Дисертації з теми "Silicate composite materials"

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A zircônia tetragonal estabilizada por ítria (Y-TZP) têm sido utilizada na área odontológica para próteses livres de metais devido à estética associada ao alto desempenho mecânico. Porém, a presença de ambiente úmido pode causar a transformação acelerada da fase tetragonal para monoclínica e consequente falha catastrófica deste material, processo este conhecido como degradação a baixa temperatura ou envelhecimento. A cinética desta transformação é função da composição química da cerâmica e sua microestrutura. Tendo em vista que métodos químicos permitem a síntese de pós cerâmicos à base de zircônia de dimensões nanométricas, cuja microestrutura da cerâmica sinterizada é constituída por grãos submicrométricos quimicamente homogêneos, e que a presença de alumina é indicada para evitar a degradação de fases da zircônia, o objetivo deste estudo foi verificar a degradação a baixa temperatura e ambiente úmido de cerâmicas de zircônia estabilizada com 3 mol% de ítria (Y-TZP) e do compósito Y-TZP/Al2O3, proveniente de pós sintetizados pela rota de coprecipitação. A concentração de alumina na Y-TZP foi estudada na faixa de 0,05 a 20% em massa. A eficiência do processo desenvolvido foi verificada pela avaliação das características físicas dos pós obtidos (granulometria, área de superfície específica, estado de aglomeração e estrutura cristalina). As amostras cerâmicas foram prensadas, sinterizadas e avaliadas quanto à densidade aparente e microestrutura. Após a caracterização inicial das cerâmicas a degradação das amostras foi estudada in vitro em reator hidrotérmico pressurizado a 150°C. As amostras (n=4) foram submetidas à análise de difração de raios X de acordo com o tempo de envelhecimento, acompanhando a curva cinética de transformação de fase. A porcentagem de cada fase cristalina foi determinada pelo Método de Rietveld. A relação entre o tempo de envelhecimento e a concentração de fase monoclínica foi determinada pela equação de Avrami modificada por Kolmogorow (Johnson-Mehl- Avrami-Kolmogorow JMAK). Após envelhecimento a 150°C por 70 horas, todas as amostras contendo alumina apresentaram menor concentração de fase monoclínica, comparativamente à cerâmica Y-TZP, que apresentou 66,5% dessa fase. Menores porcentagens de fase monoclínica após o envelhecimento hidrotérmico foram obtidas com a adição de 10 e 20% em massa de alumina na matriz de zircônia, sendo esses valores 59,1 e 52,9%, respectivamente. Deve-se considerar, no entanto, que a diminuição da degradação total é consequência da menor porcentagem de zircônia na matriz em função da adição de alumina. Neste contexto, o efeito benéfico da adição de alumina ocorre apenas no início do envelhecimento.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Nenhuma
Materiais mesoporosos ordenados tipo SBA-16 possuem uma rede de canais e poros de tamanho bem definido na escala nanométrica, com estrutura cúbica, elevada área superficial (400 1000 m2.g-1) e tamanho de poros usualmente em torno de 2 a 30 nm. Essa estrutura de poros torna esses materiais apropriados para incorporar e liberar uma grande variedade de moléculas na sua matriz. Dentre os diversos tipos de materiais SBA, o SBA-16 é considerado uma mesoestrutura muito interessante devido ao fato de possuir um ordenamento de mesoporos cúbico tridimensional correspondente ao grupo especial Im3m, podendo ser um material promissor para várias aplicações. Os materiais mesoporosos podem sofrer diversas modificações na sua superfície, devido à presença dos grupos silanóis, podendo produzir um material com uma funcionalidade direcionada. Neste trabalho, estudou-se a síntese e caracterização do material SBA-16 puro e após o processo de funcionalização para avaliar sua aplicação como sistema de liberação controlada de um fármaco modelo. O processo de modificação da superfície foi realizado pelo método pós-síntese, ou seja, após o obter o material SBA-16, esse passou por um segundo processo para se obter as amostras funcionalizadas. A caracterização do SBA-16 puro e funcionalizado foi feita por análise elementar (CHN), Espectroscopia na Região do Infravermelho com Transformada de Fourier (FTIR), Análise Termogravimétrica (TG), Adsorção de Nitrogênio, Microscopia Eletrônica de Varredura (MEV), Microscopia Eletrônica de Transmissão (MET), Espalhamento de Raios X a Baixos Ângulos (SAXS), e Ressonância Magnética Nuclear (RMN). Por meio da técnica de espectroscopia de absorção na região do infravermelho, foi possível observar, a partir dos espectros das amostras funcionalizadas, bandas características das vibrações da rede de sílica, bem como bandas referentes às vibrações dos grupos alquilas ancorados na estrutura da sílica. A presença do fármaco atenolol no material mesoporoso e nas amostras funcionalizadas também pode ser confirmada por meio das medidas de FTIR. A estabilidade térmica e as degradações que ocorrem nos componentes puros, bem como nas amostras modificadas na superfície, foram investigadas e estabelecidas pela análise termogravimétrica. Por meio da TG foi possível quantificar a presença dos grupos orgânicos ancorados nesse material. A presença dos grupos orgânicos conduziu a alterações na estrutura do material final, com a diminuição da área superficial e volume de poros. Porém, a distribuição de poros se mostrou semelhante em todas as amostras. Os resultados de MEV, MET e SAXS do SBA-16 e das amostras funcionalizadas revelaram uma estrutura bem ordenada de mesoporos, característica intrínseca desses materiais. Por meio das medidas de ressonância magnética nuclear de 29Si e 13C de estado sólido (RMN-MAS) nas amostras funcionalizadas, foi possível caracterizar e avaliar a forma de ligação desses grupos orgânicos na matriz de sílica. Através do ensaio de liberação, foi possível avaliar a quantidade de atenolol incorporado e verificar o comportamento da liberação desse nas amostras sintetizadas. Com os resultados de citotoxicidade foi possível determinar a viabilidade celular, obtendo-se resultados satisfatórios para uma futura aplicação clínica desse material.
Type ordered mesoporous materials SBA-16 have a network of channels and well defined pore size in nanometer scale. Cubic structure has a high surface area (400 - 1000m2.g-1) and pore size is usually around 20 to 30 nm. This porous structure makes these materials appropriate to incorporate and release a large variety of molecules in the matrix. Among these SBA-type silica materials, SBA-16 is considered a very interesting mesostructure due to the its 3D cubic arrangement of mesopores corresponding to the Im3m space group, a promising material for a large range of applications. The mesoporous materials may undergo several changes in its surface due to the presence of silanol groups, which can produce a material with a targeted feature. The materials were characterized by elemental analysis (CHN), Fourier Transform Infrared Spectroscopy (FTIR), Nitrogen Adsorption, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Small Angle X Ray Scattering (SAXS), Nuclear Magnetic Resonance (RMN), and Thermal Analysis. Through the FTIR analysis technique, it was possible to observe characteristic bands of the silica vibrations, as well as vibrations bands due the presence of alkyl groups anchored into the silica structure. The presence of the atenolol in the mesoporous material and functionalised samples was also confirmed by FTIR. The thermal stability and the degradation of the surface modified samples were determined by thermogravimetry. The incorporation of the organic groups into the mesoporous silica led to a significant change in the structural properties of the system, with the decrease of the specific surface area and pore volume, but the pore size distribuition was similar in all samples. The results obtained by SEM, TEM and SAXS for the samples reveal a well-defined cubic arrangement of uniform mesoporous structure, intrinsic characteristic of these materials. By measuring nuclear magnetic resonance of 29Si and 13C solid state (MAS-NMR) in the functionalized samples, it was possible to characterize and measure the extent of binding of organic groups in the silica matrix. Through the release assay was possible to evaluate the amount of embedded atenolol and verify the behavior of the drug release from the synthesized samples. Considering the results of cytotoxicity, it was possible to determine cell viability by obtaining satisfactory results for future clinical application of this material.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003.
Includes bibliographical references.
Addition cure (X1-2672) and condensation cure (4-3136) silicone resins have been studied for their mechanical property change with temperature. Properties include maximum flexural stress, flexural modulus and fracture toughness K[sub]IC. Temperature effect on mechanical properties of addition cure resin is substantial and also depends on the crosslinkers used. Generally the maximum stress and flexural modulus decrease with temperature, and the dependence upon crosslinkers in addition cure resin is obvious. Fracture toughness data of addition cure silicone resins have a peaking behavior with the peak appearing [approximately] 58-101C̊ (depending on the crosslinker) below their glass transition temperatures. This can be explained by the competing effect between network mobility and rigidity of the silicone polymer. Rate effect on fracture toughness of silylphenylene crosslinked 2672 has also been studied. It is concluded that the temperature effect on such a system is more dominant compared to the rate effect. The condensation resins also experience decrease in modulus and strength but the toughness changes little with temperature. This is due to its tight network structure. Silylphenylene crosslinked addition cure resin (2672B) and the toughened condensation cure resin (3136T) were used to make silicone fiberglass laminates. They have been successfully processed with a vacuum bagging technique. Silicone resin composites are proved to be thermally stable, moisture resistant and fire resistant. However, they have weak strength and modulus. Their temperature dependence of mechanical properties is also big and results in poor property retention at high temperatures. 2672B was used to produce hybrid composites with an organic resin-vinyl ester. The processes of curing the hybrid composites in both sequential cure and co-cure methods prove to be successful. The hybrid composites are stronger and their property retention at elevated temperatures is improved compared to silicone resin composites. They also have improved moisture resistance, thermal stability and fire resistance over vinyl ester composites. The co-cured V/B 8/4 structure has excellent strength and rigidity and also extraordinary property retention at high temperatures, which can be explained by the chemical reaction at the silicone resin and vinyl ester resin interface. The hybrid composites prove to be successful in having balanced mechanical and environmental properties.
by Yuhong Wu.
Ph.D.

Thesis (M.Sc.)--City University of Hong Kong, 2005.
At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.

Thesis (M.Sc.)--City University of Hong Kong, 2005.
At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 1, 2006) Includes bibliographical references.

This thesis outlines the work done on in-situ synthesis of Al2O3-ZrO2-SiCw ceramic composites and their property evaluation. The introductory chapter deals with the literature survey on ceramic matrix composites, properties desirable for structural applications and toughening mechanisms associated with these composites. The role of whisker toughening in ceramic matrix composites, the growth mechanisms involved in whisker growth and the conditions that favour or hamper the whisker growth are also discussed. The advantages and disadvantages of in-situ synthesis of composites as compared to physical mixing are also dealt with. The objective and scope of the work undertaken are outlined at the end. The second chapter describes the experimental techniques associated with carbothermal synthesis and characterisation of reaction products as well as properties of hot pressed bulk composites. The equipments used for this work are described here. The third chapter focuses on the results obtained by the carbothermal reduction of mixtures of kaolin, sillimanite and zircon taken in various proportions. The formation of the product phases with respect to variations in temperature, variations in composition and effect of catalyst is analysed with the help of XRD while their morphology is analysed using SEM. The conditions favouring the formation of tetragonal zirconia without the addition of stabilizers is also enumerated here. The fourth chapter deals with the compaction of these composite powders and the evaluation of some physical, thermal and mechanical properties. Density and porosity, coefficient of thermal expansion, modulus of rupture and fracture toughness of the composite specimens are evaluated and compared with binary and ternary composites made by other methods. Finally the thesis concludes by summarizing the work done and briefly projecting the areas for future work.

