Made available in DSpace on 2014-10-09T12:35:14Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:01Z (GMT). No. of bitstreams: 0 / Nas últimas décadas, questões sobre o controle de emissões em motores à combustão interna e sobre a redução de consumo de combustível vêm sendo debatidas globalmente, com claros desdobramentos em especificações de controles mais restritos, a fim de permitir a comercialização de novos motores à combustão interna a consumidores mais exigentes, que presam pela qualidade de vida e meio ambiente. Mesmo com a introdução de novas tecnologias, os motores ainda apresentam uma grande perda da energia gerada por conta do atrito mecânico. Com base neste contexto, os projetos dos novos motores visam uma melhor eficiência térmica e mecânica, com auxílio de soluções de engenharia que possam beneficiar o desempenho dos motores, resultando em uma melhor queima do combustível e menor atrito. Um dos contribuintes mais relevantes para o atrito num motor é o sistema pistão-anel de pistão-camisa de cilindro que é o foco de muitos trabalhos em busca da redução das perdas por atrito. As propriedades dos filmes à base de carbono tipo diamante (Diamond-Like Carbon - DLC) são bem conhecidas por apresentam alta resistência ao desgaste e baixo coeficiente de atrito, tornando-se adequados para diferentes aplicações tribológicas. O presente trabalho discute a viabilidade técnica de se aplicar um filme DLC amorfo hidrogenado, com gradiente de composição química, sobre a superfície interna brunida de camisas de cilindro para redução do atrito. A metodologia aborda duas espessuras de filme: 2,5 e 12,5 μm, depositadas pelo processo de deposição química em fase vapor assistida por plasma (PACVD), como alternativa para redução do atrito do motor e, consequentemente, redução no consumo específico de combustível, e ainda na redução do desgaste dos anéis de pistão e da superfície de trabalho da camisa de cilindro. Comparando camisas de cilindro com mesma rugosidade na superfície interna, denominadas camisas de referência (sem revestimento interno) e camisas recobertas com filme DLC, testes de bancada com movimento recíproco de contato mostraram redução do coeficiente de atrito (COF) em até 19%. Testes de motor ciclo Otto e Diesel em banco de prova com dinamômetro conferiram, respectivamente, uma redução da pressão média efetiva de atrito (FMEP) do motor em até 12% e consumo específico de combustível (BSFC) em até 2,5% em rotações de 1000 a 1400 rpm. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Submitted by Maria Eneide de Souza Araujo (mearaujo@ipen.br) on 2015-02-20T18:11:07Z No. of bitstreams: 0 / Made available in DSpace on 2015-02-20T18:11:07Z (GMT). No. of bitstreams: 0 / O processo de fosfatização é amplamente utilizado na indústria de tratamento de superfície de metais, especialmente de placas de baixa espessura, melhorando a aderência entre a superfície do metal e o revestimento de tinta, e aumentando a durabilidade dos sistemas de pintura contra ataques corrosivos. Os fosfatos tricatiônicos contendo zinco, níquel e manganês são comumente aplicados em aço, e muito se discute sobre a substituição do níquel por outro elemento com o objetivo de obter um fosfato mais amigável ao meio ambiente, tanto em seus processos como para as pessoas envolvidas. O nióbio tem sido avaliado nesse sentido. Os impactos ambientais mais significativos dos fosfatos estão relacionados com a presença do níquel e do cromo hexavalente utilizado no processo, devido a exposição ao contato humano e a contaminação residual da água e do solo. Seguindo a linha de pesquisa que estudou a substituição do níquel por nióbio em camadas formadas sobre o aço carbono, o presente estudo avaliou e caracterizou camadas de fosfato contendo zinco, manganês e nióbio, formadas em aço galvanizado, comparando os resultados com o fosfato de zinco, manganês e níquel, bem como com o fosfato de zinco e manganês, sem a adição de nióbio. Embora o uso de cromo não seja recomendado mundialmente, ainda hoje é utilizado no processo de selagem da porosidade da camada de fosfato, em banhos contendo cromo hexavalente, que é reconhecido por ser carcinogênico, estando associado a várias doenças. Devido às características passivantes do nióbio, este estudo também avaliou o banho tricatiônico contendo oxalato amoniacal de nióbio, como etapa de passivação das camadas, tanto em banhos bicatiônicos, quanto nos tricatiônicos, com resultados muito interessantes como opção de substituição do cromo hexavalente. Os resultados obtidos neste trabalho são promissores, pois algumas das formulações contendo nióbio se apresentaram equivalentes ao fosfato contendo níquel, tanto em morfologia, verificadas em microscopia eletrônica de varredura, ensaios gravimétricos, de porosidade e de aderência, quanto nas características de proteção anticorrosivas, verificadas nos ensaios eletroquímicos e em câmara de névoa salina. Embora apresentando eficácia compatível com fosfato contendo níquel, ajustes na estabilidade dos banhos ainda são necessários e mais estudos utilizando técnicas voltadas para o entendimento dos fenômenos que ocorrem na base dos poros, devem orientar as próximas etapas da linha de pesquisa. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

