Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2018-09-19T12:12:01Z No. of bitstreams: 1 2010 - Rafael Sanches Pacheco.pdf: 669093 bytes, checksum: 3ca2e98e7a5ac781dba791f2e1bfda70 (MD5) / Made available in DSpace on 2018-09-19T12:12:01Z (GMT). No. of bitstreams: 1 2010 - Rafael Sanches Pacheco.pdf: 669093 bytes, checksum: 3ca2e98e7a5ac781dba791f2e1bfda70 (MD5) Previous issue date: 2010-08-10 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico, CNPq, Brasil. / Nutrient concentration in the seeds can affect the initial development, biological nitrogen fixation (BNF) and yield of plants. Common bean (Phaseolus vulgaris L.) has been considered as a species with low capacity of BNF as compared to other grain legumes, but results demonstrate the potential of BNF to supply the N demand of the crop and to achieve adequate yields. The objective of this study was to evaluate the effect of seed concentrations of Mo and P on biomass production, nodulation and grain yield of common bean at different sources of N supply. The field experiment was conducted between April and July 2009, in the Santa Monica Farm of Embrapa Gado de Leite in the municipality of Valen?a ? Rio de Janeiro State. The experimental design was a split-plot 4x4 factorial randomized block with 5 replicates. The main plots consisted of four N sources: control without N, mineral N fertilization with 20 kg N ha-1 at sowing + 40 kg N ha-1 in cover, inoculation with the commercial strain of rhizobia, rhizobia inoculation + 40 kg N ha-1 in cover. The subplots consisted of four combinations between concentrations of P and Mo in the seeds (low P low Mo, low P high Mo, Mo high P low, high-P high-Mo). The seeds of cultivar Carioca were originating from a field experiment when 5 kg P ha-1 and 120 g Mo ha-1 were foliar sprayed at 52 and 71 days after emergence (DAE). In each subplot, plant biomass were sampled at 30, 42 and 57 DAE, and root, shoot and nodules dry mass, the number of nodules and the accumulation of N in the shoot were determined. Grains were harvested at 90 DAE, and grain yield, yield components, N and Mo concentratios in the grains were measured. Interactions between the N sources and the concentrations of P and Mo in the seeds were not significant in the three sampling times, except for shoot dry mass and number of nodules at 57 DAE. Seeds with low P and high Mo increased shoot dry matter and grain yield of beans. Mineral N fertilizer increased root mass in the early growth stages. The rhizobia inoculation increased bean nodulation. There was a small effect of the seeds with high P concentration in the accumulation of N and mass of shoots at 57 DAE. Mineral N fertilizer increased N accumulation in the shoots at 57 DAE. The inoculation + 40 kg N ha-1 in cover gave similar grain yield and N accumulation as the application of 60 kg N ha-1, both treatments superior to the control. The use of seeds enriched with P and Mo, associated with the inoculation of seeds and the application of N in cover, could maximize the process of biological nitrogen fixation in the common bean crop. / A concentra??o de nutrientes nas sementes pode afetar o desenvolvimento inicial, a fixa??o biol?gica de nitrog?nio (FBN) e a produ??o de gr?os das plantas por elas geradas. O feijoeiro (Phaseolus vulgaris L.) tem sido considerado uma esp?cie de baixa capacidade de FBN em compara??o com outras leguminosas de gr?o, mas resultados demonstram o potencial da FBN em suprir a demanda de N do feijoeiro e obter boas produtividades. O objetivo deste estudo foi avaliar o efeito dos teores de P e Mo em sementes na produ??o de biomassa, nodula??o e no rendimento de gr?os de feijoeiro sob diferentes fontes de fornecimento de N. O experimento foi conduzido em condi??es de campo entre abril e julho de 2009, na Fazenda Santa M?nica da Embrapa Gado de Leite, no munic?pio de Valen?a ? RJ, em delineamento em blocos ao acaso em fatorial 4x4 com 5 repeti??es em parcelas subdivididas. As parcelas foram compostas por quatro fontes de N: testemunha absoluta sem N; aduba??o com N mineral com 20 kg N ha-1 no plantio + 40 kg N ha-1 em cobertura; inocula??o com a estirpe comercial de riz?bio recomendada para a cultura; inocula??o com estirpe comercial + 40 kg N ha-1 em cobertura. As subparcelas foram compostas por quatro combina??es entre teores de P e de Mo na semente (baixo P baixo Mo, baixo P alto Mo, alto P baixo Mo, alto P alto Mo). As sementes da cultivar Carioca utilizadas foram oriundas de um experimento de campo onde foram efetuadas aplica??es foliares com 5 kg P ha-1 e 120 g Mo ha-1 aos 52 e 71 dias ap?s emerg?ncia (DAE). Em cada subparcela foram efetuadas tr?s amostragens de biomassa, aos 30, 42 e 57 DAE, determinando-se a massa seca de raiz, parte a?rea e n?dulos, o n?mero de n?dulos e a acumula??o de N na parte a?rea. A colheita de gr?os foi efetuada aos 90 DAE, determinando-se o rendimento de gr?os, os componentes de produ??o e o teor de N e de Mo nos gr?os. As intera??es entre as fontes de N e os teores de P e Mo das sementes, nas tr?s ?pocas de coleta, n?o foram significativas, exceto para massa seca de parte a?rea e n?mero de n?dulos aos 57 DAE. As sementes com baixo P e alto Mo foram as que promoveram maior massa de parte a?rea e tamb?m a maior produ??o de gr?os de feij?o. A aduba??o com N mineral promoveu maior massa radicular nos est?gios iniciais de crescimento. A inocula??o das sementes com riz?bio aumentou a nodula??o do feijoeiro. Houve um pequeno efeito dos altos teores de P nas sementes na acumula??o de N e de biomassa da parte a?rea aos 57 DAE. A aplica??o de N mineral promoveu maior ac?mulo da N na parte a?rea aos 57 DAE. A inocula??o combinada com 40 kg N ha-1 em cobertura forneceu rendimento de gr?os e acumula??o de N nos gr?os similar ? aplica??o de 60 kg N ha-1, por sua vez superiores ? testemunha. O uso de sementes enriquecidas com P e Mo, associada com a inocula??o de sementes e a aplica??o de N em cobertura, podem maximizar o processo de fixa??o biol?gica de nitrog?nio na cultura do feijoeiro.

