Nutzbare Energie ist ein knappes Gut. Aus ökonomischen und ökologischen Gründen wird die effiziente und nachhaltige Nutzung der verfügbaren Energie angestrebt. Wird Energie in elektrischer Form bereitgestellt oder transportiert, kommt der Minimierung der Verluste an elektrotechnischen Anlagen oder Bauelementen eine grundlegende Bedeutung zu. So werden beispielsweise Transformatorenkomponenten und Verstärkerelemente aus weichmagnetischen Werkstoffen mit geringem Ummagnetisierungsverlust gefertigt. In dieser Arbeit wird der Zusammenhang zwischen der magnetischen Mikrostruktur und dem magnetischen Ummagnetisierungsverlust nanokristalliner Ringbandkerne untersucht. Der Einfluss von Stärke und Lage einer induzierten Anisotropie wird anhand induktiver Hysteresemessung und simultaner Beobachtung magnetischer Domänen mit stroboskopischer Kerrmikroskopie charakterisiert.

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Du fait de leurs excellentes propriétés mécaniques et de leurs faibles masses spécifiques, l’utilisation des matériaux composites, au sein des structures mécaniques, est en plein essor. Cependant, leur usinage entraine une usure prématurée et aléatoire des outils de coupes en cermet WC-Co. L’origine de cette étude provient de la nécessité de protéger leur surface par un revêtement dur et résistant comme, par exemple, le diamant NCD. Toutefois, le cobalt présent dans le carbure cémenté favorise la formation de graphite au niveau de l’interface avec le film de diamant, ce qui nuit à son adhérence. La méthode retenue afin d’isoler ce métal de la surface a été de réaliser des systèmes interfaciaux multicouches. Ces derniers sont composés d’une barrière de diffusion au cobalt en nitrure de tantale et/ou en nitrure de zirconium et d’une couche favorisant la germination du diamant en acier inoxydable ou en molybdène. Les protocoles de dépôt élaborés au cours de ce travail ont la particularité d’utiliser une polarisation négative et séquencée du substrat durant l’étape de croissance. Cela induit une morphologie originale au revêtement de diamant breveté sous le nom de PyrNCD (Brevet N° :FR0807181). Les objectifs de cette étude sont la compréhension de l’ensemble des mécanismes (influence de la solubilité du carbone sur la germination du diamant, l’effet de la polarisation sur le substrat revêtu et sur la croissance du diamant,…) intervenant durant le dépôt de diamant et l’optimisation du procédé. / The combination of good mechanical properties and low specific mass ensures the increasing use of composite materials to reduce the weight of mechanical structures. However, their machining induces premature and random wear of WC-Co cermet cutting-tools. The origin of this study comes from the necessity to protect cutting-tools surfaces by hard and resistant coatings like NCD diamond. Unfortunately, the cobalt found in these cemented carbides catalyses graphite formation at the interface with the diamond layer and harms the grip of the diamond film. The method used to isolate this metal from the surface has been to form interfacial multilayer systems. These are composed of a tantalum nitride and/or zirconium nitride diffusion barrier for cobalt and a layer promoting the diamond nucleation in molybdenum or stainless steel. The deposit protocols developed during this PhD work have the particularity of using a negative and sequenced substrate bias during the growth stage. This leads to an original morphology of the diamond coating which is patented under the name PyrNCD (International Patent N°: WO/2010/076423). The goal of this study is to understand all the mechanisms (like the impact of the carbon solubility on the diamond nucleation, the effects of negative bias on the coated substrate and the diamond growth,...) occurring during diamond deposition and process optimization.

