Dans cette thèse nous nous sommes intéressés à établir une formulation probabiliste pour l’analyse du comportement d’un sol multicouche avec des caractéristiques aléatoires. Deux grands axes sont traités : ?la consolidation primaire et ?la réponse sismique des sols multicouches ayant des caractéristiques aléatoires. Nous utilisons les simulations de Monte Carlo associées à des méthodes semi-analytiques adaptées aux sols multicouches avec une stratification horizontale. Nous avons aussi comparés les résultats obtenus à partir de cette formulation à ceux fournis par les règlements parasismiques suivants : RPA 99 (version 2003), UBC 97 et l’EC8. Cette étude a montré que les valeurs maximales des forces de cisaillement à la base des bâtiments variaient substantiellement en fonction de la variation de la hauteur du profil de sol ainsi que de son hétérogénéité pouvant atteindre un rapport relatif de l’ordre de 3 dans les cas les plus défavorables. Ce rapport peut également être inférieur à 1 conduisant à des structures moins économiques / In this thesis we are interested to establish a probabilistic formulation for the behavior analysis of a multilayered soil with random characteristics. Two main axes are treated: ?primary consolidation and ?seismic response of multilayered soils with uncertain characteristics. We use Monte Carlo simulations associated with semi-analytical methods adapted for the multilayered soils with horizontal stratification. We have also compared the results obtained from this formulation with those provided by the following seismic codes: RPA 99 (version 2003), UBC 97 and EC8. This study showed that the maximum values of the shear forces at the base of the buildings vary substantially according to the variation of the soil profile height as well as its heterogeneity which can reach a relative ratio of about 3 in the extreme cases. This ratio can also be lower than 1 leading to less economic structures

Les aciers inoxydables martensitiques sont utilisés dans l'industrie aéronautique où de hautes propriétés mécaniques sont requises. Cependant, dû à leur faible teneur en chrome, ils sont relativement sensibles à la corrosion localisée et particulièrement à la corrosion caverneuse qui se développe en milieu confiné. Tout d'abord, le comportement électrochimique de l'acier inoxydable martensitique X12CrNiMoV12-3 a été étudié dans une solution neutre et chlorurée (NaCl 0,1 M + Na2SO4 0,04 M) en plein bain. Des mesures électrochimiques (courbes de polarisation et mesures d'impédance) couplées à des analyses de surface par XPS ont permis de caractériser les films passifs formés pour différentes conditions. Les résultats obtenus ont permis de montrer le rôle important joué par l'oxygène dissous sur la formation et/ou la modification du film passif pendant l'immersion dans l'électrolyte. Les diagrammes d'impédance obtenus au potentiel de corrosion et en milieu aéré sont caractérisés par deux constantes de temps qui ont été attribuées au film passif (hautes fréquences) et au transfert de charges (basses fréquences). L'analyse de la partie hautes fréquences des diagrammes d'impédance électrochimique à l'aide du modèle en loi de puissance a permis de montrer de faibles variations de l'épaisseur des films pendant l'immersion. Des mesures électrochimiques ont ensuite été réalisées à l'aide du montage de la cellule à couche mince qui permet de travailler avec des épaisseurs d'électrolyte rigoureusement contrôlées. Les essais réalisés ont montré l'aptitude à la repassivation de l'acier inoxydable martensitique dès qu'il est en contact avec l'oxygène dissous en particulier pour des faibles épaisseurs d'électrolyte (inférieur à 100 µm). Lorsque le milieu est confiné entre deux parois en acier afin de reproduire une situation de corrosion caverneuse, il a été montré la corrosion est fortement accélérée lorsque l'épaisseur d'électrolyte est faible (inférieur à 500 µm). / Martensitic stainless steels are mainly used for applications where high mechanical performance is required. However, due to the low chromium content, they are relatively sensitive to