Among the obstacles for the commercialization of the MoltenCarbonate Fuel Cell (MCFC), the dissolution of thestate-of-the-art lithiated NiO cathode is considered as aprimary lifetime limiting constraint. Development ofalternative cathode materials is considered as a main strategyfor solving the cathode dissolution problem. LiFeO2and LiCoO2had earlier been reported as the most promisingalternative materials; however, they could not satisfactorilysubstitute the lithiated NiO. On the other hand, ternarycompositions of LiFeO2, LiCoO2and NiO are expected to combine some desirableproperties of each component. The aim of this work was todevelop alternative cathode materials for MCFC in the LiFeO2-LiCoO2-NiO ternary system. It was carried out byinvestigating electronic conductivity of the materials, firstin the form of bulk pellets and then in ex-situ sinteredporous-gas-diffusion cathodes, and evaluating theirelectrochemical performance by short-time laboratory-scale celloperations. Materials in the LiFeO2-NiO binary system and five ternary sub-systems,each with a constant molar ratio of LiFeO2:NiO while varying LiCoO2content, were studied. Powders withcharacteristics appropriate for MCFC cathode fabrication couldbe obtained by the Pechini method. The particle size of LiFeO2-LiCoO2-NiO powders considerably depends on thecalcination temperature and the material composition. Theelectrical conductivity study reveals the ability of preparingLiFeO2-LiCoO2-NiO materials with adequate electricalconductivity for MCFC cathode application. A bimodal pore structure, appropriate for the MCFC cathode,could be achieved in sintered cathodes prepared usingporeformers and sub-micron size powder. Further, this studyindicates the nature of the compromise to be made between theelectrical conductivity, phase purity, pore structure andporosity in optimization of cathodes for MCFC application. Cellperformance comparable to that expected for the cathode in acommercial MCFC could be achieved with cathodes prepared from20 mole% LiFeO2- 20 mole% LiCoO2- 60 mole% NiO ternary composition. It shows aniR-corrected polarization of 62 mV and a iR-drop of 46 mV at acurrent density of 160 mAcm-2at 650 °C. Altogether, this study revealsthe possibility of preparing LiFeO2-LiCoO2-NiO cathode materials suitable for MCFCapplication. Keywords: molten carbonate fuel cell (MCFC), MCFC cathode,LiFeO2-LiCoO2-NiO ternary compositions, electrical conductivity,porous gas diffusion electrodes, polarization, electrochemicalperformance, post-cell characterization.

<p>Among the obstacles for the commercialization of the MoltenCarbonate Fuel Cell (MCFC), the dissolution of thestate-of-the-art lithiated NiO cathode is considered as aprimary lifetime limiting constraint. Development ofalternative cathode materials is considered as a main strategyfor solving the cathode dissolution problem. LiFeO₂and LiCoO₂had earlier been reported as the most promisingalternative materials; however, they could not satisfactorilysubstitute the lithiated NiO. On the other hand, ternarycompositions of LiFeO₂, LiCoO₂and NiO are expected to combine some desirableproperties of each component. The aim of this work was todevelop alternative cathode materials for MCFC in the LiFeO₂-LiCoO₂-NiO ternary system. It was carried out byinvestigating electronic conductivity of the materials, firstin the form of bulk pellets and then in ex-situ sinteredporous-gas-diffusion cathodes, and evaluating theirelectrochemical performance by short-time laboratory-scale celloperations.</p><p>Materials in the LiFeO₂-NiO binary system and five ternary sub-systems,each with a constant molar ratio of LiFeO₂:NiO while varying LiCoO₂content, were studied. Powders withcharacteristics appropriate for MCFC cathode fabrication couldbe obtained by the Pechini method. The particle size of LiFeO₂-LiCoO₂-NiO powders considerably depends on thecalcination temperature and the material composition. Theelectrical conductivity study reveals the ability of preparingLiFeO₂-LiCoO₂-NiO materials with adequate electricalconductivity for MCFC cathode application.</p><p>A bimodal pore structure, appropriate for the MCFC cathode,could be achieved in sintered cathodes prepared usingporeformers and sub-micron size powder. Further, this studyindicates the nature of the compromise to be made between theelectrical conductivity, phase purity, pore structure andporosity in optimization of cathodes for MCFC application. Cellperformance comparable to that expected for the cathode in acommercial MCFC could be achieved with cathodes prepared from20 mole% LiFeO₂- 20 mole% LiCoO₂- 60 mole% NiO ternary composition. It shows aniR-corrected polarization of 62 mV and a iR-drop of 46 mV at acurrent density of 160 mAcm^-2at 650 °C. Altogether, this study revealsthe possibility of preparing LiFeO₂-LiCoO₂-NiO cathode materials suitable for MCFCapplication.</p><p>Keywords: molten carbonate fuel cell (MCFC), MCFC cathode,LiFeO₂-LiCoO₂-NiO ternary compositions, electrical conductivity,porous gas diffusion electrodes, polarization, electrochemicalperformance, post-cell characterization.</p>

