Ce projet concerne la synthèse et caractérisation de nouveaux matériaux composites à base de nanoclusteurs de thiolates d’or Au25(SR)18 (tGNCs), supportés sur divers polymères de coordination (MOFs), ainsi que sur ZrO2. L’activité catalytique de ces matériaux a été évaluée sur la transformation de différents substrats. Les tGNCs sont des matériaux atomiquement bien définis et connus pour être actifs dans des réactions d’oxydation. Les nanoparticules de MOFs sont des matériaux pouvant servir de support pour des tGNCs avec de bonnes dispersions. Certains MOFs sont connus pour avoir des propriétés acides et peuvent être actifs en catalyse. Parmi eux, MIL-101 (Cr), UiO-66 (Zr) et ZIF-8 (Zn) on été choisis en raison de leur propriétés acides et/ou de stabilité thermique. La synergie entre les tGNCs et les MOFs a été évaluée à travers la conversion catalytique de différents substrats tels le glucose, le fructose, l’alcool benzylique et le furfural, impliquant des étapes nécessitant un caractère acide et/ou oxydant. Globalement, il n’a pas été observé d’impact de la présence d’or sur la réactivité de ces substrats, et les tendences catalytiques sont celles obtenues avec les MOFs seuls. Cela est certainement dû à la stabilité thermique non suffisante des MOFs qui prévient une calcination efficace des tNGCs. Lorsque ces clusters sont déposés sur ZrO2, il a été possible de les calciner à différentes températures pour étudier l’effet du ligand et de la taille de particules, pour des réactions d’oxydation en phase liquide. Ainsi, il a été montré par exemple que la température de calcination a un impact significatif sur le comportement catalytique de ces composites, qui ont donné de bonnes activités pour l’oxydation de l’alcool benzylique en benzaldéhyde dans le toluène et en conditions douces, et pour l’esterification oxydante du furfural en furoate de méthyle / This research project reports the synthesis and characterization of new composite materials based on Au25(SR)18 thiolate gold nanoclusters (tGNCs), supported over a range of metal organic frameworks (MOFs), and ZrO2. The synthesized composite materials were tested for catalytic transformations of various substrates. tGNCs are atomically well defined materials known to be active in oxidation reactions. MOFs nanoparticles are materials suitable for high dispersion of tGNCs. Some MOFs are known to have acidity and can be active as catalysts. Among them, MIL-101 (Cr), UiO-66 (Zr) and ZIF-8 (Zn) were chosen due to their acidic and/or thermal stability properties. The synergy between tGNCs and MOFs has been tested through catalytic conversions of different substrates like glucose, fructose, benzylalcohol and furfural, involving steps requiring acidic and oxidative features. Globally, no impact of the presence of Au clusters was observed, and the composite materials showed the same catalytic trends as those obtained with the MOFs alone. This is mainly due to the not sufficient thermal stability of the MOFs that prevents efficient calcination of the tGNCs. In contrast, when deposited on ZrO2 it was possible to calcine Au25(SG)18 nanoclusters at different temperatures to study the ligand and particle size effects in liquid phase oxidation reactions. For example, the calcination temperature had a significant impact on the catalytic behaviour of this composite materials, which showed good activity for the oxidation of benzyl alcohol into benzaldehyde in toluene under mild conditions, and of furfural oxidative esterification into methyl-2-furoate