Increasing interest in industrial and medical applications of carbon nanomaterial leads to the need to examine its interactions with living systems. Nanocrystalline diamond (NCD) films possess high mechanical and chemical stability which, together with its biocompatibility with human cells, enables applications in human body. Some of carbon nanoparticles possess strong antibacterial activity. In this work the effects of NCD with hydrogen, oxygen and fluorine termination deposited on glass and silicone on adhesion of gram-negative bacteria Escherichia coli K-12 in mineral medium is described and the impact of cultivation medium on effects of NCD films is compared. Prior the growth of the E. coli biofilm on NCD films, the method for quantification of biofilm using crystal violet staining and the method for biofilm cultivation in mineral medium were optimised. The properties of NCD film are independent on the base substrate. Hydrogen and fluorine terminated NCD films show antiadhesive properties only in mineral medium but not in complex medium. This is explained by formation of a conditioning film on the surface of the NCD film during cultivation in complex medium. On the other hand, O-NCD film supports bacterial adhesion in both cultivation media. Second part of this thesis is dedicated to carbon...

La technologie des microbolomètres est à ce jour la plus avancée pour l'imagerie IR non refroidie. Le LETI développe une technologie basée sur l'utilisation du silicium amorphe comme matériau thermistor. L'introduction d'un matériau alternatif doit permettre de poursuivre l'amélioration des performances. Cette étude considère une solution alternative à base de films minces d'oxydes nanocristallins. Deux procédés sont envisagés : le dépôt IBS et le dépôt MOCVD. L'étude des procédés ainsi que la caractérisation des matériaux ont permis la maîtrise et la compréhension des évolutions structurales et fonctionnelles mises en jeux. Des caractérisations électriques (résistivité, TCR, bruit en 1/f) sur dispositifs ont permis de débattre de l'intérêt de ces nouveaux matériaux. Une réflexion a été menée sur les relations microstructure-propriétés. / Microbolometers FPAs are nowadays the most advanced technology for uncooled IR imaging. Developments at CEA-LETI are based on the use of amorphous silicon as thermistor material. Introduction of an alternative material is necessary to keep on improving detectors performances. This study considersnanocrystalline oxides thin films as an alternative material. Two deposition techniques have been studied : IBS and MOCVD. Process studies as well as materials characterizations allowed us to control and understand the involved micro-structural evolutions. Electrical characterizations (resistivity, TCR, 1/f noise) on integrated devices were achievedin order to estimate the potential of these new materials. Microstructure-property relationships are also discussed.

O presente estudo está dividido em duas partes. A primeira parte está relacionada à preparação de pós de Cr3C2-25(Ni20Cr) nanoestruturados através do processo de moagem de alta energia, bem como à caracterização dos pós moídos e no estado como recebido. A análise dos dados obtidos nesta etapa do trabalho foi feita utilizando-se uma abordagem essencialmente teórica. A segunda parte deste estudo refere-se à produção e caracterização de revestimentos preparados com os pós de Cr3C2-25(Ni20Cr) nanoestruturados e como recebido. O comportamento destes revestimentos sob erosão-oxidação em alta temperatura foi comparado com base em uma abordagem de caráter mais tecnológico. O tamanho médio de cristalito do pó de Cr3C2-25(Ni20Cr) decresceu rapidamente de 145 nm para 50 nm nos estágios iniciais de moagem e, posteriormente, com o aumento do tempo de moagem, decresceu mais lentamente até atingir um estado estacionário para um tamanho de cristalito em torno de 10 nm. Este estado estacionário corresponde ao início do processo de recuperação dinâmica. A máxima deformação da rede cristalina (δ = 1,17%) foi observada para pós moídos por 16 horas, caracterizando um tamanho crítico de cristalito da ordem de 28 nm. Por outro lado, o parâmetro de rede atingiu um mínimo para pós moídos por 16 horas. Após atingir o tamanho crítico de cristalito, a densidade de discordâncias praticamente