Η παρούσα ειδική ερευνητική εργασία συνιστά μια μελέτη των μη-γραμμικών οπτικών ιδιοτήτων πέντε δειγμάτων νανοσωματιδίων οξειδίων μετάλλων. Κατ’ όνομα πρόκειται για το μονοξείδιο του Κοβαλτίου (CoO), το τετροξείδιο του Μαγγανίου (Mn3O4), το μονοξείδιο του Νικελίου (NiO), τον Αιματίτη (α-Fe2O3) και τον Μαγγεμίτη (γ-Fe2O3). Οι τρίτης τάξης οπτικές μη-γραμμικότητές τους διερευνήθηκαν με την πειραματική τεχνική Z-scan, της οποίας οι βασικές αρχές και οι πειραματικές λεπτομέρειες περιγράφονται στο δεύτερο κεφάλαιο της παρούσης. Ειδικότερα, δίδονται τεχνικές λεπτομέρειες για τις πειραματικές διατάξεις που χρησιμοποιήθηκαν, μελετώνται τα δύο κύρια φαινόμενα που αξιοποιεί η τεχνική, η μη-γραμμική διάθλαση και η μη-γραμμική απορρόφηση και γίνεται σύντομη μαθηματική περιγραφή και παράθεση της διαδικασίας ανάλυσης δεδομένων. Προηγείται των ανωτέρω μια περιεκτική θεωρητική θεμελίωση των βασικών αρχών της μη-γραμμικής οπτικής στο πρώτο κεφάλαιο. Αναπτύσσεται εκ των εξισώσεων Maxwell η μη-γραμμική κυματική εξίσωση. Περιγράφονται οι διεργασίες της γενέσεως δευτέρας αρμονικής, αθροίσματος και διαφοράς συχνοτήτων και διαδοχικά τα βαρύνουσας σημασίας φαινόμενα της αυτό-εστίασης, αυτό-απoεστίασης, κορέσιμης και ανάστροφα κορέσιμης απορρόφησης. Παρατίθεται εν συνεχεία ένας κβαντομηχανικός ορισμός της τρίτης τάξης μη-γραμμικής επιδεκτικότητος και τέλος περιγράφονται αναλυτικά οι μηχανισμοί συνεισφοράς στον μη-γραμμικό δείκτη διάθλασης, από την παραμόρφωση του ηλεκτρονικού νέφους, ως την ηλεκτροσυστολή και τα θερμικά φαινόμενα. Στο τρίτο κεφάλαιο παρουσιάζονται θεωρητικά στοιχεία για τις ιδιότητες των νανοσωματιδίων οξειδίων μετάλλων, την επίδραση του μεγέθους στις εγγενείς ιδιότητες της ύλης και παραδείγματα των πιο ευρέως διαδεδομένων εφαρμογών τους. Εν συντομία δίδονται οι τεχνικές σύνθεσης και οι ενδελεχείς χαρακτηρισμοί που εφαρμόστηκαν με σκοπό να φωτιστούν πλευρές της κρύφιας και ασαφούς φύσης των νανοσωματιδίων. Στο τέταρτο κεφάλαιο παρατίθενται λεπτομερώς οι πειραματικές μετρήσεις, από τα φάσματα απορρόφησης που ελήφθησαν για κάθε παρασκευασθείσα συγκέντρωση διεσπαρμένων νανοσωματιδίων, ως τις γραφικές παραστάσεις που αντιστοιχούν στην τεχνική Z-scan. Συγκεντρώνονται σε πίνακες όλες οι μη-γραμμικές οπτικές παράμετροι που υπολογίστηκαν και λαμβάνει χώρα αναλυτική συζήτηση για τα αποτελέσματα. Τα αποτελέσματα ομαδοποιούνται, εξάγονται ενδιαφέροντα συμπεράσματα και γίνεται σύγκριση με τη βιβλιογραφία. / The present work, a master thesis, is a study of the nonlinear optical properties of five metal oxide nanoparticles, namely Cobalt monoxide (CoO), Manganese tetroxide (Mn3O4), Nickel monoxide (NiO), Hematite (α-Fe2O3) and Maghemite (γ-Fe2O3). Their third ordrer optical nonlinearities were investigated by the means of the Z-scan experimental technique. The basic principles and the experimental details of this technique are described in the second chapter of the present work. Moreover, technical details of the experimental setups used are presented, the two most important phaenomena involved in Z-scan, nonlinear absorption and nonlinear refraction are described, a brief mathematical description and the data analysis details are given. In the first chapter, a comprehensive theoretical basis of the principles of Non-linear Optics is firstly established. Initiating from Maxwell’s equations, the non-linear wave equation is developed step-by-step. The non-linear optical processes of second harmonic generation and sum/difference frequency generation are presented. Consecutively, the very important phaenomena of self-focusing, self-defocusing, saturable and reverse saturable absorption are described. In addition, a quantum-mechanic description of third order nonlinear susceptibility is briefly developed. At last, the contribution mechanisms to the nonlinear refractive index, from the deformation of the electron cloud to the electrostriction and the thermal effects are presented. In the third chapter, some theoretical information about the properties of metal oxides nanoparticles, along with the effects of their size to their behavior and their widely known applications are listed. In brief, the unique details of the synthesis and the assiduous characterization techniques, which were applied in order to illuminate the fringe nature of these nanoscale particles, are given. In the fourth chapter the experimental measurements are apposed in detail, from the UV-Vis-NIR spectra received for every one of the prepared dispersions, to the graphs built on the Z-scan experimental curves. All nonlinear optical parameters deduced, are summed into analytical tables and a lengthy discussion is taking place over all these results. Results are grouped and studied from different perspectives and a bibliographical comparison is done.

