Biomateriais metálicos devem apresentar uma combinação de propriedades como resistência à corrosão, biocompatibilidade e resistência mecânica. Os aços inoxidáveis austeníticos, especialmente do tipo AISI 316L, aliam estas propriedades com a possibilidade de fabricação a um baixo custo. No entanto, são susceptíveis à corrosão nos fluidos fisiológicos e seus produtos de corrosão podem causar reações alérgicas ou infecciosas nos tecidos vizinhos ao implante. No presente trabalho, a aplicação de revestimentos obtidos por processos de deposição física de vapor (PVD) sobre um aço inoxidável austenítico do tipo AISI 316L foi realizada a fim de aumentar sua resistência à corrosão e biocompatibilidade. Os filmes depositados foram de nitreto de titânio (TiN), carbonitreto de titânio (TiCN) e de carbono tipo diamante (DLC). Estes materiais têm alta dureza e resistência ao desgaste, além de biocompatibilidade intrínseca, características altamente desejáveis para aplicações biomédicas. A caracterização do comportamento eletroquímico do aço com os três tipos de revestimentos mostrou que a presença de defeitos na superfície das camadas depositadas exerce uma influência negativa sobre a resistência à corrosão do substrato. A presença dos defeitos foi evidenciada por microscopia eletrônica de varredura. Foi proposto um mecanismo, com base nos dados obtidos por espectroscopia de impedância eletroquímica, para explicar a evolução do comportamento eletroquímico do aço com os diferentes revestimentos ao longo do tempo de imersão. Foram também empregados dois tratamentos de passivação da superfície do aço em soluções de ácido sulfúrico e ácido nítrico, a fim de aumentar a resistência à corrosão do substrato. Os resultados indicaram que os tratamentos utilizados não foram eficientes para melhorar esta característica, mas podem ser modificados visando um desempenho superior. As propriedades eletrônicas dos filmes passivos formados, tanto sobre o aço sem tratamento de passivação como sobre o aço passivado, foram estudadas utilizando a abordagem de Mott-Schottky. Os filmes apresentaram um caráter duplex, mostrando comportamento de um semicondutor altamente dopado acima e abaixo do potencial de banda plana. A concentração de dopantes no filme passivo foi associada à resistência à corrosão do material. Os três revestimentos PVD investigados apresentaram comportamento não citotóxico. Considerando a diminuição do coeficiente de atrito do aço 316L, os revestimentos de TiCN e o DLC foram os mais eficientes. Estas características, aliadas ao fator custo, sugerem que a aplicação comercial destes materiais sobre implantes ortopédicos pode ser viável. No entanto, a resistência à corrosão, conforme a avaliação realizada no presente estudo, não foi adequada quando comparada ao desempenho do aço sem nenhum tipo de revestimento. Ao final do texto, são apresentadas algumas sugestões a fim de conseguir um desempenho superior para a capacidade protetora dos revestimentos PVD. / Metallic biomaterials must present a combination of properties such as corrosion resistance, biocompatibility and mechanical resistance. Austenitic stainless steels, especially AISI 316L combine these properties with the easy of fabrication at low cost. However, they are prone to corrosion in physiological solutions. Furthermore, their corrosion products may lead to infectious ou allergenic reactions in the tissues around the implant device. In the present work, coatings produced by physical vapour deposition (PVD) methods have been applied on the surface of a 316L stainless steel to increase its corrosion resistance and biocompatibility. Three thin films were tested: titanium nitride (TiN), titanium carbonitride (TiCN) and diamond-like carbon (DLC). These materials present high hardness, wear resistance and intrinsic biocompatibility that are key features when considering biomedical applications. The characterization of the electrochemical behavior of the stainless steel coated with the three different films showed that the presence of surface defects are deleterious to the corrosion resistance of the substrate. These defects were observed using scanning electron microscopy. The evolution of the electrochemical behavior of the coated steel was explained through a mechanism based on the experimental results obtained using electrochemical impedance spectroscopy. Two different passivation treatments were carried out on the stainless steel surface, either in sulfuric or nitric acid solutions, to increase its corrosion resistance. The results suggested que these treatments were not efficient, but may be modified to improve its performance. The electronic properties of the passive films of the non-passivated and passivated stainless steel were studied using the Mott-Schottky approach. The films presented a duplex character. Below the flatband potential the behavior is typical of a highly doped type-p semiconductor. Above the flatband potential is typical of a highly doped type-n semiconductor. The doping concentration in the passive film was determined and associated with the corrosion resistance of the substrate. All PVD coatings investigated showed non-cytotoxic behavior. DLC and TiCN coatings decreased the friction coefficient of the stainless steel substrate. These properties allied with the stainless steel low cost recommend their commercial use for implants materials purposes. Nevertheless the corrosion resistance presented by the coated-steel was inferior to that of the bare steel and should be improved. At the end of the present text, some suggestions are proposed in order to improve the corrosion protection performance of the PVD coatings.

