Microbial cell disruption using pressurized gas is a promising approach to improve the lipid extraction yield directly from the wet biomass by eliminating the energy-intensive drying process, which is an integral part of traditional methods. As the process starts with the solubilization of the gas in lipid-rich microbial cells, it is important to understand the solubility of different potential gases in both lipid (triglyceride) and lipid-rich microbial cell culture to design efficient cell disruption processes. In this study, we determined the solubility of different gases (e.g., CO2, CH4, N2, and Ar) in canola oil (triglyceride) using a pressure drop gas apparatus developed in our laboratory. The solubility of different gases in triglyceride followed the trend CO2 > CH4 > Ar > N2. Since the solubility of CO2 was found to be higher compared to other gases, the solubility of CO2 in lipid rich cell culture, cell culture media, and spent media was also determined. It was found that CO2 is more soluble in triglycerides, but less soluble in lipid-rich cell culture compared to CO2 in water. From both thermodynamic models and Monte Carlo simulations, the correlated solubility was found to be in good agreement with the experimental results. CO2 was found to be the most suitable gas for microbial cell disruption because almost 100% cell death occurred when using CO2 whereas more than 85% cells were found to be active after treatment with CH4, N2, and Ar. The optimization of microbial cell disruption was conducted using the combination of Box-Behnken design of experiment (DOE) technique and response surface methodology. The optimized cell disruption conditions were found to be 3900 kPa, 296.5 K, 360 min, and 325 rpm where almost 100% cell death was predicted from the statistical modeling. Finally, it was found that 86% of the total lipid content can be recovered from the wet biomass after treatment with pressurized CO2 under optimized conditions compared to control where up to 74% of the total lipid content can be recovered resulting in 12% increase in the lipid extraction yield using pressurized CO2.

Les données expérimentales sur les propriétés thermodynamiques des mélanges entrant dans la composition des nouvelles générations de carburants sont rares ou entachées d’erreur. L’objectif de cette thèse est de contribuer à l’alimentation de base de données thermophysique de corps purs et de mélanges entrant dans la composition des carburants formés de biodiesel/diesel dans une large gamme de pression et de température (1 Pa à 200 kPa). Grâce à l’appareil statique disponible au laboratoire (UMR 5615) et aux différentes méthodologies mises au point pour la détermination des équilibres de phase, l’acquisition de données fiables a été obtenue pour 8 corps purs et leurs mélanges binaires. Les valeurs relatives aux pressions de vapeur des corps purs sont en bon accord avec la littérature dans le domaine des pressions moyennes. En revanche pour les faibles pressions de vapeur (inférieures à 1 kPa) et pour les mélanges binaires étudiés, les pressions de vapeur obtenues sont originales. Les deux modèles thermodynamiques NRTL et UNIQUAC ont restitué les résultats expérimentaux de façon satisfaisante.L’étude des propriétés volumétriques par la mesure de la densité, nous a permis d’interpréter les différentes interactions qui peuvent exister dans un mélange binaire constitué d’un ester et d’un alcane / Experimental data of thermodynamic properties of mixtures used in the composition of new fuel generations are very rare in the literature.The aim of this thesis is to contribute to setting up a thermophysical database of constituents used in the composition of biodiesel / diesel mixtures over a wide range of pressure and temperature (1 Pa to 200 kPa).Thanks to the static apparatus available in the laboratory (UMR 5615-Lyon1) and to the various methodologies developed to determine phase equilibrium, the acquisition of reliable data has been obtained for 8 pure substances and their binary mixtures. The vapor pressures of the pure compounds are in good agreement with the literature data in the range above 1 kPa whereas no data has been found to compare with experimental values of the pure compounds or mixtures below 1 kPa.A good correlation of the experimental results was obtained using two thermodynamic models, NRTL and UNIQUAC.The study of the volumetric properties obtained by densimetry, led us to interpret the different interactions that could exist in a binary mixture consisting of ester and alkane and to estimate quantitatively the different contributions to the excess molar volume

