Bei der Kristallzüchtung insbesondere von Halbleitern hat die Form des freien Randes (dem Interface zwischen fester und flüssiger Phase) einen starken Einfluss auf die Qualität des Kristalls. Die Dissertation befasst sich mit der Optimalsteuerung der Form und des Verlaufs des freien Randes. Als Vorlage für die in der Arbeit betrachteten Modellkonfigurationen dient das VGF-Verfahren (Vertical Gradient Freeze). Der Erstarrungsprozess wird durch ein Zweiphasen-Stefan-Problem mit durch Konvektion und Lorentzkräfte getriebener Strömung beschrieben. Der freie Rand wird als Graph formuliert. Das Kontrollziel besteht in der Ansteuerung eines gewünschten Verlaufs des freien Randes. Als Kontrollgrößen dient die Temperatur auf der Wand des Schmelztiegels und/oder wandnahe oder verteilte Lorentzkräfte. Das Kontrollziel wird durch Minimierung eines geeigneten Kosten-Funktionals erreicht. Das daraus resultierende Minimierungsproblem wird mit einem Adjungierten-Ansatz gelöst. Anhand numerischer Experimente mit Aluminium und Gallium-Arsenid Schmelzen wird gezeigt, das das vorgestellte Verfahren gut funktioniert.

Für viele Schriftsteller, die schon zu Lebzeiten als Klassiker gelten, werden Denkmale errichtet oder öffentliche Gebäude nach ihnen benannt. Ihre Bücher aber werden zunehmend weniger gelesen. In Chemnitz wurde am 23. November 2010 eine neue Datenbank, die „Stefan-Heym-Sammlung“, für das Internet frei geschaltet. Das Web-Portal, ein Gemeinschaftsprojekt der Stadtbibliothek und der Universitätsbibliothek Chemnitz, soll die Beschäftigung mit Leben und Werk des international renommierten Autors lebendig halten.

Für viele Schriftsteller, die schon zu Lebzeiten als Klassiker gelten, werden Denkmale errichtet oder öffentliche Gebäude nach ihnen benannt. Ihre Bücher aber werden zunehmend weniger gelesen. In Chemnitz wurde am 23. November 2010 eine neue Datenbank, die „Stefan-Heym-Sammlung“, für das Internet frei geschaltet. Das Web-Portal, ein Gemeinschaftsprojekt der Stadtbibliothek und der Universitätsbibliothek Chemnitz, soll die Beschäftigung mit Leben und Werk des international renommierten Autors lebendig halten.

L’objectif de cette thèse est de développer une méthode expérimentale permettant de mesurer simultanément des coefficients de co-diffusion dans les zéolithes, pour des mélanges de paraffines en C6 mono et di-branchées, dont les cinétiques de diffusion sont très différentes. Les espèces sont le 2- et le 3-methyl-pentane (2MP et 3MP) et le 2-2- et le 2-3-dimethyl-butane (22DMB et 23DMB) et l'adsorbant est une silicalite. Cette méthode est basée sur la réponse en sortie d’un lit fixe d’adsorbant à une variation cyclique de la composition à son entrée. La conception d’un modèle faisant intervenir des paramètres cinétiques et thermodynamiques a également être effectuée afin de simuler les courbes de perçages des différents constituants en mélange et sur plusieurs cycles. Les conditions expérimentales sont proches des conditions industrielles, à savoir en phase liquide et à fort taux de remplissage de l’adsorbant (185°C et 35 bars) L’écriture d’un modèle de diffusion, basé sur l’équation de Maxwell-Stefan appliquée au "Dusty Gas Model", dans ces conditions de fonctionnement, implique d’introduire des grandeurs volumiques qui permettent de redéfinir les contraintes liées à la saturation de l'adsorbant. De plus, tout en conservant la simplicité du modèle "Single File Diffusion" (pas de contre-diffusion microporeuse), nous avons montré que la prise en compte d’un flux volumique relatif associé au solide permet de conserver l’indépendance des coefficients de diffusion dans le cristal. Les simulations des courbes de perçage – sur un seul cycle pour les molécules rapides et sur plusieurs cycles pour les molécules lentes – indiquent que les coefficients de diffusion des différents isomères suivent l'ordre suivant : D3MP ˜ D2MP > D23DMB > D22DMB, avec un écart de trois ordres de grandeurs entre le 3MP et le 22DMB, ce qui laisse supposer qu'un procédé de séparation basé sur une sélectivité diffusionnelle peut être envisagé. Cependant, les tests de perçage en