Afin de faire face à la demande croissante de mémoires de plus en plus performantes dans les systèmes informatiques, de nouvelles technologies se sont développées. Parmi elles, les mémoires résistives à changement de phase (ou PCM pour Phase-Change Memory) ont des propriétés et une maturité suffisante pour développer les nouvelles mémoires SCM (pour Storage Class Memory) comme en témoigne la récente commercialisation des produits Optane par la firme INTEL®. Néanmoins, la consommation énergétique des PCM lors de leur programmation reste élevée, ce qui limite leurs performances. L’intégration de super-réseaux (GeTe)2/(Sb2Te3)m dans des mémoires dites iPCM (pour interfacial Phase-Change Memory) est une des voies les plus prometteuse pour permettre une diminution significative des courants de programmation. Cependant, le mécanisme de transition des iPCM et la structure du matériau dans ses deux états de résistances sont encore méconnus. Dans ce contexte, l’objectif de cette thèse est d’élaborer des super-réseaux (GeTe)2/(Sb2Te3)m (m=1,2,4 et 8) cristallins, de déterminer leur structure puis de les intégrer dans des dispositifs mémoires. La pulvérisation cathodique alternée des matériaux GeTe et Sb2Te3 dans un équipement industriel de dépôt est utilisée pour effectuer l’épitaxie van der Waals de ces super-réseaux. Une optimisation du procédé par l’ajout d’une cible de Te en co-pulvérisation avec la cible de Sb2Te3 montre l’obtention de super-réseaux stœchiométriques présentant la périodicité souhaitée, ainsi qu’une orientation des plans cristallins (0 0 l) parallèle à la surface du substrat. Une description de l’ordre atomique local des super-réseaux ainsi optimisés est ensuite menée par l’étude d’images HAADF-STEM couplée à des simulations. Celle-ci révèle un phénomène d’inter-diffusion entre les couches de GeTe et de Sb2Te3 déposées aboutissant à la formation locale de GexSbyTez rhomboédriques, des mesures quantitatives de l’occupation des plans atomiques en Ge/Sb confirment aussi le phénomène. De plus, un modèle de structure à longue distance de ces super-réseaux considérant un empilement aléatoire de blocs cristallins permet la simulation des courbes de diffraction obtenues expérimentalement. Enfin, les premières intégrations des super-réseaux (GeTe)2/(Sb2Te3)m dans des dispositifs mémoires mettent en évidence une réduction importante des courants de programmation jusqu’à 4 fois inférieurs à une PCM et avec une endurance dépassant les 10 millions cycles. / In order to satisfy the demand for more and more efficient memory in computer systems, new technologies have been developed. Among the latter resistive phase-change memories (PCM) exhibit capacities and sufficient maturity to achieve the so-called new SCM (for Storage Class Memory) devices as evidenced by the recent commercialization of Optane products by INTEL®. Nevertheless, PCM still require strong electrical consumption limiting their performance. Integration of (GeTe)2/(Sb2Te3)m superlattices in so-called iPCM (for interfacial Phase Change Memory) was shown to permit a significant decrease in programming currents. However, the switching mechanism of this memory and the structure of the material in its two resistance states are still under debate. The aim of this thesis is therefore to deposit crystalline (GeTe)2/(Sb2Te3)m (m=1,2,4 et 8) superlattices, to determine their structure and to integrate them into memory devices. GeTe and Sb2Te3 materials are alternately deposited by means of sputtering in an industrial deposition tool to perform van der Waals epitaxy of these superlattices. Stoichiometric superlattices with the desired periodicity and with an orientation of the (0 0 l) crystalline planes parallel to the surface of the substrate are obtained by innovative co-sputtering of Sb2Te3 and Te targets during Sb2Te3 deposition. A description of the local atomic order of superlattices is then carried out by studying HAADF-STEM images coupled to simulations. Intermixing between GeTe and Sb2Te3 deposited layers is thus revealed, leading to the local formation of rhombohedral GexSbyTez. Quantitative measurements of the Ge/Sb atomic plans occupation in further confirm the phenomenon. A long-range order structural model of superlattices by means of random stacking of crystalline blocks allows the simulation of experimental diffraction curves. Finally, the first integrations of (GeTe)2/(Sb2Te3)m (with m=1,2,4 et 8) superlattices in devices demonstrate a programming current up to 4 times lower than a PCM reference with an endurance exceeding 10 millions cycles.

