La finalité de cette étude était la réalisation d’un afficheur électrochrome sur papier activable par un smartphone comme solution anti-contrefaçon. La nature cellulosique du substrat et la faible énergie délivrée par le smartphone ont représenté deux contraintes majeures dans de ce travail de thèse. Ainsi, une nouvelle méthode originale de dépôt à température ambiante de films minces WO3 a été développée en utilisant un traitement UV. Le premier dispositif électrochrome couplant le film WO3 sur papier, le Bleu de Prusse, et une membrane électrolytique plastifiée, a montré une bonne stabilité électrochimique associée à un contraste optique ΔR de 13 % pour une tension d’activation de -1 V. En vue de minimiser la tension d’activation, de nouveaux dispositifs électrochromes, à architecture simplifiée, dérivés d’une configuration classique à 5 couches ont été mis au point. Le remplacement du matériau de contre électrode et du conducteur électronique par un matériau métallique unique a conduit à des dispositifs à 4 couches. De plus, l’utilisation d’un matériau électrochrome conducteur a permis de s’affranchir de la couche conductrice électronique adjacente à l’électrode de travail menant à des dispositifs encore plus simplifiés à 3 couches. Les dispositifs simplifiés se caractérisent par des performances électrochromes très intéressantes pour une activation à seulement -0,7 V et présentent une stabilité électrochimique sur plus de 500 cycles. Le premier prototype sur emballage de parfum, à base d’afficheur électrochrome constitué de PEDOT, d’électrolyte liquide ionique polymérisé par vernis UV, et de contre électrode d’Ag, a été activé avec succès par un smartphone en moins de 5,3 secondes pour une énergie d’activation de 0,33 mJ.cm-2. / This study aims at the development of an electrochromic display on paper, activated by a smartphone as solution for counterfeit. A novel deposition method at room temperature of WO3 thin films was developed using a UV treatment. 5-layer electrochromic device (ECD), based on WO3 on paper, Prussian blue, and an electrolyte membrane, showed good electrochemical stability for more than 500 cycles associated with an optical contrast in reflectance ΔR of 13% at -1 V. In order to minimize the activation potential, ECDs with simplified architecture, derived from 5-layer conventional configuration have been developed in a second part of this work. 4-layer ECDs were constructed by replacing the counter-electrode and conductive layer by a single metal layer. In addition, the use of an electrochromic conducting material leads to 3-layer device. 4 and 3-layer ECDs exhibit high electrochromic performances at only -0.7 V with nice stability for more than 500 cycles. The first prototype integrated on perfume packaging, with 4-layer ECD based on PEDOT (poly(3,4-ethylenedioxythiophene), ionic liquid electrolyte polymerized by UV-varnish, and Ag as counter-electrode was successfully activated by a smartphone in less than 5.3 seconds for an activation energy of 0.33 mJ.cm-2.

In dieser Studie wurde das Verhalten eines neuentwickelten Hartmetallfinierers der Firma Brasseler und herkömmlicher grober und feiner Diamantfinierer der Firmen Intensiv und Brasseler an vier verschiedenen Füllungsmaterialien untersucht. Bei dem Hartmetallfinierer handelt es sich um ein Kombinationsinstrument, das sich im Rechtslauf durch eine hohe Arbeitsleistung auszeichnet und zum Konturieren von Füllungen gedacht ist. Im Linkslauf soll das Instrument zur Feinausarbeitung eingesetzt werden, die Arbeitsleistung ist geringer. In 120 extrahierte menschliche Zähne wurden ovale Klasse-V-Kavitäten (Länge: 4 mm, Breite: 3 mm, Tiefe: 2 mm) präpariert, die jeweils zur Hälfte im Schmelz und Dentin lagen. Jeweils 30 Zähne wurden nach Herstellerangaben mit demselben Füllungsmaterial gefüllt (Prodigy, Silux Plus, Dyract AP, Fuji LC). Anschließend