The formation of thick, robust, mesoporous titania films is of particular interest and the focus of this thesis has been the study and comparison of the surfactant templated formation of such materials by three methods. film structure has been studied using TEM and small angle X-ray and neutron scattering while formation was studied using Brewster angle microscopy and X-ray and neutron reflectometry. Repetitive dip-coating was used to produce films for development into dye sensitized solar cells allowing development of cells of reasonable efficiency when four depositions were used. This research showed that repetitive deposition does not necessarily lead to a linear increase in film thickness, as subsequent depositions may be thinner making the future application of this method for solar cells problematic. In contrast to dip-coating, a fluorinated surfactant was used in a largely alcohol solvent to produce mesostructured films at the air-solution interface. Film formation occurred by a surface driven mechanism via addition of individual precursors and micelles producing a lamellar structure in-situ. After removal from the interface a cubic phase developed after drying of the film. Although films are not stable to calcination the calcined material remains porous. The surfactant templated formation of ZnO films at the air-solution interface was also studied. The di-block copolymer PEPEG2250 was also used to template titania films at the air-solution interface from alcoholic solvent. Film formation occurred via a bulk driven mechanism. Although these films were found to be disordered at the interface and not stable to calcinations they were unusually robust and self supporting after removal from the interface. Studies of subphase development allowed the first time-resolved observation of surfactant templated titania particle formation.

No description available.

No description available.

La réalisation du stockage d'énergie et le retour de l'approvisionnement en énergie est crucial pour plusieurs applications (VE, téléphones portables, ordinateurs portables). Des électrodes épaisses avec des matériaux inactifs minimisés dans la batterie globale peuvent améliorer la densité d'énergie des batteries lithium-ion. Spark Plasma Sintering est une technique de densification avancée qui a été utilisée pour préparer des électrodes épaisses en quelques minutes. L'approche de modèle est adoptée pour préparer des électrodes poreuses avec des tailles de pores et des morphologies interconnectées bien contrôlées. Ici, des particules de microsize de chlorure de sodium sont utilisées comme agent de gabarit pour créer des pores à l'intérieur des électrodes épaisses. Ces électrodes frittées sans liant sont auto-supportées, ce qui contribue à augmenter la densité énergétique des batteries lithium-ion. Les performances électrochimiques des batteries demi- et pleines révèlent une capacité surfacique spécifique remarquable (20 mA h cm-2), qui est 4 fois supérieure à celle des électrodes de 100 μm présentes dans les batteries Li-ion classiques (5 mAh cm) -2). L'étude morphologique 3D est réalisée par micro-tomodensitométrie pour obtenir des valeurs de tortuosité et des distributions de tailles de pores conduisant à une forte corrélation avec leurs propriétés électrochimiques. Ces résultats démontrent que le couplage entre le procédé de matriçage de sel et le frittage par plasma d'étincelles est également appliqué pour la fabrication d'électrodes épaisses en utilisant d'autres matériaux actifs et que différentes configurations de cellules sont également proposées / The achievement of energy storage and return of energy supply is crucial for several applications (EVs, cellphones, laptops). Thick electrodes with minimized inactive materials in the overall battery can improve the energy density of lithium ion batteries. Spark Plasma Sintering is an advanced densification technique has been used to prepare thick electrodes in minutes. The templating approach is adopted for preparing porous electrodes with interconnected well-controlled pore sizes and morphologies. Here, sodium chloride microsize particles are used as a templating agent to create pores inside the thick electrodes. These sintered binder-free electrodes are self-supported that helps to increase the energy density of lithium ion batteries. The electrochemical performances of half and full batteries reveal a remarkable specific areal capacity (20 mA h cm−2), which is 4 times higher than those of 100 μm thick electrodes present in conventional tape-casted Li–ion batteries (5 mA h cm−2). The 3D morphological study is carried out by micro computed tomography to obtain tortuosity values and pore size distributions leading to a strong correlation with their electrochemical properties. These results demonstrate that the coupling between the salt templating method and the spark plasma sintering is also applied for thick electrodes fabrication using other active materials and also different cell configurations are proposed

No / The purpose of this study was to assess the accuracy of digital radiographs and hence their effectiveness in templating. The methodology involved a retrospective study of post operative radiographs of patients with hemiarthroplasty of the hip. Three observers made observations blinded to each other¿s measurements. A statistical analysis of the data highlights magnification varying from 6 to 31 percent. There is a statistically significant relationship between the size of the error (size measured on radiograph minus implant size, i.e. magnification) and the implant size (p = 0.005) but the percentage error (error/implant size x 100) is independent of implant size (p = 0.505). It is our impression that digital radiographs and templating on the digital radiographs should not be considered a precise process.

