Hydrering är en viktig process för att producera produkter med önskade egenskaper samt att uppfylla de lagliga krav som existerar med avseende på miljö och hälsa. Reaktionerna som sker vid hydreringen är katalytiska vilket innebär att förstå sam utnyttja de mest lämpliga katalysatorerna är av yttersta vikt. Avsvavling (HDS) är en av de mest studerade reaktionerna medan avaromatisering (HDA) samt borttagandet av kväve (HDN) är diskuterade samt förstådda i lägre grad. Trots det är aromatiska samt kväverika föreningar naturligt förekommande i matningar till hydreringsreaktorerna där de organiska kväveföreningarna är inhibitorer. I detta arbete är målet att tillverka samt utvärdera några hydreringskatalysatorer med fokus på deras prestanda för HDA och HDN reaktionerna. Den bästa möjliga tekniken idag för tillverkningen av hydreringskatalysatorer utnyttjar kelateringsreagens vid beredningen. Detta har visat sig ha en positiv inverkan på egenskaperna och aktivteten vid hydrering för NiMo-katalysatorer. För att undersöka detta närmare har två typer av katalysatorer tillverkats, en med kelateringsreagens (typ II) och en utan (typ I). Dessa var sedan utvärderade i dess HDA och HDN aktiveter. Katalysatorerna var tillverkade samt karaktäriserade vid KTH och sedan aktiverade via sulfidering samt utvärderade vid Nynas AB. Aktiviteten för de sulfiderade katalysatorerna var utvärderade i ett surrogatsystem bestående av fenantren (PHE) som modell för aromatiska föreningar samt karbazol (CBZ) eller akridin (ACR) som modell för icke-basiskt samt basiskt organisk-kväve. Aktivitetsutvärderingen utfördes i en porlbäddreaktor där aktiviteten undersöktes vid närvarandet samt avsaknandet av de organiska kväveföreningarna. När matningen byttes, en så kallad modeswitch, ändras aktiviteten beroende på de betingelser som undersöktes. Reaktortemperaturen varierade mellan 300 °C och 320 °C vid ett konstant systemtryck på 120 barg. Katalysatornsaktivitet var positivt korrelerad med reaktortemperaturen där en lägre aktivtetuppmättes vid 300 °C jämfört med 320 °C. Det visade sig även att båda typerna av organiskt kväve påverkade aktivteten negativt vid båda undersökta temperaturerna. Utöver det så var de basiska kväveföreningarna mer inhiberande jämfört med de icke-basiska föreningarna för båda katalysatorerna. Inhiberingen orsakad av karbazol visade sig vara helt reversibel medan akridininhiberingen antydde på mer permanenta effekter för typ II katalsatorn. Dessa resultat antyder, trots de preliminära antagandena, att typ I katalysatorn var bättre än typ II katalysatorn. / Hydrotreating processes are of high importance in helping to obtain the desired characteristics of products as well as to comply with the legislation regarding health hazards and environmental pollution. Hydrotreating reactions are catalytic reactions which imply that the understanding and utilization of the most suitable catalysts is crucial. While hydrodesulfurization is a vastly studied branch of hydrotreating, hydrodearomatization (HDA), and hydrodenitrogenation (HDN) processes are less discussed and understood. However, aromatic compounds along with nitrogen-containing inhibitors are naturally present in the hydrotreater feeds. Therefore, the aim of this study was the preparation and evaluation of hydrotreating catalysts with the main focus on HDA and HDN reactions. According to the current state of the art, the utilization of chelating agents during preparation has a positive impact on the characteristics and activity of hydrotreating catalysts therefore NiMo catalysts with (Type II) and without (Type I) a chelating agent were prepared and evaluated towards HDA and HDN reactions. The catalysts were prepared and characterized at KTH and then activated (sulfided) and evaluated at Nynas AB. The activity of the sulfided catalysts was evaluated using surrogate mixture models containing phenanthrene (PHE) as an aromatic compound, and carbazole (CBZ) or acridine (ACR). The latter ones were representing two types of nitrogen-containing inhibitors, non-basic and basic. The activity testing was carried out in a trickle-bed microreactor during three-step experiments in the presence and absence of the organic nitrogen compounds (mode switches). During the mode switches the activity of the catalysts under varying conditions was investigated. The operating temperature of the reactor varied between 300 and 320°C under constant H2 pressure of 120 barg. The catalytic activity was positively correlated with temperature with the catalysts exhibiting lower activities at 300°C than at 320°C. It is noteworthy that the activity of all the catalysts was hindered by the presence of both nitrogen compounds at all temperatures with the basic nitrogen (ACR) being more inhibitory for both catalysts. CBZ inhibition to the HDA reactions showed reversibility, while ACR had a more permanent inhibiting effect in the case of the Type II catalyst. The results indicated that despite the preliminary assumptions, the Type I catalyst outperformed the Type II.

