L’utilisation des fibres végétales dans les polymères composites suscite de nombreuses investigations. Avant de mélanger les fibres végétales dans le polymère, un traitement chimique peut être effectué permettant de réduire l’hydrophilicité des fibres et d’améliorer l'adhérence à l’interface fibre/matrice. Dans cette thèse, l'eau et l'alcali sont utilisés d'abord pour traiter les fibres de chanvre, puis trois agents silane : 3-(triméthoxysilyl)propyl méthacrylate (MPS), N-[3- (triméthoxysilyl)propyl] aniline (PAPS) et (3-Aminopropyl)-triéthoxysilane (APS), sont utilisés pour modifier plus ou moins la surface des fibres de chanvre. Ces fibres traitées ou modifiées sont ensuite mélangées avec le polypropylène (PP) pour la fabrication des composites. Les effets de ces différents traitements sur la structure, les composants et l’hydrophilicité des fibres, et les propriétés mécaniques de ces composites sont mis en évidence. Nous avons étudié ensuite l’effet de vieillissement sur leurs comportements mécaniques, notamment l'humidité, la température et le rayonnement ultraviolet. Les résultats ont montré que le traitement de fibres par l'eau et l’alcali a des effets considérables sur la structure de fibres, les propriétés mécaniques et la durabilité des composites renforcés. La modification par l'agent de silane a une influence moins importante sur la structure des fibres, pourtant son groupe fonctionnel a une influence significative sur les propriétés mécaniques et la résistance au vieillissement des composites renforcés / Using agro fiber as reinforcement of polymer com-posites attracts numerous investigations due to the good mechanical properties and environmental benefits. Prior to blend agro fiber with polymer, chemical treatment can be employed to treat agro fiber for the purpose of reducing the hydrophilicity of fiber and improving the interfacial adhesion fi-ber/polymer matrix. In this thesis, water and alkali are utilized to treat hemp fiber firstly and then three silane agent as 3-(Trimethoxysilyl)propyl methacry-late (MPS), N-[3-(Trimethoxysilyl)propyl]aniline (PAPS) and (3-Aminopropyl)-triethoxysilane (APS) are employed to modify the hemp fiber surface. These treated or modified fibers are blended respectively with polypropylene (PP) to fabricate the hemp fiber/PP composites. The effects of these different treatments on the structure, components and hydro-philicity of fiber, and the mechanical properties of the reinforced PP composites are studied. Moreover, the accelerated ageing experiments including humidity, temperature and ultraviolet of the reinforced PP composites are conducted. The results showed that the fiber treatment of water and alkali has a considerable effect on fiber structure, mechanical properties and durability of the reinforced compo-sites. The silane agent modification of fiber has less influence on the fiber structure but its functional group has great influence on the mechanical proper-ties and ageing resistance of the reinforced compo-sites.

Cette thèse comprend deux parties : Détermination des contraintes résiduelles dans les composites stratifiés ±θ induites par le cycle thermique de fabrication et Etude de leurs influences sur le com-portement mécanique de ces stratifiés. Limitée par la théorie actuelle, la détermination expérimentale des contraintes résiduelles dans les stratifiés ±θ a été très difficile. Dans notre étude, la méthode du trou incrémental a été employée afin de relaxer les contraintes résiduelles et les déformations provoquées ont été mesurées par les jauges de déformation. Une nouvelle approche proposée dans cette thèse permet d’associer les déformations autour du trou et les contraintes résiduelles au sein du stratifié ±θ. Les coefficients de calibration ont été déterminés par la simulation numérique. Grâce à l’approche développée, nous avons constaté une relation linéaire entre les contraintes résiduelles et l’angle θ du stratifié [02/θ2]s. En adaptant un modèle thermoélastique du matériau, les résultats expérimentaux ont pu être modélisés numériquement. Ensuite, nous avons étudié l’influence de l’épaisseur du stratifié, du cycle de cuisson et du vieillissement hydrothermique sur la distribution des contraintes résiduelles. A l’aide de la technique d’émission acoustique, les influences des contraintes résiduelles sur l’endommagement et le comportement mécanique des stratifiés ont été étudiées grâce aux essais de traction. Enfin, l’importance des contraintes résiduelles sur la rupture transversale du stratifié a été mise en évidence en comparant avec les résultats théoriques / This thesis work consists of two main parts: Deter-mination