Heterogeneous Templated Grain Growth (HTGG) is a developing method to fabricate designedcrystallographic textures of polycrystalline materials. Designed crystallographic texturesare important for enhancing desired material properties for specific applications. Four steps toHTGG have been identified: fabricating single crystal seeds, aligning seeds embedded into a powdermatrix, compacting seeds in the powder matrix, and promoting templating through sintering.Experimental research was performed on processing parameters, powder particle size and compaction,to indicate template coarsening trends during sintering. The results demonstrated thatlarger powder particles were influenced faster by the seeds crystallographic orientations comparedto smaller particles. The local effects of porosity on the seed and powder interface were analyzedand this powder size effect was explained in the context of the theory of Zener pinning.

Nanoporous carbon materials are widely used in industry as adsorbents or catalyst supports, whilst becoming increasingly critical to the developing fields of energy storage / generation or separation technologies. In this thesis, the combined use of carbohydrate hydrothermal carbonisation (HTC) and templating strategies is demonstrated as an efficient route to nanostructured carbonaceous materials. HTC is an aqueous-phase, low-temperature (e.g. 130 – 200 °C) carbonisation, which proceeds via dehydration / poly-condensation of carbon precursors (e.g. carbohydrates and their derivatives), allowing facile access to highly functional carbonaceous materials. Whilst possessing utile, modifiable surface functional groups (e.g. -OH and -C=O-containing moieties), materials synthesised via HTC typically present limited accessible surface area or pore volume. Therefore, this thesis focuses on the development of fabrication routes to HTC materials which present enhanced textural properties and well-defined porosity. In the first discussed synthesis, a combined hard templating / HTC route was investigated using a range of sacrificial inorganic templates (e.g. mesoporous silica beads and macroporous alumina membranes (AAO)). Via pore impregnation of mesoporous silica beads with a biomass-derived carbon source (e.g. 2-furaldehyde) and subsequent HTC at 180 oC, an inorganic / carbonaceous hybrid material was produced. Removal of the template component by acid etching revealed the replication of the silica into mesoporous carbonaceous spheres (particle size ~ 5 μm), representing the inverse morphological structure of the original inorganic body. Surface analysis (e.g. FTIR) indicated a material decorated with hydrophilic (oxygenated) functional groups. Further thermal treatment at increasingly elevated temperatures (e.g. at 350, 550, 750 oC) under inert atmosphere allowed manipulation of functionalities from polar hydrophilic to increasingly non-polar / hydrophobic structural motifs (e.g. extension of the aromatic / pseudo-graphitic nature), thus demonstrating a process capable of simultaneous control of nanostructure and surface / bulk chemistry. As an extension of this approach, carbonaceous tubular nanostructures with controlled surface functionality were synthesised by the nanocasting of uniform, linear macropores of an AAO template (~ 200 nm). In this example, material porosity could be controlled, showing increasingly microporous tube wall features as post carbonisation temperature increased. Additionally, by taking advantage of modifiable surface groups, the introduction of useful polymeric moieties (i.e. grafting of thermoresponsive poly(N-isopropylacrylamide)) was also demonstrated, potentially enabling application of these interesting tubular structures in the fields of biotechnology (e.g. enzyme immobilization) and medicine (e.g. as drug micro-containers). Complimentary to these hard templating routes, a combined HTC / soft templating route for the direct synthesis of ordered porous carbonaceous materials was also developed. After selection of structural directing agents and optimisation of synthesis composition, the F127 triblock copolymer (i.e. ethylene oxide (EO)106 propylene