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[pt] Os ciclos termoquímicos de decomposição de água relacionados ao enxofre são uma importante classe de processos químicos considerados para a produção de hidrogênio. Recentemente, a decomposição térmica do sulfato de magnésio e sulfato de amônio tem sido relatada como uma potencial operação unitária em um desses ciclos. Portanto, algum interesse tem sido observado no uso de catalisadores para diminuir a energia de ativação de sulfatos que se decompõem em altas temperaturas, como o magnésio e a adição de um agente modificador para facilitar a separação dos produtos no caso de sulfatos que se decompõem em baixas temperaturas como amônio. Neste contexto, a presente tese relata os resultados da modelagem termodinâmica e cinética associada a este sistema de reação na presença de Pd suportado sobre gama-Al(2)O(3). Para o sistema Mg a presença de tais espécies é responsável por deslocar a temperatura de decomposição para valores mais baixos em pelo menos 100 graus C. Observou-se que o teor de magnésio ainda está orientado para a formação de MgO. Os resultados obtidos indicam que o catalisador Pd/Al(2)O(3) pode ser uma boa alternativa na redução da temperatura de decomposição térmica, pois sua presença foi responsável por diminuir a energia de ativação do processo de 368,2 para 258,8 kJ.mol(-1). Para o sistema NH4 pode-se observar que ocorre em quatro etapas e a formação de sulfato de alumínio, sendo a última espécie portadora de sulfato, proporciona a separação do óxido de enxofre liberando-o em uma etapa diferente dos demais produtos gasosos. A presença de paládio pode atuar como redutor da energia de ativação desta etapa, deslocando a temperatura de decomposição para valores inferiores em pelo menos 90 graus C e a reduzindo os valores de energia de ativação entre 12 – 30 por cento abaixo do encontrado na literatura oriundos de modelos gráficos. / [en] The sulfur related thermochemical water-splitting cycles are an important class of chemical processes considered for hydrogen production. Recently, the magnesium and the ammonium sulfate thermal decomposition have been reported as a potential unit operation in one of these cycles. Therefore, some interest has been observed in the use of catalysts to lower the activation energy for sulfates that decompose in high temperatures, as such magnesium and the addition of a modifying agent to facilitate separation of the products in the case of sulfates that decompose into low temperatures as ammonium. In this context, the present thesis reports the thermodynamics and kinetics modeling results associated with this reactions systems in the presence of a Pd supported over gamma-Al(2)O(3). For Mg system the presence of such species is responsible for shifting the decomposition temperature to lower values in at least 100 degrees C. It was observed that the magnesium content is still oriented towards MgO formation. The obtained results indicate that the Pd/Al(2)O(3) catalyst could be a good alternative in reducing the thermal decomposition temperature as its presence was responsible for diminishing the process activation energy from 368.2 to 258.8 kJ.mol(-1). For NH(4) system it can be observed four steps for reactions and formation of aluminum sulfate, as the last sulfate bearing species, provided the separation of the sulfur oxide releasing it in a different step from the other gaseous products. The presence of palladium can act as an activation energy reducer, shifting the decomposition temperature to lower values in at least 90 degrees C and decreasing the activation energy by 12 – 30 percent than that found in the literature.

