Os aços inoxidáveis austeníticos são os mais utilizados em situações onde é indispensável resistência à corrosão e excelentes propriedades mecânicas. O níquel costuma ser o principal elemento de liga utilizado na estabilização da fase austenítica, e nos últimos anos seu valor, de acordo com a London Metal Exchange, sofreu variações abruptas de preço, desestabilizando o mercado do aço inoxidável. Nesse contexto os aços da série 200, também conhecidos como aços Cr-Mn-Ni, que substituem parte do níquel por manganês para manter a estabilidade da fase austenítica, tiveram sua produção incrementada. O objetivo do presente trabalho foi comparar a resistência à corrosão por pite de dois aços inoxidáveis austeníticos, aço 17Cr-6Mn-5Ni (designado como aço 298, não normalizado) e o aço UNS S30403. Para tanto, foram estudadas duas variáveis: o efeito da temperatura de solubilização e da composição química do eletrólito, a qual foi constituída por soluções aquosas com teor fixo de 0,6M NaCl e adições progressivas de Na2SO4 visando verificar o efeito inibidor do íon sulfato nos diferentes aços com os diferentes tratamentos de solubilização (1010°C, 1040°C, 1070°C e 1100°C). A corrosão por pite foi determinada através de ensaios de polarização potenciodinâmica cíclica e os resultados obtidos foram discutidos através das variações microestruturais encontradas. Foram empregadas técnicas de microscopia ótica e eletrônica de varredura, análises por dispersão de energia, difração de raios X, medidas magnéticas com ferritoscópio e análise de imagem para quantificação da fase ferrita. Primeiramente, constatou-se que, na maioria das condições de composição química de eletrólito e tratamento térmico, em geral o aço UNS S30403 apresenta maior potencial de pite do que o aço 298. Mais detalhadamente, os resultados mostraram que a adição de íon sulfato aumenta a resistência à corrosão por pite em meio contendo cloreto dos aços 298 e UNS S30403 em todas as condições de tratamento térmico, sendo que o efeito benéfico da adição de sulfato é mais acentuado para o aço 298. O tratamento de solubilização teve pouca influência sobre a resistência à corrosão por pite do aço UNS S30403 (considerando-se cada eletrólito isoladamente); por outro lado, o aço 298 apresentou forte dependência com o tratamento térmico: na ausência de sulfato (0,6M NaCl) os tratamentos de solubilização diminuíram o potencial de pite; já na presença de sulfato, teores crescentes de Na2SO4 tiveram um efeito benéfico, cada vez mais forte, chegando ao ponto de atingir, para as concentrações de 0,6M Na2SO4 nas condições de tratamento térmico a 1070°C e 1100°C, potenciais de pite mais elevados do que os respectivos para o aço UNS S30403. Foi detectada a presença de uma segunda fase (ferrita, enriquecida em cromo) em ambos os aços (UNS S30403 e 298), e a presença de precipitados ricos em manganês no aço 298. Os distintos comportamentos foram explicados através da solubilização dos precipitados ricos em manganês. Concluiu-se que a dissolução, de tais precipitados, permitiu o aumento do teor de manganês na matriz austenítica do aço 298, sendo que a consequência disso, para o eletrólito puro em NaCl, foi a diminuição do potencial de pite desse aço, enquanto que na presença de sulfato, o efeito inibidor desse íon foi potencializado devido a maior afinidade química entre o íon sulfato e o elemento manganês - agora em solução sólida comparativamente àquela do íon cloreto e este elemento. Como o aço UNS S30403 não apresenta manganês como elemento de liga, nem consequentemente os precipitados ricos nesse elemento, o efeito deletério da solubilização, não foi observado em NaCl, e o efeito benéfico da adição de Na2SO4, sobre a resistência à corrosão por pite, não foi significativo para esse aço em função da temperatura de solubilização. / Austenitic stainless steels are widely used when both high corrosion and mechanical resistance are essentials. In general, nickel is added to stainless steels to stabilize the austenite phase. During the last decade, the nickel price fluctuated considerably; unstabling the stainless steel global market. The 200 series stainless steels, also known as Cr-Mn-Ni stainless steels, emerged as an alternative for traditional austenitic steels. In these steels, manganese replaces a fraction of nickel content, maintaining stable the austenitic phase. Consequently, the production of stainless steel containing manganese has increased notoriously. The present study has the aim to compare the pitting resistance corrosion, between the 17Cr-6Mn-5Ni (designated as 298) and UNS S30403 austenitic stainless steels. The effect of solution heat treatment temperature, and the chemical composition of environment aqueous solution were evaluated (the electrolytes used are constituted for aqueous solution with 0,6M NaCl fixed and Na2SO4 progress additions) verifying the inhibitor effect of sulfate ion in both steels on distinct temperature ranges (1010°C, 1040°C, 1070°C and 1100°C) defined for the solution heat treatments. The pitting corrosion resistance was determined by means of cyclic potentiodynamic polarization, and the answers obtained were discussed through the microstructural variations found. Optical and electron microscopy technique, X ray diffraction analysis, magnetic measurements using the ferritoscope and image analysis to ferrite phase quantification were used during this investigation. In most conditions examined, the UNS S30403 steel show highest pitting potential that 298 steel. In more detail, the results showed that addition of sodium sulfate increased the pitting corrosion resistance in media containing chloride ions of both UNS S30403 and 298 steels, in all heat treatment conditions, being