Carbon nanotube (CNT) forests have outstanding thermal, electrical, and mechanical properties, which have generated significant interest as thermal interface materials (TIMs). Some drawbacks to using CNTs as TIMs include poor substrate adhesion, high interface resistances inhibiting thermal transport, and lack of electrical insulation in electronic component applications. It is thus useful to be able to modify CNTs to reduce their electrical conductivity while maintaining high thermal conductivity and interface conductance, and high mechanical compliance. A recent report suggests that nanoscale oxide coatings could be applied to CNTs in forests without changing the mechanical deformation behavior of the forests. Oxide coatings could also provide environmental stability as well as better adhesion to the substrate compared to pristine CNT forests. In this study, we investigated thermal and electrical resistance of CNT forests with an oxide coating. Low-pressure chemical vapor deposition (LPCVD) was used to produce CNTs on high-conductivity Si substrates. Plasma-enhanced atomic layer deposition (PALD) was used to deposit Al2O3 on individual CNTs in forests. This process was facilitated by O2 plasma pretreatment to functionalize the surface of the CNTs and nucleate oxide growth. Several analytical techniques were used to characterize the CNT-oxide composites, including scanning electron microscopy, Raman and X-ray photoelectron spectroscopy. Thermal conductivity and thermal interface resistance were measured using a modified photoacoustic technique. The oxide coating had no significant effect on the effective thermal conductivity of the forests, in contrast to expectations of increased phonon scattering. Electrical resistivity measurements were made and a threefold increase was observed for the oxide-coated forests. This approach could emerge as a promising route to create a viable TIM for thermally conductive and electrically insulating applications.

Le carbone-suie, ou “black carbon” (BC), contribue au réchauffement climatique avec un forçage positif de l’ordre de +1.1 W m-2 dont l’incertitude reste haute (de l’ordre de 90%). Ce forçage s’effectue à travers l’interaction aérosol-radiation et l’interaction aérosols-nuage. Ces deux mécanismes sont affectés par le degré de mélange des particules du BC avec divers matériaux non-réfractaires et non-absorbants. Cependant, les estimations du forçage radiatif considèrent rarement les effets du mélange interne. Par ailleurs le rôle du BC comme noyau glaçogène qui influence l’interaction aérosol-nuage est largement inconnu. L’objectif de cette thèse est de mieux comprendre les mécanismes par lesquels le degré de mélange interne du BC influence la variabilité des propriétés optiques du BC et les propriétés d’activation des noyaux glaçogènes contenant du BC.Dans le premier chapitre de cette thèse, nous avons exploré la variabilité spatiale et saisonnière du coefficient d’absorption massique -mass absorption cross-section (MAC)- dans l’atmosphère en Europe. Les valeurs de MAC sont déterminées à partir de concentrations de carbone élémentaire et de coefficients d’absorption observée à différentes stations d’observation européenne du réseau ACTRIS (Aerosol, Cloud and Trace gases Research InfraStructure). Les résultats montrent une faible variabilité spatiale du MAC avec une moyenne de 10 ± 2.5 m2 g-1 à 637 nm de longueur d’onde qui peut être considérée comme représentative du BC en Europe. Le cycle saisonnier du MAC est probablement lié à la composition chimique de l’aérosol et son état de mélange, qui provoque une augmentation du MAC.Dans le second chapitre on s’est intéressé au lien entre l’absorption du BC et son état de mélange après transport sur longue-distance. Ce travail se base sur des mesures effectuées dans le cadre du projet CLIMSLIP (CLimate IMpact of Short-Lived Pollutants and methane in the Arctic). Une campagne de mesure a été conduite sur la station de recherche Zeppelin au Svalbard, Norvège en Avril 2012. Les données acquises avec un Single Particle Soot Photometer (SP2) révélaient que le BC est généralement présent en mélange interne dont l’épaisseur moyenne de la couche superficielle de matériel non-absorbant est de 47 nm pour des particules de BC de diamètre compris entre 170 et 280 nm. Ce mélange interne conduit à une augmentation d’absorption de 46%. Elle entraîne cependant une diminution relativement faible de l’albédo de simple diffusion, de l’ordre de 1%.Enfin, la capacité du BC à agir comme noyaux glaçogène pour la formation de cristaux de glace a été étudiée sur le site de haute altitude du Jungfraujoch (Suisse) dans le cadre du “cloud and aerosol characterization experiment” (CLACE) en 2013. Les différents éléments du nuage étaient séparé à partir d’une prise d’entrée type ice-CVI connectée au SP2. Ce dispositif permet de sélectionner