increases when Ti is replaced by Ge and Cr. After crystallization, all the glass-ceramics present NASICON-like phase, and their lattice parameters decrease with Ge and increase with Cr content, making it possible to adjust the unit cell volume of the NASICON-type structure. Furthermore, the ionic conductivity and activation energy for lithium conduction in the glass-ceramics are notably dependent on the unit cell volume of the NASICON-type structure. Finally, the electrochemical stability window of the NASICON-structured glass-ceramics of highest ionic conductivity is investigated. Cyclic voltammetry measurements are followed by in situ electrochemical impedance spectroscopy, enabling the effect of oxidation and reduction reactions on the electrical properties of the glass-ceramics in question to be determined. X-ray photoelectron spectroscopy, in turn, is applied to determine which chemical species undergo reduction/oxidation. Our findings reveal that the electrochemical stability of this material is limited by the reduction of Ti+4 cations in low potentials and by the oxidation of O-2 anions in high potentials. At high potentials, similar behavior is also encountered for other well-known NASICON-like Li-ion conducting suggesting that the electrochemical behavior in oxidative potentials could be generalized for NASICON-structured phosphates.

No description available.

No description available.

De nouvelles familles de liquides ioniques conducteurs par ion lithium; à anions aromatiques et aliphatiques de type perfluorosulfonate perfluorosulfonylimidure attachés à des oligoéthers (méthoxy polyéthylène glycol mPEG) de longueurs différentes ont été synthétisées et caractérisées dans le but d'améliorer l'interaction entre les chaînes de POE et les sels de lithium en améliorant la mobilité segmentaire. Ainsi différentes membranes amorphes ou peu cristallines améliorent le transport cationique par rapport aux électrolytes polymères usuels. . Leurs propriétés ont été évaluées dans deux types de polymères hôtes : un polyéther linéaire (POE) et un polyéther réticulé préparé par un procédé "VERT". Leurs parties oligooxyéthylène aident à la solvatation des cations lithium et conduisent à l'augmentation des propriétés de transport; c'est à dire la conductivité cationique et le nombre de transport. Leurs stabilités thermiques et électrochimiques sont adaptées à l'application batterie lithium-polymère. / The new families of lithium-conducting ionic liquids; aromatic and aliphatic lithium salts based on perfluorosulfonate and perfluorosulfonylimide anions attached to an oligoether (methoxy polyethylene glycol mPEG) with different lengths were synthesized and characterized with the aim to improve the salt interaction with the host polymer's POE chains while keeping a high segmental mobility. They allowed obtaining membranes with lower crystallization degree and higher cationic transport number as compared with benchmarked salts. Their properties as lithium salts were investigated in two types of host polymers i.e. a linear polyether (POE) and a cross-linked polyether prepared by a ‘GREEN' process. Their oligooxyethylene moieties improve the lithium cation solvation leading to an increase in cationic transference numbers. Their electrochemical and thermal stabilities are suitable for lithium battery application.