more pronounced in 298 steel. The solution heat treatment had little influence on pitting resistance corrosion of UNS S30403 steel (considering separately each electrolyte); on the other hand, the 298 steel showed a strong dependence with the heat treatments: in absence of sulfate (0,6M NaCl) the heat treatments decreased the pitting corrosion resistance, but in presence of sulfate, the gradual increment of Na2SO4 concentration had a beneficial effect, each time more strong, reaching, for 0,6M NaCl+0,6M Na2SO4 condition in heat treatment temperatures 1070°C and 1100°C, higher pitting potential values than UNS S30403 steel. The presence of a chromium-rich second phase (chromium ferrite) in both steels (UNS S30403 and 298) and manganese-rich precipitates in 298 steel were detected. The different behaviors were explained through annealing solution of manganese-rich precipitates found in 298 steel. It is concluded that after heat treatments, the dissolution of these precipitates increased the manganese content in solid solution in 298 steel. Consequently decreasing the pitting potential values for 0,6M NaCl electrochemical condition (environment without Na2SO4). On the other hand, in presence of Na2SO4 the inhibitor effect is potentialized due to highest chemical affinity between ion sulfate and manganese (now in solid solution) compared to that between chloride ion and manganese. The UNS S30403 stainless steel does not contain manganese as alloying element, nor manganese-rich precipitates, deleterious effect in 0,6M NaCl was not observed, and the beneficial effect on pitting corrosion resistance due the sulfate additions was not significantly different in this steel when the annealing solution temperature is changed.

Ces travaux traitent de l’influence du procédé d’élaboration sur l’état métallurgique et les propriétés mécaniques et anti-corrosion des alliages de Ni-W nanostructurés, dans le but de mieux comprendre le rôle de différents paramètres physico-chimiques sur ces propriétés. Pour cela, deux techniques de dépôt sont utilisées : l’électrodéposition et la pulvérisation cathodique magnétron. Une approche multi-échelle associant différentes techniques permet la caractérisation fine de la morphologie, de la taille de grains, de la texture, de la nature des joints de grains ainsi que de la composition chimique des alliages et de leur contamination. En fonction de la technique d’élaboration utilisée, la relation entre la teneur en W et les paramètres métallurgiques est très différente avec un impact du W beaucoup plus marqué pour les électrodépôts par rapport aux alliages obtenus par pulvérisation. Les propriétés des revêtements sont évaluées par des tests de microdureté et des essais électrochimiques (courbe de polarisation et spectroscopie d’impédance électrochimique). Une augmentation de la microdureté est généralement observée avec la diminution de la taille de grains et l’augmentation de la teneur en W dans les alliages de Ni-W. Cependant, les valeurs de microdureté les plus importantes sont toujours atteintes pour de hautes teneurs en tungstène mais pas forcément pour les tailles de grains les plus faibles. Une limite dans l’augmentation de la microdureté avec la diminution de la taille de grains a donc été mise en avant. L’étude de la réactivité électrochimique des alliages en milieu acide a permis de montrer un rôle prépondérant du tungstène qui va dépendre du pH, du domaine étudié et des réactions associées. La morphologie de surface et les défauts structuraux vont également pouvoir influencer la réactivité des alliages de Ni-W avec une influence qui peut dépasser celle des solutés. En comparaison, les autres paramètres microstructuraux (taille et orientation des grains, nature des joints de grains et contamination) ne semblent avoir qu’un impact mineur sur le comportement électrochimique. / The aim of this study is to understand the influence of the deposition process on the metallurgical state and the mechanical and anti-corrosion properties of the nanostructured Ni-W alloys. Two processes are performed to obtain our alloys : the electrodeposition and the magnetron sputtering. A combination of several microstructural techniques at different scales has permitted the characterization of the morphology, the grain size, the crystallographic texture, the nature of grain boundaries and the concentrations of alloying elements. According to the elaboration process, the relationship between the W content and the metallurgical parameters is very different. A stronger influence of W is observed for the electrodeposited coatings by comparison with the alloys obtained by sputtering. The properties of the coatings are studied with microhardness measurements and electrochemical tests (polarization curve and electrochemical spectroscopy impedance). An increase of the microhardness is mainly observed with the decrease of grain size and the increase of tungsten content. But, the highest values of microhardness are always obtained for the highest tungsten content and not necessarily for the lowest grain size. So, a limit for the increase of microhardness with the decrease of grain size is put forward. The study of the electrochemical reactivity for the alloys in acidic media have shown a dominating role of the tungsten that depend on the pH, the studied domain and the reaction path associated with the corrosion process. The surface morphology and the structural defects have also an important influence on the reactivity of the Ni-W alloys that can exceed the impact of solute. As compared, the others metallurgical parameters (grain size, texture, grain boundaries and contamination) seem to have a minor influence on the electrochemical behavior.