With the growing impact of climate change on both political decisions and how companies develop their products, it is increasingly important to find environmentally friendly alternatives to fossil-based materials. One of the more interesting materials in this respect is cellulose, which is the world's most naturally occurring polymer and can be used in a variety of applications. One way to modify the fibers and to change their properties is to use a method called Layer-by-Layer (LbL) treatment where two polymers of opposite charge are alternately adsorbed to the fiber surface. Another possibility is to oxidize the cellulose in the fibers to obtain a higher charge. This means that the fibers can adsorb a higher amount of cationic additives and that the fibers swell more which means that they are plasticized and can create stronger joints between the fiber surfaces in the dry state, which results in stronger dry fiber networks. However, wood-based fibers are small and inhomogeneous, both chemically and morphologically, which means that it is necessary to use model systems to be able to clarify, in detail, how treated and untreated surfaces interact with each other at a molecular level. One model system that can be used to investigate how cellulose fibers are affected by coating using the LbL method is to use spherical beads made from regenerated cellulose. In the present work, these beads were treated with polyallylamine hydrochloride (PAH) and hylauronic acid (HA) as well as with PAH and alginate (Alg) before being allowed to dry together and then subjected to tensile testing to clarify the adhesion between the surfaces. The beads were treated with five and ten bi-layers of these polymers, respectively, and then dried together on an AKD-coated surface, to avoid adhesion to the underlying surface, to examine the adhesion between the beads. The adhesion increased when treated with LbL and became higher upon adsorption of multiple layers of polyelectrolytes and the Alg / PAH system showed the greatest increase. Ten-layer samples of Alg / PAH were also tested after a solution of calcium chloride was added during drying, resulting in poorer adhesion between the beads. / Med klimatfrågans växande inverkan på både politiska beslut och hur företagen utvecklar sina produkter så läggs det allt större vikt vid att hitta miljövänliga alternativ till fossilbaserade material. Ett av de mer intressanta materialen är cellulosa vilket är världens mest naturligt förekommande polymer och som kan användas i en rad olika tillämpningar. Ett sätt att modifiera fibrerna och att ändra deras egenskaper är att använda sig av en metod som kalls Layer-by-layer (LbL) behandling där två polymerer mot motsatt laddning växelvis adsorberas till fiberytan. En annan möjlighet är att oxidera cellulosan i fibrerna så att de erhåller de en högre laddning. Detta innebär dels att fibrerna kan adsorbera en högre mängd katjoniska tillsatskemikalier samt att fibrerna sväller mera vilket innebär att de plasticeras och kan skapa starkare fogar mellan fiberytorna i torrt tillstånd vilket resulterar i starkare torra fibernätverk. Vedbaserade fibrer är dock små och inhomogena såväl kemiskt som morfologiskt vilket innebär att det är nödvändigt att använda modellsystem för att kunna klarlägga, i detalj, hur behandlade och icke behandlade ytor växelverkar med varandra på en molekylär nivå. Ett modellsystem som kan användas för att undersöka hur cellulosafibrer påverkas av att beläggas med hjälp av LbL metoden är att använda sig av sfäriska kulor tillverkade från regenererad cellulosa. I föreliggande arbete behandlades dessa kulor med polyallylaminhydroklorid (PAH) och hylauronsyra (HA) samt med PAH och alginat (Alg) innan de tilläts torka ihop och därefter utsattes för dragprovning för att klarlägga adhesionen mellan ytorna. Kulorna behandlades med fem respektive tio bilager av dessa polymerer och torkades sedan ihop på en AKD-belagd yta, för att undvika adhesion till den underliggande ytan, för att undersöka adhesionen mellan kulorna. Adhesionen ökade när de behandlades med LbL och blev högre vid adsorption av flera lager polyelektrolyter och systemet med Alg/PAH resulterade i den största ökningen. Prover med tio lager av Alg/PAH testades även efter att en lösning av kalciumklorid tillsattes under torkningen vilket resulterade i en sämre adhesion mellan kulorna.