wurden die Restaurationen zunächst mit den gröberen Finierdiamanten und dem Kombifinierer im Rechtslauf konturiert. Jeweils 10 Proben eines jeden Füllungsmaterials wurden mit einem der Instrumente bearbeitet. Auf diese Weise ergaben sich 12 Material-Instrumenten-Kombinationen. Nach dreiwöchiger Wasserlagerung wurde die Rauhigkeit der Füllungsoberflächen mit einem Profilometer gemessen. Außerdem erfolgte eine Auswertung der Randqualität mittels quantitativer Randanalyse. Im Anschluß hieran wurden die Füllungen mit den feineren Diamantinstrumenten bzw. dem Kombifinierer im Linkslauf finiert. Die Füllungen wurden anschließend einer Temperaturwechselbelastung unterzogen (2000 Zyklen zwischen 5°C und 55°C). Erneut erfolgte eine quantitative Randanalyse und eine Oberflächenrauhigkeitsmessung. Die statistische Auswertung der Daten ergab, daß der Kombifinierer im Linkslauf im Gegensatz zu den feinen Diamantfinierern keine Verbesserung der Oberflächenqualität bewirkt. Die Auswirkungen der Instrumente auf die Randqualität ist gleich. Fuji LC weist die höchste Oberflächenrauhigkeit auf. Die übrigen Füllungsmaterialien unterscheiden sich diesbezüglich nicht statistisch signifikant voneinander. Die Silux Plus Restaurationen zeichnen sich durch einen im Vergleich zu den übrigen Materialien hohen Anteil an Randspalten sowohl im Dentin- als auch im Schmelzbereich aus. Die Prodigy Füllungen haben signifikant mehr Randspalten im Dentin als Fuji LC und Dyract AP Füllungen, jedoch auch signifikant weniger als Silux Plus im gleichen Bereich. / In this study a newly developed tungsten carbide finishing bur (Brasseler) and conventional coarse and fine grit finishing diamonds of the companies Intensiv and Brasseler were studied with four different filling-materials. The carbide bur is a combination-instrument, that distinguishes itself in the right-hand rotation by a high performance and is intended for the contouring of fillings. When used in a left-hand rotation the instrument should be applied for polishing. In this case the cutting performance is inferior. Oval class-V-cavities (length: 4 mm, width: 3 mm, depth: 2 mm) were prepared into 120 extracted human teeth with one half of the margin length in dentin and one half in enamel. In each case, 30 teeth were filled according to manufacturer-recommendation with the same filling-material (Prodigy, Silux Plus, Dyract AP, Fuji LC). Subsequently the restorations were trimmed with the coarser finishing diamonds and the combination bur with a right-hand rotation. Ten samples of each filling-material were ground with one of the instruments. Thus 12 material-instrument-combinations were established. After three weeks of water-storage, the surface roughness of the fillings was measured with a profilometer. Furthermore, an evaluation of the margin-quality was carried out by means of quantitative margin analysis. After this, the fillings were either polished with the finer diamond-instruments or with the combination-instrument in a left-hand rotation. Afterwards the samples were subjected to a thermocycling procedure (2000 cycles between 5°C and 55°C). Again a quantitative margin analysis and a surface-roughness-measurement were performed. In contrast to the fine diamond instruments, the statistical evaluation of the data revealed that the combination finishing bur does not improve the surface quality in a left-hand rotation. The effect of the instruments on the margin quality is the same. Fuji LC shows the highest surface-roughness, the other filling-materials do not differ statistically significantly from one another. The Silux Plus restorations are characterized by a high percentage of marginal openings in both enamel and dentin. The Prodigy fillings show significantly more marginal gaps in dentin than Fuji LC and Dyract AP fillings, but significantly less than Silux Plus in the same area.