uniquement les cristaux de glace et quantifier la fraction de BC activée. Une réduction de la présence de BC dans les résidus de glace a été observée. Des mesures de l’épaisseur de la couche de mélange interne des particules contentant du BC ont montré que les résidus de cristaux de glace présentaient des enrobages bien plus épais comparée à l’aérosol total.Les résultats obtenus au cours de ce travail ont permis de mieux comprendre l’impact du degré de mélange interne sur les propriétés optiques du BC et sur son rôle dans la formation de cristaux de glace. Les propriétés optiques du BC évoluent en fonction de la saison, tandis que la formation d’une couche superficielle amplifie sa capacité d’absorption du rayonnement solaire. De plus, cette étude souligne l’importance du vieillissement atmosphérique du BC sur sa capacité à servir de noyau de nucléation de la glace. Enfin, il fournit une avancée au sujet des propriétés sensibles mesurées dans l’atmosphère avec des techniques innovantes qui permettront la simulation plus précise du forçage radiatif. / Black carbon (BC) induces a warming effect (RFBC = +1.1 W m-2 ± 90%) through two main pathways: aerosol-radiation interaction (RFari) and aerosol-cloud interaction (RFaci). Both BC-radiation and BC-cloud interaction are affected by the mixing of black carbon with other non-refractory and non-absorbing matter present in the atmosphere. An estimation of the global radiative forcing of BC rarely accounts for internal mixing of BC while the net global cloud radiative forcing is sensitive to assumptions in the initiation of cloud glaciation, which is mostly unknown for black carbon particles. Within this thesis we investigated the variability of the light absorbing properties of black carbon, the mixing of black carbon, and the impact on light absorption and ice activation.In the first part of this thesis we investigated the spatial and seasonal variability of the mass absorption cross section (MAC) over Europe. MAC values were determined from ambient observations of elemental carbon mass concentrations (mEC) and absorption coefficients (σap). The data had been acquired during several years at different background ACTRIS supersites spread over Europe. Site specific MAC values were found to be spatially homogeneous, suggesting that the overall MAC average 9.5 ± 1.9 m2 g-1 at a wavelength of 637 nm might be representative of BC at European background locations. The MAC values showed a distinct seasonal cycle at every station. This seasonality might be related to chemical composition and aging. We observed that the MAC value has a linear and positive proportionality with the non-absorbing matter mass fraction.The second part of the work focuses on the coating acquisition of BC and the induced absorption enhancement after long-range transport. Within the CLIMSLIP (climate impact of short-lived pollutants and methane in the Arctic) project field experiments were conducted at the Zeppelin research site in Svalbard, Norway, during the Arctic spring. SP2 data were used to characterize the BC size distribution and mixing. BC containing particles having a core diameter between 170 and 280 nm were found to have a median coating thickness of 47 nm. The relationship between coating thickness and BC absorption was simulated. The observed coating thickness enhanced the mass absorption cross section by 46%, which led to a decrease of less than 1% in the single scattering albedo.In the final part of this work, the role of black carbon as ice nuclei in mixed phase clouds was investigated at the high elevation measuring site Jungfraujoch (Switzerland) during the cloud and aerosol characterization experiment (CLACE) held in 2013. The ice-CVI inlet and a single particle soot photometer were used to select and quantify the ice activated BC particles. According to the observations, BC containing particles were depleted in the ice residuals. The activation efficiency showed a size dependency, with larger BC containing particles being activated more efficiently compared to smaller ones. Activated BC cores having a diameter between 170 and 240 nm showed a larger coating thickness (median = 53 nm) compared to the total aerosol (median = 16 nm).The results obtained in this thesis shed new light on the effect of the mixing state on the optical properties and cloud activation of black carbon particles. Absorbing properties of BC showed a distinct seasonal pattern, while aging was found to consistently increase its absorption behavior. However, black carbon was found not to act as ice nuclei in low tropospheric mixed-phase clouds, where the coating thickness might play a role in the activation efficiency. This work provides freshly determined physical properties derived from ambient observations that will improve the accuracy of future aerosol and cloud radiative forcing estimations.