Many of the flows in nature are turbulent. To modify turbulent flows, nature serves itself with different types of coatings. Sharks have riblets-like structures on their skin, fishes have slime with polymers and the surface of the lotus flower has superhydrophobic properties. However many times these naturally occurring coatings also serve other purposes. Due to millions of years of adaption, there are anyway many reasons to be inspired by these. The present work is an investigation of nature inspired coatings with the aim of passive flow manipulations. The goal of the investigation has not been to achieve drag reduction, but to achieve a better understanding of the effect of these coatings on turbulent flows. Simulations have been performed in a channel flow configuration, where the boundary condition on one wall has been modified. A macroscopic description has been used to simulate superhydrophobic and porous-like surfaces and a microscopic description has been used to simulate suspended fibers, both rigid and flexible, attached to the channel wall. For the macroscopic description, a pseudo-spectral method was used and for the microscopic description a lattice-Boltzmann method was used. The superhydrophobic modification was implemented using a general slip tensor formulation. In agreement with earlier results, drag reduction was achieved with slip in the streamwise direction and slip in the spanwise direction resulted in drag increase. Non-zero off-diagonal terms in the slip tensor resulted in a slight drag increase, but with rather similar flow behaviour. Transpiration, imitating a porous media, gave rise to drag increase and severely modified the turbulent structures, forming two-dimensional structures elongated in the spanwise direction. For the short fibers, neither rigid nor flexible fibers modified the velocity field to a large extent. The fibers gave rise to recirculation regions and these were seen to be stronger below high-speed streaks. Flexible fibers showed similarities to porous media through a coupling of wallnormal velocity and pressure fluctuations, and this was not seen for the rigid fibers. The fiber deflections were seen to correlate well with the pressure fluctuations. / Många naturligt förekommande flöden är turbulenta. Naturen har också gett upphov till flera typer av ytskikt som kan påverka dessa. Hajars skinn har räfflor, fiskar har slem som innehåller polymerer och lotusblommans yta har superhydrofobiska egenskaper, men ofta har dessa naturliga ytskikt också andra egenskaper. På grund av miljoner år av anpassning så finns det ändå många skäl att studera dessa. Detta arbete är en studie av naturinspirerade ytskikt, där målet har varit passiva flödesmanipulationer. Målet har inte varit att åstadkomma en ytfriktionsminskning, utan att få en bättre förståelse om hur dessa ytskikt påverkar turbulenta flöden. Simuleringar har utförts i en kanalliknande geometri, där en kanalväggs randvillkor har modifierats. En makroskopisk beskrivning har använts för att simulera superhydrofobiska och porösa ytor och en mikroskopisk beskriving har använts för att simulera fibrer, både stela och böjbara, fastsatta på en kanalvägg. För flödet med det makroskopiskt beskrivna randvillkoret har en pseudospektral metod använts och för flödet med det mikroskopiskt beskrivna randvillkoret har en lattice-Boltzmannmetod använts. Den superhydrofobiska ytan implementerades genom en generell tensorformulering. Ett randvillkor med nollskild hastighet i kanalens riktning gav upphov till en ytfriktionsminskning och ett randvillkor med nollskild hastighet vinkelrät mot kanalens riktning gav upphov till en ökad ytfriktion, i överensstämmelse med tidigare resultat. Nollskilda icke-diagonala tensorelement gav upphov till en smärre ökning av ytfriktionen, utan att nämnvärt förändra flödet. De porösa ytorna gav upphov till en ytfriktionsökning och hade stor inverkan på de turbulenta strukturerna. Dessa ytor bildade tvådimensionella struturer vinkelrät mot kanalens riktning. Varken de stela eller de böjbara fibrerna gav upphov till stora ändringar i hastighetsfältet. Däremot uppstor cirkulationszoner och dessa var starkare under stråkstrukturer med hög hastighet. De böjbara fibrerna uppvisade likheter med porösa material genom en interaktion mellan det vertikala hastighetsfältet och de turbulenta tryckfluktuationerna. Denna interaktion uppstod inte för de stela fibrerna. Fibrernas böjning korrelerade också i stor utsträckning till tryckfluktuationerna.

To develop a hydrogel sensor system using the Hall effect to detect the degree of swelling, gels containing high concentrations of magnetic particles are necessary to induce a strong magnetic field. For this purpose, hydrogels based on poly(N-isopropylacrylamide) cross-linked with Laponite XLS are modified with various magnetic nanoparticles. The focus of this work is to introduce high particle densities with a homogeneous distribution into the gel. Particles are coated with 3-(trimethoxysilyl)propyl methacrylate to bind them into the network structure. The swelling behavior and temperature response of gels containing pure and modified particles are compared to the unmodified clay gel. Ferrogels are further synthesized in a magnetic field to permanently align magnetic nanoparticles in the network. This results in permanently embedded rod-like structures spanning the entire length of the gel. The influence of this anisotropic distribution on the mechanical properties of the hydrogel is investigated through compression measurements.