localised corrosion, and particularly, to crevice corrosion encountered in confined environments. First, the electrochemical behavior of X12CrNiMoV12-3 martensitic stainless steel has been studied in a bulk neutral chloride solution (0.1 M NaCl + 0.04 M Na2SO4). Electrochemical measurements (polarisation curves and impedance measures) and XPS surface analysis were performed in order to characterise the passive films formed under different experimental conditions. The results showed the important role of dissolved oxygen to form and/or modify the passive film during immersion in electrolyte. The impedance diagrams are characterised by two time constants wich are attributed to passive film response (high frequency range) and to charge transfert resistance (low frequency range). The analyse of the high frequencies part of the diagrams by using the "power law model" showed low evolution of passive films thickness during immersion. Then, electrochemical measurements were perfomed in confined environments by using a thin layer cell where the electrolyte thickness were rigourosly adjusted. The measurements showed that the martensitic stainless steel is in passive state even for low electrolyte thickness (inferior in 100 µm). When the electrolyte is confined between two stainless electrodes in order to reproduce the same conditions find during crevice corrosion, the corrosion is sharply accelerated when the electrolyte thickness is above 500 µm

Palicourea marcgravii St. Hil. (Rubiaceae) vulgarmente conhecida como \"erva de rato\" é uma planta tóxica brasileira de grande interesse econômico na pecuária, por provocar, em bovinos, convulsões, arritmias cardíacas e \"morte súbita\" em elevado número de animais. No presente trabalho, as folhas dessecadas e moídas de P. marcgravii foram extraídas com etanol 95 %, a temperatura ambiente, por percolação; o extrato resultante foi fracionado por partição com acetato de etila e butanol saturado com água. Os resíduos obtidos foram testados \"per os\" em ratos, buscando-se investigar nos mesmos, a presença do princípio ativo tóxico. O resíduo aquoso foi o único que produziu convulsões e morte dos animais. A existência do monofluoroacetato (MF A) no resíduo aquoso foi comprovada biologicamente através do paralelismo entre as retas refetentes às funções dose/porcentagem de letalidade e dose/latência para a 1ª convulsão que foram construídas para o resíduo aquoso e padrão de referência (monofluoroacetato de sódio). O MFA foi também identificado quimicamente através da RMN19F e da cromatografia em camada delgada. Os resultados obtidos comprovaram a presença de MF A nas folhas de P.marcgravii, responsabilizando-o pelos efeitos tóxicos produzidos. Também foram levantadas algumas hipóteses na tentativa de explicar a sintomatologia dos animais intoxicados. / Palicourea marcgravii St. Hil. (Rubiaceae) is one of the most economica1ly important poisonous plants for Brazilian livestock, since it induces not only seizures, cardiac arrythmias, but also \"sudden death\" of large number of the intoxicated animals. ln the present paper, the dissected and grounded leaves of P.marcgravii were extracted with ethanol 95 %, at room temperature, by percolation; the resultant extract was fractionized by partition in ethyl acetate and butanol saturated with water. The obtained residues were administered \"per os\" to rats, trying to look for the presence of the active toxic principIe. The aqueous residue was the only that induced seizures and death to the animals. The presence of monofluoroacetate (MFA) in the aqueous residue was biologica1ly confirmed by the correlation shown in the sodium monofluoroacetate and the aqueous residue dose-response and dose effect curves. MFA was also identified through NMR19F and thin layer chromatography. The obtained results confirmed the presence of MF A in the P.marcgravii leaves; they also suggest that the toxic effects induced by this plant are a consequence of the presence of MFA in its leaves. Further, some hypothesis were also perfomed, in an attempt to better explain the symptoms induced by the plant leaves.