condition cyclique permettant de caractériser de manière plus précise le système, il a été possible de mettre en évidence une très lente accumulation du 22DMB au cours des cycles sous certaines conditions opératoires, phénomène qui peut s'avérer indétectable sur un faible nombre de cycles et/ou sur le profils de concentration des autres espèces. Ce phénomène a pour conséquence de diminuer les performances de l'adsorbant, aussi bien d'un point de vue capacitif que d'un point de vue sélectif / The aim of this work is to develop a new experimental method in order to determine simultaneously co-diffusion coefficients in zeolites for mixtures of single- and di-branched C6 paraffins, with totally different diffusion kinetics. The species are 2- and 3-methyl-pentane (2MP and 3MP) and 2-2- and 2-3-dimethyl-butane (22DMB and 23DMB) and the adsorbent is a silicalite. This method is based on the output measurement of an adsorbent column subjected to cyclic variations of its input concentration. The analysis of the mixture experimental breakthrough curves, on several cycles, is carried out using a mathematical model, based on Maxwell-Stefan theory of multi-component diffusion, allowing an estimation of thermodynamic and kinetic parameters. The experimental conditions are close to industrial constraints, i.e. at very high adsorption loading, and in the liquid phase (185°C and 35 bars). This requires to develop a modified Maxwell-Stefan diffusion model, applied to the "Dusty Gas Model", including volume constraints in the crystal which implies to redefine the adsorbent saturation. Moreover, while preserving the simplicity of the "Single File Diffusion" model (no counter-diffusion), a relative volumetric flow of the solid is taken into account, allowing to ensure the independence of the diffusion coefficient of each component in the adsorbent. The Maxwell-Stefan diffusion coefficients for the different isomers, obtained from breakthrough curves simulations – on one cycle for fast diffusing species and several cycles for slow molecules – are in the sequence : D3MP ˜ D2MP, > D23DMB > D22DMB, with a difference of three orders of magnitude between 3MP and 22DMB. This implies that a separation process based on kinetic selectivity can be considered. The cyclic breakthrough experiments, allowing a better characterization of the system, highlight a very slow accumulation of the 22DMB isomer during cycles for specific operating conditions, which may be undetectable on a small number of cycles and on the profiles of the other components.. This phenomenon involves a decrease of the adsorbent performances, in terms of capacity as well as selectivity

Les panneaux photovoltaïques ont pris ces dernières années une place importante dans le secteur de l’énergie. Les performances de ces panneaux dépendent notamment de la qualité et de l’homogénéité du silicium utilisé et des impuretés qu’il contient. Pour obtenir du silicium photovoltaïque, on peut utiliser un procédé de solidification dirigée afin d’obtenir un lingot de silicium de grade photovoltaïque à partir de silicium de grade métallurgique. Cette approche reste aujourd’hui difficile à simuler efficacement en raison de l’aspect multi-échelle du procédé et du suivi de l’interface mobile avec des transferts de masse et de chaleur à l’interface solide/liquide. Cette thèse présente la mise en œuvre d’une méthode originale de maillage glissant proposée pour réaliser un suivi adaptatif de l’interface mobile, afin d’améliorer l’efficacité des simulations. Dans un premier temps, la modélisation de la solidification dirigée d’un corps pur avec un tel maillage glissant est validée à l’aide d’une solution analytique dans une configuration diffusive de référence. L’impact de la méthode proposée est ensuite étudié dans une configuration de type Bridgman vertical en présence de convection naturelle dans la phase liquide. Dans un second temps, on s’intéresse à la ségrégation des impuretés dans cette même configuration. Pour cela, on propose une modélisation spécifique du rejet d’impuretés à l’interface, et on étudie l’impact sur les simulations