Ce travail porte sur l'étude de la capacité d'absorption du CO2 par différents types d'amines dissoutes en milieux aqueux et non aqueux. Ce dernier est constitué d'un mélange de chlorure de choline et d'éthylène glycol dans une proportion molaire respectivement de 1 pour 2. Ce solvant, communément appelé "Ethaline", appartient à la catégorie dite des « Solvants à Eutectique Profond » ainsi désignés car leur composition eutectique permet d'obtenir des mélanges généralement liquides à température ambiante. Pour ce faire un appareil d'équilibre liquide-vapeur avec analyse en ligne de la phase vapeur par GC a été réalisé et son fonctionnement validé. Les isothermes d'absorption du CO2 ainsi que la volatilité (composition de la phase vapeur) des mélanges étudiés, avec et sans CO2, ont été déterminées à différentes températures et pour différentes compositions en amines. Le domaine de pression exploré est particulièrement large : du Pascal à 800 kPa. L'étude a montré que la substitution de l'eau par "l'Ethaline" conduit à une capacité d'absorption du CO2 presque identique à celle de la MEA et DEA en solution aqueuse. Par contre dans le cas de la MDEA on observe une capacité d'absorption plus faible en milieu « Ethaline » qu'en milieu aqueux. Les isothermes d'absorption du CO2 des trois classes d'amines en milieu aqueux et non aqueux ont été corrélés par les modèles semi empiriques de (Gabrielsen et al., 2005) initialement établis par ces auteurs pour les solutions aqueuses (un modèle pour les amines primaires et secondaires conduisant à la formation de carbamates en présence de CO2, un modèle pour les amines tertiaires donnant des sels d'ammonium avec le CO2). Nous avons montré que ces deux modèles représentent avec succès les isothermes d'absorption en milieu non aqueux. Les constantes d'équilibre et les enthalpies de réaction qui s'en déduisent montrent que ces dernières sont plus faibles (en valeur absolue) pour la MEA et TMDEA en solution éthaline qu'en solution aqueuse. Dans le cas de la MDEA la nature du solvant n'a qu'une influence minime sur l'enthalpie de réaction. Les valeurs expérimentales des volatilités des amines dans les différents mélanges Amine- CO2 en milieu aqueux ont été corrélées par différents modèles semi-empiriques. Trois modèles thermodynamiques de coefficients d'activité ; le modèle de Wilson, NRTL et UNIQUAC ont été utilisés afin de restituer les données expérimentales de l'équilibre liquide-vapeur des systèmes aqueux d'amines (sans CO2). Une représentation satisfaisante des résultats expérimentaux par les trois modèles a été obtenue / This work focuses on the study of the absorption capacity of CO2 by different types of dissolved amines in aqueous and non-aqueous media. The latter consists of a mixture of choline chloride and ethylene glycol in a molar proportion of 1 to 2 respectively. This solvent, commonly called "Ethaline", belongs to the category called "Deep Eutectic Solvents" so designated because their eutectic composition makes it possible to obtain mixtures that are generally liquid at room temperature. With this aim, a liquid-vapor equilibrium apparatus with on-line analysis of the vapor phase by GC was performed and its operation validated. The CO2 absorption isotherms and the volatility (composition of the vapor phase) of the studied mixtures, with and without CO2, were determined at different temperatures and for different amine compositions. The explored pressure range is particularly large: from 1 Pa to 800 kPa. The study showed that the substitution of water by "Ethaline" leads to a CO2 absorption capacity almost identical to that of MEA and DEA in aqueous solution. On the other hand, in the case of MDEA, a lower absorption capacity is observed in Ethaline than in aqueous medium. In the hypothesis of a use of the DES+amine solvent for CO2 capture in post-combustion process, a decrease of the vapor pressure of the solvent (comparing to that of water+amine) has an advantage because of the low solvent loss due to vaporization in the absorber. The second advantage is most likely a lower effect of equipment corrosion, the third positive point is a lower enthalpy of absorption of MEA and MDEA in (1 ChCl : 2 EG) comparing to aqueous medium, resulting in a possible saving of energy in the regenerator of almost 40%. The disadvantage of the use of amines in "Ethaline" solution is the high viscosity of this solvent which decreases the kinetics of material transfer and reaction with CO2. The CO2 absorption isotherms and the experimental values of the amine volatilities in the different Amine-H2O-CO2 mixtures were well correlated by different semi-empirical models. Three thermodynamic models based on the activity coefficients; the Wilson model, NRTL and UNIQUAC were used to restitute experimental data for the liquid-vapor equilibrium of aqueous amine systems (without CO2). A satisfactory representation of the experimental results by the three models was obtained