A atual Política Nacional de Plantas Medicinais e Fitoterápicos prevê investimentos em pesquisa e desenvolvimento para suprir a necessidade da indústria nacional em adquirir a matéria prima para a produção de novos fitoterápicos de maneira segura e controlada. As espécies do gênero Smilax, conhecidas popularmente como salsaparrilha, são empregadas na medicina popular como fortificante, antirreumático e antissifilítico e são vendidas em farmácias, casa de ervas e mercados públicos sem que exista um controle de qualidade de sua origem e eficácia. Além disso, a procedência do material é baseada principalmente no extrativismo. O controle de qualidade das drogas vegetais deveria ter uma base mais segura de identificação das drogas através da caracterização e definição de particularidades anatômicas e químicas. Este estudo teve como objetivo apresentar a quantidade, o valor, o modo de preparo, utilização e a procedência da salsaparrilha comercializada no Estado de São Paulo, bem como analisar a anatomia e o perfil químico de 44 amostras de salsaparrilha comercializada. Amostras de raiz foram submetidas às técnicas convencionais de microscopia de luz e eletrônica de varredura. Também foram realizados testes histoquímicos. Para determinar o perfil químico por Cromatografia em Camada delgada (CCD), foram realizados extratos etanólicos de amostras de raízes. O perfil químico do material comercializado foi comparado com o perfil das espécies de Smilax previamente identificadas (S. goyazana A. De Candolle, S. rufescens Grisebach, S. brasiliensis Sprengel, S. campestris Grisebach, S. cissoides Martius ex Grisebach, S. fluminensis Steudel, S. oblongifolia Pohl ex Grisebach e S. polyantha Grisebach). A quantidade média de salsaparrilha comercializada nas farmácias (400g) e nas casas de ervas (20Kg) é elevada se for considerado o fato de que as raízes não são procedentes de cultivo. Embora tenha sido observada grande semelhança entre a estrutura anatômica das amostras de salsaparrilha comercializadas e a estrutura já descrita na literatura para as espécies de Smilax, houve diferenças em relação à organização do floema, à presença de séries de idioblastos contendo ráfides na medula, à ausência de idioblastos fenólicos na medula e presença de metaxilema no centro da estrutura. O teste histoquímico confirmou a presença de amido em todas as amostras comerciais. As análises em CCD dos extratos etanólicos das amostras comerciais evidenciaram diversas manchas com tonalidades variando de amarelo a verde. Além disso, as manchas apresentaram componentes de mesmo Fator de retenção (Rf), indicando semelhança química entre as diversas amostras. No entanto, o padrão de distribuição de manchas, bem como o Rf das amostras comerciais diferiu daqueles obtidos para as oito espécies de Smilax, os quais foram muito similares entre si. / The current National Policy on Herbal Medicine provides investments in drug research and development to supply the need of national industry to acquire the raw material for production new herbal medicines in a safe and controlled way. The species of Smilax, popularly known as sarsaparilla, are used in folk medicine to be effective as tonic, antirheumatic and antisyphilitic properties and they are commercialized in pharmaceutical stores, natural products stores and public markets in Brazil with no quality control of its origin and efficacy. In addition, these plants are still harvested in extractive way. The quality control of herbal drugs should have more secure identification of drugs through the characterization and definition of anatomical and chemical peculiarities. This study aims to present the quantity, value, method of preparation, use and origin of the commercialized sarsaparilla in cities from the São Paulo state and to investigate the anatomy and chemical profile of 44 samples of the commercialized sarsaparilla. Root samples were processed and analyzed using conventional light and scanning electron microscopy techniques. Usual histochemical tests were also performed. Chemical profiles of samples were analyzed by thin layer chromatography (TLC) using ethanolic extracts of the roots. The chemical profile of the commercialized material was compared with profiles of previously identified species of Smilax (S. goyazana A. De Candolle, S. rufescens Grisebach, S. brasiliensis Sprengel, S. campestris Grisebach, S. cissoides Martius ex Grisebach, S. fluminensis Steudel, S. oblongifolia Pohl ex Grisebach and S. polyantha Grisebach). The average amount of sarsaparilla sold in pharmaceutical stores (400g) and natural products stores (20kg) is high if one considers the fact that the roots are not found under cultivation. Although there was a great similarity between the anatomical structure of commercialized sarsaparilla and the structure already described in literature for the Smilax species, there were found some differences in the organization of the phloem, the occurrence of series of idioblasts containing raphides in the pith, the absence of phenolic idioblasts in the pith and the presence of metaxylem in the center of the organ. The histochemical tests confirmed the presence of starch in all commercialized samples. Chemical profile showed several spots with colors ranging from yellow to green. Moreover, the spots showed the same components retention factor (Rf), indicating chemical similarity between the different samples. However, the distribution pattern of spots, Rf value of commercial samples differed from the eight species of Smilax, which were very similar to each other.

