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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
151

Novel gas-separation membranes for intensified catalytic reactors

Escorihuela Roca, Sara 20 May 2019 (has links)
[ES] La presente tesis doctoral se centra en el desarrollo de nuevas membranas de separación de gases, así como su empleo in-situ en reactores catalíticos de membrana para la intensificación de procesos. Para este propósito, se han sintetizado varios materiales, como polímeros para la fabricación de membranas, catalizadores tanto para la metanación del CO2 como para la reacción de síntesis de Fischer-Tropsch, y diversas partículas inorgánicas nanométricas para su uso en membranas de matriz mixta. En lo referente a la fabricación de las membranas, la tesis aborda principalmente dos tipos: orgánicas e inorgánicas. Con respecto a las membranas orgánicas, se han considerado diferentes materiales poliméricos, tanto para la capa selectiva de la membrana, así como soporte de la misma. Se ha trabajado con poliimidas, puesto que son materiales con temperaturas de transición vítrea muy alta, para su posterior uso en reacciones industriales que tienen lugar entre 250-300 ºC. Para conseguir membranas muy permeables, manteniendo una buena selectividad, es necesario obtener capas selectivas de menos de una micra. Usando como material de soporte otro tipo de polímero, no es necesario estudiar la compatibilidad entre ellos, siendo menos compleja la obtención de capas finas. En cambio, si el soporte es de tipo inorgánico, un exhaustivo estudio de la relación entre la concentración y la viscosidad de la solución polimérica es altamente necesario. Diversas partículas inorgánicas nanométricas se estudiaron para favorecer la permeación de agua a través de los materiales poliméricos. En segundo lugar, en cuanto a membranas inorgánicas, se realizó la funcionalización de una membrana de paladio para favorecer la permeación de hidrógeno y evitar así la contaminación por monóxido de carbono. El motivo por el cual se dopó con otro metal la capa selectiva de la membrana metálica fue para poder emplearla en un reactor de Fischer-Tropsch. Con relación al diseño y fabricación de los reactores, durante esta tesis, se desarrolló el prototipo de un microreactor para la metanación de CO2, donde una membrana polimérica de capa fina selectiva al agua se integró para evitar la desactivación del catalizador, y a su vez desplazar el equilibrio y aumentar la conversión de CO2. Por otro lado, se rediseñó un reactor de Fischer-Tropsch para poder introducir una membrana metálica selectiva a hidrogeno y poder inyectarlo de manera controlada. De esta manera, y siguiendo estudios previos, el objetivo fue mejorar la selectividad a los productos deseados mediante el hidrocraqueo y la hidroisomerización de olefinas y parafinas con la ayuda de la alta presión parcial de hidrógeno. / [CAT] La present tesi doctoral es centra en el desenvolupament de noves membranes de separació de gasos, així com el seu ús in-situ en reactors catalítics de membrana per a la intensificació de processos. Per a aquest propòsit, s'han sintetitzat diversos materials, com a polímers per a la fabricació de membranes, catalitzadors tant per a la metanació del CO2 com per a la reacció de síntesi de Fischer-Tropsch, i diverses partícules inorgàniques nanomètriques per al seu ús en membranes de matriu mixta. Referent a la fabricació de les membranes, la tesi aborda principalment dos tipus: orgàniques i inorgàniques. Respecte a les membranes orgàniques, diferents materials polimèrics s'ha considerat com a candidats prometedors, tant per a la capa selectiva de la membrana, així com com a suport d'aquesta. S'ha treballat amb poliimides, ja que són materials amb temperatures de transició vítria molt alta, per al seu posterior ús en reaccions industrials que tenen lloc entre 250-300 °C. Per a aconseguir membranes molt permeables, mantenint una bona selectivitat, és necessari obtindre capes selectives de menys d'una micra. Emprant com a material de suport altre tipus de polímer, no és necessari estudiar la compatibilitat entre ells, sent menys complexa l'obtenció de capes fines. En canvi, si el suport és de tipus inorgànic, un exhaustiu estudi de la relació entre la concentració i la viscositat de la solució polimèrica és altament necessari. Diverses partícules inorgàniques nanomètriques es van estudiar per a afavorir la permeació d'aigua a través dels materials polimèrics. En segon lloc, quant a membranes inorgàniques, es va realitzar la funcionalització d'una membrana de pal¿ladi per a afavorir la permeació d'hidrogen i evitar la contaminació per monòxid de carboni. El motiu pel qual es va dopar amb un altre metall la capa selectiva de la membrana metàl¿lica va ser per a poder emprar-la en un reactor de Fischer-Tropsch. En relació amb el disseny i fabricació dels reactors, durant aquesta tesi, es va desenvolupar el prototip d'un microreactor per a la metanació de CO2, on una membrana polimèrica de capa fina selectiva a l'aigua es va integrar per a així evitar la desactivació del catalitzador i al seu torn desplaçar l'equilibri i augmentar la conversió de CO2. D'altra banda, un reactor de Fischer-Tropsch va ser redissenyat per a poder introduir una membrana metàl¿lica selectiva a l'hidrogen i poder injectar-lo de manera controlada. D'aquesta manera, i seguint estudis previs, el objectiu va ser millorar la selectivitat als productes desitjats mitjançant el hidrocraqueix i la hidroisomerització d'olefines i parafines amb l'ajuda de l'alta pressió parcial d'hidrogen. / [EN] The present thesis is focused on the development of new gas-separation membranes, as well as their in-situ integration on catalytic membrane reactors for process intensification. For this purpose, several materials have been synthesized such as polymers for membrane manufacture, catalysts for CO2 methanation and Fischer-Tropsch synthesis reaction, and inorganic materials in form of nanometer-sized particles for their use in mixed matrix membranes. Regarding membranes manufacture, this thesis deals mainly with two types: organic and inorganic. With regards to the organic membranes, different polymeric materials have been considered as promising candidates, both for the selective layer of the membrane, as well as a support thereof. Polyimides have been selected since they are materials with very high glass transition temperatures, in order to be used in industrial reactions which take place at temperatures around 250-300 ºC. To obtain highly permeable membranes, while maintaining a good selectivity, it is necessary to develop selective layers of less than one micron. Using another type of polymer as support material, it is not necessary to study the compatibility between membrane and support. On the other hand, if the support is inorganic, an exhaustive study of the relation between the concentration and the viscosity of the polymer solution is highly necessary. In addition, various inorganic particles were studied to favor the permeation of water through polymeric materials. Secondly, as regards to inorganic membranes, the functionalization of a palladium membrane to favor the permeation of hydrogen and avoid carbon monoxide contamination was carried out. The membrane selective layer was doped with another metal in order to be used in a Fischer-Tropsch reactor. Regarding the design and manufacture of the reactors used during this thesis, a prototype of a microreactor for CO2 methanation was carried out, where a thin-film polymer membrane selective to water was integrated to avoid the deactivation of the catalyst and to displace the equilibrium and increase the CO2 conversion. On the other hand, a Fischer-Tropsch reactor was redesigned to introduce a hydrogen-selective metal membrane and to be able to inject it in a controlled manner. In this way, and following previous studies, the aim is to enhance the selectivity to the target products by hydrocracking and hydroisomerization the olefins and paraffins assisted by the presence of an elevated partial pressure of hydrogen. / I would like to acknowledge the Spanish Government, for funding my research with the Severo Ochoa scholarship. / Escorihuela Roca, S. (2019). Novel gas-separation membranes for intensified catalytic reactors [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/121139 / TESIS
152