Les performances des modèles thermodynamiques actuels pour les solvants mixtes (en particulier avec alcools) électrolytiques sont limités. L’objectif de ce travail est d’étendre les capacités du modèle eGC-PPC-SAFT à ces systèmes. Ceci est fait en plusieurs étapes. Dans une première étape, le modèle PPC-SAFT existant est amélioré pour l’eau pure et les solvants usuels, par (1) introduisant une dépendance en température du diamètre sphère dure de l'eau et (2) adapter un minimum de paramètres ioniques sur les coefficients d’activité moyens et les densités des systèmes contenant des électrolytes forts ainsi que les sur les équilibres liquide vapeur des solvants mixtes d'électrolytes. Dans une troisième étape, le modèle final est utilisé pour représenter les équilibres liquide-liquide des solvants mixtes électrolytiques en étudiant les coefficients de partition de chacune des espèces dans le système. Pour cela, une stratégie de paramétrage des paramètres binaires ion-solvant a été développée, qui implique l’évaluation de l’impact de chacune des contributions individuelles du modèle ePPC-SAFT sur les coefficients de partition. Étant donné son importance dans le cadre de la modélisation thermodynamique de ces systèmes, une nouvelle règle de mélange pour le constant diélectrique est proposée. Au final, le modèle développé est capable de décrire les coefficients d’activité ainsi que les équilibres VLE et LLE des système électrolytiques avec solvants mixtes. / The capabilities of the current thermodynamic models are limited in dealing with mixed-solvent electrolyte systems, due to the complex interactions within these systems. The objective of this work is to extend eGC-PPC-SAFT model to these systems. This is done in several steps. First, a modification in the temperature dependent water diameter was proposed. Second, a minimum number of ion-water parameters are determined on mean ioninc activity coefficients and densities of strong electrolyte systems, as well as vapour-liquid equilibria (VLE) of mixed solvent electrolytes. In the third step, the model is used to study the liquid-liquid equilibrium (LLE) of the mixed-solvent electrolyte system. This was done by looking at the partition coefficients of the individual species in the systems. In doing so, a parameterization strategy was developed for ion-solvent binaries that involve assessing the impact of the individual ePPC-SAFT contribution on the partitioning of individual species. A new method for dealing with the condition of electroneutrality in liquid-liquid ionic systems was proposed that involves a direct correction on the fugacity coefficient. In view of the importance of this property, a new mixing rule for the dielectric constant of mixed solvent is proposed to provide the best description of LLE of mixed solvent electrolyte. The final model is capable of describing, the activity coefficient, VLE, and LLE of mixed-solvent electrolyte systems.

xiv, 103 p. : ill. (some col.) / Results from a recent mid-ocean ridge tomography study along the fast-spreading, northern East Pacific Rise (EPR) reveal that the axis of mantle upwelling beneath the ridge is skewed with respect to the spreading axis, giving rise to regions of both rise-centered and off-axis mantle melt accumulation. Here, we investigate the effects of off-axis melt accumulation on the architecture of overlying crust as well as off-axis melt delivery on crustal construction along the ridge axis. We first present evidence for off-axis magmatism 20 km from the spreading center in 300-ka-old crust overlying a region of off-axis melt supply. Seismic data reveal an intrusive complex ∼2 km beneath the seafloor that is limited in lateral extent (<5 km) and comprises a melt lens underlain by low-velocity, high-attenuation crust, which provides the necessary conditions to drive off-axis volcanic and hydrothermal activity. We next present results from thermodynamic modeling that show systematic, along-axis variations in the depth of crystallization and degree of