Es wird gezeigt, dass mit dem Fluoreszenzmesssystem sowohl die Schichtdicke als auch die Aushärtung detektiert werden kann. Durch das Erstellen von Eichkurven ist es so möglich, vollflächig, die genaue Schichtdicke der Beschichtung im laufenden Prozess inline zu bestimmen und Abweichungen in Echtzeit entgegenzuwirken. Zudem können so Unregelmäßigkeiten bei der Aushärtung der Lacke direkt erkannt und bei unzureichender Aushärtung der Anteil von Fehlproduktionen minimiert werden. Auch bei hochvernetzten Acrylatklebstoffen konnte gezeigt werden, dass mit dem System eine genaue Analyse der inneren Festigkeit vorgenommen werden kann. Diese Klebstoffe, mit teilweise unterschiedlichem chemischen Aufbau, aber gleichem E-Modul, emittieren dasselbe Maß an Fluoreszenz. Somit konnte gezeigt werden, dass mit der Fluoreszenzmessung, unabhängig von der chemischen Struktur, gleichbleibende Intensitäten gemessen und damit der Aushärtegrad bestimmt werden kann. Zur genauen Bestimmung der Schichtdicken mit dem Fluoreszenzmesssystem ist es notwendig genaue Eichkurven für jedes einzelne System zu erstellen. Auch ist es, im Falle der Molkeprotein Beschichtungen notwendig weitere Formulierungen zu testen um eine exakte Vorhersage des Vernetzungsgrads zu gewährleisten. Durch die Ergebnisse die mit den Acrylatklebstoffen erzielt wurden stellt sich die Frage, inwieweit eine Korrelation zwischen der chemischen Struktur des untersuchten Materials und der gemessenen Fluoreszenz dabei besteht. Es sollte die Fluoreszenz von weiteren Materialien, unterschiedlicher chemischer Struktur, gemessen und überprüft werden, ob ein Zusammenhang zu deren E-Modul besteht. Außerdem sind Materialien wie z.B. Klebstoffe und Lacke auf Polyurethanbasis, deren Aushärtung erst nach mehreren Tagen oder Wochen abgeschlossen ist, interessant. Dabei stellt sich die Frage, ob Abweichungen der Aushärtung schon direkt nach der Beschichtung, durch das Fluoreszenzmesssystem, detektiert und somit Fehlproduktionen schon frühzeitig erkennt werden können. [... aus Zusammenfassung und Ausblick]

O demorado tratamento térmico, comum no preparo de fotocatalisadores e sua imobilização em substratos, foi contornado nesta tese, em que se investigaram duas estratégias de modificação de eletrodos de ouro com TiO2 P25. A primeira consiste em promover a formação de uma nanocamada pela simples exposição do metal por 1 min à suspensão aquosa de TiO2 (10 g L-1 em HCl 0,1 mol L-1); na segunda, deposita-se uma pequena alíquota (5 ou 8 µL) da suspensão diretamente no substrato (drop coating) para secá-lo em seguida por irradiação com lâmpada incandescente (60 W a 20 cm), obtendo-se bons resultados de uma a três camadas depositadas. Comprovou-se grande aumento da estabilidade da suspensão aquosa e duplicação da atividade fotocatalítica do nanofilme de TiO2 em decorrência da repulverização de P25 comercial em almofariz, melhoria inalcançável por sonicação da suspensão. O tamanho de partícula médio obtido por DLS para o TiO2 disperso em meio de HCl 0,1 mol L-1 atingiu 103±3 nm, enquanto que o filme depositado na superfície do ouro (observado por MEV e caracterizado por EDS) não ultrapassou 100 nm de espessura, sendo dominado por partículas de diâmetro de 20 (anatase) a 30 nm (rutilo), observadas por MET. A estabilidade da suspensão é susceptível ao ânion do ácido utilizado, sendo que resultados igualmente satisfatórios foram obtidos com HCl e HclO4 0,1 mol L-1, enquanto que para a mesma concentração de H2SO4 o TiO2 sofreu sedimentação rápida e o eletrodo preparado com a suspensão apresentou fotoatividade 10x menor. Filmes de espessuras bastante distintas (100 nm e 2 m) depositados a partir de suspensão 10 g L-1 por contato e drop coating com gota de 5,0 µL, respectivamente, foram comparados em relação à sua capacidade de transporte de elétrons e resposta eletroquímica