Les capteurs de gaz électrochimiques sont l’un des moyens les plus directs pour convertir la composition chimique d’un gaz en signal électrique mesurable. A ce titre, ils ont été largement étudiés et font aujourd’hui partie des solutions de détection les plus courantes. Toutefois, ils sont souvent basés sur un électrolyte YSZ, ce qui implique des températures de travail élevées (600°C).Afin de pouvoir réaliser une cellule de capteur fonctionnant à plus basse température (300°C), les conditions de dépôt des électrolytes Bi4V2O11 et BITAVOX (Bi2TaxV1-xO5,5) par pulvérisation cathodique magnétron en conditions réactives (PVD) ont été étudiées. L’impact de l’épaisseur des films ainsi que celui du taux de substitution du vanadium par le tantale sur les propriétés structurale et de conduction ont été déterminés.Par la suite, deux types de cellules ont été réalisés en déposant des électrodes à la surface de l’électrolyte par PVD. Le premier utilise des électrodes de platine dense et de nanofils de LASCO (La1-x-yAgxSryCoO3). Néanmoins, le comportement de ce capteur aux plus basses températures est assez complexe. Aussi, des électrodes de platine et d’or ont ensuite été étudiées, amenant à une réponse plus simple et apparaissant dès 200°C. / Electrochemical sensors are one of the most direct ways to convert the chemical composition of a gas into measurable electric signals. As such, they have been widely investigated and are now one of the most common detection solutions. However, they are often based on YSZ electrolyte, which implies high working temperatures (600°C).In order to build a sensor cell which could operate at lower temperature (300°C), deposition parameters of Bi4V2O11 and BITAVOX (Bi2TaxV1-xO5.5) electrolytes by the mean of reactive magnetron sputtering (PVD) were investigated. The impact of film thickness and that of tantalum substitution rate on the V site on structural and conduction properties were determined.Then, two different kinds of cells were realised by depositing electrodes onto the electrolyte surface. The first one used dense platinum and LASCO (La1-x-yAgxSryCoO3) nanowires electrodes. Nevertheless, this sensor exhibited a rather complex behaviour at lowest temperatures. Then, gold and platinum electrodes were investigated, which led to a more simple response of the sensor. Furthermore, this response started at 200°C.

Nous étudions les mécanismes d’endommagement dus à l’érosion pluie sur des matériaux massifs et sur des matériaux revêtus. Pour cela, un banc d’essais spécifique a permis de mener des recherches en laboratoire. Le principe de l’essai repose sur l’émission de jets à haute vitesse et à haute fréquence.L’étude des matériaux massifs met en évidence un mécanisme de propagation de fissures par fatigue qui aboutit à des pertes de matière. Ces mêmes endommagements ont été observés sur des échantillons usés en service. Il a été confirmé que la dureté augmente la résistance à l’érosion pluie des matériaux métalliques.L’étude des revêtements s’est focalisée sur 2 technologies, à savoir la pulvérisation cathodique magnétron, qui est un procédé de déposition phase vapeur, et la projection thermique sous flamme supersonique. Les revêtements obtenus par projection thermique (dont l’épaisseur était supérieure à 200 μm), se sont révélés moins résistants à cause d’un manque d’adhérence ou de la présence de défauts au sein du matériau. Les revêtements obtenus par PVD (dont l’épaisseur était inférieure à 30 μm) ont permis d’obtenir des gains de résistance significatifs. Dans tous les cas, quel que soit la technologie utilisée, l’adhérence du revêtement s’est révélé être un paramètre critique en ce qui concerne la résistance de la surface à l’érosion pluie. Enfin, une simulation numérique en dynamique a permis d’étudier les champs de contraintes dans des feuillets métalliques, et ce, en faisant varier leurs épaisseurs, les matériaux qui les composent, et la vitesse d’impact. Les résultats de la simulation tendent à prouver que la propagation des ondes de contraintes dans le matériau peut entrainer des phénomènes de sur-contraintes dans les feuillets les plus fins à cause de la réflexion des ondes sur la face antérieure de la plaque. / The study deals with the rain erosion mechanisms of both bulk and coated materials. For that purpose, a specific test bench has been built, enabling laboratory research. The principle of the test is based on the emission of high-speed water jets at high frequency.Studying bulk materials confirmed the positive influence of hardness on rain erosion resistance for metallic materials. The mechanism found responsible for material losses is the propagation of fatigue cracks. These fatigue damages were also observed on in-service worn out samples.The analysis of coated materials focused on two covering technologies, namely physical vapor magnetron sputtering deposition (Magnetron PVD) and high velocity oxy-fuel coating spraying (HVOF). The coatings obtained by HVOF (> 200μm) weren’t resistant enough due to lack of adhesion and/or due to specific defects within the material. The coatings obtained by PVD (< 30μm) have yielded to significant improvements on the surface resistance. However, the adhesion of the coating appeared as a critical parameter for the rain erosion resistance.Finally, a numerical simulation has been designed to study dynamic stress fields in metal sheets. Moreover the model allowed the sheets thicknesses, the materials, and the speed of impact to vary. The simulation showed that the propagation of stress waves in the material may cause over-stresses phenomena in the thinner sheets, due to the reflection waves on the back side of the plate.