Ces travaux abordent, d'une part l'étude de la coordination du cuivre(II) et nickel(II) avec un ligand heptadenté tripode, et d'autre part la synthèse et la caractérisation de liquides ioniques dérivés de la bétaïne.Tout d'abord, le ligand heptadenté, le tris[(L)-alanyl-2-carboxamidoéthyl]amine (H3trenala), a été synthétisé sous forme de sel de chlorure ; ses constantes de protonation ainsi que les constantes de stabilité des complexes de Cu(II) et de Ni(II) ont été déterminées par potentiométrie. Des espèces complexes mononucléaires dans lesquels le ligand est protonné ([Cu(H5trenala)]4+, [M(H4trenala)]3+), neutre ([M(H3trenala)]2+) ou déprotonné ([M(H2trenala)]+, [M(Htrenala)]) (M = Cu2+ ou Ni2+) ont été mises en évidence. Seul le Cu(II) donne des espèces dinucléaires dans lesquels le ligand est uniquement déprotonné ([Cu2(H2trenala)]2+, [Cu2(Htrenala)]2+, [Cu2(trenala)]+, [Cu2(trenala)(OH)]). A l'état solide, deux complexes dinucléaires de cuivre(II) ont pu être isolés et caractérisés (IR, UV-Vis, masse électrospray, ATG). L'étude des propriétés catalytiques de ces deux complexes montre une faible activité vis-à-vis de la réaction d'oxydation du catéchol.La seconde partie de ce travail présente la synthèse de liquides ioniques constitués par des synthons cationiques dérivés d'ester de glycine-bétaïne {trialkyl(2-éthoxy-2-oxoéthyl)ammonium (alkyl = éthyl, n-propyl et n-butyl), N-(1-méthylpyrrolidyl-2-éthoxy-2oxoéthyl)ammonium} et des anions inorganiques {bis(trifluorosulfonyl)imide (NTf2-), dicyanamide (Dca-), tétrafluoroborate (BF4-)}. Les influences de la longueur de la chaîne alkyle portée par l'atome d'azote ammonium et de la nature de l'anion associé sur les propriétés physicochimiques telles que la densité, les températures de fusion, de transition vitreuse et de décomposition, la viscosité et les fenêtres électrochimiques, ont été déterminées. De plus, des sels fondus ont pu être générés à partir de ces cations organiques associés aux anions tetrafluoroborate, dicyanamide, hexafluorophosphate (PF6-) et perchlorate (ClO4-), et leurs propriétés physicochimiques ainsi que leurs structures cristallines ont été déterminées.Ensuite, les liquides ioniques hydrophobes sont utilisés pour l'extraction des cations métalliques [Cu(II), Ni(II), Cd(II) et Pb(II)] en phase aqueuse. Cette étude montre que les rendements d'extraction d'ions métalliques, déterminés par mesure de la concentration résiduelle en métal en phase aqueuse, dépendent de la longueur de la chaîne alkyle portée par l'atome d'azote ammonium et des propriétés chélatantes de l'anion. Les rendements les plus élevés ont été obtenus avec les liquides ioniques dont l'anion possède des propriétés chélatantes. L'étude du transfert du métal montre qu'il est dépendant de l'hydrophobicité du synthon cationique. Une augmentation de l'hydrophobicité du synthon cationique conduit à une augmentation du rendement d'extraction, tout en limitant l'échange ionique et en privilégiant une extraction par paires d'ions. Enfin, l'électrodéposition en phase liquide ionique et la désextraction liquide-liquide des ions métalliques ont été étudiées. / This work deals with copper(II) and nickel(II) complexation of a polydentate tripodal ligand and with, on a second part, the synthesis and characterization of ionic liquids derived from betaine and their use in liquid-liquid extraction.On the first part, a heptadentate ligand, tris[(L)-alanyl-2-carboxamidoethyl]amine (H3trenala), has been synthesized as its tetrahydrochloride salt; its protonation constants and the stability constants of the copper(II) and nickel(II) chelates have been determined by potentiometry. Mononuclear species with protonated, neutral, or deprotonated forms of the ligand, [Cu(H5trenala)]4+, [M(H4trenala)]3+, [M(H3trenala)]2+, [M(H2trenala)]+, and [M(Htrenala)] (M=Cu2+ and Ni2+) have been detected in all cases, while only Cu2+ gives dinuclear [Cu2(H2trenala)]2+, [Cu2(Htrenala)]2+, [Cu2(trenala)]+, and [Cu2(trenala)(OH)] species. Two dinuclear copper(II) complexes have been prepared and characterized by spectroscopic techniques (IR, UV-Vis, mass electro-spray) and thermogravimetric analysis. These two dinuclear copper(II) complexes have revealed weak catalytic activity in catechol oxidation.On the second part, a series of salts based on ethyl ester betaine derivatives[trialkyl(2-ethoxy-2-oxoethyl)ammonium or N-(1-methylpyrrolidyl-2-ethoxy-2-oxoethyl)ammonium cations] with alkyl chains [ethyl, n-propyl and