ao Fe(CN)6 3 1,0 mmol L-1, sendo que a carga líquida formal de oxidação do EDTA 1,0 mmol L-1 é apenas 50 % maior para o filme 20x mais espesso, além de gerar distorções consideráveis nas ondas voltamétricas do sistema-sonda reversível em relação ao filme nanométrico e à superfície polida. Com eletrodos modificados pelo protocolo otimizado de drop coating (8,0 µL de TiO2 2 g L-1), testou-se o efeito da presença de diferentes eletrólitos de suporte (ácidos 0,1 mol L-1) em processos anódicos de fotooxidação em geral. A curva de decaimento da fotocorrente iph com o tempo pode ser descrita por uma equação de decaimento exponencial duplo iph = i0 + A1 exp(k1t) + A2 exp( k21t), permitindo distinguir as contribuições da fotocorrente de oxidação da água (i0) e de termos referentes a dois tipos de sítio superficiais, sendo um de cinética rápida e outro de cinética lenta. A seguinte ordem foi determinada para a fotocorrente total inicial (iph0 total) dos eletrólitos: HNO3 > HClO4 > HCl > H1SO4 > H3PO4 e as explicações propostas para tal se embasam na adsortividade dos ânions no TiO2 e na reatividade dos respectivos traps formados. O mesmo modelo de ajuste matemático foi utilizado para avaliar a fotoatividade do eletrodo modificado pela sua irradiação sucessiva e repetida em HNO3 0,1 mol L-1 (sem EDTA), sendo observada redução significativa principalmente nos parâmetros relativos aos sítios de reação e, assim, sugere-se um impedimento dos mesmos através, p. ex., da formação de peróxidos superficiais. Na presença também de EDTA, a carga líquida total despendida na sua fotooxidação se mantém relativamente constante nas sucessivas irradiações. Por fim, os experimentos de fotooxidação do EDTA sob varredura de potencial revelaram uma região de relação linear entre a fotocorrente e o potencial aplicado ao eletrodo modificado com TiO2 que se estende até a região de saturação de fotocorrente ser atingida, comportamento compatível com filmes nanoparticulados porosos não-dopados. A inclinação da região linear aumenta em função da [EDTA], como se os valores de condutância (di/dE) se elevassem dependendo da reação interfacial. Ajuste de modelo matemático hiperbólico correlacionando a (foto)resistência do filme em função da fotocorrente de saturação R = R0 + kIsph1, fornece resistência ôhmica do filme R0 de 5,0 kΩ e uma constante atrelada ao fotopotencial de 237 mA Ω. Já a curva monotônica de fotocorrente de saturação (Isph) com a [EDTA] apresenta comportamento linear até cerca de 0,7 mmol L-1, sugerindo-se que nessa região o controle por transporte de massa é a etapa limitante do processo global. Acima dessa concentração o coeficiente angular diminui gradualmente à medida que a reação de cinética de captura das lacunas passa a ser o determinante até um limite máximo (aparentemente 5,0 mmol L-1 de EDTA, nas condições do experimento) onde a disponibilidade de lacunas fotogeradas passa a governar. / The lengthy thermal treatment is a common step during the preparation and immobilization of photocatalysers on substrates, which by the way, was overcome in this thesis by the investigation of two strategies of modification of gold electrodes with P25 TiO2. The first one consists in promoting the formation of a nanolayer by the simple exposure of the metal surface to an aqueous suspension of TiO2 (10 g L-1 on 0.1 mol L-1 HCl) during 1 min; the second involves the deposition of a small drop (5 or 8 L) of the suspension on the gold substrate (drop coating) and its drying by irradiation with an incandescent lamp (60 W at 20 cm far), with worthy results also for two or three deposited layers. The stability of this aqueous suspension was appreciably improved by the repulverization of commercial P25 in a grinding mortar. As a consequence the photocatalytic activity conferred to the electrode by the formation of the