A técnica de cultivo em camada delgada contendo ágar Middlebrook 7H11 modificado foi comparada com o cultivo padrão em meio de Stonebrink, visando avaliar a sensibilidade e o tempo de detecção de Mycobacterium bovis em órgãos de bovinos e bubalinos oriundos de abatedouros comerciais. Posteriormente, a PCR foi utilizada para a confirmação do crescimento observado nos cultivos, bem como a coloração de Ziehl-Neelsen na pesquisa de bacilos álcool-ácido resistentes. As 49 amostras testadas foram descontaminadas pelo método tradicional de Petroff e trabalhadas em duas etapas. Na primeira, todas foram semeadas nas placas contendo o meio de Middlebrook 7H11 em camada delgada e nos tubos contendo o meio de Stonebrink, e as colônias observadas macroscopicamente em ambos os meios foram submetidas à PCR. Na segunda, 10 amostras cultivadas na primeira etapa foram submetidas a novo cultivo, somente em camada delgada, para observação do crescimento microscópico das colônias e também analisadas pela PCR. Os resultados obtidos demonstraram que: 1) a técnica de cultivo de Mycobacterium bovis em camada delgada no meio de Middlebrook 7H11 modificado em amostras de órgãos de bovinos e bubalinos mostrou-se viável quando comparada ao cultivo clássico no meio de Stonebrink, reduzindo o tempo de isolamento e podendo ser utilizada de forma complementar aos métodos tradicionais de diagnóstico da tuberculose bovina; 2) foi possível a identificação precoce do crescimento das micobactérias em camada delgada (entre 12º e 25º dia de crescimento) quando comparadas ao Stonebrink; 3) a PCR mostrou-se uma ferramenta complementar à somatória das técnicas de descontaminação de Petroff, coloração de Ziehl-Neelsen e cultivo em camada delgada na confirmação do diagnóstico de presença de micobactérias em amostras de órgãos de bovinos e bubalinos. / The modified thin layer Middlebrook 7H11 cultivation was compared to the standard culture technique containing Stonebrink media, in order to evaluate the sensitivity and time for the detection of Mycobacterium bovis in bovine and buffalo organs deriving from commercial slaughterhouses. The PCR was applied for confirmation of the growth observed in the cultures, as well as the Ziehl-Neelsen color technique in order to detect acid-fast bacilli. 49 samples were submitted to the classic Petroff\'s decontamination method, and worked in two stages. In the first one, all of them were sowed in plates containing modified Middlebrook 7H11 agar in thin layer and in tubes containing the Stonebrink media, and the colonies observed macroscopically in both medias were submitted to the PCR. In the second stage, 10 samples from the first stage were submitted to a new culture, only in thin layer, for microscopical growth observation of the colonies and also submitted to the PCR. The results showed that: 1) Mycobacterium bovis cultivation in modified thin layer Middlebrook 7H11 for bovine and buffalo samples were viable when compared to the classic culture in Stonebrink, reducing the time of isolation, and can be applied as a complement to the traditional bovine tuberculosis diagnosis methods; 2) earlier identification of mycobacteria growth was found in thin layer (between 12nd and 25th day of growth) when compared to the Stonebrink; 3) PCR technique showed to be a complementary tool to the sum of techniques including Petroff decontamination, Ziehl-Neelsen color and thin layer cultivation for the diagnosis confirmation of the presence of mycobacteria in bovine and buffalo organs samples .