Untersuchung von Multilagenbarrieren für die Verkapselung organischer Bauelemente

Dollinger, Felix 24 November 2015 (has links)
Elektronische Bauteile aus organischen Halbleitern stellen höchste Anforderungen an die Qualität der Verkapselung, die sie vor eindringenden Wasser- und Luftmolekülen schützt. Gleichzeitig soll diese preiswert und mechanisch flexibel sein. Diese Arbeit realisiert Aluminium-Mehrschichtsysteme als wirkungsvolle, biegsame und einfache Verkapselung. Es werden verschiedene Herstellungsmethoden und Zwischenschichtmaterialien untersucht, wobei die Barrierelamination als überlegenes Verfahren etabliert wird. Verkapselungssysteme werden mittels optischer Untersuchung und mit dem elektrischen Calciumtest auf ihre Güte geprüft, bevor sie in Solarzellenalterungsexperimenten unter realitätsnahen Bedingungen zur Anwendung kommen. Laminationsbarrieren aus Aluminiumdünnschichten zeigen reproduzierbar Wasserdampfdurchtrittsraten im unteren 10^(-4) g(H2O)/m^2/Tag-Bereich unter beschleunigten Permeationsbedingungen. Sie verlängern die T(50)-Lebensdauer von Solarzellen um einen Faktor 50 gegenüber unverkapselten Zellen auf Werte, die mit starrer Glas- oder zeitaufwendiger ALD-Verkapselung vergleichbar sind.:1. Einleitung 2. Grundlagen 2.1. Organische Halbleiter 2.2. Organische Photovoltaik 2.2.1. Aufbau und Funktion 2.2.2. Charakterisierung 2.3. Degradationsmechanismen in organischer Photovoltaik 2.3.1. Intrinsische Degradation 2.3.2. Extrinsische Degradation 2.4. Permeationsbarrieren 2.4.1. Wasserdampftransmissionsrate 2.4.2. Permeationsmechanismen 2.5. Vakuumabscheidung 2.5.1. Thermische Vakuumabscheidung 2.5.2. Dünnschichtwachstum 2.6. Calciumtest 2.6.1. Allgemeiner Aufbau 2.6.2. Mögliche Fehlerquellen beim Calciumtest 2.6.3. Optischer Calciumtest 2.6.4. Elektrischer Calciumtest 3. Experimentelle Methoden und Geräte 3.1. Substrate 3.2. Vakuumverdampfung 3.2.1. Evaporation System Königbau 3.2.2. Lesker-Verdampfungsanlage 3.3. Lamination 3.3.1. Epoxidharz Araldite 2011 3.3.2. Barrierekleber Tesa SE 3.3.3. Barrierekleber BK4a Fraunhofer 3.4. Elektrischer Calciumtest 3.4.1. Probenaufbau 3.4.2. Messapparatur 3.5. Solarzellencharakterisierung 3.5.1. Externe Quanteneffizienz 3.5.2. Strom-Spannungskennlinien 3.6. Klimaschrank 4. Ergebnisse und Diskussion 4.1. Defektradius von Aluminiumbarrieren 4.2. Keimschichten 4.3. Multilagenbarrieren 4.3.1. Vakuumprozessierte Zwischenschichten 4.3.2. Laminationsbarrieren 4.4. Integration von Calcium als Wasserfangstoff 4.5. Solarzellenalterung 4.5.1. Vergleich der Glasverkapselten Proben 4.5.2. Vergleich der Verkapselungstechniken 4.5.3. Vergleich der unverkapselten Proben: MoO3-, Cu-, Cr-Schichten 4.5.4. Degradation der Epoxidharzproben 4.5.5. Wirkungsgrad und Degradation der ALD-Proben 4.6. Vollflexible Solarzellen mit Laminationsbarriere 5. Zusammenfassung und Ausblick A. Anhang A.1. Abkürzungsverzeichnis A.2. Häufige Formelzeichen / Organic electronic devices require excellent encapsulation to protect them from intruding water- and air-molecules. At the same time, the encapsulation has to be inexpensive and flexible. This work presents aluminum multilayer barriers as highly effective, flexible and low-cost encapsulation. Various production methods and interlayer materials are investigated and barrier-lamination is established as superior process. Encapsulation systems are evaluated optically and by means of the electrical calcium-test, before they are employed in realistic solar cell aging experiments. Lamination-barriers of thin aluminum films show reproducible water-vapor transmission rates in the low 10^(-4) g(H2O)/m^2/day-range under accelerated permeation conditions. They improve the T(50)-lifetime of solar cells by a factor of 50 compared to unencapsulated cells, reaching values on par with rigid glass encapsulation or time-consuming atomic layer deposition.:1. Einleitung 2. Grundlagen 2.1. Organische Halbleiter 2.2. Organische Photovoltaik 2.2.1. Aufbau und Funktion 2.2.2. Charakterisierung 2.3. Degradationsmechanismen in organischer Photovoltaik 2.3.1. Intrinsische Degradation 2.3.2. Extrinsische Degradation 2.4. Permeationsbarrieren 2.4.1. Wasserdampftransmissionsrate 2.4.2. Permeationsmechanismen 2.5. Vakuumabscheidung 2.5.1. Thermische Vakuumabscheidung 2.5.2. Dünnschichtwachstum 2.6. Calciumtest 2.6.1. Allgemeiner Aufbau 2.6.2. Mögliche Fehlerquellen beim Calciumtest 2.6.3. Optischer Calciumtest 2.6.4. Elektrischer Calciumtest 3. Experimentelle Methoden und Geräte 3.1. Substrate 3.2. Vakuumverdampfung 3.2.1. Evaporation System Königbau 3.2.2. Lesker-Verdampfungsanlage 3.3. Lamination 3.3.1. Epoxidharz Araldite 2011 3.3.2. Barrierekleber Tesa SE 3.3.3. Barrierekleber BK4a Fraunhofer 3.4. Elektrischer Calciumtest 3.4.1. Probenaufbau 3.4.2. Messapparatur 3.5. Solarzellencharakterisierung 3.5.1. Externe Quanteneffizienz 3.5.2. Strom-Spannungskennlinien 3.6. Klimaschrank 4. Ergebnisse und Diskussion 4.1. Defektradius von Aluminiumbarrieren 4.2. Keimschichten 4.3. Multilagenbarrieren 4.3.1. Vakuumprozessierte Zwischenschichten 4.3.2. Laminationsbarrieren 4.4. Integration von Calcium als Wasserfangstoff 4.5. Solarzellenalterung 4.5.1. Vergleich der Glasverkapselten Proben 4.5.2. Vergleich der Verkapselungstechniken 4.5.3. Vergleich der unverkapselten Proben: MoO3-, Cu-, Cr-Schichten 4.5.4. Degradation der Epoxidharzproben 4.5.5. Wirkungsgrad und Degradation der ALD-Proben 4.6. Vollflexible Solarzellen mit Laminationsbarriere 5. Zusammenfassung und Ausblick A. Anhang A.1. Abkürzungsverzeichnis A.2. Häufige Formelzeichen
153