oxide (PO)70 ethylene oxide (EO)106) / D-Fructose system was extensively studied. D-Fructose was found to be a useful carbon precursor as the HTC process could be performed at 130 oC, thus allowing access to stable micellular phase. Thermolytic template removal from the synthesised ordered copolymer / carbon composite yielded functional cuboctahedron single crystalline-like particles (~ 5 μm) with well ordered pore structure of a near perfect cubic Im3m symmetry. N2 sorption analysis revealed a predominantly microporous carbonaceous material (i.e. Type I isotherm, SBET = 257 m2g-1, 79 % microporosity) possessing a pore size of ca. 0.9 nm. The addition of a simple pore swelling additive (e.g. trimethylbenzene (TMB)) to this system was found to direct pore size into the mesopore size domain (i.e. Type IV isotherm, SBET = 116 m2g-1, 60 % mesoporosity) generating pore size of ca. 4 nm. It is proposed that in both cases as HTC proceeds to generate a polyfuran-like network, the organised block copolymer micellular phase is essentially “templated”, either via hydrogen bonding between hydrophilic poly(EO) moiety and the carbohydrate or via hydrophobic interaction between hydrophobic poly(PO) moiety and forming polyfuran-like network, whilst the additive TMB presumably interact with poly(PO) moieties, thus swelling the hydrophobic region expanding the micelle template size further into the mesopore range. / Nanoporöse kohlenstoffbasierte Materialien sind in der Industrie als Adsorbentien und Katalysatorträger weit verbreitet und gewinnen im aufstrebenden Bereich der Energiespeicherung/erzeugung und für Trennverfahren an wachsender Bedeutung. In der vorliegenden Arbeit wird gezeigt, dass die Kombination aus hydrothermaler Karbonisierung von Zuckern (HTC) mit Templatierungsstrategien einen effizienten Weg zu nanostrukturierten kohlenstoffbasierten Materialien darstellt. HTC ist ein in Wasser und bei niedrigen Temperaturen (130 - 200 °C) durchgeführter Karbonisierungsprozess, bei dem Zucker und deren Derivate einen einfachen Zugang zu hochfunktionalisierten Materialien erlauben. Obwohl diese sauerstoffhaltige Funktionalitäten auf der Oberfläche besitzen, an welche andere chemische Gruppen gebunden werden könnten, was die Verwendung für Trennverfahren und in der verzögerten Wirkstofffreisetzung ermöglichen sollte, ist die mittels HTC hergestellte Kohle für solche Anwendungen nicht porös genug. Das Ziel dieser Arbeit ist es daher, Methoden zu entwickeln, um wohldefinierte Poren in solchen Materialien zu erzeugen. Hierbei führte unter anderem der Einsatz von anorganischen formgebenden mesoporösen Silikapartikeln und makroporösen Aluminiumoxid-Membranen zum Erfolg. Durch Zugabe einer Kohlenstoffquelle (z. B. 2-Furfural), HTC und anschließender Entfernung des Templats konnten poröse kohlenstoffbasierte Partikel und röhrenförmige Nanostrukturen hergestellt werden. Gleichzeitig konnte durch eine zusätzliche Nachbehandlung bei hoher Temperatur (350-750 °C) auch noch die Oberflächenfunktionalität hin zu aromatischen Systemen verschoben werden. Analog zur Formgebung durch anorganische Template konnte mit sog. Soft-Templaten, z. B. PEO-PPO-PEO Blockcopolymeren, eine funktionelle poröse Struktur induziert werden. Hierbei machte man sich die Ausbildung geordneter Mizellen mit der Kohlenstoffquelle D-Fructose zu Nutze. Das erhaltene Material wies hochgeordnete Mikroporen mit einem Durchmesser von ca. 0,9 nm auf. Dieser konnte desweiteren durch Zugabe von Quell-Additiven (z. B. Trimethylbenzol) auf 4 nm in den mesoporösen Bereich vergrößert werden. Zusammenfassend lässt sich sagen, dass beide untersuchten Synthesewege nanostrukturierte kohlenstoffbasierte Materialien mit vielfältiger Oberflächenchemie liefern, und das mittels einer bei relativ niedriger Temperatur in Wasser ablaufenden Reaktion und einer billigen, nachhaltigen Kohlenstoffquelle. Die so hergestellten Produkte eröffnen vielseitige Anwendungsmöglichkeiten, z. B. zur Molekültrennung in der Flüssigchromatographie, in der Energiespeicherung als Anodenmaterial in Li-Ionen Akkus oder Superkondensatoren, oder als Trägermaterial für die gezielte Pharmakotherapie.