TiO2 nanofilm doubled. Such improvements cannot be attained by bath sonication of the suspension. The average particle size determined by DLS for the TiO2 dispersed in 0.1 mol L-1 HCl was 103±3 nm, while the film deposited on the surface of gold consisted of particles of 20 nmn (anatase) and 30 nm (rutile) characterized by TEM and barely achieved a thickness of 100 nm (characterized by SEM and EDS). The stability of the modifying suspension is susceptible to the type of anion of the electrolyte. Good results were found with 0.1 mol L-1 HCl and HClO4, but not with 0.1 mol L-1 H2SO4. This last medium causes fast sedimentation of TiO2 and generates electrodes with one tenth of the photoactivity achieved with the other acids. The effect of film thickness on the photoactivity was evaluated for films with 100 nm and 2.0 µm prepared from a 10 g L-1 TiO2 suspension by the contact and drop coating (5 µL) strategies, respectively. The electron transport across both films and the electrochemical response for the 1.0 mmol L-1 Fe(CN) 63- probe was compared. The formal net charge for the 1.0 mmol L-1 EDTA oxidation was only 50 % higher for the 20x thicker film that also considerably distorts the voltammetric waves of the aforementioned reversible probe. The effect of different supporting electrolytes (0.1 mol L-1 acids) on the anodic photooxidation processes in general was tested with electrodes modified by an optimized drop coating protocol (8.0 µL of 2 µg L-1 TiO2). The curve describing the photocurrent decay in function of time might be ascribed to an equation of double exponential decay iph = i0 + A1 exp(k1t) + A2 exp (k2t), which allows the distinction of the contribution of water oxidation (i0) from terms of two types of surface sites: a kinetically fast site and a slow one. The total initial photocurrent (iph0 total) of the following electrolytes decays in the order: HNO3 > HClO4 > HCl > H2SO4 > H3PO4; explanations comprise the adsorbability of each respective anion on TiO2 and the reactivity of the corresponding traps formed. Similar curve fitting applied to the data of photoactivity of the gold electrode during successive irradiations of its surface in 0.1 mol L-1 HNO3 (absence of EDTA) revealed that sites reactivities underwent considerable reduction. It is suggested that during repetitive experiments the sites are impaired by the formation of surface peroxides. However, in the presence of 1.0 mmol L-1 of EDTA, the formal net charge of oxidation of the organic species remains almost unaltered. Ultimately, the experiments concerning the photooxidation of EDTA under linear potential scan revealed a region of linear relation between the photocurrent and the potential applied to the electrode modified with a TiO2 film (nanometric or micrometric), which holds until the saturation photocurrent is attained. This behavior is typical for porous non-doped nanoparticulate electrodes. The slope of the linear region increase somewhat with the EDTA concentration, as though the conductance values (di/dE) were raised depending on the interfacial reaction rate. The fitting of a hyperbolic model R = R0 + kIsph-1 for the correlation of the (photo)resistence (R) of the film with the photocurrent of saturation (Isph) allows the estimation of an ohmic resistance of 5.0 kΩ, and a photopotential related constant of 237 mA Ω. The curve of correlation between Isph and the [EDTA] is linear fit until 0.7 mmol L-1, suggesting that in this initial region the mass transport to the interface is the limiting step of the global process. Above that concentration, the slope of the curve is gradually reduced as the kinetic of capture of the holes becomes the determining step and from 5.0 mmol L-1 on an asymptotic Isph is reached (under the conditions of the experiments), where the holes photogeneration might start governing.