de la méthode de maillage glissant proposée. Les résultats et les gains de performance pour les simulations sont discutés en faisant varier des paramètres de calcul et par comparaison avec des données de la littérature. / In recent years, photovoltaic panels took a key role in the energy sector. The efficiency of these panels depends notably on the quality of the processed silicon ingots and on their homogeneity regarding the impurities they include. In order to process photovoltaic silicon, one can use a directional solidification process to obtain a solar grade silicon ingot from a metallurgical grade silicon feedstock. This approach is still nowadays hard to simulate with efficiency because of the multi-scales aspects of the process and because of the front tracking of the interface, where some heat and mass transfer occurs. This thesis presents the implementation of an original moving mesh method, proposed in order to perform an adaptive front tracking of the moving interface. The aim is to improve the efficiency of the numerical simulations. In a first time, the directional solidification model of a pure substance with such a moving mesh is validated against an analytical solution based on a purely diffusive reference configuration. The influence of the proposed method is then studied on a vertical Bridgman configuration with natural convection in the liquid phase. In a second time, the segregation of impurities is considered in the same configuration. For this study, a specific model for the rejection of impurities is proposed at the solid/liquid interface, and the influence of the proposed moving mesh method on the results is as well explored. Finally, the results and the performance improvements for the numerical simulations are discussed through variations of the calculation parameters and through comparisons against data from the literature.

Die vorliegende Arbeit befasst sich mit der Verallgemeinerung von Reaktions-Diffusions-Systemen auf Subdiffusion. Die subdiffusive Dynamik auf mesoskopischer Skala wurde mittels Continuous-Time Random Walks mit breiten Wartezeitverteilungen modelliert. Die Reaktion findet auf mikroskopischer Skala, d.h. während der Wartezeiten, statt und unterliegt dem Massenwirkungsgesetz. Die resultierenden Integro-Differentialgleichungen weisen im Integralkern des Transportterms eine Abhängigkeit von der Reaktion auf. Im Falle der Degradation A->0 wurde ein allgemeiner Ausdruck für die Lösungen beliebiger Dirichlet-Randwertprobleme hergeleitet. Die Annahme, dass die Reaktion dem Massenwirkungsgesetz unterliegt, ist eine entscheidende Voraussetzung für die Existenz stationärer Profile unter Subdiffusion. Eine nichtlineare Reaktion stellt die irreversible autokatalytische Reaktion A+B->2A unter Subdiffusion dar. Es wurde ein Analogon zur Fisher-Kolmogorov-Petrovskii-Piscounov-Gleichung (FKPP) aufgestellt und die resultierenden propagierenden Fronten untersucht. Numerische Simulationen legten die Existenz zweier Regimes nahe, die sowohl mittels eines Crossover-Argumentes als auch durch analytische Berechnungen untersucht wurden. Das erste Regime ist charakterisiert durch eine Front, deren Breite und Geschwindigkeit sich mit der Zeit verringert. Das zweite, fluktuationsdominierte Regime liegt nicht im Geltungsbereich der kontinuierlichen Gleichung und weist eine stärkere Abnahme der Frontgeschwindigkeit sowie eine atomar scharf definierte Front auf. Ein anderes Szenario, bei dem eine Spezies A in ein mit immobilen B-Partikeln besetztes Medium hineindiffundiert und gemäß dem Schema A+B->(inert) reagiert, wurde ebenfalls betrachtet. Diese Anordnung wurde näherungsweise als ein Randwertproblem mit einem beweglichen Rand (Stefan-Problem) formuliert. Die analytisch gewonnenen Ergebnisse bzgl. der Position des beweglichen Randes wurden durch numerische Simulationen untermauert. / The present work studies the generalization of reaction-diffusion schemes to subdiffusion. The subdiffusive dynamics was modelled by means of continuous-time random walks on a mesoscopic scale with a heavy-tailed waiting time pdf lacking the first