La Réduction Catalytique Sélective (SCR) par l'ammoniac, ou l'urée, est un procédé connu de post-traitement permettant de réduire efficacement les oxydes d'azote émis par les motorisations Diesel, en azote et en eau. Les zéolithes échangées au cuivre sont parmi les meilleures formulations pour une application sur véhicules légers, puisque efficaces sur une large zone de température. Le but de cette thèse était d'étudier la stabilité hydrothermale de ce type de catalyseur. L'approche utilisée au cours de ce travail repose sur l'étude des différentes fonctionnalités d'un catalyseur commercial de NH3-SCR présent sous forme de monolithe, à l'état frais et pour différentes conditions de vieillissement, au Banc Gaz Synthétique couplée à une analyse physico-chimique précise de la phase active du catalyseur. Ceci nous a permis de comprendre les phénomènes de désactivation intervenant au cours d'un vieillissement hydrothermal et de mesurer leur impact sur l'activité et la sélectivité de ce type de catalyseur. Après traitement hydrothermal, on assiste à une désalumination plus ou moins importante de la zéolithe, pouvant conduire à l'effondrement de sa structure, ainsi que d'importantes modifications au niveau du cuivre dès les plus faibles températures de vieillissements. Les résultats ont montré l'importance de maintenir une teneur minimal de cuivre en position d'échange, afin de conserver une capacité de stockage en ammoniac suffisante, mais surtout pour garantir une bonne efficacité à basse température en SCR du NO. Le maintien de la structure de la zéolithe semble essentiel pour que le catalyseur conserve une bonne efficacité et sélectivité au cours du temps. / The Selective Catalytic Reduction (SCR) by ammonia, or urea, is a well-known after-treatment process used for converting efficiently the nitrogen oxides, emitted by Diesel engines, into nitrogen and water. Copper-exchanged zeolites are among the most efficient formulations for light-duty applications, since effective over a wide temperature-range. The aim of this thesis is to study the hydrothermal stability of this type of catalyst. The approach used is this work is based on the study of the catalytic properties of a fresh commercial monolith catalyst for NH3-SCR in fresh and after different ageing conditions, at synthetic gas test bench, coupled with a comprehensive physicochemical analysis of the catalyst active phase. This allowed us to understand the deactivation phenomena occurring during a hydrothermal ageing and the impact on the catalyst activity and selectivity. A hydrothermal treatment induces a dealumination of the zeolite, into a more or less significant extent, which can lead to its collapse, as well as important modifications of the copper sites, even at low ageing. The results showed the importance to maintain a minimal copper content into exchanged sites, in order to retain a sufficient ammonia storage capacity, and especially to provide a good efficiency for the SCR of NO at low temperature. The preservation of the zeolite structure seems to be essential in order to maintain the catalyst efficiency and selectivity over time.

Copper based alloys play important role in high heat flux applications, particularly in rocket technology, the liner of the combustion chamber, and also in other heat transfer vessels. In these applications, one needs excellent high-temperature strength without sacrificing the thermal conductivity significantly. However, it is a challenging and difficult task to significantly improve the balance between strength and conductivities (electrical and thermal) of Cu-based alloys. In general, microstructural attributes, responsible for increasing mechanical strength of the alloy, also affect the transport properties by creating scattering centers. Hence, delicate optimization is needed for developing balanced alloy system for better performance. A substantial amount of research efforts has therefore been focused on devising methodologies to synthesize copper based alloys with a good combination of strength and conductivity. The present thesis deals with the development of a newer class of high strength high conductivity copper base alloy through tuning of phase transformation and careful additions of ternary and quaternary alloying elements and ultimately by microstructural engineering. In this thesis, we report the development of novel high strength high conductivity Cu-based alloy series in the Cu-Fe-Si system through rapid solidification process using suction casting apparatus. We have also optimized the alloys by altering and fine tuning the alloy compositions in order to achieve balanced and optimum properties. The strength of copper can be increased by various strengthening mechanisms. In general, precipitation hardening, dispersion strengthening and solid solution strengthening are the three most effective mechanisms for improving the strength of copper. Among these, solid solution strengthening has the most detrimental effect on the transport properties due to the presence of solute atoms which act as prominent scattering centres. Precipitation hardened copper alloys are often unable to retain strength at high temperatures, due to the coarsening of the precipitates. Currently, efforts are being made to develop newer dispersion strengthened copper alloys. These alloys contain a fine dispersion of nanometer sized oxides or other intermetallic compounds in the copper matrix. Dispersion strengthened copper alloys show impressive mechanical strength as well as thermal stability. In this thesis, we have explored the possibility of obtaining structurally ordered intermetallic dispersions through exploiting immiscibility of solutes in copper based alloys. The immiscibility promotes precipitation and decrease the solid solubility of solute elements in the matrix which in turn minimizes the scattering process and thus offers the possibility of improved transport properties. These ordered and coherent dispersion