of residual stresses in composites laminates ±θ, introduced by the thermal cycle during the manufacturing process of laminates and Study of their influences on the mechanical behavior of these laminates. Limited by the current theory, the exper-imental determination of residual stresses in the laminates ±θ was very difficult. In this work, the incremental hole drilling method was performed for the residual stresses relaxation and then the gener-ated strains around the hole were measured with strain gages. The new approach proposed in this thesis allows associating the strains around the hole and the residual stresses in the laminates ±θ. The calibration coefficients were determined by the numerical simulation. With this approach, we found a linear relationship between the residual stresses and the fiber orientation angle θ for the composite laminates [02/θ2]s. By adapting a thermoelastic ma-terial model, the results obtained by our new ap-proach were modelized by the numerical study. Then we studied the influence of laminate thickness, curing cycle and hydrothermal ageing on the distri-bution of residual stresses. With the help of acoustic emission technique, the influences of the residual stresses on the damage and the mechanical behavior of composite laminates were studied through tensile tests. Finally, the importance of the residual stresses on the transverse failure of composite laminates was demonstrated comparing with the theoretical results

Depuis quelques années les matériaux composites à base de fibres naturelles sont de plus en plus utilisés pour les nouvelles performances qu’ils proposent. C’est surtout au niveau des fibres naturelles que de nouvelles propriétés sont proposées. Dans ce travail, nous nous sommes essentiellement intéressés aux fibres naturelles de chanvre. Ces fibres sont déjà fortement utilisées dans l’automobile et la construction. En Europe, ces fibres sont produites principalement en France et plus particulièrement dans l’Aube. Pour développer des agro-composites hautes performances, c’est sous la forme de fibres longues et de tissus que nous avons choisi d’orienter ce travail de thèse. Nous avons choisi la thermocompression pour élaborer des plaques avec des tissus de chanvre et une matrice en polypropylène (PP). Ce travail permet de voir l’influence des conditions d’élaboration sur le comportement mécaniques de ces agro-composites. Cette thèse permet aussi de voir l’effet du vieillissement aux UV et à l’Humidité sur les performances de ces matériaux. Enfin une analyse des contraintes résiduelles par la méthode du trou incrémental permet de voir leurs effets sur ces agro-matériaux / In recent years composite materials based on natural fibers are more and more used for their new performances. Natural fibers propose attractive environmental, mechanical and thermal properties.In this work, we are firstly interested in hemp fibers. These fibers are already used in the automotive and construction industry. In Europe, these fibers are produced mainly in France and especially in Aube. To develop agro-composites with high performances, we have focused this thesis on hemp woven. We chose to elaborate the plates with hemp woven and a polypropylene matrix (PP) by compression molding. This work allows us to see the influence of elaboration conditions on the mechanical behavior of these agro-composites. This thesis also allows us to see the effect of aging conditions UV and humidity on the performance of these materials. Finally an analysis of residual stresses determined by the hole drilling method is proposed to see their effects on the agro-materials

Orientador: Prof. Dr. Wendel Andrade Alves / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2015. / Os biopolímeros mostram-se materiais promissores na construção de dispositivos para aplicações na área biomédica. Dentro desta classe a policaprolactona vêm sendo amplamente empregada em sistemas de liberação controlada, uma vez que permite a incorporação de drogas preservando a atividade farmacológica. Neste trabalho, apresentamos a proposta de um material híbrido composto por policaprolactona (PCL) e micro-/nanotubos de L,L-difenilalanina (MNTs-FF). O biomaterial foi avaliado à temperatura ambiente nas concentrações de 0% a 50% de MNTs-FF. As propriedades morfológicas e estruturais dos compósitos foram investigadas por diferentes técnicas analíticas, espectroscópicas e microscópicas. Os resultados obtidos mostraram que, o peptídeo promoveu variações microestruturais na rede polimérica, impactando no diâmetro médio das fibras (~570-360 nm), na cristalinidade (34,6 - 6,6%) e na porosidade (74 - 50%). Como