In this thesis Cu(In,Ga)Se2 (CIGS) solar cells with different sodiumdoping of the CIGS absorber and varying Al2O3 rear surface passivationlayer thickness have been manufactured and electrically characterised. Baseline samples and samples without passivation were used asreferences for the passivated samples. For the passivated samplesbetween 1 and 7 nm of Al2O3 were deposited by ALD. The electricalcharacterisation included current-voltage (IV, JV), quantum efficiency (QE, EQE), capacitance-voltage (CV) and temperature dependent currentvoltage (IVT, JVT) measurements. The results show that it is indeed possible to use a tunnel current toconstruct an electrical contact, but that the electrical contact isvery sensitive to sodium doping. The samples with post-depositiontreatment and without Na start to block the tunnel current when thepassivation layer reaches a thickness of about 2 nm, while no blocking of the tunnel current could be observed for the samples with Na pre-deposition. The samples with pre-deposition treatment showed acontinued increase in efficiency all the way to a passivation layerthickness of about 7 nm. When trying to construct samples with eventhicker passivation layer the CIGS started to peel off. For thisreason the optimal thickness for the pre-deposition treated samplescould not be found. The samples with the highest efficiency was thesamples with pre-deposition treatment and thick passivation layer. Those samples showed an increase of 3 percent (absolute) compared tothe unpassivated sample with the same deposition treatment and 1.6 percent higher efficiency compared to the baseline sample. Concluding that tunnelling passivation layer is comparable to the passivationlayer with point contact methods.

Une solution au problème astrophysique de la matière sombre pourrait être apportée par la détection de WIMPs, particules prédites par la supersymétrie. Sa détection directe nécessite de grandes masses de détecteurs capables d'identifier le signal d'un WIMP parmi le fond radioactif et cosmique environnant. Cette thèse se déroule dans le cadre de l'expérience EDELWEISS et la future expérience EURECA qui lui succédera. Ces expériences utilisent une technologie basée sur des détecteurs cryogéniques (bolomètres) à double voies, fonctionnant à quelques dizaines de mK. Ils sont constitués de cristaux qui sont le siège des interactions des particules, dont les dépôts d'énergie vont entraîner une élévation de température ainsi que l'ionisation du cristal, pouvant entraîner des charges ou des photons selon sa nature. Afin d'augmenter la palette de cibles pouvant faire office de bolomètres scintillants, nous avons mis en place un dispositif expérimental permettant d'étudier la scintillation de cristaux refroidis jusqu'à 3 K. Il est basé sur un cryostat à géométrie optique compacte permettant une collecte de lumière améliorée. Une méthode de comptage de photons individuels ainsi qu'un traitement statistique des données permettent de mesurer l'évolution du rendement lumineux et des constantes de temps de scintillation de cristaux entre la température ambiante et 3K. Cette thèse présente ainsi les résultats obtenus à 3 K avec ce dispositif expérimental sur deux cristaux, bien connus à température ambiante: le BGO (Bi4Ge3O12) et le BaF2. Nous présentons également les résultats sur la luminescence du saphir dopé au titane (Ti:Al2O3), sous VUV et refroidi à 8 K. / A solution to the dark matter problem in astrophysics could be found by the detection of WIMPs, particles predicted by supersymmetry. Its direct detection requires a large mass of detectors, able to identify WIMPs in the background of natural radioactivity and cosmic rays. This thesis takes place within the framework of the EDELWEISS and the future EURECA experiments. These experiments use a technology based on two channel cryogenic detectors (bolometers), working at a few tens of mK. They are made of crystals in which the energy deposited by particle interactions will produce a temperature increase (phonon signal), and where the ionization of the crystals results in either a charge or photon signal, depending on their nature. In order to broaden the range of targets for scintillating bolometers, we have built a setup to study the scintillation of crystals cooled down to 3 K. It is based on a cryostat with a compact optical geometry allowing enhanced light collection. Thanks to an individual photon counting technique and a statistical treatment of data, it allows us to measure the evolution of the the light yields and the decay time components between room temperature and 3 K. Thus this thesis presents the results obtained at 3 K on two well known room temperature crystals: BGO (Bi4Ge3O12) and BaF2. We also study the luminescence properties of titanium sapphire (Ti:Al2O3), under VUV excitation cooled down to 8 K.