Le chrome dur, utilisé comme revêtement de tige d’actionneurs hydrauliques linéaires, a été interdit pour risque sanitaire (directive européenne REACH). A cet effet, un revêtement de WS2 a été sélectionné par Safran Landing Systems pour substituer le chrome dur comme revêtement de tige de piston de frein hydraulique. La démarche de sélection utilisée, est limitée par son incapacité à expliquer les performances observées et démontre le besoin d’une démarche de sélection d’autant plus appropriée que la notion d’étanchéité des actionneurs hydrauliques linéaires est « floue ». Comme, la tribologie n’a pas vocation à caractériser les revêtements de surface, parce que son plus petit objet d’étude est un triplet tribologique, cette étude propose l’évaluation de la compatibilité tribologique du revêtement de WS2, avec la fonction d’étanchéité. La démarche utilisée montre que l’étanchéité est régie, par un critère en pression, et par une vérification des caractéristiques tribologiques du système tige/joints requises pour la réalisation de l’étanchéité ; ce qui nécessite un piston hydraulique instrumenté. L’absence de ce piston est compensée par une « caractérisation tribologique approchée » du contact tige/joints, qui associe les expertises tribologiques de pistons hydrauliques d’essais de qualification, appuyées par un modèle éléments finis (EF) du piston hydraulique d’une part, et les résultats d’un essai de frottement piste/joints, conçus à cet effet à l’aide d’un modèle EF d’autre part. Les résultats montrent que le système tige/joints présente de bonnes caractéristiques tribologiques pour le facteur de frottement et l’usure, alors que la localisation de l’accommodation de vitesses dans le cas du contact tige/joint d’étanchéité, accélère le débit source du revêtement et limite sa durée de vie. Enfin, cette thèse comble un vide méthodologique en proposant, une démarche de sélection d’un revêtement pour une application tribologique, et une démarche de triboconception d’un actionneur hydraulique linéaire dans le cas d’un fonctionnement quasi-statique. / Hard chromium used as rod coating in linear hydraulic actuators has been forbidden by the European Directive REACH. In this situation, a WS2 coating has been selected by Safran Landing Systems to replace the hard chromium coating on rod pistons actuators of landing gear braking systems. The selection method was unable to explain the observed performance, and shows the lack of an appropriate methodology for the rod coating selection, mainly because the sealing concept is rather vague. Since tribology is not intended to characterize surface coatings, because its smallest object of study is a tribological triplet, this study proposes the evaluation of the tribological compatibility of the WS2 coating with the sealing function of the hydraulic piston. The adopted approach shows that the sealing performance is governed by a rod/seal contact pressure criterion and by the verification of the tribological characteristics of the rod/seal contact required to achieve a sealing performance. This tribological characterization requires an instrumented hydraulic piston. The absence of this piston is compensated by an "approximate tribological characterization" of the rod/seal contact, which combines the tribological expert analysis of hydraulic pistons of qualification tests, supported by a finite elements model (FE) of the hydraulic piston, and the results of a plate rod/seal friction test, designed for this purpose using another FE model. The results show that the rod/seal contact exhibits good tribological characteristics for the friction factor and wear, whereas the location of the velocity accommodation in the case of the rod/anti-extrusion seal contact accelerates the 3rd body generation of the coating and limits its life expectancy. Finally, this thesis fills a methodological lack by proposing a method of selecting a coating for a tribological application and a triboconception method of a linear hydraulic actuator in the case of quasi-static operating conditions.