A técnica de cultivo em camada delgada contendo ágar Middlebrook 7H11 modificado foi comparada com o cultivo padrão em meio de Stonebrink, visando avaliar a sensibilidade e o tempo de detecção de Mycobacterium bovis em órgãos de bovinos e bubalinos oriundos de abatedouros comerciais. Posteriormente, a PCR foi utilizada para a confirmação do crescimento observado nos cultivos, bem como a coloração de Ziehl-Neelsen na pesquisa de bacilos álcool-ácido resistentes. As 49 amostras testadas foram descontaminadas pelo método tradicional de Petroff e trabalhadas em duas etapas. Na primeira, todas foram semeadas nas placas contendo o meio de Middlebrook 7H11 em camada delgada e nos tubos contendo o meio de Stonebrink, e as colônias observadas macroscopicamente em ambos os meios foram submetidas à PCR. Na segunda, 10 amostras cultivadas na primeira etapa foram submetidas a novo cultivo, somente em camada delgada, para observação do crescimento microscópico das colônias e também analisadas pela PCR. Os resultados obtidos demonstraram que: 1) a técnica de cultivo de Mycobacterium bovis em camada delgada no meio de Middlebrook 7H11 modificado em amostras de órgãos de bovinos e bubalinos mostrou-se viável quando comparada ao cultivo clássico no meio de Stonebrink, reduzindo o tempo de isolamento e podendo ser utilizada de forma complementar aos métodos tradicionais de diagnóstico da tuberculose bovina; 2) foi possível a identificação precoce do crescimento das micobactérias em camada delgada (entre 12º e 25º dia de crescimento) quando comparadas ao Stonebrink; 3) a PCR mostrou-se uma ferramenta complementar à somatória das técnicas de descontaminação de Petroff, coloração de Ziehl-Neelsen e cultivo em camada delgada na confirmação do diagnóstico de presença de micobactérias em amostras de órgãos de bovinos e bubalinos. / The modified thin layer Middlebrook 7H11 cultivation was compared to the standard culture technique containing Stonebrink media, in order to evaluate the sensitivity and time for the detection of Mycobacterium bovis in bovine and buffalo organs deriving from commercial slaughterhouses. The PCR was applied for confirmation of the growth observed in the cultures, as well as the Ziehl-Neelsen color technique in order to detect acid-fast bacilli. 49 samples were submitted to the classic Petroff\'s decontamination method, and worked in two stages. In the first one, all of them were sowed in plates containing modified Middlebrook 7H11 agar in thin layer and in tubes containing the Stonebrink media, and the colonies observed macroscopically in both medias were submitted to the PCR. In the second stage, 10 samples from the first stage were submitted to a new culture, only in thin layer, for microscopical growth observation of the colonies and also submitted to the PCR. The results showed that: 1) Mycobacterium bovis cultivation in modified thin layer Middlebrook 7H11 for bovine and buffalo samples were viable when compared to the classic culture in Stonebrink, reducing the time of isolation, and can be applied as a complement to the traditional bovine tuberculosis diagnosis methods; 2) earlier identification of mycobacteria growth was found in thin layer (between 12nd and 25th day of growth) when compared to the Stonebrink; 3) PCR technique showed to be a complementary tool to the sum of techniques including Petroff decontamination, Ziehl-Neelsen color and thin layer cultivation for the diagnosis confirmation of the presence of mycobacteria in bovine and buffalo organs samples .