Energy traps at the silicon surface originating from discontinuities in the lattice is detrimental to the performance of solar cells. Acting as recombination centers, they offer a location where the charge carriers may easily return to their original energy band after excitation. Surface passivation is an effective method to combat this and can be done either by suppressing traps (lowering trap density) or by forming an electric field, preventing the carriers from reaching the defect states. Silicon oxide, SiO2, and aluminum oxide, Al2O3, are two materials which have previously been shown to provide good passivating qualities. In this thesis, SiO2 and Al2O3 have been used both as single layers and in a stack configuration to passivate the surface of crystalline silicon (c-Si). Using a response surface methodology approach, temperature optimization with respect to deposition and annealing temperature has been conducted for SiO2/Al2O3 stacks deposited with plasma-enhanced atomic layer deposition, PEALD. It was shown that the same deposition temperature (Tdeposition = 140 °C, Tanneal = 395 °C) could be used for both materials and provide good passivation with an effective surface recombination velocity, Seff, of 5.3 cm/s (1Ωcm n-type Si wafers). From FTIR measurements, an increase in hydroxyl groups was seen as the SiO2 deposition temperature increased while the opposite was observed for Al2O3 which also showed fewer carbon related impurities with increasing temperature. Increasing the SiO2 temperature strongly affected the fixed charge density, causing it to decrease and even switch polarity. The fixed charge density could also be controlled by varying the thickness of the intermediate SiO2 layer. At a thickness of 1-2 nm, a minimum in the effective lifetime was observed and was correlated to Si close to flat-band conditions. N-type wafers showed a larger negative fixed charge density than p-type wafers which results in stronger field-effect passivation. For phosphorous doped emitters (200 Ω/sq on 10 Ωcm p-type wafer), it was seen that SiO2/Al2O3 stacks with a SiNx anti-reflection coating performed better than SiO2 or Al2O3 single layers. By depositing SiO2 at 130 °C in SiO2/Al2O3 stacks and annealing at 450 °C, an implied open circuit voltage (iVoc) of 710 mV was measured (AM1.5G) together with an implied fill factor (iFF) of 84.1% and a recombination parameter (J0) of 19.2 fA/cm2. Al2O3 single layer showed an extremely low J0 of 10 fA/cm2 but suffered from a decreased iFF and strong injection dependent lifetimes which originates from an inversion layer. ALD ozone processes were successfully developed for SiO2 and Al2O3.  The deposition rate per cycle for SiO2 was found to be only ~0.175 Ǻ/cycle (PEALD ~1.1 Ǻ/cycle), making it rather unpractical for use outside of research. Single layer SiO2 deposited with ozone showed, similarly to a plasma process, almost no surface passivation. Al2O3 however proved to be highly passivating on its own with a τeff = 3.8 ms, Seff = 1.2 cm/s (1 Ωcm n-type) after depositing at 250 °C. Studies on the effect of annealing showed that an annealing temperature of 450 °C is necessary to completely activate the passivation. The low Seff values were attributed to a very high negative fixed charge density ~1013 cm-2 together with strong chemical passivation.

Ce mémoire présente la conception et l'utilisation d'un réacteur microstructuré en silicium pour la catalyse hétérogène et en particulier pour la réaction de déshydrogénation du méthylcyclohexane. Cette réaction permet d'une part de restituer de l'hydrogène stocké et d'autre part de réaliser des développements technologiques importants car elle est endothermique et difficile à mettre en œuvre. Ainsi un nouveau microréacteur obtenu par DRIE a été conçu et scellé avec un capot en pyrex. Il intègre des résistances chauffantes déposées par sérigraphie et une connectique métallique « haute température ». Il comprend soit un catalyseur issu de la microtechnologie, film de platine déposé par pulvérisation cathodique soit un catalyseur plus classique, platine supporté sur alumine. Pour ce dernier catalyseur, le microréacteur préalablement préoxydé est prétraité par plasma oxygène ou par voie liquide afin que le dépôt adhère aux parois. L'enduction peut être réalisée en microréacteur ouvert par trempage dans la suspension d'alumine ou en microréacteur fermé sous vide, ou par circulation de liquide. A la suite de tests catalytiques effectués en macroréacteurs, le catalyseur Pt/Al2O3 a été choisi pour être inséré dans le microréacteur. Les tests catalytiques réalisés avec un microréacteur couplé à un spectromètre de masse ont permis de montrer la présence d'hydrogène. En parallèle, le microréacteur a été utilisé en tant que filtre pour améliorer la sélectivité des capteurs de gaz.