Thesis (M.Sc.)--City University of Hong Kong, 2005.
At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Materiais mesoporosos ordenados tipo SBA-15 possuem uma rede de canais e poros de tamanho bem definido na escala nanométrica. Essa arquitetura particular de poros torna esses materiais viáveis para encapsular uma variedade de compostos na matriz da sílica, resultando em um material promissor para uma gama de aplicações. Esses materiais, quando contêm óxidos de metais de transição, especialmente nanopartículas de óxido de ferro magnéticas, podem ser usados para algumas aplicações in vivo, tais como no aumento do contraste em imagens por ressonância magnética nuclear, reparo de tecidos, imunoensaio, hypertermia, e liberação de fármacos. Nesse trabalho, nanopartículas magnéticas encapsuladas em sílica mesoporosa foram preparados em duas etapas. Primeiro a magnetita foi sintetizada pelo método de oxidação-precipitação a partir de uma solução de sulfato de ferro, hidróxido de potássio e nitrato de potássio. Em seguida, as nanopartículas magnéticas foram revestidas com sílica mesoporosa pelo uso de um surfactante não-iônico copolímero em blocos como agente direcionador da estrutura. A caracterização dos materiais foi feita por difração de raios X, adsorção de gases, infravermelho, espectroscopia Mössbauer, espectrometria de energia dispersiva (EDS), microscopia eletrônica de varredura (MEV), microscopia eletrônica de transmissão (TEM), espectroscopia de fotoelétrons excitados por raios X (XPS) e medidas magnéticas. Os resultados revelaram uma estrutura bem ordenada de mesoporos do nanocompósito, sugerindo que a mesma pode ser descrita como mesoporos hexagonais separados por uma parede de sílica contínua, formando uma camada de revestimento sobre as nanopartículas magnéticas. Dos dados de difração de raios X, foi obtido o tamanho médio das partículas de magnetita, que foi de 38 nm. A espectroscpia Mössbauer mostrou que a magnetita é preservada na rota de síntese. Os dados de XPS aliados aos de TEM mostraram que a rede de sílica recobre as partículas de magnetita, formando um nanocompósito com tamanho médio de grãos de 138 nm. Por fim, foi feito o estudo da influência dessas partículas magnéticas na cinética de liberação de três fármacos-modelo: cisplatina, carboplatina e atenolol sob condições in vitro. A liberação foi estudada na ausência e na presença de um campo magnético externo, utilizando para tanto um magneto NdFeB de 0,25 T. A análise foi feita por estudos de mecanismos cinéticos e de modelos de difusão, revelando que o campo externo influencia pouco no processo de liberação dos fármacos. Ao considerar que as nanopartículas estão presas na estrutura, esse resultado é coerente. Então, foi feito um teste para verificar a influência de um campo alternado no perfil de liberação, que mostrou um resultado mais significativo para a liberação de cisplatina. Para explicar esse fato, foi proposto então um modelo de interação entre a mesma e o nanocompósito.
Ordered mesoporous materials like SBA-15 posses a network of channels and pores of well-defined size in the nanoscale range. This particular pore architecture makes them suitable for hosting a broad variety of compounds into the silica matrix, resulting in very promising material for a broad range of applications, including magnetic carriers for drug delivery. In this work, magnetic nanocomposites embedded into mesoporous silica were prepared in two steps. Firstly, magnetite was synthesized by oxidation-precipitation method from a solution of iron sulfate, potassium nitrate and potassium hydroxide. After this, the magnetic nanoparticles were coated with mesoporous silica by using nonionic block copolymer surfactants as structure-directing agents. Characterization of the materials was carried out by using X-ray diffraction (XRD), 57Fe Mössbauer spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), N2 adsorption, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), XRay Photoeletron Spectroscopy (XPS) and magnetic measures. Our results revealed a wellordered mesopore structure of the nanocomposite, suggesting that the samples structure can be described as a honeycomb of hexagonal mesopores separated by continuous silica walls and the coating layer is distributed over the magnetic nanoparticles. The average size of magnetite particles obtained by XRD data was about 38 nm. Mössbauer spectroscopy showed that magnetite is preserved in the applied synthesis route. Both XPS data and TEM had shown that the silica recovers magnetite particles, forming a composite with particle sizeof 138 nm. Finally, the influence of these magnetic particles in the release kinetic was studied using drugs like cisplatin, carboplatin and atenolol; this study was made under in vitro conditions. The release was studied in absence and presence of a external magnetic field, using a NdFeB permanent magnet of 0,25 T. The kinetic mechanisms and diffusion models were investigated by the external field, and the results had showed a small influence of this parameter on the process of drug release. Considering that nanoparticles are coated by mesoporous silica, this result is expected. Then, a test was made to verify the influence of an oscillating field in the release profile and the results showed a more significant delivery for cisplatin. To explain this fact, an interaction model between this drug and the nanocomposite was proposed.

Thesis (Ph.D.)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Dr. Haskell W. Beckham; Committee Member: Dr. Anselm Griffin; Committee Member: Dr. Johannes Leisen; Committee Member: Dr. Sankar Nair; Committee Member: Dr. Uwe Bunz.

High-voltage (HV) outdoor composite insulators used in transmission lines are made of two polymers, comprising the core and housing, bonded together with metallic end-connections. The interface between these polymers is parallel to the electric field, which makes the insulators more prone to interfacial problems at these common points [1]. If interfacial ageing occurs, degradation and catastrophic breakdown can result [2]. Therefore, the design reliability of outdoor composite insulators depends on the high-strength bond between the core and the housing [3],[4]. Research findings by Kutil and Froshlic [5] indicate that delaminated areas, cavities and/or micro cracks in the medium are enough to initiate streamer discharges along the interface that are capable of degrading both insulating materials. The heat, UV radiation, and high-energy electrons produced from such discharge activity resulted in the growth of carbon paths along the interface, known as ‘tracking’, ultimately causing failure [6]. This investigation focuses on the development of tracking between silicone rubber and epoxy resin, with a view to replicating the tracking phenomena seen within composite insulators in service. A fine wire is placed between the dielectrics materials to enhance the local electric field magnitude and initiate discharge processes. The resulting partial discharge (PD) activity has been monitored. This Information has been used to understand the inception and propagation of the interfacial tracking. A strong relationship was found between maximum PD magnitude and track length. PD patterns and unique detailed images of the interfacial tracking development, allowed identification of the growth characteristics of interfacial channels and phases of tracking growth. Furthermore, a correlation in the mechanisms of interfacial degradation was found between the lab-fabricated samples and commercial composite rods. Finally, a growth model of interfacial ageing has been developed with the information from FEA models, PD patterns and the detailed images of tracking growth. The physical structure and chemical analysis of interfacial tracking is also disclosed to provide an insight into interfacial ageing mechanisms that occur in the composite insulators under electrical stress.

Este trabalho teve como objetivo preparar e caracterizar um compósito de colágeno com silicato e hidroxiapatita a ser possivelmente utilizado para capeamento pulpar direto e em pulpotomia como material endodôntico em prevenção ao tratamento radical de canais radiculares que em virtude de suas anatomias dificultam a utilização de biomateriais no interior dos mesmos. Embora materiais para este fim estejam disponíveis no mercado, na maioria dos casos não são isentos de agressão na zona do reparo. O colágeno utilizado foi do tipo I na forma aniônica que foi misturado com silicato (cimento Portland branco) e hidroxiapatita em proporções variadas. Os materiais obtidos foram caracterizados por técnicas de calorimetria exploratória diferencial (DSC), termogravimetria (TG), microscopia eletrônica de varredura (MEV), espectrometria de dispersão de energia de Raios-X (EDX) e espectroscopia na região do infravermelho (FTIR). A presença de colágeno no compósito foi demonstrada por transições térmicas típicas daquelas encontradas para o colágeno do tipo I ('APROXIMADAMENTE' 48 graus Celsius), independentemente da proporção utilizada, e também por MEV, onde as fibras colagênicas também puderam ser observadas interligando as partículas de silicato. Em função das quantidades de colágeno utilizadas, a composição química dos compósitos foi praticamente aquela descrita para o silicato inicial utilizado. Estes resultados mostraram que a estrutura da matriz colagênica nos compósitos estudados não foi alterada, uma característica importante para a utilização dos materiais propostos na endodontia objetivando uma reparação dos tecidos envolvidos de uma forma “mais natural”
In this work was prepared and characterized collagen composites with silicate and hydroxyapatite for pulp capping; post pulpotomy usage, as endodontic material. Even though materials for this purpose are available, in most case they suffer degradation in the repair zone when. Was used type I collagen in the form anionic mixed with silicate (white Portland cement) and hydroxyapatite in various proportions. The materials were characterized by standard differential scanning calorimetry (DSC), thermogravimetry (TG), scanning electronic microscopy (SEM) and infrared spectroscopy (FTIR), energy dispersion X-Ray (EDX). The presence of the collagen in the composite was checked via the thermal transitions typical for collagen type I ('APPROXIMATE' 48 Celsius degrees), independently of the proportion used and also via MEV, in which the collagenic fibers could also be seen interconnecting the silicate particles. For the amounts of collagen used, we find the chemical composition of the composites is essentially the same as that of the silicate we started with. This results showed that the structure of the collagenic matrix in the composite studied is not altered – an important feature for the use of the proposed materials in endodontic applications aiming at repairing the relevant tissues in a “more natural way”

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2007.
The continuous development of new materials and the improvement of existing ones ensure a balance between technological growth and environmental sustainability. With the above trade-offs, the quality of life for humankind is continually being improved. Polymeric materials are some of our most valued commodities in our everyday lives. They continue to be developed and improved in a variety of ways; one of which is to improve their properties by preparing nanocomposites. Polymer-based nanocomposites (PNCs) is a way of getting novel properties and enhancing existing one in polymer matrices, by incorporating additives on a nano-scale. The most significant advantage of PNCs is the potential to design and tailor properties for a specific application, since the control of the structure can be done at the molecular level. Therefore, a fundamental understanding of the relationships between the structure and the properties of PNCs is of utmost importance. Amongst the most studied and researched PNC materials, polymer-layered silicate nanocomposites (PLSNs) have recently enjoyed attention from academia and industry. In the current study structure-property relationships of PLSNs were investigated. Polystyrene (PS) was chosen as the base polymer due to its wide use in many articles such as in packaging. It was also a material of choice based on its poor mechanical properties in its natural state (unfilled), so as to contribute in its property improvement. Montmorillonite (MMT) was a layered silicate (clay) of choice, as much research has been done on it, and it is available worldwide, as a main component in Bentonite (a natural material). Clays are composed of sheet-like, layered particles, which, when in a suitable environment, can delaminate into single, nano-sized sheets. The sheets are held together by van der Waals forces and between the sheets are exchangeable cations. The clays are hydrophilic in nature and cannot readily delaminate in a hydrophobic polymer matrix due to the differences in surface energies. A MMT surface was functionalized to be hydrophobic by conducting an ion exchange reaction with alkyl ammonium surface active agents (surfactants). Polymerizable surfactants (surfmers) were used to enhance the interfacial interaction between the PS matrix and MMT silicate layers. The organically modified clays (organoclays) were used in synthesizing polystyrene-layered silicate nanocomposites (PS-LSN) by an in-situ intercalative polymerization method. The polymerization of the nanocomposites was conducted in bulk. The morphologies of the nanocomposites were characterized using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (Ope). The study was further expanded to the investigation of the effects of the nanocomposite structure, type of organic modifier, and amount of clay loading on the properties of the materials. The properties were studied by dynamic mechanical analysis (DMA), thermomechanical analysis (TMA) and dielectric analysis (DEA). The properties were dependent on the interfacial processes between the clay layers and the polymer matrix. The changes in properties compared to the PS homopolymer showed time and temperature dependent effects, as determined by DEA. Even though the dynamics of the interfacial interactions are still not fully understood, the nanocomposites showed improvements in properties compared to the homopolymers.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1985.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Includes bibliographical references.
by Kyu-Ha Chung.
Ph.D.

L'échantillonnage passif intégratif est de plus en plus reconnu comme une alternative à l'échantillonnage ponctuel pour la mesure des concentrations de micropolluants organiques dans les milieux aquatiques. Cette technique combine l'étape d'échantillonnage et de préconcentration in situ pour délivrer une concentration intégrée sur la durée d'exposition de l'échantillonneur passif (EP). Une des limitations principales de l'échantillonnage passif est la sélectivité imposée par la phase réceptrice pour une classe de contaminants restreinte (hydrophobes ou polaires). Ainsi, il est à l'heure actuelle nécessaire d'employer plusieurs EP pour mesurer des concentrations en pesticides caractérisés par une large gamme de polarité. L'objectif principal de cette thèse s'inscrit dans une démarche de développement de phases réceptrices pour l'échantillonnage passif de pesticides dans les milieux aquatiques. Afin de répondre à ce défi, nous avons sélectionné et formulé des matériaux pour la sorption de 28 pesticides aux propriétés physico-chimiques variées par le biais de tests en laboratoire. Nous avons d'une part sélectionné un élastomère de silicone de la marque Goodfellow® parmi 7 autres élastomères de silicone à partir de tests en laboratoire sur des critères de sorption. Nous avons démontré que les élastomères de silicone ont une forte affinité pour les pesticides plutôt hydrophobes, tout en accumulant également des pesticides polaires. Des propriétés de sorption différentes ont été identifiées selon leur formulation et un mécanisme d'adsorption est suspecté pour certains pesticides. D'autre part, nous avons formulé et testé plusieurs matériaux composites innovants dont le plus performant, renommé PACSiR, combine les propriétés de sorption d'un élastomère de silicone et d'un copolymère poreux (Oasis ® HLB). Nous avons mis en évidence que le PACSiR a des propriétés mécaniques adaptées pour une exposition directe dans le milieu aquatique et permet de capter une gamme de pesticides élargie vers les pesticides plus polaires par rapport à un élastomère de silicone. Ces deux matériaux ont été calibrés en laboratoire en tant qu'EP (TS à base de silicone et TSP à base de PACSiR), sous forme de tiges de petite dimension, afin de déterminer les constantes cinétiques d'accumulation et d'étudier l'impact de la vitesse de courant. Enfin, nous avons appliqué les TS et TSP dans des eaux de surface et de subsurface afin d'en évaluer et comparer les performances dans des situations contrastées d'exposition. La gamme d'utilisation de chaque EP en termes de polarité des pesticides a pu être définie (TS : 3 < log Kow < 5,5 et TSP : 2 < log Kow < 5,5.). Les concentrations en pesticides intégrées sur la durée d'exposition sont équivalentes à un échantillonnage d'eau moyenné au temps et les incertitudes sont du même ordre de grandeur sur les concentrations calculées. Ces EP ont permis de détecter des insecticides organophosphorés faiblement quantifiés par d'autres techniques de prélèvement d'eau. Nous avons démontré leur capacité à intégrer des pics de contamination fugaces en pesticides dans des contextes agricoles variés
Time integrative passive sampling is more and more accepted as an alternative to grab sampling for measurement of organic micropollutants concentrations in aquatic environment. This technique offers the advantage to provide a concentration integrated over the deployment period of the passive sampler and to reduce limit of quantification by combining sampling and in situ pre-concentration steps. The main limitation of passive sampling is the selectivity of the receiving phase for a restricted class of contaminants (hydrophobic or hydrophilic). In this way, we need to deploy several passive samplers for sampling of pesticides covering a wide range of polarities. The aim of this thesis was to develop a receiving phase for passive sampling of pesticides in a single step in aquatic environment.We selected and developed materials for sorption of 28 pesticides with varied physicochemical properties by laboratory tests. The two selected and studied materials were a silicone rubber and a porous copolymer (Oasis ® HLB). Indeed, we shown that silicone rubber have strong affinity for hydrophobic pesticides but they also accumulate polar pesticides. We identified different sorption properties of silicone rubbers owing to their formulation and a possible adsorption mechanism for some pesticides. The composite material developed had mechanical properties adapted for a direct exposition in the aquatic environment and accumulates a range of pesticides expanded for more polar pesticides. These two materials were then shaped as rods for a simple in situ deployment and recovery of pesticides in laboratory. They have been calibrated as passive samplers by studying the impact of flow velocity on uptake kinetic parameters. In situ applications of passive samplers in surface and subsurface waters made it possible to calculate time integrated concentrations of pesticides over a duration exposure of one week. Moreover, we detected organosphorous insecticides underquantified by other techniques of water sampling. They also showed a capacity to integrate short peak contamination of pesticides in various agricultural contexts

In this work nanomaterials based on silica were synthesized aiming their applications in therapy and diagnostic imaging. The study was divided into two parts, the first relating to the synthesis and characterization of modified with folic acid. The second part involves the synthesis and characterization of modified nanoparticles with nitric oxide-releasing complexes. Fluorescent nanoparticles were synthesized from the incorporation of fluorescent dyes in micellar medium containing tetraethylorthosilicate as silica precursor. The materials were functionalized with folic acid and characterized by TEM, nitrogen adsorption isotherms, UV-Vis, FTIR and fluorescence spectroscopy. The data suggest the incorporation of fluorophores to silica matrix with average nanoparticle diameter of 80 nm, low porosity, specific surface Ãrea of 45m2 g-1 and exhibited considerable ability to fluorescent emission. The photophysical studies for nanoparticles containing the two dyes: rhodamine B and dichlorofluorescein indicated the occurrence of Foster resonant energy transfer (FRET) process. The organofunctionalization of the silica matrix was confirmed by FTIR, UV-Vis and fluorescence spectroscopy results, suggesting the immobilization of folic acid to silica matrix by reaction between the amino groups of the composite (NPs-NH2) with the carboxylate groups of the folic acid. In the second part [Fe(CN)4(isn)(NO)]- and cis-[Ru(bpy)2(isn)(NO)]3+ complexes were immobilized on to fluorescent silica nanoparticles All systems synthesized were characterized by UV-vis, FTIR and chronoamperometry (employing a nitric oxide-selective electrode). The characterization data showed the nitric oxide release in the visible region. The composite formed by the iron nitrosyl complex showed more photosensitivity than ruthenium nitrosyl complex. The results of chronoamperometry showed that the fluorescent dye played no key role on the increase of the wavelength of NO release. All systems showed a slow kinetics of NO release which is very promising for controlled release systems.
No presente trabalho nanomateriais à base de sÃlica foram sintetizados visando aplicaÃÃes em terapia e diagnÃstico por imagem. O trabalho foi dividido em duas partes, sendo a primeira referente à sÃntese de nanopartÃculas fluorescentes modificadas com Ãcido fÃlico. A segunda parte envolve a sÃntese e caracterizaÃÃo de nanopartÃculas de sÃlica fluorescentes modificados com complexos liberadores de Ãxido NÃtrico. As nanopartÃculas de sÃlica fluorescentes foram sintetizadas a partir da incorporaÃÃo de corantes fluorescentes em meio micelar contendo o precursor de sÃlica tetraetilortosilicato. Os materiais foram posteriormente funcionalizados com Ãcido fÃlico e caracterizados por MET, isotermas de adsorÃÃo de nitrogÃnio, UV-Vis, IR e espectroscopia de fluorescÃncia. Os dados sugerem fortemente a incorporaÃÃo dos fluorÃforos a matriz de sÃlica e evidenciam nanomateriais com diÃmetro mÃdio de 80nm, com baixa porosidade, Ãreas superficiais especÃficas de aproximadamente 45m2g-1 e com considerÃvel capacidade de emissÃo fluorescente. Os estudos fotofÃsicos realizados para as nanopartÃculas contendo os dois corantes: rodamina B e 2â,7â-diclorofluoresceÃna evidenciaram a ocorrÃncia do processo de transferÃncia de energia ressonante do tipo Foster (FRET). A organofuncionalizaÃÃo da matriz de sÃlica foi confirmada pelos resultados de FTIR, UV-Vis e espectroscopia de fluorescÃncia, que sugerem a imobilizaÃÃo do Ãcido fÃlico a matriz de sÃlica, por meio de reaÃÃo amÃdica entre grupos NH2 das nanopartÃculas compÃsitas NPs-NH2 com os grupos carboxilatos da molÃcula de Ãcido fÃlico. Na segunda parte do trabalho os complexos [Fe(CN)4(isn)(NO)]- e cis-[Ru(bpy)2(isn)(NO)]3+ foram imobilizados nas nanopartÃculas fluorescentes de sÃlica. Todos os sistemas sintetizados a partir desses complexos foram caracterizados por UV-Vis, FTIR e cronoamperometria utilizando eletrodo seletivo de NO. Os nitrosilos complexos imobilizados liberaram Ãxido nÃtrico na regiÃo do visÃvel, sendo o compÃsito formado pelo nitrosilo complexo de ferro mais fotossensÃvel, comparado ao compÃsito formado pelo nitrosilo complexo de rutÃnio. Todos os sistemas apresentaram uma lenta cinÃtica de liberaÃÃo de NO, resultado promissor para utilizaÃÃo em sistemas onde hà necessidade de liberaÃÃo controlada.

Nanoporous materials for gas purification and thermal insulation have been studied and developed for application in many areas. It is known that a single adsorbent may not adequately control multiple contaminants. Further the utilization of nanoporous material as thermal insulator in building applications is limited due to high cost. Moreover, in view of the global environmental movement for clean air and reduction of heating energy consumption in built environment, the development of new and better nanoporous materials will not only facilitate major advances in gas adsorption and thermal insulation technology, but also meet the new challenges that cannot be met with the nanoporous materials that are currently available. This thesis presents a synthesis of new nanoporous silica based materials, and the characterization and application of these materials for molecular filtration and thermal insulation. Commercial nanoporous materials have been used for benchmarking for the pore properties, the applicability, and the performance of these new materials. First a double metal-silica adsorbent has been synthesized. The preparation procedure is based on the use of sodium silicate coagulated with various ratios of magnesium and calcium salts which yields micro-meso porous structures in the resulting material. The results show that molar ratios of Mg/Ca influence the pore parameters as well as the structure and morphology. The bimodal pore size can be tailored by controlling the Mg/Ca ratio. In the second synthesis, pure mesoporous silica, SNP has been prepared using glycerol as pore forming agent and monovalent salts as coagulant. This leads to material with large surface area and uniformed pore size centred at 43 or 47 nm.  The materials further exhibits a low bulk density in the range of 0.077 to 0.122 g/ml and possess a high porosity in the range of 95-97%. The influence of acid type (organic or inorganic) on the pore parameters and on the tapped density has also been investigated.   A synthesis method has also been developed for the preparation of carbon-silica composites. The method involves a number of routes, which can be summarised as addition of activated carbon particles to (I) the paste, (II) the salt solution, or (III) with the sodium silicate solution. In route II and III the activated carbon is present before coagulation. The routes presented here leads to carbon-silica composites possessing high micro porosity, meso porosity as well as large surface areas. The results further shows that pore size distribution may be tailored based on the route of addition of the carbon particles. Following route I and III a wide pore size (1-30 nm) was obtained whereas by route II a narrow pore size (1-4 nm) was observed.     MgCa-silica chemisorbents were also developed using either potassium hydroxide or potassium permanganate as impregnate chemicals. A direct or post-impregnation procedure was employed. The results revealed that the impregnate route and amount cause a reduction in both specific surface area and pore volume. Finally the thermal conductivity and dynamic adsorption of H2S, SO2 andtoluene were measured. Results show that at room temperature and atmospheric pressure, a thermal conductivity of 28.4 and 29.6 mW/m.K were obtained for the SNP mesoporous silicas. The dynamic adsorption behaviour of the chemisorbents and composites indicate their ability to absorbed H2S, SO2 andtoluene respectively. The highest H2S uptake corresponds to chemisorbents with 11.2-13.6 wt% KMnO4. The effect of impregnation route, amount of KMnO4 and its location in the pore system are likely the key factors in achieving a large H2S uptake. For SO2 adsorption, the highest uptake capacity was observed for MgCa-68/32-KOH. The results further suggest that the key to large SO2 uptake is as a result of the synergetic effect between large mesopore diameter and extensive mesopore volumes. Carbon-silica composites with carbon content 45 wt % exhibits high toluene adsorption with composite via route I having the highest toluene adsorption capacity (27.6 wt % relative to carbon content). The large uptake capacity of this composite was attributed to the presence of high microporosity volume and a wide (1-30 nm) bimodal pore system consisting of extensive mesopore channels (2-30 nm) as well as large surface area. These capacity values of carbon-silica composites are competitive to results obtained for commercial coconut based carbon (31 wt %), and better than commercial alumina-carbon composite (9.5 wt %).

QC 20130408

Orientador: Inez Valeria Pagotto Yoshida
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Neste trabalho foram preparados compósitos de silicona reforçados com argila montmorillonita natural (MT) e orgânica (MT-O). Os compósitos foram obtidos por adição direta das argilas (MT ou MT-O) em goma de silicona de altíssima massa molar (~10 g/mol), que foi reticulada para formar borracha, ou por adição de ¿masterbatches¿ argila/fluido de silicona na matriz de silicona. Previamente à preparação dos ¿masterbatches¿ avaliou-se o efeito de 3 fluidos de silicona: poli(dimetilsiloxano) de terminais ¿Si(CH3)2OH, PDMS-OH, poli(dimetilsiloxano-co-3-óxido de etilenopropilmetilsiloxano), PDMS-POE e poli(dimetilsiloxano-co-metilaminoetilaminopropilsiloxano, PDMS-NH2), na modificação das argilas, selecionando-se aquele que promoveu um maior efeito na expansão das lamelas para a obtenção dos ¿masterbatches¿. Para isto foram preparadas dispersões argila/fluido estudando-se as características morfológicas dessas dispersões por espalhamento de raios X em baixo e alto ângulo utilizando detector bidimensional (SAXS/WAXS-2D). As análises de SAXS/WAXS-2D mostraram que os fluidos PDMS-POE e PDMS-NH2 apresentaram forte tendência de expansão das lamelas das argilas, diferente do PDMS-OH. O fluido PDMS-POE se mostrou mais adequado para a preparação dos compósitos e foi então selecionado para a preparação dos ¿masterbatches¿. Os compósitos preparados via ¿masterbatch¿ ou por adição direta da argila foram caracterizados por medidas de intumescimento em tolueno, difração de raios X, espalhamento de raios X em baixo e alto ângulo, microscopia eletrônica de varredura, microscopia eletrônica de transmissão e ensaios mecânicos sob tração. Os compósitos preparados com os ¿masterbatches¿ apresentaram maior intumescimento em tolueno do que os preparados por adição direta das argilas, indicando que a presença do PDMS-POE aumenta a quantidade de solvente admitida no material. Os ensaios mecânicos mostraram que o compósito preparado com o ¿masterbatch¿ da argila orgânica, PDMS/MB2:5, carregado com apenas 5 phr da MT-O, apresentou praticamente a mesma resistência à tração do que o compósito de PDMS carregado com 30 phr da MT-O, obtido por adição direta da argila no polímero. Além disto, o PDMS/MB2:5 apresentou um aumento de 126% no alongamento na ruptura em relação ao PDMS/MT-O:30. O desempenho mecânico do PDMS/MB2:5 foi atribuído à dispersão nanométrica da argila na matriz de silicona. Por outro lado, no compósito preparado com o ¿masterbatch¿ da MT, PDMS/MB1:5, a argila não se dispersou adequadamente e as propriedades mecânicas obtidas (particularmente, resistência à tração e alongamento na ruptura) não foram satisfatórias. Essa diferença de comportamento foi atribuída aos diferentes arranjos do PDMS-POE entre as lamelas das argilas MT e MT-O. No ¿masterbatch¿ com a MT-O, a parte apolar do PDMS-POE deve se localizar, preferencialmente, no interior das lamelas da argila, resultando em uma dispersão mais eficiente da MT-O, devido à ação lubrificante do fluido do silicona entre as lamelas da argila. A inversão desse arranjo no ¿masterbatch¿ com a MT resulta em uma pobre dispersão da argila no PDMS/MB1:5
Abstract: In this study, silicone composites were prepared with natural (MT) or organomodified (MT-O) montmorillonite clays. The composites were obtained by direct addition of the clays (MT or MT-O) to a high molar mass poly(dimethylsiloxane)-gum (~10 g/mol), which was than crosslinked to form rubber, or by addition of clay/silicone fluid masterbatches into the silicone matrix. Previously to the preparation of the masterbatches, the effect of 3 silicone fluids: (poly(dimethylsiloxane) with ¿Si(CH3)2OH end groups, PDMS-OH, poly(dimethylsiloxane-co-3-ethylenepropylmethylsiloxane oxide), PDMS-PEO, and a poly(dimethylsiloxane-co-aminoethylaminopropylmethylsiloxane), PDMS-NH2) into the clays was studied. The most appropriate silicone fluid, which promoted the greatest effect in the separation of the clay layers, was selected in order to prepare the masterbatches. For this purpose, clay/fluid dispersions were prepared and the morphological characteristics of these dispersions were studied by small angle/wide angle X-ray scattering using a two-dimensional imaging plate detector (SAXS/WAXS-2D). The SAXS/WAXS-2D analisis indicated that the PDMS-POE and the PDMS-NH2 showed greater tendencies to swell the galleries of the clays than the PDMS-OH fluid. The PDMS-PEO was the most appropriate fluid and it was selected to prepare the masterbatches. The composites prepared via masterbatch or by direct clay addition were characterized by swelling measurements in toluene, X-ray diffraction, small angle/wide angle X-ray scattering, scanning electron microscopy, transmission electron microscopy and tensile tests. The composites prepared via masterbatch showed higher toluene swelling than the composites prepared by direct addition, indicating that the presence of the PDMS-POE enchances the solvent amount into the material. The tensile tests showed that the composite with the MT-O masterbatch, PDMS/MB2:5, filled only with 5 phr of O-MT, improved the tensile strength as much as that one obtained with the composite filled with 30 phr of O-MT clay, PDMS/MTO: 30, prepared by direct clay addition. Moreover, the elongation at break was improved at least 126% in comparison to that of the PDMS/MT-O:30. The mechanical performance of PDMS/MB2:5 was attributed to the nanometric dispersion of the clay layers into the silicone matrix. On the other hand, the clay did not disperse well in the composite prepared with the MT masterbatch, PDMS/MB1:5, and the mechanical properties of the this composite (especially, tensile strenght and elongation at break) were not satisfactory.The difference in these behaviours was atribuited to the PDMS-POE arrange between the MT and MT-O clay layers. In the MT-O masterbatch, the PDMS-POE apolar chains should be mainly located inside the clay layers, resulting in an efficient clay dispersion, due to the lubricating effect of the silicone fluid between the layers. The inversion of this arrange in the MT masterbatch results in a poor dispersion of the clay into PDMS/MB1:5
Doutorado
Físico-Química
Doutor em Ciências