consequência, tais variações foram associadas ao comportamento elástico-plástico da matriz. O aumento da concentração de MNTs-FF contribuiu para um maior módulo de Young para as fibras de PCL (12,47-18,96 MPa). Testes de biodegradação enzimática mostraram uma perda significativa de massa para as membranas com peptídeos em relação ao polímero puro. Os compósitos de MNTs-FF/PCL foram avaliados na liberação controlada do fármaco lipofílico, benzocaína. As membranas apresentaram uma eficácia progressiva de liberação de ~13 horas, sendo este um resultado superior ao gel disponível no mercado atualmente. Logo, o compósito exibiu elevada resistência mecânica e características biodegradáveis, sendo propriedades favoráveis na aplicação como sistemas carreadores de fármacos. / The biopolymers appear to be promising materials for the development of devices for the biomedicine area. Within this class, the polycaprolactone has been widely used in systems of controlled liberation, once it allows the incorporation of drugs preserving the pharmacological activity. In this essay, we propose a hybrid material composed by polycaprolactone (PCL) and micro-/nanotubes of L,L-diphenylalanine (FF-MNSs). The biomaterial was evaluated under room temperature in the concentrations from 0% to 50% of FF-MNSs. The morphological and structural properties were investigated by different analytical, spectroscopical and microscopical techniques. The results showed that the peptide promoted microstructural variations in the polymeric net, having impact on the average diameter of the fibers (~570-360 nm), in the crystallinity (34.6- 6.6%) and in the porosity (74 - 50%). As a result, such variations were associated to the elastic-plastic behavior of the matrix. The increase in concentration of FF-MNSs contributed for a bigger Young module for the PCL fibers (12.47-18.96 MPa). Enzymes biodegrading tests showed a significant loss of mass for the membranes with peptides comparing to the pure polymer. The composite of FF-MNSs/PCL were evaluated in the controlled liberation of the lipophilic drug, benzocaine. The membrane presented a progressive liberation efficiency of ~13 hours, being this a superior result to the gel available in the market currently. Therefore, the composite showed high mechanical resistance and biodegradable features, which are favorable features in its use as drug carrier systems.

A busca por materiais que possam ser modificados em nível molecular tem sido o alvo de numerosas pesquisas no mundo. Desta maneira, as técnicas de fabricação de filmes finos se destacam devido à possibilidade de se reduzir custos e melhorar a eficiência de sistemas como, por exemplo, os fotossensíveis. Neste contexto, o objetivo deste trabalho foi a obtenção e caracterização de filmes finos através da técnica de automontagem (técnica "camada por camada" ou Layer-by-Layer). Os filmes foram depositados sobre diversos substratos (lamínula de vidro, silício e poliestireno). Nesse trabalho foram depositados dois conjuntos diferentes de multicamadas combinados com duas proporções diferentes de cada sistemas de soluções. O sistema catiônico foi composto pela solução do polieletrólito orgânico PDDA e a solução coloidal do semicondutor inorgânico seleneto de cádmio (CdSe). O sistema aniônico foi composto por solução do poli(ácido acrílico) (PAA) e solução de óxido de titânio (TiO2), respectivamente. Os materiais utilizados para a obtenção dos filmes e os filmes finos nanoestruturados produzidos foram caracterizados por meio de diversas técnicas. As regiões de absorção das soluções coloidais inorgânicas foram determinadas por espectroscopia de absorção molecular no ultravioleta-visível (UV-Vis) e apresentaram absorção em 320 nm (TiO2) e 440 nm (CdSe). O diâmetro das nanopartículas inorgânicas de TiO2 e de CdSe foram mensurados por difração de raios X (DRX) e microscopia eletrônica de transmissão (MET), revelando valores em escala nanométrica. Observou-se no difratograma do pó nanoparticulado de TiO2 que a fase predominante no mesmo é a anatase, e que houve uma sobreposição dos picos de maior intensidade do TiO2 e do CdSe, ambos em 2q = 25,3°. O espectro de refletância difusa (RDUV-Visível) dos filmes automontados apresentou valores compatíveis com as das soluções formadoras dos filmes, indicando que os mesmos apresentam aplicação em dispositivos fotossensíveis. Através dos comprimentos de onda obtidos a partir das técnicas de UV-Vis e RDUV-Vis foi possível estimar os valores de energia de bandas proibidas (Ebg) para os semincondutores TiO2 e CdSe. As espessuras dos filmes foram determinadas pelas técnicas de perfilometria e por