Aqueous-phase reforming (APR) is reported for the first time for the production of H2 from actual biomass. The experiments are carried out in batch using a 100mL Parr microreactor heated to 225C. In this one-pot, two-step process, acid hydrolysis is used to break down the polymeric constituents of biomass to smaller soluble molecules and these species are reformed using a Pt/Al2O3 catalyst. The experiments show that increasing the acid concentration from 1% to 5% causes more than a twelve-fold increase in H2 concentration, with hydrogen a minor product accounting for 18% of the non-condensable gas phase and CO2 as the major product. In the presence of the Pt/Al2O3 reforming catalyst, both the selectivity and yield of hydrogen in the gas phase increase. This is accompanied by a noticeable decrease in carbon monoxide production. Comparison with other feeds such as glucose, wastepaper and ethylene glycol showed that the amount of hydrogen produced from biomass is of a comparable magnitude per gram of feed, although biomass yields more hydrogen per gram of carbohydrate than either glucose or wastepaper. Baseline experiments with only the catalysts in the absence of any biomass show no increase in the reactor system pressure when only water and helium are present, indicating that the observed hydrogen produced is sourced form the biomass.

DC and RF magnetron co-sputtering techniques are one of the most suitable techniques in fabrication of thin films with different compositions. In this work, Al2O3 and Si/Al2O3 thin films were fabricated by using magnetron co-sputtering technique. For Al2O3 films, the stoichiometric, optical and crystallographic analyses were performed. For Si contained Al2O3 films, the formation conditions of Si nanocrystals were investigated. To do so, these thin films were sputtered on Si (100) substrates. Post annealing was done in order to clarify the evolution of Al2O3 matrix and Si nanocrystals at different temperatures. Crystallographic properties and size of the nanocrystals were investigated by X-ray diffraction (XRD) method. The variation of the atomic concentrations and bond formations were investigated with X-ray photoelectron spectroscopy (XPS). The luminescent behaviors of Si nanocrystals and Al2O3 matrix were investigated with photoluminescence (PL) spectroscopy. Finally, the characteristic emissions from the matrix and the nanocrystals were separately identified.

ABSTRACT MICROWAVE SINTERING AND CHARACTERIZATION OF ALUMINA AND ALUMINA MATRIX CERAMIC NANOCOMPOSITES Kayiplar, Burcu M.S., Department of Metallurgical and Materials Engineering Supervisor: Assist. Prof. Dr. Arcan F. Dericioglu April 2010, 106 pages Efficiency of microwave heating on the sintering of ceramic materials has been investigated in comparison to conventional processing. Monolithic alumina with or without sintering additives such as MgO, CaO, Y2O3 were fabricated by both conventional and microwave sintering at temperatures ranging from 1000&deg / C to 1600&deg / C with a constant soaking time of 1 hour. Based on the densification results on monolithic alumina, nanometer-sized SiC or stabilized ZrO2 particle-dispersed alumina matrix ceramic nanocomposites were sintered by both methods at 1300&deg / C and 1500&deg / C for 1 hour. Sintered ceramic materials were characterized in terms of densification, microstructural evolution, chemical composition and mechanical properties such as hardness and indentation fracture toughness. Microwave sintering was determined to be a remarkably effective method in the production of Al2O3 ceramics at considerably low temperatures (&amp / #8804 / 1400&deg / C) compared to conventional sintering in achieving enhanced relative densities reaching to ~97% with improved microstructural characteristics and mechanical properties. Usage of sintering additives at temperatures higher than 1400&deg / C was determined to be effective in densifiying Al2O3 by both methods. Second phase particle incorporation yielded poor densification resulting in a decrease of hardness of the fabricated ceramic nanocomposites / however, their fracture toughness improved considerably caused by the crack deflection at the dispersed particles and grain boundaries reaching to ~4 MPa&middot / m1/2 in the case of SiC particledispersed nanocomposites. Compared to conventional sintering, microwave sintering is more effective in the processing of alumina and alumina matrix nanocomposites leading to similar densification values along with improved microstructural and mechanical characteristics at lower temperatures in shorter soaking periods.