Melhorias na eficiência energética motivam o desenvolvimento de isolamentos térmicos cada vez mais eficazes e duráveis. Cerâmicas porosas à base de mulita (Al6Si2O13 ou 3Al2O3.2SiO2) são ideais para essa aplicação devido à alta resistência à corrosão e à densificação. Apesar de rara sua forma mineral, esta é uma das fases mais importantes em cerâmicas tradicionais e avançadas, visto que pode ser obtida a partir de fontes de alumina e sílica, por meio de diversas rotas de processamentos. Sua formação in situ por sinterização reativa tem se destacado dentre os métodos de produção pelos bons resultados mecânicos e eficácia na formação e manutenção de porosidade, entretanto, ainda existem pontos a serem investigados como a influência do tamanho de partícula e porosidade inicial de suas matérias-primas nas propriedades finais das estruturas. Neste trabalho, foram produzidas peças porosas de alumina-mulita in situ a partir de suspensões de sílica coloidal com diferentes concentrações (30, 40 e 50 %) e hidróxidos de alumínio de diferentes granulometrias (fino, HAF e grosso, HAG) pré-calcinados em várias temperaturas (500-1500 °C), pelo processo de moldagem direta para aplicação como isolante térmico em temperaturas acima de 1000 °C. As amostras (verdes e tratadas termicamente - 1500 °C) foram submetidas à ensaios mecânicos (módulo elástico e resistência à ruptura por compressão e flexão), análise microestrutural (MEV e DRX) e de propriedades físicas (porosidade total, densidades e variação térmica dimensional). As aluminas de transição provenientes da calcinação agiram como agentes porogênicos no sistema e juntamente com a sílica coloidal (com funções simultâneas de fluido de mistura, agente ligante, aditivo de secagem e fonte de SiO2 amorfa) formaram estruturas com grande variação de propriedades. Estruturas com HAF apresentaram porosidade próxima a 40% e elevadas propriedades mecânicas, e com HAG foram obtidos níveis de porosidade acima de 50 % e baixas resistências. As composições mistas, contendo tanto HAF como HAG, obtiveram bons resultados mecânicos e porosidades acima de 50 %, mostrando-se bons candidatos para uso como isolamento térmico. Todos os sistemas contiveram a fase de mulita em maior quantidade coexistindo com alfa alumina (Coríndon). / Improvements in energy efficiency motivate the development of more effective and durable thermal insulation. Porous ceramics based on mullite (Al6Si2O13 or 3Al2O3.2SiO2) have great potential for this application due its high resistance to corrosion and densification. Although rare in its mineral form, this is one of the most important phases in traditional and advanced ceramics because it can be obtained from alumina and silica sources, through various processing routes. Among them, the solid-state in situ reactions by reactive sintering stands out for its good mechanical properties and efficiency in the formation and maintenance of pores. However, how particle size and initial porosity of its raw materials influences the final properties still requires investigation. In this work, porous ceramics of alumina-mullite were produced in situ from aqueous suspensions of colloidal silica with different concentrations (30, 40 and 50 %) and aluminum hydroxides of different grain sizes (fine, HAF and coarse, HAG) pre-calcined in several temperatures (500-1500 °C) by direct casting process for application as a thermal insulation at temperatures above 1000 °C. The samples (green and thermally treated - 1500 °C) were submitted to mechanical tests (elastic modulus and resistance to rupture by compression and flexural), microstructural analysis (SEM and XRD) and physical properties characterization (total porosity, densities and dimensional thermal variation). The transition aluminas acted as porogenic agents in the system and with the colloidal silica (with simultaneous functions of mixing fluid, binding agent, drying additive and source of amorphous SiO2), formed structures with great properties\' variation. Samples with HAF had porosity close to 40% and high mechanical properties, and with HAG, porosity levels above 50 % and low resistances were obtained. The mixed compositions, containing both HAF and HAG, obtained good mechanical results and porosities above 50 %, showing great potential to thermal insulation. All systems contained most of mullite coexisting with alpha alumina phase (Corundum).

This thesis is about using nuclear magnetic resonance (NMR) spectroscopy for studying soft materials. Soft materials may be encountered everyday by most readers of this thesis, for example when taking a shower or watching TV. The usefulness of these materials originates from them being soft yet, at the same time, having some kind of a structure. The characteristic length scale of those structures is often on the order of nanometers (10-9 m) and the structure can respond to various external stimuli such as temperature, electric and magnetic fields, or the presence of interfaces. NMR spectroscopy excels when studying soft materials because it is a non-invasive technique with a large spectral resolution. Moreover, different NMR methods allow us to study local molecular dynamics or longer-range translational diffusion. Understanding those latter aspects is very important for the development of dynamic and responsive materials. Papers I-III present our work on assessing molecular adsorption on interfaces in colloidal dispersions. Here, carbon nanotubes (CNTs) or silica particles were the colloidal substrates to which proteins, polymers or surfactants adsorbed. Papers IV-VI concern ionic mobility in liquid crystals (LCs). The influence of material structure on, for example, the anisotropy of diffusion or on the association/dissociation of ions was studied in several LC phases. / QC 20110225