L’industrie aéronautique travaille sur l’amélioration des systèmes propulsifs parl’introduction de composites dans la fabrication des aubes de soufflante afin d’alléger lastructure et ainsi de réduire la consommation en carburant des avions. Ces pièces réaliséesen tissage 3D présentent généralement des irrégularités de surface. Une manière d’optimisercet aspect est d’ajouter un pli additionnel de surface : nos travaux de thèse portent sur ledéveloppement de ce pli sous la forme d’un renfort « Non Crimp Fabric » (NCF) biaxial extrafinen fibre de carbone de module intermédiaire (IM), inférieur à 100 g/m², régulier et ayant unebonne déformabilité. Lors de nos travaux de thèse, nous avons utilisé la méthode des plans d’expériencepour améliorer la technologie d’étalement afin de répondre aux exigences demandées. Nousavons pu définir la configuration optimale d’étalement permettant d’atteindre la cible d’un pliinférieur à 50 g/m² en fibre de carbone IM. Pour réaliser un NCF extra-fin, après étalement,les plis sont assemblés par couture afin d’assurer la tenue du renfort. La combinaison decouture choisie (armure, tension, longueur, jauge …) conditionne l’aspect du NCF et sacapacité à être manipulée et déformée. Nous avons donc optimisé les paramètres de coutureafin d’obtenir les propriétés souhaitées. Après avoir optimisé l’étalement des fibres et l’assemblage des plis, nous avons réalisé et caractérisé les renforts NCF extra-fins pour valider leurs propriétés. Nous sommesfinalement parvenus à mettre au point un renfort NCF en fibre de carbone IM, inférieur à50 g/m² par pli ayant un taux de couverture supérieur à 98 % et une bonne capacité à sedéformer. / Aircraft manufacturers are working on the improvement of their engines bymanufacturing fan blades with advanced composite materials to reduce fuel consumption.However, fan blades are made from 3D woven fabrics which often have surface irregularities.It can be minimized by an additional thin layer on the surface : our thesis work is focused onthe development of a new textile structure based on ultra-thin biaxial “Non Crimp Fabric” (NCF)technology. This spread NCF made from intermediate modulus (IM) carbon fibers must belighter than 100 gsm, regular and deformable.During our thesis work, we used Design of Experiments (DOE) methodology to improvethe spreading technology used by Chomarat to make ultra-light NCF materials and meet theestablished requirements. We were able to reach the ultra-thin ply target of less than 50 gsmper ply. After optimizing the spreading process these thin ply tapes are stitched together tocreate NCF. Stability, visual aspect, handling and deformability are dependent on the stitchingsettings (stitching pattern, tension, length, gauge, etc.). Therefore we optimized the stitchingparameters to get the desired properties.After the spreading and stitching process had been optimized, the NCF weremanufactured and tested to validate the desired properties had been achieved. The testingconfirmed that we were able to develop a new carbon fiber NCF that was less than 50 gsm perply, had a coverage rate of higher than 98 % and had good deformability characteristics.

L'agence spatiale européenne et le CNES étudient la possibilité d’envoyer des microsystèmes dans l’espace, en particulier pour le gain de masse qu’ils représentent. Afin d’améliorer la fiabilité des composants en couches minces dans le temps et leurs performances, il est nécessaire de connaitre leurs propriétés mécaniques. Plusieurs techniques de caractérisation existent, en particulier la nanoindentation qui sollicite les couches minces directement sur substrat. Mais les résultats peuvent être largement influencés par le substrat dans le cas des couches microniques. Les méthodes de traction uniaxiale (CNES) et du gonflement de membranes autoportantes (INL) permettent de s’affranchir des effets du substrat, mais la fabrication de telles structures est complexe et nécessite bon nombre d’étapes technologiques pour retirer le substrat en face arrière. L’objectif de cette thèse est de comprendre le lien qui existe entre les paramètres de fabrication de couches minces métalliques d'or et d'aluminium, leur microstructure, et leurs propriétés mécaniques à l’aide des outils présentés précédemment. Une perspective étant de mieux agir sur les procédés de fabrication afin d’améliorer la fiabilité des composants. Le premier chapitre présente les différentes techniques de dépôt, leur thermodynamique et cinétique, les types de microstructures rapportées dans la littérature, ainsi que la réalisation des structures de test. Le deuxième présente les caractérisations microstructurales, et la corrélation entre les paramètres de dépôt et les propriétés microstructurales est discutée. Le chapitre trois présente les caractérisations mécaniques des couches