The initial stage of liquid phase sintering, involving liquid penetration, agglomerate separation, particle spreading and growth has been investigated in experiments using tungsten heavy alloys. The particle composites used were produced by hot isostatic pressing (HIP) of pure powder mixtures of W-Ni-Fe-(Co). By using different HIP temperatures, volume fractions of tungsten, alloying elements like Cobalt and Sulphur or excluding Iron from the matrix, liquid penetration, agglomerate separation and particle growth conditions were affected. The investigations were performed mainly under microgravity (sounding rockets or parabolic trajectories by airplanes) but at high tungsten particle fractions, short sintering times or at infiltration of solid pure tungsten, they were performed at normal gravity. The liquid penetration of the tungsten agglomerates is explained by initial wetting under non-equilibrium conditions, due to the reaction between the liquid matrix and the particles, and a decrease of interfacial energy. The dissolving of tungsten gives a pressure drop in the penetrating liquid and a driving force for the liquid movement by a suggested parabolic penetration model. For cold worked tungsten, a penetration theory was proposed, where an internal stress release in the penetrated tungsten grains creates space for the advancing liquid. The spreading of the tungsten agglomerates is explained by an interagglomerate melt swelling due to a Kirkendall effect. The liquid matrix undergoes a volume increase since the diffusion rates of Ni-Fe are higher than for W and initial concentration gradients of W and Ni, Fe exists. The suggested model by Kirkendall are also used for an analysis of the interaction behaviour between solid particles and a solidification front and inclusion behaviour in iron base alloys during teeming and deoxidation. The average tungsten particles size decrease initially since part of the tungsten particles is dissolved when the non-equilibrium matrix phase is melting. When equilibrium is reached, the tungsten particles grow in accordance with the Ostwald ripening process by an approximately 1/3 power law. Larger particle fraction of particles showed a higher growth rate, due to shorter diffusion distances between the particles. Cobalt, Sulphur and absence of iron in the matrix were found to increase the growth rate of the tungsten particles due to a higher surface tension between the solid tungsten particles and the matrix melt. / QC 20100528

A parallel finite element code with adaptive meshing was developed and used to study three dimensional, time-dependent fluid flows caused by thermocapillary convection as well as temperature and dopant distribution in fusion welding and floating zone crystal growth. A comprehensive numerical model of the three dimensional time-dependent fluid flows in a weld pool had been developed. This model considered most of the physical mechanisms involved in gas tungsten arc welding. The model helped obtaining the actual chaotic time-dependent melt flow. It was found that the fluid flow in the weld pool was highly complex and influenced the weld pool’s depth and width. The physicochemical model had also been studied and applied numerically in order to simulate the surfactant adsorption onto the surface effect to the surface tension of the metal liquid in a weld pool. Another model, a three dimensional time-dependent, with adaptive mesh refinement and coarsening was applied for simulating the effect of weak flow on the radial segregation in floating zone crystal growth. The phase change equation was also included in this model in order to simulate the real interface shape of floating zone. In the new parallel code, a scheme that keeps the level of node and face instead of the complete history of refinements was utilized to facilitate derefinement. The information was now local and the exchange of information between each and every processor during the derefinement process was minimized. This scheme helped to improve the efficiency of the parallel adaptive solver. / QC 20100527

The Quantum chemical cluster approach has been shown to be quite powerful and efficient in the modeling of enzyme active sites and reaction mechanisms. In this thesis, the reaction mechanisms of several enzymes have been investigated using the hybrid density functional B3LYP. The enzymes studied include four dinuclear zinc enzymes, namely dihydroorotase, N-acyl-homoserine lactone hydrolase, RNase Z, and human renal dipeptidase, two trinuclear zinc enzymes, namely phospholipase C and nuclease P1, two tungstoenzymes, namely formaldehyde ferredoxin oxidoreductase and acetylene hydratase, aspartate α-decarboxylase, and mycolic acid cyclopropane synthase. The potential energy profiles for various mechanistic scenarios have been calculated and analyzed. The role of the metal ions as well as important active site residues has been discussed.   In the cluster approach, the effects of the parts of the enzyme that are not explicitly included in the model are taken into account using implicit solvation methods.   For all six zinc-dependent enzymes studied, the di-zinc bridging hydroxide has been shown to be capable of performing nucleophilic attack on the substrate. In addition, one, two, or even all three zinc ions participate in the stabilization of the negative charge in the transition states and intermediates, thereby lowering the barriers.   For the two tungstoenzymes, several different mechanistic scenarios have been considered to identify the energetically most feasible one. For both enzymes, new mechanisms are proposed.   Finally, the mechanism of mycolic acid cyclopropane synthase has been shown to be a direct methyl transfer to the substrate double bond, followed by proton transfer to the bicarbonate.   From the studies of these enzymes, we demonstrate that density functional calculations are able to solve mechanistic problems related to enzymatic reactions, and a wealth of new insight can be obtained.

This thesis summarizes the methods and major findings of Ni-W(P)/ã-Al2O3 nitride cata-lyst synthesis, characterization, hydrotreating activity, kinetic analysis and correlation of the catalysts activities to their synthesis parameters and properties.<p> The range of parameters for catalyst synthesis were W (15-40 wt%), Ni (0-8 wt%), P (0-5 wt%) and nitriding temperature (TN) (500-900 °C). Characterization techniques used included: N2 sorption studies, chemisorption, elemental analysis, temperature programmed studies, x-ray diffraction, scanning electron microscopy, energy dispersive x-ray, infrared spectroscopy, trans-mission electron microscopy and x-ray absorption near edge structure. Hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatization (HDA) were performed at: tem-perature (340-380 °C), pressure (6.2-9.0 MPa), liquid hourly space velocity (1-3 h-1) and hydro-gen to oil ratio (600 ml/ml, STP).<p> The predominant species on the catalyst surface were Ni3N, W2N and bimetallic Ni2W3N. The bimetallic Ni-W nitride species was more active than the individual activities of the Ni3N and W2N. P increased weak acid sites while nitriding temperature decreased amount of strong acid sites. Low nitriding temperature enhanced dispersion of metal particles. P interacted with Al2O3 which increased the dispersion of metal nitrides on the catalyst surface. HDN activity in-creased with Ni and P loading but decreased with increase in nitriding temperature (optimum conversion; 60 wt%). HDS and HDA activities went through a maximum with increase in the synthesis parameters (optimum conversions; 88. wt% for HDS and 47 wt% for HDA). Increase in W loading led to increase in catalyst activity. The catalysts were stable to deactivation and had the nitride structure conserved during hydrotreating in the presence of hydrogen sulfide.<p> The results showed good correlation between hydrotreating activities (HDS and HDN) and the catalyst nitrogen content, number of exposed active sites, catalyst particle size and BET surface area.<p> HDS and HDN kinetic analyses, using Langmuir-Hinshelwood models, gave activation energies of 66 and 32 kJ/mol, respectively. There were no diffusion limitations in the reaction process. Two active sites were involved in HDS reaction while one site was used for HDN. HDS and HDN activities of the Ni-W(P)/ã-Al2O3 nitride catalysts were comparable to the corre-sponding sulfides.

This thesis summarizes the methods and major findings of Ni-W(P)/ã-Al2O3 nitride cata-lyst synthesis, characterization, hydrotreating activity, kinetic analysis and correlation of the catalysts activities to their synthesis parameters and properties.<p> The range of parameters for catalyst synthesis were W (15-40 wt%), Ni (0-8 wt%), P (0-5 wt%) and nitriding temperature (TN) (500-900 °C). Characterization techniques used included: N2 sorption studies, chemisorption, elemental analysis, temperature programmed studies, x-ray diffraction, scanning electron microscopy, energy dispersive x-ray, infrared spectroscopy, trans-mission electron microscopy and x-ray absorption near edge structure. Hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatization (HDA) were performed at: tem-perature (340-380 °C), pressure (6.2-9.0 MPa), liquid hourly space velocity (1-3 h-1) and hydro-gen to oil ratio (600 ml/ml, STP).<p> The predominant species on the catalyst surface were Ni3N, W2N and bimetallic Ni2W3N. The bimetallic Ni-W nitride species was more active than the individual activities of the Ni3N and W2N. P increased weak acid sites while nitriding temperature decreased amount of strong acid sites. Low nitriding temperature enhanced dispersion of metal particles. P interacted with Al2O3 which increased the dispersion of metal nitrides on the catalyst surface. HDN activity in-creased with Ni and P loading but decreased with increase in nitriding temperature (optimum conversion; 60 wt%). HDS and HDA activities went through a maximum with increase in the synthesis parameters (optimum conversions; 88. wt% for HDS and 47 wt% for HDA). Increase in W loading led to increase in catalyst activity. The catalysts were stable to deactivation and had the nitride structure conserved during hydrotreating in the presence of hydrogen sulfide.<p> The results showed good correlation between hydrotreating activities (HDS and HDN) and the catalyst nitrogen content, number of exposed active sites, catalyst particle size and BET surface area.<p> HDS and HDN kinetic analyses, using Langmuir-Hinshelwood models, gave activation energies of 66 and 32 kJ/mol, respectively. There were no diffusion limitations in the reaction process. Two active sites were involved in HDS reaction while one site was used for HDN. HDS and HDN activities of the Ni-W(P)/ã-Al2O3 nitride catalysts were comparable to the corre-sponding sulfides.