Ce travail développe une approche globale du problème de l'interface entre une solution électrolytique et un semiconducteur doté d'une densité d'impuretés ionisables élevée (environ 10²º/cm³). L'épaisseur réduite de la zone de charge d'espace, l'influence de la couche d'Helmhotz et l'existence de niveaux profonds sont étudiées. Une expression très générale de la capacité de charge d'espace en présence de niveaux profonds est établie. Cette approche est appliquée au cas de l'oxyde de nickel lithiné Li_xNi_1-xO et conduit à une explication originale du comportement de l'interface.

Les composés électrochomes changent de couleur en fonction d'une tension qui leur est appliquée. La tenue en cyclage de couches minces à base de NiO, électrochrome cathodique, dépend fortement de la température et de la pression de dépôt. D'autre part la proportion de phase électrochimiquement active dépend fortement de l'épaisseur des couches. Selon le modèle proposé NiO en milieu KOH se transforme en hydroxyde de nickel Ni(OH)2 puis dans la phase de coloration en oxyhydroxyde NiOOH avant de revenir à sa forme réduite durant la phase décoloration. À la fin de ce cycle, des traces de phase colorée persistent. Nous avons développé des nouvelles méthodes numériques d'analyse des spectres d'absorption de rayons X, caractérisant la structure locale autour du nickel dans ces phases non cristallisées, afin de déterminer les concentrations des diverses espèces au cours du cycle. Aucune des méthodes habituellement pratiquées, comme la combinaison linéaire d'espèces modèles par la méthode des moindres carrés linéaire, et la méthode d'Analyse en Composantes Principales, ne sont adaptées aux cas de spectres fortement corrélés comme les oxydes-hydroxydes de nickel. Nous montrons qu'il est possible d'améliorer la méthode des moindres carrés en utilisant un algorithme original : " la méthode des Moindres Carrés Linéaire Progressive ". La base de cette méthode est fondée sur l'étude statistique des erreurs et corrélations. Ce travail a permis de valider le modèle électrochimique et d'évaluer pour la première fois la concentration en NiOOH dans la phase réduite, signature de l'irréversibilité. Seule, la présence avant cyclage de Ni(OH)2 dans les films de NiO n'a pu être expliquée

Στην παρούσα εργασία μελετήθηκε η ανάπτυξη και η επακόλουθη συμπεριφορά κατά τη θέρμανση υμενίων μεταλλικού νικελίου και χρωμίου σε μονοκρυσταλλικό οξείδιο του νικελίου, NiO(100). Οι αποθέσεις έγιναν κοντά στη θερμοκρασία δωματίου σε περιβάλλον υπερυψηλού κενού 2 x 10-10 mbar χρησιμοποιώντας πηγές θερμικής εξάχνωσης, ενώ η χημική κατάσταση των επιφανειών προσδιορίστηκε με την χρήση φασματοσκοπίας φωτοηλεκτρονίων ακτίνων-Χ (XPS) και στην περίπτωση της απόθεσης Cr επιπλέον με φασματοσκοπία σκέδασης ιόντων (ISS). Οι φασματοσκοπικές μετρήσεις έγιναν με το υπόστρωμα σε θερμοκρασίες από 550 Κ έως 680 Κ, ώστε να αυξηθεί η αγωγιμότητα και να αποφευχθεί η διαφορική φόρτιση της επιφάνειας του κρυστάλλου. Η θέρμανση μέχρι 2 μονοστρώματα (ML) νικελίου αποτεθειμένου σε NiO(100) είχε πρόσφατα βρεθεί ότι οδηγεί σε σταδιακή εξαφάνιση του Ni0, φαινόμενο που αποδόθηκε σε οξείδωσή του με οξυγόνα από το υπόστρωμα. Καθώς η ποσότητα αυτή είναι σημαντικά μεγαλύτερη από τις τυχόν διαθέσιμες ποσότητες επιφανειακού οξυγόνου (π.χ. προσροφημένα υδροξύλια) και δεν υπάρχουν ενδείξεις για την παρουσία μη στοιχειομετρικού οξυγόνου στο εσωτερικό του μονοκρυστάλλου NiO(100), επιδιώχθηκε η διερεύνηση της προέλευσης των οξυγόνων που συμμετείχαν στην οξείδωση. Προς τούτο έγιναν διαδοχικές αποθέσεις Ni0 1,6 ML, 3,8 ML και 7,5 ML, ενώ μετά από κάθε απόθεση και πριν από την επόμενη το δείγμα θερμάνθηκε μέχρι τους 940 Κ, όπου στις δύο πρώτες περιπτώσεις επήλθε πλήρης οξείδωση του Ni0 ενώ στην τρίτη η οξείδωση δεν ολοκληρώθηκε στα χρονικά περιθώρια του πειράματος. Μια κατ’ αρχήν μοντελοποίηση της κινητικής της οξείδωσης υποδεικνύει προέλευση του διαθέσιμου