Dissertations / Theses on the topic 'Hydroxydes à base de Co'

Le développement d'électrocatalyseurs efficaces pour la réaction de libération d'oxygène (OER) est important pour améliorer l'efficacité globale du processus d'électrolyse de l'eau. Les oxydes / hydroxydes de métaux de transition présentent une activité et une stabilité raisonnables lorsqu’utilisés dans un milieu alcalin. Ils ont le potentiel de remplacer les oxydes à base d'Ir et de Ru. Comprendre la réaction d’OER pour les oxydes / hydroxydes de métaux de transition dans les électrolytes alcalins aide à la conception d'électrocatalyseurs peu coûteux et très efficaces. Avec trois travaux différents sur les oxydes / hydroxydes à base de Co, cette thèse approfondit la compréhension des propriétés de surface des matériaux et des propriétés interfaciales sur la cinétique de la réaction d’OER. Tout d'abord, la substitution au fer régule par exemple la configuration des cations métalliques dans LaCoO3. Cela ajuste la covalence de la liaison oxygène 2p – métal 3d et améliore les performances. Deuxièmement, la substitution au Ni dans ZnCo2O4 modifie la position relative du centre de la bande O 2p et du centre de la bande métallique dans un environnement octahédrique MOh. Cela modifie la stabilité et la possibilité pour l'oxygène du réseau de participer à la réaction de dégagement d’oxygène. Enfin, en étudiant les séries La1-xSrxCoO3, CoOOH et CoOOH contenant Fe, l'impact de l'électrolyte sur les paramètres de la cinétique de réaction a été exploré. Avec une meilleure compréhension de la façon dont les propriétés des matériaux et l'environnement dynamique influencent l'activité et le mécanisme des OER, nous pouvons obtenir des catalyseurs de OER plus efficaces pour une meilleure infrastructure énergétique
The development of efficient electrocatalysts to lower the overpotential of oxygen evolution reaction (OER) is of fundamental importance in improving the overall efficiency of fuel production by water electrolysis. Among a plethora of catalysts being studied on, transition metal oxides / hydroxides that exhibit reasonable activity and stability in alkaline electrolyte have been identified as catalysts to potentially overpass the activity of expensive Ir- and Ru- based oxides. Understanding the OER for transition metal oxides / hydroxides in alkaline electrolytes paves the way for better design of low cost and highly efficient electrocatalysts. This dissertation, with three different work on Co-based oxides / hydroxides, studies and deepens the understanding of the bulk properties, surface properties of materials and interfacial properties on OER. Firstly, with Fe substitution, it addresses tuning the eg configuration of metal cations in LaCoO3 where adjusting the metal 3d oxygen 2p covalency can bring benefits to the OER performance. Secondly, with Ni substitution in ZnCo2O4, it demonstrates a change in relative position of O p-band and MOh d-band centre which induces a change in stability as well as the possibility for lattice oxygen to participate in the OER. Finally, with La1-xSrxCoO3 series, CoOOH and Fe-containing CoOOH as examples, the impact of the electrolyte has been explored by the study of reaction kinetics parameters. With a better understanding of how material properties and dynamic environment influence the OER activity and mechanism, we can obtain more efficient OER catalysts for better energy infrastructure

Les polymères accroissent les risques d'incendies, du fait de leurs natures inflammables. Ce risque est réduit par ajout de retardateur de flamme (FR). Les FR halogénés présentent l'inconvénient de libérer des fumées opaques et toxiques. La réglementation internationale tente de limiter leur utilisation et favorise le développement de charges nùnérales comme l'hydroxyde de magnésium (MGH) car il dégage peu de gaz toxiques et/ou corrosifs. Le but de ce travail réside dans la caractérisation et l'optimisation de formulations à base de copolymère éthylène-propylène (EPc) et de MGH en terme de tenue au feu et de propriétés mécaniques pour le remplacement des câbles automobile en PVC. Afin d'anticiper les changements législatifs, FL-,%,WMAG a développé une synthèse hydrotherinale de MGH permettant le recyclage d'une partie des réactifs, limitant ainsi, le coût de production et les rejets dans l'environnement. Le remplacement du PVC par des EPc fortement chargés en MGH (60,Vo wlw pour la même tenue au feu) génère une perte des propriétés mécaniques. U modification de surface du MGH par l'ac. Stéarique améliore la compatibilité entre le MGH (polaire) et l'EPc (apolaire) et donc les propriétés mécaniques (tenue aux chocs). L'analyse de surface du MGII enrobé par l'ac. Stéarique montre la présence d'un sel mixte, ce qui montre le caractère réactif de l'enrobage. Les tests au calorimètre à cône montrent une baisse du CO, du C02, du volume de fumée et la diminution de la quantité de chaleur produite par rapport aux MGH références. Dans le cas Flainemag, le MgO issu de la déshydratation du MGH adsorbe le carbone provenant de la décomposition de l'EPc (limitation fumée) mais, contrairement aux autres MGH, ne catalyse pas l'oxydation du carbone, limitant la production de gaz. Les formulations références libèrent donc plus de COIC02 et une quantité de chaleur supplémentaire en raison de l'oxydation exothermique du carbone.

La gestion actuelle des effluents liquides contenant des métaux lourds passe par des traitements qui conduisent à l'obtention de boues d'hydroxydes métalliques dont la mise en décharge pose un problème de cout et de capacité d'accueil des sites de stockage. La recherche de nouvelles voies de traitement de ces déchets minéraux, principalement ceux charges en fer et en zinc, doit permettre, par des opérations d'inertage chimique et de valorisation matière, de limiter voir d'éviter la mise en décharge. Leur principe repose sur une sélectivité de la réactivité chimique des espèces métalliques présentes. La première voie envisagée correspond à une recherche de stabilisation chimique sous forme de sulfure insoluble des formes minéralogiques du zinc présents dans les boues d'hydroxydes métalliques en mettant à profit la réactivité de solutions de polysulfures. Le procédé appliqué à des boues synthétiques puis industrielles démontre que le déchet peut être inerte à température ambiante et pour des temps de traitement compatibles avec les impératifs industriels. Un second procédé permet la détoxication du déchet par extraction des éléments polluants et le recyclage des produits obtenus en vue d'une valorisation matière. L'utilisation de ligands minéraux comme les thiosulfates et de ligands organiques de la famille des polyéthylène-polyamines permet l'obtention de réactifs lixiviants conjuguant effet de pH et de complexation. La solubilité importante des formes ZnO et Zn(OH)2 dans ces milieux permet d'envisager un traitement similaire sur les boues d'hydroxydes. Une étude cinétique de la lixiviation montre qu'il est possible d'extraire dans des conditions économiques et technologiques acceptables la quasi-totalité du zinc présent dans le solide sans entrainement de fer. La dernière voie étudiée propose de mener des opérations de précipitation sélective des cations métalliques présents dans l'effluent, en amont des traitements physico-chimiques classiques. Les propriétés oxydoréductrices et sulfurantes des polysulfures permettent de précipiter, dans des solutions mixtes de fer-zinc-nickel, le sulfure de zinc ou de nickel sans entrainer la précipitation du fer. Ce type de protocole appliqué à des effluents industriels conduit à la récupération des sulfures des métaux lourds avant la précipitation des hydroxydes de fer. Les résidus sulfures ainsi que les hydroxydes de fer pourraient être réorientés vers des filières de valorisation ou de recyclage
The treatment process of liquid waste containing heavy metals by metal hydroxyde precipitation is the most commonly employed. At the present time, the sludge are an ultimate waste wich are stored in landfilling. In a first time, the objective is the inertizing of heavy metal like zinc. The principle of transformation of leaching forms containing heavy metal in metallic sulfides slightly soluble appears like a way to explore. The present work confirms that a sulfurization of mineralogic form of zinc containing in sludge is faisable from polysulfides solutions. The performance of this process is confirmed in the case of real sample stemming from industry. In a second time, we studied the possibility of the selective extraction method by leaching of zinc-bearing phases. Chemical leaching of ZnO and Zn(OH)2 with a solution of inorganic ligand as thiosulphate and organic ligand such as polyethylene-polyamine appeared to be an efficient method. This detoxication method has been validated using these reagents on the real hydroxyde sludge stemming from industry. The result confirms that this treatment led to the extraction of the potential polluting zinc fraction contained in the waste. The last method studied the possibility of selective precipitation of heavy metal contained in liquid waste before classical physicochemical treatment. The reducing power of polysulfides and the formation possibility of metallic sulfides slighthly soluble bring about the selective precipitation of zinc sulfide and nickel in mixte solution of fer-zinc-nickel. The treatment of liquid waste containing heavy metal is possible. The final-products are a sulfur-metallic sulfur heavy metal mixture and an hydroxie ferric cake. The use of this products as new materials in different industries is actually under study

Des hydroxydes doubles lamellaires (hdl) multicomposants, contenant les cations co 2 +, ni 2 +, mg 2 + et al 3 +, obtenus par coprecipitation a ph constant, en controlant les parametres de synthese, ont ete utilises comme precurseurs de catalyseurs d'hydrogenation. L'etude de l'activation montre que les stabilites thermiques des echantillons sont fonction de leur teneur en magnesium et de leur densite de charge dans les feuillets. Les phases cristallines obtenues apres calcination sont un melange de phases oxydes mixtes et spinelles. Les reductibilites dependent largement de leur composition. De ce fait, le cobalt se reduit dans deux types d'especes bien identifiables, alors que le profil de reduction attribuable au nickel traduit une plus large distribution d'especes. Les proprietes acido-basiques et metalliques des catalyseurs sont reliees a leurs activite dans l'hydrogenation de l'acetonitrile. Ils presentent une selectivite elevee pour la formation de l'amine primaire, et permettent dans le meilleur des cas d'atteindre 96% d'ethylamine a 98% de conversion. L'etude comparative des divers solides ne met en evidence aucune correlation nette entre leur acido-basicite et la selectivite. Par contre, l'association du nickel et du cobalt induit un effet de synergie, attribue a une dilution des ensembles nickel par le cobalt, ce qui limite la formation des produits secondaires de condensation.

Cette thèse présente un travail sur l'obtention d'aérogels d'HDL par séchage en conditions CO2 supercritique et l'élaboration de nouveaux bionanocomposites formés par la coprécipitation d'hydroxydes doubles lamellaire (HDL) dans l'espace confiné des billes d'alginate. Grâce à la combinaison d'une synthèse par coprécipitation Flash et d'un séchage en conditions supercritiques au CO2, des aérogels d'HDL possédant des surfaces spécifiques élevées sont élaborés. Parallèlement, l'alginate est utilisé comme une matrice de confinement pour la précipitation inorganique d'HDL. D'une part, les billes d'alginate sont synthétisées par complexation des ions Ca2+ et la coprécipitation des phases HDL s'effectue en réalisant des imprégnations successives de réactifs. D'autre part, des billes d'alginate sont formées directement en présence des cations divalents (Mg2+, Ni2++, Co2+, ...) et des cations des métaux trivalents (Al3+), précurseurs des composés inorganiques. La coprécipitation des HDL se produit dans ce cas lors d'une étape d'imprégnation dans une solution d'hydroxyde de sodium. Tous les composés HDL, aérogels ou encore bionanocomposites sont caractérisés en détail par DRX, spectroscopie IR, MEB/MET, adsorption/désorption d'azote et ATG/DTG, pour obtenir un meilleur aperçu de la structure des particules, de leur taille et de leur morphologie. Des études menées sur l'adsorption de la trypsine pour les aérogels ou encore sur les performances d'électrodes modifiées HDL-alginate ont permis de montrer qu'il était possible d'améliorer les performances des HDL en augmenter leur porosité et en élaborant des bionanocomposites.

O objetivo deste trabalho foi a obtenção de nanocompósitos de poli(hidroxibutirato-co-hidroxivalerato) (PHBV) com diferentes filossilicatos – montmorilonita (OMMT) e haloisita (HNT), na proporção de 1, 3 e 5% em massa, através de processamento no estado fundido. A influência do tipo e teor de nanopartícula, das condições de processamento e da modificação com organosilanos sobre a morfologia e propriedades térmicas e mecânicas dos nanocompósitos foi avaliada. A cristalização dos nanocompósitos apresentou dependência no tipo de nanopartícula: a OMMT dificultou a formação dos esferulitos, enquanto que a HNT promoveu a formação de estruturas mais regulares e orientadas, com maior temperatura de fusão. Os nanocompósitos preparados com teores mais elevados de nanopartículas e em maior intensidade de cisalhamento apresentaram melhor dispersão, o que foi refletido em um aumento nas propriedades mecânicas e de barreira. As nanopartículas modificadas apresentaram diferentes resultados, dependendo do grau de interação do grupo funcional com o polímero. Interações mais fracas promoveram aumento na ductilidade e tenacidade dos nanocompósitos. Por outro lado, a degradação da matriz na presença de sais de amônio quaternário ou de aminosilanos influenciou negativamente o desempenho térmico e mecânico dos nanocompósitos. O conjunto de resultados revelou o potencial da haloisita comparada à montmorilonita. Os nanocompósitos com HNT não modificada apresentaram melhores características de processamento e balanço de propriedades, com aumento no alongamento na ruptura e resistência ao impacto, mantendo elevada rigidez, além de uma diminuição de 93% nos valores de permeabilidade ao oxigênio.
In this work, poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposites were prepared by melt intercalation process using 1, 3 and 5 wt% of different phyllosilicates – montmorillonite (OMMT) and halloysite (HNT). The effect of the clay type and content, as well as the processing conditions and the modification with organosilanes on the morphology and thermal and mechanical properties of the nanocomposites were evaluated. The crystallization characteristics of the nanocomposites were dependent on the clay type: OMMT prevented the formation of the spherulites, while HNT promoted the formation of a regular and oriented structure with higher melting temperature. The nanocomposites prepared with high clay content and high shear intensity presented a better dispersion, which resulted in an improvement in the mechanical properties and barrier property. The modified nanoparticles presented different results, depending on its degree of interaction with the polymer matrix. For weak interactions, it was observed an increase in ductility and toughness of the nanocomposites. The degradation of the polymer matrix in the presence of aminosilanes or quaternary ammonium salts negatively influenced the thermal and mechanical performance of the nanocomposites. The set of results revealed the potential of halloysite in comparison to montmorillonite. The nanocomposites with unmodified HNT presented the best set of properties, with improved processing characteristics, strain at break and impact strength while maintaining a high stiffness, and a reduction of 93% in the oxygen permeability.