differentiation of magma produce crustal density variations of ∼0.1 g/cm 3 . These density anomalies are on the order inferred from a recent study that shows increasing axial depth along the northern EPR correlates with an increase in crustal density and offset of mantle upwelling with respect to the ridge axis. Our results, along with geophysical and geochemical data from the 9°-10°N region of the EPR, suggest that along-axis deeps correspond with magmatic systems that have significant near-Moho (i.e., crust-mantle transition) crystallization, which we attribute to off-axis delivery of mantle melt. As this investigation is motivated by the EPR tomography results, we conclude with a numerical study that examines the travel time sensitivity of Pn , a sub-crustal head wave commonly used in local travel time tomography, to crustal and mantle heterogeneity. Our results indicate that Pn travel times and Fresnel zones are insensitive to normal sub-axial crustal thickness anomalies, mantle velocity gradients and crust-mantle velocity contrast variations and that mantle low-velocity zones must be at least 3 km thick to produce significant, near-constant Pn delay times. Our data support the validity and interpretation of the EPR tomography results. This dissertation includes both previously published and unpublished co-authored material. / Committee in charge: Dr. Douglas R. Toomey, Chairperson; Dr. Paul J. Wallace, Member; Dr. Eugene Humphreys, Member; Dr. James Isenberg, Outside Member

Submitted by Luciano Guimarães Alves (luciano_kouros@hotmail.com) on 2018-10-05T00:31:18Z No. of bitstreams: 1 Tese - Luciano Guimarães Alves - 02-10-18_Versão Final.pdf: 3679805 bytes, checksum: a7d506e1df21202b74acc947a1ce92bb (MD5) / Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2018-10-05T18:42:41Z (GMT) No. of bitstreams: 1 alves_lg_dr_guara.pdf: 3679805 bytes, checksum: a7d506e1df21202b74acc947a1ce92bb (MD5) / Made available in DSpace on 2018-10-05T18:42:42Z (GMT). No. of bitstreams: 1 alves_lg_dr_guara.pdf: 3679805 bytes, checksum: a7d506e1df21202b74acc947a1ce92bb (MD5) Previous issue date: 2018-08-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As indústrias queimam combustíveis para produzir energia térmica para um processo. Em alguns casos, uma fração dessa energia não é completamente utilizada. Com o intuito melhorar a eficiência do sistema, essa fração de energia térmica não utilizada pode ser usada para acionar um Sistema de Refrigeração por Absorção (SRA). Nas últimas décadas, o interesse em usar SRA aumentou consideravelmente por conta da possibilidade de se utilizar vapor, água quente e gases de exaustão de sistemas de potência. Além disso, melhorias tecnológicas permitiram uma melhor eficiência do SRA. Uma modelagem termodinâmica do SRA foi realizada para analisar o desempenho de uma máquina em termos energéticos e exergéticos para obter água gelada a 5, 7, 9, 11 e 15 oC com uma fonte de água quente a 80, 90, 100, 110, 120 e 130 oC . A primeira e segunda lei da termodinâmica, tabelas e equações das propriedades da solução aquosa de brometo de lítio e água foram utilizadas para modelar o ciclo e efetuar os cálculos. As hipóteses básicas consideradas foram regime permanente, água pura, bomba isentrópica e processos adiabáticos. Através da análise dos resultados, que essa metodologia pode ser aplicada para determinar o comportamento da variação do COP e eficiência exergética em função da temperatura da água quente que alimenta o gerador e da água gelada obtida no evaporador. Realizou-se análise energética e exergética em cada componente do sistema. Com base nesses dados, pode-se verificar que a faixa de temperatura de água quente que o SRA deve ser alimentado de modo a operar na maior eficiência energética e exergética é de 90 a 100 oC. Ao analisar a distribuição exergética nos componentes, nota-se que as maiores perdas de exergia estão no gerador e absorvedor. / Industries burn fuels to produce thermal energy for a process. In some cases, a fraction of this energy is not fully utilized. In order to improve the efficiency of the system, this waste of energy can be used to drive an Absorption Refrigeration System (ARS). On the last decades, the interest in using ARS increased considerably because of the possibility of using steam, hot water or exhaust gases from thermal engines. Furthermore, technological improvements increased efficiency of this cycle. A thermodynamic model of an ARS was developed to calculate the required energy to generate cold water at 5, 7, 9, 11 e 15 oC from