of intermetallic particles in the continuous copper matrix, dispersed during solidification, are believed to be the main contributor to the improvement of mechanical strength of the alloy. Crystallographically ordered structure and the coherency strain associated with the intermetallic particles in the copper matrix, together contribute to the mechanical strength through the mechanism of order hardening and coherency strengthening. These also, promote a low interfacial energy between precipitates and matrix in the alloy. This low interfacial energy reduces the driving force for coarsening process and thus helps in retaining the mechanical strength at elevated temperatures. Releasing of coherency strain at the precipitate-matrix interface with increasing temperature also yields a dramatic effect on the enhancement of thermal conductivity at high service temperatures. In the current study, we have selected three alloy compositions in the Cu-Fe-Si system at the higher end of copper. These are Cu-20Fe-5Si (at%), Cu-2.5Fe-2.5Si (at%) and Cu-1.0Fe-1.0Si (at%) respectively. We have systematically increased the concentration of copper, and altered the ratio of Fe and Si in order to achieve the better combination of properties (mechanical and transport) through fine tuning the microstructure. The present sets of alloys have been chill cast by the suction casting technique. This rapid solidification process, associated with moderate undercooling, is capable of accessing the submerged metastable miscibility gap of the Cu-Fe binary system. The higher quenching rate moves the system far away from equilibrium and hence, the solidification process occurs at the non-equilibrium regime. Rapid solidification of a copper rich Fe-Cu melt promotes the precipitation of the γFe from copper solid solution due to the immiscibility of Fe and Cu. In this scenario, the addition of a small quantity of silicon as a ternary element leads to its partition to both copper and iron rich phases. However, the larger chemical affinity between Fe and Si, leads to the formation of an ordered structure. However, the FCC crystal field of the copper matrix tends to promote an FCC based novel L12 ordered structure of the Fe3Si intermetallic particles instead of the ordered DO3 structure of Fe3Si composition normally observed in the bulk alloy. This nano meter sized L12 ordered particles maintain a cube-on-cube orientation relationship with the surrounding copper matrix and are associated with large coherency strain. A good lattice matching between these L12 ordered particles and copper matrix will promote a low interfacial energy and thus, a low driving force for particle coarsening. The present thesis is divided into eight chapters. The first chapter introduces the present work and the organization of the thesis. In the second chapter, current status in the development of the copper alloys and the general principle of alloy developments has been described. This includes both experimental and theoretical developments that can be used for developing high strength Cu based alloys. Chapter three, titled as „experimental procedure‟, describes the detailed description of materials and experimental techniques, adopted for the current studies. There are three chapters that deal with the main results of the thesis. Chapter eight, describes the suggestion for future work. The fourth chapter, titled as „Chill cast Cu75Fe20Si5 alloy: Microstructural Evolution and Properties‟, explores the detailed microstructural evolution of the Cu75Fe20Si5 alloy. This chapter also discusses the microstructure-property correlations. The microstructure of the alloy exhibits a multi-scale hierarchical structure during rapid solidification. The solidified microstructure contains Fe-rich globules with DO3 ordered structure, embedded in the continuous Cu-rich matrix. The continuous copper matrix also contains nanometer sized (average diameter 12 nm) coherent particles that exhibit Ashby-Brown strain contrast. Characterization of these phases has been carried out by a combination of X-ray diffraction, electron probe microanalysis and transmission electron microscopy coupled with energy dispersive spectroscopy. This multi-scale complex copper alloy (Cu75Fe20Si5 ) has achieved a remarkable yield and ultimate tensile strength at both room temperature and elevated temperatures in comparison to other copper based alloys. The yield strength and ultimate tensile strength at room temperature are 516±17 MPa and 635±14 MPa respectively whereas yield strength and ultimate tensile strength at 6000C turn out to be 95±11 MPa and 105±12 MPa respectively. In spite of achieving good mechanical strength, this alloy suffers from deterioration of electrical and thermal conductivity due to the presence of high volume fraction of the second phase and alloying elements. The room temperature electrical resistivity of this alloy shows that it is 10 times higher than that of pure copper (alloy resistivity = 1.70E-05 Ohm-cm at 250C and pure Copper- 1.68 × 10-6 Ohm-cm at 200C ). The thermal conductivity of this alloy turns out to be 88 W/m.K at 500C and 161 W/m.K at 6000C respectively which is much smaller in comparison to pure copper ( pure copper ≈ 401 W/m.K at 50 to 6000C). Attempts have been made to overcome the lowering of the transport properties by careful alteration of alloy compositions and fine tuning the microstructure. A new alloy with composition Cu-2.5Fe-2.5Si (at %) has been synthesized in order to achieve better transport properties without significantly sacrificing the mechanical strength. In this new alloy, we have reduced the volume fraction of the second phase (Fe-rich DO3 ordered globules) by lowering the addition of the alloying elements. We have also tried to alter the Fe to Si ratio in such a way that we can retain nanometer sized coherent particles in the matrix that provides strengthening. We arrived at a Fe and Si atom ratio of 1:1. The study of this alloy is presented