οξυγόνου από πηγή σταθερής συγκέντρωσης στο εσωτερικό του κρυστάλλου. Η μοντελοποίηση των εντάσεων των φωτοκορυφών XPS με βάση σωματιδιακά υμένια νικελίου σταθερού μέσου πάχους που καλύπτουν κλάσμα της επιφάνειας, οδηγεί στο συμπέρασμα ότι η θέρμανση αρχικά οδηγεί σε γρήγορη συσσωμάτωση του νικελίου, ενώ στην συνέχεια τα μεγάλα σωματίδια Ni0 που σχηματίζονται καλύπτονται αρχικά από NiO και στην συνέχεια η οξείδωση προχωρά προς τον μεταλλικό τους πυρήνα. Καθώς από το πείραμα δεν προκύπτει άλλη πληροφορία για την προέλευση των οξυγόνων, διεξάχθηκαν προσομοιώσεις Μοριακής Δυναμικής προκειμένου να διερευνηθεί η δυνατότητα του τέλειου μονοκρυστάλλου να παρέχει πλεγματικά οξυγόνα στην επιφάνεια. Οι προσομοιώσεις έγιναν στο ισόθερμο κανονικό στατιστικό σύνολο χρησιμοποιώντας τη μέθοδο του Nose πάνω σε μονοκρύσταλλο από 1728 ιόντα με εφαρμογή περιοδικών οριακών συνθηκών. Η ολοκλήρωση των εξισώσεων κίνησης έγινε με τον αλγόριθμο του Verlet, με χρονικό βήμα 2x10-15 s και χρησιμοποιήθηκε δυναμικό του τύπου σκληρών ιόντων, ενώ οι συνεισφορές Coulomb υπολογίστηκαν με την μέθοδο του Ewald. Πραγματοποιήθηκαν προσομοιώσεις για αποθέσεις με 8 ιόντα νικελίου (0,06ML), 16 ιόντα νικελίου (0,11ML) και 32 ιόντα νικελίου (0,22ML) σε θερμοκρασία 0,37Tm, με καταγραφή της συνάρτησης τοπικής πυκνότητας κατανομής των ιόντων οξυγόνου ανά 2000 βήματα. Οι προσομοιώσεις δείχνουν ότι ο τέλειος μονοκρύσταλλος μπορεί να σχηματίσει μεγάλο αριθμό οπών ιόντων οξυγόνου της τάξης του 10%, γεγονός που επιτρέπει την ερμηνεία του πειράματος, όπου περίπου 8ML Ni0 οξειδώθηκαν με οξυγόνα από το υπόστρωμα, χωρίς την ανάγκη υπόθεσης της παρουσίας άλλης πηγής μη στοιχειομετρικού οξυγόνου στο εσωτερικό του μονοκρυστάλλου. Για την μελέτη της αλληλεπίδρασης του Cr με το NiO(100), η οποία δεν είχε μελετηθεί συστηματικά μέχρι τώρα σε κλίμακα νανομετρικών υμενίων, έγιναν 4 πειράματα απόθεσης, που κατέληξαν σε 1,10 nm , 0,12 nm, 0,05 nm και 0,30 nm Cr0. Η απόθεση μεταλλικού χρωμίου σε θερμοκρασία δωματίου οδήγησε σε πλήρη κάλυψη της επιφάνειας του NiO(100), ενώ θέρμανση στους 550 Κ προκάλεσε συσσωμάτωση του χρωμίου και οξείδωσή του με παράλληλη αναγωγή του νικελίου του υποστρώματος. Περαιτέρω θερμάνσεις σε υψηλότερες θερμοκρασίες προκάλεσαν την εκ νέου οξείδωση του νικελίου. Η μοντελοποίηση των εντάσεων των φωτοκορυφών XPS με βάση σωματιδιακά υμένια χρωμίου και νικελίου δείχνει ότι το χρώμιο οξειδώνεται από κάτω προς τα πάνω και τελικά καλύπτει το μεταλλικό νικέλιο, χωρίς να αποκλείεται η ενδιάμεση ανάμειξη των δύο μετάλλων. Η μοντελοποίηση της οξείδωσης του ανηγμένου νικελίου σε μεγαλύτερη θερμοκρασία, δείχνει ότι ακολουθείται γενικά η ίδια πορεία , όπως και για απόθεση καθαρού Νi, με το οξείδιο του χρωμίου αρχικά να καλύπτει το σχηματιζόμενο NiO. Κατά την παρατεταμένη θέρμανση της διεπιφάνειας στους 940 Κ, η απόκλιση των πειραματικών σημείων από τις προβλέψεις του μοντέλου υποδεικνύει διεπιφανειακή ανάμειξη των υμενίων NiO και Cr2O3 και πιθανό σχηματισμό σπινελίου NiCr2O4, όπως αναφέρεται και στην βιβλιογραφία. Τα αποτελέσματα της φασματοσκοπίας ISS επιβεβαιώνουν σε ποιοτικό επίπεδο την ερμηνεία που αποδίδουν τα μοντέλα στις μετρήσεις XPS. / Deposition and annealing of Ni and Cr on a NiO(100) single crystal was studied using X-ray photoelectron spectroscopy (XPS) and Molecular Dynamics Simulations (MD) for the case of Ni and using XPS and Ion Scattering Spectroscopy (ISS) for the case of Cr. Depositions were carried out near room temperature in ultra high vacuum with base pressure of 2 x 10-10 mbar using Ni and Cr thermal evaporation sources . Both XP and IS spectra were taken while the sample was kept at an elevated temperature between 550K and 680K in order to avoid differential substrate charging. Annealing of up to 2 monolayers (ML) Ni deposited on NiO(100) has been reported to result in the gradual elimination of metallic Ni, attributed to oxidation via the substrate. Since the necessary quantity of