Made available in DSpace on 2014-08-20T13:44:41Z (GMT). No. of bitstreams: 1 dissertacao_joao_carlos_benatto_jr.pdf: 93588 bytes, checksum: 357cf23c63a8a8f690a9bf4dd7d3511a (MD5) Previous issue date: 2008-05-06 / The use of polymers in soybean seeds has been accomplished with the purpose of incorporating products like insecticides, fungicides, growing substances, minor fertilizers and so on, in order to improve the visual aspect of the seed, to promote smaller operator's intoxication risk and to provide a better seeds' acting and seedlings after sowing. The main objective of this work was to evaluate the recovered seeds' effects in soybeans seed quality lots of high and low germination of the cv. AG 7000. The seed's film coating was accomplished with two commercial marks of polymers, LABORSAN ® , and LANXESS ® , in doses of 2 and 3,5 ml for each kg with and without mixture of the fungicide Carbendazim + Thiram (firewalk ® ). The seeds' quality evalutions, were measured by the germination test, germination in sand and accelerated aging. The use of polymers in soybean seeds provides seeds with good appearance and coloration and can be applied to differentiate the seed from the commercial grain. The fungicide and the polymers do not affect the physiological quality of soybean seed. The results of the polymers and fungicide were superior in the test of accelerated aging, showing higher germination in relation to the check treatment. / O uso de polímeros em sementes de soja vem sendo realizado com a finalidade de incorporar produtos fitossanitários, melhorar o aspecto visual da semente, promover menor risco de intoxicação do operador e proporcionar um melhor desempenho de sementes e plântulas após a sua semeadura. O objetivo principal deste trabalho foi avaliar o efeito do recobrimento na qualidade de semente de soja de alta e baixa germinação da cv. AG 7000. O revestimento foi realizado com duas marcas comerciais de polímeros, LABORSAN ® , e LANXESS ® , nas doses de 2 e 3,5 mL para cada kg de semente com e sem mistura do fungicida Carbendazim + Thiram (firewalk ® ). As avaliações da qualidade das sementes foram realizadas por meio do teste de germinação, germinação em substrato de areia e envelhecimento acelerado. O uso de polímeros na semente de soja proporciona sementes com boa aparência e coloração, podendo ser aplicado para diferenciar a semente do grão comercial. O fungicida e o polímero não prejudicam a qualidade fisiológica da semente de soja. Os resultados do polímero e fungicida foram superiores no teste de envelhecimento acelerado, apresentando maior percentual de germinação em relação à testemunha.