in chapter five titled as „Chill cast Cu95Fe2.5Si2.5 alloy: Microstructural Evolution and Properties‟. Microstructural characterization indicates that the alloy contains only the nano meter sized coherent L12 ordered particles in the copper matrix. These particles show the Ashby-Brown strain contrast and are rich in iron and silicon. The absence of the high volume fraction of DO3 ordered Fe-rich globular phase and the smaller addition of the alloying elements ensure an improvement in the transport properties. The average resistivity value of this alloy at 250C is 3.5053 × 10-6 (Ohm-cm). This value represents a dramatic improvement in electrical properties in comparison to the Cu75Fe20Si5 alloy (Cu75Fe20Si5 alloy: 1.70E-05 Ohm-cm at 250C). The result is even better when we consider the temperature dependent thermal conductivity of the Cu95Fe2.5Si2.5 alloy. The thermal conductivity of this alloy turns out to be 236 W/m.K at 500C and 313 W/m.K at 6000C respectively. Though the thermal conductivity at room temperature is lower than pure copper, the gap reduces with increasing temperature (pure copper ≈ 401 W/m.K at 50 to 6000C and Cu75Fe20Si5 alloy: 88 W/m.K at 500C and 161 W/m.K at 6000C). This trend of temperature dependent thermal conductivity has made this alloy as one of the potential candidates for high-temperature applications. In situ heating experiment using transmission electron microscope (up to 4500C) and the heat treatment analysis at 6000C confirm that these L12 ordered particles are structurally stable at high temperatures and believed to be the main contributor to high mechanical strength in the alloy through the mechanism of order hardening and coherency strengthening. Coherent nature of the interface between the ordered particles and copper matrix also promotes low interfacial energy in the alloy and thus offers resistance to coarsening at elevated temperatures. Along with the attractive transport properties, this alloy also exhibits its success of retaining mechanical strength at both ambient and high temperatures as compared to the earlier alloy. The room temperature yield strength and ultimate tensile strength of this alloy are recorded as 580±18 MPa and 690±16 MPa respectively whereas the yield strength and ultimate tensile strength at 6000C of this alloy obtained as 128±8 MPa and 150±10 MPa respectively. Thus newly modified alloy exhibits an excellent balance between mechanical strength and conductivity (electrical and thermal) and can be regarded as a promising alloy for high strength high heat flux applications. The possibilities of the Cu95Fe2.5Si2.5 alloy as a potential candidate for high strength high conductivity application has provided the motivation for further optimization of the composition of this class of alloy. Mechanical strength and transport properties of a precipitation strengthened alloy always depends on the structure, shape, volume fractions and the number densities of the precipitate particles. Electrical and thermal conductivity are also sensitive to the presence of third elements and the number densities of the precipitates in the alloy. Thus, optimization of the volume fraction and the number density of the precipitates can yield a better alloy. With this objective, we have further increased the concentration of copper while keeping the Fe and Si atom ratio fixed at 1:1. Chapter six, titled as „Chill cast Cu98Fe1.0Si1.0 alloy: Microstructural Evolution and Properties‟ describes the microstructural evolution and microstructure-property correlation of this new alloy. Characterization analysis (X-ray diffraction, electron probe microanalysis and transmission electron microscopy) confirms that the microstructure of this alloy contains similar kind of nanometer sized L12 ordered particles with lower number density as compared to Cu95Fe2.5Si2.5 alloy (Relative planar number density of the particles: Cu98Fe1.0Si1.0 = 0.13 and Cu95Fe2.5Si2.5 = 0.20). This nano sized coherently ordered particles show the similar Ashby-Brown strain contrast and are rich in iron and silicon similar to the Cu95Fe2.5Si2.5 alloy. This dilute alloy exhibits slight improvement in transport properties in comparison to the earlier Cu95Fe2.5Si2.5 alloy. The electrical resistivity of this alloy at 250C is 3.438E-6 Ohm-cm (Cu95Fe2.5Si2.5 = 3.5053 × 10-6 Ohm-cm at 250C). The thermal conductivity values of this alloy are 243 W/m.K and 338 W/m.K at 500C and 6000C respectively (Cu95Fe2.5Si2.5 = 236 W/m.K at 500C and 313 W/m.K at 6000C). This increase in transport properties is associated with further compositional dilution and the presence of lower number density of the ordered particles in the copper matrix. The mechanism of strengthening is similar to the earlier alloys. The only difference lies in the fact that this present alloy contains lower number density of the L12 ordered particles in the copper matrix. This lower number density is responsible for the loss in mechanical strength of this alloy. The room temperature yield strength and the ultimate tensile strength of this present alloy are 467±16 MPa and 558±12 MPa whereas yield strength and ultimate tensile strength at 6000C are recorded as 102±13 MPa and 110±12 MPa respectively. Though the alloy exhibits some loss in mechanical strength, the values are still attractive in comparison to other commercially available copper based alloys. Both the alloy Cu98Fe1.0Si1.0 and Cu95Fe2.5Si2.5 demonstrate an excellent balance of mechanical strength and transport properties and have the potential to become a high strength and high conductivity materials for high temperature applications. Chapter seven is entitled as „Comparison between the alloy systems‟. In this chapter, we have presented a comparison of our new alloys with other commercially available Cu-base alloys. The thesis ends with a chapter titled as “Suggestions for future work”. We have included a descriptive note for possible future extension of our current work in this chapter.