<p>Denna avhandling presenterar experimentella studier av polyelektrolytadsorption på motsatt laddade ytor, där substrat av både kiseloxid och blekt barrsulfatmassa har använts. Ett huvudsakligt syfte med denna forskning var att karaktärisera konformationen hos adsorberade skikt av katjonisk polyakrylamid (CPAM) i jämförelse med katjonisk dextran (Cdextran) och relatera denna information till inbindningskapaciteten av kolloidal kiselsyra. Ett andra syfte i denna avhandling var att studera kinetiken för sekventiell adsorption av polyamidamin epiklorhydrin (PAE) och karboxymetyl cellulosa (CMC) på massafibrer och att bestämma adsorptionsisotermer för deponering av polyelektrolyter skikt för skikt på massafibrer.</p><p>Adsorptionen av CPAM på kiseloxidytor studeras med stagnationspunkts-reflektometri och kvartskristalls-mikrogravimetri för att bestämma adsorptionskinetiken och mättnadsadsorptionens beroende av polyelektrolytens laddningstäthet, pH och NaCl koncentration. Konformationen hos adsorberade skikt av CPAM och Cdextran bestämdes både före och efter sekundär tillsats av kolloidal kiselsyra (CS) och adsorptionen av CS kvantifierades också som funktion av yttäckningen av polyelektrolyt.</p><p>Resultaten indikerar att laddningstätheten hos CPAM kontrollerar den adsorberade mängden på kiseloxidytor vid låga NaCl koncentrationer. Både adsorptionen av CPAM och Cdextran på kiseloxid visades vara effektiv i NaCl koncentrationer upp till 1 M, vilket indikerar ett signifikant bidrag av icke-jonisk interaktion mellan polyelektrolyterna och kiseloxid. Adsorptionen av CS var högre på föradsorberad CPAM än Cdextran. Konformationen hos de adsorberade skikten efter tillsats av CS sågs expandera signifikant för skikt baserade på CPAM medan skikt av Cdextran vid låga salthalter verkade återta sin konformation efter en temporär expansion.</p><p>I den andra delen av avhandlingen studerades sekventiell adsorption av PAE och CMC på massafibrer. Adsorptionsisotermer skikt för skikt på avkryllad massa visade att PAE adsorberade i större mängd än CMC, både i hänseende av massa och laddning. Adsorptionen av PAE var signifikant långsammare än CMC och adsorptionstiden till 90% av mättnadsadsorptionen bestämdes till 3 respektive 1 minut. Zetapotentialen för kryll bestämdes för adsorption av de två första polyelektrolytskikten och resultaten tydde på att kryllmaterialet omladdade inom en minut efter tillsatserna av polyelektrolyt. Reflektometriförsök inom sekventiell adsorption av PAE och CMC på kiseloxid antydde att den låga molekylviktsfraktionen av PAE störde uppbyggnaden av polyelektrolyt-multiskikten.</p> / <p>This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres.</p><p>The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation of adsorbed layers of CPAM and Cdextran, analysed in terms of amount of water and layer thickness, was determined both before and after the secondary adsorption of colloidal silica (CS), and the adsorption of CS was also quantified as a function of the surface coverage of the polyelectrolyte.</p><p>Results indicate that the charge density of CPAM controlled the amount of the polyelectrolyte adsorbed on silica surfaces at low NaCl concentrations. The adsorption of both CPAM and Cdextran on silica was shown to be effective at up to 1 M NaCl concentrations, which indicates that non-ionic interactions between the polyelectrolytes and silica contribute significantly. CS adsorption was higher on pre-adsorbed CPAM than on Cdextran. The conformation of the adsorbed layer after CS addition was seen to expand significantly in CPAM-based layers, while the Cdextran layer appeared to restore its conformation after a temporary expansion at low salt concentrations.</p><p>In the second part of the thesis, the sequential adsorption of PAE and CMC on pulp fibres was determined using the polyelectrolyte titration technique. Layer-by-layer adsorption isotherms derived on fractionated pulp showed that PAE adsorbed in higher amounts than CMC did, both in terms of adsorbed mass and adsorbed charge. The adsorption of PAE was significantly slower compared to CMC, and the adsorption times required to reach 90% of the saturation adsorption were 3 and 1 min, respectively. The zeta potential of pulp fines was determined for the adsorption of the two first polyelectrolyte layers, and data indicated that the fines recharge within one minute after the polyelectrolyte additions. Reflectometry experiments regarding the sequential adsorption of PAE and CMC on silica indicated that the low-molecular-weight fraction of PAE disturbed the formation of polyelectrolyte multilayers.</p>

The inherent thermal resistance of ceramic membranes allows for treatment of industrial waters at elevated temperatures. Traditionally, the high temperature of wastewater has been an issue compromising the integrity of polymeric membrane systems or requiring the temperature to be lowered for further treatments. In ceramic membrane systems, a decrease in viscosity with increasing temperature, however, can be utilized, which increases the permeate flux. In this study, the fouling of ceramic ultrafiltration by feed solutions containing colloidal silica was evaluated at temperatures between 25 – 90 °C seen in various industries. Ceramic membranes were able to perform well at elevated temperatures up to 90 ºC with sustained mechanical and chemical integrity. Results showed net benefit of filtration at elevated temperatures on permeate flux in spite of increasing total fouling resistance with temperature. When the temperature increased from 25 to 90 °C, there was a 90% increase in steady-state permeate flux. The dominant resistance was physically removable fouling, and the increase in fouling with feed temperature was supported by force balance analyses. This study provides a foundation from which further studies can be developed including pilot-scale testing, use of real wastewater, and the effects of operating conditions.

No description available.

Cette étude porte sur le développement de nanoparticules pour différentes applicationsbiologiques. Trois systèmes de nanoparticules ont été mis au point : des clusters de nanoparticulesmagnétiques pour l’extraction par magnétophorèse d’objets biologiques, des agents de contrastemultimodaux (IRM, fluorescence dans le proche infrarouge) pour le diagnostic de l’athérosclérose etdes nanoparticules de silice fluorescentes doublement marquées pour la détection de tumeurs in vivo.Au cours de cette étude, une stratégie de greffage de surface de silice par des macromolécules depoly(oxyde d’éthylène) (PEG) permettant d’atteindre de hautes densités de greffage. Cette PEGylationpermet, d’annuler les interactions non spécifiques dans le cadre de l’extraction magnétique rendantainsi ce système plus efficace, et de conférer aux nanoparticules des propriétés de furtivité vis-à-vis dusystème immunitaire dans le cadre du marquage de tumeurs. Le contrôle du nombre de biomoléculesgreffées régiosélectivement sur les nanoparticules (Annexine A5, ou fragments d’anticorps) ainsi quel’étude des interactions biomoléculaires par des techniques de biophysique (SPR, QCM-D) ont permisd’optimiser la propriété de reconnaissance des nano-objets pour leurs cible respective. Enfin, les nanoobjetsont été évalués dans le cadre de leur application. / The aim of this study was the design of nanoparticles for three different biologicalapplications: magnetic nanoparticles cluster for magnetic extraction of biological materials,multimodal contrast agents (MRI and near infrared fluorescence imaging) for atherosclerosisdiagnosis, and fluorescent silica nanoparticles with two different dyes for in vitro and in vivo tumorlabeling. One part of the project dealt with the developement of a new grafting method ofpoly(ethylene oxide) macromolecules onto nanoparticle’s silica surfaces (PEGylation) in order toobtain a high grafting densities. The obtained results have shown that this PEGylation reduces the nonspecificprotein adsorption allowing a better extraction and sorting efficiency, and also permitsnanoparticles to escape the surveillance of the immune system for in vivo tumor labeling. Therefore,the biomolecular recognition of the nanoparticles has been optimized by controlling the number ofconjugated biomolecules and by studying this biomolecular recognition using biophysical methods(SPR, QCM-D). Finally, the different nano-objects were evaluated in the context of their respectiveapplication.

Impregnace na bázi silikátů se široce používá k ochraně betonu před agresivním prostředím. Pochopení aspektů týkajících se tohoto typu impregnace však není zcela jasné. Tato práce představuje informaci o jednotlivých vlastnostech vybraných křemičitanů, přesněji draselného, sodného, lithného a koloidního oxidu křemičitého (koloidní silika), dále o účinnosti z hlediska nasákavosti, stupni účinku na hydrataci cementu, schopnosti těchto látek uzavřít póry a jejích vliv na mikrostrukturu cementového substrátu a na penetrační schopnost. Účinnost filmotvorných látek byla hodnocena jak na čerstvém cementovém tmelu, tak na vyzrálejším, aplikovaných po 1 a 24 hodinách od smíchání směsi. K dosažení kvalitativních výsledků byly použity instrumentální metody, jako je rtuťová porosimetrie, rheometrie, izotermální kalorimetrie, rentgenová difrakční analýza a skenovací elektronová mikroskopie. S ohledem na provedené testy byla prokázána určitá účinnost ošetřujících přísad. Výsledky všech testů ukázaly vyšší účinnost těchto látek v případě ošetření na vyzrálejším cementovém povrchu, což bylo pravděpodobně způsobeno vyšším stupněm hydratace, díky čemuž se vytvořily nové fáze, se kterými silikáty byly schopné zareagovat a jistým způsobem ovlivnit mikrostrukturu.

No description available.

Denna avhandling presenterar experimentella studier av polyelektrolytadsorption på motsatt laddade ytor, där substrat av både kiseloxid och blekt barrsulfatmassa har använts. Ett huvudsakligt syfte med denna forskning var att karaktärisera konformationen hos adsorberade skikt av katjonisk polyakrylamid (CPAM) i jämförelse med katjonisk dextran (Cdextran) och relatera denna information till inbindningskapaciteten av kolloidal kiselsyra. Ett andra syfte i denna avhandling var att studera kinetiken för sekventiell adsorption av polyamidamin epiklorhydrin (PAE) och karboxymetyl cellulosa (CMC) på massafibrer och att bestämma adsorptionsisotermer för deponering av polyelektrolyter skikt för skikt på massafibrer. Adsorptionen av CPAM på kiseloxidytor studeras med stagnationspunkts-reflektometri och kvartskristalls-mikrogravimetri för att bestämma adsorptionskinetiken och mättnadsadsorptionens beroende av polyelektrolytens laddningstäthet, pH och NaCl koncentration. Konformationen hos adsorberade skikt av CPAM och Cdextran bestämdes både före och efter sekundär tillsats av kolloidal kiselsyra (CS) och adsorptionen av CS kvantifierades också som funktion av yttäckningen av polyelektrolyt. Resultaten indikerar att laddningstätheten hos CPAM kontrollerar den adsorberade mängden på kiseloxidytor vid låga NaCl koncentrationer. Både adsorptionen av CPAM och Cdextran på kiseloxid visades vara effektiv i NaCl koncentrationer upp till 1 M, vilket indikerar ett signifikant bidrag av icke-jonisk interaktion mellan polyelektrolyterna och kiseloxid. Adsorptionen av CS var högre på föradsorberad CPAM än Cdextran. Konformationen hos de adsorberade skikten efter tillsats av CS sågs expandera signifikant för skikt baserade på CPAM medan skikt av Cdextran vid låga salthalter verkade återta sin konformation efter en temporär expansion. I den andra delen av avhandlingen studerades sekventiell adsorption av PAE och CMC på massafibrer. Adsorptionsisotermer skikt för skikt på avkryllad massa visade att PAE adsorberade i större mängd än CMC, både i hänseende av massa och laddning. Adsorptionen av PAE var signifikant långsammare än CMC och adsorptionstiden till 90% av mättnadsadsorptionen bestämdes till 3 respektive 1 minut. Zetapotentialen för kryll bestämdes för adsorption av de två första polyelektrolytskikten och resultaten tydde på att kryllmaterialet omladdade inom en minut efter tillsatserna av polyelektrolyt. Reflektometriförsök inom sekventiell adsorption av PAE och CMC på kiseloxid antydde att den låga molekylviktsfraktionen av PAE störde uppbyggnaden av polyelektrolyt-multiskikten. / This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres. The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation of adsorbed layers of CPAM and Cdextran, analysed in terms of amount of water and layer thickness, was determined both before and after the secondary adsorption of colloidal silica (CS), and the adsorption of CS was also quantified as a function of the surface coverage of the polyelectrolyte. Results indicate that the charge density of CPAM controlled the amount of the polyelectrolyte adsorbed on silica surfaces at low NaCl concentrations. The adsorption of both CPAM and Cdextran on silica was shown to be effective at up to 1 M NaCl concentrations, which indicates that non-ionic interactions between the polyelectrolytes and silica contribute significantly. CS adsorption was higher on pre-adsorbed CPAM than on Cdextran. The conformation of the adsorbed layer after CS addition was seen to expand significantly in CPAM-based layers, while the Cdextran layer appeared to restore its conformation after a temporary expansion at low salt concentrations. In the second part of the thesis, the sequential adsorption of PAE and CMC on pulp fibres was determined using the polyelectrolyte titration technique. Layer-by-layer adsorption isotherms derived on fractionated pulp showed that PAE adsorbed in higher amounts than CMC did, both in terms of adsorbed mass and adsorbed charge. The adsorption of PAE was significantly slower compared to CMC, and the adsorption times required to reach 90% of the saturation adsorption were 3 and 1 min, respectively. The zeta potential of pulp fines was determined for the adsorption of the two first polyelectrolyte layers, and data indicated that the fines recharge within one minute after the polyelectrolyte additions. Reflectometry experiments regarding the sequential adsorption of PAE and CMC on silica indicated that the low-molecular-weight fraction of PAE disturbed the formation of polyelectrolyte multilayers. / QC 20101112