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No. of bitstreams: 2 Tese V.6 (Final) - João Fernando.pdf: 9335731 bytes, checksum: d43ee1c77922e89387dfea2707ce3abd (MD5) Carta Comprovante da versão final da tese.jpg: 41274 bytes, checksum: 68e6feb4fa1360327b440f2f90621de9 (MD5) Previous issue date: 2018-03-23 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Many glasses have been studied as solid electrolytes in behalf of replacing commercial liquid electrolytes. However, even for the best glass compositions available in the literature, values of conductivity similar to those presented by liquids are far beyond to be achieved. This work intends to show how changes in the structure, by means of composition, can help to increase the conductivity in oxide glasses. Samples with composition x WO3 - 0.30 (NaPO3)n - (0.70-x) NaF, with 0,30 ≤ ≤ 0,60;, were produced by melting quenching methodology. Substitution of tungsten for sodium fluoride generates a linear decrease of glass transition temperature while the stability remains high enough up to = % and decreasing for higher WO3 content. Raman and 31P and 19F 1D MAS-NMR spectroscopies data shows that the less NaF leads to a depolymerization of main phosphate chains, due to formation of − − bonds. In addition, fluorine atoms prefer to bind in the − form, with low tungsten content, or in − , with high proportion All samples showed same calculated values of Ea for ionic conductivity and drop of σ0. For higher fluoride proportion, it was observed a rise in the conductivity of around one order of magnitude. However, UV-Vis absorption curves demonstrate more presence of W5+ species in samples with ≥ %. This leads to a mixed conductivity of these materials. In order to obtain maximum ionic conductivity, NaF and (NaPO3)n were replaced by Li2O and (LiPO3)n respectively. Samples with composition x WO3 – 0.40 (LiPO3)n – (0.60-x) Li2O, with 0.30 ≤ ≤ 0.50; 0.40 WO3 – y (LiPO3)n – (0.60- y) Li2O, with 0.30 ≤ ≤ 0.50 and z WO3 – (0.80-z) (LiPO3)n – 0.20 Li2O, with 0.30 ≤ ≤ 0.50; were also produced using the melting quenching methodology. The three series of samples presented linear increase of Tg with their respective substitutions, besides having good thermal stability (> 100 °). Raman and 31P 1D MAS-NMR spectroscopies data exhibited the influence of WO3 content on the depolymerization of phosphate chains, as well as the formation of WO6 unit clusters, when much tungsten is present. Although UV-Vis absorption spectra indicate mixed conductivities in some samples, calculated values of ionic conductivity show that the most conductive sample without presence of reduced species reached 6.3 10−4Ω−1−1, comparable to conductive crystalline samples. / Muitos vidros têm sido estudados como eletrólitos sólidos, a fim de substituírem eletrólitos líquidos comerciais. No entanto, mesmo para composições vítreas ótimas na literatura, valores de condutividade similares àqueles presentes pelos líquidos estão muito além do alcançado. Este trabalho pretende mostrar como as mudanças na estrutura, por meio da composição, podem ajudar a aumentar a condutividade em vidros óxidos. Amostras com composição x WO3 – 0,30 (NaPO3)n – (0,70-x) NaF, com 0,30 ≤ ≤ 0,60; foram produzidas por meio da metodologia fusão/resfriamento. Substituição de tungstênio por fluoreto de sódio gera um decréscimo linear da temperatura de transição vítrea, enquanto que a estabilidade permanece alta até = 40 % e decresce para alto teor de WO3. Dados de Espectroscopias Raman e 31P e 19F MAS-NMR mostram que pouco NaF leva a despolimerização das cadeias principais de fosfato, devido a formação de ligações − − . Além disso, átomo de flúor prefere ligar-se na forma − , com baixa proporção de tungstênio, ou em − , com alta proporção. Todas as amostras apresentaram mesmos valores calculados de energia de ativação para condutividade iônica e queda de σ0. Para maior proporção de fluoreto, observou-se um incremento por volta de uma ordem de magnitude. Entretanto, curvas de absorção no UV-Vis demonstrou a maior presença de espécies W5+ em amostras com ≥ 50 % . Isto leva a uma condutividade mista destes materiais. A fim de se obter condutividade iônica máxima, NaF e (NaPO3)n foram substituídos por Li2O e (LiPO3)n respectivamente. Amostras com composições x WO3 – 0,40 (LiPO3)n – (0,60-x) Li2O, com 0,30 ≤ ≤ 0,50; 0,40 WO3 – y (LiPO3)n – (0,60-y) Li2O, com 0,30 ≤ ≤ 0,50 e z WO3 – (0,80-z) (LiPO3)n – 0,20 Li2O, com 0,30 ≤ ≤ 0,50; também foram produzidas por meio da metodologia fusão/resfriamento. As três séries de amostras apresentaram incremento linear de Tg com suas respectivas substituições, além de terem boa estabilidade térmica (> 100 °). Dados de Espectroscopia Raman e 31P MAS-NMR registraram a influência do teor de WO3 na despolimerização das cadeias de fosfato, bem a formação de clusters de unidades de WO6, quando muito tungstênio se faz presente. Apesar de curvas de absorção no UV-Vis indicarem a condutividade mista em algumas amostras, valores calculados de condutividade iônica mostram que a amostra mais condutora e sem a presença de espécies reduzidas, atingiu 6,3 10−4 Ω−1−1, comparável com amostras cristalinas condutoras. / CNPq: 141905/2013-1