Coating structure was mainly composed of α-fcp- and β-fcc-cobalt. Selected temperature interval for coating formation, according to XRD analysis, allowed us to form inter-metalloid compounds of CoxCry-type cobalt with chromium. Subsequent melting of a surface layer by a plasma jet resulted to doping of the coating surface by Mo atoms (compounds) from doping electrodes. It was demonstrated that essential improvement of servicing characteristics was due phase transformations induced by high-temperature plasma jet, Mo doping, redistribution of elements in the coating, and appearance of micro- and nano-grained structure, as well as decreasing porosity due to repeated melting. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20651

Les matériaux hydroxydes doubles lamellaires (HDL) sont une classe d'argiles anioniques synthétiques dont la structure est basée sur celle du brucite Mg(OH)2 dans lesquelles une partie des cations métalliques divalents sont été remplacés par des ions trivalents donnant ainsi des feuillets chargés positive. Cette charge est équilibrée par l'intercalation d'anions dans la région interlamellaire hydratée. Les identités et les rapports des cations di- et trivalents et l'anion interlamellaire peuvent être varié sur une large gamme, donnant lieu à une large classe de matériaux isostructurales. Le matériau d’origine de cette classe est l’hydrotalcite (HT) et les HDL sont par conséquent également connus comme des matériaux de type hydrotalcite. Bien que les caractéristiques de base de la structure soient bien comprises, des aspects structurels détaillés ont fait l'objet de certaine controverse dans la littérature afin de maîtriser leurs propriétés et leurs applications potentielles. Dans ce travail de thèse nous avons retenu deux types de HDL MgAl et ZnAl qui ont été largement introduits dans diverses applications, tels que la sorption des molécules d'intérêt biologique (enzyme et médicament) et l'élaboration d'électrodes. La spécificité de ce travail repose sur l’immobilisation d’une enzyme modèle, la lactate déshydrogénase dans ces deux matrices ainsi qu’un médicament anti-bactérien, la berbérine, afin d’étudier les interactions entre ces deux biomolécules et la phase HDL introduite et de répondre à leurs exigences d'applications dans le domaine médical. Dans un second temps nous avons tenté d’étudier les deux phases mentionnées de plus en plus fine en termes de structure, morphologie et profil électrochimique en vue de les employer en tant que matériaux d’électrode pour le développement de biopile
DHs are a class of synthetic anionic clays whose structure is based on brucite-like layers Mg(OH)2 inwhich some of the divalent cations have been replaced by trivalent ions giving positively-charged sheets.This charge is balanced by intercalation of anions in the hydrated interlayer regions. The identities andratios of the di- and trivalent cations and the interlayer anion may be varied over a wide range, giving rise toa large class of isostructural materials. The parent material of this class is the naturally occurring mineralhydrotalcite and LDHs are consequently also known as hydrotalcite-like materials. Although the basicfeatures of the structure are well understood, detailed structural aspects have been the subject of somecontroversy in the literature. In this thesis, we have selected two types of LDH, MgAl and ZnAl, which havebeen widely introduced in various applications, such as sorption of molecules of biological interest (enzymeand drug) and the development of electrodes. The specificity of this work lies on the immobilization of amodel enzyme, lactate dehydrogenase in both matrices as well as an anti-bacterial drug, berberine, inorder to study the interactions between these two biomolecules and the introduced LDH phase and tobetter address their challenges of applications in the medical field. Second, we have tried to study the twophases mentioned above more and more accurately in terms of structure, morphology and electrochemicalprofile in order to use them as electrode materials for microbial fuel cell device

Parmi les matériaux de base utilisés en microélectronique, le SOI (silicium sur isolant), fabriqué par la technologie Smart CutTM, a réussi à tirer son épingle du jeu. Cette technologie enchaîne plusieurs étapes clés, dont l'une est l'implantation ionique d'hydrogène. Pour des raisons économiques, l'utilisation d'hydrogène à forte dose a été remplacée par une co-implantation hélium / hydrogène. La co-implantation est un " système " complexe, récent et donc relativement peu compris. Nous avons proposé un scénario décrivant la transformation des platelets en microfissures puis en onde de fracture. Les populations de défauts croissent en moyenne selon un mûrissement d'Ostwald, mais une faible partie des défauts interagit par coalescence. Nous avons trouvé un critère d'interaction basé sur la taille des défauts et la distance les séparant. Nous avons testé et validé la spectroscopie Raman comme technique permettant d'identifier les complexes hydrogénés mis en jeu après implantation et en cours de recuit. Nous avons ainsi pu vérifier l'étape de nucléation des platelets dans plusieurs conditions d'implantation. Nous avons montré que la redistribution de l'hélium est essentiellement due à la diffusion et au piégeage de l'hélium sur les platelets générées par l'implantation d'hydrogène, à l'aide d'un modèle physique simple. La réduction de dose spectaculaire de la co-implantation par rapport à l'implantation standard d'hydrogène provient majoritairement du fait que l'hélium est un gaz monoatomique, contrairement au dihydrogène. Nous avons également montré que le retard sur les cinétiques de fracture avec l'ordre d'implantation inversé est un effet purement balistique
Among the different substrates used in the microelectronic industry, the SOI (Silicon On Insulator), manufactured by Smart CutTM technology, is used more and more. This technology involves several process steps, one of which is the ion implantation of hydrogen. For cost-effective reasons, the co-implantation of helium / hydrogen has replaced the hydrogen only step. The co-implantation is a " complex " and recent system and it is not well understood. We have suggested a global picture that describes the defect formation process: some of the platelets are transformed into microcracks and then result in fracture wave. Both populations of defects evolve in average following an Ostwald ripening, but few of the defects interact by coalescence. We have found a criterion of interaction based on the size of the defects and the distance between them. We have tested and approved the Raman spectroscopy as a technique allowing the identification of the hydrogenated complexes playing a role after implant and during the annealing. We have then checked the nucleation step of platelets for several implantation conditions. We have shown that the helium redistribution is mainly due to diffusion and gettering of helium on hydrogenated platelets, thanks to a simple physical model. The drastic dose reduction in co-implantation as compared to hydrogen only case, comes mainly from the fact that helium is a monatomic gas, as oppose to hydrogen gas. We have also shown that the delay in fracture kinetics with the reverse order of implantation is a pure ballistic effect

The abrasive wear of a WC12Co/NiCrAl two layer coating, single layer WC12Co, and single layer 50%(WC12Co)50%(NiCr) on the as deposited and melted conditions was studied. The tests were performed at two different conditions, called mild wearand severe wear. Samples of the substrate material, AISI 1020 grade steel, were also studied for comparison. The surface of the materials was characterized before and after the wear tests using topographic parameters obtained by stylus profilometry. A Modified Plasticity Index was created to evaluate the nature of the contact betweenthe surfaces and the abrasive media. The lowest wear rates were found on the duplex coating on both severity conditions. The results show that the 50%(WC12Co)50%(NiCr) coatings have lower wear resistance than the WC12Co single layer and duplex coatings on both severityconditions. However, their wear rate was significantly lower than that of the steel. Although the 50%(WC12Co)50%(NiCr) coatings proved not to be the best choice in terms of wear resistance, they are resistant enough to produce good results on wear applications. The topographic parameters helped on the characterization of the wear mechanisms.The Modified Plasticity Index, defined as a function both of the surface characteristics and of the mechanical properties of the materials, can be used to compare the wear behavior of different surfaces/coatings.
Estudou-se o desgaste abrasivo dos recobrimentos duplex WC12Co/NiCrAl monocamada WC12Co e monocamada 50%(WC12Co)50%(NiCr) como depositado e fundido. Os testes foram realizados em duas condições de severidade que foramdenominadas desgaste brando e desgaste severo. Amostras do material do substrato, aço AISI 1020, também foram desgastadas para fins de comparação. Também foi feita uma caracterização superficial dos materiais antes e depois do desgaste por meio de parâmetros de topografia extraídos das superfícies por perfilometria. Um Índice dePlasticidade Modificado foi definido para avaliar a natureza do contato entre o meio abrasivo e a superfície. As menores taxas de desgaste foram observadas no recobrimento duplex em ambas ascondições. Os resultados obtidos mostram que os recobrimentos50%(WC12Co)50%(NiCr) apresentam menor resistência ao desgaste do que os recobrimentos Duplex e monocamada WC12Co nas duas condições estudadas. Apesar disso, a taxa de desgaste desses materiais foi muitas vezes inferior à do aço, de modo que, apesar de não constituírem a melhor opção para resistir ao desgaste, podem serutilizados com sucesso na presença desse tipo de solicitação.O estudo dos parâmetros de topografia contribuiu para a caracterização dos mecanismo de desgaste atuantes. Foi comprovado que o Índice de Plasticidade, função tanto das características da superfície quanto das propriedades dos materiais, pode ser utilizado para comparar o comportamento de desgaste de materiais diferentes.

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Universidade Federal de Sao Carlos
Ir/Al2O3 samples were prepared to evaluate the influence of the particle size of the metal in the preferential oxidation of CO reaction. Initially, samples with different amounts of iridium were prepared in an attempt to get different particle sizes. Samples containing 1, 2, 6 and 10 % Ir/Al2O3 were prepared. The samples were prepared via dry impregnation, from alcoholic solutions of the salt precursor and calcined at a temperature of 400 °C. The -Al2O3 support was calcined at 550 °C. The catalytic tests were carried out using a flow rate of 100 ml/min of a mixture containing 1% O2, 1% CO, 45% H2 and balance in He. The results of XRD of these samples showed no characteristic peaks of iridium and the metal dispersions were very similar, raising the possibility that even with the increased loading of iridium samples showed no significant differences in their structure. After realize catalytic tests using the same density of active sites, it was found that the structure of the samples was very similar and the different results of activity and selectivity were due to the different densities of active sites. In order to obtain samples with different structural properties, was fixed in 4% the iridium concentration on the catalysts and was varied the calcination temperature of the catalysts (400, 550 and 750 °C) and the support (550 and 750 °C) and was studied the influence of calcination temperature of the catalyst as well the support. Results of XRD and hydrogen chemisorption showed large differences in particle size and metal dispersion. The total flow of the catalytic tests was reduced to 50 mL/min, maintaining the concentrations of the gases. DRIFTS spectra confirmed the structural differences due to the increase of calcination temperature of catalysts, showing a large decrease in the interaction between CO/metal. The results of the catalytic tests showed that by increasing the calcination temperature of the catalysts there is a loss of activity but these catalysts were more selective. A strong influence of the calcination temperature of the supports in the activity and selectivity of the catalysts was also observed. The results show that the PROX reaction is very sensitive to catalyst structure.
Foram preparadas amostras de Ir/Al2O3 a fim de avaliar a influência do tamanho de partícula do metal na PROX-CO. Inicialmente foram preparadas amostras com diferentes teores de irídio, na tentativa de se obter diferentes tamanhos de partículas. Foram preparadas amostras com teor de irídio de 1, 2, 6 e 10% Ir/Al2O3. As amostras foram preparadas via impregnação seca, a partir de soluções alcoólicas do sal precursor, e calcinadas em temperatura de 400 °C. O suporte -Al2O3 foi calcinado em 550 °C. Os testes catalíticos foram realizados utilizando um fluxo de 100 mL/min de uma mistura contendo 1% O2, 1% CO, 45% H2 e balanço em He. Os resultados de DRX destas amostras não apresentaram picos característicos de irídio e as dispersões metálicas foram muito semelhantes, levantando a hipótese de que mesmo com o aumento da carga de irídio as amostras não apresentavam diferenças significativas em sua estrutura. Após serem realizados testes catalíticos utilizando a mesma densidade de sítios ativos, foi constatado que a estrutura das amostras era muito semelhante e os diferentes resultados de atividade e seletividade eram devidos as diferentes densidades de sítios ativos. Para que se obtivessem amostras com propriedades estruturais diferentes, foi fixada em 4% a concentração de irídio nos catalisadores e variada a temperatura de calcinação dos catalisadores (400, 550 e 750 °C) e do suporte (550 e 750 °C) e foi estudada a influência da temperatura de calcinação tanto do catalisador quanto do suporte. Resultados de DRX e quimissorção de hidrogênio mostraram grandes diferenças de tamanho de partícula e dispersão metálica. O fluxo total dos testes catalíticos foi reduzido para 50 mL/min, mantendo as concentrações dos gases. Os espectros de DRIFTS comprovaram as diferenças estruturais devidas ao aumento de temperatura de calcinação dos catalisadores, mostrando uma grande queda na interação entre CO/metal. O resultado dos testes catalíticos mostrou que com o aumento da temperatura de calcinação dos catalisadores há uma perda de atividade, porém estes catalisadores se mostraram mais seletivos. Também foi observada uma forte influência da temperatura de calcinação dos suportes na atividade e seletividade dos catalisadores. Os resultados mostram que a reação PROX é muito sensível a estrutura dos catalisadores.