Afin d’obtenir des matériaux aux caractéristiques mécaniques, tribologiques et thermiques améliorées, nous avons élaboré des revêtements nanocomposites à base de TiN en utilisant une technique de dépôt physique en phase vapeur. Ces matériaux aux caractéristiques spécifiques peuvent être exploités pour le surfaçage d’outils de coupe de très haute dureté. En ajustant les processus d’élaboration dont dépendent la microstructure et la microchimie des revêtements, il est possible de contrôler les propriétés de ces matériaux. Cette thèse présente les résultats obtenus sur les trois systèmes de revêtement que sont Ti-Al-N, Ti-Al-Y-N et Ti-Si-N, configurés soit en réseaux superposés multicouche soit en nanocomposites. L’accent est mis sur l’étude systématique de la dureté et de la résistance à l’usure et à l'oxydation en fonction des paramètres de dépôt. En combinant la diffraction des rayons X et la microscopie électronique à transmission avec des tests physico-mécaniques sur une large gamme de configurations de revêtement, on établit une matrice processus-performance prédictive permettant de guider la fabrication de surfaces durcies. / TiN-based nanocomposite coatings were prepared using physical vapor deposition to deliver enhanced mechanical, tribological and thermal characters that can be exploited for superhard cutting tool surfacing. These properties are controlled by tailoring processing methods to tune the microstructure and microchemistry. This thesis examined three coating systems, which are Ti-Al-N, Ti-Al-Y-N and Ti-Si-N, configured variously as multilayer superlattices and nanocomposites to comprehensively correlate hardness, wear resistance and oxidation resistance with deposition parameters. Combining X-ray diffraction and transmission electron microscopy with physical-mechanical testing, over a wide range of coating configurations, enabled construction of a predictive process-performance matrix to guide the fabrication of hardened surfaces.In multilayer TiN/TixAl1-xN coatings prepared by cathodic arc deposition, the mechanical properties were controlled by the layer period that was adjusted by varying substrate rotation speed. A hardness of 39 ± 4 GPa was achieved for a superlattice period of 13 nm, where the coatings contain columnar <111> textured rock salt – type crystals connected by low-angle grain boundaries. When yttrium was introduced to the multilayers, by adding a Y - metal target powered by DC magnetron sputtering, the morphology changed from columnar to acicular grains with smaller grain size. Specifically, by fixing the period at 5.5 nm and incorporating Y from 0 to 2.4 at% the grain size decreased (from 100-200 nm to 20-30 nm) and hardness increased (from 29 ± 7 GPa to 41 ± 3 GPa). The improved performance was a consequence of solid solution hardening that arises from the misfit strain field introduced by Y (element atomic radii 2.12 Å) substitution for Ti (1.76 Å) or Al (1.18 Å), and a nanosize effect, where finer grains result in a greater volume fraction of grain boundaries that block dislocation movement. Higher Y additions also retard oxidation as high temperature (800 ºC) annealing generates Ti2O3, rather than TiO2 as in Y-free coatings, and also affects Al oxidation. Adhesion and wear resistance were not compromised by higher Y contents demonstrating that TiN/TixAl1-xN coatings can enhance mechanical properties and thermal stability. Notably, this work employed a pure Y target, instead of a Ti-Al-Y alloy target, and substrate holder rotation speed was the critical parameter, where faster substrate rotation leads to smaller periods and more uniform Y distribution. However, an Y-rich layer became progressively thicker at slower rotation with the period increasing from 5.5 nm to 24 nm. These Y-rich regions seeded crystal nucleation that reduced coherency at layer interfaces and grain boundaries to significantly degrade mechanical properties (41 ± 3 GPa to 30 ± 5 GPa). Therefore, the period and Y content work in tandem in multilayered TiN/TixAl1-xN coatings and the optimized Y content was to be 2.4 at% at a period of 5.5 nm.Nanocrystallite TiN / amorphous (a)-Si3N4 nanocomposites were fabricated by high power impulse magnetron sputtering. The introduction of silicon by controlling the Si target current can be used to modify the coating structure, tailor mechanical properties, improve wear resistance and passivate oxidation. Smaller crystal sizes promoted at higher Si content lead to TiN / amorphous (a)-Si3N4 nanocomposites, with ~10 at% Si/(Si+Ti) yielding maximum hardness (41 ± 3 GPa). Compared to TiN, Ti0.903Si0.097N showed enhanced resistance to oxidation and wear resistance, however, the TiN crystallites were not completely encapsulated by a-Si3N4 intergranular films and further optimization of the structure and property relationship can be realised.