Thesis (M.S.)--Case Western Reserve University, 2009
Title from PDF (viewed on 19 August 2009) Department of Mechanical & Aerospace Engineering Includes abstract Includes bibliographical references Available online via the OhioLINK ETD Center

Thesis submitted in fulfilment of the requirements for the degree Doctor of Technology: Chemistry in the Faculty of Applied Sciences at the Cape Peninsula University of Technology 2013
In this present study, the physicochemical properties, nature and morphology of prepared composite materials involving activated carbon, fly ash, nFe3O4, nSiO2 and nZnO in the 1:1 ratio for two components composite materials and 1:1:1 for three components composite materials were investigated. The nature, morphology and elemental characterizations of these materials were carried out by means of modern analytical methods such as scanning electron and transmission electron microscopy (SEM and TEM), x-ray diffraction (XRD), x-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and Fourier transform infrared spectroscopy (FTIR). Other physicochemical characterizations undertaken were CNH analysis, ash content, pH, point of zero charge and surface area and porosity determination by Brunauer, Emmett and Teller (BET). The precursors and composite materials were then applied to the sorption (remediation) of tributyltin (TBT) and triphenyltin (TPT) from artificial seawater and wastewater and the adsorption efficiencies for the precursors and the composites compared. The adsorption of TBT and TPT onto these materials as a function of adsorbent amount, contact time, pH, stirring speed, initial adsorbate concentration and temperature was investigated. Maximum organotin adsorption was recorded within the pH range of normal saline water (pH 8). Approximately 99.95 %, 95.75 %, 96.78 %, 99.88 %, 96.96 %, 99.98 %, 99.99 %, 99.99 % and 99.99 % TBT were removed from 25 mL of 100 mg/L TBT-contaminated artificial seawater using 0.5 g adsorbents at a contact time of 60 min, pH 8, stirring speed 200 rpm and temperature of 80 oC by activated carbon, fly ash, nFe3O4, nSiO2, nZnO, fly ash/activated carbon, nFe3O4/activated carbon, nSiO2/activated carbon and nZnO/activated carbon composite, respectively and the adsorption of TBT onto these adsorbents was endothermic. Approx. 99.99 %, 96.54 %, 95.50 %, 96.92 %, 97.14 %, 99.99 %, 98.44 %, 98.98 % and 99.66 % TPT were also removed from 25 mL of 100 mg/L TPT-contaminated artificial seawater using 0.5 g adsorbents at a contact time of 60 min, pH 8, stirring speed 200 rpm and a temperature of 20 oC by the activated carbon, fly ash, nFe3O4, nSiO2, nZnO, fly ash/activated carbon, nFe3O4/fly ash, nSiO2/fly ash and nZnO/fly ash composite, respectively. The adsorption of TPT onto activated carbon and fly ash/activated carbon composite from TPT – contaminated artificial seawater was endothermic while TPT adsorption onto fly ash, nFe3O4, nSiO2, nZnO, nFe3O4/fly ash, nSiO2/fly ash and nZnO/fly ash composites from TPT – contaminated artificial seawater was exothermic. The adsorption of TBT and TPT onto nFe3O4/fly ash/activated carbon and nSiO2/fly ash/activated carbon composites from TBT – and TPT – contaminated water, respectively were endothermic and approx. 99.98 % and 99.99 % of TBT and TPT, respectively were removed from the initial concentration of 100 mg/L OTC by the composites at a temperature of 80 oC, 60 min contact time, pH 8 and a stirring speed of 200 rpm. The adsorption kinetics of all the precursors and composite materials fitted well with the pseudo second-order kinetic model while the adsorption isotherm data could be well described by the Freundlich isotherm model except TBT adsorption onto nZnO/activated carbon and nFe3O4/activated carbon composite from TBT contaminated artificial seawater, TPT adsorption onto activated carbon and fly ash/activated carbon from TPT contaminated artificial seawater, and TPT sorption onto nSiO2/fly ash/activated carbon composite from TPT – contaminated water which could be described by both the Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Optimal conditions for the adsorption of TBT and TPT from artificial seawater were further applied to TBT and TPT removal from TBT – and TPT – contaminated natural seawater obtained from Cape Town harbour and the results obtained show that 99.71 %, 79.23 %, 80.11 %, 82.86 %, 80.42 %, 99.75 %, 99.88 %, 99.83 % and 99.88 % TBT were removed from TBT – contaminated natural seawater by activated carbon, fly ash, nFe3O4, nSiO2, nZnO, fly ash/activated carbon, nFe3O4/activated carbon, nSiO2/activated carbon and nZnO/activated carbon composite, respectively while 99.90 %, 96.44 %, 95.37 %, 96.75 %, 97.03 %, 99.92 %, 98.42 %, 98.92 % and 99.58 % TPT were removed from TPT – contaminated natural seawater by activated carbon, fly ash, nFe3O4, nSiO2, nZnO, fly ash/activated carbon, nFe3O4/fly ash, nSiO2/fly ash and nZnO/fly ash composite, respectively. Experimental results therefore show that the composite materials present higher organotin adsorption efficiency than the precursors due to the nature and improved properties of the composite materials and can therefore be utilized for the remediation of organotin contamination from industrial and/or shipyards process wastewater to > 99 % reduction before discharge into the environment.

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Jones, Christopher; Committee Member: Koros, William; Committee Member: Lyon, Andrew; Committee Member: Nair, Sankar; Committee Member: Weck, Marcus. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2009.
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Neste trabalho apresentamos o processo de nanoestruturação por máscara híbrida, que permite a fabricação de redes ordenadas de esferas metálicas a partir de um molde polimérico. As máscaras híbridas são formadas em substratos de silício, por spin-coating de uma solução contendo esferas de sílica monodispersas num solvente polimérico fotossensível, posteriormente submetido a um processo de cura por radiação ultravioleta (fotopolimerização). Todas as esferas utilizadas para a fabricação das máscaras foram sintetizadas no próprio laboratório, com o domínio do processo de síntese de esferas submicrométricas de sílica monodispersas para diversos diâmetros. Obtidas as máscaras, dois caminhos poderão ser seguidos: remoção do polímero através de plasma de oxigênio ou remoção seletiva das esferas de sílica por corrosão química. No segundo caso, após a remoção das esferas, obtemos um polímero microporoso que posteriormente pode ser preenchido com o metal de interesse via eletrodeposição. Após a retirada do molde polimérico observamos que os depósitos adquirem um espaçamento e periodicidade semelhante àquele que as esferas de sílica possuíam enquanto envoltas pelo polímero. O domínio da técnica de fabricação de redes metálicas ordenadas ainda é inédito no país e abre um imenso potencial para o estudo de propriedades fotônicas, spintrônicas ou catalíticas, além de possibilitar o desenvolvimento de sensores e dispositivos. Mesmo que a qualidade dos depósitos metálicos tenha ficado aquém de nossas expectativas, resultados preliminares referentes a seu ordenamento revelam estratégias que poderão ser adotadas em trabalhos futuros.

Робота присвячена розробці сорбційних технологій захисту вод від забруднення важкими металами та радіонуклідами з використанням композиційних матеріалів на основі природних глинистих мінералів. Одержано композиційні сорбенти на основі природних глинистих мінералів з нанесеним шаром нанорозмірного Fe0, (окси)гідроксидів заліза(ІІІ) та мікроводоростей Chlorella vulgaris і Scenedesmua asutus. Встановлено значне підвищення сорбційних характеристик одержаних матеріалів щодо сполук Со(ІІ), Cr(VI) та U(VI) порівняно з вихідними мінералами. Вивчено процеси формування поруватої структури шаруватих силікатів при гранулюванні. Досліджено сорбційну здатність гранул по відношенню до іонів U(VI) в розчинах. Показана ефективність використання палигорськіту з нанесеним шаром нанорозмірного Fe0 при створенні в шарах грунту сорбційних екранів для захисту підземних вод від забруднення. Проведено дослідну перевірку ефективності очищення реальних підземних вод від сполук U(VI) з використанням композиційних сорбентів. Запропоновано технологічну схему одержання сорбційних матеріалів.

The increasing demand for energy and the necessity to overcome the depletion of fossil fuel supplies requires that alternative energy sources be developed. Solid Oxide Fuel Cells (SOFCs) are one of the alternative technologies to minimise our dependence on fossil fuel due to their numerous advantages including high efficiency, long-term stability, fuel flexibility and low emissions. However, the development of reliable sealing techniques remains a crucial challenge to overcome to allow usable efficiency and facilitate commercialization. Sealing technology has been object of research for several years. Nevertheless, the optimal solution is yet to be found. The use of a glass composite approach is attractive as it allows the possibility of engineering the properties of the seal, by independently adjusting the particle size distribution and volume fraction of the additives. In the present work, the interaction between various SiO2 based glasses with nickel and B2O3 based glasses with silver were studied. Results as a function of additive particle size distribution (7-100 microns) and volume fraction (0-18%) will be presented. Micrographs, X-ray patterns and CTE measurements showed that the proposed systems have adequate characteristics for usage as seal for fuel cells due to the inertness of the additive particles with the respective glass matrix and predictable long-term chemical and thermal stability. The use of DTMA as a technique to calculate the onset of residual stresses, explores the influence of the additive and its interfacial interactions on the dissipation of energy during deformation. The multi-frequency test lead to an activation energy for stress relaxation between 400 and 600 kJ/mol depending on the different additive content. Furthermore, the temperature difference between de Tg and the onset of residual stresses was calculated showing that increments on the additive content results on a larger temperature range that allows stress relaxation. The mechanical response under compression test was also investigated to identify the potential deformation of a stack during service. The results showed that the glass composites can experience large deformations during the entire service cycle and not only during the isothermal service hold. Moreover, the microstructure in terms of crystalline phase evolves with the test temperature and the applied force, showing an increase of the crystals volume fraction when either the temperature of the applied load increase. The microstructures showed that the additive is getting aligned during deformation, providing an increased resistance to compression against flow of the viscous glass composite. Finally the measurement of the residual stresses as function of cooling rate and additive content revealed that the residual stresses development is minimised for a combination of service conditions including cooling rate under 20 °C/min and glass composite containing a minimum of 12 %vol. Such operating conditions should contribute to maximise the service life of a SOFC stack.
La demande croissante en énergie et la nécessité de surmonter les défis d'épuisement des réserves de combustibles fossiles exigent que des sources d'énergies alternatives soient développées. Les piles à combustible à électrolyte solide sont l'une des technologies alternatives pour réduire notre dépendance aux combustibles fossiles en raison de leurs nombreux avantages, y compris leur haute efficacité, stabilité à long terme, flexibilité dans le choix du carburant et leurs faibles émissions. Cependant, le développement de techniques fiables pour joindre les composantes demeure un défi important à relever pour obtenir une efficacité utilisable et pour faciliter la commercialisation. Les technologies de jointage ont été l'objet de recherches depuis plusieurs années. Néanmoins, la solution optimale demeure encore à être trouvée. L'approche du composite de verre est intéressante car elle permet la possibilité d'optimiser les propriétés du joint en ajustant de façon indépendante la distribution de la taille des particules et la fraction volumique des additifs. Dans le présent travail, l'interaction entre des différents verres composites SiO2 avec nickel, et des verres composite B2O3 avec de l'argent ont été étudiés. Les résultats, en fonction de la distribution de la taille des particules (7-100 microns) et la fraction volumique des additifs (0-18%) seront présentés. Les micrographies, la diffraction des rayons X et les calculs du coefficient d'expansion thermique ont démontré que les systèmes proposés ont les caractéristiques adéquates pour leur utilisation en tant que joint pour les piles à combustible, en raison de l'inertie des particules d'additif avec la matrice de verre, et en raison de la prévisibilité à long terme de la stabilité chimique et thermique. L'utilisation de l'analyse thermomécanique dynamique comme technique pour calculer l'apparition de contraintes résiduelles, explore l'influence de l'additif et ses interactions relatives à l'égard de la dissipation de l'énergie pendant la déformation. Les tests à multifréquences a mené à une énergie d'activation variant entre 400 et 600 kJ/mole pour la relaxation des contraintes, er ce en fonction des différentes quantités d'additifs. De plus, la différence de température entre Tg et l'apparition de contraintes résiduelles a été calculée, et démontre que des incréments de quantités d'additif résultent en un augmentation de l'interval de températures pouvant permettre la relaxation des contraintes. Les résultats du point de vue mécanique, pour des tests de compression ont également été étudiés afin d'identifier les déformations potentielles des assemblages durant l'opération. Les résultats ont montré que les composites de verre peuvent subir de grandes déformations au cours du cycle entier d'opération et non pas seulement pendant la période isotherme. De plus, la microstructure, en termes de phases cristallines, évolue avec la température d'essai et la force appliquée, montrant une augmentation de la fraction volumique des cristaux avec l'augmentation de la température et de la charge appliquée. Les microstructures ont démontré que les particules s'alignent pendant la déformation, offrant une résistance accrue contre la compression, résultant de l'écoulement du composite de verre visqueux. Enfin, le calcul des contraintes résiduelles en fonction de la vitesse de refroidissement et de la fraction volumique d'additifs a révélé que le développement des contraintes résiduel est minimisé dans quelques combinaisons de conditions d'opération, incluant un taux de refroidissement en dessous de 20 °C/min et une fraction volumique minimum de 12% en additif. Ces conditions d'opérations devraient contribuer à maximiser la durée de vie des assemblages de piles à combustible à électrolyte solide.

[ES] El trabajo de investigación descrito en la presente Tesis Doctoral ha sido desarrollado en el marco del proyecto europeo MULTI2HYCAT (grant agreement N. 720783) y se ha centrado en la síntesis y caracterización de materiales mono- y multi-funcionales que presentan sitios catalíticos ácidos, básicos o redox. Diferentes líneas de investigación han sido desarrolladas en paralelo para obtener distintos materiales híbridos que serán empleados en diferentes procesos catalíticos, en línea con las necesidades de los socios industriales del proyecto. Debido a la naturaleza colaborativa del proyecto, cada miembro académico se ha en-centrado en un aspecto del desarrollo de los materiales. Es por ello que el Instituto de Tecnología Química (ITQ-CSIC), donde se ha llevado a cabo esta Tesis Doctoral, se ha centrado en la síntesis de los catalizadores híbridos. Por ello, parte de la caracterización descrita en el Capítulo 3 se ha llevado a cabo en la Università del Piemonte Orientale (IT), durante una estancia de un mes. Ademas, algúnos resultados catalíticos descritos en los Capítulos 3 y 5 han sido obtenidos por la University of Southampton (UK). En el Capítulo 3, se ha descrito la síntesis de dos catalizadores heterogéneos híbridos que presentan moléculas de ácido aril-sulfónico en su composición. En uno de ellos, el anillo aromático presentará átomos de flúor en posición 2, 3, 5, 6. Se han llevado a cabo dos estrategias de síntesis multi-etapas, a través de la síntesis de los precursores alkoxi-silanos, a través de procesos de condensación junto a un precursor de sílice (en ausencia de agentes directores de estructura, a pH neutro y temperaturas bajas) y de una reacción de tethering. Los materiales híbridos han sido caracterizados a través de dife-rentes técnicas. Las propiedades texturales, la estabilidad térmica y la composición química de los catalizadores ha sido estudiada. Además, moléculas sondas han sido adsorbidas en los materiales hibridos y las interacciones entre ellos han sido estudiadas a través de espectroscopias FTIR y RMN multi-nuclear. El catalizador hibrido en que el anillo aromático estaba fluorado resultó ser el más activo catalíticamente en la reac-ción de formación de acetal entre benzaldehído y etilenglicol. Una versión de los hí-bridos en que la superficie había sido pasivada con grupos metilos también fue obteni-da. Las propiedades de los materiales híbridos pasivados fueron comparadas, para po-der estudiar el efecto de la polaridad de la superficie del soporte sobre la actividad catalítica. En el Capítulo 4 se describe la síntesis de órgano-catalizadores híbridos obtenidos por anclaje de precursores de silicio funcionalizados con grupos básicos sobre un soporte del tipo MCM-41. Los catalizadores han sido caracterizados y empleados en diferentes reacciones de formación de enlaces C-C, como la condensación de Knoevenagel y la adición de Michael. Los catalizadores híbridos han sido empleados en la condensación entre furfural y metil isobutil cetona. El catalizador más activo ha sido seleccionado para ser funcionalizado posteriormente con nanoparticulas de paladio y empleado en un proceso catalítico en cascada. Mecanismos de reacción han sido pro-puesto para cada proceso catalítico. El efecto beneficioso debido a la presencia de los grupos silanoles en la superficie del soporte también fue analizado. En el Capítulo 5, la síntesis de catalizadores híbridos multi-funcionales fue descrita. Basándose en los resultados obtenidos en el Capítulo 4, se ha preparado un catalizador que presente grupos aminopropil- y nanopartículas de paladio. Las propiedades estructurales y texturales han sido estudiadas. Además, a través de la microscopia electrónica de transmisión, la distribución dimensional de las nanoparticulas ha sido estimada, resultando en un tamaño medio equivalente a la dimensión de los canales mesoporosos del soporte, MCM-4
[CA] El treball de recerca descrit en aquesta tesi doctoral es va desenvolupar en el marc del projecte europeu MULTI2HYCAT (grant agreement N. 720783) i se centra en la sínte-si i la caracterització de catalitzadors híbrids mono i multifuncionals amb àcid, base o redox actius llocs. S'han desenvolupat diverses línies d'investigació en paral·lel per dissenyar múltiples catalitzadors híbrids per a diferents processos catalítics, basant-se en les necessitats dels socis industrials. A causa del caràcter col·laboratiu del projecte, cada soci acadèmic es va centrar princi-palment en un aspecte de tot el procés. Institut de Tecnologia Química (ITQ-CSIC), on es va desenvolupar aquesta tesi, està principalment centrat en el disseny i síntesi de catalitzadors híbrids. Per això, part dels resultats de caracterització reportats al Capítol 3 s'han dut a terme a la Università del Piemonte Orientale (IT), durant una estada d'un mes. Alguns dels resultats catalítics reportats al Capítol 3 i al Capítol 5 han estat reali-tzats per la Universitat de Southampton (Regne Unit). En el Capítol 3, s'ha descrit la síntesi de dos catalitzadors heterogenis híbrids que pre-senten molècules d'àcid aril-sulfònic en la composició. En un d'ells, l'anell aromàtic presentarà àtoms de fluor en posició 2, 3, 5, 6. S'han dut a terme dues estratègies de síntesi multi-etapes, a través de la síntesi dels precursors alkoxi-silans, mitjançant pro-cessos de condensació al costat d'un precursor de sílice (en absència d'agents directors d'estructura, a pH neutre i temperatures baixes) i d'una reacció de tethering. Els mate-rials híbrids han estat caracteritzats mitjançant diferents tècniques. Les propietats texturals, l'estabilitat tèrmica i la composició química dels catalitzadors ha sigut estudiada. A més, molècules sondes han estat adsorbides en els materials híbrids i les interaccions entre ells han estat estudiades mitjançant espectroscòpies FTIR i RMN multi-nuclear. El catalitzador híbrid en que l'anell aromàtic estava fluorat va resultar ser el més actiu catalíticament en la reacció de formació d'acetal entre benzaldehid i etilenglicol. Una versió dels híbrids en que la superfície havia estat pasivada amb grups metilos també va ser obtinguda. Les propietats dels materials híbrids passivats van ser comparades, per poder estudiar l'efecte de la polaritat de la superfície del suport sobre l'activitat catalítica. En el Capítol 4 es descriu la síntesi d'organo-catalitzadors híbrids obtinguts per ancoratge de precursors de silici funcionalitzats amb grups bàsics sobre un suport del tipus MCM-41. Els catalitzadors han estat caracteritzats i empleats en diferents reaccions de formació d'enllaços C-C, com la condensació de Knoevenagel i l'addició de Michael. Finalment, els catalitzadors híbrids han estat emprats en la condensació entre furfural i metil isobutil cetona. El catalitzador més actiu ha estat seleccionat per a ser funcionalitzat posteriorment amb nanoparticules de pal·ladi i emprat en un procés catalític en cascada. Mecanismes de reacció han estat proposat per a cada procés catalític. L'efecte beneficiós a causa de la presència dels grups silanols en la superfície de suport també va ser analitzat. En el Capítol 5, la síntesi de catalitzadors híbrids multi-funcionals va ser descrita. Basant-se en els resultats obtinguts en el Capítol 4, s'ha preparat un catalitzador que presenti grups aminopropil- i nanopartícules de palladi. Les propietats estructurals i texturals han estat estudiades. A més, a través de la microscòpia electrònica de trans-missió, la distribució dimensional de les nanoparticulas ha estat estimada, resultant en una grandària mitjana equivalent a la dimensió dels canals mesoporosos del suport, MCM-41. El material ha estat emprat com a catalitzador multi-funcional.
[EN] The research work described in this Doctoral Thesis was developed within the frame of the MULTI2HYCAT European Project (grant agreement N. 720783) and it is focused on the synthesis and characterization of mono- and multi-functional hybrid catalysts featuring acid, base or redox active sites. Several research lines have been developed in parallel to design multiple hybrid catalysts for different catalytic processes, building upon the needs of the industrial partners. Due to the collaborative nature of the project, each academic partners mainly focused on one aspect of the whole process. Instituto de Tecnología Química (ITQ-CSIC), where this Thesis was developed, mostly focused on the design and synthesis of the hybrid catalysts. For that, part of the characterization results reported in Chapter 3 have been carried out at Università del Piemonte Orientale (IT), during a one month stay. Some of the catalytic results reported in Chapter 3 and Chapter 5 have been car-ried out by the University of Southampton (UK). In Chapter 3 the synthesis of two different heterogeneous hybrid catalysts carrying aryl-sulfonic moieties, in which the aromatic ring was either fluorinated or not, is re-ported. Two multi-step synthetic approaches were developed, involving the synthesis of the silyl-derivative precursor, template-free one-pot co-condensation (at low tem-perature and neutral pH) and tethering reaction. A multi-technique approach was im-plemented to characterize the hybrid catalysts. Textural properties, thermal stability and chemical makeup of the materials were studied. Moreover, probe molecules were adsorbed onto the hybrids and the interaction were studied with multi-nuclear NMR and FTIR spectroscopies. The catalytic activity of the two hybrids showed superior performances for the fluoro-aryl-sulfonic acid, compared to the non-fluorinated mate-rial, in the acetal formation between benzaldehyde and ethylene glycol. Silanol-capped versions of the hybrids have also been prepared and their properties have been com-pared with those of hydrophilic hybrids, to study the effect of the polarity of the sur-face on the overall catalytic activity of the hybrids. In Chapter 4, the synthesis of hybrid mesoporous organocatalysts, obtained by graft-ing of commercial and custom-made silyl-derivatives onto MCM-41 supports, is re-ported. The hybrid catalysts were characterized and tested for different reactions in-volving C-C bond formation, such as Knoevenagel condensations and Michael addi-tion. Finally, the catalysts were tested in the condensation between furfural and methyl isobutyl ketone and the most performing catalyst was selected for the synthesis of a multi-functional hybrid. Reaction mechanisms have been proposed and the beneficial effect of the surface silanol groups on the catalytic activity was demonstrated. In Chapter 5, the synthesis of hybrid multi-functional catalysts is reported. Building upon the results reported in Chapter 4, a hybrid catalyst featuring aminopropyl moie-ties and palladium nanoparticles was developed. Structural and textural properties of the catalysts were accessed. Moreover, transmission electron microscopy showed a narrow nanoparticles distribution, centered a value equivalent to the size of the meso-porous channels of the support. The catalyst was tested in a tandem process involving the aldol condensation between furfural and methyl isobutyl ketone followed by hy-drogenation of the aldol adduct. The influence of several variables on the activity of the multi-functional catalyst was explored, with the scope of paving the way for more thorough studies to be carried out in flow regime. Lastly, proof-of-concept syntheses of multi-functional hybrid catalysts featuring base sites and supported metal complex are reported.
The research work described in this Doctoral Thesis was developed within the frame of the MULTI2HYCAT European Project (grant agreement N. 720783). I would like to thank la Caixa foundation for my PhD scholarship.
Erigoni, A. (2021). Organic-Inorganic Hybrid Catalysts for Chemical Processes of Industrial Interest [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/165238
TESIS

Polyamide 6/SiO2 hybrid materials were produced by a coupled polymerization reaction of three monomeric components namely 1,1′,1′′,1′′′-silanetetrayltetrakis-(azepan-2-one) (Si(ε-CL)4), 6-aminocaproic acid (ε-ACA) and ε-caprolactam (ε-CL) within one process. Si(ε-CL)4 together with ε-ACA has been found suitable as a precursor monomer for the silica and PA6 components. The accurate adjustment of the molar ratio of both components, as well as the combination of the overall process for producing the polyamide 6/SiO2 hybrid material with the hydrolytic ring opening polymerization of ε-caprolactam is of great importance to achieve homogeneous products with a low extractable content. Water in comparison with ε-ACA has been found unsuitable as an oxygen source to produce uniformly distributed silica. The procedure was carried out in a commercial laboratory autoclave at 8 bar initial pressure. The molecular structure and morphology of the hybrid materials have been investigated by solid state 29Si and 13C NMR spectroscopy, DSC and FTIR spectroscopy and electron microscopy measurements
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Les matériaux hybrides organique/inorganiques ont reçu beaucoup d'attention ces dernières années dans les études des nanomatériaux. En effet, ils possèdent des propriétés physiques et chimiques uniques grâce aux effets synergiques de chaque composant. En particulier, les nanoparticules de silice (SiO2) présentent des caractéristiques intéressantes, comme une bonne stabilité chimique et thermique. Elles peuvent être préparées de différentes tailles et peuvent aussi être facilement fonctionnalisées. Les polymères conducteurs intrinsèques comme le polythiophène et la polyaniline (PANI) peuvent exister sous différents états d'oxydation et donc répondre à des stimuli extérieurs en changeant une de leur caractéristique (couleur, conductivité, etc…). La PANI est un polymère non-toxique, thermiquement stable et peu coûteux avec une conductivité relativement élevée qui a été utilisée comme film antistatique, matériel d'électrode, inhibiteur de corrosion et comme surface sensible de capteur. Depuis la découverte des polymères conducteurs en 1977, plusieurs travaux ont été effectués sur la préparation, la caractérisation et les applications de films polymériques construits à la surface de matériaux comme la silice. Parmi les différents types de composites existants, les particules de type cœur@coquille composées d’un cœur inorganique et d’une couronne de polymère sont les plus prometteurs. Dans cette étude, nous avons donc décidé de travailler sur la synthèse de composites cœur@coquille constitués d’une coquille de PANI et d’un cœur de particules de silice.Dans la littérature, en utilisant des protocoles expérimentaux similaires, deux morphologies très contradictoires ont été obtenues après la polymérisation par oxydation chimique d'aniline en présence de particules de silice : cœur@coquille et framboise (structure inversée avec la PANI comme cœur). Nous avons alors décidé de réexaminer la synthèse de PANI en présence de particules de silice. Pour cela, nous avons, dans un premier temps, synthétisé des particules de silice monodisperses de différentes tailles (300, 160 et 90 nm) par procédé Stöber. Nous avons ensuite réalisé la polymérisation chimique de l'aniline en présence de ces particules de silice dans des conditions contrôlées afin de promouvoir une adsorption des ions aniliniums en surface des particules. Différents paramètres expérimentaux ont été étudiés tels que la température, la concentration en réactifs, la taille des particules… Les résultats en termes de morphologie sont discutés en fonction de ces paramètres. Dans un second temps, nous avons fonctionnalisé la surface des particules de silice par un alcoxysilane afin de favoriser la polymérisation de l’aniline à la surface des particules. Ainsi, nous avons obtenu des structures SiO2@PANI avec une épaisseur de polymère contrôlable. La dernière partie de ce travail traite des premiers essais qui ont été réalisés afin d’utiliser ces composites SiO2@PANi pour des applications environnementales. Deux applications ont notamment été envisagées, l'adsorption de métaux pour l'aspect de particule et la détection de gaz pour les capacités conductrices de la PANI
Organic/inorganic hybrid materials have received much attention in recent years such as in the field of nano-materials. Indeed, these materials possess unique physical and chemical properties due to the synergistic effect of both components. In particular, silica nanoparticles (SiO2) present interesting properties, such as good chemical and thermal stabilities. They can be prepared in different size and can be easily chemically modified. Intrinsically conducting polymers such as polythiophene and polyaniline (PANI) can exist in different oxidation states and respond to external stimuli by changing one of their characteristics (color, conductivity, …). PANI is a non-toxic, thermally stable and low cost polymer with relatively high conductivity that has been used as antistatic coating, electrode materials, corrosion inhibitor and active layer of sensors. Since the discovery of conducting polymer in 1977, several works have been carried out on the preparation, characterization and applications of polymeric films build on various surfaces like silica. Among the different kinds of composites that exist, inorganic-polymer core-shell nanoparticles are more promising candidates. In this study, we decided to work on the synthesis of core@shell hybrid compounds based on PANI shells and silica nanoparticles cores.In the literature, using similar experimental protocols, two morphologies have been obtained after chemical polymerization of aniline in the presence of silica particles: core@shell and raspberry (inverted structure with PANI as core). We thus decided to reinvestigate the synthesis of PANI in the presence of silica particles. For this, we first synthesized silica particles with different sizes by Stöber process. We then performed the chemical polymerization of aniline in the presence of these naked silica particles under different conditions: temperature, concentration of reactive. However, in all cases, we never managed to obtain core@shell structures. Finally, we succeed in developing a method to prepare these core@shell particles which relies on the functionalization of the SiO2 by alkoxysilanes followed by the polymerization of aniline at room temperature. A series of core-shell particles with tunable PANI thickness has been prepared by this method. The last part of this work deals with the first tests that have been carried out in order to use these composites SiO2@PANi for environmental applications. Two applications have been considered, the adsorption of metals for the particle appearance and the detection of gas for the conductive capacities of the PANI

Ces travaux de thèse ont porté sur l’élaboration d’électrodes déformables pour la récupération d’énergie houlomotrice. En effet, la conversion de l’énergie mécanique des vagues en électricité est possible via un système entièrement souple et basé sur la technologie des polymères électroactifs (ou EAP). Ces matériaux ont la capacité de se déformer sous stimuli électrique, d’où la nécessité de développer des matériaux conducteurs déformables. Le matériau EAP choisi pour l’étude est un élastomère silicone. La formulation de composites à matrice élastomère silicone chargée en particules conductrices carbonées (graphite, nanofeuillets de graphite et nanotubes de carbone) est ainsi la piste suivie pour composer des électrodes déformables. Deux méthodes de mélange, en voie fondu, ont été explorées. La première utilise un mélangeur planétaire, et la seconde utilise en plus un mélangeur tri-cylindre. L’influence sur les propriétés électriques des composites, de la méthode de mélange, de la nature de la charge conductrice ainsi du taux de charges, a été analysée. Aussi, l’étude de la percolation électrique ainsi que l’étude des mécanismes de conduction mis en jeux dans les différents composites ont été réalisées, et complétées par l’observation de la morphologie en microscopie optique et en microscopie électronique. Le comportement mécanique des composites en traction a également été analysé. Enfin, les propriétés couplées électro-mécaniques des composites les plus prometteurs ont été testées. Les mesures permettent de proposer une formulation à base de nanotubes de carbone comme électrode déformable
This PhD work presents the development of stretchable electrodes for wave energy harvesting. Indeed, it is possible to convert the mechanical energy of the waves into electricity thanks to a flexible system based on electroactive polymer (EAP) technology. As EAPs have the ability to deform under electrical stimuli, deformable conductive materials are needed. In this study, the chosen EAP is a silicone elastomer. Composites formulated with silicone elastomer matrix filled with carbonaceous conductive particles (graphite, graphite nanoplatelets and carbon nanotubes) were thus developed. Two mixing methods, by melt compounding, have been explored. The first uses a planetary mixer, and the second uses a three roll-mill. The influence of the mixing method, the nature of the fillers and the filler rate on the electrical properties of the composites has been analyzed. The morphology, as well as the percolation and the conduction mechanisms have been studied. The tensile properties of the composites were also analyzed. Finally, the electromechanical coupled properties of the most promising composites were tested, allowing us to propose a formulation as a stretchable electrode

La vaste gamme de combinaisons possibles de cations et anions, ainsi que les excellentes propriétés intrinsèques des liquides ioniques (LIs) peuvent être considérées comme les principaux facteurs qui ont conduit au développement d’une recherche utilisant des LIs comme additifs des matériaux polymère. Ainsi, l'objectif principal de ce travail est d'explorer le rôle de la nature du cation et/ou du anion du LI sur les propriétés des matériaux basées de poly (méthacrylate de méthyle) (PMMA). Dans une première partie, des LIs de type imidazolium et ammonium ont été incorporés au PMMA et des caractérisations morphologiques et structurales ont été effectuées afin de comprendre leur impact sur les propriétés thermiques, viscoélastiques et mécaniques des matériaux résultants. Dans la section suivante, la capacité de ces LIs à base d'imidazolium et d'ammonium en tant qu’agents interfaciaux à la surface de la silice a été évaluée. Sub-micro et nanoparticules de silice, ainsi que les LIs, ont été incorporées dans une matrice de PMMA afin de préparer des composites. L'amélioration des propriétés des matériaux ont été discutées en fonction du degré auquel chaque LI influence la compatibilité entre les particules et la matrice polymère. De plus, ces composites ont été exposés au dioxyde de carbone en état supercritique (scCO2) pour utiliser celui-ci comme agent moussant et ainsi produire des matériaux expansés. Le rôle du LI et des particules de silice pour structurer les matériaux expansés a été analysé. Dans la dernière partie de cette étude, le scCO2 est utilisé comme milieu de réaction pour la modification chimique par greffage de la surface des nanoparticules de silice par des LIs de type imidazolium, contenant également des groupes hydrolysables et différentes chaînes alkyles. Le rôle de la pression et la quantité de LI ajoutées au milieu de réaction, ainsi que la longueur de la chaîne alkyle des LIs se sont avérées essentielles pour contrôler le degré de fonctionnalisation des nanoparticules. Enfin, ces nanoparticules modifiées ont été incorporées dans une matrice PMMA. Des analyses de morphologie ont été utilisées pour évaluer la dispersion des particules dans la matrice et les propriétés physico-chimiques de ces matériaux ont été également étudiées
The large array of cation/anion combinations, and the excellent intrinsic properties of ionic liquids (ILs) open a large range of possibilities in their use as additives to polymer materials. Thus, the main objective of this work is to explore the role of both the cation and anion of a series of ILs on the properties of poly(methyl methacrylate) (PMMA)-based materials. In a first approach, low amounts of imidazolium and ammonium-based ILs were incorporated as additives to PMMA in the molten state. Morphological and structural characterizations were developed in order to understand the impact of the presence of such ILs on the thermal and mechanical properties of the resulting materials. Then, in the following section, the ability of the same imidazolium and ammonium-based ILs as physical modifiers of silica surface was evaluated. In such an approach, ILs were supposed to act as interfacial agents. Sub-micron and nanosize silica particles were used to prepare PMMA composites. Thus, the extents of each IL improve the interfacial interaction between PMMA and silica particles were discussed. In addition, supercritical carbon dioxide (scCO2) was used as foaming agent to produce foamed PMMA-based composites. In such a case, the combined effect of the presence of ILs and silica particles was analyzed regarding the morphology of the foamed structures. In the last section, scCO2 was used as reaction medium, in an environmental friendly approach, to chemically modify silica nanoparticles using a series of imidazolium IL-functionalized silanes (with different alkyl chain lengths). Thermogravimetric analysis (TGA) was used to highlight the effect of the working pressure and the content of such ILs in the reaction medium. The effect of the alkyl chain length on the grafting density of the resulting nanoparticles was also discussed. Finally, novel PMMA-based nanocomposites were prepared by the incorporation of such grafted nanoparticles. Transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) analyses were used to evaluate the state of dispersion of the particles into the polymer matrix. Moreover, the thermal, rheological and mechanical properties of the materials were studied