The cell plasma membrane is an interactive interface playing an important role in regulating cell-to-cell, cell-to-tissue contact, and cell-to-environment responses. This environment-responsive phospholipid layer consisting of multiple dynamically balanced macromolecules, such as membrane proteins, carbohydrate and lipids, is regarded as a promising platform for various surface engineering strategies. Through different chemical modification routes, we are able to incorporate various artificial materials into the cell surface for biomedical applications in small molecule and cellular therapeutics. In this dissertation, we establish two different cell coating techniques for applications of cell-mediated drug delivery and the localization of cell-based therapies to specific tissues. The first part of this dissertation establishes a membrane-associated hydrogel patch for drug delivery. The crosslinking of a grafted polymeric patch from a mammalian cell membrane is achieved through surface-mediated photolithographic polymerization. With the use of photomask, the formation of nanoparticle-loaded PEGDA hydrogel is controlled to deposit various geometric features on photoinitiator-immobilized surfaces. Through microarray patch patterning, we analyzed the influence of processing parameters on the accuracy of polymer patterning on a microarray. We then optimized the patterning approach for the formation of PEGDA patches on live A549 cells. In the second part of this dissertation, we study the use of tissue-adhesive coatings to improve the retention of therapeutic mesenchymal stem cells (MSCs) in the heart following intramyocardial or intravenous injection. MSCs were coated with antibodies against ICAM1 to adhere to CAM-overexpressed endothelium present in the heart following MI. Through intramyocardial or intravenous delivery, we observe higher number of coated cells retained in the heart over uncoated ones, supporting enhanced affinity for the inflamed endothelium near the infarct. We correlate the detachment force of antigen-interacted MSCs by a parallel laminar flow assay with the density of ICAM on the substrate and the density of anti-ICAM on the MSC surface. MSC retention on CAMmodified surfaces or activated HUVECs was significantly increased on antibody-coated groups (~90%) under physiologically hemodynamic forces (< 30dyne/cm2), compared to uncoated MSCs (~20%). Moreover, a dramatic reduction of immune cell quantity was observed after intravenous injection, indicating the enhanced immunoregulatory efficacy by systemically delivering ICAM-adhesive MSCs to the site of inflammation.

Superparamagnetic iron oxide (Fe3O4 and γ-Fe2O3) nanoparticles (IONPs) are of great in-terest as a diagnostic and/or therapeutic aid. Several IONPs with biocompatible polymer coatings have been approved for clinical use, as MRI contrast agents. IONPs conjugated to targeting ligands and therapeutic agents are being investigated for targeted drug deliv-ery applications. The superparamagnetic properties of IONPs are also helpful for magnetic field assisted localization to specific target sites and for in situ MRI applications. This thesis primarily focuses on the synthesis and surface modifications (with biocompatible polymers including dextran, poly(ethylene glycol) (PEG), dextran, poly(ethyl methacry-late) (PEMA), poly(hydroxyethyl methacrylate) (PHEMA), etc.) of IONPs. The IONPs were prepared following the classical co-precipitation method and a novel reduction-hydrolysis method. Initial studies used bovine serum albumin (BSA) to examine the ca-pabilities of polymer coated IONP to deliver a model protein therapeutic. Gel migration studies using BSA physisorbed onto polymer coated IONP under gradient magnetic field of an MRI showed that the IONPs had limited control in transporting the protein. Cova-lent linking of therapeutics to IONP core can improve the time window of formers con-trollability using magnetic field. To facilitate covalent conjugations, functional silane coated IONPs (with surface amino and carboxylic acid) were prepared as general precur-sors. The utility of silane coated IONPs for bioconjugations was demonstrated by cova-lently linking PEG diacid through surface amino groups and by linking of BSA through surface carboxylic acid groups. The biocompatibility of the IONPs synthesized following the novel reduction-hydrolysis method were assessed in vitro on cell culture models using toxicity assays. The versatile reduction-hydrolysis method was further extended, as a general method to prepare several early transition metal oxide NPs (manganese oxide (Mn3O4), cobalt oxide (Co3O4), nickel/nickel oxide (Ni/NiO), copper/copper oxide (Cu/Cu2O) and zinc oxide (ZnO) NPs), silica nanoparticles with surface IONPs, and iron/iron oxide nanosheets.

The effect of substrate surface treatment (substrate sputter cleaning) in a cathodic arc plasma prior to unbalanced magnetron deposition of transition metal nitride coatings on the performance of the coated components has been investigated. In particular the influence of parameters such as ion species, ion energy and exposure time on the changes in substrate surface topography, microstructure and micro-chemistry were studied employing transmission electron microscopy, energy dispersive X-ray analysis, electron energy loss spectroscopy, X-ray diffraction, atomic force microscopy and optical microscopy. The consequences for both the microstructure of subsequently grown transition metal nitride coatings and their adhesion were elucidated. The relevance for practical applications was demonstrated using the example of dry high-speed milling tests, which showed that an appropriate choice of substrate surface pre-treatment parameters can double the life time of the coated tools. This was found to be due to an improved adhesion as a result of a combina-tion of reduced oxygen incorporation at the interface between coating and substrate and local epitaxial growth of the coating. The latter is promoted by certain sub-strate surface pre-treatment procedures, which provide clean surfaces with preserved crystallographic order.

Made available in DSpace on 2014-10-09T12:35:58Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:33Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP