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.

Made available in DSpace on 2014-06-11T19:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-18Bitstream added on 2014-06-13T21:02:05Z : No. of bitstreams: 1 sano_dmc_dr_bauru.pdf: 2390435 bytes, checksum: c70bb14dca9d8503f9a9ce373ebe90a2 (MD5) / Neste trabalho foi realizada a simulação numérica da fase líquida no processo de deposição de filmes finos pela técnica de molhamento (dip-coating), via sol-gel, utilizando como aplicação soluções precursoras de dióxido de estanho (Sn'IND. 2'). Dióxido de estanho é um semicondutor transparente de gap largo, amplamente utilizado em muitos tipos de dispositivos. Além da técnica convencional, o trabalho analisa uma nova proposta da técnica de deposição dip-coating onde a solução se encontra em uma temperatura diferente da ambiente. Para ambas as técnicas foram realizadas a modelagem matemática dos problemas e desenvolveu-se um método numérico apropriado baseado no método MAC (Marker and Cell). O problema foi resolvido em coordenadas cartesianas bidimensionais e as equações foram discretizadas pela técnica de diferenças finitas. Os resultados numéricos são visualizados por meio da distribuição de temperatura e vetores velocidade da solução precursora, que fornecem subsídios para investigação da influência dos vetores velocidade na obtenção de filmes com boas propriedades, em relação à uniformidade e homogeneidade. Verifica-se que estas características refletem diretamente na qualidade óptica dos filmes investigados, tornando-se parâmetros importantes para aplicações em dispositivos opto-eletrônicos. Através dos resultados numéricos verificou-se que nas regiões do fluido próximas ao substrato, os módulos dos vetores velocidade são maiores, há uma maior quantidade de material sendo depositado. Notou-se também, através da distribuição de velocidades em direção ao substrato que o filme tem uma melhor uniformidade na sua espessura quando os vetores velocidade possuem os valores de seus módulos mais próximos uns dos outros. Portanto, mudando os parâmetros iniciais de viscosidade, densidade, velocidade de imersão/emersão do substrato ou temperatura no fluido pode-se estudar o comportamento. / In this work, the numerical simulation of liquid phase in the thin film deposition, by the sol-gel-dip-coating technique, was carried out. The method was applied to tin dioxide (Sn'IND. 2') solutions. Tin dioxide is a transparent semiconductor of wide bandgap, extensively used in many types of devices. Besides the conventional procedure, this work analyses a new proposal for the deposition technique, where the solution is heated above room temperature. In both cases, the mathematical modeling was done and the appropriated numerical method was developed, based on MAC (Marker and Cell) approach. The problem was solved in two-dimensional Cartesian coordinates and the equations were discretized by the finite difference technique. The numerical results are visualized through temperature and vector velocity distributions in the precursos solution, yielding subsides to the investigation of the influence of vectors velocity in the deposition of good property films, concerning uniformity and homogeneity. It was verified that these characteristics point directly toward the optical quality of investigated films, becoming important parameters for application in optoelectronic devices. The numerical results allow verifying that in the fluid regions close to the substrate, where the velocity modulus is highter, there is a larger amount of material being deposited. It was also noticed, through the velocity distribution towards the substrate, that the film has a better thickness uniformity when the vectors velocity have modulus values closer to each other. Therefore, changing initial parameters such as viscosity, density, substrate dipping rate or fluid temperature, it is possible to evaluate the fluid behavior during the thin film deposition.