Notre dépendance à l'égard des combustibles fossiles et la diminution des ressources pétrolières nous imposent la recherche de sources renouvelables d'énergie et de produits chimiques. La synthèse Fischer-Tropsch permet de répondre à la demande en carburants propres et renouvelables grâce à l'utilisation de gaz de synthèse issu de la biomasse. L'objectif de ce travail est de contribuer à la compréhension du mécanisme de l'hydrogénation du CO sur des catalyseurs au cobalt et à l'identification du site actif par des études spectroscopiques DRIFTS operando. Ce système permet d'observer les différentes espèces adsorbées à la surface du catalyseur pendant la réaction : CO pontés et linéaires, formiates, carboxylates et hydrocarbures. Nos travaux ont montré qu'une fraction des formiates dits « rapides» peut expliquer la formation du méthanol dans nos conditions de réaction. L'ajout dans le mélange H2+CO d'un élément minéral typique de la biomasse, le chlore sous forme de trichloréthylène, a révélé que, l'activité diminuait. La bande des CO pontés étant la plus impactée et se déplaçant vers les hauts nombres d'onde, l'effet du chlore a été notamment associé à un effet électronique sur le cobalt. L'adsorption du chlore étant réversible, nous avons également étudié l'effet de l'étain. Ce métal n'adsorbe pas le CO dans nos conditions et peut s'adsorber à la surface du cobalt. L'étain empoisonne sélectivement la formation des CO pontés et limite fortement la chimisorption de l'hydrogène. Une relation linéaire entre la vitesse de formation des produits et la proportion de CO pontés est observée, révélant l'importance des CO pontés pour la réaction d'hydrogénation du CO
Our dependence on fossil fuels and the decrease of oil resources warrant the search for renewable energy sources and chemicals. Fischer-Tropsch synthesis enables meeting the requirements for cleaner and renewable fuels through the use of syngas obtained from biomass.The objective of this work was to contribute to the understanding of the mechanism of CO hydrogenation on cobalt-based catalysts and the identification of the active site by operando DRIFT spectroscopy. Different species were adsorbed on the surface of the catalyst under reaction conditions: bridged and linear CO, formates, carboxylates and hydrocarbons. Our resutls shows that so-called “fast formate” can account for the formation of methanol under our reaction conditions. The study of a typical biomass element, chlorine, revealed that the activity decreased under trichloroethylene,. The CO bridged band being the most affected band and shifting to higher wavenumber, the chlorine effect was partly associated with an electronic effect on cobalt. Chlorine adsorption being reversible, tin poisoning was also studied. This metal does not adsorb CO under our conditions. Tin addition to cobalt selectively poisons bridged CO and greatly limits the chemisorption of hydrogen. A linear relationship between the rate of formation of products and the proportion of CO bridged is observed, highlighting the importance of CO bridged

The increased introduction of renewable energy puts pressure on power producers to level peak loads, since the electrical generation from renewable sources more often than not is of intermittent nature. Good base load properties i.e. smooth and even power production over time is one of the most important characteristic a renewable source can show since that implies that less regulating power is required. This project examines the base load properties of wave power and compares them to the base load properties of wind power. This is done based on wave data from Islandsberg on the Swedish west coast and on wind and wave data recorded at Horns rev, a large wind power farm of the west coast of Jutland, Denmark. The wave energy converter (WEC) investigated is a point absorber type WEC, similar to the device developed at Uppsala University / Seabased AB. The results indicate that electrical generation from waves is less fluctuating than generation from winds. Further, wind and wave power co-production would benefit from the time delay in electric wave generation due to that the wind-generated waves continue, after the wind velocities slow down and the wind power output decreases. However, the results also show that Horns rev (and Islandsberg) have rather moderate wave climates and wind-wave co-production would be better balanced inmore energetic wave climates (deeper and/or more exposed waters).

L’acide oxalique est un ligand mis en avant pour la récupération quantitative des actinides séparés des produits de fission. En particulier, la co-précipitation oxalique facilite l’incorporation des actinides mineurs dans des matériaux céramique dédiés à leur transmutation grâce à la formation contrôlée de composés oxalate mixtes, précurseurs des solutions solides oxyde souhaitées. Les méthodes de croissance cristalline existantes n’étant pas adaptables à la chimie du système actinide-oxalate et aux conditions de manipulation en boîte-à-gants, plusieurs méthodes de synthèse originales ont été conçues puis développées sur les lanthanides et les actinides légers (uranium, thorium). Quatre méthodes originales, basées sur des stratégies de mise en contact lente des réactifs, ont ainsi été optimisées. Après développement sur les simulants, elles ont été adaptées aux spécificités (notamment redox) des actinides plus lourds tels le plutonium ou l’américium. Elles ont permis la synthèse de nombreux monocristaux d’oxalates d’actinide et d’oxalates mixtes An1(IV)-An2(III) mais aussi An1(IV)-An2(IV). Finalement, les premières caractérisations structurales poussées de ces composés par DRX sur monocristal, EXAFS ou micro-RAMAN permettent d’acquérir des informations structurales indispensables à l’enrichissement de la base de données structurales relativement pauvre concernant les oxalates d’actinides. Cette dernière est pourtant indispensable à une meilleure compréhension des futurs cycles du combustible actuellement à l’étude
Oxalic acid is a well-known reagent to recover actinides thanks to the very low solubility of An(IV) and An(III) oxalate compounds in acidic solution. Therefore, considering mixed-oxide fuel or considering minor actinides incorporation in ceramic fuel materials for transmutation, oxalic co-conversion is convenient to synthesize mixed oxalate compounds, precursors of oxide solid solutions. As the existing oxalate single crystal syntheses are not adaptable to the actinide-oxalate chemistry or to their manipulation constrains in gloves box, several original crystal growth methods were developed. They were first validate and optimized on lanthanides and uranium before the application to transuranium elements. The advanced investigations allow to better understand the syntheses and to define optimized chemical conditions to promote crystal growth. These new crystal growth methods were then applied to a large number of mixed An1(IV)-An2(III) or An1(IV)-An2(IV) systems and lead to the formation of the first original mixed An1(IV)-An2(III) and An1(IV)-An2(IV) oxalate single crystals. Finally thanks to the first thorough structural characterizations of these compounds, single crystal X-ray diffraction, EXAFS or micro-RAMAN, the particularly weak oxalate-actinide compounds structural database is enriched, which is essential for future studied nuclear fuel cycles

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Universidade Federal de Sao Carlos
The emissions of the nitrogen oxides (NOx) must be hardly reduced in the next years. The catalytic reduction of NO with CO is one of the possible processes with potential to be able to transform those oxides in N2. In that process, supported noble metals have been the most used, however, their low stability in the presence of water steam or SO2, have led to develop studies to overcome those limitations. Perovkites type catalysts or transition metal oxides supported in a variety of support show activity in this reaction. Nevertheless, no adequate information about the activity of metal oxides supported on zeolites is found in the literature. In this context, the present work was focused to prepare and evaluate between 150°C and 500°C, Cu, Co or Fe containing catalysts dispersed on USY (Si/Al=3,4) or ZSM-5 (Si/Al=12,8) zeolites in the reduction of NO with CO and in the oxidation of CO to CO2. The oxide activity was also compared with that of the respective metal cations located in charge compensation sites. The catalysts were prepared by ion exchange or impregnation and characterized by AAS, XRD, DRS-UV and H2-TPR. Conversion data of NO to N2 on USY and ZSM-5 zeolites containing predominantly Cu2+ or Co2+ cations in exchangeable sites were more active when located on ZSM-5 zeolite (MFI structure), with the Cu2+ cations being more active. On the other hand, Cu, Co or Fe oxides supported on USY or ZSM-5 were more active than cations of considered metals in exchangeable sites, with conversion being dependent on the type and metal content and the type of zeolite. Among the studied metal oxides, the Fe one was the most active and selective. However the presence of O2 or water steam in the feed inhibited the NO reduction with CO on Fe oxide, which was attributed to the deactivation of the active sites by the water steam and the CO direct oxidation by O2 occurring preferentially than CO oxidation via NO reduction. This result gives evidence of the water steam leads to the deactivation of the metallic active sites and O2 favors the direct oxidation of CO to CO2 in detriment of its oxidation by NO reduction. The NO conversion was not significantly affected by the presence of SO2 in the feed (40 ppm).
A emissão de óxidos de nitrogênio (NOx) deverá ser no curto prazo reduzida drasticamente. Dentre os processos com potencial para a conversão desses óxidos a N2 tem-se a redução catalítica de NO com CO. Nesse processo, metais nobres suportados têm sido os mais empregados, entretanto, sua baixa estabilidade na presença de vapor de água e de SO2, levam à necessidade de se realizar estudos que superem essas limitações. Catalisadores tipo perovskita ou de óxidos de metais de transição depositados sobre diversos suportes apresentam atividade nessa reação. Entretanto, pouca informação encontra-se disponível relacionada à atividade desses óxidos suportados em zeólitas. Dentro desse contexto, este trabalho teve como objetivo preparar catalisadores à base de Cu, Co ou Fe dispersos em zeólita USY (Si/Al=3,4) ou ZSM-5 (Si/Al=12,8) e avaliá-los na redução de NO a N2 e oxidação de CO a CO2 no intervalo entre 150°C e 500°C. A atividade desses óxidos foi comparada com cátions dos respectivos metais em sítios de compensação de carga. Os catalisadores foram preparados por troca iônica ou impregnação e caracterizados por EAA, DRX, ERD-UV e RTP-H2. Os resultados de conversão de NO a N2 sobre as zeólitas USY ou ZSM-5 com predominância de cátions Cu2+ e Co2+ compensando carga, mostraram que essas espécies foram mais ativas quando presentes na zeólita ZSM-5 (estrutura MFI), sendo os cátions de Cu mais ativos. Por outro lado, óxidos de Cu, Co ou Fe depositados sobre a USY ou ZSM-5 mostraramse mais ativos que cátions desses metais em sítios de compensação, com a conversão sendo dependente do tipo e do teor de metal e do tipo de zeólita. Dentre os óxidos estudados, o óxido de Fe foi o mais ativo e seletivo a N2, porém a presença de O2 ou vapor de água inibiram fortemente a redução de NO com CO sobre óxido de Fe. Esse resultado evidencia que o vapor de água desativa os sítios metálicos ativos e o O2 favorece a oxidação direta do CO a CO2 em detrimento da sua oxidação via redução de NO. A conversão de NO não foi afetada significantemente na presença de SO2 (40 ppm).