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Agradecemos a compreensão. on 2016-11-10T15:50:45Z (GMT) / Submitted by ANDERSON FIGUEIREDO DA COSTA null (and.kairos@hotmail.com) on 2016-11-22T17:09:03Z No. of bitstreams: 1 Dissertação 20161104 - Versão Final Corrigida.pdf: 5558976 bytes, checksum: 402eb9e3734833ebc7ccebf113844b8e (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-11-23T17:41:31Z (GMT) No. of bitstreams: 1 costa_af_me_guara.pdf: 5558976 bytes, checksum: 402eb9e3734833ebc7ccebf113844b8e (MD5) / Made available in DSpace on 2016-11-23T17:41:31Z (GMT). No. of bitstreams: 1 costa_af_me_guara.pdf: 5558976 bytes, checksum: 402eb9e3734833ebc7ccebf113844b8e (MD5) Previous issue date: 16-09-08 / Com o atual avanço de propriedades dos materiais, novas alternativas estão sendo buscadas para manufaturas desses materiais. Entre os processos, a usinagem se caracteriza por ser um processo que emprega milhões de pessoas. Entretanto para alcançar tais objetivos melhorias nas propriedades das ferramentas se faz necessária. Neste seguimento, os revestimentos vêm apresentando avanços significativos, como pode-se destacar o revestimento por CVD (deposição química a vapor) que permite que a ferramenta seja empregada nas temperaturas em torno de 1200ºC. Nesta mesma linha vale destacar o revestimento por PVD (deposição física a vapor) normalmente em uma única camada, o qual permite que a aresta de corte seja positiva, possa trabalhar com menor esforço de corte, e em temperatura aproximadamente em 700ºC. Este trabalho tem como objetivo analisar comparativamente o desempenho de ferramentas de metal duro revestidas pelo processo CVD e PVD no torneamento do aço ABNT 8620 sem uso de fluido de corte. Foram utilizadas duas pastilhas de metal duro revestidas pelo processo de PVD e CVD, com mesma geometria para efeito comparativo. A pastilha revestida por PVD tem espessura do revestimento de 3µm, enquanto que a pastilha revestida por CVD tem espessura do revestimento de 16µm. As pastilhas revestidas foram caracterizadas quanto a composição química dos elementos de revestimentos utilizando um microscópio eletrônico de varredura pela técnica de linescan e mapping. Posteriormente as ferramentas foram aplicadas ao torneamento nas velocidades de corte (Vc) entre 350 a 500m/min, avanço (f) de 0,20mm/rot e profundidade de corte (ap) de 1,00mm, utilizando um torno da marca ROMI, modelo GL240M. As caracterizações foram realizadas com uso de um microscópio óptico, microscópio eletrônico de varredura e um rugosímetro. Os resultados demonstraram que a ferramenta revestida pelo processo CVD apresenta um melhor rendimento, quando comparado ao processo PVD, este fato ocorreu porque a ferramenta revestida pelo processo CVD apresenta um revestimento multicamadas, possuindo um aporte térmico mais elevado, suportando assim, temperaturas de corte mais elevadas durante a usinagem e promovendo um menor desgaste de flanco e de superfície de saída. Portanto, este trabalho demonstra que para uso em uma indústria que torneia o aço ABNT 8620, as ferramentas revestidas com CVD apresentam melhor desempenho, levando a um menor consumo de pastilhas e uma expressiva redução de custos. / With the current advancement of material properties, new alternatives are being sought for manufacturing these materials. Among the processes, machining is characterized as a process that employs millions of people. However to achieve such goals improvements in the tools properties is necessary. In this follow-up, the coatings have shown significant advances, as can highlight the coating by CVD (chemical vapor deposition) that allows the tool to be used at temperatures around 1200°C. In the same line it is worth highlighting the coating by PVD (physical vapor deposition) usually in a single layer, which allows the cutting edge is positive, can work with less shear stress, and temperature approximately 700°C. This study aims at comparing the performance of carbide tools coated by the CVD process and PVD in the steel turning ABNT 8620 without the use of cutting fluid. We used two carbide inserts coated by the PVD and CVD process, with the same geometry for comparison purposes. The tablet is coated by PVD coating thickness of 3μm, while the tablet is coated by CVD coating thickness of 16μm. The coated tablets were characterized as the chemical composition of coatings elements using a scanning electron microscope for linescan technique and mapping. Subsequently the tools were applied to turning the cutting speed (Vc) between 350 to 500 m/min, feed (f) 0.20 mm/rev and depth of cut (ap) of 1.00mm using a lathe ROMI mark, GL240M model. The characterizations were carried out using an optical microscope, scanning electron microscope and roughness. The results demonstrated that the tool coated by the CVD process has a better performance when compared to PVD this occurred because the tool coated by the CVD process has a multilayer coating having a higher heat input, supporting thus cutting temperatures over high during machining and promote a smaller flank wear and output surface. Therefore, this work shows that for use in an industry that sidesteps steel ABNT 8620, tools coated with CVD have better performance, leading to lower consumption of pellets and a significant cost reduction.

Biomateriais metálicos devem apresentar uma combinação de propriedades como resistência à corrosão, biocompatibilidade e resistência mecânica. Os aços inoxidáveis austeníticos, especialmente do tipo AISI 316L, aliam estas propriedades com a possibilidade de fabricação a um baixo custo. No entanto, são susceptíveis à corrosão nos fluidos fisiológicos e seus produtos de corrosão podem causar reações alérgicas ou infecciosas nos tecidos vizinhos ao implante. No presente trabalho, a aplicação de revestimentos obtidos por processos de deposição física de vapor (PVD) sobre um aço inoxidável austenítico do tipo AISI 316L foi realizada a fim de aumentar sua resistência à corrosão e biocompatibilidade. Os filmes depositados foram de nitreto de titânio (TiN), carbonitreto de titânio (TiCN) e de carbono tipo diamante (DLC). Estes materiais têm alta dureza e resistência ao desgaste, além de biocompatibilidade intrínseca, características altamente desejáveis para aplicações biomédicas. A caracterização do comportamento eletroquímico do aço com os três tipos de revestimentos mostrou que a presença de defeitos na superfície das camadas depositadas exerce uma influência negativa sobre a resistência à corrosão do substrato. A presença dos defeitos foi evidenciada por microscopia eletrônica de varredura. Foi proposto um mecanismo, com base nos dados obtidos por espectroscopia de impedância eletroquímica, para explicar a evolução do comportamento eletroquímico do aço com os diferentes revestimentos ao longo do tempo de imersão. Foram também empregados dois tratamentos de passivação da superfície do aço em soluções de ácido sulfúrico e ácido nítrico, a fim de aumentar a resistência à corrosão do substrato. Os resultados indicaram que os tratamentos utilizados não foram eficientes para melhorar esta característica, mas podem ser modificados visando um desempenho superior. As propriedades eletrônicas dos filmes passivos formados, tanto sobre o aço sem tratamento de passivação como sobre o aço passivado, foram estudadas utilizando a abordagem de Mott-Schottky. Os filmes apresentaram um caráter duplex, mostrando comportamento de um semicondutor altamente dopado acima e abaixo do potencial de banda plana. A concentração de dopantes no filme passivo foi associada à resistência à corrosão do material. Os três revestimentos PVD investigados apresentaram comportamento não citotóxico. Considerando a diminuição do coeficiente de atrito do aço 316L, os revestimentos de TiCN e o DLC foram os mais eficientes. Estas características, aliadas ao fator custo, sugerem que a aplicação comercial destes materiais sobre implantes ortopédicos pode ser viável. No entanto, a resistência à corrosão, conforme a avaliação realizada no presente estudo, não foi adequada quando comparada ao desempenho do aço sem nenhum tipo de revestimento. Ao final do texto, são apresentadas algumas sugestões a fim de conseguir um desempenho superior para a capacidade protetora dos revestimentos PVD. / Metallic biomaterials must present a combination of properties such as corrosion resistance, biocompatibility and mechanical resistance. Austenitic stainless steels, especially AISI 316L combine these properties with the easy of fabrication at low cost. However, they are prone to corrosion in physiological solutions. Furthermore, their corrosion products may lead to infectious ou allergenic reactions in the tissues around the implant device. In the present work, coatings produced by physical vapour deposition (PVD) methods have been applied on the surface of a 316L stainless steel to increase its corrosion resistance and biocompatibility. Three thin films were tested: titanium nitride (TiN), titanium carbonitride (TiCN) and diamond-like carbon (DLC). These materials present high hardness, wear resistance and intrinsic biocompatibility that are key features when considering biomedical applications. The characterization of the electrochemical behavior of the stainless steel coated with the three different films showed that the presence of surface defects are deleterious to the corrosion resistance of the substrate. These defects were observed using scanning electron microscopy. The evolution of the electrochemical behavior of the coated steel was explained through a mechanism based on the experimental results obtained using electrochemical impedance spectroscopy. Two different passivation treatments were carried out on the stainless steel surface, either in sulfuric or nitric acid solutions, to increase its corrosion resistance. The results suggested que these treatments were not efficient, but may be modified to improve its performance. The electronic properties of the passive films of the non-passivated and passivated stainless steel were studied using the Mott-Schottky approach. The films presented a duplex character. Below the flatband potential the behavior is typical of a highly doped type-p semiconductor. Above the flatband potential is typical of a highly doped type-n semiconductor. The doping concentration in the passive film was determined and associated with the corrosion resistance of the substrate. All PVD coatings investigated showed non-cytotoxic behavior. DLC and TiCN coatings decreased the friction coefficient of the stainless steel substrate. These properties allied with the stainless steel low cost recommend their commercial use for implants materials purposes. Nevertheless the corrosion resistance presented by the coated-steel was inferior to that of the bare steel and should be improved. At the end of the present text, some suggestions are proposed in order to improve the corrosion protection performance of the PVD coatings.

