La mucoviscidose est la maladie génétique la plus fréquente dans la population caucasienne. Le genre Scedosporium se situe au deuxième rang parmi les champignons filamenteux isolés des expectorations dans ce contexte. Au niveau pulmonaire, les colonisations/infections entraînent le recrutement de phagocytes qui induisent un stress oxydatif normalement délétère pour les pathogènes. Pour se défendre, ceux-ci ont développé des systèmes antioxydants, notamment diverses enzymes. Ce travail de thèse visait à étudier la réponse au stress oxydatif chez Scedosporium. Tout d’abord, la capacité à germer en présence d’oxydants a été évaluée. Par la suite, trente-trois gènes potentiellement impliqués dans la défense contre le stress oxydatif ont été identifiés. Leur expression en présence d’oxydants et en co-cultures avec des phagocytes suggère un rôle majeur, notamment pour une catalase, une peroxyrédoxine et deux thiorédoxine réductases. Par ailleurs, un mutant défectif pour un gène codant une superoxyde dismutase (SOD) pariétale et spécifique des spores a été produit. L’auranofin, un inhibiteur des thiorédoxine réductases, présente une activité vis-à-vis des Scedosporium et un effet additif avec des triazolés. Un test ELISA a été développé pour le sérodiagnostic des scédosporioses, utilisant une catalase et une Cu/Zn-SOD recombinantes. Ce test sensible et spécifique permet de distinguer les infections à Scedosporium de celles à Aspergillus fumigatus et des colonisations à Scedosporium. Au final, ces résultats indiquent un rôle majeur des enzymes antioxydantes chez Scedosporium, qui pourraient être de véritables facteurs de virulence et donc de nouvelles cibles thérapeutiques. / Cystic fibrosis (CF) is the most common genetic disease in Caucasian populations. The Scedosporium genus ranks the second among the filamentous fungi colonizing the airways of CF patients. In the respiratory tract, colonizations/infections lead to the recruitment of phagocytes which produce an oxidative stress, usually deleterious for pathogens. To defend themselves, pathogens have developed protective antioxidant systems, especially various enzymes. This thesis aimed to study the oxidative stress response in Scedosporium species. First, capacity of several Scedosporium isolates to germinate upon oxidative stress conditions was evaluated. Then, thirty-three genes potentially involved in protection against the oxidative stress were identified. Their overexpression in response to oxidants and in co-cultures with phagocytes suggested a crucial role, especially for one catalase, one peroxiredoxin and the two thioredoxin reductases. A mutant defective for the gene encoding a superoxide dismutase (SOD) anchored to the cell wall and specific for the conidia was produced. Auranofin, a thioredoxin reductase inhibitor, exhibits little anti-Scedosporium activity and an additive effect with triazole drugs. An ELISA was developed for serodiagnosis of scedosporiosis, using recombinant proteins derived from one catalase and a Cu/Zn-SOD. This sensitive and specific assay allows to differentiate Scedosporium infections from Aspergillus fumigatus infections and Scedosporium colonizations. Finally, these results indicate a crucial role of antioxidant enzymes in Scedosporium species, which could therefore be considered as virulence factors and as possible new therapeutic targets.