Comme les propriétés physiques d'un matériau à l’échelle nanométrique sont largement dépendantes de la taille et de la forme des nanostructures, il est inutile de synthétiser de nouvelles compositions et morphologies. L’étude avancée de leur structure par les techniques de caractérisation usuelles (MET, MEB, DRX, Raman…) permettra de collecter toutes les informations nécessaires à la compréhension de leurs propriétés physiques (magnétiques, optiques, électriques). Dans ce manuscrit, nous décrirons plusieurs approches d’élaboration de nanostructures 0D, 1D et 2D multifonctionnelles afin de mieux connaître les paramètres qui contrôlent leur composition chimique et leur structure. De plus, ce travail de recherche a abouti à la synthèse de nouveaux matériaux à base d’oxyde et de carbure de fer. Des nanofibres magnétiques ayant des morphologies originales « Ruban » et « tube » ont été élaborées par la technique d’électrospinning en modifiant plusieurs paramètres expérimentaux : concentration de la solution, atmosphères de traitement thermique, température de recuit… De plus, des couches minces guidantes dopées par des nanostructures magnétiques ont été préparées par la technique dip-coating. Nous avons mené une étude complexe et détaillée sur les propriétés structurales de ces matériaux afin de définir les paramètres expérimentaux qui permettront d’obtenir des nano objets de bonne qualité. Dans un but ultime, nous souhaiterons explorer les possibilités d’application de ces matériaux qui présentent à la fois des caractéristiques électriques et magnétiques. / The physical properties of a nanomaterial strongly depend on the size and the shape of the nanostructure. As a consequence, it is interesting to elaborate new materials with different compositions and morphologies. The advanced study on the structure using common characterization techniques (TEM, MEB, XRD, Raman…) allows us to collect all the important information on their physical properties (magnetic, optical and electrical properties). In this thesis, we describe multiple ways to elaborate multifunctional nanostructures with 0D, 1D and 2D in order to study the parameters that control their chemical composition and structure. Besides, this research lead to the elaboration of new nanomaterials based on the oxide and the carbide forms of iron. Magnetic nanofibers with different morphologies (belts, tubes) were prepared using the electrospinning technique while controlling several experimental parameters : solution concentration, pyrolysis atmosphere, thermal treatment temperature… Moreover, thin layers doped with magnetic nanostructures were deposited on a pyrex substrate using the dip-coating technique. A full and detailed study on their structural properties was performed in order to reach the experimental parameters that allow us to obtain high quality products. Finally, we wish to explore the possible applications of these materials that present interesting electrical and magnetic characteristics.

Ces travaux de thèse ont eu deux objectifs: i) le développent de systèmes nanofluidique en utilisant une méthode non-lithographique, peu chère et facilement transposable à l'échelle industrielle ii) la compréhension des phénomènes nanofluidiques au travers des études expérimentales et de modélisation. Des couches minces mesoporeuses, en particulier des structures planaires avec des nanopiliers, ont été utilisé pour des études sur l'infiltration capillaire des liquides dans espaces confiné au niveau nanométrique. En plus des premiers tests pour des applications plus complexes comme des séparations et réactions nanoconfiné. Des structures mesoporeuses non-organisés ont aussi été étudiées pour déterminer la relation entre la nanostructure et la vitesse de remplissage capillaire. A été aussi démontré que pour des porosités avec des forts rétrécissements le remplissage capillaire se produit par l'intermédiaire d'une phase vapeur. Les échantillons ont été préparés par dip-coating. Une méthode de préparation basé sur une substitution de la plus grande parte de la solution à déposer par un fluide inerte a été développé. La méthode permet de réduire fortement le cout de procédé et, par conséquence, de faire des dépôts sur plus grande surface. Un effort dans la modélisation des phénomènes nanofluidiques a aussi été fait pendant cette thèse. Une méthode de simulation qui permet de décrire adéquatement les interactions hydrodynamiques dans un système nano a été utilisée pour simuler un flux électro-osmotique. La méthode, Stochastic Rotational Dynamics, a été valide par confrontation avec des résultats connus et l'influence des certains paramètres de simulation évaluée dans le détail. / This thesis had a dual purpose: i) the development of nanofluidic devices through not lithographic, cheap and scalable bottom-up approach ii) the understanding of nanofluidic phenomena both through experiments and simulations. Mesoporous thin films, in particular Pillared Planar Nanochannels (PPNs), were prepared and utilized to study the capillary infiltration of liquids in nanostructures and have been tested for future nanofluidic applications like separations and nanoconfined reactions. Non organized mesoporous films have also been studied to determine the relationship between nanostructure characteristics and infiltration speed. It has been also demonstrated that in the case of porosities with reduced bottle-necks capillary penetration is performed through a vapor mediated mechanism The samples were prepared by dip-coating. A novel method of preparation based on the substitution of a large part of the deposing solution in dip-coating with an inert fluid has been developed in order to strongly reduce the fabrication costs and allow the preparation of larger samples. Moreover advancement in control of the dip-coating technique in “acceleration-mode” to produce thickness gradients has been developed and some potential application linked to fluidics shown. Finally a part of the effort of this thesis has been placed in the modeling of the electro-osmotic phenomenon in nanostructures through a rather novel simulation method, Stochastic Rotational Dynamics, which takes into account the hydrodynamics and the other interactions inside a nanofluidic system. Validations of the method and further investigations in particular nanofluidic conditions have been performed.