a heat source at 80, 90, 100, 110, 120, 130 oC. First law of thermodynamic, tables and equations of property of aqueous solution of lithium bromide and water were used to model the cycle. The basic hypothesis considered was steady state, pure water, isentropic pump and adiabatic processes. Analysis of the results revealed that this methodology can be applied to study the relationship between COP and exergetic efficiency as a function of the inlet hot water temperature and outlet cold water . Energetic and exergetic analysis were performed for each component. The results show that the highest COP and exergetic efficiency were obtained for hotwater temperature range between 90 to 100 oC. The distribution in terms of exergy in main components were studied and revealed that the high losses of exergy occurred in evaporator and absorber / 1586376

Made available in DSpace on 2014-12-17T15:01:24Z (GMT). No. of bitstreams: 1 DivalBGN_DISSERT.pdf: 2637921 bytes, checksum: 83fbea74e9888e52417cea5286defdaa (MD5) Previous issue date: 2010-12-22 / Crude oil is a complex liquid mixture of organic and inorganic compounds that are dominated by hydrocarbons. It is a mixture of alkanes from the simplest to more complex aromatic compounds that are present derivatives such as gasoline, diesel, alcohol, kerosene, naphtha, etc.. These derivatives are extracted from any oil, however, only with a very high quality, in other words, when the content of hydrocarbons of low molecular weight is high means that production of these compounds is feasible. The American Petroleum Institute (API) developed a classification system for the various types of oil. In Brazil, the quality of most of the oil taken from wells is very low, so it is necessary to generate new technology to develop best practices for refining in order to produce petroleum products of higher commercial value. Therefore, it is necessary to study the thermodynamic equilibrium properties of its derivative compounds of interest. This dissertation aims to determine vapor-liquid equilibrium (VLE) data for the systems Phenilcyclohexane - CO2, and Cyclohexane - Phenilcyclohexane - CO2 at high pressure and temperatures between 30 to 70oC. Furthermore, comparisons between measured VLE experimental data from this work and from the literature in relation to the Peng- Robinson molecular thermodynamic model, using a simulation program SPECS IVCSEP v5.60 and two adjustable interaction parameters, have been performed for modeling and simulation purposes. Finally, the developed apparatus for determination of phase equilibrium data at high pressures is presented / O petr?leo bruto ? uma complexa mistura l?quida de compostos org?nicos e inorg?nicos em que predominam os hidrocarbonetos, desde os alcanos mais simples at? os arom?ticos mais complexos. Nessa mistura encontram-se presentes derivados como gasolina, diesel, ?lcool, querosene, nafta, g?soleos, etc., estes derivados s?o extra?dos de qualquer petr?leo, por?m, somente os com uma qualidade bastante elevada, ou seja, com teor de hidrocarbonetos de baixo peso molecular alto s?o realmente vi?veis a produ??o destes compostos. A American Petroleum Institute (API) desenvolveu um sistema de classifica??o dos tipos de petr?leo. No Brasil a qualidade da maioria dos petr?leos retirado dos po?os ? muito baixa, sendo assim, ? necess?rio obter novos conhecimentos a fim de desenvolver melhores pr?ticas de refino com o intuito de produzir derivados de petr?leo de alto valor comercial. Para isso se faz necess?rio o estudo de equil?brio termodin?mico de seus derivados. Esta disserta??o de mestrado consiste em determinar dados de equil?brio l?quido-vapor dos sistemas Fenilciclohexano - CO2 e Fenilciclohexano - Ciclohexano e CO2 a alta press?o e temperaturas entre 30 a 70 graus Celsius. Compara??es entres os dados experimentais de equil?brio liquidovapor encontrados no laborat?rio e na literatura foram realizadas em rela??o aos valores obtidos pelo modelo termodin?mico molecular de Peng-Robinson usando o programa computacional SPECS IVCSEP v5.60, com dois par?metros de intera??o ajust?veis, para fins de modelagem e simula??o. Al?m disso, ? apresentado o desenvolvimento de um equipamento de alta press?o no laborat?rio para determina??o de dados de equil?brio de fases