Le procédé de soudage par friction malaxage (FSW) entraîne, d’une manière générale, une importante chute de dureté à travers le joint soudé. Dans le but de concevoir des structures aéronautiques soudées par FSW en fatigue, il est nécessaire de connaître l’impact de cette chute de dureté dans le comportement mécanique global de la soudure. Dans ces travaux, l’alliage d’aluminium à durcissement structural 2198-T8 est considéré. Une chaîne de calcul de durée de vie en fatigue d’une structure soudée par FSW est mise en place. Elle intègre un couplage de calculs et d’expériences grâce auxquels le comportement mécanique de la structure est modélisé. Dans un premier temps, le gradient de comportement mécanique de la soudure est étudié. Des essais mécaniques de traction et cycliques sont réalisés à température ambiante. La méthode de corrélation d’images numériques (DIC) est utilisée dans le but de mesurer les champs de déplacements localement dans et au voisinage du joint soudé. À partir des résultats expérimentaux, les paramètres mécaniques d’un modèle de comportement sont identifiés à partir d’un élément de volume, zone par zone à travers le joint soudé. En parallèle, une quantification des précipités durcissants T1 (Al2CuLi) est menée dans différentes zones du joint soudé à l’aide d’un Microscope Electronique en Transmission (MET). Un lien entre l’évolution de la microstructure à travers la soudure et l’évolution des paramètres mécaniques est recherché. Le modèle de comportement mécanique est utilisé sur des calculs de structure utilisant la méthode des éléments finis pour simuler le joint soudé. En parallèle, des essais de fatigue sont réalisés sur des éprouvettes uniaxiales et cruciformes soumises à des chargements uniaxiaux et multiaxiaux. À l’aide des simulations du gradient de comportement mécanique du joint soudé ainsi que des résultats mesurés en fatigue, les paramètres d’un modèle d’endommagement sont identifiés. Ce modèle est utilisé pour prédire les durées de vie en fatigue et les zones d’amorçages de fissure pour une structure soudée soumise à des chargements multiaxiaux. / The Friction Stir Welding (FSW) process generally induces a critical hardness decrease inside the welded joint. To design aeronautical structure welded by FSW in fatigue, it is then necessary to know the impact of this hardness drop on the constitutive behaviour of the junction. In this study, the hardening structural aluminium alloy 2198-T8 is considered.A fatigue lifetime assessment loop of a welded structure is implemented. It integrates a calculations and experiments coupling which is used to model the structure’s mechanical behaviour. The gradient mechanical behaviour of the weldment is initially studied.Monotonic and cyclic mechanical tests are carried out to room temperature. Digital Image Correlation (DIC) is used to measure local displacement fields around the junction. Based on this experimental data, mechanical parameters for a constitutive model are identified on a volume element, zone by zone across the welded joint. In parallel, a quantification of the T1 (Al2CuLi) strengthening precipitates is realized in different region of the joint with a Transmission Electron Microscope. A connection between the microstructure evolution and the mechanical parameters is researched. The gradient mechanical behaviour of the joint is assessed on a 3D structure by Finite Element Analysis. Furthermore, fatigue tests are carried out on uniaxial and multiaxial loadings welded specimen. Thanks to the mechanical behaviour model and the fatigue lifetime measured, a damage model is used to predict the fatigue lifetime and the crack initiation zone for a welded structure which is subjected to higher multiaxial loads.

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.

Os fármacos antiinflamatórios não-esteróides (FAINEs) são amplamente utilizados no combate a processos inflamatórios e dores, mas apresentam restrição de uso em razão de sérios efeitos colaterais sobre o trato gastrointestinal. A atividade biológica de complexos metálicos tem sido objeto de pesquisa de grande interesse na área de metalofármacos e compostos do tipo Cu(II)-FAINEs apresentam boa atividade antiinflamatória e efeitos colaterais reduzidos em relação aos fármacos orgânicos. Nesse trabalho, com o objetivo de contribuir para ampliar os estudos sobre o desenvolvimento de alternativas aos FAINEs, foram preparados e caracterizados complexos cobre(lI) com ibuprofeno, indometacina, naproxeno, sulindaco, meloxicam. Os compostos foram imobilizados em Hidrotalcita, um hidróxido duplo lamelar (HDL) de magnésio e alumínio (Mg/AI = 3) que é biocompatível e tem uso como antiácido estomacal. As interações dos metalofármacos com o HDL geraram materiais híbridos bioinorgânicos do tipo Cu-FAINElHDL, nos quais os complexos podem estar presentes de duas maneiras: intercalados entre as Ia meias ou adsorvidos nas superfícies externas do hidróxido duplo lamelar, dependendo do solvente utilizado. A intercalação de complexos neutros é favorecida em solvente misto álcooVamida no qual a Hidrotalcita sofre esfoliação promovida por um processo de hidrólise da amida. A estabilidade alguns dos complexos e dos materiais híbridos em condições gástricas simuladas (pH e temperatura) e as atividades antiinflamatória, analgésica e ulcerogênica in vivo dos sistemas contendo indometacina (Indo) foram investigadas. A intercalação do complexo Cu-Indo no HDL favorece sua estabilização, contribuindo para potencializar a sua atividade farmacolágica. Os materiais híbridos bioinorgânicos obtidos neste trabalho apresentam propriedades interessantes com vistas a potencial aplicação como sistemas de liberação controlada de fármacos. / Non-steroidal anti-inflammatory drugs are widely consumed to treat inflammatory diseases and pain but their clinical use are limited due to serious side-effects on the gastrointestinal tract. The bioactivity of metal complexes exhibits great interest in metal-based drug research. Cu(II)-NSAID compounds show good anti-inflammatory property and decreased side-effects compared to their organic parent drugs. This work aimed to contribute for development of alternative NSAIDs. Cu-NSAlD compounds containing the drugs Ibuprofen, Indomethacin, Naproxen, Sulindac and Meloxicam were synthesized and characterized. The compounds were also immobilized on Hydrotalcite, a layered double hydroxide (LDH) of magnesium and aluminum (Mg/Al = 3), that is biocompatible and used as stomach antacid. The interactions of the copper drugs with LDH led to Cu-NSAID/LDH- bioinorganic hybrid materiais. Two kinds of complex-LDH interactions were observed by changing the solvent: intercalation between LDH layers or adsorption on the LDH external surfaces. The intercalation of neutral complexes is favored in an alcohollamide solvent mixture where Hydrotalcite undergoes exfoliation process promoted by the amide hydrolysis. The stability of some complexes and their correspondent hybrid materials under gastric conditions (pH and temperature) and also in vivo anti-inflammatory, analgesic and ulcerogenic activities for Indomethacin (Indo)-containing systems were investigated. The stabilization of the Cu-Indo structure is promoted by intercalation of the complex into the LDH layers, contributing to increase its pharmacological activity. The bioinorganic hybrid materials here investigated also exhibit interesting properties for applications as controlled drug delivery systems.