In gas-solid fluidized beds, the generation of electrostatic charges due to continuous contacts between fluidizing particles, and the particles and the fluidization vessel wall, is unavoidable. Industrial operations, such as the production of polyethylene, are susceptible to significant operational challenges caused by electrostatics including reactor wall fouling, a problem known as “sheeting”. The formation of particle sheets can require shutdown periods for clean-up which results in significant economic losses. To gain a better understanding of the underlying mechanisms of electrostatic charging in gas-solid fluidized beds, in an attempt to eliminate or minimize this problem, a pilot-scale pressurized gas-solid fluidization system was designed and built, housing an online electrostatic charge measurement technique consisting of two Faraday cups. The system permits the study of the degree of particle wall fouling at pressures and temperatures up to 2600 kPa and 100°C, respectively, and gas velocities up to 1 m/s (covering a range including turbulent flow regime). The system also allowed, for the first time, the measurement of the fluidizing particles’ mass, net charge and size distribution in various regions of the bed, especially those related to the wall coating under the industrially relevant operating conditions of high pressures and gas velocities. Experimental trials were carried out using polyethylene resin received from commercial reactors to investigate the influence of pressure and gas velocity on the bed hydrodynamics and in turn, the degree of bed electrification. Mechanisms for particle charging, migration and adherence to the column wall were proposed. The size distribution of the gas bubbles shifted towards smaller bubbles as the operating pressure was raised. Thus, higher pressures lead to greater mixing within the bulk of the bed and resulted in a higher degree of particle wall fouling. Moreover, the extent of wall fouling increased linearly with the increase in gas velocity and as the bed transitioned to turbulent regime, due to the increase in particle-wall contacts. Bipolar charging was observed especially within the wall coating with smaller particles being negatively charged. Overall, particle-wall contacts generated negatively charged particles resulting in a net negative charge in the bed, whereas particle-particle contacts generated positively and negatively charged particles resulting in no net charge when entrainment was negligible. The formation of the wall layer and its extent was influenced by the gravitational and drag forces balancing the image force and Coulomb forces (created by the net charge of the bed and the metallic column wall as the attraction between oppositely charged particles).

Production of top quality castings for applications in energy, aerospace and medical industries by the addition of ceramic cores to investment casting presents many metallurgical and technological problems. Ceramic cores applied in investment casting are subjects to many requirements in terms of their inertness to the casted alloy and at the same time to their final removal from the casting cavity in such a way that does not damage the casting. Both of these assumptions can be achieved by applying a thin layer of inert oxide ceramic coating to the surface of a ceramic core, made out of a chemically removable – leachable oxide ceramic.

This diploma thesis deals with material printing using roll to roll material printer. Several kinds of printing inks were prepared and their parameters, like viscosity and homogeneity were optimized. Corona treated PET foil was used as the flexible substrate. Thin layers of function material were prepared by coating by using the smooth cylinder and slot die method. Layers homogeneity was characterized by optical density. Layer thickness was measured by profilometer.