microscopia eletrônica de varredura (MEV), e encontram-se na ordem de grandeza micrométrica. Pelas micrografias de MEV foi possível avaliar a superfície dos filmes que revelaram alta rugosidade, formação de ilhas de TiO2 e aglomeração de grãos esféricos (Se). Nas imagens de MET, observou-se a distribuição das nanopartículas dos semicondutores na seção transversal dos filmes, corroborando as aglomerações observadas por MEV. / Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-06-05T16:53:57Z No. of bitstreams: 1 Dissertacao Ana Claudia R Faria.pdf: 12916246 bytes, checksum: 8f6d72e15170865b53f4fc6c7da263b1 (MD5) / Made available in DSpace on 2014-06-05T16:53:57Z (GMT). No. of bitstreams: 1 Dissertacao Ana Claudia R Faria.pdf: 12916246 bytes, checksum: 8f6d72e15170865b53f4fc6c7da263b1 (MD5) / The search for materials that can be modified at molecular level has been the subject of several studies worldwide. Thus, the production techniques of thin films stand out due to the possibility of reducing costs and improving the efficiency of systems, such as photosensitive systems. In this context, the aim of this study was to obtain and characterize thin films using the self-assembly technique (layer by layer technique or LbL). The thin films were deposited on different substrates (glass coverslips, silicon and polystyrene). In this work two different multilayer sets combined with two different proportions of each solution system were deposited. The cationic system was composed by the poly(diallyldimethilammonium) (PDDA) organic polyelectrolyte solution and the cadmium selenide (CdSe) inorganic semiconductor colloidal solution. The anionic system was composed by the poly(acid acrylic) (PAA) solution and the titanium dioxide (TiO2) solution, respectively. The materials used for the achievement of films and nanostructured thin films produced were characterized through various techniques. The absorption regions of inorganic colloidal solutions were determined by UV-Vis spectroscopy and presented absorption at 320 nm (TiO2) and 440 nm (CdSe). The resulting inorganic nanoparticles diameter of TiO2 and CdSe were measured by X ray diffraction (XRD) and transmission electron microscopy (TEM), resulting in values at nanometric scale. It was observed in the nanoparticle TiO2 powder diffractogram that anatase is the most abundant phase, and that there was an overlap of the highest intensity diffraction peaks of TiO2 and CdSe, both at 2q = 25.3 °. The diffuse reflectance spectrum (RDUV-Vis) of self-assembled films presented values compatible with those of the film forming solutions. Using the wavelengths obtained from the UVVis and Vis-RDUV techniques it were possible to evaluate values for the energy band gap (Ebg) seminconductors TiO2 and CdSe. The thicknesses of the films were determined by profilometry and scanning electron microscopy (SEM) techniques, and they are in the micrometric order of magnitude. Using the SEM micrographs, it was possible to evaluate the surface of the films that show a high roughness, the formation of TiO2 clumps and the agglomeration spherical selenium clusters. In TEM images, the distribution of the semiconductor nanoparticles in cross-section of films can be observed, confirming agglomerations observed by SEM.

Neste trabalho foram investigadas a morfologia, a estrutura cristalina e as propriedades térmicas e reológicas de uma blenda de polipropileno isotático (i-PP) e copolímero de etileno, propileno e dieno (EPDM), preparada em laboratório, por processo de mistura reativa, com a adição de argila Cloisite 15A e submetida à deformação uniaxial por tração e compressão à temperatura ambiente. As técnicas utilizadas para caracterização foram a Difração de Raios-X (DRX), o Espalhamento de Raios-X de Baixo Ângulo (SAXS), a Microscopia Eletrônica de Varredura (MEV), a Microscopia Eletrônica de Transmissão (MET), a Calorimetria Diferencial de Varredura (DSC), a Análise Termogravimétrica (TGA) e a Espectroscopia no Infravermelho por Transformada de Fourier (FTIR). A MEV permitiu observar que ocorreu interação entre a blenda e a argila, o que foi corroborado pelas imagens de MET, a qual permitiu verificar a existência de argila intercalada entre as lamelas da blenda, bem como a existência de alguns pontos de aglomeração da argila na blenda. A análise de DRX também confirmou a intercalação da argila pelo polímero. Da mesma forma, o SAXS nos mostrou que existe um aumento no espaçamento lamelar, com a introdução da argila. Por fim, foi observado também que a deformação uniaxial por compressão do material provocou a quebra de domínios cristalinos na blenda, enquanto na deformação uniaxial por tração o grau de cristalinidade inicial foi mantido. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2015-10-07T17:04:58Z No. of bitstreams: 1 Dissertacao Arthur Thompson.pdf: 2821768 bytes, checksum: 1e4375e8bb47bdeb964a7ef45a77ae48 (MD5) / Made available in DSpace on 2015-10-07T17:04:58Z (GMT). No. of bitstreams: 1 Dissertacao Arthur Thompson.pdf: 2821768 bytes, checksum: 1e4375e8bb47bdeb964a7ef45a77ae48 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior. / In this work were investigated the morphological, themal and rheological properties of a isotactic polypropylene/ethylene-propylene-diene terpolymer rubber/nanoclay Cloisite 15A composite, prepared by mixed melt and submitted to uni-axial plane-strain compression and stretching deformations, both at room temperature. The techniques used for characterization were Wide Angle X-ray Diffraction (WAXD), Small Angle X-ray Scattering (SAXS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis and Fourier Transform Infrared Spectroscopy (FTIR). The SEM images showed that interaction occured between the clay and the blend, which was corroborated by the TEM images, where it was show the intercalation between blend and clay, as well as the existence of some points of clay’s aglomeration in the blend. The WAXD analysis also confirmed the intercalation of the clay in the blend. Furthermore, the SAXS showed an increase in the lamellar long period with the addition of clay. With the mapping of chemical elements we could see the dispersion of clay’s organometalics into the blend. Finally, it was verified that the uni-axial plain strain compression deformation of the composites contribute to the break of crystalline domains in the blend, while in the uniaxial stretching deformation the degree of initial cristallinity was sustained.

Neste trabalho foram investigadas a morfologia, a estrutura cristalina e as propriedades térmicas e reológicas de uma blenda de polipropileno isotático (i-PP) e copolímero de etileno, propileno e dieno (EPDM), preparada em laboratório, por processo de mistura reativa, com a adição de argila Cloisite 15A e submetida à deformação uniaxial por tração e compressão à temperatura ambiente. As técnicas utilizadas para caracterização foram a Difração de Raios-X (DRX), o Espalhamento de Raios-X de Baixo Ângulo (SAXS), a Microscopia Eletrônica de Varredura (MEV), a Microscopia Eletrônica de Transmissão (MET), a Calorimetria Diferencial de Varredura (DSC), a Análise Termogravimétrica (TGA) e a Espectroscopia no Infravermelho por Transformada de Fourier (FTIR). A MEV permitiu observar que ocorreu interação entre a blenda e a argila, o que foi corroborado pelas imagens de MET, a qual permitiu verificar a existência de argila intercalada entre as lamelas da blenda, bem como a existência de alguns pontos de aglomeração da argila na blenda. A análise de DRX também confirmou a intercalação da argila pelo polímero. Da mesma forma, o SAXS nos mostrou que existe um aumento no espaçamento lamelar, com a introdução da argila. Por fim, foi observado também que a deformação uniaxial por compressão do material provocou a quebra de domínios cristalinos na blenda, enquanto na deformação uniaxial por tração o grau de cristalinidade inicial foi mantido. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior. / In this work were investigated the morphological, themal and rheological properties of a isotactic polypropylene/ethylene-propylene-diene terpolymer rubber/nanoclay Cloisite 15A composite, prepared by mixed melt and submitted to uni-axial plane-strain compression and stretching deformations, both at room temperature. The techniques used for characterization were Wide Angle X-ray Diffraction (WAXD), Small Angle X-ray Scattering (SAXS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis and Fourier Transform Infrared Spectroscopy (FTIR). The SEM images showed that interaction occured between the clay and the blend, which was corroborated by the TEM images, where it was show the intercalation between blend and clay, as well as the existence of some points of clay’s aglomeration in the blend. The WAXD analysis also confirmed the intercalation of the clay in the blend. Furthermore, the SAXS showed an increase in the lamellar long period with the addition of clay. With the mapping of chemical elements we could see the dispersion of clay’s organometalics into the blend. Finally, it was verified that the uni-axial plain strain compression deformation of the composites contribute to the break of crystalline domains in the blend, while in the uniaxial stretching deformation the degree of initial cristallinity was sustained.