Cette étude se place dans le contexte de réalisation de nouveaux matériaux à bas coût pour l'optique non linéaire. Pour cela, nous avons développé une approche nanocomposite, basée sur la fabrication de films Laponite/ LiIO3. Ces films sont réalisés à l'aide d'une technologie issue du procédé sol-gel puis recuits pour cristalliser LiIO3, matériau optiquement non linéaire, et ils présentent de bonnes potentialités en raison d'une concentration en nanocristaux actifs importante. De plus, la possibilité d'orienter les nanocristaux pendant la cristallisation par l'application d'un champ électrique permet d'obtenir un matériau présentant des propriétés optiques non linéaires comparables à celles des matériaux usuels de ce domaine.<br /><br />Au cours de ce travail, nous avons tout d'abord affiné le modèle de structure des films composites en mettant en évidence l'absence d'intercalation du LiIO3 dans l'espace interplaquette. Par la suite, nous avons optimisé le processus de dépôt des films. En particulier, nous avons amélioré sa reproductibilité en déterminant les principaux paramètres intervenant durant le process : pH, viscosité, température de recuit, champ électrique d'orientation. Par ailleurs, nous avons montré que le vieillissement des films, une limitation importante de ce procédé, pouvait être ralenti par le dépôt d'un film protecteur. Nous sommes ainsi parvenus à définir un ensemble de critères permettant la réalisation de films nanocomposites aux propriétés optiques linéaires et non linéaires satisfaisantes.<br /><br />Dans une seconde partie, nous nous sommes attachés à caractériser et modéliser les propriétés optiques linéaires et non linéaires des films nanocomposites Laponite/LiIO3. Nous avons cherché à établir le lien entre ces propriétés et la structure des films, et nous avons observé l'influence de la distribution d'orientation des nanocristaux d'iodate de lithium au sein de la matrice de Laponite sur les propriétés optiques non linéaire et pour le guidage. Cette étude, au caractère plus fondamental, a permis de construire des modèles adaptés à ce type de matériaux composites permettant d'interpréter les résultats expérimentaux et de prévoir les indices de réfraction et les propriétés optiques non linéaires de ce type de matériau.

In this study, the wastewater from oxide chemical mechanical polishing (oxide-CMP) process of semiconductor wafer fabrication was treated by crossflow electro-ultrafiltration with self-prepared tubular inorganic membranes. First of all, a recipe of alumina (72 wt%), bentonite (8 wt%) and water (20 wt%) was determined for the extrusion of green tubes. The porous ceramic green tubes of 200 mm in length thus obtained were subjected to further curing, drying, and sintering processes. The inner and outer radii of the porous ceramic supports were 6.0 mm and 10.0 mm, respectively. Then, nanoscale TiO2 (i.e., the slip) was prepared by sol-gel method. On the tops of porous ceramic supports thin layers of nanoscale TiO2 were applied by the dip-coating method. To analyze the microstructures of tubular inorganic membranes and confirm the nanoscale TiO2 films, a scanning electron microscope equipped with energy-dispersive X-ray analyzer (SEM-EDS) and X-ray diffractometer (XRD) were employed. The self-prepared tubular inorganic composite membranes (TICMs) were futher characterized by permporometry and Kelvin equation to determine their pore size distributions and nominal pore sizes. In addition, through the employment of polyethylene glycol (PEG) of different molecular weights and total organic carbon analysis method, the molecular weight cut-off (MWCO) and tightness coefficient of each TICM was determined. It was found that the self-prepared TICMs were suitable for ultrafiltration applications. In this work, wastewater from the oxide-CMP process of semiconductor wafer fabrication was treated by crossflow electro-ultrafiltration with self- prepared TICMs. The permeate qualities were evaluated. Experimental results have shown that permeate of a higher filtration rate, a turbidity of below 1 NTU, 90% removal of total suspended solids, and a removal efficiency of greater than 80% for soluable silica could be obtained under the conditions of an electric filed strength of 30 V/cm and transmembrane pressure of 5 kgf/cm2. For permeate to meet the feed water requirements for the ultrapure water system, it has to be further treated to lower its silica content to ¡Ø 6 mg/L. Overall speaking, by incorporation of the tubular inorganic composite membranes prepared in this work into the novel electrofiltration treatment module for the treatment of oxide-CMP wastewater would yield permeate suitable for the purpose of reclamation.

Submitted by Mario BC (mario@bc.ufrpe.br) on 2017-08-03T12:52:24Z No. of bitstreams: 1 Pedro Lemos de Almeida Junior.pdf: 3276258 bytes, checksum: 9cfc77040db57e5dc73048d5ce92da67 (MD5) / Made available in DSpace on 2017-08-03T12:52:24Z (GMT). No. of bitstreams: 1 Pedro Lemos de Almeida Junior.pdf: 3276258 bytes, checksum: 9cfc77040db57e5dc73048d5ce92da67 (MD5) Previous issue date: 2014-03-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The development of multilayer self-assembled films using the Layer Layer (LbL) approach has showed a high efficiency on the fabrication o ultrathin films. The LbL technique have been successfully and increasingly employed on developing new arquitectures for immobilization of enzymes, catalysts, electron mediators and other chemicals on conventional solid electrode surfaces for the development of electrochemical sensors and biosensors. This work followed two main paths: it was proposed the development and application of a new miniaturized dip-coating equipment, named LbL System, for the preparation of multilayers thin films on solid electrodes, and also a new method for the modification of gold electrodes for the immobilization of ferricyanide ions into a silica network, with application for the determination of nitrite ions. The proposed LbL System is automatic and has an embedded microcontroller that simplifies its hardware and software, and also favors its miniaturization. The system makes it possible all the modification process of being carried out automatically without attendance during the operation, only requiring the definition of some parameters by the user. The development of the equipment was based on a new concept of dip-coating, where, the solution flows to a fixed electrode instead of dipping the electrode in the solution, as it happens at all the commercial equipments, making possible to work with microvolumes of reagents and solutions keeping a high reproducibility of the modification process. The proposed new method for immobilization of ferricyanide ions on gold electrodes was based on its affinity with a silica network modified with a spacer containing amine terminal groups, anchored on the surface via silanol groups of the opposite terminal bound to other silanol groups of a self-assembled monolayer previously deposited on the metal. The gold modified electrode presents the voltammetric characteristic reversible signal of the redox pair Fe((III)/Fe(II), showing the maintenance of the Fe(III)/Fe(II) in the molecular arquitecture mounted on the metal surface. The modified electrode presented electrocatalytic activity for the reduction of nitrite ions and was successfully applied on a flow injection analysis system for analyses of natural waters, presenting a linear response range of 1x10-6 to 4x10-5 mol L-1 (r = 0.9995), with a detection limit of 0,53x10-6 mol L-1. / A elaboração de filmes contendo multicamadas automontadas utilizando a técnica camada sobre camada (LbL, do inglês “Layer by Layer”) tem se mostrado um método eficaz para a fabricação de filmes ultrafinos. Filmes LbL vêm sendo crescentemente empregados com sucesso na elaboração de novas arquiteturas para imobilização de enzimas, catalisadores, mediadores de elétrons e outras espécies na superfície de eletrodos sólidos convencionais para elaboração de sensores e biossensores eletroquímicos. Neste trabalho foram propostas duas vertentes. Primeiramente se descreve a fabricação e aplicação de um equipamento microcontrolado, denominado Sistema LbL, para a obtenção de filmes finos multicamadas sobre eletrodos sólidos. Em seguida se propõe um novo método para a modificação de eletrodo de ouro pela imobilização de íons ferricianeto em rede de sílica, com aplicação para determinação de íons nitrito. O Sistema LbL desenvolvido é automatizado e traz consigo um microcontrolador, que simplifica significativamente seu hardware e software, além de possibilitar sua miniaturização. O Sistema permite que todo o processo de modificação da superfície de eletrodos sólidos seja realizado automaticamente e sem requerer assistência durante a operação, cabendo ao usuário apenas a definição prévia de determinados parâmetros. O desenvolvimento do equipamento fundamentou-se em uma nova concepção de sistema dip-coating, em que ao invés de introduzir o eletrodo nas soluções, como realizado nos equipamentos comerciais, leva-se as soluções até o eletrodo, tendo como resultado um método de modificação que utiliza microvolumes de reagentes e soluções, com elevada reprodutibilidade do processo de modificação. O novo método, desenvolvido para imobilização de íons ferricianeto em eletrodo de ouro, baseou-se na afinidade dos íons ferricianeto por uma rede de sílica modificada com um espaçador contendo grupamentos amina terminais ancorado no eletrodo via grupos silanóis do terminal oposto, sendo este previamente fixado no eletrodo por condensação com grupos silanóis de uma monocamada automontada na superfície do ouro. Após a modificação, o eletrodo de ouro passa a apresentar o sinal voltamétrico reversível característico do par redox Fe(III)/Fe(II), demonstrando que a atividade redox é mantida na arquitetura molecular montada sobre a superfície do metal. O eletrodo modificado apresentou atividade eletrocatalítica para a redução de íons nitrito e foi aplicado com sucesso num sistema de análise por injeção em fluxo para análises de águas naturais, apresentando resposta linear na faixa de 1x10-6 a 4x10-5 mol L-1 (r = 0,9995), com limite de detecção de 0,53x10-6 mol L-1.

Tato diplomová práce se zabývá výrobou ultratenkých keramických dutých vláken pomocí metody povlakování namáčením. Příprava keramických dutých vláken je v současnosti limitována rozměrem vnějšího a vnitřního průměru. Aplikace metody povlakování namáčením pro přípravu ultratenkých dutých je nový a technologicky náročný proces vyžadující volbu vhodné šablony a zároveň zvládnutí kontroly parametrů povlakování. Základními zvolenými materiály s vysokým aplikačním potenciálem jsou hydroxyapatit a oxid titaničitý. Samonosná dutá vlákna s tloušťkou stěny pod 1 m byla úspěšně připravena z obou materiálů. Dále byl také popsán proces povlakování namáčením obětovaných šablon. Tato metoda je unikátní, protože umožňuje produkci ultratenkých keramických dutých vláken s vnitřním průměrem pod 100 m a tloušťkou stěny pod 1 m.

This work deals with preparation of layers of ceramic materials – perovskites. The introductory part includes general characteristics concerning structure, properties and use of this materials. In details then there is described method of their preparation, namely Pechini´s syntheses, which are most widely used. Optimum molar ratio of components is discussed, in the sense of what compositions lead to creation of perovskite structures. Influence of this parameter on rheological properties of precursory gels is described in the end of the first part of work. In experimental section there are described preparations of gels, which are prepared via reaction between citric acid and ethylene glycol and gels, which are prepared by Pechini´s synthesis. Rheological properties of prepared gels (density, viscosity and surface tension) and besides determination of amount of nitrates in gels are characterized. Temperature dependence of viscosity of gels, that are prepared by reaction of citric acid and ethylene glycol are determined. In final part successful preparations of perovskite layers is shown on ceramic substrate. This layers are observed by means of light optical microscope and scanning electron microscope.

No description available.

Implementation of solar power by photovoltaic modules in cold climates, such as northern Sweden, implies several challenges. Ice and snow coverage not only leads to reduction in energy production due to shading, but it also puts equipment at risk from additional weight. The goal of this thesis was to formulate a passive ice shedding coating for photovoltaics that could handle the demands of both high optical transmittance and durability. In addition, the coating should be environmentally friendly and low cost. For that purpose, a state-of-the-art, superhydrophobic sol-gel silica-based coating was selected with the focus on optimizing its transparency, wettability, and durability. Different concentrations of binder, tetraethyl orthosilicate (TEOS), and catalyst (HCl) in the sol were explored, as well as post-treatment temperatures and sol aging, Hydrophobization was done by self-assembly of a silane and plasma polymerization of a siloxane. The coatings were characterized by UV-Vis spectroscopy, contact angle measurements, Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), tape peel strength, freeze-thaw cycling, ice adhesion force and a field test. Superhydrophobic, anti-reflective coatings with high transmittance (88.5±1.9%) were achieved, with some of them retaining their superhydrophobic properties after 15 freeze-thaw cycles between room temperature and -20°C. The main findings were that the amount of TEOS in the sol has the largest influence on transmittance and strength, with more TEOS leading to less transparent but stronger coatings, and that calcination of the coatings greatly improves their durability.

Polymer coatings are thin films of polymer deposited on different substrates for various applications. Such surface coatings can serve a functional purpose (adhesives, photographic films), protective purpose (anticorrosion), or decorative purpose (paint). Additionally, their composite coatings containing ceramic, or metal particles are often used to enhance durability, functionality, or aesthetics. Electrophoretic deposition (EPD) and dip coating are two promising methods for the fabrication of polymer and composite coatings due to the ease of fabrication, low cost, and high-volume production. EPD involves the electrophoresis of charged particles and their deposition on the electrode surface, which requires the colloidal particles to be charged in a stable suspension as a precursor solution for deposition. Many polymers cannot be deposited by EPD directly because of their charge neutrality and poor dispersion. Therefore, it is critical to develop efficient charging dispersants to modify electrically neutral polymers for their EPD. The approach was inspired by the strong solubilization power of bile acids in the human body. Two types of bile salts, cholic acid sodium salt and sodium chenodeoxycholate, and three types of biosurfactants, carbenoxolone sodium salt, glycyrrhizic acid, and 18β-glycyrrhetinic acid, which share similar structures with bile salts, were discovered for charging, dispersion, and EPD of different materials. The electrically neutral polymers (PTFE and PVDF), chemically inert materials (diamond, nanodiamond, graphene, carbon dots, carbon nanotubes and Zr-doped hydrotalcite (MHT)), and their composites can be well dispersed in suspension and deposited using these bio-surfactants as dispersants. It was found that the unique chemical structures of these biomolecules play vital roles in the surface modification and EPD of different materials. Moreover, the deposited polymer (PVDF, PTFE) and composite (PTFE-MHT) coatings can provide outstanding corrosion protection for stainless steel. The biomimetic and versatile strategy opens a way for the deposition of other electrically neutral materials through EPD. These findings also provide a promising strategy for selecting new dispersants for EPD. The deposition of high molecular weight (MW) polymers such as poly(ethyl methacrylate) (PEMA) at high concentrations in non-toxic solvents continues to be a challenge for dip coating. In this work, we firstly proposed using water-isopropanol as a co-solvent to dissolve high MW PEMA at high concentrations. It was found that water molecules can solvate carbonyl groups of PEMA and facilitate their dissolution. This method avoided the usage of toxic solvents and a long-time heating procedure for their removal. Moreover, it allows the fabrication of high-quality PEMA and composite coatings containing different flame retardant materials (FRMs), including double hydroxide LiAl2(OH)7.2H2O (LiAlDH), huntite, halloysite and hydrotalcite, through the dip coating method. A novel solid state synthesis method was proposed to fabricate LiAlDH, which is promising for the fabrication of other advanced DHs. Such composite coatings combined advanced properties of PEMA and functional properties of FRMs, such as corrosion inhibition and FR properties. / Thesis / Doctor of Engineering (DEng) / Polymer and composite coatings have been utilized for a wide range of applications due to their barrier properties, scratch and abrasion resistance, chemical resistance, and biocompatibility. Various techniques have been developed to fabricate polymer and composite coatings, such as electrophoretic deposition (EPD) and the dip coating method. However, limitations remain. EPD unitizes an electrical field to drive charged particles in a suspension toward conductive substrates to achieve film deposition. This process requires a stable suspension with charged particles, therefore, the electroneutral polymers present difficulties in their EPD. In addition, dissolving high molecular weight polymers at high concentrations in a non-toxic solvent is currently challenging, which is vital to utilize dip coating technique. The objective of this work was to develop advanced charging dispersants for EPD of electroneutral polymers and non-toxic solvents for dip coating of high molecular weight polymers. New biomimetic and versatile approaches have been developed for EPD of different electrically neutral polymers, chemically inert materials, and their composite coatings. A non-toxic co-solvent was proposed to dissolve high molecular weight polymer at high concentration for dip coating of the polymer and its composite coatings containing flame retardant materials. The results presented in this work showed the formation of high-quality films with multifunctionality and paved new strategies for further developments.