não mais varia (estado estacionário) e toda deformação plástica posteriormente introduzida no material é acomodada através de eventos que ocorrem nos contornos de grão, particularmente por meio do processo designado deslizamento de contorno de grão (grain boundary sliding). A energia de deformação armazenada na rede cristalina dos pós de Cr3C2-25(Ni20Cr) moídos com diferentes tempos de moagem foi determinada por meio de medidas da variação de entalpia. Estes resultados indicaram que a máxima variação de entalpia (ΔH = 722 mcal) também ocorreu para pós moídos por 16 horas. Analogamente, a máxima variação do calor específico (ΔCp = 0,278 cal/gK) ocorreu para pós moídos por 16 horas. As seguintes propriedades mecânicas dos revestimentos de Cr3C2-25(Ni20Cr), preparados utilizando-se o processo HVOF de aspersão térmica, foram determinadas: microdureza Vickers, módulo de Young e tenacidade à fratura. As propriedades dos revestimentos preparados com os pós nanoestruturados e como recebido foram comparadas. A dureza e o módulo de Young dos revestimentos preparados com os pós nanoestruturados foram aproximadamente 26% maiores que aqueles preparados com os pós como recebido. A tenacidade à fratura dos revestimentos nanoestruturados foi aproximadamente 36% maior do que o verificado para os revestimentos produzidos com pós no estado como recebido. A resistência à erosão-oxidação do revestimento produzido com o pó nanoestruturado foi em torno de 52% maior do que a do revestimento preparado com o pó no estado como recebido, a 800ºC. Ambos os revestimentos mostraram um aumento da taxa de erosão-oxidação para temperaturas acima de 450ºC. / This study is divided in two parts. The first part is about the preparation of nanostructured Cr3C2-25(Ni20Cr) powders by high energy milling followed by characterization of the milled and the as received powder. Analyses of some of the data obtained were done using a theoretical approach. The second part of this study is about the preparation and characterization of coatings prepared with the nanostructured as well as the as received Cr3C2-25(Ni20Cr) powders. The high temperature erosion-oxidation (E-O) behavior of the coatings prepared with the two types of powders has been compared based on a technological approach. The average crystallite size of the Cr3C2-25(Ni20Cr) powder decreased rapidly from 145 nm to 50 nm in the initial stages of milling and thereafter decreased slowly to a steady state value of around 10 nm with further increase in milling time. This steady state corresponds to the beginning of a dynamic recovery process. The maximum lattice strain (δ = 1,17%) was observed in powders milled for 16 hours, and this powders critical crystallite size was 28 nm. In contrast, the lattice parameter attained a minimum for powders milled for 16 hours. Upon reaching the critical crystallite size, the dislocation density attained a steady state regime and all plastic deformation introduced in the material there after was in the form of events occurring at the grain boundaries, due mainly to grain boundary sliding. The deformation energy stored in the crystal lattice of the Cr3C2-25(Ni20Cr) powders milled for different times was determined from enthalpy variation measurements. These results indicated that the maximum enthalpy variation (ΔH = 722 mcal) also occurred for powders milled for 16 hours. In a similar manner, the maximum specific heat variation (ΔCp = 0,278 cal/gK) occurred for powders milled for 16 hours. The following mechanical properties of Cr3C2-25(Ni20Cr) coatings prepared using the HVOF thermal spray process were determined: Vickers micro-hardness, the Young Modulus and the fracture toughness. The properties of the coatings prepared with the nanostructured and the as received powders were compared. The hardness and Young Modulus of the coatings prepared with nanostructured powders were approximately 26% higher than that of the coatings prepared with as received powders. The fracture toughness of the nanostructured coating was 36% higher. The erosion-oxidation resistance of the coating produced with the nanostructured powder was around 52% higher than that of the coating prepared with the as received powders at 800 ºC. The E-O wastage of both types of coatings increased with temperature beyond 450 ºC.