L'objectif de ces travaux est l'élaboration de nouveaux matériaux pour la dépollution des sols. Le principe repose sur l'encapsulation de microorganismes ayant des capacités de bioremédiation dans une matrice hybride et macroporeuse. La matrice employée doit à la fois être compatible avec les microorganismes encapsulés et adaptée à l'application visée en termes de structure et de stabilité dans les sols. Le choix des composants employés, mais également les méthodes de mise en forme utilisées ont une influence significative sur ces deux aspects. Les microorganismes choisis (les bactéries Pseudomonas aeruginosa et Shewanella oneidensis) ont été immobilisés dans une matrice hybride, composée de biopolymère (pectine ou alginate) et de silice. La méthode du freeze-casting a été employée simultanément comme méthode d'encapsulation et comme procédé de mise en forme pour l'obtention d'une structure à porosité orientée. La chimie du sol-gel a été utilisée pour recouvrir cette structure par une couche de silice, tout en assurant la survie des organismes encapsulés grâce à des conditions de synthèse douces. Ce travail de thèse a dans un premier temps permis l'identification de paramètres clés à la fois pour la survie des microorganismes et la structure de la matrice. L'influence de la vitesse de congélation et la composition de la matrice (type de biopolymère, présence d'additifs ¿) ont notamment été étudiés afin d'optimiser le taux de survie des bactéries lors de l'encapsulation. Le comportement de ces matériaux a par la suite été évalué dans un sol de référence, tant du point de vue du vieillissement de la matrice que de l'efficacité en termes de dépollution du sol. / The goal of this work is the elaboration of new materials for soil depollution. The principle consists in the encapsulation of microorganisms with bioremediation capabilities in a hybrid porous matrix. Such matrix must be both compatible with the survival of the encapsulated organisms and suitable for the targeted application in terms of structure and in-soil stability. The choice of the components, as well as the processing techniques have a significant influence on these two aspects. The chosen microorganisms (the bacteria Pseudomonas aeruginosa and Shewanella oneidensis) were immobilized within a hybrid matrix, composed of biopolymer (pectin or alginate) as the organic moiety and silica as the inorganic moiety. The freeze-casting technique was used both as a way to encapsulate the microorganisms and to shape the biopolymer into a structure with an oriented porosity. Sol-gel chemistry was used to coat this structure with a silice layer, while ensuring survival of the encapsulated organisms thanks to mild synthetic conditions. This work allowed for the identification of key parameters both regarding the survival of microorganisms toward encapsulation and the final structure of the matrix. The influence of the freezing rate and of the composition of the matrix (type of biopolymer, presence of additives …) have in particular been investigated as a way to optimize bacterial survival rates upon encapsulation. The behavior of the materials was then assessed in a reference soil, from the point of view of the ageing of the matrix, but also regarding the efficiency of the device for soil depollution.

Les céramiques macroporeuses sont largement utilisées dans des applications telles que la filtration, l'isolation thermique, les scaffolds pour la croissance de tissus biologiques, les SOFC, ou encore les OTM. En plus d’une bonne stabilité mécanique, ces céramiques doivent généralement posséder une autre propriété fonctionnelle, comme une perméabilité élevée, une faible conductivité thermique, ou une biocompatibilité. Cependant, la résistance mécanique est généralement augmentée en diminuant le volume total des pores, même si cela peut dégrader d’autres propriétés fonctionnelles. Au-delà de la porosité, des paramètres morphologiques tels que la taille des pores, leur forme ou la tortuosité, peuvent devenir cruciaux pour maximiser les performances, tout en conservant une grande résistance mécanique. Une importante amélioration des propriétés mécaniques peut par exemple être obtenue par des structures anisotropes. Celles-ci renforcent les structures dans la direction de la contrainte principale, de manière similaire aux matériaux naturels tels que l'os trabéculaire, le liège ou le bois. Néanmoins, la plupart des techniques classiquement utilisées pour produire des céramiques macroporeuses ne proposent pas ce niveau de flexibilité. L’ ice-templating est une technique de mise en forme appropriée pour obtenir des matériaux macroporeux anisotropes. Elle est basée sur la congélation de suspensions colloïdales et la séparation ultérieure des particules par le front de solidification. Le solvant congelé est ensuite éliminé, en laissant des pores dont les morphologies sont une réplique des cristaux sublimés. Enfin, le matériau cru est fritté pour consolider la microstructure. Ce processus assure un contrôle indépendant de