Übergangsmetalloxidbronzen (TMOB) – Verbindungen mit der allgemeinen chemischen Summenformel AxByOz (A = Element der Gruppen 1, 2, 11, 12, 13, NH4+ oder Kombination; B = Übergangsmetall) – sind seit längerem als Material für ionensensitive Festkörperelektroden bekannt. Sie reagieren als Elektroden in elektrochemischen Messungen auf Ionen in wässrigen Elektrolyten in höchst unterschiedlicher Weise. Bis heute gibt es dazu nur wenige systematische vergleichende Untersuchungen, die von der Präparation der Bronzen, der Charakterisierung ihrer Eigenschaften bis zur Untersuchung ihrer Elektrodeneigenschaften reichen. Gegenstand der Arbeit war deshalb die Synthese von in der Literatur beschriebenen TMOB auf der Basis von Wolfram und Molybdän, die Bestimmung ihrer Kristallstruktur und die Untersuchung ihrer chemischen und physikalischen Eigenschaften. Aus den synthetisierten Verbindungen waren anhand einer elektrochemischen Vorcharakterisierung einige auszuwählen, um diese systematisch als Elektroden zu untersuchen. Insbesondere HxMoO3, Ba0,12WO3 und Li0,4Mo0,95W0,05O3 zeichneten sich durch gegenüber den anderen Oxidbronzen abweichende potentiometrische Charakteristika aus. Hinsichtlich der Einsetzbarkeit dieser Materialien für potentiometrische Elektroden wurden diese Verbin¬dungen noch nicht untersucht. Daher wurden diese Verbindungen eingehender erforscht. Die bezüglich ihrer potentiometrischen Eigen¬schaften bereits ausreichend untersuchte Verbindung Na0,9Mo6O17 diente dem Vergleich und wurde deshalb den selben Tests ausgesetzt. Dazu waren im Einzelnen potentiometrische Messungen in Abhängigkeit von der Konzentration der Alkaliionen und der Wasserstoffionen sowie von der Konzentration verschiedener Redoxspezies in wässrigen Medien durchzuführen. Unklar war bisher wie sich die Wechselwirkungen der gelösten Ionen mit den Molybdän- und Wolframionen im Festkörper vollziehen und warum die Elektroden Sensitivitäten für verschiedene Ionen aufweisen, die sich nicht aus der chemischen Zusammensetzung oder mit der Kristallstruktur der jeweiligen Oxidbronze erklären lassen. Zur Aufhellung dieses Problems waren unter anderem XPS-Untersuchungen an verschiedenen Oxidbronzen durchzuführen, aus denen man auf den Oxidationszustand des Wolframs und Molybdäns im Festkörper schließen kann.