Orientador: Eliana Aparecida de Rezende Duek
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Polímero sintético biodegradável tem encontrado aplicações em diferentes áreas da medicina, especialmente em dispositivos ortopédicos. A principal vantagem desses materiais comparado com os materiais metálicos é pelo fato dos implantes biodegradáveis não necessitarem de uma segunda cirurgia para remover o dispositivo, resultando em baixo custo e menor risco para o paciente. Pinos de poli(L-co-D,L ácido lático-co-trimetileno carbonato), PLDLA-TMC, contendo 30% de TMC foram obtidos e caracterizados através do estudo in vitro e in vivo visando aplicação como dispositivos para fratura. Pinos de 2,5 mm de diâmetro foram obtidos por fusão do polímero e imersos em solução tampão fosfato, pH 7,4 para se estudar o processo de degradação in vitro e implantados na tíbia de ratos Wistars para avaliar a formação óssea após 15, 60, 90, 120 e 150 dias. Os resultados obtidos a partir do estudo da degradação in vitro de pinos PLDLA-co-TMC mostraram que as propriedades térmicas, mecânicas e morfológicas se mantêm praticamente inalteradas até 90 dias em solução tampão fosfato, especialmente temperatura de transição vítrea, módulo de Young, tensão máxima no alongamento e perda de massa, apesar da nítida variação da massa molar já no início do processo de degradação. Esses resultados corroboram com os do estudo in vivo, cujos resultados mostraram a ocorrência de neoformação óssea nos tempos iniciais, principalmente 60 e 90 dias, sendo que o grupo implante, no geral, apresentou uma formação óssea mais madura e organizada, com menor presença de fibrose do que o grupo controle. Esse conjunto de resultados indica que o material apresenta potencial para aplicado como dispositivo para recuperação de lesões ósseas, em situações onde seja adequada a permanência do implante durante longo período de tempo e ainda com a vantagem da degradação do mesmo, evitando sua posterior retirada
Abstract: Biodegradable synthetic polymers have found application in different areas of medicine, especially in orthopedics devices. The main advantage of these biomaterials compared to the metals materials is the fact of the use of biodegradable implants avoid the/necessity of a second surgery to removal the device, resulting in a lower costs and minor risks for the patient. Poly(L-co-D,L lactic acid-co-trimethylene carbonate), PLDLA-TMC, pins, content 30% of TMC were obtained and characterized by in vitro and in vivo study aiming application as fracture devices. Pins with 2,5mm of diameter were obtained by melting of polymer and immersed into the buffer phosphate solution, pH 7,4 to study in vitro degradation process and implanted in Wistars rats tibia to evaluate the bone formation after 15, 60, 90, 120 e 150 days. Results obtained from the in vitro degradation of the PLDLA-co-TMC pins showed that thermal, mechanical and morphological properties remained without alterations until 90 days, considering the glass transition temperature, Young modulus, maximum tension at the elongation and loss of mass. In spite of this, variation of molar mass was nitid since the initial of the degradation process. These results are in accordance with in vivo study, which showed the occurrence of bone neoformation in the initial times of implant, mainly after 60 and 90 days and presence of bone formation more organized and mature with minor presence of fibrosis than control group. These results are indicative that this material presents a potential to be applied as a device for recuperation of bone lesion in a situation where it is necessary the permanence of the implant for a long period of time and so with the advantage of the degradation, avoiding it to be removed
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

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

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Cookie is a product consumed internationally for all social classes, obtained by mixing flour(s), starch(s) with other ingredients, undergo the process of kneading and cooking, fermented or not. The present study aimed to use of co-products from rice and soybeans, the cookies donut type production for celiac patients, also adding more value commodities (rice bran, grits and okara) that in most industries are discarded. First, we performed experiments with mixtures (Simplex) and evaluated physical and chemical analysis of the experimental and commercial biscuit, biscuit being chosen for the sensory analysis that came closest commercial biscuit. Upon sensory evaluation, only one formulation was evaluated for 10 months during the storage test. The results showed that the biscuit developed with okara and rice bran showed no significant difference (p> 0.05), with the commercial biscuit, as to the questions of appearance, color, flavor and aroma; the moisture, ash, lipids and energy value of both biscuits, were significantly influenced by the factors type interactions of biscuit and storage time (p <0.05), whereas protein and carbohydrates suffered influence, significantly, only the time factor alone (p <0.05); in relation to protein digestibility, there was a significant difference (p <0.05) between the two product reviews (experimental Cookie - 71.64% and commercial biscuit - 73.24%), which does not mean that the cookie does not have good experimental in vitro digestibility. Therefore, the experimental cookie, using the co-products of rice and soybean was feasible from a technological and nutritional standpoint, being a product that caters to the public in patients with celiac disease.
O biscoito é um produto consumido, internacionalmente, por todas as classes sociais, obtido pela mistura de farinha(s), amido(s) e/ou fécula(s), com outros ingredientes, submetidos a processos de amassamento e cocção, fermentados ou não. O presente trabalho teve como objetivo, o aproveitamento dos co-produtos do arroz e da soja, na elaboração de biscoitos tipo rosquinha para pacientes celíacos, agregando, também, maior valor as matérias primas (farelo de arroz, quirera e okara) que, na maioria das indústrias, são descartadas. Primeiramente, foi realizado delineamento de misturas (Simplex) e avaliadas análises físicas e químicas do biscoito experimental e comercial, sendo o biscoito escolhido para a análise sensorial os que mais se aproximaram do biscoito comercial. Após análise sensorial, apenas uma formulação foi avaliada, durante 10 meses, no decorrer do ensaio de armazenamento. Os resultados obtidos mostraram que o biscoito desenvolvido com okara e farelo de arroz não mostraram diferença significativa (p>0,05), com o biscoito comercial, quanto aos quesitos aparência, cor, sabor e aroma; os teores de umidade, cinzas, lipídeos e valor energético, de ambos os biscoitos, foram influenciados, significativamente, pelas interações dos fatores tipo de biscoito e tempo de armazenamento (p < 0,05), enquanto que o teor de proteínas e carboidratos sofreu influência, significativa, somente do fator isolado tempo (p < 0,05); em relação a digestibilidade protéica, houve diferença significativa (p<0,05) entre os dois produtos avaliados (biscoito experimental – 71,64% e biscoito comercial – 73,24%), o que não significa que o biscoito experimental não possua boa digestibilidade in vitro. Portanto, o biscoito experimental, utilizando os co-produtos do arroz e da soja, foi viável do ponto de vista tecnológico e nutricional, sendo um produto que atende ao público de portadores de doença celíaca.

Neste trabalho sintetizou-se catalisadores ternários a base de Ni, Co e Fe para eletro-oxidação de glicerol suportados em carbono por diferente métodos de síntese. Os resultado de EDX mostraram que foi possível obter uma relação próxima aos 20 % de carga metálica pretendida assim como uma relação próxima das proporções atômicas dos metais (1:1:1), ou seja, (Ni33Co33Fe33/C). Os difratogramas dos catalisadores mostraram perfis de materiais amorfos, salvo por alguns catalisadores que exibiram picos característicos de fase metálica. Observouse que o melhor desempenho frente a eletro-oxidação de glicerol foi o do catalisador 7 - Ni32,33Co42,07Fe25,61/C preparado via refluxo em álcool (etanol) por 12 horas, tanto na voltametria cíclica quanto na cronoamperometria. No experimento de FTIR in situ coletados a 1500 mV vs ERH para a eletro-oxidação de glicerol, observou-se bandas características do composto formato dando indicativo de que este pode vir a ser o produto majoritário durante a eletro-oxidação do glicerol. O teste em célula unitária mostrou que o catalisador monometálico a base de Ni sobressaiu-se sobre os demais com densidade de potência máximo obtido na célula a combustível em aproximadamente 0,4 mW cm-2, resultado esse divergente dos resultados observados nos teste voltamétricos e cronoamperométricos frente à eletrooxidação do glicerol. Tal fato pode ter acontecido em virtude de problemas técnicos e/ou experimentais do funcionamento da célula unitária.
This work was synthesized in the ternary catalysts based on Ni, Co and Fe for electrooxidation of glycerol supported on carbon by different methods of synthesis. The result of EDX showed that it was possible to obtain a close relationship to 20% metal load intended as a close relationship of the atomic proportions of metal (1:1:1), or (Ni33Co33Fe33/C). The XRD patterns of the catalysts showed profiles of amorphous materials, except for a few catalysts that exhibited characteristic peaks of metallic phase. It was observed that the best performance compared to electro-oxidation glycerol was the catalyst of 7 - Ni32,33Co42,07Fe25,61/C prepared via refluxing in alcohol (ethanol) for 12 hours at both techniques, the cyclic voltammetry as chronoamperometry. In-situ FTIR experiments listed at 1500 mV vs RHE for electro-oxidation of glycerol, characteristic bands observed for the compound of format giving an indication that this is the major product during the electrooxidation of glycerol. The test showed that the unit cell base monometallic catalyst Ni towered over the other with maximum power density obtained from the fuel cell by approximately 0.4 mW cm-2, a result of the divergent results observed in the test and voltammetric chronoamperometric front of the electro-oxidation of glycerol. This may have happened because of technical problems and / or experimental operation of the unit cell.

Tradicionalmente, no tratamento de feridas graves o antimicrobiano tópico deve ser aplicado uma a duas vezes ao dia na área lesada para reduzir as infecções. No entanto, os pacientes geralmente sofrem desconforto com a aplicação de drogas tópicas e com a troca de curativos. Nesse contexto, o desenvolvimento de sistemas curativos biodegradáveis contendo fármaco antimicrobiano são fundamentais para a promoção de ações terapêuticas, reduzindo as infecções causadas por microrganismos e podendo substituir os curativos convencionas que não possuem polímeros biodegradáveis em sua composição. Para ir de encontro com essa necessidade, filmes de PBAT e PBAT/gentamicina foram preparados por meio de duas abordagens. Na primeira abordagem filmes de PBAT obtidos por casting foram funcionalizados por radiação UV durante 90 minutos na presença de O2 atmosférico para posterior inserção de gentamicina na superfície através de soluções tampões contendo EDC e gentamicina. A superfície das amostras foi analisada pelo WCA, FTIR-ATR e XPS. A análise antimicrobiana dos filmes também foi realizada. Os resultados para os filmes de PBAT por casting mostram que o tempo de irradiação produziu superfícies altamente hidrofílicas com grupos oxigenados enxertados na superfície do polímero (C=O e C-OH). A análise antimicrobiana indicou que a gentamicina não ligou covalentemente com o PBAT, porém observou-se a presença de nitrogênio na superfície das amostras pela análise de XPS Na segunda abordagem foram preparadas fibras de PBAT e PBAT/gentamicina a partir da eletrofiação. As soluções utilizadas no processo de eletrofiação foram preparadas com diferentes concentrações de gentamicina e passaram por análises de condutividade e viscosidade. As fibras de PBAT e PBAT/gentamicina foram caracterizadas quanto a suas propriedades físico-químicas, morfológicas, térmicas, antimicrobianas e biológicas. Nos resultados obtidos para as fibras de PBAT e PBAT/gentamicina observou-se que não houve mudança nos espectros após a mistura dos materiais, uma vez que as bandas de absorção foram preservadas e não houve o aparecimento de novos picos. A presença da gentamicina modificou a morfologia das amostras, diminuindo o diâmetro das fibras. O grau de intumescimento foi alterado com o acréscimo de gentamicina e houve modificação da morfologia das fibras após 48 horas de imersão em PBS, porém as fibras mantiveram-se presentes. A gentamicina aumentou o grau de molhabilidade das fibras PBAT. As fibras de PBAT/gentamicina possuem atividade antimicrobiana frente às cepas de E. coli e não apresentaram citotoxicidadede acordo com o padrão ISO 10993-5. Estes resultados reforçam que o PBAT pode ser usado como um sistema curativo com incorporação de fármaco, mostrando ser uma alternativa interessante de curativo/adesivo para uso tópico.
Traditionally in the treatment of serious wounds, topical antimicrobial should be applied 1–2 times daily to the injured area to reduce infections. However, patients often suffer from discomfort with the application of topical drugs and with the exchange of dressings. In this context, the development of biodegradable curative systems containing antimicrobial drug are fundamental for the promotion of therapeutic actions, reducing the infections caused by microorganisms and being able to substitute conventional dressings that there aren’t biodegradable polymers in their composition. To meet this need, PBAT and PBAT/gentamicin films were prepared using two approaches. In the first approach PBAT films obtained by casting were functionalized by UV radiation for 90 minutes in the presence of atmospheric O2 for subsequent insertion of gentamicin on the surface through buffer solutions containing EDC and gentamicin. The surface of the samples was analyzed by the WCA, FTIR-ATR and XPS. Antimicrobial analysis of the films was also performed. The results for the PBAT films by casting show that the irradiation time produced highly hydrophilic surfaces with oxygenated groups grafted onto the polymer surface (C=O and C-OH). Antimicrobial analysis indicated that gentamycin did not bind covalently with PBAT, but nitrogen was observed on the surface of the samples by XPS analysis In the second approach, PBAT and PBAT/gentamicin fibers were prepared from the electrospun. The solutions used in the electrospun process were prepared with different concentrations of gentamicin and underwent conductivity and viscosity analyzes. The PBAT and PBAT/gentamicin fibers were characterized as their physical-chemical, morphological, thermal, antimicrobial and biological properties. In the results obtained for the PBAT and PBAT/gentamicin fibers, it was observed that there was no change in the spectra after the materials were mixed, since the absorption bands were preserved and there were no new peaks. The presence of gentamicin modified the morphology of the samples, reducing the diameter of the fibers. The degree of swelling was altered with the addition of gentamicin and there was a change in the morphology of the fibers after 48 hours of immersion in PBS, but the fibers remained present. Gentamicin increased the degree of wettability of PBAT fibers. PBAT/gentamicin fibers have antimicrobial activity against E. coli strains and did not present cytotoxicity according to ISO 10993-5 standard. These results reinforce that PBAT can be used as a curative system with drug incorporation, proving to be an interesting dressing/adhesive alternative for topical use.