l'architecture des pores (volume des pores, la taille et la morphologie) à travers la fraction de solides initiale, la vitesse de refroidissement, ou les éventuels additifs. Par conséquent, une bonne compréhension de ces paramètres est essentielle afin d’établir un lien entre les procédés de mise en forme, la microstructure, et les performances de ce type de matériaux et d'étendre leur utilisation dans les applications mentionnées précédemment. L’objectif de ce travail est premièrement, d’adapter l'architecture des pores faits par l’ice-templating pour ensuite, déterminer les principaux paramètres des microstructures qui contrôlent la résistance à la compression, la fiabilité mécanique, et la perméabilité de ces matériaux poreux unidirectionnels. En outre, l'applicabilité des modèles de flux mécanistique et de flux de gaz sera discutée dans le contexte des morphologies de pores structurés. Enfin, nous allons fournir des lignes directrices pour produire des échantillons tubulaires produits par ice-templating. / Macroporous ceramics are widely used in applications such as filtration, thermal insulation, scaffolds for tissue engineering, SOFCs, or OTM’s. They must combine mechanical stability with at least one other functional property such as high permeability, low thermal conductivity, or biocompatibility. However, strength is usually increased by decreasing the total pore volume even though this may degrade the other functional properties. Beyond porosity content, morphological parameters such as pore size, shape, or tortuosity, can become crucial to maximize the performance while maintaining high strength. For example, a significant improvement can be achieved by engineering anisotropic structures to mechanically reinforce the direction of the main stress, similarly to natural materials such as trabecular bone, cork, or wood. Unfortunately, most of the techniques conventionally used to produce macroporous ceramics do not offer this level of flexibility. Ice-templating is a processing technique suitable to obtain anisotropic macroporous materials. It is based on the freezing of colloidal suspensions and the subsequent segregation of particles by the solidification front. After solidification, the frozen solvent is removed, leaving pores whose morphologies are a replica of the sublimated crystals. Finally, the green body is sintered to consolidate the microstructure. This process provides independent control of the pore architecture (pore volume, size, and morphology) through initial solids loading, cooling rate, or additives. Therefore, a good understanding of these parameters is essential to understand the relationship between processing, microstructure, and performance of this type of materials and extend their use in the aforementioned applications.The purpose of this work is first, tailor the pore architecture of specimens processed by ice-templating to then, determine the main microstructural parameters that control the compressive strength, mechanical reliability, and air permeability of unidirectional porous materials. Furthermore, the applicability of mechanistic and gas flow models will be discussed in the context of the structured pore morphologies. Finally, we will provide some guidelines to produce tubular ice-templated samples with controlled porosity.The purpose of this work is first, tailor the pore architecture of specimens processed by ice-templating to then, determine the main microstructural parameters that control the compressive strength, mechanical reliability, and air permeability of unidirectional porous materials. Furthermore, the applicability of mechanistic and gas flow models will be discussed in the context of the structured pore morphologies. Finally, we will provide some guidelines to produce tubular ice-templated samples with controlled porosity.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In many spacecraft receiver applications, the Fast Fourier Transform (FFT) provides a powerful tool for measuring the amplitude and frequency of an unmodulated RF signal. By increasing the FFT acquisition time, tiny signals can be coaxed from the noise and their frequency measured by determining which frequency bin the signal energy appears. The greater the acquisition time, the narrower the bin bandwidth and the more accurate the frequency measurement. In modern satellite operations it is often desirable for the receiver to measure the frequency of a carrier which is modulated with BPSK data. The presence of the BPSK data limits the FFT acquisition time since the signal may switch polarities a number of times while the FFT samples are being acquired. This polarity switching spreads the signal energy into multiple frequency bins making frequency measurement difficult or impossible. The Bit Templating Technique, used for the first time in the CMC Electronics Cincinnati TDRSS / BPSK Spacecraft Receiver, collects the modulated waveform energy back into a signal bin so that accurate amplitude and frequency information can be calculated.