L’hydrogénation catalytique du CO2 est considérée comme l’une des voies de valorisation les plus prometteuses pour la production du méthanol. Cette synthèse, souvent accompagné par une formation de CO, a fait l’objet de nombreuses études dans la littérature. Cependant, les résultats obtenus sur des catalyseurs à base de Cu et de ZnO ont démontré que cette réaction n’est pas aussi simple qu’elle y paraissait. Il y a encore beaucoup de controverses et d’interrogations sur la nature des sites actifs et sur les différentes étapes réactionnelles mises en jeu lors de la réaction. L’objectif de ce travail est d’apporter des éléments de compréhension sur la nature des sites actifs et leur rôle sur l’activation du CO2 et de H2. L’étude sur des catalyseurs modèles (mélanges mécaniques et matériaux préparés par coprécipitation) a permis de mettre en évidence un effet de synergie entre Cu et ZnO lié à des phénomènes de migration. Ce travail a montré que la production de méthanol est étroitement liée à la création d’une phase oxyde de type CuxZn(1-x)Oy (lacunaire en oxygène) induit par un effet de Kirkendall à l’interface Cu-ZnO, favorisant l’épandage de l’hydrogène. Différents modèles mathématiques ont été développés afin de déterminer la concentration des contacts entre Cu et ZnO. Les résultats obtenus ont démontré qu’il est possible de corréler directement l’activité du catalyseur avec la concentration de contacts et que cela peut permettre ainsi de prédire la composition chimique idéale du catalyseur pour un design de matériau donné. L’expertise complète de la relation design-activité a permis le développement de matériaux Cu-ZnO de type cœur-coquille 100% sélectif en méthanol. / The catalytic CO2 hydrogenation is considered to be one of the most promising methods for methanol production. This synthesis, often accompanied by a CO formation, had been the subject of many studies in the literature. However, the results obtained on Cu and ZnO based catalysts demonstrated that the reaction is not as simple as it appear to be. There is still a lot of controversies and interrogations concerning the nature of the active sites and the different reactional steps involved during the reaction. The objective of this work is a better understanding of the nature of the active sites and their role on CO2 an H2 activation. A study on model catalysts (mechanical mixtures and materials prepared by coprecipitation) allowed to demonstrate that the synergetic effect between Cu and ZnO linked to a migration phenomenon. This work showed that the methanol production was closely linked to the CuxZn(1-x)Oy oxide phase creation (with oxygen vacancies) induced by a Kirkendall effect on Cu-ZnO interface, thereby promoting the hydrogen spillover. Different mathematical models were developed to determine the concentration of contacts between Cu and ZnO. The results obtained demonstrated that it is possible to directly correlate the catalyst’s activity with the concentration of contacts between Cu and ZnO, which in turn allowed predicting optimal catalyst chemical composition for a particular design of a material. The full expertise of the design-activity relationship allowed the development of Cu-ZnO core-shell type materials with a 100% selective to methanol.

Quarante ans après la découverte de la circulation hydrothermale profonde, les processus chimiques se produisant dans le mélange entre le fluide hydrothermal et l’eau de mer restent mal contraints. Ce travail de thèse, dont l’originalité repose sur l’utilisation systématique de la filtration in situ, présente le partitionnement effectif des éléments métalliques majeurs (principalement Fe, Cu, Zn, Ba et Ca) entre les phases dissoutes (< 0,45 μm) et particulaire (> 0,45 μm) dans le mélange précoce-intermédiaire de plusieurs fumeurs du champ hydrothermal Lucky Strike (37°N, MAR). Le comportement et la spéciation du Cu dans la fraction dissoute sont ensuite explorés plus en détail par le biais de compétitions de ligands et de mesures voltamétriques. Nos résultats démontrent en premier lieu l’importance de la filtration in situ pour s’affranchir des biais induits par le prolongement des réactions de précipitation ou de redissolution pouvant se produire lors de la remontée des échantillons. L’examen des fluides collectés à différentes reprises et sur une large panoplie de fumeurs (240 échantillons) démontre une variabilité spatiale des signatures chimiques le long de l'axe est-ouest du champ hydrothermal. Parmi les métaux étudiés, Fe, Ca et Ba sont principalement mesurés sous forme dissoute tandis que Cu et Zn sont majoritairement particulaires. Dans le mélange initital (50‒150°C, dMn > 50 μM), le pool de particules est dominé par de la sphalérite (ou wurtzite) et de la chalcopyrite, avec généralement moins de pyrite. Dans cette zone, les changements chimiques semblent cinétiquement limités et les fluides échantillonnés présentent une signature chimique proche de celle du fluide pur. Cependant, à mesure que le fluide hydrothermal se mélange à l'eau de mer (4‒50°C, dMn < 50 μm), le