Ocean acidification is predicted to have adverse effects on the physiologies of marine organisms, particularly those that produce calcified structures. Extracellular homeostasis is considered to be critical to mediating the effects of ocean acidification. Due to their low metabolic rates and weak ability to regulate ion exchange, sea urchins are thought to be particularly weak acid-base regulators. Recent findings showing species-specific capacities for extracellular pH regulation however suggest that species currently exposed to natural CO₂ elevations, such as upwelling events, may have a higher capacity tolerate elevated CO₂. The sea urchin Parechinus angulosus currently experiences natural CO₂ variations within the Benguela upwelling system and is therefore predicted to possess the capacity to compensate moderate acid-base disturbances. Urchins were submitted to control (8.0), intermediate (7.7) and low (7.4) seawater pH treatments for 14 days to investigate the capacity to regulate extracellular acid-base status. Extracellular pH changes induced by exposure to intermediate (pH 7.7) seawater acidification were fully compensated through the accumulation of approximately 2.0 mmol l-1 of bicarbonate. The bicarbonate accumulation was only sufficient to partially compensate extracellular acid-base status during exposure to low (7.4) seawater pH. Results from acute (24 hour) exposure to low (7.4) seawater pH reveal that bicarbonate accumulation, despite being evident within 24 hours, is not sufficient to compensate extracellular pH. This study provides further support that sea urchins exposed to natural CO₂ variability possess a limited capacity to regulate extracellular acid-base disturbances. P.angulosus may therefore already be adapted to deal with a moderate reduction in seawater pH to 7.7, but lacks the iono-regulatory capacity to accumulate sufficient bicarbonate to deal with a reduction of seawater pH to 7.3. Long-term studies are needed to assess the role of acid-base regulation as a mediator of broader physiological tolerance to ocean acidification, and its consequences at the level of the whole organism.

L’optimisation de la morphologie de la couche active est primordiale pour l’augmentation des rendements des cellules solaires photovoltaïques organiques. Nous avons montré l’influence du ratio de matériaux donneur (P3HT) et accepteur (PCBM) d’électrons ainsi que de la masse molaire du P3HT sur la morphologie de la couche active. Afin de contrôler la séparation de phases entre les matériaux donneur et accepteur d’électrons, il est possible d’utiliser des copolymères à blocs afin d’aider la compatibilisation entre le P3HT et le PCBM. Nous avons choisi de synthétiser des copolymères à blocs P3HT-b-polystyrène et des P3HT-b-polyisoprène présentant une certaine compatibilité avec les matériaux de la partie active. L’ajout optimisé de P3HT-b-polyisoprène permet une augmentation de 30% des rendements et de 90% de durée de vie des cellules solaires
Active layer morphology optimization is fundamental to achieve high efficiency in organic photovoltaic solar cells. We showed the influence of the donor (P3HT) and acceptor (PCBM) material ratio and the impact of the P3HT molecular weight on the active layer morphology. We demonstrated the possibility of using well-designed block copolymers to help P3HT and PCBM compatibilization and to control their phase separation. We chose to synthesize P3HT-b-polystyrene and P3HT-b-polyisoprene for which each block is compatible with the active materials. Optimal addition of P3HT-b-polyisoprene enables to get a 30%-improved efficiency and a 90%-enhanced lifetime of the solar cells

Oxidative transformation is one of the fundamental reactions occurring in organic chemistry and is the basis of many synthetic processes. This ia an area of an ongoing research work addressed both to the synthetic application and to the understanding of the mechanism involved in these processes, whose interest include reactions occurring in biological system also. In enzymes, as in artificial catalysts, the presence of metals in high oxidation state allow the activation of hydrogen peroxide (H2O2) and alkyl hydroperoxides (RO2H) and the subsequent oxidation of different organic substrates. Both in enzymes and in artificial systems the sourranding environment of the peroxidic reactive species is of great importance. The ligands bounded to a metal center, such as proteins or molecules from synthesis, are able to increase not only the stability and reactivity, but also the stereoselectivity of the metal. However, there are numerous examples in the literature of how the reactivity, stability and stereoselectivity of cataytic synthetic processes catalyzed by polidentate catalysts may be largely influenced by the presence of additives or monodentate ligands able to bind to the metal center. The influence that polidentate ligands or monodentate ligands may exsert on the reactivity of several catalytic systems is part of the topics covered in the first chapter of this thesis. In particular, we have addressed our attention to catalytic oxidative processes which are accelerated after the bind of ligands both poly- and monodentate. Numerous examples from recent literature have been reported. They are divided into two classes of phenomena: the "ligand accelerated catalysis (LAC) and the co-ligand accelerated catalysis (LAC-CO ). In LAC, as defined by Sharpless, the addition of a polydentate chiral ligand induces the genaration, towards ligand exchange, of a new chiral metallic complex characterized by an increased reactivity. In CO-LAC, the addition of a chiral or achiral monodentate ligand allows the modification of the reactivity of the original metal complex without the occurrency of a ligand exchange. In Chapter 2 we have focused our attention on the reactivity of a polyhedral oligomeric silsesquioxane trisilanolate vanadium(V) complex towards oxidation reactions. This catalyst, at room temeperature and in the presence of cumyl hydroperoxide as the terminal oxidant is efficient in oxygen transfer processes towards sulfides, tertiary amine and secondary amine. Sulfoxidations and N-oxidations have been carried out yielding the corrisponding products in good yields. The addition of a Lewis base as a co-ligand can markedly affect reactivity, stability, chemo- and stereo-selectivity. A proposal for the intermolecular activation, using Gutmann analysis supported by MP2/TZVP calculations, has been presented. In Chapter 3 catalytic sulfoxidations, using cumylhydroperoxide as primary oxidant, has been tested in a series of eight aminotriphenolate d0 metals complexes [Sc(III), Ti(IV), Zr(IV), Hf(IV), V(V), Nb(V), Ta(V), Mo(VI)]. The reactivity and selectivity properties ,both in presence and in absence of a strong Lewis Base (dimethylhexyl-N-oxide) as co-ligand, has been determined experimentally. The experimental values have been correlated with the Sanderson value of electronegativity. MP2/LANL2DZ theoretical calculations on model complexes have furnished more insights on the characteristics of the reactive peroxo specie. The experimentals combined with the theoretical calculations have offered the possibility to propose a general mechanism for the peroxide activation and reactivity. The study described in Chapter 4 pertains to V(V)-oxo amine triphenolate complexes as functional and structural model of vanadium haloperoxidases: their trigonal bypiramidal geometry emulates the one found in the enzymes and their ability to catalyse efficiently sulfoxidations as well as chlorination and bromination of trimethoxybenzene reflects the properties of the enzyme. In particular, sulfoxidations using hydrogen peroxide as terminal oxidant are performaed in quantitative yields and high selectivities ( catalyst loading down to 0.01%, TONs up to 9900, TOF up to 8000 h-1), while in the second case TONs up to 1260 and TOF up to 220 h-1 are achieved with a acatlyst loading down to 0.05%. In Chapter 5 some synthtic method for the preparation of a new fluorinated incompletely condensed polyhedral oligomeric silsesquioxane suitable to be immobilized on polymeric fluorous membranes or in addition able to be dissolved in fluorous solvents have been reported.
La trasformazione ossidativa di gruppi funzionali costituisce una delle reazioni fondamentali della chimica organica ed è alla base di moltissimi processi sintetici. Si tratta di un settore che è oggetto di un continuo lavoro di ricerca, indirizzato sia alla risoluzione di problemi sintetico-applicativi che alla comprensione dei meccanismi che operano in tali processi il cui interesse è così vasto da includere reazioni che avvengono anche in sistemi biologici. Negli enzimi, così come nei catalizzatori artificiali, la presenza di metalli in elevato stato di ossidazione permette l'attivazione di acqua ossigenata (H2O2) e di idroperossidi alchilici (RO2H) consentendo l’ossidazione di diversi substrati organici. Sia negli enzimi che nei sistemi artificiali particolare importanza riveste l’intorno chimico della specie reattiva metalloperossidica responsabile del trasferimento di ossigeno. I leganti al centro metallico, siano essi di natura proteica o costituiti da molecole di sintesi, sono in grado di aumentare non solo la stabilità e la reattività ma anche la capacità di stereoselezione del centro reattivo. Tuttavia, si trovano in letteratura numerosi esempi di come la reattività, la stabilità e la stereoselezione di processi sintetici catalizzati da complessi con leganti polidentati vengano ampiamente influenzati anche dalla presenza di additivi, o leganti monodentati per lo più basici, in seguito alla loro interazione con il metallo. L’influenza che leganti polidentati e co-leganti monodentati possono avere sulla reattività di numerosi sistemi catalitici è parte degli argomenti trattati nel primo capitolo di questa tesi di dottorato. In particolare abbiamo voluto indirizzare la nostra attenzione verso processi reattivi, soprattutto di tipo ossidativo, che vengono accelerati in seguito all’azione sia di leganti polidentati che di co-leganti monodentati. I numerosi esempi che sono stati riportati su questo argomento, tratti dalla recente letteratura, sono stati suddivisi all’interno di due classi di fenomeni: la “ligand accelerated catalysis” (LAC) e la “co-ligand accelerated catalysis” (CO-LAC). Nella LAC, secondo la definizione di Sharpless, l’aggiunta di un legante chirale polidentato induce la formazione, tramite scambio di legante, di un nuovo complesso metallico dotato di una aumentata reattività che spesso si accompagna anche ad una aumentata stereoselettività. Nella CO-LAC invece, l’aggiunta di un legante monodentato chirale o achirale, induce una modificazione della reattività del complesso metallico senza che vi sia scambio di legante. Numerosi esempi di CO-LAC prevedono l’utilizzo di leganti monodentati basici. Durante questo dottorato, abbiamo potuto constatare che il processo di trasferimento di ossigeno verso il metil p-tolil solfuro catalizzato da un complesso polisilosanico di V(V) recanti sostituenti iso-butilici in presenza di CHP come ossidante primario viene accelerato, anche di 24 volte, a seguito dell’aggiunta di basi di Lewis in quantità confrontabili con quelle del catalizzatore. Nel Capitolo 2 i dati sperimentali riportati evidenziano l’esistenza di una corrispondenza tra accelerazione osservata del processo e natura elettron donatrice della base di Lewis usata. Più elettron ricca è la base di Lewis maggiore è la reattività del sistema e, probabilmente a causa delle migliori capacità coordinanti del co-legante, minore è la quantità di base di Lewis necessaria per avere l’effetto massimo. Calcoli computazionali condotti hanno dimostrato come la coordinazione di basi di Lewis al vanadio inducano variazioni di distribuzione elettronica con aumento di densità elettronica all’ossigeno della specie reattiva metalloperossidica coinvolto nel trasferimento di ossigeno e contemporanea diminuzione della stessa a livello del centro metallico con conseguente stabilizzazione dell’intermedio reattivo. Lo studio sugli effetti delle basi di Lewis in processi di trasferimento di ossigeno a solfuri organici è stato esteso anche verso un’altra classe di leganti ossia le trifenolammine. Nel Capitolo 3 sono stati investigati processi catalitici di ossidazione del metil p-tolil solfuro per mezzo di cumilidroperossido come ossidante primario in presenza di otto complessi ammino tri-fenolati di metalli d0 [Sc(III), Ti(IV), Zr(IV), Hf(IV), V(V), Nb(V), Ta(V), Mo(VI)]. La reattività e la selettività di questi processi, sia in assenza che in presenza di una base di Lewis forte come il dimetilesil-N-ossido è stata determinata sperimentalmente. I dati sperimentali ottenuti sono stati correlati con i valori di elettronegatività di Sanderson e tramite studi teorici sono state tratte delle delucidazioni sulle caratteristiche della specie reattiva metalloperossidica. I dati sperimentali raccolti e i calcoli teorici ci hanno permesso di proporre un meccanismo generale per spiegare l’attivazione della specie perossidica e la sua reattività. Nel Capitolo 4 sono descritti i complessi ammino tri-fenolati di ossovanadio(V) come modelli funzionali e strutturali di aloperossidasi, grazie alla loro geometria trigonale bipiramidale e alla loro abilità nel catalizzare efficacemente sia le solfossidazioni così come la bromurazione e la clorurazione del trimetossibenzene. In particolare, nell’ossidazione di solfuri, usando perossido d’idrogeno come ossidante primario, sono state ottenute con rese quantitative in prodotto con alta chemoselettività, anche in presenza dello 0.01% di catalizzatore, con TON fino a 9900 e TOF fino a 8000 h-1. Nel caso della bromurazione si sono ottenuti TON pari a 1260 e TOF fino a 220 h-1 usando fino allo 0.05% di catalizzatore. Nel Capitolo 5 viene riportata una serie di strategie di sintesi per la formazione di un nuovo legante trisilanolico polisilossanico recante lunghe catene perfluorurate come sostituenti.