oxygen is far greater than any possibly available surface oxygen (e.g. adsorbed hydroxyl species) and there is no evidence of non stoichiometric oxygen within the NiO(100) single crystal, it was decided to investigate the origin of the oxygen species involved. To that purpose, three successive depositions of Ni0 on NiO(100) were conducted, 1.6 ML 3.8 ML and 7.5 ML. After each deposition and before the next one, the sample was annealed up to 940 K resulting in the complete oxidation of the deposited Nio , with the exception of the final deposition of 7.5 ML whereby the oxidation was not completed within the time frame of the experiment. Simple kinetic modelling of the oxidation is consistent with oxygen originating from a constant concentration source within the substrate. Modelling of the XPS photoelectron intensities based on particulate films covering part of the substrate surface indicates that annealing leads initially to sintering and then to oxidation of the Ni0 particles, whereby they are covered by NiO as oxidation proceeds toward the metallic core. Since the experiment cannot provide any more information with respect to the origin of the oxygen, MD simulations where performed in order to investigate the ability of the perfect crystal to provide lattice oxygen to its surface. The Molecular Dynamics simulations were carried out in the constant temperature canonical ensemble using the Nose scheme, with a slab geometry consisting of 1728 ions and applying periodic boundary conditions. The equations of motion were integrated by means of Verlet’s algorithm and with a time step of 2 x10-15 s, whereas a rigid ion potential was adopted for the atomic interactions and the Coulombic contributions were evaluated with the use of the Ewald summation. Results are presented for depositions of 8 Ni (0.06ML), 16 Ni (0.11ML) and 32 Ni (0.22ML) ad-cations. The evolution of these systems was followed for up to 300000 time steps at a temperature corresponding to 0.37Tm , while the oxygen ions local density distribution function was recorded every 2000 time steps during each simulation run. The simulations show that the perfect crystal can successively form up to 10% of oxygen vacancies in each layer, which can explain the experimental results whereby 8ML of Ni0 where oxidized, without affecting the equivalent concentration of the available oxygen in the substrate and without having to assume any non stoichiometric oxygen inside the NiO(100) single crystal. In order to study the interaction of Cr with NiO(100), which has not been studied systematically so far in the nanometric film thickness range, four quantities of Cr0 , 10 nm, 0,12nm, 0,05 nm and 0,30 nm , were deposited. Deposition at room temperature resulted in complete coverage of the NiO(100) surface, while annealing at 550 K caused sintering and oxidation of Cr as well as reduction of NiO to Ni0 while farther annealing at higher temperatures caused the re-oxidation of the reduced Ni. Modelling of the XPS photoelectron intensities based on particulate films, indicated that Cr0 particles are oxidized from the bottom and finally cover the Ni0 film produced by reduction of the NiO(100) substrate, however the possibility that metallic Cr mixes with metallic Ni forming surface alloy during the process cannot be excluded. The XPS-based modelling of the oxidation process of the reduced Ni at higher temperatures shows that these particles are initially covered by NiO while the oxidation proceeds toward the metallic core, just as in the case of pure deposited Ni. Upon extensive annealing of the interface at 940 K, the deviation of the experimental results from the predictions of the model suggests that mixing of Cr2O3 and NiO occurs at the interface and possibly a NiCr2O4 spinel is formed, as reported in the literature. The ISS results qualitatively support the interpretation of the XPS results provided by the models.