n-butyl] have been synthesized. These cations generate hydrophobic ionic liquids with bis(trifluoromethylsulfonyl)imide, tetrafluoroborate or dicyanamide anions. The influence of the alkyl chain length and the chemical nature of the counteranion on physicochemical properties such as density, melting point, glass transition and decomposition temperatures, viscosity, and electrochemical window have been investigated. In addition, molten salts have been generated from these organic cations with hexafluorophosphate, perchlorate, tetrafluoroborate or dicyanamide anions. Their physicochemical properties and crystal structure have been investigated.The extraction of the different metal cations (Cu2+, Ni2+, Cd2+ and Pb2+) in aqueous solution by hydrophobic ionic liquids synthesized was performed. The extraction yields, determined by the measurements of the residual metal concentration in aqueous solution, depend not only the length of the alkyl chain of the ammonium but also on the nature of the associated anion. The most promising results are obtained with ILs whose anion has a chelating ability. The mechanism of metal transfer has been studied and was related to the hydrophobicity of the cationic synthon. Increasing the hydrophobicity of the cationic synthon leads to an increase of extraction yield, thus limiting the ion exchange and promoting ion pairing extraction. Electrodeposition in ionic liquid phase and liquid-liquid desextraction of metallic ions have also been investigated.

Desde a descoberta das ligas amorfas em 1960, os motivos pelos quais algumas ligas podem ser facilmente amorfizadas enquanto outras não podem, não é claramente conhecido, assim não há teoria universal para predizer a habilidade de formação vítrea em sistemas metálicos. No presente trabalho, um critério de seleção foi aplicado ao sistema Ni-Nb-Zr com o objetivo de predizer as melhores estequiometrias com as mais altas tendências de formação vítrea. As habilidades de formação vítrea das ligas foram avaliadas pelo parâmetro térmico γm e os resultados mostraram uma pobre correlação com as predições. Este critério preditivo correlaciona as taxas de resfriamento para a formação vítrea com a instabilidade topológica de estruturas cristalinas, as diferenças médias de função trabalho e densidade eletrônica entre os elementos constituintes da liga. O parâmetro térmico depende de temperaturas características de transformações de fases que podem ser facilmente determinadas a partir de curvas de calorimetria exploratória diferencial dos vidros metálicos. As hipóteses iniciais para explicar a pobre correlação entre os resultados e as predições foram atribuídas às influências de fatores não considerados nos cálculos como os compostos intermetálicos desconhecidos e contaminação por oxigênio. Assim, algumas ligas solidificadas rapidamente foram investigadas com mais rigor com o objetivo de entender a formação das fases cristalinas que competem contra a formação vítrea. As fases cristalinas foram caracterizadas e comparadas com estruturas cristalinas encontradas na literatura como também alguns diagramas de fases. Os diagramas de fases foram utilizados como guias para o melhor entendimento do comportamento de cristalização. Em adição, o critério de seleção também foi utilizado para predizer o melhoramento da tendência de formação vítrea de uma liga do sistema Ni-Nb-Zr com pequenas adições dos elementos terras-raras Y ou Er. É bem conhecido que uma pequena adição de um elemento terra-rara apropriado pode aumentar significativamente a habilidade de formação vítrea de algumas ligas. As tendências de formação vítrea da liga base e das ligas dopadas com terras-raras também foram avaliadas pelo parâmetro térmico &#947m e os resultados concordaram muito bem com a tendência predita pelo cálculo. As amostras amorfas volumosas foram produzidas por injeção em molde de cobre. A natureza amorfa foi analisada por difração de raios-X e calorimetria exploratória diferencial. As fases cristalinas foram analisadas por microscopia eletrônica de transmissão, microscopia eletrônica de varredura, espectroscopia de raios-X por dispersão em energia e difração de raios-X. A contaminação por oxigênio foi quantificada pelo método de fusão em gás inerte. / Since the discovering of amorphous alloys in 1960, the actual causes of why some alloys can be easily formed into glasses while others cannot, are not clearly known, thus there is no universal theory to predict the glass forming