[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.

Whist copper (Cu) is an essential element for plants, when this element is present in excess quantities it can cause irreversible damage. This metal induces excessive production of reactive oxygen species (ROS), which damages organelles causing dysfunction. A possible means for the promotion of metal tolerance in plants is the adition of the element silicon (Si). The current study was conducted with the aim of evaluating the role of Si (0, 1 and 3 mmol L-1) on the morphologic, nutritional, metabolic and physiological responses of Panicum maximum cv. Tanzania under different Cu rates (0.3, 250, 500 and 750 μmol L-1). The grass was grown in a greenhouse under hydroponic conditions for two growth periods (33 and 30 days). Thirteen days after sowing, the seedlings were transplanted to a nutrient solution and supplied just with the Cu rate of 0.3 μmol L-1 and the set Si rates for 25 days. The remaining Cu rates were only added for a seven day period during the first growth stage. The second harvest took place 31 days after the first harvest. The experiment had six randomized blocks: three for yield, morphology and nutritional analyses and three for metabolic and physiological analyses. Plant yield, morphology and metabolic parameters were quantified in shoots and roots. Chlorophyll content index (SPAD values) and gas exchange parameters were determined in diagnostic leaves (DL), and Cu and Si concentrations were analysed from the DL and roots. The calculation of Cu and Si contents took into account the whole plant biomass. Plants exposed to Cu rates above 0.3 μmol L-1 showed low values of plant yield, morphologic parameters and SPAD, in both growth periods. Silicon supplied plants showed lower Cu concentration and content, and higher values of plant yield, morphlogic parameters and SPAD than the ones with no Si application. Silicon concentration and content were higher in plants exposed to excess Cu compared to those exposed to the control rate (0.3 μmol L-1). Gas exchange parameters in plants of the first growth were positively affected by Si supply and negatively affected by Cu rates. In the second growth, an eustress event was observed, in which plants exposed to stressing rates of residual Cu showed the highest values of gas exchange parameters and the lowest values of stress indicators. The activities of antioxidant enzymes were reduced with the increment in Cu rates. Silicon supply resulted in an increment in superoxide dismutase (SOD) activity. Tanzania guinea grass supplied with Si was able to better deal with Cu toxicity, showing increases in plant yield, morphologic and gas exchange parameters. Silicon supplied plants reduced their absorption of Cu and consequently, plants exposed to high Cu rates were still able to produce considerable biomass in the regrowth. / O cobre (Cu) é um elemento essencial para as plantas, porém, quando em excesso, pode causar danos irreversíveis às plantas. Este metal induz a produção excessiva de espécies reativas de oxigênio (ERO), que danificam organelas causando a disfunção delas. Uma possível maneira de aumentar a tolerância de plantas aos metais é o fornecimento de silício (Si). Um experimento foi conduzido com o objetivo de avaliar o papel do Si (0, 1 e 3 mmol L-1) nas respostas morfológicas, nutricionais, metabólicas e fisiológicas do Panicum maximum cv. Tanzânia sob doses de Cu (0,3, 250, 500 e 750 μmol L-1). Esse capim foi cultivado hidroponicamente em casa de vegetação por dois períodos de crescimento (33 e 30 dias). Treze dias após a semeadura, plântulas foram transplantadas para solução nutritiva, fornecendo-se apenas as doses de Si por 25 dias. A exposição ao cobre foi realizada apenas no primeiro crescimento das plantas e durou sete dias. O segundo corte ocorreu 31 dias após o primeiro corte. O experimento consistia de seis blocos completos ao acaso: três para avaliações de produção, morfologia e análises nutricionais e três para análises metabólicas e fisiológicas. A produção, a morfologia e o metabolismo das plantas foram quantificados na parte aérea e nas raízes. O índice de conteúdo de clorofila (valores SPAD) e as análises fisiológicas foram determinados nas lâminas diagnósticas (LD), e as concentrações de Cu e Si nas LD e nas raízes. Para o cálculo dos acúmulos de Cu e Si levou-se em consideração toda a biomassa da planta. Plantas expostas a doses de Cu acima de 0,3 μmol L-1 apresentaram menores valores de produtividade, parâmetros morfológicos e de SPAD. Plantas supridas com Si apresentaram menor concentração e acúmulo de Cu, e maiores valores de produtividade, parâmetros morfológicos e SPAD do que aquelas que não receberam o fornecimento de Si. A concentração e o acúmulo de silício foram maiores nas plantas expostas ao excesso de Cu do que nas expostas à dose controle de Cu (0,3 μmol L-1). Os parâmetros de trocas gasosas das plantas no primeiro crescimento foram afetados positivamente pelo Si e negativamente pelo incremento nas doses de Cu. No segundo crescimento, observou-se evento de eustresse em que plantas expostas à dose de Cu residual apresentaram os valores mais altos de parâmetros de troca gasosa e os valores mais baixos de indicadores de estresse. As atividades de enzimas antioxidantes foram reduzidas com o incremento nas doses de Cu. O suprimento de silício resultou em incremento na atividade da superóxido dismutase (SOD). O capim tanzânia suplementado com Si foi capaz de suportar melhor a toxicidade do Cu, mostrando um aumento na produção de biomassa da planta, e em parâmetros morfológicos e de trocas gasosas. As plantas suplementadas com Si reduziram a absorção de Cu e, consequentemente, plantas expostas a altas taxas de Cu e suplementadas com Si ainda foram capazes de produzir uma biomassa apreciável na rebrota.