Mestrado em Gestão e Estratégia Industrial
O modelo de inovação aberta consiste na abertura, ao exterior, das actividades internas de inovação, permitindo a colaboração de outras organizações, na qualidade de parceiras¬ e, por outro lado, a transferência de conhecimentos internos para estas. Este modelo surgiu para colmatar as limitações do processo de inovação fechada, onde cada empresa inovava sozinha. Pela absorção dos fluxos externos de conhecimento e do desenvolvimento conjunto, os parceiros alcançam um maior retorno da I&D interna resultante da alavancagem das capacidades de ambos. Praticar a inovação aberta, num país como Portugal, é um desafio ainda não abraçado por muitas empresas. Esta dissertação pretende analisar a EDP Inovação (EDPI), a qual desenvolve as actividades de coordenação da inovação tecnológica, dos estudos de engenharia e das actividades laboratoriais, de todo o grupo EDP. Para realizar essa análise, a metodologia utilizada foi o estudo de caso. Com recurso a entrevistas, a profissionais da empresa e, a dados secundários foi possível concluir que esta empresa pratica o modelo de inovação aberta, através das parcerias que desenvolve com outras empresas e universidades, com vista à execução de projectos. A EDPI criou uma plataforma de co-criação acessível, a todos, que potencia a inovação no grupo. Com relação à transferência de conhecimento, interno excedentário, esta ainda não é realizada para entidades externas. Apesar dos riscos da partilha da I&D interna, as parcerias são benéficas, pois enriquecem a base de conhecimentos, das empresas da rede.
The model of open innovation consists in opening our innovative activities, allowing collaboration with other organizations, as partners and, on the other hand, transferring internal knowledge to them. This model has emerged to face the limitations of closed innovation process, where each company innovated alone. Utilize external knowledge flows and co-creation provides, to partners, a greater return of internal R&D by leveraging the capacities of both. Practicing open innovation, in a country like Portugal, is a challenge not yet embraced by many companies. This thesis aims to analyze EDP Inovação (EDPI), which develops the coordination of technological innovation, the engineering studies and laboratory activities, of the whole group EDP. For this study, the methodology used was the case study. Using interviews, with professionals of the company and secondary data, was possible to conclude that this company practices open innovation model, which develops through partnerships with other companies and universities, to implement the projects. The EDPI created a platform "co-creation", accessible to everyone, which encourages innovation in the group. With relation to the transfer, of the excess internal knowledge, this is still not performed for external organizations. Despite the risks of sharing internal R&D, partnerships are beneficial because enrich the knowledge base of the network.

Copolímeros à base de estireno e anidrido maleico (SMA) são materiais sintéticos comercialmente disponíveis, obtidos pela reação dos dois monômeros citados em diferentes proporções, resultando em materiais versáteis, e disponíveis em diferentes graus de massas e porcentagens molares de anidrido maleico. São considerados polímeros funcionais devido à reatividade do grupamento anidrido maleico presente na cadeia polimérica. Por este motivo, esses materiais possuem vasta gama de aplicações, e elevada importância em diversas áreas, principalmente por terem baixa toxicidade, boa resistência térmica e boa estabilidade dimensional. Dessa forma, para melhor aplicação desses copolímeros, é muito importante o conhecimento dos parâmetros relativos ao seu comportamento em solução. A viscosimetria, em especial, é um método simples, útil e apropriado para fornecer essas informações. Os parâmetros viscosimétricos podem ser matematicamente calculados por extrapolação gráfica, entretanto a geração dos dados experimentais é mais demorada. Em contrapartida, é possível que a determinação experimental seja feita de forma mais rápida, por um único ponto, procedimento esse que desperta tanto o interesse acadêmico quanto o industrial. Neste trabalho, foram empregados os dois métodos de cálculo, utilizando solventes puros, misturas de solventes e três amostras de copolímeros à base de SMA. As determinações foram conduzidas a 40C. Os copolímeros utilizados possuiam teores de anidrido maleico de 50%, 45% e 40%, sendo os dois últimos esterificados com butil-metil-éster e sec-butil-metil-éster, respectivamente. Os solventes utilizados foram: N-metil-pirrolidona (NMP), tetrahidrofurano (THF) e suas respectivas misturas 1:1 com metil-etil-cetona (MEK), ou seja, (NMP:MEK) e THF:MEK, sendo a MEK um não solvente para o copolímero não esterificado. As equações utilizadas para extrapolação gráfica foram as de Huggins, Kraemer e Schulz-Blaschke. As equações empregadas em um único ponto foram as de Solomon-Ciuta, Deb-Chanterjee e novamente Schulz-Blaschke. Os resultados obtidos foram comparados e avaliou-se a possibilidade da utilização do método mais rápido, por um único ponto, para os sistemas estudados através dos desvios percentuais tendo como padrão os resultados da equação de Huggins. A equação de Deb-Chanterjee foi a mais adequada aos sistemas em NMP, que foi também o melhor solvente para as amostras. Os resultados obtidos na mistura NMP:MEK sugeriram que a viscosimetria pode ter sido um método sensível às pequenas diferenças estruturais entre os grupos pendentes nas amostras esterificadas. Paralelamente, realizou-se análises de espectroscopia na região do infravermelho (FTIR), análise termogravimétrica (TGA) e ensaios dinâmico-mecânicos (DMA) para a caracterização estrutural e térmica das amostras. Somente os resultados obtidos a partir de DMA indicaram diferenças entre as amostras esterificadas
Styrene maleic anhydride copolymers (SMA) are synthetic materials commercially available, obtained by the reaction of styrene with maleic anhydride, resulting in very versatile products obtained in a wide range of molar masses and maleic anhydride proportions. The copolymers are considered to be functional due to maleic anhydride reactivity, that provides a very large range of applications, and major importance in different areas, mainly for the low toxicity, good thermal resistance and excellent dimensional stability. Thus, for improving the application of these materials, it is necessary and important to understand the behavior of the copolymers in solution. Therefore, viscosimetry can be a simple, helpful and suitable method to provide these informations. The viscosimetric parameters are generally mathematically calculated by graphic extrapolation. However, the experiments take too long. Indeed, it is possible to reduce the time of the execution by employing a single point determination. In this work, both calculation methods were performed, using pure solvents and mixtures and three different copolymers samples, based on SMA. The tests were carried out at 40oC. The copolymers contained 50%, 45% and 40% of maleic anhydride groups and the last two copolymers were esterified with butyl-methyl ester and sec-butyl-methyl ester. N-methyl-pyrrolidone (NMP), tetrahydrofuran (THF), and their mixtures (1:1) with methyl-ethyl-cetone (MEK) were employed as solvents. The latter was a non-solvent for the esterified copolymers. The equations applied for graphic extrapolation were Huggins, Kraemer and Schulz-Blaschke. The equations employed for a single point determination were Solomon-Ciuta, Deb-Chanterjee and again Schulz-Blaschke. The single point determination method values were compared with those obtained from Huggins equation, and the possibility of using the faster method was evaluated by analyzing percentage deviation. Deb-Chanterjee equation was the most adequate to the copolymers in NMP, which was the best solvent for the samples. The results obtained in NMP:MEK mixture suggested that viscosimetry could be a sensitive method to the small structural variations between the pendant groups in the esterified samples. The copolymers were structurally characterized by infrared spectroscopy (FTIR), and thermally by thermogravimetric analysis (TGA) and dynamic-mecanical analysis (DMA). The results obtained from those techniques did not show significant differences between the esterified copolymers, except for DMA

Les benzoxaboroles sont des dérivés cycliques d'acides boroniques, récemment développés en médecine comme agents thérapeutiques. Dans cette thèse, une étude fondamentale de la formulation des benzoxaboroles dans des matériaux a été effectuée, utilisant le benzoxaborole le plus simple ainsi qu'un dérivé fluoré, l'AN2690 (antifongique approuvé par la FDA). L'étude a commencé par la détermination des données spectroscopiques de ces molécules à l'état solide, sous leur forme acide (à partir des molécules cristallisées), et basique (utilisant des matériaux modèles à base de benzoxaborolates) ; une variété de paramètres RMN a ainsi été établie pour chaque forme de la molécule. Par la suite, une première formulation a été développée par association de benzoxaborolates à un matériau inorganique de type « hydroxyde double lamellaire » (HDL Mg/Al-NO3). Un taux de charge à ~30 % massique en benzoxaboroles a pu être atteint, et des cinétiques de libérations rapides ont été observées. Cependant, une sensibilité des molécules au caractère basique de la matrice a été mise en évidence, et la structure de ces matériaux s'est avérée complexe, évoluant d'un mode d'intercalation normale à une structure de type « staging », en fonction du taux d'hydratation de l'espace interlamellaire. Dans une deuxième formulation, nous avons incorporé les benzoxaboroles, à divers taux de charge (jusqu'à 25% en masse), dans un polymère biorésorbable, l'acide poly-L-lactique (PLLA), avec une mise en forme en films et fibres, ces dernières étant formées par électrospinning. Dans ce cas, plusieurs vitesses de libération ont été obtenues, en modulant la composition et les conditions de préparation des matériaux, et les tests cellulaires réalisés (migration de cellules cancéreuses et tests antifongiques) sont en bonne corrélation avec ces cinétiques. Cette étude, dans son ensemble, permet d'élargir la gamme de formulations envisageables pour les benzoxaboroles, mais souligne aussi les enjeux associés à leur formulation dans des matériaux, du fait de la réactivité intrinsèque de la fonction benzoxaborole
Benzoxaboroles are cyclic derivatives of boronic acids, which have recently been developed as therapeutic agents. In this thesis, a fundamental study was carried out on the formulation of benzoxaboroles in materials, using the simplest benzoxaborole molecule and its fluorinated derivative, AN2690 (an antifungal agent approved by the FDA). The spectroscopic signatures of these molecules were first determined in the solid state, by looking at their acid form (using the crystallized molecules) and their basic form (using model materials based on benzoxaborolates), and this led to the establishment of the NMR parameters of each form of the molecules. A first formulation was then performed by association of benzoxaborolates with an inorganic material, a “layered double hydroxide” (Mg/Al-NO3 LDH). A loading capacity of ~ 30 wt% could be reached for this system and fast release kinetics were observed. However, the molecules were found to be sensitive to the basic character of the matrix. The resulting structure of these materials was also complex, due to the evolution from a normal mode of intercalation to a “staging” structure by dehydration of the interlamellar space. In a second formulation, the benzoxaboroles were incorporated at different loadings (up to 25 wt %), in a bioresorbable polymer, poly L lactic acid (PLLA), and shaped under the form of films and also fibers (which were obtained by electrospinning). Different release rates were achieved by varying the composition or the preparation conditions of the materials. Cellular assays investigating the migration of cancer cells and the inhibition of fungi showed a good correlation between these release rates and the cellular responses. Overall, this study allowed not only to increase the span of possible formulations of the benzoxaboroles, but also to highlight the issues related to their formulation in materials, due to the inherent reactivity of the benzaxoborole function

L'objectif du travail relève d'une approche micro cinétique expérimentale des réactions CO/O2 et CO/NO sur des catalyseurs Pt et Rh supportés. Dans un premier temps nous avons utilisé un modèle cinétique précédemment établi au laboratoire pour la réaction CO/O2 sur Pt/Al2O3 en vue de déterminer l'impact de la dispersion D du Pt sur le TOF de la réaction ainsi que les étapes élémentaires impliquées. Ceci nous a permis de corréler ces observations à la modification des étapes élémentaires. Des études menées en régimes transitoires lors de l'oxydation par O2 des espèces CO adsorbées indiquent une période d'induction dans la formation du CO2 observée uniquement pour D>0. 6. L'impact de divers paramètres expérimentaux a, à cet effet, été réalisé et un jeu d 'équations mathématiques a été établi modélisant correctement les données expériementales. Ces études montrent que la compétition d'adsorption entre les espèces CO-B et oxygènes faiblement adsorbés (Owads) constituent un processus clé dans l'observation d'une période d'induction. La procédure AEIR, appuyée de la spectroscopie FTIR, a été utilisée à l'étude de l'impact de divers paramètres sur la chaleur d'adsorption d'espèces CO adsorbées sur différents catalyseurs supportés. C'est dans l'objectif de déterminer celle d'espèces inactives en IR qu'une nouvelle méthode a été développée : TPAE. Dans un second temps, nous avons étudié l'impact de la présence de NO sur la réaction CO/O2. Des expériences menées par spectroscopie FTIR et spectrométrie de masse suggèrent que ce sont les espèces Nads, provenant de la dissociation de NO, qui perturbent la réaction d'oxydation des espèces CO adsorbées. Enfin, en préliminaire d'une modélisation cinétique des réactions CO/O2 sur Rh/Al2O3 d'une part et CO/NO sur Pt/Al2O3 et Rh/Al2O3, nous avons entrepris des expériences en régimes transitoires par une approche similaire à celles de CO/O2 sur Pt/Al2O3. En comparaison avec cette dernière, il est observé que la réaction CO/O2 sur Rh/Al2O3 exhibe de grandes ressemblances. Toutefois, la formation d'espèces gem di-carbonyls complique l'exploitation des données. Quant à la réaction CO/NO sur les deux catalyseurs, il apparaît que la vitesse d'oxydation par NO est plus lente que sous O2

Rapid advances in the level of technology in education and training have greatly increased possibilities for their use. This thesis investigates traditional and more recent applications of advanced technology. The goal of the work is to provide an introduction to concepts and considerations in implementing advanced technologies in education and training applications. Included is a model proposal for implementing advanced technologies in the Republic of China Air Force. The thesis offers conclusions about such an implementation; namely, that lead time to plan, availability and affordability of technology, expertise for development and administration, abilities required to participate, and overall effectiveness are considerations that must be addressed in the planning and design stages