partitionnement de certains métaux alcalins et alcalinoterreux (Ca, Ba, Mg et Sr) entre les deux phases est profondément affecté par la précipitation de sulfates. Contrairement aux prédictions thermodynamiques, la précipitation d’anhydrite, de barite et potentiellement de caminite est observée dans la partie relativement froide du mélange (4-50°C). L’augmentation importante du pH dans cette zone conduit également à l’initiation de la précipitation d’oxydes de Fe. Enfin, dans la phase dissoute, les ligands du Cu semblent être principalement des sulfures inorganiques issus du fluide hydrothermal. / Forty years after the discovery of deep hydrothermal circulation, chemical processes occurring in the early mixing between hydrothermal vent fluids and deep seawater are still not fully constrained. This thesis, whose the originality lies on the systematic use of in situ filtration, report on the partitioning of major metals (mainly Fe, Cu, Zn, Ba and Ca) between the dissolved (< 0.45 μm) and particulate (> 0.45 μm) phases in the early mixing of several black and clear smokers from the Lucky Strike vent field (37°N, MAR). The behavior and the speciation of Cu in the dissolved fraction are then deeper explored by performing ligands competition and voltammetric measurements. Our results first demonstrate the importance of the in situ filtration to restrict the bias induced by precipitation reactions or particles redissolution potentially occurring postsampling.The examination of the fluids collected at several occasions and on a wide range of smokers (240 samples) shows a spatial variability of chemical signatures along the east-west axis of the hydrothermal field. Among metals studied, most of Fe, Ca and Ba are measured as dissolved species whereas Cu and Zn are mainly found as particles. In the initial part of the mixing (50-150°C, dMn > 50 μM), the particulate pool is dominated by sphalerite (or wurtzite) and chalcopyrite, with generally lower amount of pyrite. In this zone, chemical changes seem kinetically limited and fluids collected display a chemical signature close to that of the end-members. However, as the hydrothermal fluid progressively mixes with seawater (4-50°C, dMn < 50 μm), the partitioning of some alkali and alkaline earth metals (Ca, Ba, Mg and Sr) between the two phases is deeply affected by precipitation of sulfates. Unlike thermodynamic predictions, precipitation of anhydrite, barite and potentially caminite is observed in the colder part of the mixing (4-50°C). The large increase of pH in this area also drives the beginning of Fe oxides precipitation. Finally, the dissolved Cu-ligands detected seem to be mainly inorganic sulfides originating from the hydrothermal fluid.

Ces dernières années, l’évolution de la taille des circuits intégrés a été dirigée par la loi de Moore conduisant à des noeuds technologiques de 22 nm et en-deçà. Cependant, les problématiques de performances, de taille et de coût des composants rendent cette conjecture difficile à suivre. La tendance de diversification appelée « More than Moore » consiste à intégrer des fonctions analogiques avec des technologies CMOS dans le but d’optimiser les coûts.L'une de ses technologies clés est le TSV, qui maintient le contact entre deux niveaux de composants. Leurs facteurs de forme devenant de plus en plus élevés, les techniques de dépôts standards par iPVD sont proches de leurs limites. De plus, les méthodes de caractérisation usuelles ne sont pas adaptées à ces structures.La première partie de cette thèse sera dédiée au développement des procédés de dépôt de la barrière de diffusion du cuivre par MOCVD à basse température pour s’adapter aux divers schémas d'intégration de type via middle et via last. La deuxième partie sera consacrée à l’élaboration des protocoles avancés de caractérisation des films dans ces structures afin d’étudier leurs comportements en intégration. / For the past years, Moore’s law has pointed mainstream microelectronics, driving integrated circuits down to 22 nm and below. Yet, performance, dimension and cost issues make it difficult to follow the trend. Integrating analog functions into CMOS-based technologies enables cost-optimized systems solutions. These diversified tendencies are known as “More than Moore”. One of the key technologies of this trend is the TSV, which maintains the contact between two components.The increasing aspect ratio of via made it critical to obtain a continuous, conformal coverage of the copper diffusion barrier layer using iPVD.In the first part of this thesis, a promising deposition technique by MOCVD has been developed at low temperature to fulfill various integration schemes including via last and via middle processes.Characterizations of the behavior of these materials in the TSV then became a great challenge in order to handle the integration protocol. Working at theses scales makes standard methods limited to evaluate the intrinsic properties inside the TSV. In the second part, the implementations of advanced characterization into these structures were carried out.