O bagaço de cana-de-açúcar é um abundante coproduto obtido a partir da produção convencional de etanol. No entanto, o bagaço vem se mostrando como uma importante fonte para a produção de etanol de segunda geração. No primeiro capítulo da tese é apresentado um estudo referente à distribuição espacial dos compostos na matriz de bagaço de cana-de-açúcar. A investigação foi realizada utilizando microscopia de fluorescência confocal e espectroscopia por excitação com um e dois fótons. Imagens de autofluorescência em combinação com as medidas de fluorescência e tempos de vida forneceram uma gama de informações necessárias para a caracterização de amostras de bagaço. Além disso, a técnica permite o acompanhamento de processos relacionados com a remoção de lignina. A nanocelulose cristalina (NCC) é um material promissor devido as suas propriedades intrínsecas, tais como seu formato alongado, medindo de 1 a 100 nm de diâmetro e seu comprimento variando de algumas dezenas a centenas de nanômetros. No capítulo 2, a nanocelulose cristalina foi obtida através da hidrólise da celulose cristalina (de Avicel®) com ácido sulfúrico. Em seguida, o material foi caracterizado por técnicas de microscopia SEM e TEM, confirmando a morfologia em forma de haste e a estrutura de tamanho nanométrico. A microscopia de campo largo convencional foi utilizada como ferramenta na caracterização da NCC dispersa em soluções poliméricas de PVA e PVP. A última parte do capítulo 2 descreve a caracterização de estruturas de NCC usando a microscopia de super-resolução de fluorescência STED (depleção de emissão estimulada). As imagens mostraram uma resolução de até 50 nm, permitindo a comparação com resultados de TEM e AFM. No capítulo 3, a nanocelulose cristalina foi covalentemente marcada com o corante ATTO-532, através da chamada reação \"click\". As propriedades relacionadas com o coeficiente de difusão da NCC foram determinadas por espectroscopia de correlação de fluorescência (FCS). Em uma etapa posterior, a NCC foi colocada em diferentes soluções do polímero PEG, contendo quantidades diferentes. As propriedades dinâmicas foram analisadas por métodos de FCS e WFM. O uso de técnicas de espectroscopia e microscopia revelou detalhes relacionados à heterogeneidade das dispersões de NCC, as quais estão relacionadas com as propriedades hidrofílicas e hidrofóbicas das soluções poliméricas. / The sugarcane bagasse is an abundant co-product obtained from the conventional production of ethanol. However, sugarcane bagasse has been proving to be an important source to the production of second-generation ethanol. In the first chapter, the spatial distribution of compounds in the sugarcane bagasse matrix was investigated by confocal fluorescence microscopy and spectroscopy with one and two-photon excitation. Autofluorescence images in combination to spectral emission and lifetime measurements provided a tool for the characterization of natural bagasse samples. Moreover, the technique allows the following of processes related to the lignin removal. Nanocrystalline cellulose (NCC) is a promisor material because of its properties, such as rod-shape with 1-100 nm in diameter, and tens to hundreds of nanometres in length. In the Chapter 2, NCC was obtained via sulphuric acid hydrolysis from Avicel®. Afterwards, the material was characterized by classic electronic microscopy SEM and TEM, confirming the rod-shaped morphology and the nano-sized structure. Conventional wide field microscopy was used as fluorescence microscopy tool in the characterization of NCC, when dispersed in polymeric solutions of PVA and PVP. The last part of the chapter 2 describes the characterization of NCC structures by using the super-resolution fluorescence microscopy STED (Stimulated Emission Depletion). The STED images showed a resolution down to 50 nm, allowing the comparison with TEM and AFM microscopy results. In the Chapter 3, the NCC was covalently labelled, by a click-chemistry reaction, with the ATTO-532 dye. Properties related to diffusion coefficient of NCC were determined by Fluorescence Correlation Spectroscopy (FCS) method. Afterwards, NCC was placed into a solution of PEG, containing different amounts polymer. The dynamic properties were evaluated by FCS and WFM methods. The use of spectroscopy and microscopy imaging techniques revealed heterogeneity details of NCC dispersions, which are related to the hydrophilic and hydrophobic properties of the polymer solution. A better understanding of polymer systems is achieved by investigation of diffusion properties, that allows the comprehension of rheological parameters, and, consequently, in polymer processing and assembly of plastics, films, and fibres. In the Chapter 4 is presented a study where fluorescence correlation spectroscopy (FCS) and wide-field fluorescence microscopy (WFM) were used to follow changes in the diffusion coefficients of growing polymer chains, during the controlled radical polymerization process. Linear and star-shaped polystyrene were grown via nitroxide-mediated polymerization (NMP) from alkoxyamine-based initiators containing a highly fluorescent perylene diimide moiety. This study demonstrates that direct investigation of heterogeneity emerging during a controlled radical polymerization process by means of fluorescence of single-molecule chain initiator allows unravelling information related to the diffusion processes of the growing polymer chain.