Thesis (PhD)--Stellenbosch University, 2011.
ENGLISH ABSTRACT: Novel silicone nanocomposites were prepared using poly(acrylonitrile) (PAN) based reinforcing fibres as well as multi-walled carbon nanotubes (MWCNTs). Compatibility of the fibre fillers with the silicone matrix required the synthesis of novel amphiphilic, organic–inorganic graft copolymers of PAN and poly(dimethylsiloxane) (PAN-g-PDMS). These fibre precursor materials were synthesised via the “grafting through” technique using conventional free radical copolymerisation. The PDMS macromonomer content in the feed was varied from 5 wt% to 25 wt% and the molecular weights of the macromonomer were 1000 g.mol-1 and 5000 g.mol-1. The solvent medium of the precipitation reaction was optimised at a volume ratio of 98% benzene to 2% dimethylformamide (DMF). Successful incorporation of PDMS yielded graft copolymer blend materials of PAN-g-PDMS, blended with PAN homopolymer and unreacted PDMS macromonomer. A gradient elution profile was developed to track the successful removal of the PDMS macromonomer via hexane extraction. The gradient profile showed that as the PDMS content in the feed increased, the number of graft molecules in the blend increased relative to the number of PAN homopolymer molecules. The crystallisability of the PAN segments was shown to decrease as the PDMS content increased. The synthesised polymer was used as precursor material for the electrospinning of fibre fillers. The electrospinning of the precursor material was successfully achieved using 100% DMF as electrospinning solution medium. The amphiphilic nature of the precursor material in DMF resulted in self-assembled aggregate structures in the electrospinning solution. An increasing PDMS content was shown to affect the aggregation of the precursor material, and resulted in an increase in the solution viscosity. The “gel-like” solutions limited the achievable fibre morphological control when altering conventional electrospinning parameters such as voltage, tip-to-collector distance, and solution concentrations. The rapid evaporation and stretching of the solution during electrospinning, combined with the phase segregated amphiphilic molecules in solution and the crystallisation of the PAN segments resulted in (non-equilibrium morphology) fully porous fibres. The crystallinity was shown to decrease after electrospinning of the fibre precursor materials. Successful incorporation of surface oxidised MWCNTs into the electrospun fibres was achieved. The content of nanotubes was varied from 2 wt% to 32 wt%. The MWCNTs reduced the mean fibre diameters by acting as cross-linkers between the PAN segments and increasing the solution conductivity. The nanotubes dispersed well throughout the porous structure of the fibres and aligned in the direction of the fibre axis. Fabrication of silicone composites containing nonwoven and aligned fibre mats (with 8 wt% MWCNTs in the fibres, and without) was successfully achieved. The compatibilisation of the PDMS surface segregated domains allowed excellent dispersion and interaction of the PAN based fibre fillers with the silicone matrix. Mechanical analysis showed improved properties as the PDMS content in the fibre increased. The highest PDMS content fibres did, however, exhibit decreased properties. This was ascribed to increased PDMS (soft and weak) content, decreased crystallinity and increased fibre diameter (lower interfacial area). Dramatic improvements in strength, stiffness, strain and toughness were achieved. The most significant result was an increase in strain of 470%. The mechanical results correlated with results of SEM analysis of the fracture surfaces. The dramatic improvements in properties were a result of the fibre strength and ductility, as well as the mechanism of composite failure.
AFRIKAANSE OPSOMMING: Nuwe silikonnanosamestellings is berei deur gebruik te maak van poli(akrilonitriel) (PAN) gebaseerde versterkende vesels wat multi-ommuurde koolstof nanobuisies bevat het. Versoenbaarheid van die vesels met die silikonmatriks het die sintese van nuwe amfifiliese, organies–anorganiese ent-kopolimere van PAN en poli(dimetielsiloksaan) (PAN-g-PDMS) benodig. Die vesel voorlopermateriaal is deur middel van ‘n “ent-deur” vryeradikaalkopolimerisasie gesintetiseer. Die inhoud van die PDMS makromonomeer in die reaksie het gewissel vanaf 5% tot 25%. Die gebruik van twee verskillende molekulêre massas makromonomere is bestudeer (1000 en 5000 g.mol-1). Die optimale oplosmiddelmengsel vir die neerslagreaksie was 'n volume verhouding van 98% benseen tot 2% dimetielformamied (DMF). Suksesvolle insluiting van PDMS het versnitmateriale van PAN-g-PDMS kopolimere gemeng met PAN homopolimere en ongereageerde PDMS makromonomere gelewer. 'n Gradiënteluering- chromatografiese profiel is ontwikkel om die suksesvolle verwydering van die PDMS makromonomere via heksaanekstraksie te bepaal. Die gradiëntprofiel het aangetoon dat indien die PDMS inhoud in die reagense verhoog is, die aantal entmolekules relatief tot PAN homopolimeermolekules ook verhoog het. 'n Toename in PDMS inhoud het egter 'n afname in kristallisasie van die PAN segmente tot gevolg gehad. Die gesintetiseerde polimeer is gebruik as die beginmateriaal vir die elektrospin van veselvullers. Die elektrospin van die beginmateriaal was suksesvol wanneer 100% DMF as elektrospinoplosmiddel gebruik is. Die amfifiliese aard van die beginmateriaal in DMF lei tot outokonstruksie van aggregaatstrukture in die elektrospinoplossing. Toenemende PDMS inhoud beïnvloed die outokonstruksie van die molekules in oplossing en het gelei tot 'n toename in die oplossings se viskositeit. Die "gelagtige" oplossings beperk die haalbare vesel se morfologiese beheerbaarheid wanneer konvensionele elektrospin parameters soos elektriese spanning, punt-tot-versamelaar afstand, en oplossingkonsentrasies gewysig word. Die vinnige verdamping en strek van die oplossing tydens elektrospin, gekombineer met die fase-geskeide amfifiliese molekules in oplossing en die kristallisasie van die PAN segmente, het gelei tot (nie-ewewig morfologie) volledige poreuse vesels. Die kristalliniteit van die veselbeginmaterial het afgeneem nadat elektrospin toegepas is. Die insluiting van die oppervlak-geoksideerde multi-ommuurde koolstof nanobuisies in die elektrogespinde vesels was suksesvol. Die inhoud van die nanobuisies het gewissel van 2 wt% tot 32 wt%. Die MWCNTs het die gemiddelde veseldeursnit verminder deur op te tree as kruisbinders tussen die PAN segmente van die molekules. Die nanobuisies was goed versprei deur die poreuse struktuur van die vesels en dit was gerig in die rigting van die vesel-as. Bereiding van die silikonsamestellings bestaande uit nie-geweefde en gerigte veseloppervlakke (met en sonder 8 wt% multi-ommuurde koolstof nanobuisies in die vesel) was suksesvol. Die versoenbaarheid tussen die oppervlak van die PDMS-geskeide gebiede en die silikonmatriks laat uitstekende verspreiding en interaksie van die PAN-gebaseerde veselvullers met die silikonmatriks toe. Meganiese analise het aangetoon dat die fisiese eienskappe verbeter het namate die PDMS inhoud in die vesel vermeerder het. Die vesels met die hoogste PDMS inhoud het egter verswakte eienskappe getoon. Dit is toegeskryf aan ‘n verhoogde PDMS inhoud (sag en swak), ‘n afname in kristalliniteit en ‘n verhoogde veseldeursnit (laer grensoppervlakke). Dramatiese verbeterings in sterkte, styfheid, verlengbaarheid, vervorming en taaiheid is bereik. Die mees betekenisvolle gevolg was 'n toename in die verrekking van 470%. Die meganiese resultate is gekorreleer met SEM ontleding van die brekingsoppervlakke. Die veselkrag en vervormbaarheid, sowel as die meganisme van die splyting van die samestellings, het tot die dramatiese verbeterings in die meganiese eienskappe gelei.

Current insulation solutions across multiple industries, especially the commercial sector, can be bulky and ineffective when considering their volume. Aerogels are excellent insulators, exhibiting low thermal conductivities and low densities with a porosity of around 95%. Such characteristics make aerogels effective in decreasing conductive heat transfer within a solid. These requirements are crucial for aerospace and spaceflight applications, where sensitive components exist among extreme temperature environments. When implemented into insulation applications, aerogel can perform better than existing technology while using less material, which limits the amount of volume allocated for insulation. The application of these materials into composites can result in enhancing a material's thermal and mechanical properties when exposed to mechanical testing. The main objective of this study was to perform theoretical and experimental analysis on a corrugated composite sandwich structure integrated with aerogel insulation by studying its effective thermal conductivity. The aerogel material used was Pyrogel XT-E, a silica aerogel-based fiberglass insulation manufactured by Aspen Aerogels. Theoretical models of the corrugated composite sandwich structure were constructed in ANSYS Workbench based on geometry from a previous study. The main goal of the theoretical models was to analytically and computationally study the effective thermal conductivity of this sample; the conditions of these simulations were modeled after the experimental setup. Additionally, two insulation studies were performed using the thermal models. The first study was performed on a flat plate structure to determine the optimal thickness of Pyrogel XT-E in a flat plate orientation. The second study compared multiple types of common insulation materials to Pyrogel XT-E when integrated into the corrugated composite sandwich structure model. As expected, aerogel particles and Pyrogel XT-E outperformed all insulation materials and had the lowest effective thermal conductivity. Experimental data was obtained using a test enclosure and a heating element source with an integrated temperature control circuit that was designed and built for this study. This experimental data was compared to the theoretical data obtained from the thermal model simulations. The corrugated composite sandwich structure did not perform as well as expected due to thermal bridging along the composite corrugation. Its effective thermal conductivity was much higher than that of the flat plate structure, even though the effective Pyrogel XT-E layer in the corrugated composite sandwich structure was more than twice as thick as the layer in the flat plate structure. Despite thermal bridging, the corrugated composite sandwich structure exhibits superb thermal resistance, which adds to its impressive strength. Thermal conductivity results from this study can be used to design efficient materials for high structural and thermal stress applications.

Polystyrene (PS) nanocomposite foams were prepared using supercritical fluid (SCF) CO2 as a solvent and blowing agent. PS was first in-situ polymerized with a range of concentrations of montmorillonite layered silicate (MLS). The polymerized samples were then compression molded into 1 to 2mm thick laminates. The laminates were foamed in a batch supercritical CO2 process at various temperatures and pressures from 60°-85°C and 7.6-12MPa. The resulting foams were analyzed by scanning electron microscopy to determine effect of MLS on cellular morphology. Differential scanning calorimetry was used to determine the impact of nanocomposite microstructure on glass transition of the foamed polymer. X-ray diffraction spectra suggested that the PS/MLS composite had an intercalated structure at both the 1% and 3% mixtures, and that the intercalation may be enhanced by the foaming process.

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pos-Graduação em Ciência e Engenharia de Materais, Florianópolis, 2009.
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No presente trabalho foram preparados e caracterizados compósitos antibacterianos à base de BisGMA/TEGDMA e vidro de sílica dopado com prata. Em uma primeira etapa, foi realizada a síntese do vidro dopado com prata a partir do processo sol-gel. Este material foi caracterizado através das técnicas de espectroscopia Raman e no infravermelho com transformada de Fourier (FTIR), difração de raios-x (DRX), granulometria a laser, espectroscopia de absorção atômica e testes de cultura microbiológica (concentração inibitória mínima # CIM, e difusão em ágar). As análises realizadas através dos testes de cultura microbiológica mostraram que o vidro dopado com prata possui ação antibacteriana contra os S.mutans, as principais bactérias causadoras da cárie dental. Este material libera íons de prata em pequenas quantidades para o meio, mesmo após trinta dias de imersão. Uma vez caracterizado, o vidro dopado com prata foi incorporado em uma matriz de BisGMA/TEGDMA para a formação do compósito antibacteriano. O compósito experimental foi caracterizado através de espectroscopia Raman, microdureza Knoop, espectroscopia de absorção atômica, determinação da taxa de absorção de água, solubilidade e coeficiente de difusão do material, resistência à flexão, microscopia eletrônica de varredura (MEV) e análise microbiológica através dos testes de difusão em ágar e contagem de células viáveis. As análises realizadas através dos testes de cultura microbiológica mostraram que o compósito apresentou atividade antibacteriana por meio de contato das bactérias com sua superfície. A liberação dos íons de prata para o meio aquoso foi constante durante os trinta dias de imersão das amostras, no entanto, em um nível inferior à concentração inibitória mínima determinada. Os valores de absorção de água pela matriz do compósito e o coeficiente de difusão mostraram-se satisfatórios, porém os valores de solubilidade foram considerados altos. A resistência mecânica do polímero foi significantemente diminuída (p < 0,001) com a incorporação das partículas de vidro, podendo no entanto, ser otimizada através do projeto microestrutural do compósito, como por exemplo, diminuição do tamanho das partículas, aumento da fração volumétrica na matriz e utilização de um agente de acoplamento para melhorar a transferência de tensões na interface carga-matriz. Através dos resultados obtidos neste trabalho, pode-se concluir que os compósitos desenvolvidos apresentaram atividade antibacteriana por meio de contato das bactérias com a sua superfície, sendo promissores para serem utilizados como materiais de restauração dental com propriedades antibacterianas.
In this work, antibacterial composites based on BisGMA/TEGDMA and silver doped silica glass were prepared and characterized. In a first step, a silver doped silica glass was prepared by a sol-gel process. This material was characterized through Raman and infrared spectroscopy (FTIR), X-ray diffraction (XRD), laser granulometry, atomic absorption spectroscopy and microbiologic tests (minimum inhibitory concentration # MIC, and agar diffusion test). The microbiologic culture analyses showed that the silver doped glass has an antibacterial activity against the S. mutans, the main bacteria responsible for dental caries. This material releases silver ions in low concentrations even after thirty days on water immersion. Once characterized, the silver doped glass was incorporated in a BisGMA/TEGDMA matrix, to produce the antibacterial composite. The experimental composite was characterized through Raman spectroscopy, knoop microhardness (KMH), atomic absorption spectroscopy, water sorption, solubility and the diffusion coefficient, flexural strength, scanning electron microscopy (SEM) and microbiologic analyzes through agar diffusion test and viable cell counting. The microbiologic culture analyses showed that the experimental composite presented antibacterial activity through the direct contact between bacteria and the material#s surface. The silver ions release was constant during the thirty days of water immersion, but in a level inferior to the minimum inhibitory concentration. The water sorption values and the