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / Propylene is a chemical compound with high value added, widely used in the industry and usually obtained from petroleum. However, there is the need of the development of alternative routes for the production of this compound from renewable sources. The use of acetone for the production of propylene is a good option, because this oxygenated compound can be obtained by biomass conversion. The use of a one step process also adds an advantage to the propylene production from acetone, uniting in a single reactor two consecutive reactions: acetone hydrogenation, followed by dehydration of the formed isopropanol. For this, there are necessary two catalysts with distinct properties, one containing metallic sites, for hydrogenation, and another where there are acidic sites, for dehydration. The main objective of this work is to obtain propylene from acetone in one single step, using Cu/Zn/Al mixed oxide derived from hydrotalcite-like compounds and acid form of Beta zeolite as catalysts. For that, the catalysts were obtained by the coprecipitation method at variable pH followed by calcination, for the mixed oxide, and by hydrothermal synthesis, for the zeolite. The catalysts were also characterized as their with distinct properties. The hydrogenation and dehydration reactions have been studied individually and together by varying the catalyst or mixture of catalysts employed and the composition and flow rate of the feed. First, they were evaluated the thermodynamic boundaries of the reaction systems in which was observed that the acetone hydrogenation is strongly limited by the equilibrium and which are the preferential products of each reaction. For the reaction test, it was used the factorial experimental design, where the feeding conditions and reaction temperature were varied, and as response variables it was obtained the composition of the organic fraction at the reactor outlet. In the hydrogenation reaction, only isopropanol was obtained and the acetone conversion was close to that of equilibrium. In the dehydration reaction of isopropanol, propylene was preferably formed, with only small concentrations of diisopropyl ether at low temperatures, being obtained complete alcohol conversion in some experimental conditions. The complete process of acetone conversion into propylene was carried out at eleven distinct experimental conditions and the olefin fraction was up to 65 % of the organic fraction. It was possible the parameters estimation of simplified kinetic models, considering the Langmuir-Hinshelwood hypothesis, appropriate to the prediction of the molar fractions of the compounds in the organic fraction for both individual as simultaneous reactions. The kinetic models were used to the analysis of the effect of process variables on the reaction products in the three reaction systems considered. / O propeno é um composto químico de alto valor agregado, largamente empregado na indústria e obtido, geralmente, a partir do petróleo. Entretanto, há a necessidade do desenvolvimento de rotas alternativas para a produção deste composto a partir de fontes renováveis. A utilização de acetona para a produção de propeno é uma boa opção, pois este composto oxigenado pode ser obtido através de conversão da biomassa. A utilização de processo em uma única etapa acrescenta, ainda, mais uma vantagem à produção de propeno a partir de acetona, unindo em um único reator duas reações consecutivas: hidrogenação de acetona, seguida da desidratação do isopropanol formado. Para tanto, são necessários dois catalisadores com propriedades distintas, um deles contendo sítios metálicos, para a hidrogenação, e outro onde haja sítios ácidos, para a desidratação. O objetivo principal deste trabalho é a obtenção de propeno a partir de acetona em uma única etapa, utilizando óxido misto de Cu/Zn/Al derivado de material do tipo hidrotalcita e forma ácida da zeólita Beta como catalisadores. Para isso, os catalisadores foram obtidos pelo método de coprecipitação a pH variável seguido de calcinação, para o óxido misto, e pela síntese hidrotérmica, para a zeólita. Os catalisadores foram, ainda, caracterizados quanto às suas propriedades físicoquímicas. As reações de hidrogenação e desidratação foram estudadas individualmente e em conjunto variando-se o catalisador ou mistura de catalisadores empregados e a composição e vazão da alimentação. Primeiramente, foram avaliados os limites termodinâmicos dos sistemas reacionais, em que se observou que a hidrogenação de acetona é fortemente limitada pelo equilíbrio e quais são os produtos preferenciais de cada reação. Para os testes reacionais foi utilizado planejamento de experimentos fatorial, onde as condições de alimentação e temperatura de reação foram variadas, e como variáveis resposta obteve-se a composição da fração orgânica na saída do reator. Na reação de hidrogenação, apenas isopropanol foi obtido e a conversão de acetona foi próxima daquela de equilíbrio. Na reação de desidratação de isopropanol, o propeno foi formado preferencialmente, com apenas pequenas concentrações de éter di-isopropílico a baixas temperaturas, sendo obtidas conversões completas do álcool em algumas condições experimentais. O processo completo de conversão de acetona em propeno foi realizado em onze condições experimentais distintas e a fração de olefina foi de até 65 % da fração orgânica. Foi possível a estimação dos parâmetros de modelos cinéticos simplificados, considerando as hipóteses de Langmuir-Hinshelwood, adequados à predição das frações molares dos compostos na fração orgânica tanto para as reações individuais como simultâneas. Os modelos cinéticos foram utilizados para a análise do efeito das variáveis de processo sobre os produtos de reação nos três sistemas reacionais considerados.