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Aromatic hydrocarbons are chemical compounds of great interest in the petrochemical industry. These are commonly derived from reformed naphtha, which are in multicomponent mixtures with aliphatic hydrocarbons. The separation of these components is realized, generally, the liquid-liquid extraction process. In this process, the sulfolane is the most widely used solvent. However, this has some disadvantages such as high cost. For this reason, many studies are developed by the academic community in order to propose alternative solvents to replace the exclusive use of sulfolane by compounds that are important features like good selectivity, easy recoverability and low costs. Given the above, this study main aims to determine liquid-liquid equilibrium data (LLE) to study the ability of solvents [diethylene glycol (DEG), triethylene glycol (TEG), glycerol and 2-hydroxyethyl amine format (2-HEAF)] in extracting aromatic mixtures with aliphatic. The physical properties also of great importance in the understanding of the behavior and interactions that occur in liquid mixtures. Thus, in this study were also studied the density and viscosity of solvent extractors aromatic. The experimental methodology for the determination of LLE data was initially validated by reproducing the literature, and the results showed good agreement between these data. After the method has been validated, solubility curves and tie-lines were constructed for systems containing decane + toluene + DEG (+ TEG, + glycerol, + 2-HEAF, + sulfolane) at T = (303.15 and 333.15) K. The composition data of tie-lines, obtained experimentally, were used to calculate the selectivity parameter and the distribution coefficient. With this data, it can be concluded that all the solvents studied have a good capacity for toluene extraction from mixtures with decane. However, the glycerol has presented as the most promising solvent for aromatics extraction. Finally, the experimental data were correlated through the thermodynamic activity coefficient models, NRTL and UNIQUAC. The results were considered satisfactory, noting that the NRTL was the model that presented minor deviations in compositions. Thus, best represented the LLE data for the systems studied. / Os hidrocarbonetos aromÃticos sÃo compostos quÃmicos de grande interesse na indÃstria petroquÃmica. Estes sÃo comumente originados da nafta reformada, onde encontram-se em misturas multicomponentes com hidrocarbonetos alifÃticos. A separaÃÃo destes componentes à realizada, em sua grande maioria, pelo processo de extraÃÃo lÃquido-lÃquido. Nesse processo, o sulfolano à o solvente mais utilizado. No entanto, este apresenta algumas desvantagens, tais como alto custo. Por esse motivo, inÃmeros estudos sÃo realizados pela comunidade acadÃmica a fim de propor solventes alternativos que substituam o uso exclusivo do sulfolano por compostos que tambÃm apresentem caracterÃsticas importantes, como boa seletividade, boa recuperabilidade e baixos custos. Diante do exposto, o presente trabalho tem como principal objetivo determinar dados de equilÃbrio lÃquido-lÃquido (ELL) para estudar a capacidade dos solventes [dietilenoglicol (DEG), trietilenoglicol (TEG), glicerina e 2-hidroxietilamina formato (2-HEAF)] em extrair aromÃticos das misturas com alifÃticos. As propriedades fÃsicas tambÃm assumem extrema importÃncia no conhecimento do comportamento e das interaÃÃes que ocorrem nas misturas de lÃquidos. Deste modo, neste trabalho foram estudados a densidade e a viscosidade de solventes extratores de aromÃticos. A metodologia experimental para obtenÃÃo dos dados de ELL foi inicialmente validada reproduzindo dados da literatura, e os resultados mostraram uma boa concordÃncia entre estes dados. ApÃs a metodologia ter sido validada foram construÃdas curvas de solubilidade e tie-lines para os sistemas contendo decano + tolueno + DEG (+ TEG, + glicerina, + 2-HEAF, + sulfolano) a T = (303,15 e 333,15) K. Os dados de composiÃÃo das tie-lines, obtidos experimentalmente, foram utilizados para calcular o parÃmetro de seletividade e o coeficiente de distribuiÃÃo. De posse desses dados, pode-se concluir que todos os solventes estudados apresentam boa capacidade para extraÃÃo de tolueno a partir de misturas com decano. No entanto, a glicerina destacou-se como o solvente mais promissor para a extraÃÃo de aromÃticos apresentando os maiores valores para seletividade. Finalmente, os dados experimentais foram correlacionados atravÃs dos modelos termodinÃmicos de coeficiente de atividade, NRTL e UNIQUAC. Os resultados foram considerados satisfatÃrios, observando-se que o NRTL foi o modelo que apresentou os menores desvios na composiÃÃo. Dessa forma, representou melhor os dados de ELL para os sistemas estudados.