Although current trends in global warming are of great concern, energy demand is still increasing, resulting in increasing pollutant emissions. To address this issue, we need reliable renewable energy sources, lowered pollutant emissions, and efficient and profitable processes for energy conversion. We also need to improve the use of the energy, produced by existing infrastructure. Consequently, the work presented in this thesis aims at investigating current scientific and technological challenges in energy conversion through biomass gasification and the alternative use of fossil fuels, such as diesel, in the generation of cleaner electricity through auxiliary power units in the transport sector. Production of chemicals, syngas, and renewable fuels is highly dependent on the development and innovation of catalytic processes within these applications. This thesis focuses on the development and optimization of catalytic technologies in these areas. One of the limitations in the commercialization of the biomass gasification technology is the effective catalytic conversion of tars, formed during gasification. Biomass contains high amounts of alkali impurities, which pass on to the producer gas. Therefore, a new material with alkali tolerance is needed. In the scope of this thesis, a new catalyst support, KxWO3 – ZrO2 with high alkali resistance was developed. The dynamic capability of KxWO3 – ZrO2 to store alkali metals in the crystal structure, enhances the capture of alkali metals "in situ". Alkali metals are also important electronic promoters for the active phase, which usually increases the catalysts activity and selectivity for certain products. Experimental results show that conversion of 1-methylnaphathalene over Ni/KxWO3 – ZrO2 increases in the presence of 2 ppm of gas-phase K (Paper I). This support is considered to contribute to the electronic equilibrium within the metal/support interface, when certain amounts of alkali metals are present. The potential use of this support can be extended to applications in which alkali "storage-release" properties are required, i.e. processes with high alkali content in the process flow, to enhance catalyst lifetime and regeneration. In addition, fundamental studies to understand the adsorption geometry of naphthalene with increasing temperature were performed in a single crystal of Ni(111) by STM analyses. Chapter 9 presents preliminary studies on the adsorption geometry of the molecule, as well as DFT calculations of the adsorption energy. In relation to the use of clean energy for transport applications, hydrogen generation through ATR for FC-APUs is presented in Papers II to V. Two promoted RhPt bimetallic catalysts were selected in a previous bench scale study, supported on La2O3:CeO2/d – Al2O3 and MgO : Y2O3/CeO2 – ZrO2. Catalyst evaluation was performed in a fullscale reformer under real operating conditions. Results showed increased catalyst activity after the second monolithic catalyst due to the effect of steam reforming, WGS reaction, and higher catalyst reducibility of the RhxOy species in the CeO2 – ZrO2 mixed oxide, as a result of the improved redox properties. The influence of sulfur and coke formation on diesel reforming was assessed after 40 h on stream. Sulfur poisoning was evaluated for the intrinsic activity related to the total Rh and Pt area observed after exposure to sulfur. Sulfur concentration in the aged catalyst washcoat was observed to decrease in the axial direction of the reformer. Estimations of the amount of sulfur adsorbed were found to be below the theoretical equilibrated coverage on Rh and Pt, thus showing a partial deactivation due to sulfur poisoning. / <p>QC 20150213</p>

For sustainable development, it is highly important to limit the loss of energy and materials in machines used for transportation, manufacturing, and other purposes. Large improvements can be achieved by reducing friction and wear in machine elements, for example by the application of coatings. This work is focused on triboactive coatings, for which the outermost layer changes in tribological contacts to form so-called tribofilms. The coatings are deposited by magnetron sputtering (a physical vapor deposition method) and thoroughly chemically and structurally characterized, often theoretically modelled, and tribologically evaluated, to study the connection between the composition, structure and tribological performance of the coatings. Tungsten disulfide, WS2, is a layered material with the possibility of ultra-low friction. This work presents a number of nanocomposite or amorphous coatings based on WS2, which combine the low friction with improved mechanical properties. Addition of N can give amorphous coatings consisting of a network of W, S and N with N2 molecules in nanometer-sized pockets, or lead to the formation of a metastable cubic tungsten nitride. Co-deposition with C can also give amorphous coatings, or nanocomposites with WSx grains in an amorphous C-based matrix. Further increase in coating hardness is achieved by adding both C and Ti, forming titanium carbide. All the WS2-based materials can provide very low friction (down to µ&lt;0.02) by the formation of WS2 tribofilms, but the performance is dependent on the atmosphere as O2 and H2O can be detrimental to the tribofilm functionality. Another possibility is to form low-friction tribofilms by tribochemical reactions between the two surfaces in contact. Addition of S to TiC/a-C nanocomposite coatings leads to the formation of a metastable S-doped carbide phase, TiCxSy, from which S can be released. This enables the formation of low-friction WS2 tribofilms when a Ti-C-S coating is run against a W counter-surface. Reduced friction, at a moderate level, also occurs for steel counter-surfaces, likely due to formation of beneficial iron sulfide tribofilms. The studied coatings, whether based on WS2 or TiC, are thus triboactive, with the ability to form low-friction tribofilms in a sliding contact.