moment. The reaction was assumed to take place on a microscopic scale, i.e. during the waiting times, obeying the mass action law. The resultant equations are of integro-differential form, and the reaction explicitly affects the transport term. The long ranged memory of the subdiffusion kernel is modified by a factor accounting for the reaction of particles during the waiting times. The degradation A->0 was considered and a general expression for the solution to arbitrary Dirichlet Boundary Value Problems was derived. For stationary solutions to exist in reaction-subdiffusion, the assumption of reactions according to classical rate kinetics is essential. As an example for a nonlinear reaction-subdiffusion system, the irreversible autocatalytic reaction A+B->2A under subdiffusion is considered. A subdiffusive analogue of the classical Fisher-Kolmogorov-Petrovskii-Piscounov (FKPP) equation was derived and the resultant propagating fronts were studied. Two different regimes were detected in numerical simulations, and were discussed using both crossover arguments and analytic calculations. The first regime is characterized by a decaying front velocity and width. The fluctuation dominated regime is not within the scope of the continuous description. The velocity of the front decays faster in time than in the continuous regime, and the front is atomically sharp. Another setup where reactants A penetrate a medium initially filled with immobile reactants B and react according to the scheme A+B->(inert) was also considered. This problem was approximately described in terms of a moving boundary problem (Stefan-problem). The theoretical predictions concerning the moving boundary were corroborated by numerical simulations.

O problema da condução de calor, envolvendo mudança de fase, foi resolvido para o caso de uma cavidade limitada por duas superfícies cilíndricas indefinidamente longas. As condições de contorno impostas consistem em manter a temperatura da superfície interna fixa e abaixo da temperatura de fusão do material que preenche a cavidade, enquanto que a temperatura da superfície externa é mantida fixa e acima da temperatura de fusão. Como condição inicial se fixou a temperatura de todo o material que preenche a cavidade no valor da temperatura da superfície externa. A solução obtida consiste em duas soluções da equação de condução de calor, uma escrita para o material solidificado e outra escrita para o material em estado líquido. As duas soluções são formalmente escritas em termos da posição da frente de mudança de fase, que é representada por uma superfície cilíndrica com raio em expansão dentro da cavidade. A posição dessa superfície é, a princípio, desconhecida e é calculada impondo o balanço de energia através da frente da mudança de fase. O balanço de energia é expresso por uma equação diferencial de primeira ordem, cuja solução numérica fornece a posição da frente como função do tempo. A substituição da posição da frente de mudança de fase em um instante particular, nas soluções da equação de condução de calor, fornece a temperatura nas duas fases naquele instante. A solução obtida é ilustrada através de exemplos numéricos. / The heat conduction problem, in the presence of a change of state, was solved for the case of an indefinitely long cylindrical layer cavity. As boundary conditions it is imposed that the internal surface of the cavity is maintained below the fusion temperature of the infilling substance and the external surface is kept above it. The solution, obtained in non-dimensional variables, consists in two closed form heat conduction equation solutions for the solidified and liquid regions, which formally depend of the, at first, unknown position of the phase change front. The energy balance through the phase change front furnishes the equation for time dependence of the front position, which is numerically solved. Substitution of the front position for a particular instant in the heat conduction equation solutions gives the temperature distribution inside the cavity at that moment. The solution is illustrated with numerical examples.