Ce travail se concentre sur le développement d'une procédure expérimentale d’essai mécanique à haute vitesse de déformation de matériaux. La nouveauté de ce travail est l'utilisation de champs d’accélération mesurés comme cellule de force, évitant la nécessité des mesures des forces externes. Pour identifier les paramètres constitutifs des matériaux testés à partir des mesures de champs, la méthode champs virtuels (MCV) basé sur le principe des puissances virtuelles (PPV) est utilisée. En dynamique, avec la MCV, il est possible de définir des champs virtuels qui mettent à zéro les puissances virtuelles des forces externes. Au lieu de cela, l'accélération obtenue grâce à une double dérivation temporelle des déplacements peut être utilisée comme une cellule de force. Enfin, les paramètres élastiques peuvent être identifiés directement à partir d’un système linéaire qui se construit en réécrivant le PPV avec autant de champs virtuels indépendants que d’inconnues à identifier. Cette procédure est d'abord validée numériquement par des simulations éléments finis puis mise en œuvre expérimentalement en utilisant deux configurations d’impact différentes. Les résultats confirment que effets inertiels peuvent être utilisés pour identifier les paramètres des matériaux sans la nécessité de mesurer la force d’impact, et sans exigence de déformations uniformes comme dans les procédures actuelles basées sur le montage de barres d’Hopkinson. Ces nouveaux développement ont le potentiel de mener à de nouveaux essais standards en dynamique rapide / This work focuses on the development of a novel experimental procedure for high strain rate testing of materials. The underpinning novelty of this work is the use of the full-field acceleration maps as a volume distributed load cell, avoiding the need for impact force measurement. To identify the constitutive parameters of materials from the full-field data, the Virtual Fields Method (VFM) based on the principle of virtual work is used here. In dynamics, using the VFM, it is possible to define particular virtual fields which can zero out the virtual work of the external forces. Instead, the acceleration obtained through second order temporal differentiation from displacement can be used as a load cell. Finally, the elastic parameters can be identified directly from a linear system which is built up through rewriting the principle of virtual work with as many independent virtual fields as unknowns. Thus, external force measurement is avoided, which is highly beneficial as it is difficult to measure in dynamics. This procedure is first numerically validated through finite element simulations and then experimentally implemented using different impact setups. Both results confirm that inertial effects can be used to identify the material parameters without the need for impact force measurements, also relieving the usual requirements for uniform/uniaxial stress in SHPB like test configurations. This exciting development has the potential to lead to new standard testing techniques at high strain rates

Ni/TiC metal matrix composites have been processed using the laser engineered net shaping (LENS) process. As nickel does not form an equilibrium carbide phase, addition of a strong carbide former in the form of titanium reinforces the nickel matrix resulting in a promising hybrid material for both surface engineering as well as high temperature structural applications. Changing the relative amounts of titanium and carbon in the nickel matrix, relatively low volume fraction of refined homogeneously distributed carbide precipitates, formation of in-situ carbide precipitates and the microstructural changes are investigated. The composites have been characterized in detail using x-ray diffraction, scanning electron microscopy (including energy dispersive spectroscopy (XEDS) mapping and electron backscatter diffraction (EBSD)), Auger electron spectroscopy, and transmission (including high resolution) electron microscopy. Both primary and eutectic titanium carbides, observed in this composite, exhibited the fcc-TiC structure (NaCl-type). Details of the orientation relationship between Ni and TiC have been studied using SEM-EBSD and high resolution TEM. The results of micro-hardness and tribology tests indicate that these composites have a relatively high hardness and a steady-state friction coefficient of ~0.5, both of which are improvements in comparison to LENS deposited pure Ni.