Orientador: Adalberto Bono Maurizio Sacchi Bassi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-25T02:48:09Z (GMT). No. of bitstreams: 1 Reis_MartinaCosta_D.pdf: 1200753 bytes, checksum: 9318dbbd02e3d4660c4a6806e68dad7d (MD5) Previous issue date: 2014 / Resumo: Este trabalho descreve a termodinâmica de sistemas eletroquímicos. Explorando os princípios da teoria constitutiva, algumas hipóteses ad hoc e, em especial, o princípio de entropia Müller-Liu, modelos termo-eletroquímicos são propostos para soluções eletrolíticas e para as regiões de bulk e dupla camada de um sistema eletroquímico. A influência das interações íon-íon e íon-solvente sobre a dinâmica da mistura é considerada através da termodinâmica de contínuos polares e as equações de balanço são apropriadamente postuladas. Além disso, equações fenomenológicas são apresentadas para uma solução eletrolítica diluída e isotrópica e as condições para o equilíbrio termodinâmico local do bulk e da dupla camada são investigadas. Comparando-se as desigualdades residuais de entropia obtidas para cada região, foi demonstrado que alguns processos, tais como os fenômenos de difusão térmica, termoeletricidade e eletroforese, desenvolvem-se somente na dupla camada. Consequentemente, o estado de equilíbrio termodinâmico local na dupla camada requer condições termodinâmicas mais severas do que no bulk. Apesar das equações constitutivas serem as mais simples possíveis, os modelos constitutivos propostos para as regiões de dupla camada e bulk são fisicamente consistentes e mais abrangentes do que os modelos eletroquímicos usuais, visto que as equações e relações termodinâmicas obtidas não se limitam às condições limites e nem de equilíbrio. Portanto, a descrição termodinâmica mostrada neste trabalho pode estimular químicos e engenheiros químicos a usar a abordagem contínua no estudo da mobilidade iônica em meios bio e geológicos, fluxos de íons e de outras espécies químicas através de membranas e processos cujas transferências de calor e massa são intensificadas por campos eletromagnéticos / Abstract: This work concerns the thermodynamics of electrochemical systems. Exploiting the principles of constitutive theory, few expedient assumptions, and, in special, the Müller-Liu entropy principle, a thermo-electrochemical continuum model is proposed for electrolyte solutions as well as for the bulk and double layer regions of an electrochemical system. The influence of ion-ion and ion-solvent interactions on the mixture dynamics is taken into account through the thermodynamics of polar materials and balance laws for an electrochemical system are accordingly stated. In addition, phenomenological equations are schemed for a dilute and isotropic electrolyte solution, and the conditions for local thermodynamic equilibrium of bulk and double layer regions are investigated. Comparing the residual entropy inequalities obtained for each region of an electrochemical system, it is shown that some mechanisms develop only in the double layer, such as the thermal diffusion, thermoelectricity and electrophoresis phenomena. As a consequence, the local thermodynamic equilibrium state in the double layer requires stricter conditions than in the bulk. Although the constitutive equations are the simplest possible, the constitutive models proposed for the double layer and bulk regions are physically consistent and more comprehensive than the usual models since the emerging equations do not constrain themselves to equilibrium neither limiting conditions. Therefore, the thermodynamic description provided in this work may stimulate chemists and chemical engineers to take advantage of it to study the flow of ions and other chemical species across cell membranes, ionic mobility in bio and geological media, and processes whose heat and mass transfers are enhanced by electromagnetic fields / Doutorado / Físico-Química / Doutora em Ciências

Les diagrammes d’équilibre sont le point de départ et la ligne directrice qui permet de prévoir et contrôler les phases pouvant se former au cours de différents processus industriels. Bien que l’étude expérimentale soit nécessaire pour les systèmes binaires et ternaires, elle est difficilement envisageable pour déterminer les diagrammes de phases des systèmes d’ordre supérieur sur de larges gammes de composition et de température. Afin de contourner ce problème, la méthode dite CALPHAD (CALculation of PHAse Diagram) a été développée. Son principe consiste à optimiser les paramètres des modèles thermodynamiques utilisés pour décrire l´énergie libre de Gibbs de chaque phase à partir d’informations expérimentales ou estimées (ab-initio). Le modèle appelé « Compound Energy Formalism » (CEF) est largement utilisé pour décrire les phases qui présentent plusieurs