Le matériau La_2 Mo_1,5 W_0,5 O_9 (LMW05) est un conducteur ionique de la famille LAMOX qui a récemment connu un grand potentiel en tant qu’électrolyte solide dans des systèmes électrochimiques haute température. L’objectif de cette thèse est double : d’une part, étudier les effets de certains paramètres microstructuraux, essentiellement la porosité, sur les propriétés électriques des échantillons céramiques de LMW05 et, d’autre part, appliquer le procédé de frittage flash pour la préparation d’échantillons denses.Les échantillons poreux ont été préparés par frittage à des températures comprises entre 750 °C et 1100 °C. La spectroscopie d’impédance complexe a été systématiquement utilisée pour évaluer l’influence de la porosité sur les propriétés électriques de LMW05. La réponse électrique, observée à haute fréquence (HF) sur les diagrammes d’impédance, est très affectée par la porosité. Elle dépend de la morphologie et de la localisation des pores. Les théories du milieu effectif ont été employées pour l’interprétation des résultats obtenus. L’approximation de Bruggeman s’est révélée la plus appropriée pour décrire la réponse électrique haute fréquence pour 0 < P ≤ 22%. En comparaison avec des céramiques de type YSZ, les échantillons poreux de LMW05 présentent une faible valeur du facteur de blocage α_R. Cette dernière est, en fait, liée à la morphologie des pores qui sont de forme sphérique et de grande taille. La mise en contact de deux pastilles denses a permis de simuler le contact entre deux grains de LMW05.Le procédé de frittage flash a été testé avec succès pour la préparation des échantillons de LMW05. Une attention particulière a été portée à l’optimisation des conditions de déclenchement du flash de courant. Nous avons montré que les échantillons frittés de LMW05 présentent le même comportement électrique indépendamment du procédé de frittage employé. / The La_2 Mo_1,5 W_0,5 O_9 (LMW05) material is an ionic conductor of the LAMOX family which has recently shown a great potential as a solid electrolyte in high temperature electrochemical systems. The aim of this thesis is double: firstly, to study the effects of certain microstructural parameters, essentially the porosity, on the electrical response of LMW05 ceramic samples and, on the other hand, to apply the flash sintering process for the preparation of dense samples. Porous samples were obtained by varying the sintering temperature in the range of 750 to 1100 °C. Complex impedance spectroscopy was systematically used to evaluate the effect of porosity on the electrical response of LMW05. The electrical response, observed at high frequency (HF) on the impedance diagrams, is greatly affected by the porosity. It depends on the morphology and the location of pores. Effective medium theories were used for the interpretation of obtained results. The Bruggeman approximation proved to be better suited to describe the high frequency electrical response for 0 < P ≤ 22%. Compared with YSZ-type ceramics, the porous LMW05 was found to have a low blocking factor α_R. This low value is related to the morphology of the pores which are spherical in shape and large in size. The contacting of two dense pellets allowed us to simulate the contact between two grains of LMW05.The flash sintering process has been successfully tested for the preparation of LMW05 samples. Particular attention is paid to optimizing the conditions of the flash sintering onset. We have shown that the sintered LMW05 samples exhibit the same electrical behavior independently to the employed sintering process.