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Capes
A tecnologia Stealth é a capacidade de navios, aeronaves e submarinos tornarem-se invisíveis à detecção de radares. Para isso, se faz necessário o uso de Materiais Absorvedores de Radiação Eletromagnética – MARE que atuem de forma efetiva no bloqueio da radiação emitida pelos radares. Neste contexto, o objetivo desta pesquisa foi obter um compósito de matriz polimérica de borracha de silicone e carga de ferrita NiZn nanométrica em diferentes concentrações, visando sua utilização como um MARE. A carga foi sintetizada por reação de combustão e os compósitos foram obtidos com concentrações de carga variando entre 16 e 20 g e quantidade de silicone fixa de 20g. Visando investigar a melhor interação entre a carga e a matriz, a carga foi silanizada com 3-aminopropiltrietoxissilano e incorporada apenas ao compósito na concentração de 20:20 de carga:silicone. As técnicas de Difração de Raios-X (DRX), Espectroscopia na Região do Infravermelho por Transformada de Fourrier (FTIR), Microscopia de Força Atômica (AFM), Microscopia eletrônica de Varredura (MEV), Medidas Magnéticas e Eletromagnéticas foram utilizadas para caracterizar a carga e os compósitos. Observou-se que a carga apresentou a fase cristalina do espinélio inverso, com tamanho de partícula nanométrico, com característica de um material magnético mole com valores de absorção de -15,2 dB na faixa de 3 a 4 GHz. Todos os compósitos apresentaram características de MARE com valores de absorção variando de -5 a -17,5 dB na faixa de 3 e 6 GHz. De forma geral, verificou-se que o aumento do teor da carga no compósito dificultou a dispersão e introduziu defeitos volumétricos do tipo poros e aglomerados da carga, porém, não influenciou nos parâmetros magnéticos. A silanização não causou alterações significativas nas propriedades da ferrita, porém contribuiu efetivamente para uma melhor interação com a matriz, resultando diretamente no compósito com o melhor valor de absorção, -14 dB na faixa de 6 GHz, indicando ser o mais promissor para a aplicação como MARE.
Define the Stealth technology as the ability of ships, aircraft and submarines become invisible to radar detection. For this, it is necessary to use materials that effectively reduce this probe, this field that can stand out the use of Radiation Absorbing Materials Electromagnetic - RAME. The objective of this research was to obtain a polymer matrix composite silicone rubber and NiZn ferrite load with different concentrations and better dispersion, for their use as a MARE. The composites were obtained with concentrations varying load between 16 and 20 g of NiZn ferrite synthesized by combustion. To improve the interaction between the cargo and the matrix, it has been silanized with 3 aminopropyltriethoxysilane silane agent and incorporated into a composite. The techniques of X-ray diffraction (XRD), Infrared Spectroscopy in the region by Fourier transform (FTIR), Atomic Force Microscopy (AFM), scanning electron microscopy (SEM), Magnetic and Electromagnetic measurements were used to characterize the load and composite. It was noted that the load presented to the inverse spinel crystalline phase with nanometer particle size with characteristics of a soft magnetic material with 15.2 dB absorption values in the range 3 to 4 GHz. Silanization caused no change significant feature in the ferrite, but contributed effectively for better interaction with the matrix, resulting directly in the composite with the best absorption values, -14 dB at 6 GHz range, indicating that the most promising for application as RAME. For other composites was found that increasing the filler content provided processing difficulties which resulted in the formation of agglomerates and will not influence the magnetic parameters.

Les alliages à mémoire de forme Nickel-Titane sont connus pour leurs propriétés de superélasticité associées à une transformation martensitique élastique, de ferroélasticité liées à la réorientation de variantes de martensite et enfin de mémoire de forme. Les propriétés des matériaux architecturés NiTi, tels que des tricots, des matériaux cellulaires,… dépendent de celles de l'alliage NiTi constituant et de la structure géométrique. L'étude porte sur des matériaux architecturés composites constitués par des matériaux architecturés NiTi saturés par des élastomères silicones. De tels matériaux possèdent potentiellement une gamme étendue de propriétés dépendant à la fois des matériaux constitutifs, mais également des interfaces et de la topologie.La première partie du travail porte sur l'étude de l'interface NiTi silicone. Parmi les solutions testées, le traitement de surface par plasma a été particulièrement étudié. L'influence des paramètres du traitement plasma sur la qualité des interfaces a tout d'abord été étudiée grâce à des essais de pull-out réalisés sur des fils de NiTi enrobés dans des silicones. Les paramètres optimaux de traitement par plasma ont ensuite été appliqués pour élaborer des matériaux architecturés tubulaires constitués d'un tricot NiTi enrobé d'élastomère. Le comportement mécanique du composite ainsi obtenu a été caractérisé par des essais de traction et de gonflement.La deuxième partie de l'étude porte sur le comportement de l'élastomère silicone. Une campagne expérimentale a été menée afin de déterminer l'influence de la température sur le comportement mécanique du silicone, en particulier sur l'accommodation du matériau après la première charge (effet Mullins), l'hystérésis mécanique et la relaxation. Une loi de comportement prenant en compte l'hystérésis mécanique a ensuite été proposée. Inspirée par de nombreux travaux en mécanique des élastomères, l'approche utilise une décomposition de l'espace en un nombre fini de directions. Une loi monodimensionnel incluant les effets d'hystérésis est écrite pour chacune des directions. Ce modèle a été implémenté dans un code de calculs par éléments finis (Abaqus) et a été testé avec des calculs de structures.Dans la troisième partie de l'étude, le formalisme précédent a été utilisé afin de proposer un modèle pour le comportement mécanique du NiTi, en se restreignant dans cette première contribution à la superélasticité. La confrontation des résultats de simulation avec ceux de tests expérimentaux de la littérature sur des plaques isotropes et anisotropes montre les perspectives prometteuses d'une telle approche
Shape memory alloys Nickel-Titanium are well known for their superelastic properties associated with a martensitic elastic transformation, ferroelasticity due to the reorientation of martensite and finally shape memory effects. The properties of architectured NiTi materials, such a knitted NiTi, cellular materials,… depend on the constituting NiTi and of the geometry. The study deals with architectured composite materials made of architectured NiTi materials and silicone rubber elastomer. Such materials present numerous different properties, depending on the constituting materials and also on the interfaces and the topology.The first part of the study focuses on the interface between NiTi and silicone rubber. Among the tested solutions, plasma treatments were especially studied. The influence of treatment parameters on the interface resistance was firstly investigated by means of pull-out tests carried out on NiTi wires embedded in a silicone rubber matrix. Optimized parameters for plasma treatment were then applied in order to elaborate a tubular architectured material made of knitted NiTi and silicone rubber. The mechanical behavior of this composite was characterized by means of tensile and swelling tests.The second part of the study deals with silicone rubber behavior. Experiments were performed in order to evaluate the influence of temperature on the mechanical behavior of silicone rubbers, especially on the stress softening (Mullins Effect), mechanical hysteresis and stress relaxation. A model taking into account the mechanical hysteresis was then proposed. Based on numerous works in the field of rubber mechanics, the approach used a decomposition of the space in a finite number of directions. A monodimensional constitutive equation including hysteresis effects is written for each direction. This model was implemented in a finite elements software (ABAQUS) and was tested with structure simulations. In the third part of the study, the previous formalism was used model the mechanical behavior of NiTi, only In case of superelasticity. The results of the simulations carried out are in good agreement with those reported in the literature for tests on isotropic and anisotropic NiTi plates, which highlights the great interest of such an approach

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência e Engenharia de Materiais, Florianópolis, 2012.
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As inovações na engenharia de superfície/interface são as vertentes mais promissoras no mercado de materiais compósitos. Adicionalmente, seguindo a tendência global pela busca incessante de sustentabilidade, a indústria tem investido intensamente em pesquisas e desenvolvimento (P&D) de novas matérias-primas provenientes de fontes naturais e renováveis, com grande potencial econômico para serem utilizadas como cargas de reforço em matrizes poliméricas destinadas às aplicações de engenharia. As fibras naturais de sílica amorfa (FNSA) inserem-se neste contexto sob todos os pontos de vista, seja econômico ou técnico, uma vez que alia versatilidade de processo, estabilidade termoquímica, baixa toxicidade e capacidade de reforço em matrizes poliméricas, bem como ser proveniente de uma fonte renovável e abundante em território nacional. O presente trabalho visa investigar a viabilidade de utilização das FNSA como agente de reforço de matrizes de polímeros de engenharia através de modificações na química de superfície dessas fibras, e assim alavancar o seu potencial como uma alternativa para substituir as fibras curtas de vidro em aplicações industriais. A modificação de superfície das FNSA foi realizada através do tratamento com diferentes agentes de acoplamento do tipo silano, os quais tem como função aumentar a adesão na interface entre fibras/matriz, e consequentemente, das propriedades mecânicas do compósito final. O PBT foi selecionado como matriz devido a sua conhecida facilidade de processamento, mesmo após a incorporação de grandes quantidades de aditivos. A modificação das FNSA foi avaliada a partir da análise termogravimétrica acoplada à espectroscopia no infravermelho com transformada de Fourier A resistência mecânica e morfologia dos compósitos foi investigada por ensaios de tração e microscopia eletrônica de varredura com o objetivo de correlacionar qual das modificações foi a mais eficiente. Os resultados mostraram que a resistência à tração dos compósitos com fibras modificadas é 40% superior ao material base puro.

Abstract : Surface/interface engineering is the most promising area at the materials composites market. Additionally, following the global trends for development of sustainable products and process, industries have sponsored research and development of new natural raw materials aiming applications as fiber reinforced engineering products. Natural amorphous silicate short fibers (FNSA) achieves all this requirements, either economic or technical, once it's match easy manufacturing, thermo-chemical stability, low toxicity, reinforce ability, likewise being extracted from renewable sources which is abundant throughout Brazilian territory. This work aims to investigate FNSA viability as reinforce agent of thermoplastics engineering polymers. Different surface modifications were performed in order to improve interface adhesion between matrix and FNSA, and consequently improve mechanical properties, driving this composite as an alternative for regular short glass fibers at industrial applications. The surface treatments of FNSA were applied with silane coupling agents provided with different organofunctional groups. PBT was chosen as matrix due its easy manufacturing process even after incorporation of heavy additives loads. The surface chemistry after modification were evaluated through thermogravimetric analyses coupled to a Fourier transformed infrared spectroscopy equipment. Mechanical resistance and composite morphology were investigated through tensile tests and image analyses by electronic scanning microscope. Finally, tensile strength of modified fibers reinforced PBT was 40% higher than neat PBT.

Electroconductive composites are modern materials that are commonly used in many industries such as the construction industry among others. For example these materials can be useful as sensors for monitoring changes in constructions. The aim of this thesis is the research of electrically conductive silicate composite based on secondary raw materials. The design of this composite is based on the development of its own mixtures and experimental verification of the effect of the structure. The introduction part consists of a detailed analysis of 15 materials. Samples of the 5 fine and 2 coarse electrically conductive fillers were tested. Composite with filler Condufit C4 was selected as representative for type of fine fillers. Composite with filler Supragraphite C300 was selected as representative for type of coarse fillers. The selection of the composites was based on the impedance of the fabricated composites with these fillers. Subsequently, the individual components of the primary mixture were substituted. The cement was replaced by high-temperature fly ash in the amount of 20, 30, and 40 %, the aggregate of a similar fraction was replaced by steel sawdust, and the primary electrically conductive fillers were replaced by secondary ones in the amount of 30 and 50 %. All proposed replacements reduced the impedance of the composite. The most effective replacement for impedance reduction was replacement with waste graphite (up to 92 % reduction), which also slightly improved the mechanical properties of the composite. The result of this thesis is an optimized electrically conductive composite based on secondary raw materials with a fine type of filler with 30 % replacement by waste graphite "odpad vysavač"which achieves an impedance of 5 ohms. The partial goal of this thesis is a verification of the influence of moisture on the impedance of composites. Results are significantly affected by moisture when using the coarse type of filler, when using the fine type are not.