sous-réseaux. Ce modèle et ceux qui en dérivent permettent la modélisation d'une grande variété de composés. Les activités menées au cours de ce travail ont permis de développer une nouvelle approche du CEF (NACEF) basée sur une étude mathématique de ses paramètres thermodynamiques. Elle a conduit à une nouvelle formulation de la fonction d'énergie libre de Gibbs faisant intervenir de nouveaux paramètres indépendants. Cette nouvelle approche a été utilisée dans le cadre de ce travail afin de modéliser les phases intermétalliques binaires constituée de deux sous-réseaux présentant des défauts uniquement de type anti-sites (A,B)a(A,B)b. Le système Al-Fe-Nb sur lequel porte notre étude a été choisi en raison de son importance dans la fabrication de nombreuses familles d'alliages tels que les aciers, les alliages légers et plus récemment dans le développement de nouveaux matériaux réfractaires à base Nb pour des applications à hautes températures. Dans ce travail, de nouvelles modélisations des bordures binaires Al-Nb et Fe-Nb et pour la première fois du ternaire Al-Fe-Nb sont proposées en utilisant la NACEF et en s’appuyant sur les informations issues de la littérature ou obtenues dans cette étude. / The equilibrium diagrams are the starting point and the guideline to predict and control the microstructure that will form during processing materials. Despite experiments being necessary in binaries and ternaries systems, it is difficult to experimentally determine phase diagrams of higher orders systems over wide ranges of compositions and temperature. The CALPHAD (CALculation of PHAse Diagrams) method was developed in order to solve this problem. The essence is to optimize the parameters of thermodynamic models that describe the Gibbs free energies of each phase aiming to reproduce the experimental and estimated (ab-initio) data. The compound energy formalism (CEF) is widely used in order to describe phases which present several sublattices. It allows the modeling of a large variety of phases and numerous methods have been developed to treat different situations. The activities in this work developed a new approach of the CEF (NACEF) based on a mathematic analysis of the parameters which leads to a new formulation of the Gibbs free energy function evolving new independent parameters in which new independent parameters are obtained to express the Gibbs free energy. This approach was used in this work to describe the intermetallic phases with two-sublattice in which the only defect type is anti-sites (A,B)a(A,B)b. The Al-Fe-Nb system was chosen due to its importance for the manufacturing process of several families of alloys currently used, e.g. steels, light alloys, and also for the development of new materials for high temperatures application. The binaries Al-Nb and Fe-Nb were reassessed and the Al-Fe-Nb system was assessed for the first time using literature information and new experimental data. / Os diagramas de equilíbrio são o ponto de partida e a diretriz para prever e controlar a microestrutura ao final do processamento de um material. Apesar de experimentos serem necessários em sistemas binários e ternários, é muito difícil determinar experimentalmente diagramas de fase de sistemas de ordens superiores numa vasta amplitude de composições e temperatura. A fim de solucionar este problema, o método CALPHAD (CALculation of PHAse Diagrams) foi desenvolvido. A essência consiste em aperfeiçoar os parâmetros de modelos termodinâmicos que descrevem as energias livres de Gibbs de cada fase de modo a reproduzir as informações experimentais ou estimadas (ab-initio). O compound energy formalism (CEF) é amplamente utilizado para descrever fases que apresentam várias sub-redes. Ele permite a modelagem de uma grande variedade de fases e vários métodos têm sido desenvolvidos para o tratamento de diferentes situações. As atividades deste trabalho ajudaram a desenvolver uma nova abordagem para o CEF (NACEF) com base em um estudo matemático dos seus parâmetros termodinâmicos que levou a uma nova formulação para função da energia livre de Gibbs envolvendo novos parâmetros independentes. Esta nova abordagem tem sido utilizado como parte do presente trabalho para modelar fases intermetálicas binárias constituídas de sub-redes cujo único defeito é do tipo anti-sítio (A,B)a(A,B)b. O sistema Al-Fe-Nb foi escolhido devido a sua importância para o processo de fabricação de diversas famílias de ligas usadas atualmente, e.g. aços, ligas leves e, além disto, é um sistema importante para o desenvolvimento de materiais para aplicações em altas temperaturas. Neste trabalho os binários Al-Nb e Fe-Nb foram reavaliados e o sistema Al-Fe-Nb foi modelado pela primeira vez utilizando as informações da literatura e novos dados experimentais.