L'objectif essentiel de ce travail est l'etude de la genese de la microstructure cellulaire, pour un alliage de composition sm(cofecuzr)#7#. #6#2. La microstructure du materiau, traite dans le domaine 1180-800#c selon des conditions variables, a ete caracterisee a differentes echelles. Le developpement de la morphologie cellulaire au cours du traitement de precipitation vers 850#)c a ete etudie. Parallelement, nous avons suivi l'evolution des proprietes magnetiques et en particulier de la coercitivite. Les resultats experimentaux conduisent a proposer une representation de l'evolution des phases avec la temperature dans le materiau, et des scenari de transformations de phases. L'influence de la composition des phases formees sur la coercitivite est mise en evidence. Des elements de reflexion sur l'origine de la coercitivite dans le materiau etudie sont egalement donnes

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Apresenta-se, neste trabalho, um estudo sistemático dos efeitos dos parâmetros experimentais [ângulo de deposição do feixe em relação ao substrato α (e/ou posição no substrato); velocidade de rotação do porta-substrato ω; campo magnético de deposição HD; temperatura do substrato TS] sobre os campos de anisotropias cúbica HKC, uniaxial HKU e de exchange bias HEB de filmes finos de Co e Gd, bicamadas de Co/IrMn e IrMn/Gd e tricamadas de Co/IrMn/Gd preparados pela técnica de magnetron sputtering. Usando a técnica de difração de raios-X, demonstrou-se que, independentemente dos valores dos parâmetros α, ω e HD, os filmes de Co crescem sobre a camada semente de Ta orientados na direção [111] com fase estrutural cúbica de face centrada fcc. Para os filmes de Gd, crescidos sobre o Ta, demonstrou-se que quanto maior o valor de TS maior a tensão interna na camada de Gd que, por sua vez, favorece a estabilização da fase fcc até a espessura de Gd tGd de 10 nm (anteriormente resultados da literatura reportavam valores de 4 nm). O aumento do valor de tGd ou a diminuição de TS provoca, nas camadas atômicas de Gd crescidas sobre o Ta, relaxação estrutural para a estrutura hexagonal compacta hcp. Com relação aos campos de anisotropias, obtidos pelas medidas de ressonância ferromagnética FMR, demonstrou-se que devido à deposição oblíqua α ≠ 0° pode-se controlar o campo de anisotropia uniaxial HKU do filme de Co, sendo que, para HD = 0, o máximo valor de HKU = 72 Oe para α = 55° e ω = 0 rpm. Combinando deposição oblíqua para valores baixos de α (22 ≤ α ≤ 40°) com diferentes velocidades de rotação ω (0, 30 e 40 rpm) do porta-substrato durante a deposição dos filmes de Co, controlam-se nas amostras anisotropias puramente cúbica HKC, puramente uniaxial HKU ou combinada HKC + HKU. Ainda dos resultados de FMR nos filmes de Co, demonstrou-se que o campo de anisotropia HKC ≅ 2,8 Oe permanece aproximadamente constante independentemente dos valores de α, ω e HD, enquanto que o campo de anisotropia HKU decresce linearmente com o aumento da velocidade de rotação ω a uma taxa de -0,35 Oe/rpm, (posição central: 15,7 ≥ HKU ≥ 1,4 Oe e extremidade do porta-substrato: 20,6 ≥ HKU ≥ 6,5 Oe, para o intervalo de 0 ≤ ω ≤ 40 rpm, respectivamente). Usando medidas de magnetometria, demonstrou-se que a fase fcc do Gd possui magnetização de 175 emu/cm3 e campo coercivo de 100 Oe, aproximadamente constantes em um amplo intervalo de temperatura (10 ≤ T ≤ 400 K), enquanto a fase hcp do Gd apresenta altos campo coercivo (HC = 480 Oe) e magnetização de saturação (MS = 640 emu/cm3). No caso das bicamadas Co/IrMn, verificou-se que a presença do campo de deposição HD (aplicado no plano do filme) aumenta significativamente o campo uniaxial HKU (13 → 33 Oe) e o de exchange bias HEB (33 → 55 Oe) quando preparam-se as amostras na posição central. Para os filmes produzidos nas extremidades do porta-substrato há um aumento ainda maior no valor de HKU (130%) devido à variação angular α durante a rotação do porta-amostra. Para as tricamadas, considerando também as amostras nas extremidades, o campo HKU sofre um aumento anômalo (~ 45 → ~ 220 Oe, 5 vezes), acompanhado por um aumento de 45% no valor do campo HEB (~ 55 → ~ 80 Oe) para a interface Co/IrMn, quando se cresce o Gd sobre a camada IrMn; fato ainda não compreendido.

Estudou-se a caracterização de blocos sinterizados à base de Co-Cr-Mo visando a obtenção de próteses odontológicas por fresagem CAD/CAM. O processo de sinterização foi estudado e ocorreu através do transporte difusional de massa e calor no estado sólido, denominado sinterização no estado sólido. Esse fenômeno produz uma forte união entre as partículas devido ao transporte de massa, em escala atômica, sob condições controladas de tempo, temperatura e atmosfera. Foram realizadas sinterizações interrompidas a 800, 1000, 1200 e 1300°C nos tempos de 15 minutos, 1 hora e 4 horas. A liga foi caracterizada nas condições recebida e sinterizadas em termos de composição química, propriedades mecânicas e caracterização microestrutural. Para isto, utilizou-se fluorescência de raios X, dilatometria, ensaios de Arquimedes, ensaios de dureza, ensaios de compressão, microscopia eletrônica de varredura (MEV), microscopia óptica e microanálise eletrônica dispersiva (EDS). Os resultados composicionais indicam que a liga se encontrava dentro da faixa de composição química estabelecida pelo manual do fabricante e pela norma ASTM 1537. As partículas analisadas na condição pré-sinterizada exibiram formato esférico, indicando uma provável utilização de pós atomizados. A estimativa do levantamento da distribuição do tamanho das partículas foi realizado utilizando o programa de computador ImageJ, e a distribuição foi caracterizada como assimétrica positiva. O material no estado recebido se apresentou monofásico. A fase presente encontrada foi ?Co com estrutura cristalina CFC. Em contrapartida, as amostras sinterizadas apresentaram porções de fase ?Co, com estrutura cristalina hexagonal, fase esta formada a partir da transformação ?Co <-> ?Co, na qual, a energia armazenada na forma de defeitos é a força motriz da transformação. E sugere que a transformação ocorreu durante resfriamento. A amostra sinterizada por quatro horas em 1200°C apresentou-se no estágio final de sinterização, dado que os poros encontrados tinham aspecto arredondado e com densificação maior que 90%. Os resultados de compressão indicam tensão média de ruptura de 2523 ± 168 MPa.
This work studied the characterization of Co-Cr-Mo sintered blocks in order to obtain dental prosthesis by prototyping CAD/CAM. The sintering process was studied through diffusional mass transport in solid state, termed solid state sintering. This phenomenon produces a strong bond between the particles due to mass transport, at the atomic scale, under controlled conditions of time, temperature and atmosphere. The interrupted sintering was performed at 800, 1000, 1200 and 1300 ° C in times to 15 minutes, 1 hour and 4 hours. The alloy was characterized in conditions as received and sintered in terms of chemical composition, mechanical properties and microstructural characterization. For this, we used X-ray fluorescence, dilatometry, Archimedes tests, hardness tests, compression tests, scanning electron microscopy (SEM), optical microscopy and dispersive electron microanalysis (EDS). The results indicate that the alloy was within the chemical composition range established by the manufacturer and ASTM 1537. The particles analyzed in the pre-sintered condition showed spherical shape, indicating a likely use of atomized powders. The estimate of the particle size distribution was performed using ImageJ software, and the distribution is characterized as positive asymmetric. The samples in the received state were monophasic. This phase was found ?Co with FCC crystal structure. On the order hand, the sintered samples showed ?Co phase portions with hexagonal crystal structure, phase formed from the transformation ?Co <-> ?Co, in which the energy stored in the form of defects is the driving force of transformation and suggests that transformation occurred during the cooling. Sample sintered during four hours at 1200°C was in the final stages of sintering, since the pores were found aspect rounded and densification above 90%. The compression results indicate rupture stress at 2523 ± 168 MPa.

L’intérêt grandissant envers les nanomatériaux a base des métaux de transition 3d comme le cobalt, le nickel et le fer trouve son origine dans les propriétés intrinsèques de ces éléments (forte aimantation du fer et constante magnétocristalline élevée du cobalt) combinées aux propriétés particulières offertes par la taille nanométrique et l’anisotropie de ces alliages. Parmi les nombreuses voies de synthèse dites de chimie douce, le procède polyol permet l’élaboration de plusieurs classes de matériaux inorganiques a l’état finement divises (oxydes, hydroxydes et métaux) grâce aux réactions de réduction et d’hydrolyse qui peuvent être conduites et contrôlées dans les milieux polyols. Le premier axe de ce travail a consisté à tirer profit de l’état finement divise des oxydes et hydroxydes élabores en milieu polyol pour l’obtention de métaux et alliages correspondants, au moyen d’une réduction ménagée a l’état solide sous flux d’hydrogène. Il a alors été possible d’aboutir a des particules de CoFe2, CoFe, NiFe, Ni3Fe et Fe ferromagnétiques avec une température de blocage supérieure a 300 K. Le deuxième axe de travail a trait a l’élaboration d’objets anisotropes. Pour ce faire, une nouvelle approche est proposée : la synthèse en milieu polyol assistée par l’application d’un champ magnétique. Ce type de synthèse mené a des nanofils d’akaganeite β-FeOOH et a des nanoparticules d’oxydes spinelles. Une réduction relativement douce (300 °C) des nanofils d’akaganeite permet de l’obtention de phases spinelles de même morphologie et avec des propriétés magnétiques en accord avec la composition chimique et le caractère nanométrique des particules (comportement superparamagnétique avec une température de blocage proche de 300 K, Ms élevée et Hc dépendant de la nature de l’élément M se trouvant dans le spinelle MFe2O4 : élevé dans le cas du cobalt et faible dans le cas du fer et du nickel)
The growing interest in nanomaterials based on 3d transition metals such as cobalt, iron and nickel finds its origin in the intrinsic properties of these elements (high magnetization of iron and high magnetocristalline constant of cobalt) combined with particular property due to nanometric size and anisotropy of these alloys. Among the numerous synthetic routes, the polyol method which belongs to the chimie douce routes allows the elaboration of several finely divided inorganic materials (oxides, hydroxides, metals) by means of reduction or forced hydrolysis reactions conducted in polyol medium. The main first contribution of this work was to take advantage of these finely divided oxides and hydroxides elaborated in polyol medium to obtain metals and alloys, through a controlled reduction in solid form under hydrogen flow. Ferromagnetic particles of CoFe2, CoFe, NiFe, Ni3Fe and Fe with a blocking temperature above 300 K were obtained. The second main contribution of this work relates elaboration of anisotropic objects. Further, a new approach is proposed: forced hydrolysis in polyol medium assisted by applying a magnetic field. This type of synthesis leads to akaganeite β7&eOOH nanowires and spinel oxides nanoparticles. A relative mild reduction (300 °C) of akaganeite nanowires allows to obtain spinels phase with same morphology and magnetic properties in agreement with the chemical composition and the particles nanoscale (superparamagnetic behavior with blocking temperaturenear 300 K, high Ms and Hc dependent on the nature of the M element in the spinel MFe2O4, high in the case of cobalt and low for nickel and iron)

Orientadora: Ana Sofia Clímaco Monteiro D'Oliveira
Dissertaçăo (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduaçăo em Engenharia Mecânica. Defesa: Curitiba, 2005
Inclui bibliografia
Resumo: Hardfacing o nome dado t cnica de revestir com uma liga de elevada durezaum material menos nobre. Revestimentos de Co s o aplicados em componentes expostosa desgaste na presenc¸a ou n o de temperaturas elevadas. Entre as ligas maisutilizadas encontram-se as ligas comercialmente conhecidas como Stellite 6 e Stellite1, a ltima mais freq entemente especificada para revestimentos de componentessujeitos a severo desgaste a alta temperatura, mas de dif ýcil soldabilidade. O Stellite6 utilizado como material “para v rias aplicac¸ es” devido ao amplo espectro deaplicac¸ es. Com o objetivo de aumentar a resist ncia da liga Stellite 6, foram adicionadasdiferentes quantidades (5% e 35%) de carbonetos de Tungst nio (WCoC)a liga atomizada. Ap s homogeneizac¸ o as misturas foram depositadas pelo processode plasma com arco transferido (PTA). Para efeitos de comparac¸ o tamb em foramproduzidos revestimentos da liga original de Stellite 6 sem adic¸ o de carbonetos detungst nio. Os dep sitos foram caracterizados quanto ao seu aspecto geral, dureza,diluic¸ o e ensaio de desgaste tipo pino sobre disco. A microestrutura foi avaliadarecorrendo microscopia tica e eletr nica de varredura e perfis de microdureza Vickers,com carga de 500g. Resultados mostraram ser poss ývel adaptar/melhorar ascaracter ýsticas dos revestimentos de Stellite 6 pela adic¸ o de diferentes quantidadesde carbonetos de Tungst nio, mantendo a facilidade de soldagem da liga original.