ability in metallic systems. In the present work, a selection criterion was applied in the Ni-Nb-Zr system in order to predict the best stoichiometries with high glass forming ability. The actual glass forming ability of alloys were evaluated by the thermal parameter γm and the results have shown a poor correlation with the predictions. This criterion correlates critical cooling rate for glass formation with topological instability of stable crystalline structures; average work function difference and average electron density difference among the constituent elements of the alloy. The thermal parameter depends on the characteristic temperatures of phase transformations which can be easily measured from differential scanning calorimetry curves of metallic glasses. The initial hypotheses to explain the poor correlation between the experimental results and the predictions concerned with the influence of factors not considered in the calculation, such as unknown intermetallic compounds and oxygen contamination. Thus some rapidly quenched alloys were investigated with more accuracy in order to understand the formation of crystalline phases which compete against the glass formation. We characterized the crystalline phases and compared them to crystalline structures found in literature as well as some phase diagrams. The phase diagrams were used as guides in order to understand the crystallization behavior. In addition, the selection criterion also was used to predict the glass forming ability improvement of a Ni-Nb-Zr alloy with minor additions of rare-earth elements Y or Er. It is well known that the minor amount addition of proper rare-earth elements can greatly enhance the glass forming ability of some glass-forming alloys. The actual glass forming ability of the base alloy and rare-earth doped alloys also were evaluated by the thermal parameter &#947m and the results agree very well with the tendency predicted by the calculation. Bulk amorphous specimens were produced by injection casting. The amorphous nature was analyzed by X-ray diffraction and differential scanning calorimetry. The crystalline phases were analyzed by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and x-ray diffraction. Oxygen contamination was quantified by the inert gas fusion method.

Ce travail démontre l'utilité des propriétés photothermiques dans le proche Infrarouge (NIR) des complexes de nickel-bis(dithiolène) neutres pour des applications en science des matériaux et biotechnologies. Des complexes Ni-bis(dithiolène) neutres hydrophiles et hydrophobes ont été élaborés et leur effet photothermique, sous irradiation laser NIR, a été quantifié pour la première fois. Grâce à cette propriété remarquable et à leur grande stabilité sous irradiation, il a été mis en évidence, que ces complexes pouvaient trouver des applications pour la thérapie photothermique, la libération contrôlée de médicament mais également pour le développement de nanomatériaux photosensibles à un stimulus externe. En effet, cet effet photothermique, sous irradiation laser NIR, permet de détruire des cellules cancéreuses, d'augmenter la perméabilité de nanoparticules polymériques ou de liposomes contenant des principes actifs et de désagréger des métallogels à base de complexes Ni-bis(dithiolène). Enfin, nous avons montré que les complexes [Ni(R2-timdt)2]0 ayant une haute efficacité photothermique sont de nouveaux candidats très prometteurs pour ce type d'applications. / The photothermal properties in the near Infrared (NIR) of neutral nickel-bis(dithiolene) complexes were used in materials science and for the first time in biotechnology. Hydrophilic and hydrophobic neutral Ni-bis(dithiolene) complexes were developped and for the first time, their photothermal effect under NIR laser irradiation was quantified. Thanks to this remarkable property and their high stability under irradiaton, it has been demonstrated that these complexes could find applications to photothermal therapy, controlled drug delivery but also in the developpement of stimuli responsive nanomaterials. Indeed, this photothermal effect, under NIR laser irradiation, allow to destroy malignant cells, increase the permeability of polymeric nanoparticles or liposomes containing active ingredients and disintegrate métallogels based on Ni-bis(dithiolene) cores. Finally, we showed that the [Ni(R2-timdt)2]0 complexes having higher phothothermal activity are very promising new candidates for these applications.