Encapsulation and stability of organic devices upon water ingress

Nehm, Frederik 22 April 2016 (has links)
Organic electronic devices like organic solar cells and organic light-emitting diodes quickly degrade in ambient conditions if left unprotected. High susceptibility to moisture necessitates their encapsulation. The maximum water ingress acceptable to achieve reasonable lifetimes ranges several orders of magnitudes below industrial flexible barrier solutions. In this work, an electrical Ca-Test is used to optimize and investigate moisture barriers towards their application in device encapsulation. Aside from substantial improvement of the measurement system, atomic layer deposited, sputtered, and thermally evaporated barriers are screened and their water vapor transmission rates measured down to 2*10^(-5) g(H2O)/(m²*d) at 38 °C and 90% RH. Completely new encapsulation techniques are presented using novel molecular layer deposition interlayers or lamination of independently processed barriers. This way, simple Al layers become high-end moisture barriers. Furthermore, different single layer barriers are exposed to a wide variety of climates. An in-depth analysis of water permeation mechanics reveals sorption governed by Henry's law as well as dominance of interface diffusion below the barrier at late test stages. Investigated moisture barriers are applied to organic light-emitting diodes as well as solar cells and great improvements of lifetimes are observed. In addition, significant improvements in stability towards water ingress are witnessed upon the integration of adhesion layers at the cathode interface. Lastly, the great potential and applicability of this technology is showcased by the production and aging of fully flexible, highly efficient, stable organic solar cells. / Organische Elektronik-Bauteile wie organische Solarzellen und organische Leuchtdioden degradieren in kürzester Zeit, wenn sie ungeschützt feuchter Luft ausgesetzt sind. Ihre starke Anfälligkeit gegenüber Wasserdampf macht ihre Verkapselung notwendig. Der maximale Wassereintritt, der für sinnvolle Lebensdauern noch zulässig erscheint, liegt jedoch noch mehrere Größenordnungen unter dem, was mit existierenden Technologien erreicht werden kann. In der vorliegenden Arbeit wird ein elektrischer Kalzium-Korrosionstest benutzt, um Barrieresysteme auf ihre Anwendbarkeit als Verkapselung organischer Bauelemente hin zu untersuchen und zu optimieren. Abgesehen von signifikanten Verbesserungen am Messsystem werden Wasserdampfbarrieren aus Atomlagenabscheidungs-, Kathodenzerstäubungs- und Verdampfungsprozessen vermessen. Dabei werden außerordentlich niedrige Wasserdampfdurchtrittsraten von nur 2*10^(-5) g(H2O)/(m²*d) in einem Alterungsklima von 38 °C und 90% relativer Feuchte verzeichnet. Vollkommen neue Verkapselungstechniken werden realisiert, wie etwa die Integration von Zwischenschichten durch Molekularlagenabscheidung oder die Lamination zweier Barrieren, die unabhängig voneinander prozessiert werden. Dieser Prozess verwandelt einfache Al Schichten in qualitativ hochwertige Wasserdampfbarrieren. Des Weiteren werden verschiedene Einzelschicht-Barrieren einer breiten Klimavariation ausgesetzt. Dies ermöglicht die genaue Analyse der Permeationsmechanismen des Wassers. Es wird gezeigt, dass Sorption hier dem Henry'sche Gesetz folgt. Diffusion entlang der Grenzfläche unterhalb der Barriere dominiert die Permeation zu späten Testzeiten. Die untersuchten Wasserdampfbarrieren werden an organischen Leuchtdioden und Solarzellen erprobt und zeigen große Verbesserungen bezüglich ihrer Lebensdauern. Darüber hinaus zeigt sich eine stark verbesserte Resistenz gegenüber Wassereintritt, wenn eine zusätzliche Adhäsionsschicht unter der Kathodengrenzfläche integriert wird. Letztendlich zeigt sich das große Potential und die Anwendbarkeit der Ergebnisse in der hohen Effizienz und langen Lebensdauer vollflexibler, verkapselter organischer Solarzellen.
154