“De konflikt-gestaltade partiledarna” är en kvantitativ innehållsanalys av Aftonbladet, Expressen, Dagens Nyheter och Svenska Dagbladets gestaltning av Stefan Löfven, Ulf Kristersson och Jimmie Åkesson den sista veckan innan riksdagsvalet 2018. Studien fokuserar på förekomsten av konflikt-gestaltning och typ av tonalitet. Syftet med studien är att undersöka hur gestaltningen yttrar sig och vilka likheter och skillnader som finns mellan de tre partiledarna och mellan de fyra tidningarna. De teorier och tidigare forskning studien utgår ifrån är teorierna dagordningsteorin och gestaltningsteorin samt forskning om tabloidisering, partipress, political bias, nyhetsvärdering och nyhetsurval. Dessa teorier och tidigare forskning hjälper studien att förklara och förstå de val tidningarna gör när de gestaltar partiledarna. Vart fjärde år är det riksdagsval i Sverige. 2018 års riksdagsval blev ett utav de jämnaste valen i svensk historia. Tidigare forskning visar att medier har stor makt över vad medborgare anser vara viktigt och vad medborgare har för bild av det politiska samhället. Vilken typ av bild det svenska folket fick av Stefan Löfven, Ulf Kristersson och Jimmie Åkesson i de största svenska tidningarna inför valet är därför viktigt att undersöka. Resultatet av studien visar att det förekommer mycket konflikt-gestaltning och negativ tonalitet i de texter i tidningarna där de tre partiledarna nämns. Kvällstidningarna Aftonbladet och Expressen använder sig av mer negativ tonalitet än vad morgontidningarna Dagens Nyheter och Svenska Dagbladet gör. Tidningarna skiljer sig även åt vad gäller vilken person de fokuserat på den sista veckan innan valet. Stefan Löfven är huvudfokus i Dagens Nyheter och Svenska Dagbladet och Jimmie Åkesson är huvudfokus i Aftonbladet och Expressen. Resultatet mellan de tre partiledarna har inte lika stora skillnader. Det man dock kan konstatera är att Stefan Löfven nämns mer i texter med positiv och balanserad tonalitet än de andra två partiledarna. Jimmie Åkesson nämns något mer i texter med negativ tonalitet. Slutsatserna i studien är att det råder stora skillnader mellan morgon- och kvällstidningarna. Detta speglar den tidigare forskningens slutsatser kring tabloidisering, olika styrfält och partipress. / "The conflict-framed party-leaders" is a quantitative content analysis of Aftonbladet, Expressen, Dagens Nyheter and Svenska Dagbladet's framing of Stefan Löfven, Ulf Kristersson and Jimmie Åkesson the last week before the general election in Sweden 2018. The study focuses on the occurrence of the conflict-frame and type of tonality. The purpose of the study is to investigate how the framing looks and what similarities and differences that exist between the three party-leaders and between the four newspapers. The theories and previous research this study is based on is the framing theory, agenda-setting theory and research about tabloidization, party press, political bias and news selection. These theories and previous research help the study to explain and understand the choices the newspapers make when framing the three party-leaders. Every fourth year there is a general election in Sweden. The 2018 general election became one of the most even elections in Swedish history. Previous research show that media have great power over what citizens consider to be important and what kind of image citizens have of the political society. What kind of image the Swedish people received of Stefan Löfven, Ulf Kristersson and Jimmie Åkesson in the largest newspapers before the election is therefore important to analyze. The results of this study show that the conflict-frame and negative tonality generally occurs a lot in the framing of the three party-leaders. Aftonbladet and Expressen use more negative tonality than Dagens Nyheter and Svenska Dagbladet. The newspapers also differ in terms of which person they focused on the last week before the election. Stefan Löfven is the main focus in Dagens Nyheter and Svenska Dagbladet, and Jimmie Åkesson is the main focus in Aftonbladet and Expressen. The results between the three party-leaders do not have as much differences as the newspapers. What we can note however, is that Stefan Löfven is mentioned more in texts with positive and balanced tonality than the other two party-leaders. Jimmie Åkesson is mentioned a bit more in texts with negative tonality. The conclusions of this study are that there are major differences between the newspapers. This reflects the findings of the previous research on this subject.