[pt] As ligas metálicas têm sido amplamente estudadas, visando atender aplicações onde propriedades físicas e químicas diferenciadas se fazem necessárias. Nesse sentido, merecem destaque as ligas voltadas ao recobrimento de substratos metálicos, tendo-se como objetivo a proteção do substrato em ambientes corrosivos. Sendo assim, a presente pesquisa propõe abordar um método de síntese de ligas de Cu-Ni em substratos de cobre através da decomposição térmica do nitrato de níquel, e subsequentemente a redução do óxido NiO formado, mediante redução com H2 a 350 graus Celsius e tratamento térmico na mesma atmosfera a 800 graus Celsius, com tempos variados (3, 4 e 5h), para estimular a difusão do níquel produzido no interior da matriz de Cu. Os filmes serão caracterizados via microscopia eletrônica de varredura (MEV), tanto em sessões transversais, quanto panorâmico, além da difração de raios-x (DRX) com incidência rasante, visando-se identificar a liga Cu-Ni produzida. Os resultados sugerem que o processo proposto foi bem-sucedido, permitindo um amplo recobrimento do substrato e a subsequente difusão do Ni produzido, o que permitiu a identificação, em todas as amostras, da liga de interesse. As amostras selecionadas serão futuramente utilizadas para ensaios de microdureza, bem como de eletro-corrosão, sendo o comportamento medido comparando-se com o substrato puro. Espera-se que a presença do recobrimento eleve a resistência à abrasão, bem como dificultar a corrosão do cobre presente. / [en] Metal alloys has been extensively studied to light upon applications where differentiated physical and chemical properties are required. In this context, its value highlighting the alloys for the coating of metallic substrates with the objective of protecting the substrate in corrosive environments. The present work proposes to approach a method of synthesis of Cu-Ni alloys in copper substrates through the thermal decomposition of nickel nitrate and subsequently to discount the NiO oxide formed by reduction with H2 at 350 degrees Celsius and heat treatment in the same atmosphere at 800 degrees Celsius with (3, 4 and 5h) to stimulate the diffusion of the nickel produced inside the Cu matrix. The films were then characterized by scanning electron microscopy (SEM) in both cross-sectional and panoramic sessions, in addition to X-ray diffraction (XRD) with low incidence, aiming to identify Cu-Ni alloy produced. The results suggest that the proposed process was successful, allowing a wide coating of the substrate and subsequent diffusion of Ni produced, which allowed the identification in all samples of the alloy of interest. Selected samples will be used in the future for microhardness tests, as well as for electro-corrosion, and the measured behavior is compared to that observed for pure substrate. The presence of the coating is expected to raise the abrasion resistance as well as to hinder the corrosion of the copper present.

Ce travail porte sur la synthèse, la caractérisation et l’évaluation en catalyse de réduction des protons en dihydrogène, de nouveaux complexes de Ni(II), Co(III), Cu(II) et Pd(II) basés sur des ligands de type thiosemicarbazone. La nature de l’espèce catalytique active a été étudiée par voltampérométrie cyclique et des propositions de mécanisme ont été formulés sur la base de calcul quantique de type DFT.Le premier chapitre introduit le contexte scientifique. Le second chapitre concerne la synthèse et la caractérisation des ligands de type N2S2 et des complexes mononucléaires associés de Ni, Cu et Pd. Le troisième chapitre présente la synthèse et la caractérisation de complexes binucléaires de Co et trinucléaire de Ni.Les études électrochimiques de ces complexes dans le DMF en présence d’une source de protons, nous a permis d’évaluer leur efficacité catalytique. Nos résultats montrent que les complexes du Cu et du Pd présentent une vague irréversible spécifique pour la réduction des protons, mais une décomposition est observée durant l’électrolyse. Par contre, les complexes de Ni et de Co ont montré une stabilité électrochimique ainsi que de bonnes performances catalytiques. En particulier, le nouveau complexe mononucléaire de Ni présente des propriétés catalytiques remarquables qui le classent parmi les meilleurs catalyseurs de la réduction des protons décrits dans la littérature. L’ensemble de ce travail fourni une description complète du comportement électrochimique des ligands de type N2S2 complexés à des métaux de transition. Il permet d’envisager des développements futurs dans l’amélioration des propriétés catalytiques de ces complexes. / This work focuses on the synthesis, the characterization and the catalytic evaluation in the reduction of protons into dihydrogen, of new complexes of Ni(II), Co(III), Cu(II) and Pd(II) based ligands Type thiosemicarbazone. The catalytically active species during the process of the proton reduction was studied by cyclic voltammetry and mechanisms were formulated on the basis quantum chemical calculation.The first chapter introduces the scientific context, the goals and the main objectives of this work. The second chapter concerns the synthesis and the characterization of the N2S2 ligands and their associated mononuclear complexes, Ni, Cu and Pd. The third chapter presents the synthesis and the characterization of binuclear Co and trinuclear Ni based on N2S2 ligand.Electrochemical studies of these complexes in DMF in the presence of a proton source (trifluoroacetic acid), allowed us to evaluate their catalytic efficiency. Our results show that Cu and Pd complexes have a specific irreversible wave for the reduction of protons, but decomposition is observed during electrolysis, which makes these uninteresting complexes for the reduction of protons.On the contrary, Ni and Co complexes showed an electrochemical stability and good catalytic performances. In particular, the new mononuclear Ni complex exhibits remarkable catalytic properties that rank it among the best catalysts for the reduction of protons reported in the literature. All this work provided a complete description of the electrochemical behavior of N2S2 thiosemicarbazone ligands complexed to transition metals. It allows considering future developments in improving the catalytic properties of these complexes.