A busca por materiais que possam ser modificados em nível molecular tem sido o alvo de numerosas pesquisas no mundo. Desta maneira, as técnicas de fabricação de filmes finos se destacam devido à possibilidade de se reduzir custos e melhorar a eficiência de sistemas como, por exemplo, os fotossensíveis. Neste contexto, o objetivo deste trabalho foi a obtenção e caracterização de filmes finos através da técnica de automontagem (técnica "camada por camada" ou Layer-by-Layer). Os filmes foram depositados sobre diversos substratos (lamínula de vidro, silício e poliestireno). Nesse trabalho foram depositados dois conjuntos diferentes de multicamadas combinados com duas proporções diferentes de cada sistemas de soluções. O sistema catiônico foi composto pela solução do polieletrólito orgânico PDDA e a solução coloidal do semicondutor inorgânico seleneto de cádmio (CdSe). O sistema aniônico foi composto por solução do poli(ácido acrílico) (PAA) e solução de óxido de titânio (TiO2), respectivamente. Os materiais utilizados para a obtenção dos filmes e os filmes finos nanoestruturados produzidos foram caracterizados por meio de diversas técnicas. As regiões de absorção das soluções coloidais inorgânicas foram determinadas por espectroscopia de absorção molecular no ultravioleta-visível (UV-Vis) e apresentaram absorção em 320 nm (TiO2) e 440 nm (CdSe). O diâmetro das nanopartículas inorgânicas de TiO2 e de CdSe foram mensurados por difração de raios X (DRX) e microscopia eletrônica de transmissão (MET), revelando valores em escala nanométrica. Observou-se no difratograma do pó nanoparticulado de TiO2 que a fase predominante no mesmo é a anatase, e que houve uma sobreposição dos picos de maior intensidade do TiO2 e do CdSe, ambos em 2q = 25,3°. O espectro de refletância difusa (RDUV-Visível) dos filmes automontados apresentou valores compatíveis com as das soluções formadoras dos filmes, indicando que os mesmos apresentam aplicação em dispositivos fotossensíveis. Através dos comprimentos de onda obtidos a partir das técnicas de UV-Vis e RDUV-Vis foi possível estimar os valores de energia de bandas proibidas (Ebg) para os semincondutores TiO2 e CdSe. As espessuras dos filmes foram determinadas pelas técnicas de perfilometria e por microscopia eletrônica de varredura (MEV), e encontram-se na ordem de grandeza micrométrica. Pelas micrografias de MEV foi possível avaliar a superfície dos filmes que revelaram alta rugosidade, formação de ilhas de TiO2 e aglomeração de grãos esféricos (Se). Nas imagens de MET, observou-se a distribuição das nanopartículas dos semicondutores na seção transversal dos filmes, corroborando as aglomerações observadas por MEV. / The search for materials that can be modified at molecular level has been the subject of several studies worldwide. Thus, the production techniques of thin films stand out due to the possibility of reducing costs and improving the efficiency of systems, such as photosensitive systems. In this context, the aim of this study was to obtain and characterize thin films using the self-assembly technique (layer by layer technique or LbL). The thin films were deposited on different substrates (glass coverslips, silicon and polystyrene). In this work two different multilayer sets combined with two different proportions of each solution system were deposited. The cationic system was composed by the poly(diallyldimethilammonium) (PDDA) organic polyelectrolyte solution and the cadmium selenide (CdSe) inorganic semiconductor colloidal solution. The anionic system was composed by the poly(acid acrylic) (PAA) solution and the titanium dioxide (TiO2) solution, respectively. The materials used for the achievement of films and nanostructured thin films produced were characterized through various techniques. The absorption regions of inorganic colloidal solutions were determined by UV-Vis spectroscopy and presented absorption at 320 nm (TiO2) and 440 nm (CdSe). The resulting inorganic nanoparticles diameter of TiO2 and CdSe were measured by X ray diffraction (XRD) and transmission electron microscopy (TEM), resulting in values at nanometric scale. It was observed in the nanoparticle TiO2 powder diffractogram that anatase is the most abundant phase, and that there was an overlap of the highest intensity diffraction peaks of TiO2 and CdSe, both at 2q = 25.3 °. The diffuse reflectance spectrum (RDUV-Vis) of self-assembled films presented values compatible with those of the film forming solutions. Using the wavelengths obtained from the UVVis and Vis-RDUV techniques it were possible to evaluate values for the energy band gap (Ebg) seminconductors TiO2 and CdSe. The thicknesses of the films were determined by profilometry and scanning electron microscopy (SEM) techniques, and they are in the micrometric order of magnitude. Using the SEM micrographs, it was possible to evaluate the surface of the films that show a high roughness, the formation of TiO2 clumps and the agglomeration spherical selenium clusters. In TEM images, the distribution of the semiconductor nanoparticles in cross-section of films can be observed, confirming agglomerations observed by SEM.