In this work were synthesized and studied four new coordination compounds of copper(II) with phenylseleninato ligand, three of them polymeric and one molecular. The reaction of phenylseleninic acid with copper(II) acetate led to microcrystalline light blue powder of polymeric compound catena-poli-[Cu(μ2-O2SePh)2], 1. That powder was used to obtain crystalls of 1 and three others: catena-poli-[Cu(μ2-O2SePh)2(NH3)], 2, obtained by the dissolution of 1 in dmf and aqueous ammonia, catena-poli-[Cu(μ2-O2SePh)2(NC5H5)]·NC5H5, 3, obtained by the dissolution of 1 in pyridine and aqueous ammonia, and poli-[Cu(O2SePh)2(NH3)2(H2O)2], 4, obtained by the dissolution of 1 in water and aqueous ammonia. Compound 1 is a two-dimensional coordination polymer with layers formed by the phenylseleninato double bridges between copper(II) units. The copper(II) centers in the same layer form a (4,4) net topology. Magnetic susceptibility measurements of the crystalline sample of 1 was carried out on a SQUID magnometer and strong ferromagnetic coupling was verified between 10 and 6.3 K. Below 6.3 K was verified a weak antiferromagnetic interactions between partially ordered ferromagnetic layers. All the new compounds were characterized by X-ray diffraction, infrared spectroscopy and elemental analysis. Compounds 2 and 3 have supramolecular nature due to hydrogen bonds in those structures. Only compound 3 is a one-dimensional coordination polymer. / Neste trabalho foram sintetizados e estudados quatro novos compostos de coordenação de cobre(II) com o ligante fenilseleninato, três deles poliméricos e um molecular. A reação do ácido fenilselenínico com acetato de cobre(II) originou um pó microcristalino e azul-claro, referente ao composto polimérico catena-poli-[Cu(μ2-O2SePh)2], 1. Esse foi o composto de partida para a obtenção de cristais de 1, além da obtenção de outros três compostos cristalinos: catena-poli-[Cu(μ2-O2SePh)2(NH3)], 2, obtido pela dissolução de 1 em dmf e amônia aquosa; catena-poli-[Cu(μ2-O2SePh)2(NC5H5)]·NC5H5, 3, obtido pela dissolução de 1 em piridina e amônia aquosa; e [Cu(O2SePh)2(NH3)2(H2O)2], 4, obtido a pela dissolução de 1 em água e amônia aquosa. O composto 1 é um polímero bidimensional em camadas formadas pelo centro metálico e o ligante, no qual os centros de cobre(II) são conectados por pontes duplas de fenilseleninato. Esses centros distribuem-se nas camadas com uma topologia de rede (4,4). Estudos de propriedades magnéticas com um magnetômetro do tipo SQUID evidenciaram fortes interações ferromagnéticas entre 10 e 6,3 K, quando ocorre uma transição antiferromagnética, com queda brusca dos valores do inverso da susceptibilidade magnética, provavelmente por interações antiferromagnéticas entre os planos de Cu(II) paralelos. Todos os novos compostos foram caracterizados por difração de raios-X, espectroscopia de infravermelho e análise elementar. A instabilidade e decomposição, por perda de solvente, das estruturas 2 e 4 impediram estudos de magnetismo, porém a elucidação de suas estruturas cristalinas evidenciaram a existência de interessante caráter supramolecular devido a presença do ligante NH3, em 2, e NH3 e H2O, em 3. As ligações de hidrogênio nesses compostos mostraram-se importantes na manutenção de suas estruturas no estado sólido, assim como na formação de camadas com topologia de rede (4,4). Somente o composto 3 mostrou-se como um polímero de coordenação unidimensional.

Dans ce travail, Al-Cu échantillons modèle en alliage ont été chauffés sous vide ultra élevé, et on a trouvé que l'oxyde Al grandi et Cu pertage inceased en fonction de l'exposition à l'O2 en raison de l'oxydation préférentielle de Al. échantillons ont ensuite été recuits à 540 °C sous vide poussé et vieilli à 300 °C dans l'air, et corrodés en peu de temps dans l'électrolyte neutre et l'électrolyte alcalin contenant des ions Cl- en utilisant le système à trois électrodes, respectivement. Après immersion dans l'électrolyte neutre, corrosion morphologies (creusement de tranchées sur l'échantillon poli vs fosses creuses sur l'échantillon vieilli) se distinguent. Cependant, dans un électrolyte alcalin, la corrosion a à deux phases en raison de la dissolution de l'aluminium et de l'oxyde d'aluminium dans une solution alcaline: d'une part, un oxyde d'Al et la matrice d'Al ont été dissous en général, ce qui entraîne riche en Cu intermétalliques étant laissé isolément sur la surface; d'autre part, la corrosion générale a ensuite accompagné la dissolution préférentielle du substrat environnant riche en Cu intermétalliques résultant dans des tranchées autour des particules. Formation des mixtes Al-Cu oxydes riche en Cu2O et CuO dépôts ont été trouvés sur la surface corrodée. En outre, les échantillons Al-Cu recouvertes de revêtements Al2O3 déposés par procédé ALD à la surface ont été corrodés dans des conditions similaires. Comme on s'y attendait, une amélioration significative de la résistance à la corrosion des échantillons d'alliages revêtus a été observée, mais la couche d'ALD dans l'électrolyte alcalin est pas aussi stable que dans les électrolytes neutres. / In this work, Al-Cu model alloy samples were heated in ultra high vacuum (UHV), and it was found that the Al oxide grew and Cu percentage increased as a function of exposure to the O2 owing to the preferential oxidation of Al. Then samples were annealed at 540 °C in high vacuum and aged at 300 °C in air, and corroded in short time in the neutral electrolyte and the alkaline electrolyte containing Cl- ion using the three-electrode system, respectively. After immersion in the neutral electrolyte, corrosion morphologies (trenching on the polished sample vs. hollow pits on the aged sample) are distinguished due to the different distributions of Cu-rich intermetallics in the polished sample (distributed homogeneously) and the aged sample (mostly beneath the oxide layer). However, in alkaline electrolyte, corrosion went at two stages owing to the dissolution of aluminium and aluminium oxide in an alkaline solution: firstly, Al oxide and the Al matrix were dissolved generally, resulting in Cu-rich intermetallics being left isolatedly on the surface; secondly, general corrosion went on accompanied with the preferential dissolution of substrate surrounding Cu-rich intermetallics resulting in trenching around particles. Formation of mixed Al-Cu oxides/hydroxides layer rich in Cu2O and CuO deposits were found on the corroded surface. Furthermore, Al-Cu samples covered with Al2O3 coatings deposited by ALD process on the surface were corroded under similar conditions. As expected, a significant improvement of corrosion resistance of the coated alloy samples was observed, but the ALD layer in alkaline electrolyte is not as stable as in neutral electrolytes, and undergoes dissolution.