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Ce travail est dédié à l'étude des mécanismes clés contrôlant l'écoulement linéaire et non-linéaire ainsi que l'état de dispersion des polymères fondus chargés avec des particules submicrométriques. La compréhension fondamentale est ensuite appliquée au procédé de moulage par injection céramique lors duquel un mélange-maître (i.e., une formulation complexe à base de polymères et avec un haut taux de charges de particules de céramique) est injecté dans un moule puis délianté et fritté. Un premier chapitre présente les caractéristiques principales du procédé, l'état de l'art de la compréhension des mécanismes concernés, ainsi que plus généralement, les forces d'interaction en jeu dans les polymères chargés. Ensuite, l'étude se focalise sur le polyéthylène chargé en zircone. Tout d'abord, le rôle de l'interface charge-matrice dans les propriétés rhéologiques et morphologiques est discuté. Il est montré qu'elles sont fortement influencées par la compatibilité de la charge avec la matrice. Une méthode expérimentale est développée pour ajuster la qualité de l'interface. En particulier, l'acide stéarique est déterminé comme étant le surfactant le plus efficace. La cinétique d'hydrophobisation des particules induite par l'estérification est analysée. Par la suite, les mécanismes de dispersion dans les polymères chargés sont explorés. Par exemple, il est conclu que l'acide stéarique et l'extrudeuse à fort cisaillement promeuvent la rupture et l'érosion des agglomérats. Leurs effets sur le comportement rhéologique (i.e., seuil de percolation, contrainte d'écoulement et modulus élastique dynamique) sont discutés. Enfin, la stabilité des polymères chargés, i.e., leur tendence à la floculation et à la ségrégation matrice-charge, est évaluée au repos et à haut taux de cisaillement. Deux méthodes expérimentales sont développées pour cette étude plus appliquée. Le rôle crucial de l'état de dispersion est notamment mis en avant / This work aims to investigate the relevant mechanisms controlling the linear and non-linear flow behaviors and dispersion state of molten polymers filled with submicrometer particles. The fundamental understanding is then applied to the Ceramic Injection Molding process, during which a feedstock (i.e., a complex polymer based formulation, highly filled with ceramic particles) is injected into a mold, debinded and sintered. A first chapter presents the key features of the process, a state of the art of the understanding of the involved mechanisms and more generally the interplaying interaction forces in filled polymers. Then, the study focuses on zirconia filled polyethylene. Firstly, the role of the filler-matrix interface in the rheological and morphological properties is discussed. It is shown that they are strongly influenced by the compatibility of the filler with the matrix. An experimental method is developed to adjust the interface quality. In particular, stearic acid is determined to be the most efficient surfactant. The kinetics of particles hydrophobization induced by the esterification is analyzed. Then, the dispersion mechanisms in filled polymers are explored. For instance, it is concluded that stearic acid and the high shear extruder promote the rupture and erosion of agglomerates. Their effects on the rheological behavior (i.e., percolation threshold, yield stress and dynamic storage modulus) are discussed. Finally, the stability of filled polymers, i.e., tendency to flocculation and filler-matrix segregation, is evaluated at rest and under high shear rates. Two experimental methods are developed for this more applied study. The crucial role of the dispersion state is for instance highlighted

Indiana University-Purdue University Indianapolis (IUPUI) / Thermal barrier coatings (TBCs) have been extensively employed as thermal protection in hot sections of gas turbines in aerospace and power generation applications. However, the fabrication of TBCs still needs to improve for better coating quality, such as achieving coating thickness' uniformity. However, several previous studies on the coating thickness prediction and a systematic understanding of the thickness evolution during the deposition process are still missing. This study aims to develop high-fidelity computational models to predict the coating thickness on complex-shaped components. In this work, two types of models, i.e., ray-tracing based and heat transfer based, are developed. For the ray-tracing model, assuming a line-of-sight coating process and considering the shadow effect, validation studies of coating thickness predictions on different shapes, including plate, disc, cylinder, and three-pin components. For the heat transfer model, a heat source following the Gaussian distribution is applied. It has the analogy of the governing equations of the ray-tracing method, thus generating a temperature distribution similar to the ray intensity distribution in the ray-tracing method, with the advantages of high computational efficiency. Then, using a calibrated conversion process, the ray intensity or the temperature profile are converted to the corresponding coating thickness. After validation studies, both models are applied to simulate the coating thickness in a rotary turbine blade. The results show that the simulated validation cases are in good agreement with either the experimental, analytical, or modeling results in the literature. The turbine blade case shows the coating thickness distributions based on rotating speed and deposition time. In summary, the models can simulate the coating thickness in rotary complex-shaped parts, which can be used to design and optimize the coating deposition process.

The topic of the Ph.D. thesis was focused on the process of sintering alumina and zirconia ceramic materials with the aim to compare kinetics of sintering sub-micro and nanoparticle systems. Zirconia ceramic powders stabilized by different amount of yttria addition in the concentration range of 0 – 8 mol% were used. The different crystal structure (secured by yttria stabilization) of zirconia, as found, did not play statistically proven role in the process of zirconia sintering. The possible influence was covered by other major factors as particle size and green body structure, which does affect sintering in general. According to the Herrings law, the formula predicting sintering temperature of materials with different particle size was defined. The predicted sintering temperatures were in good correlation with the experimental data for zirconia ceramic materials prepared from both, coarser submicrometer, and also nanometer powders. In case of alumina ceramics the predicted and experimentally observed sintering temperature values did not match very well. Mainly the nanoparticle alumina materials real sintering temperature values were markedly higher than predicted. The reason was, as shown in the work, strong agglomeration of the powders and strong irregularities of particle shape. The major role of green body microstructure in the sintering process was confirmed. The final density of ceramic materials was growing in spite of sintering temperature, which was decreasing together with pore - particle size ratio (materials with similar particle size were compared). Sintering temperature was increasing together with growing size of pores trapped in the green body structure. Clear message received from the above mentioned results was the importance of elimination of stable pores with high coordination number out off the green body microstructure during shaping ceramic green parts. Same sintering kinetics model was successfully applied on the sintering process of submicro- and also nanometer zirconia ceramics. Activation energy of nanometer zirconia was notably lower in comparison to submicrometer material. For the sintering of nanoparticle zirconia was typical so called “zero stage” of sintering, clearly visible on kinetic curves. It was found out, that processes running in zirconia “green” material during zero stage of sintering are heat activated and their activation energy was determined. Pores of submicrometer zirconia were growing in an open porosity stage of sintering just a slightly (1.3 times) compared to the nanoparticle zirconia, where the growth was much higher (5.5 times of the initial pore diameter). This difference was most probably caused by preferential sintering of agglomerates within the green bodies and by particle rearrangement processes which appears in the zero stage of sintering of nanoparticular ceramics. The technology of preparation of bulk dense ytria stabilized zirconia nanomaterial with high relative density of 99.6 % t.d. and average grain size 65nm was developed within the thesis research.

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Aim: The aim of the present study was to evaluate how the material KATANA ™ Zirconia YML is affected in strength depending on two different sintering programs. The evaluation of the strength was made by means of a biaxial flexural strength test.   Material and method: A total of 48 test specimens, 32 specimens were produced by KATANA ™ Zirconia YML and 16 specimen cups that formed the control group, by KATANA ™. Zirconia UTML. The specimens were designed as circular disks and were placed in two different layers in the disk, between Enamel-Body 1 and Body 2-Body 3. The specimens were divided into two subgroups of which 24 specimens were quickly sintered and the remaining (n = 24) specimens were conventionally sintered and the strength was evaluated with a biaxial flexural strength test.   Results: The highest mean value for the biaxial flexural strength test was shown by the test group which was high-speed sintered, with placement in Body 2 - Body 3. This was significant in comparison with other groups (p> 0.001) in addition to conventional sintered with the same placement in the disk. Both control groups showed low mean values ​​in comparison with the test groups, control group K (414 MPa) as the lowest in comparison with all other groups. When comparing the two control groups S and K, no significant difference was shown.   Conclusion: The bending strength varies depending on which layers are loaded regardless of fast and conventional sintering. The sintering parameters are significant for the bending strength. / Syfte: Syftet med föreliggande studie var att utvärdera hur materialet KATANA™ Zirconia YML påverkas i hållfasthet beroende av två olika sintringsprogram. Utvärderingen av hållfastheten gjordes med hjälp av ett biaxialt böjhållfasthetstest.   Material och metod: Totalt framställdes 48 provkroppar, 32 stycken framställdes av KATANA™ Zirconia YML och 16 provkoppar som utgjorde kontrollgrupp, av KATANA™. Zirconia UTML. Provkropparna var utformade som cirkulära diskar och dem placerades i två olika skikt i disken, mellan Enamel-Body 1 och Body 2-Body 3. Provkropparna delades in i två undergrupper varav 24 provkroppar snabbsintrades och resterande (n=24) provkroppar sintrades konventionellt och hållfastheten utvärderades med ett biaxialt böjhållfasthetstest.   Resultat: Högst medelvärde för det biaxiala böjhållfasthetstestet uppvisade testgruppen som snabbsintrats, med placering i Body 2 – Body 3. Detta var signifikant i jämförelse med övriga grupper (p > 0,001) förutom konventionellt sintrat med samma placering i disken. Båda kontrollgrupperna uppvisade låga medelvärden i jämförelse med testgrupperna, kontrollgrupp K (414 MPa) som lägst i jämförelse med alla övriga grupper. Vid jämförelse mellan de två kontrollgrupperna S och K uppvisades inte någon signifikant skillnad.   Slutsats: Böjhållfastheten varierar beroende på vilka skikt som belastas oavsett snabb- respektive konventionell sintring. Sintringsparametrarna är betydande för böjhållfastheten.

High speed and/or high efficiency separations can be realized using small particles (~ 1 µm) in liquid chromatography (LC). However, due to the large pressure drop caused by small particles, conventional LC pumping systems cannot satisfy the pressure requirements needed to drive the mobile phase through the column. Use of ultrahigh pressure, elevated temperature, or both can overcome these pressure limitations and allow the use of very small particles for high speed and/or high efficiency separations. In this dissertation, the use of ultrahigh pressures with and without elevated temperatures in capillary LC is described. Very fast separations of various samples on silica-based stationary phases were achieved using optimized equipment and conditions. Great reduction in separation time, while maintaining high efficiency, is the most significant result of this work. Mechanically, chemically and thermally stable new packing materials were required for this research. Polybutadiene encapsulated nonporous zirconia particles, which are chemically and thermally more stable than silica, were evaluated for fast separations of pharmaceuticals and herbicides at temperatures and pressures as high as 100 °C and 30 kpsi, respectively. Safety is a concern when extremely high pressures are used in LC. Column rupture and system component failure can lead to the creation of high speed liquid jets and capillary projectiles. The use of a plexiglass shroud to cover the initial section of the installed capillary column can eliminate any safety-related concerns about these liquid jets or capillary projectiles. An ultrahigh pressure sample injector, with small dwell volume is critical for sample injection and gradient operation at high pressures. A novel injection assembly, composed of six small needle valves, withstood pressures as high as 30 kpsi. A new capillary connector was designed to hold the capillary by “two-point” holding forces under high pressures. With this new injector and capillary connector, gradient elution was easily achieved for the high resolution separation of a protein tryptic digest.

In the study the influence of different dental technical tools on the surface temperature and phase composition of fixed dental prostheses (FDPs) made of yttria-partially stabilized zirconia polycrystals (3Y-/4Y-/5Y-PSZ) was investigated. FDPs were fabricated by using computer-aided manufacturing (CAM). The FDPs were treated with a contra-angle handpiece equipped with different burs and polishers. The resulting surface temperatures were measured with a thermographic camera, and the resulting phase transformations were investigated by X-ray diffraction and quantified by Rietveld refinement. Processing with burs resulted in no phase transformation, but a preferred orientation shift. Using coarse polisher induced a phase transformation to the rhombohedral phase, while fine polishers produced no relevant phase transformations and no preferred orientation shift. Compared to the monoclinic phase (ca. 9% theoretical volume increase), which is associated with low-temperature degradation (LTD), the rhombohedral phase is much more voluminous (ca. 15% theoretical volume increase) and distorted and, therefore, has a greater degradation potential.

The effect of dental technical tools on the phase composition and roughness of 3/4/5 yttria-stabilized tetragonal zirconia polycrystalline (3y-/4y-/5y-TZP) for application in prosthetic dentistry was investigated. Additionally, the X-ray diffraction methods of Garvie-Nicholson and Rietveld were compared in a dental restoration context. Seven plates from two manufacturers, each fabricated from commercially available zirconia (3/4/5 mol%) for application as dental restorative material, were stressed by different dental technical tools used for grinding and polishing, as well as by chewing simulation and thermocycling. All specimens were examined via laser microscopy (surface roughness) and X-ray diffraction (DIN EN ISO 13356 and the Rietveld method). As a result, the monoclinic phase fraction was halved by grinding for the 3y-TZP and transformed entirely into one of the tetragonal phases by polishing/chewing for all specimens. The tetragonal phase t is preferred for an yttria content of 3 mol% and phase t″ for 5 mol%. Mechanical stress, such as polishing or grinding, does not trigger low-temperature degradation (LTD), but it fosters a phase transformation from monoclinic to tetragonal under certain conditions. This may increase the translucency and deteriorate the mechanical properties to some extent.