Bacterial infections caused by the formation of a biofilm on the implant aftersurgery is a severe problem affecting the implants long term function and often leading to implant failure. Copper is a natural trace element found in the human body, and has recently become a possible alloying element with strongantibacterial properties. In this master thesis, copper bearing titanium alloys with different concentrations of Cu (1, 3, 5 and 10 wt.% Cu) were prepared using two different heat treatments (T1 and T2) in order to kill the bacteria and prevent the formation of biofilms causing these infections. The antibacterial performance andCu ion release rate of the Ti-Cu alloys were investigated in order to determine their applicability as a biomaterial. The results from the experimental investigations showed that the addition of Cu provided the alloys with an antibacterial effect against Staphylococcus epidermidis. The alloys with 5 and 10 wt.% Cu had improved antibacterial properties, and the alloys with highest Cu content exhibited the strongest antibacterial ability with an antibacterial rate of 42% for the 10- Cu(T2) alloy and 48% for the 10-Cu(T1) alloy, after 6 hours. The Cu ion release rate of the Ti-Cu alloys with 1, 3 and 5 wt.% Cu were far below the daily recommended allowance according to WHO, while the alloys with 10 wt.% Cu showed Cu ion release rates substantially over the daily limit. For this reason, Ti- Cu alloys with less Cu content (>10 wt.%) are recommended. Nevertheless, Ti-Cu alloys have a promising future as a medical implant with antibacterial properties.

Les nanostructures magnétiques peuvent avoir des propriétés très différentes de celles des matériaux massifs. Une des méthodes pour élaborer de petits objets est l'évaporation sur un substrat nanostructuré tel qu'une surface vicinale présentant des marches à l'échelle atomique. La compréhension des propriétés magnétiques de ces systèmes nécessite une caractérisation précise de leur structure et de leur morphologie afin d'évaluer les effets dus aux contraintes épitaxiales et aux dimensions réduites. Nous avons étudié les films de cobalt déposés sur des surfaces de Cu(1 1 11) et Cu(115) par trois techniques. Leur magnétisme a été sondé par effet Kerr magnéto-optique tandis que leur morphologie et leur structure cristallographique ont fait l'objet de mesures respectivement par microscopie à effet tunnel et EXAFS de surface. Les mesures par effet Kerr montrent une anisotropie uniaxiale magnétique avec un axe de facile aimantation parallèle aux bords de marches. L'anisotropie mesurée sur Cu(115), le substrat ayant les terrasses les moins larges, est plus importante. Les expériences de STM montrent la forte mobilité du cuivre dès les faibles taux de couverture ainsi qu'une grande évolution de la morphologie en fonction de la quantité de cobalt déposée. Grâce à l'EXAFS, nous avons montré que dès 3 monocouches (MC) de cobalt sur Cu(1 1 11) et 5 MC sur Cu(115), la structure est quasiment identique à celle observée sur Cu (001) i.e. tétragonale à faces centrées et que la présence de terrasses étroites n'engendrent pas d'anisotropie dans le plan (001). Des simulations de l'anisotropie magnétique prenant en compte les liaisons manquantes à la surface et en bord de marche (modèle de Néel) ainsi que les effets magnétoélastiques induits par la tétragonalisation de la maille montrent que l'anisotropie uniaxiale est très majoritairement due à la morphologie des films et que la distorsion de la maille de cobalt y contribue très peu.