No description available.

The present thesis deals with synthesis of free alloy nanoparticles in immiscible alloy systems by the process of laser ablation under a liquid. In this process the alloy target is submerged in a liquid and the plume formed by the laser beam interaction with the target is confined in the liquid. The nanoparticles formed inside this plume and get quenched by the surrounding liquid yielding suspension of nanoparticles in the liquid. By the addition of suitable surfactants, these nanoparticles can be protected from other reactions and their size can be controlled by preventing further growth. We have selected immiscible alloys for the present study. These alloys tend to phase separate in melt as well as in solid depending on the value of the positive heat of mixing. We have used two binary alloys for the present study. These are alloys in Ag-Cu system and Fe-Cu system. In both these systems, there are reports of formation of extended solid solution due to kinetic factors during nonequilibrium processing like rapid solidification and mechanical alloying. In the present thesis we report synthesis of alloy nanoparticles of different compositions and sizes in these two systems and explore the nature of the phases that form in the small (nano) particles and their evolutionary pathways leading to the final microstructure. Microscopic techniques, especially transmission electron microscope, were used for characterization of these nanoparticles. The phase evolution was further studied using in situ microscopic techniques. After introducing the thesis in the Chapter 1, we describe briefly the relevant literatures in Chapter 2. The experimental details, in particular the experimental set up for laser ablation with targets under liquid are described in chapter 3. This chapter also includes the experimental details of the characterization. Transmission electron microscopy was used as primary characterization tool in the present study. The Chapter 4 presents the result of our study of alloy nanoparticles in Fe-Cu system. This system exhibits a submerged liquid miscibility gap. Although we have studied alloy targets of different compositions, the results of alloy nanoparticles obtained from targets with compositions Cu-40at.%Fe and Cu-60at.%Fe were primarily presented in this chapter. The nanoparticles that were synthesized had a size range of approximately 40nm to more than 100 nm. These particles have spherical morphology. The measurements of local compositions of different locations in the particle indicate the presence of a layer of Fe3O4 oxide at the spherical surface. This layer is devoid of copper. Most of the copper exist in the core of the particle. Fe rich spherical particles of much smaller size (~15 nm) are found to be embedded in the copper rich core. The copper formed solid solution with Fe and a copper concentration gradient exists in the particle below oxide layer due to oxidation of Fe. In contrast the nanoparticles obtained from alloy target with composition Fe-40at.% Cu have a spherical morphology. These have a composite structure with a Fe core in addition to Fe3O4 oxide layer at the surface. We have attempted to explain the phase evolution taking into account under cooling of the melt condensate that forms in the plume and their subsequent solidification through submerged miscibility gap. The chapters 5-7 deals with alloys of Ag-Cu system. In Chapter 5, we have carried out a detailed study of morphological evolution of the nanoparticles of Ag-Cu system. After optimizing the ablation parameters using pure Ag and Cu targets, we have synthesized alloy nanoparticles using different target compositions over the entire range of compositions with sizes having a mode of 25 nm. The evolution of the two phase structure is shown to be composition dependent with particles near equiatomic composition exhibit solid solution with uniformly distributed segregations of composition (Cu & Ag rich) while copper rich alloys exhibit a core shell structure with outer layer being Ag rich. The isothermal experiments again reveal emergence of core-shell morphology at intermediate time for particles with equiatomic composition. In order to compare the results of Ag-Cu nanoparticles with particles produced by other techniques we have synthesized Ag-Cu nanoparticles of near equiatomic composition by chemical route using nitrate salts and NaBH4 as reducing agent. PVP was used as capping agent. The results are presented in chapter 6. Depending on time of reaction, it is possible to synthesis free alloy particles from 2-3 nm to a network of chains. The nanoparticles contain Ag rich and Ag deficient region with Ag tends to segregate near surface. We have also presented mechanism for the formation of chain structure with prolonged reaction. The thermodynamic basis of phase formation in the immiscible system and evolution of phases under nonequilibrium situation have been discussed in chapter 7. This also includes a model to estimate size dependent surface energy. The analysis presented allows a discussion of possible pathways for phase evolution observed in the present work. The thesis ends with a final chapter that discussed the critical issues remains to be addressed and possible future work.