La réduction des émissions anthropiques de CO2 constitue actuellement un enjeu majeur. Parmi les technologies destinées à la production d'énergie, le Chemical Looping Combustion (CLC) présente un potentiel intéressant avec un faible coût de capture de CO2. Le CLC consiste à produire de l'énergie à partir de combustibles fossiles, en présence d’un transporteur d’oxygène solide qui fournit l’oxygène nécessaire à la combustion. Le matériau est ensuite régénéré sous air dans un deuxième réacteur. En sortie du réacteur de combustion, seuls les gaz CO2 et H2O sont émis et ainsi, après la condensation de l’eau, du CO2 quasiment pur est obtenu. La viabilité du procédé CLC à échelle industrielle dépend des performances et de la durée de vie des transporteurs d’oxygène utilisés. Au cours de cette thèse, les performances et le vieillissement d’un transporteur d'oxygène modèle (NiO/NiAl2O4), vis-à-vis de l’oxydation de CO ont été étudiées. Pour cela, des cycles d'oxydation-réduction dans un réacteur à lit fixe traversé ont été réalisés. Au cours de l’étude de l'influence des conditions de fonctionnement sur les performances du transporteur, il a été observé que la réactivité du transporteur augmente avec la température. De plus, le liant (NiAl2O4) participe également à la réaction d’oxydation du CO. Une évolution de la structure cristalline du liant au cours des cycles à haute température, a été mise en évidence à l’aide des techniques de caractérisation du solide (DRX, MEB-EDX, TPR,...). En parallèle à ces travaux, un outil numérique de simulation du lit fixe traversé a été développé afin de modéliser la réaction de réduction du transporteur d'oxygène avec le combustible CO. / Nowadays, the reduction of anthropogenic greenhouse gas emissions (especially CO2) constitutes an important challenge. Among the different technologies currently studied for the CO2 capture during energy production, the Chemical Looping Combustion (CLC) shows an interesting potential with a low cost of capture. CLC consists of producing energy from fossil fuels or biomass combustion, in the presence of an oxygen carrier (generally a metal oxide) which provides the required oxygen for combustion. The material is then reoxidized with air in a different reactor. At the combustion reactor outlet only H2O and CO2 gases are emitted, therefore after condensation almost pure CO2 can be obtained. The success of a large scale CLC application depends on finding suitable oxygen carriers with good performances and long lifetime. The objective of this work is to study the performances and the ageing of a model oxygen carrier (NiO/NiAl2O4) with CO as fuel. For this, oxidation/reduction cycles have been carried out in a fixed bed reactor. The influence of the operating conditions on its performances is also investigated. From these studies, it is observed that the reactivity of the oxygen carrier increases with temperature. Moreover, the binder used in the oxygen carrier (NiAl2O4) reacts also with the fuel CO to produce CO2. An evolution on the support’s structure during cycles at high temperature is demonstrated using solid characterization techniques (DRX, MEB-EDX and TPR). After these experimental studies, a numerical model has been developed to simulate the reduction reaction of the oxygen carrier with CO in a fixed bed reactor.