Made available in DSpace on 2014-12-17T15:48:04Z (GMT). No. of bitstreams: 1 GeorgeHCD_DISSERT.pdf: 1498112 bytes, checksum: 47b708a57a0944475a3489af84029df2 (MD5) Previous issue date: 2012-08-06 / The academic community and software industry have shown, in recent years, substantial interest in approaches and technologies related to the area of model-driven development (MDD). At the same time, continues the relentless pursuit of industry for technologies to raise productivity and quality in the development of software products. This work aims to explore those two statements, through an experiment carried by using MDD technology and evaluation of its use on solving an actual problem under the security context of enterprise systems. By building and using a tool, a visual DSL denominated CALV3, inspired by the software factory approach: a synergy between software product line, domainspecific languages and MDD, we evaluate the gains in abstraction and productivity through a systematic case study conducted in a development team. The results and lessons learned from the evaluation of this tool within industry are the main contributions of this work / A comunidade acad?mica e a ind?stria de software t?m demonstrado, nos ?ltimos anos, bastante interesse em abordagens e tecnologias ligadas ? ?rea de desenvolvimento dirigido por modelos (MDD). Em paralelo a isto, continua a busca incessante da ind?stria por tecnologias que aumentem a produtividade e qualidade no desenvolvimento de produtos de software. Esta pesquisa visa explorar estas duas afirma??es, atrav?s de um trabalho que usa uma tecnologia MDD e avalia seu uso na resolu??o de um problema real no contexto de seguran?a de sistemas corporativos. Com a constru??o e uso de uma ferramenta, uma DSL visual denominada CALV3, inspirada na abordagem de F?bricas de Software: uma sinergia entre linha de produto de software, linguagens espec?ficas de dom?nio e MDD, avaliamos os ganhos em abstra??o e produtividade, atrav?s de um estudo de caso sistem?tico conduzido em uma equipe de desenvolvimento. Os resultados e li??es aprendidas com a avalia??o desta ferramenta no ?mbito industrial s?o uma das principais contribui??es deste trabalho

Made available in DSpace on 2014-12-17T15:54:58Z (GMT). No. of bitstreams: 1 RichellyCD_DISSERT.pdf: 2320293 bytes, checksum: 0a60ecea735c1b5c6fe1a9d05e141fe9 (MD5) Previous issue date: 2012-02-06 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Contamination by complex mixtures of various origins has been explored and studied for decades. Radon is a naturally occurring environmental contaminant that causes carcinogenic effects. These emissions can cause mutations in the lung tissue, which can initiate a carcinogenic process. Thus the dam Creek Falls, located in the municipality of Lajes Pintadas, was chosen for the development of this study, since cancer rates in the region reach 9% of the population annually, with this, the main objective of this study was evaluate the mutagenicity and toxicity of Riacho da Cachoeira damunder the influence of radon. The methodology ecotoxicological tests were performed with Ceriodaphinia dubia, as well as tests with Tradescantia pallida genotoxicologicos and Oreochromis niloticus. To understand how the population of Pintadas Slabs realizes the environment, we performed a study of environmental perception. The test results indicated that the reservoir water is toxic to test organimos exposed, found heavy metals, chloride, total and fecal coliforms as well as radon levels above the maximum allowed under Brazilian law. These results can be justified because it is so complex samples composed of different compounds that interact only with each other or causing synergistic effects. It was concluded that the dam Creek Waterfall, is contaminated with radon, as well as heavy metals, coliforms and chloride, causing toxic effects to the natural community. Thus, further studies should be performed with the human population of the region, to verify that the high rates of cancer in the population of the municipality may be linked to the presence of natural radiation. Thus, it is expected that the competent bodies that administer the municipality of Lajes Pintadas take reasonable steps to minimize risks and ensure the health of the community that still makes use of the weir / A contamina??o por misturas complexas de origens diversas vem sendo explorada e estudada por d?cadas. O rad?nio ? um contaminante ambiental de origem natural, que provoca efeitos carcinog?nicos. Estas emiss?es podem levar as muta??es no tecido do pulm?o, que podem iniciar um processo carcinog?nico. Assim o a?ude Riacho da Cachoeira, localizado no munic?pio de Lajes Pintadas, foi escolhido para o desenvolvimento do presente estudo, j? que h? altas taxas de c?ncer na regi?o que chegam a 9% da popula??o, anualmente, com isso, o objetivo principal do presente estudo foi avaliar a mutagenicidade e toxicidade do a?ude Riacho da Cachoeira sob a influ?ncia do Rad?nio. Como metodologia, foram realizados ensaios ecotoxicologicos com Ceriodaphinia dubia, assim como ensaios genotoxicologicos com Tradescantia pallida e Oreochromis niloticus. Para entender como a popula??o de Lajes Pintadas percebe o meio ambiente, foi realizado um estudo de percep??o ambiental. Os resultados dos ensaios indicaram que a ?gua do a?ude ? toxica aos organimos-teste expostos, foram encontrados metais pesados, cloreto, coliformes totais e fecais assim como os n?veis de rad?nio acima dos limites m?ximos permitidos segundo a legisla??o brasileira. Os resultados encontrados podem ser justificados pelo fato de se tratar de amostras complexas constitu?das assim de diferentes compostos que interagem s? ou entre si causando efeitos sin?rgicos. Concluiu-se que o a?ude Riacho da Cachoeira, est? contaminado com rad?nio, assim como por metais pesados, coliformes e cloreto, causando efeitos toxicol?gicos ? comunidade natural. Assim, novos estudos devem ser realizados com a popula??o humana da regi?o, para verificar se os altos ?ndices de c?ncer na popula??o do munic?pio podem estar ligados a presen?a da radia??o natural. Desta forma, espera-se que os ?rg?os competentes que administram o munic?pio de Lajes Pintadas tomem medidas cab?veis para assegurar e minimizar os riscos a sa?de da comunidade que ainda faz uso do a?ude