Les mécanismes de formation de phases dans des films minces du système ternaire Al-Cu-Fe et des systèmes binaires Al-Cu, Al-Fe et Cu-Fe ont été étudiés. Dans chacun des systèmes, plusieurs échantillons avec des compositions distinctes ont été préparés par pulvérisation cathodique. Des couches d'aluminium, de cuivre et de fer ont été déposées séquentiellement sur des substrats de silicium oxydé et ont été traités thermiquement par différentes méthodes puis caractérisés. Des mesures de diffraction de rayons X et de résistivité in-situ ont été effectuées pour suivre la formation des phases. Des recuits thermiques suivis de trempe ont été réalisés et les échantillons ont été caractérisés par diffraction des rayons X. L'analyse enthalpique différentielle a également été utilisée ainsi que des mesures simultanées in-situ de résistivité et de diffraction des rayons X. L'ensemble des résultats obtenus nous a permis de proposer des mécanismes de formation de phases pour chacun des échantillons étudiés et en utilisant des modèles théoriques de croissance de phases nous avons pu déterminer des données cinétiques sur la formation de phases dans ces films.

The bulk metallic glasses (BMGs) are potential metallic materials due to their interesting properties, such as the high strength, high elastic strain limit, and high wear/corrosion resistance. Over the past four decades, a variety of studies have been done on the characteristics of the mechanical, thermodynamic properties of such category of metallic materials, but there still remain many questions about basic deformation mechanisms and their microstructures so far. Molecular dynamics (MD) simulation can provide significant insight into material properties under the atomic level and see a detailed picture of the model under available investigation in explaining the connection of macroscopic properties to atomic scale. MD simulation is applied to study the material properties and the deformation mechanisms in various binary metallic glasses and intended to examine the feasibility of MD simulation to compare the experimental results obtained in our laboratory over the past few years. The gradual vitrification evolution of atom mixing and local atomic pairing structure of the binary Zr-Ni, Zr-Ti alloys and pure Zr element during severe deformation at room temperature is traced numerically by molecular dynamic simulation. It is found that the icosahedra clusters will gradually develop with the increasing of disorder environment of alloys in the Zr-Ni, Zr-Ti systems, forming amorphous atomic packing. Other compound-like transition structures were also observed in transient in the Zr-Ni couple during the solid-state amorphization process under severe plastic deformation. The crystalline pure Zr can be vitrified in the simulation provided that the rolling speed is high enough and the rolling temperature is maintained at around 300 K. On the other hand, the effective medium theory (EMT) inter-atomic potential is employed in the molecular dynamics (MD) simulation to challenge the study of the diffusion properties in the Mg-Cu thin films. The transition of local structures of Mg-Cu thin films is traced at annealing temperatures of 300, 413, and 500 K. Furthermore, the simulation results are compared with the experimental results obtained from the transmission electron microscopy and X-ray diffraction. The gradual evolution of the local atomic pairing and cluster structure is discussed in light of the Mg and Cu atomic characteristics. Lately, the progress of the cyclic-fatigue damage in a binary Zr-Cu metallic glass in small size scale is investigated using classical molecular-dynamics (MD) simulations. The three-dimensional Zr-Cu fully amorphous structure is produced by quenching at a cooling rate 5 K/ps (ps = 10-12 s-1) from a high liquid temperature. The Nose-Hoover chain method is used to control the temperature and pressure to maintain a reasonable thermodynamic state during the MD-simulation process, as well as to bring the imposed cyclic stress on the subsequent simulation process. Both the stress- and strain-control cyclic loadings are applied to investigate the structural response and free-volume evolution. The overall structure would consistently maintain the amorphous state during cyclic loading. The plastic deformation in simulated samples proceeds via the network-like development of individual shear transition zones (STZs) by the reversible and irreversible structure-relaxations during cyclic loading, dislike the contribution of shear band in large-scale specimens. Dynamic recovery and reversible/irreversible structure rearrangements occur in the current model, along with annihilation of excessive free volumes. This behavior might be able to retard the damage growth of metallic glass and enhance their fatigue life.