Élaborer et optimiser des nouveaux matériaux restent toujours parmi les enjeux liés à l'amélioration de la performance de la durabilité des matériaux.Le domaine des traitements de surface et plus particulièrement les nanotechnologies utilisées pour produire des revêtements en couches minces plus précisément les dépôts physiques en phase vapeur (PVD), permet de synthétiser des nouveaux matériaux qui peuvent résister dans des conditions sévères de diverses applications.L'industrie des outils de coupe et plus précisément le bois dans notre cas, nécessitent de plus en plus la synthèse des nouveaux matériaux et nanomatériaux pour améliorer la tenue en service des outils de coupe.L'objectif de ce présent travail est de développer et caractériser des revêtements dont le matériau de base est le chrome et/ou le silicium en vue de les optimiser. L'élaboration a été réalisée par différentes méthodes à savoir la pulvérisation cathodique magnétron radio fréquence ou encore en mode courant direct. En outre, la RGPP (reactive gas pulsing process) a été exploité pour la première fois dans ce travail dont le but est de surmonter les difficultés rencontrées avec la pulvérisation réactive.Les différentes caractéristiques mécaniques et tribologiques des couches ont été étudiées et corrélées avec les caractéristiques physicochimiques et microstructurales.Il s'avère que la pulvérisation cathodique en mode courant direct prouve son importance par l'obtention des couches de meilleure qualité que celles obtenues en mode radio fréquence. Pour des contenus d'azote similaires on obtient des propriétés mécaniques et tribologiques plus importantes. On note que les propriétés mécaniques réalisent un gain de 60 % par rapport à celles obtenues en mode RF. En outre l'ajustement des paramètres de la méthode RGPP (le rapport cyclique et la période des pulses) influe considérablement les caractéristiques des couches obtenues et on montre une amélioration de la performance des couches. A l'issue de l'injection pulsée du gaz réactif, on montre que l'alternance entre l'ouverture et la coupure de la vanne du gaz réactif est indispensable pour la déposition dans un milieu réactif afin d'éliminer les composés métalliques sur les cibles obtenus lors de dépôt.Enfin, l'ajout de silicium au CrN mène à obtenir des solutions solides ou une structure nanocomposite selon la teneur de silicium dans la couche ce qui implique une amélioration des caractéristiques mécaniques et par la suite celles tribologiques.L'apport de ce travail de thèse est de présenter une étude globale sur la performance des couches CrN et CrSiN en corrélant ses caractéristiques mécaniques et tribologiques avec les paramètres physiques de dépôt et en adoptant plusieurs méthodes d'élaboration. / Develop and optimize new materials are still among the issues to improve the performance of the durability of materials.The field of surface treatments and nanotechnology used to produce thin film coatings specifically physical vapor deposition (PVD) allow the synthesis of new materials that can withstand harsh conditions in various applications.The cutting tool industry and more specifically the wood in our case require more synthesis of new materials and nanomaterials to improve the serviceability of cutting tools.The aim of the present work is to develop and characterize coatings with the base material is chromium and / or silicon and optimize them. The preparation was carried out by different methods : the magnetron sputtering radio frequency RF or direct current mode DC. In addition, RGPP (reactive gas pulsing process) was used for the first time in this work which aims to overcome the difficulties of sputtering in reactive environment.Different characteristics of the layers were studied and correlated with the physicochemical and microstructural characteristics.It turns out that the direct current sputtering method proves its importance in obtaining layers of better quality than those obtained by radio-frequency mode. For similar nitrogen content, greater mechanical and tribological properties were obtained. We note that the mechanical properties realize a gain of 60% compared to those obtained in RF mode. Further adjustment of parameters RGPP method (duty cycle and pulse period) significantly influences the characteristics of the layers obtained and shown to improve the performance of layers. Following the pulsed injection of the reactive gas, it is shown that the alternation between the opening and the cutting of the valve of the reactive gas is essential for deposition in a reactive environment to remove the metal compounds on targets obtained during deposition.Finally, the addition of silicon in CrN films leads to obtain solid solutions or nanocomposite structure according to the content of silicon in the layer which implies an improvement of the mechanical and tribological properties.The contribution of this thesis is to present a comprehensive study on the performance of CrN layers and CrSiN correlating mechanical and tribological characteristics with physical deposition parameters by adopting various methods of preparation.