Orientador: Joni Augusto Cirelli
Banca: Raquel Scarel Caminaga
Banca: Willian Fernando Zambuzzi
Resumo: Com a evolução no desenvolvimento de biomateriais, a utilização de matrizes tridimensionais (scaffolds), construídas a partir de impressão tridimensional (3DP), via SLS (selective laser sinterization) e por Extrusão de Filamentos, vêm ganhando bastante destaque no ramo da engenharia tecidual óssea. A possibilidade de impressão de modelos 3D, baseado em modelo virtual prévio, com forma, tamanho, e porosidade altamente controlados, assemelha o material ao osso perdido, favorecendo a reconstrução de defeitos ósseos em substituição aos autoenxentos, considerados "padrão ouro". O objetivo deste trabalho foi caracterizar físico-química e biologicamente scaffolds à base de Poli(3-hidroxibutirato) (PHB), confeccionados por impressão 3D via SLS, revestidos com celulose bacteriana (CB), funcionalizados ou não com apatitas (HA) e/ou peptídeo de crescimento osteogênico (osteogenic growth peptide - OGP) (Estudo 1), assim como matrizes de Poli(hidroxibutirato-co-valerato) (PHBV) e PHBV-apatita radiopaca dopada com Lantânio (PHBV-La20OAP) confeccionadas por Extrusão de Filamentos (Estudo 2), com finalidade de regeneração óssea. Os resultados de caracterização físico-química por meio da MEV/EDS demonstraram que os scaffolds produzidos apresentaram composição química e arquitetura (forma e porosidade) adequadas. A resistência mecânica nos scaffolds de PHB não sofreu alteração significativa após o revestimento com CB; porém, teve redução com a adição de apatita. O lantânio promoveu um aumento ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: With the evolution in the development of biomaterials, the use of three-dimensional matrices (scaffolds), constructed from three-dimensional printing (3DP) via SLS (selective laser sinterization) and Filament Extrusion are gaining a lot of attention in the field of bone tissue engineering. The possibility to print 3D models based on previous virtual models with highly controlled shape, size and porosity, makes the material similar to the lost bone and favours the reconstruction of bone defects in the replacement of autografts considered "gold standard". The aim of this study was to physicochemically and biologically characterize Poly (3-hydroxybutyrate) (PHB) scaffolds, made by 3D printing via SLS coated with bacterial cellulose, functionalized or not with apatite (HA) and / or osteogenic growth peptide- (OGP) (Study 1) and matrices of Poly (hydroxybutyrate-co-valerate) (PHBV) and PHBV-La containing radiopaque apatite (PHBV-La20OAP) made by filament extrusion (Study 2) for bone regeneration. Results from physicochemical characterization by SEM/EDS demonstrated that the all produced scaffolds presented appropriate chemical composition and architecture (shape and porosity). The mechanical strength of the PHB scaffolds was not significantly affected my CB coating but was reduced after apatite addition. The La allowed an increase in the elasticity modulus of PHBV matrices. Experiments for analysis of the biological behaviour of the scaffolds showed that they allowed the maintenan... (Complete abstract click electronic access below)
Mestre

O interesse em óxido de zinco (ZnO) dopado com metais de transição tem atraído a atenção de pesquisadores nos últimos anos. Esses sistemas potencialmente apresentam temperatura de Curie acima da temperatura ambiente, o que possibilitaria sua aplicação em dispositivos spintrônicos. Entretanto, apesar dos extensos estudos, a natureza de suas propriedades magnéticas ainda permanece uma questão controversa. Recentemente resultados teóricos e experimentais têm mostrado que o ordenamento magnético é função direta de defeitos pontuais, tais como vacâncias de oxigênio e zinco intersticial. Neste contexto, esta dissertação descreve a caracterização estrutural e magnética de óxidos magnéticos diluídos (OMDs) nanoestruturados a base de ZnO dopados com Co em diferentes concentrações molares preparados a partir do método hidrotermal assistido por micro-ondas. Foram analizadas cinco amostras com concentrações molares de 0,5, 1, 3, 5 e 7% de Co. A caracterização estrutural foi realizada através das técnicas de Difração de Raios-X e Espectroscopia de Espalhamento RAMAN. A morfologia dos grãos dos pós preparados foi caracterizada por Microscopia Eletrônica de Transmissão de Alta Resolução. Em associação ao RAMAN e à Difração de Raios-X no teste da incorporação do Co à matriz de ZnO, medidas de Absorção de Raios-X foram utilizadas para obter informações sobre o estado de oxidação e simetria do sítio do átomo absorvedor, neste caso o Co. Por fim, as propriedades magnéticas foram analisadas através de magnetometria SQUID (Superconducting Quantum Interference Device). Os resultados obtidos comprovaram a incorporação do Co na estrutura do ZnO sem a formação de fases secundárias de óxido de Co ou Co metálico. A caracterização magnética das amostras dopadas apresenta características que definem um comportamento paramagnético com grande interação de troca antiferromagnética entre os íons Co2+. Além disso, as amostras com baixa concentração de Co () revelaram a coexistência de uma fase majoritariamente paramagnética e uma fase minoritária ferromagnética. O comportamento magnético de nossas amostras é entendido sob o escopo dos modelos teóricos BMP (Bound Magnetic Polaron) e d0. O estudo dos parâmetros magnéticos com base em um modelo randômico de distribuição dos íons dopantes e uma interação de troca simples entre os íons de Co2+ revela uma distribuição não homogênea ao longo do volume dos grãos.
The interest in Zinc Oxide (ZnO) doped with transition metal has been attracted much attention in the last years. These systems present Curie temperature above room temperature, this property enable its application in spintronic devices. In spite of the extensive studies, the origin of its magnetic properties still remains a controversial issue. Some recent theoretical and experimental results have shown that the ferromagnetic ordering depends on defects, such as oxygen vacancies or interstitial zinc, created during the sample preparation. In this context, this dissertation describes the structural and magnetic characterization of nanostructured diluted magnetic oxides (DMOs) based on Co-doped ZnO systems produced by microwave-assisted hydrothermal route. We have prepared nanostructured samples with Co molar concentrations of 0.5, 1, 3, 5 and 7%. The crystal structures of the samples were characterized using X-ray diffraction (XRD) and RAMAN scattering spectroscopy. The microstructure and composition distributions were characterized by high-resolution transmission electron microscopy (HRTEM). Co K-edge x-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) were used to determine the valence state and to evaluate the environment of Co in the ZnO lattice. Finally, magnetic characterizations were performed using a superconducting quantum interference device (SQUID) magnetometer. The results confirmed the Zn replacement by Co ions in the wurtzite ZnO structure with oxidation state of 2+, neither segregated secondary phases, nor Co-metal were detected. The magnetic characterization of the studied samples revelas a paramagnetic behavior with large antiferromagnetic exchange interaction between Co2+ ions. Besides, the samples with low concentration of Co () present the coexistence of a major paramagnetic phase associated to a minority ferromagnetic phase. The magnetic behavior of our samples are studied under the scope of the BMP (Bound Magnetic Polaron) and d0 theoretical models. The studied of the magnetic parameters through a model corresponding to a random distribution of the dopants and a simple exchange interaction between the Co2+ ions reveals a non-homogeneous distribution over the volume of the grains.
Fundação de Amparo à Pesquisa do Estado de Minas Gerais - FAPEMIG

Ce travail concerne la réalisation et la caractérisation de mélanges à base de polystyrène et de polyéthylène co-propylène ; le but étant d'obtenir des matériaux résistant à l'impact et présentant une stabilisation à l'oxydation par rapport aux autres polystyrènes chocs. Pour permettre une compatibilisation partielle des constituants, nous avons généré des liaisons ioniques en les modifiant chimiquement. Nous obtenons ainsi des polystyrènes carboxylates et des polyéthylène co-propylène sulfonates en utilisant trois différents cations et divers processus de mise en œuvre. La caractérisation des produits obtenus met en évidence une séparation totale de la phase élastomère, sous forme de nodules d'une taille moyenne de 0, 2 μm dans la matrice polystyrène. Nous avons observé l'influence du cursus de mélange et de la formulation sur la nature des liaisons ioniques, l'adhésion entre les nodules d'élastomères et la matrice, les propriétés mécaniques statiques et la résistance à l'impact. Nous montrons en particulier ·les relations qui existent entre la qualité de l'adhésion des nodules à la matrice et la présence d'agrégats ioniques, en exploitant respectivement des mesures viscoélastiques suivant un modèle de Kerner modifié et les résultats de spectrométrie infrarouge. Nous mettons en évidence une amélioration de la résistance à l'impact, limitée toutefois par une taille des nodules d'élastomère inadaptée à la matrice.

Divers monomeres carbonate de vinyle aromatiques et aliphatiques ont ete polymerises en masse a 35#oc. L'amorcage resulte de la decomposition du percarbonate de bis-(4 tertiobutylcyclohexyle), ce qui a permis d'obtenir des polymeres de masses moleculaires elevees. L'effet du radical substituant sur les proprietes physico-chimiques des polymeres a ete etudie. Certains de ces monomeres ont ensuite ete copolymerises avec le styrene et le methacrylate de methyle en solution dans le dichloromethane a 70#oc, en presence d'azobisisobutyronitrile. Les rapports de reactivite r#1 et r#2 ont ete determines par la methode de kelen-tudos. Une nouvelle serie de monomeres acryliques u-substitues a ete (co)polymerisee en emulsion avec le styrene et l'acrylate de methyle a 70#oc, en presence de persulfate de potassium. L'evolution cinetique des (co)polymerisations a ete etudiee en fonction de la nature et de la concentration en monomere acrylique, et de la quantite d'amorceur et d'emulsifiant. La composition et les proprietes physico-chimiques des (co)-polymeres resultants, ainsi que les proprietes coloidales des latex, ont ete etudiees par irtf, #1hrmn, gpc, dsc, ddl, tensiometrie et viscosimetrie

L'amelioration des performances des catalyseurs d'hydrodesulfuration est rendue necessaire par l'evolution des normes antipollution sur les teneurs en soufre des combustibles et en particulier des gazoles. Les catalyseurs actuellement utilises sont du type comop/al#2o#3. Ce travail propose une nouvelle methode de synthese de ces solides. Nous avons prepare des catalyseurs d'hds a partir de sels d'heteropolyanions a structure de keggin associant le molybdene, le cobalt et le phosphore ou le silicium, le cobalt etant introduit en contre-ion de l'unite de keggin. Une reduction de l'heteropolyanion induit une augmentation de la charge et permet ainsi de moduler le rapport co/mo. Par ailleurs, une preparation originale d'heteropolyanion monosubstitue du type co#3xymo#1#1o#4#0#n# y = p, si ; n = 1, 2, ou x (co ou ni) est au sein meme de l'unite de keggin a la place d'un atome de molybdene, est presentee. Les caracterisations physico-chimiques realisees a chaque etape de la preparation du catalyseur permettent de decrire la genese des precurseurs oxydes. Ces solides sont actives par sulfuration. Les catalyseurs sont testes en hds du thiophene et les activites sont comparees a celles obtenues avec des catalyseurs prepares selon les procedures industrielles.

The phase behavior of CO2 + polymer systems is of interest in polymer synthesis, flue and natural gas processing, polymer foam and nanoparticle processing, and drug delivery. Theoretical and experimental evidence suggests that CO2 is able to interact with electron donating functional groups in polymers to form weak Lewis acid – base or EDA (Electron Donor Acceptor) complexes. These complexes can have a significant effect on the phase behavior of associated CO2 + polymer systems. In spite of this, however, the phase equilibria of only a few associated CO2 + polymer systems have been measured. Some success in modeling the phase behavior of polymer solutions has been achieved by various versions of the Statistical Association Fluid Theory (SAFT), as well as by several Lattice Models. However, many of these models incorporate two to four adjustable parameters that often depend on temperature (T), pressure (P), and/or molecular weight (MW). As a result, a large amount of experimental data is required to apply these models. The goal of the present work was therefore to develop a new thermodynamic model for associating systems that would include no more than two temperature-independent adjustable parameters. The new model presented in this work is based on the Guggenheim-Huggins-Miller lattice and includes complex formation in the development of the partition function. The EOS obtained from the resulting partition function includes two mixture parameters – the enthalpy of association or complex formation and a reference value of the equilibrium constant for complex formation . Most importantly, can be obtained from in situ Attenuated Total Reflection Fourier Transform Infrared (ATR – FTIR) measurements. This work therefore demonstrates the use of ATR – FTIR spectra to obtain molecular level information regarding the interaction of CO2 and electron donating functional groups in polymers. Unlike other studies, this work uses the bending vibration of CO2 to estimate the enthalpies of association ( ) of CO2 + polymer systems. Values of were directly incorporated in the new model and were found to lie between -7 and -12 kJ/mol for the systems investigated in this work. They increased (i.e. became more negative) in the order: CO2 + PS-co-PMMA < CO2 + PMMA