Currently available solid lubricants only perform well under a limited range of environmental conditions. Unlike them, oxides are thermodynamically stable and relatively inert over a broad range of temperatures and environments. However, conventional oxides are brittle at normal temperatures; exhibiting significant plasticity only at high temperatures (>0.5Tmelting). This prevents oxides' use in tribological applications at low temperatures. If oxides can be made lubricious at low temperatures, they would be excellent solid lubricants for a wide range of conditions. Atomic layer deposition (ALD) is a growth technique capable of depositing highly uniform and conformal films in challenging applications that have buried surfaces and high-aspect-ratio features such as microelectromechanical (MEMS) devices where the need for robust solid lubricants is sometimes necessary. This dissertation investigates the surface and subsurface characteristics of ALD-grown ZnO/Al2O3 nanolaminates and ZrO2 monofilms before and after sliding at room temperature. Significant enhancement in friction and wear performance was observed for some films. HRSEM/FIB, HRTEM and ancillary techniques (i.e. SAED, EELS) were used to determine the mechanisms responsible for this enhancement. Contributory characteristics and energy dissipation modes were identified that promote low-temperature lubricity in both material systems.

L'objectif de cette thèse est de contribuer à la compréhension des propriétés optoélectroniques des couches minces de silicium hydrogénée, une étude détaillée a été effectuée. Les échantillons ont été déposés par 13,56 MHz PECVD (Plasma Enhanced Chemical Vapor Deposition) à partir du silane dilué avec l'argon (96 %). La température du substrat a été fixée à 200 °C. L'influence des paramètres de dépôts sur les propriétés optiques des échantillons a été étudiée par spectroscopie UV -Vis -NIR. L'évolution structurelle a été étudiée par spectroscopie Raman, TEM, AFM, FTIR et par diffraction des rayons X (XRD). La déposition des couches intrinsèques a été faite dans cette étude dans le but d'obtenir la transition de l'état amorphe à la phase cristalline des matériaux. La pression de dépôt varie de 400 mTorr à 1400 mTorr et la puissance de 50 à 250 W. La caractérisation structurelle montre qu'au-delà de 160 W, nous avons observé une transition amorphe nanocristalline, avec une augmentation de la fraction cristalline en augmentant la puissance et la pression. Les couches sont déposées avec des vitesses de dépôt relativement élevées (3.5 - 8 Å/s), ce qui est très souhaitable pour la fabrication des cellules photovoltaïques. La vitesse de dépôt augmente avec l'augmentation de la puissance et de la pression. Des différentes fractions cristallines et tailles des cristallites ont été obtenues en contrôlant la pression et la puissance. Ces modifications de structure ont été corrélées avec la variation des propriétés optiques et électriques des couches minces déposées. / The main objective of this thesis is to contribute to the understanding of the optoelectronics properties of hydrogenated nanocrystalline silicon thin films, a detailed study has been conducted. The samples were deposited by 13.56 MHz PECVD (Plasma Enhanced Chemical Vapor Deposition) of silane argon mixture. The argon dilution of silane for all samples studied was 96% by volume. The substrate temperature was fixed at 200 °C. The influence of depositions parameters on optical proprieties of samples was studied by UV-Vis-NIR spectroscopy. The structural evolution was studied by Raman spectroscopy, TEM, AFM, FTIR and X-ray diffraction (XRD). Intrinsic-layer samples depositions were made in this experiment in order to obtain the transition from the amorphous to crystalline phase materials. The deposition pressure varied from 400 mTorr to 1400 mTorr and the RF power from 50 to 250 W. The structural evolution studies show that beyond 160 W, we observed an amorphous-nanocrystalline transition, with an increase in crystalline fraction by increasing RF power and working pressure. Films near the amorphous to nanocrystalline transition region are grown at reasonably high deposition rates (3.5- 8 Å/s), which are highly desirable for the fabrication of cost effective devices. The deposition rate increases with increasing RF power and process pressure. Different crystalline fractions and crystallite size can be achieved by controlling the process pressure and RF power. These structural changes are well correlated to the variation of optical and electrical proprieties of the thin films.

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