Cette thèse se place dans le cadre d’un projet ANR qui vise à remplacer des dépôts électrolytiques sacrificiels par des dépôts PVD à base d’aluminium, moins néfastes pour l’environnement. Trois critères ont été définis :un comportement sacrificiel avec de faibles cinétiques de dissolution, une bonne résistance au grippage et la possibilité d’élaboration du dépôt avant emboutissage du substrat acier. Des revêtements monocouches ont été élaborés pour étudier l’effet d’un élément d’alliage dans l’aluminium. Certains éléments (Mo, Mn) améliorent les propriétés mécaniques et d’autres (Mg, Zn) les propriétés sacrificielles des revêtements. Cette étude a permis de mettre en évidence qu’il est difficile de combiner de bonnes propriétés mécaniques et sacrificielles. Pour pallier à ce problème, deux voies peuvent être explorées. L’élaboration d’alliages ternaires et celle d’architectures multicouches.Ce travail s’est focalisé de manière plus approfondie sur la deuxième voie. Des architectures multicouches ont été élaborées avec deux types de couches, chaque type de couche possédant l’une des deux propriétés souhaitées pour le revêtement. Les configurations étudiées sont les suivantes : Al-Mo/Al-Zn, Al-Mo/Al-Mg et Al-Mn/Al-Mg, avec différentes périodes. Cette étude a permis de trouver une architecture multicouche qui répond tout à fait aux deux premiers critères :Al-Mn/Al-Mg 15 nm.Une étude préliminaire en corrosion après déformation a été réalisée sur cette dernière. Elle perd son caractère sacrificiel en immersions salines de 48h à partir de 1% de déformation. L’optimisation des paramètres de dépôt pour améliorer la tenue mécanique de cette architecture est une prochaine étape. / This work is part of an ANR project which purpose is to find an alternative to sacrificial electrolytic coatingsusing aluminium-based PVD coatings, which are more environmental friendly. Three main parameters weredefined : a sacrificial behavior, good tribological properties and the possibility to elaborate the coatings before shaping the steel substrate. Monolayer coatings were elaborated to study the impact of an alloying element on aluminium properties. Some alloying elements increase mechanical properties (Mo, Mn) while others enhance the electrochemical behavior (Mg, Zn). To combine both properties, two methods can be used. Either the elaboration ofternary alloys or the elaboration of multilayer coatings. This work is focused on the second way. Some multilayercoatings were proposed with two types of layers, each type presenting one interesting property. This study permitted to find a multilayer architecture fitting very well two parameters required for the project.A preliminary study on this architecture was lead with electrochemical characterization after strain. The architecture loses its sacrificial behavior after 1% strain in 48h immersion. Two of the three requested criteria are found.The next step of this work would be the optimization of the process parameters to enhance the adhesion of the coating so the third parameter is achieved.

Pour le développement des nœuds technologiques 14 nm et en-deçà, la technologie planaire Fully Depleted Silicon-On-Isolator implémente des sources et drains (S&D) en Si1-xGex épitaxiés pour augmenter la mobilité des trous par induction d'une contrainte compressive dans le canal p-MOS. Le procédé de siliciuration auto-alignée est utilisé pour contacter les S&D avant le dépôt du diélectrique du premier niveau de contact. Cependant, le procédé de germanosiliciuration des S&D reste un défi majeur. En effet, le germanosiliciure de Ni souffre de la partition de Ge et de l'agglomération du film dès 400 °C qui dégradent irréversiblement les performances du transistor. La stabilité morphologique des siliciures de Ni a été considérablement améliorée par l'utilisation d'un alliage Ni1-yPty sur Si. Cependant, pour le système quaternaire Ni-Pt-Si-Ge, ainsi que pour les films ultra-minces de Ni ou Ni1-yPty à fort taux de Pt (> 10 at.%), les réactions à l'état solide sont complexes et leurs études restent rares. Dans ce travail, nous proposons une étude comparative des systèmes Ni/Si0,7Ge0,3 et NiPt(15 at.%)/Si0,7Ge0,3. La discussion est centrée sur les mécanismes de formation et de dégradation intervenant pendant la réaction Ni/Si0,7Ge0,3. Puis, l'impact du Pt sur la séquence de phase et la dégradation a été identifié. Finalement, la comparaison de ces réactions réalisées sur pleine plaque et dans des motifs a permis d'extraire l'impact du confinement. Afin de caractériser ces films très fins, la sonde atomique tomographique a été utilisée pour étudier la redistribution des éléments, ainsi que la diffraction des rayons X pour identifier la phase en présence et la texture du film. / For 14 nm node and beyond, planar Fully Depleted Silicon-On-Isolator (FDSOI) CMOS of STMicroelectronics implements Si1-xGex epitaxial layers in source/drain (S&D) areas to enhance the hole mobility by inducing a compressive stress in the pMOS channel. Salicide process is preformed to contact S&D prior pre-metal dielectric deposition. However, the Nickel based germanosilicidation of S&D remains more than ever a critical challenge. Indeed, Nickel germanosilicide suffers from Ge out-diffusion and film agglomeration from 400 °C which both degrade irreversibly transistor performances. Morphological stability of Ni based silicide has been considerably improved by using Ni1-yPty alloys on Si. Nevertheless, for the quaternary system with Ni-Pt-Ge-Si as well as for ultra-thin Ni or Ni1-yPty films and high Pt content (> 10 at.%), the solid state reactions are complex and remain poorly understood. In this work, we propose a comparative study between Ni/Si0,7Ge0,3 and NiPt(15 at.%)/Si0,7Ge0,3. We focused on the discussion on the formation and degradation phenomena occurring during the Ni/Si0,7Ge0,3 reaction. Then, the impact of Pt on both phase sequence and degradation has been identified. Finally, the comparison between reactions performed on blanket and patterned wafers permit to extract the impact of patterning. To characterize these very thin films, atom probe tomography was performed to study element redistribution, as well as X-rays diffraction to identify phase nature and texture.