O problema da condução de calor, envolvendo mudança de fase, foi resolvido para o caso de uma cavidade limitada por duas superfícies cilíndricas indefinidamente longas. As condições de contorno impostas consistem em manter a temperatura da superfície interna fixa e abaixo da temperatura de fusão do material que preenche a cavidade, enquanto que a temperatura da superfície externa é mantida fixa e acima da temperatura de fusão. Como condição inicial se fixou a temperatura de todo o material que preenche a cavidade no valor da temperatura da superfície externa. A solução obtida consiste em duas soluções da equação de condução de calor, uma escrita para o material solidificado e outra escrita para o material em estado líquido. As duas soluções são formalmente escritas em termos da posição da frente de mudança de fase, que é representada por uma superfície cilíndrica com raio em expansão dentro da cavidade. A posição dessa superfície é, a princípio, desconhecida e é calculada impondo o balanço de energia através da frente da mudança de fase. O balanço de energia é expresso por uma equação diferencial de primeira ordem, cuja solução numérica fornece a posição da frente como função do tempo. A substituição da posição da frente de mudança de fase em um instante particular, nas soluções da equação de condução de calor, fornece a temperatura nas duas fases naquele instante. A solução obtida é ilustrada através de exemplos numéricos. / The heat conduction problem, in the presence of a change of state, was solved for the case of an indefinitely long cylindrical layer cavity. As boundary conditions it is imposed that the internal surface of the cavity is maintained below the fusion temperature of the infilling substance and the external surface is kept above it. The solution, obtained in non-dimensional variables, consists in two closed form heat conduction equation solutions for the solidified and liquid regions, which formally depend of the, at first, unknown position of the phase change front. The energy balance through the phase change front furnishes the equation for time dependence of the front position, which is numerically solved. Substitution of the front position for a particular instant in the heat conduction equation solutions gives the temperature distribution inside the cavity at that moment. The solution is illustrated with numerical examples.

Οι ζεόλιθοι είναι κρυσταλλικά αργιλοπυριτικά υλικά με πόρους μοριακών διαστάσεων και για το λόγο αυτό συχνά καλούνται και ως μοριακά κόσκινα. Χαρακτηρίζονται από την ικανότητα ρόφησης αερίων και ατμών, ανταλλαγής των κατιόντων της δομής τους, καθώς και κατάλυσης σημαντικού αριθμού χημικών αντιδράσεων. Λόγω των ιδιαίτερων φυσικοχημικών ιδιοτήτων τους, οι ζεόλιθοι αποτελούν ιδανικά υλικά για το διαχωρισμό μορίων με διαφορετικό σχήμα, μέγεθος ή πολικότητα γι’αυτό την τελευταία δεκαετία μέρος του ερευνητικού ενδιαφέροντος έχει επικεντρωθεί στην ανάπτυξη πολυκρυσταλλικών μεμβρανών από ζεόλιθους με σκοπό το διαχωρισμό αερίων και υγρών μιγμάτων. Στην παρούσα Διατριβή μελετήθηκε η κρυστάλλωση μεμβρανών φωγιασίτη πάνω σε πορώδη υποστρώματα από α-Al2O3 με επίπεδη και κυλινδρική γεωμετρία συναρτήσει διαφόρων παραμέτρων σύνθεσης όπως ήταν η σύσταση, η θερμοκρασία, ο χρόνος και η γήρανση των αιωρημάτων σύνθεσης των μεμβρανών Συνολικά εξετάστηκαν πέντε διαφορετικές συστάσεις. Η σύσταση 4.17Na2O : 1.0Al2O3 : 10TEA (τριαιθανολαμίνη) : 1.87SiO2 : 460H2O οδήγησε στην ανάπτυξη μεμβρανών φωγιασίτη με λιγότερες ατέλειες και για αυτό μελετήθηκε περισσότερο. Η ικανότητα των μεμβρανών να διαχωρίζουν μίγματα CO2 / H2, CO2 / N2, CO2 / CH4, CO2 / H2 / N2 / CH4, C3H6 / C3H8, C3H6 / N2, C3H8 / N2 και C3H6 / C3H8 / N2 εξετάστηκε συναρτήσει της θερμοκρασίας, της σύστασης και της πίεσης της τροφοδοσίας καθώς και της παρουσίας ή μη υγρασίας στο ρεύμα της τροφοδοσίας. Τα πειράματα διαπερατότητας απέδειξαν, ότι ευνοείται η εκλεκτική μεταφορά κυρίως του CO2 και του C3H6 μέσα από τις μεμβράνες. Η εκλεκτικότητα μπορεί να αποδοθεί στην ισχυρή αλληλεπίδραση των μορίων αυτών με τα κατιόντα Na+ που περιέχονται στη δομή του φωγιασίτη. Τέλος, μελετήθηκαν οι μηχανισμοί μεταφοράς μάζας των μιγμάτων CO2 / H2 και CO2 / H2 / N2 / CH4 με τη χρήση της θεωρίας Stefan-Maxwell. Επιπρόσθετα εξετάστηκαν διάφορες περιπτώσεις αργού σταδίου (διάχυση και εκρόφηση) καθώς και συνδυασμοί διαφορετικών μηχανισμών διάχυσης (επιφανειακή διάχυση και ενεργοποιημένη διάχυση αερίων). Οι συντελεστές διάχυσης υπολογίστηκαν από το συνδυασμό των πειραματικών δεδομένων ρόφησης και διαπερατότητας των καθαρών συστατικών. Η ανάλυση που πραγματοποιήθηκε οδήγησε στο συμπέρασμα ότι η μεταφορά των μιγμάτων μέσα από τις μεμβράνες μπορεί να προβλεφθεί κυρίως από το μηχανισμό της επιφανειακής διάχυσης. / Zeolites are crystalline aluminosilicate materials. They are frequently called molecular sieves because they have pores of molecular dimensions. They are able to adsorb gases or vapors, to exchange framework cations and to catalyze a large number of chemical reactions. Due to their physicochemical properties they are ideal materials for the discrimination of molecules based on their shape, size or polarity. The last decade part of the research attention has been focused on the synthesis of polycrystalline zeolite membranes for the separation of gas and vapor mixtures. In the present thesis the crystallization of faujasite membranes on porous flat or tubular α-Al2O3 substrates was studied as a function of several synthesis parameters such as composition, temperature, time and aging of sol mixtures. Five different compositions were examined. Membranes synthesized using sols with composition 4.17Na2O : 1.0Al2O3 : 10TEA (triethanolamine) : 1.87SiO2 : 460H2O, had the best separation performance. The ability of the membranes to separate CO2 / H2, CO2 / N2, CO2 / CH4, CO2 / H2 / N2 / CH4, C3H6 / C3H8, C3H6 / N2, C3H8 / N2 and C3H6 / C3H8 / N2 mixtures was examined as a function of temperature, feed mixture composition, total feed pressure and the presence or not of humidity in the feed side. In all cases the membranes were either CO2 or C3H6 selective. The separation ability can be attributed to the strong interaction between those molecules with the Na+ cations of the faujasite framework. The transport of CO2, H2, N2 and CH4 through the membranes was modeled using the Maxwell-Stefan theory. Two different cases of rate limiting step (diffusion and desorption) as well as several combinations of different diffusion mechanisms (surface diffusion and activated gaseous diffusion) were considered. The diffusion coefficients were calculated using the single-component permeation and adsorption data. It has been possible to predict the multicomponent permeation fluxes when surface diffusion was assumed the transport mechanism of all species.