A demanda por combustíveis cada vez menos prejudiciais ao meio ambiente, leva à necessidade de desenvolvimento de processos industriais cada vez mais eficientes. No caso da produção de diesel, há uma crescente preocupação com a emissão de derivados do enxofre após a queima do combustível. Tais derivados são responsáveis, principalmente, pelo surgimento de chuvas ácidas. A tecnologia de retirada de enxofre dos combustíveis fósseis já está bem estabelecida na indústria, através de processos catalíticos conhecidos como hidrotratamento. O aprimoramento destes processos está intimamente ligado ao desenvolvimento de catalisadores cada vez mais eficientes. Visando o desenvolvimento de tais materiais, este trabalho apresenta a síntese de catalisadores Ni-Mo/Al2O3 para hidrodessulfurização no refino de petróleo, preparados a partir do método de síntese conhecido como processo poliol e posteriormente sulfetados in situ. A preparação destes catalisadores demonstrou que tal método de síntese favorece a formação do óxido misto de níquel e molibdênio em duas estruturas cristalinas distintas, ?-NiMoO4 e ?-NiMoO4. Normalmente, a formação destas fases não é muito explorada na literatura de catalisadores para hidrodessulfurização. Outro resultado muito interessante obtido a partir deste trabalho é em relação às propriedades texturais de tais catalisadores. Observa-se que, a partir do processo poliol, poucas alterações em termos de área específica e volume de poros dos catalisadores em relação à alumina adotada como suporte são esperadas. No entanto, testes catalíticos demonstraram que os resultados de conversão em termos de hidrodessulfurização da molécula modelo dibenzotiofeno foram insatisfatórios em comparação a um catalisador comercial. Acredita-se que este comportamento seja proveniente da formação do NiMoO4, que mitiga a ação promotora do níquel na estrutura do óxido de molibdênio. O presente trabalho demonstra a necessidade de maiores estudos em relação à aplicação das duas estruturas de molibdato de níquel frente às reações de hidrodessulfurização. / The demand for less harmful fuels to the environment leads to the necessity of developing more and more efficient industrial processes. In the case of diesel production, there is a growing concern about the emission of sulfur compounds after the fuel has been burned. Such compounds are mainly responsible for the emerging of acid rain. Sulfur removing technology for fossil fuels is already well established in the industry through catalytic processes known as hydrotreatment. The improvement of these processes is closely connected to the development of increasingly efficient catalysts. Aiming for the development of such materials, this study presents the synthesis of Ni-Mo/Al2O3 catalysts for hydrodesulfurization in petroleum refining, prepared from the synthesis method known as the polyol-mediated synthesis and after in situ sulfidation. The preparation of these catalysts has shown that such a synthesis method favors the formation of the mixed oxide of nickel and molybdenum in two distinct crystalline structures, ?-NiMoO4 and ?-NiMoO4. Normally, the formation of these structures is not much explored in the literature of hydrodesulfurization catalysts. Another really interesting result obtained from this work is in relation to the textural properties of such catalysts. It is observed that, from the polyolmediated synthesis, few changes in terms of specific surface area and pore volume of the catalysts in comparison with the alumina adopted as a support are expected. However, catalytic tests have shown that the conversion results in terms of hydrodesulfurization of the dibenzothiophene molecule model were unsatisfactory compared to a commercial catalyst. It is believed that this behavior comes from the formation of NiMoO4, which mitigates the promoting action of nickel in the structure of molybdenum oxide. The present work demonstrates the necessity for further studies regarding the application of the two nickel molybdate structures to the hydrodesulfurization reactions.

L'objectif de cette étude est de regarder l'influence du Pt sur la formation des siliciures de Ni dans le procédé Salicide et en particulier sur la phase basse résistivité NiSi, envisagée par l'industrie pour réaliser les contacts avec les zones actives de transistors de type Flash. Pour cela, nous avons étudié la nature, la séquence et la cinétique des phases formées, d'une part sur le système Ni1-xPtx/Si(100) (0% ≤ x ≤ 30%), et plus particulièrement sur un système intéressant pour certaines de ces propriétés, Ni(13%Pt)/Si(100). Deux types de dépôts ont été confrontés : dépôts réalisés avec une cible alliée Ni(13%Pt) ou par codéposition (cibles Ni et Pt dissociées). Ainsi nous avons couplé différentes techniques de caractérisation in situ (diffraction des rayons X, Réflectivité des rayons X (RRX), résistivité 4 pointes) pour essayer de comprendre les mécanismes liés à ce système. En particulier des expériences de RRX in-situ, associées à une analyse par transformée de Fourier inverse, ont été mises en œuvre, en utilisant le rayonnement synchrotron (ESRF), et aboutissent à des résultats originaux : la séquence des phases est modifiée dans le cas du Ni(13%Pt). Enfin, des premières mesures de résistance sur lignes étroites ont été réalisées, soulignant les avantages et les limites associées à l'utilisation d'un tel système.