minces, sur substrat ou autoportantes, par les méthodes de nanoindentation en pointe Berkovich et sphérique, de microtraction et du gonflement de membrane. Le dernier chapitre est consacré aux relations entre les propriétés microstructurales et mécaniques des couches minces métalliques et à l'influence des traitements thermiques. / The European Space Agency and CNES are studying the possibility of sending microsystems in space, especially for the mass gain they represent. To improve the reliability of components, it is necessary to know their mechanical properties. Several characterization techniques exist, especially nanoindentation of thin films on substrates. However, results can be largely influenced by the substrate in the case of micron layers. The methods of uniaxial tension (CNES) and bulge-test (INL) on freestanding specimen are used to eliminate the effects of the substrate, but the fabrication of such structures is complex and requires many technological steps to remove the substrate on the backside. The objective of this thesis is to understand the relationship between manufacturing parameters of thin metal films of gold and aluminum thin films, their microstructure and mechanical properties using the tools described above. The first chapter presents different deposition techniques, their thermodynamics and kinetics, types of microstructures reported in the literature, and the fabrication of test structures. The second presents the microstructural characterization, and correlation between deposition parameters and the microstructural properties is discussed. Chapter three presents the mechanical characterization of thin films on substrate or freestanding ones, by the methods of nanoindentation with Berkovich and spherical tips, microtensile test and bulge test. The last chapter is devoted to relations between microstructural and mechanical properties of thin metal films and the influence of heat treatments.

No description available.

Les siliciures métalliques constituent un élément crucial des contacts électriques des transistors que l'on retrouve au coeur des circuits intégrés modernes. À mesure qu'on réduit les dimensions de ces derniers apparaissent de graves problèmes de formation, liés par exemple à la limitation des processus par la faible densité de sites de germination. L'objectif de ce projet est d'étudier les mécanismes de synthèse de siliciures métalliques à très petite échelle, en particulier le NiSi, et de déterminer l’effet de l’endommagement du Si par implantation ionique sur la séquence de phase. Nous avons déterminé la séquence de formation des différentes phases du système Ni-Si d’échantillons possédant une couche de Si amorphe sur lesquels étaient déposés 10 nm de Ni. Celle-ci a été obtenue à partir de mesures de diffraction des rayons X résolue en temps et, pour des échantillons trempés à des températures critiques du processus, l’identité des phases et la composition et la microstructure ont été déterminées par mesures de figures de pôle, spectrométrie par rétrodiffusion Rutherford et microscopie électronique en transmission (TEM). Nous avons constaté que pour environ la moitié des échantillons, une réaction survenait spontanément avant le début du recuit thermique, le produit de la réaction étant du Ni2Si hexagonal, une phase instable à température de la pièce, mélangée à du NiSi. Dans de tels échantillons, la température de formation du NiSi, la phase d’intérêt pour la microélectronique, était significativement abaissée. / Currently metal silicide constitutes a crucial component in the formation of electrical contacts for transistors that forms the heart of modern day integrated circuits. As we reduce the dimensions of the latter, we are faced with serious problems of formation, related for example to the process limitation due to the weak density of germination sites. The objective of this project is to study at small scale the synthesis mechanisms of metal silicide, in particular NiSi, and to determine the effect of Si implantation damage on the phase sequence. We have determined the different phase sequences of the Ni-Si system for samples composed of a 10 nm Ni surface layer deposited on a-Si. These were obtained by time resolved x-ray diffraction (TR-XRD) measurements. As for samples quenched at critical temperatures we identified the different phases, their composition and their microstructure were determined by pole figures, Rutherford back scattering (RBS) spectrometry and transmission electron microscopy (TEM). We noted that for approximately half the samples, a spontaneous reaction happened before annealing. The result of the reaction was hexagonal Ni2Si, a phase unstable at room temperature, mixed with NiSi. In theses samples, the temperature of formation for the phase of interest, the NiSi, was lower.