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-12-12T18:02:43Z No. of bitstreams: 1 GilvanPereiraDeFigueredo_TESE.pdf: 4395902 bytes, checksum: dcc65d04331c39ac75781ca0d55044db (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-12-13T18:29:41Z (GMT) No. of bitstreams: 1 GilvanPereiraDeFigueredo_TESE.pdf: 4395902 bytes, checksum: dcc65d04331c39ac75781ca0d55044db (MD5) / Made available in DSpace on 2017-12-13T18:29:41Z (GMT). No. of bitstreams: 1 GilvanPereiraDeFigueredo_TESE.pdf: 4395902 bytes, checksum: dcc65d04331c39ac75781ca0d55044db (MD5) Previous issue date: 2017-08-11 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Os materiais cer?micos apresentam diversas aplica??es, principalmente por sua versatilidade e propriedades. V?rias metodologias foram consolidadas para a s?ntese destes materiais, mas algumas desvantagens limitam sua aplicabilidade em cat?lise. Assim, h? muitas pesquisas concentradas no estudo de m?todos de s?ntese de catalisadores e suportes catal?ticos que sejam simples, r?pidos, de baixo custo, ecol?gicos e que produzam materiais adequados. Nos ?ltimos anos algumas rotas alternativas de s?ntese t?m atra?do bastante aten??o, mas a obten??o do espin?lio MgAl2O4 pelo m?todo da gelatina e da perovskita LaAlO3 via rea??o de combust?o assistida por microondas tem sido pouco explorada. O MgAl2O4 ? bastante utilizado na reforma a seco do metano (RSM), mas estudos de RSM usando LaAlO3 como suporte s?o muito limitados. Neste contexto, os objetivos deste trabalho foram: sintetizar MgAl2O4 usando gelatina como precursor org?nico; preparar a perovskita LaAlO3 via rea??o de combust?o assistida por microondas; e, comparar o desempenho em reforma a seco do metano de dois catalisadores preparados com n?quel suportado no LaAlO3 e na ?-Al2O3 comercial. Pelo m?todo da gelatina foi poss?vel obter MgAl2O4 puro, nanom?trico e com cristalinidade de at? 90,40%. Um aumento brusco no tamanho dos cristalitos foi observado para temperatura de calcina??o acima de 900 ?C. Na s?ntese por microondas, a perovskita LaAlO3 monof?sica e nanom?trica foi obtida. Os perfis de RTP-H2 mostram que as vac?ncias de oxig?nio presentes na superf?cie da perovskita exerceram um forte efeito sobre a temperatura de redu??o e a redutibilidade das nanopart?culas de NiO, resultando em fraca intera??o Ni0/LaAlO3. Os resultados dos testes de 10 h com GHSV de 18 L g-1 h-1 mostram que o catalisador Ni/LaAlO3 ? 7,8 e 11,5 % mais est?vel do que o Ni/?-Al2O3 nas convers?es de CH4 e CO2, respectivamente. A maior estabilidade e atividade do Ni/LaAlO3 est? diretamente relacionada ? presen?a de NiO (3,38 %p) ap?s a ativa??o, que promoveu a forma??o de nanotubos de carbono (NTC), aumentando a dispers?o da fase met?lica. Mesmo em condi??es severas de ativa??o e rea??o (alta GHSV), como no teste a longo prazo (20 h), o catalisador Ni/LaAlO3 revelou um rendimento em H2 de 37,2% a mais que o Ni/?-Al2O3. As an?lises por Microscopia Eletr?nica de Transmiss?o (MET) revelam que o catalisador Ni/?-Al2O3 desativou por sinteriza??o. Assim, a presen?a de defeitos estruturais e de superf?cies ricas em vac?ncias de oxig?nio tornam a perovskita LaAlO3 um potencial suporte para aplica??o em processos de reforma catal?tica do metano. / Ceramic materials have several applications, mainly due to their versatility and properties. Several methodologies have been consolidated for the synthesis of these materials, but some disadvantages limit their applicability in catalysis. Thus, much research is concentrated on the study of catalyst synthesis methods that are simple, fast, low cost, ecofriendly and produce suitable materials. In recent years, some alternative synthesis routes have attracted great attention, however the obtainment of MgAl2O4 spinel by the gelatin method and perovskite LaAlO3 via microwave assisted combustion method has been little explored. MgAl2O4 is widely used in the dry reforming of methane (DRM), but DRM studies using LaAlO3 as support are very limited. In this context, the aims of this work were: to synthesize MgAl2O4 using gelatin as an organic precursor; to prepare LaAlO3 perovskite via microwave assisted combustion reaction; and to compare the methane dry reforming performance of two nickel catalysts supported on LaAlO3 and commercial ?-Al2O3. By the gelatin method it was possible to obtain pure and nano-sized MgAl2O4 with crystallinity of up to 90.40%. An abrupt increase in crystallite size was observed for calcination temperatures above 900 ?C. In the microwave synthesis, a monophasic and nano-sized LaAlO3 perovskite was obtained. The TPR-H2 profiles show that the oxygen vacancies present on the perovskite surface exerted a strong effect on the reduction temperature and the reducibility of NiO nanoparticles, resulting in poor Ni0/LaAlO3 interaction. The results of the 10 h catalytic tests with GHSV of 18 L g-1 h-1 show that the Ni/LaAlO3 catalyst is 7.8 and 11.5% more stable than Ni/?-Al2O3 for CH4 and CO2 conversions, respectively. The higher stability and activity of Ni/LaAlO3 is directly related to the presence of NiO (3.38% p) after activation, which promoted the formation of carbon nanotubes (CNT), increasing the dispersion of the metal phase. Even under severe activation and reaction conditions (high GHSV) as in the long-term test (20 h), Ni/LaAlO3 catalyst showed a H2 yield of 37.2% higher than Ni/?-Al2O3. Transmission Electron Microscopy (MET) analyzes revealed that the Ni/?-Al2O3 catalyst deactivated by sintering. Thus, the presence of structural defects and surfaces rich in oxygen vacancies makes the LaAlO3 perovskite a potential support for application in processes of catalytic reforming of methane.