A NUMERICAL MODEL OF HEAT- AND MASS TRANSFER IN POLYMER ELECTROLYTE FUEL CELLS : A two-dimensional 1+1D approach to solve the steady-state temperature- and mass- distributions

Skoglund, Emil January 2021 (has links)
Methods of solving the steady state characteristics of a node matrix equation system over a polymer electrolyte fuel cell (PEFC) were evaluated. The most suitable method, referred to as the semi-implicit method, was set up in a MATLAB program. The model covers heat transfer due to thermal diffusion throughout the layers and due to thermal advection+diffusion in the gas channels. Included mass transport processes cover only transport of water vapor and consist of the same diffusion/advection schematics as the heat transfer processes. The mass transport processes are hence Fickian diffusion throughout all the layers and diffusion+advection in the gas channels. Data regarding all the relevant properties of the layer materials were gathered to simulate these heat- and mass transfer processes.Comparing the simulated temperature profiles obtained with the model to the temperature profiles of a previous work’s model, showed that the characteristics and behavior of the temperature profile are realistic. There were however differences between the results, but due to the number of unknown parameters in the previous work’s model it was not possible to draw conclusions regarding the accuracy of the model by comparing the results.Comparing the simulated water concentration profiles of the model and measured values, showed that the model produced concentration characteristics that for the most part alignedwell with the measurement data. The part of the fuel cell where the concentration profile did not match the measured data was the cathode side gas diffusion layer (GDL). This comparison was however performed with the assumption that relative humidity corresponds to liquid water concentration, and that this liquid water concentration is in the same range as the measured data. Because of this assumption it was not possible to determine the accuracy of the model.
155

High Temperature Volatility and Oxidation Measurements of Titanium and Silicon Containing Ceramic Materials

Nguyen, QuynhGiao N. January 2008 (has links)
No description available.
156

Feasibility of Troposphere Propagation Delay Modeling of GPS Signals using Three-Dimensional Weather Radar Reflectivity Returns

Muvvala, Priyanka 26 July 2011 (has links)
No description available.
157

Off-Host Biology and Ecology of Immature Gulf Coast Ticks (Amblyomma Maculatum Koch) in Mississippi

Portugal, Jose Santos 06 May 2017 (has links)
Little is understood about off-host behavior and ecology of immature Amblyomma maculatum Koch (Gulf Coast tick). A more complete understanding of this tick is essential to protect human and animal health. My research focused on seasonality and distribution of immatures in Mississippi, potential suitability of some insect and human hosts to larvae, and aspects of nymphal questing behavior. A single larva was collected (third off-host collection reported) when sampling A. maculatum habitat using a novel device. Collection of this larva in November expands the stage’s known seasonality and confirmed a prediction concerning seasonality of larval A. maculatum. Low frequency of immatures (8.3%) confirmed that they’re incredibly difficult to collect off-host. Nymphal collections peaked in March, and known seasonality was extended for both nymphs and adults. I examined known records, elucidating seasonality and distribution of A. maculatum in Mississippi. Either multiple generations per year or diapause are responsible for observed bi-modal distribution of immature collections. Additionally, I compiled the most extensive host record of immature A. maculatum in Mississippi and investigated seasonality patterns using USDA plant hardiness zones. I compiled the most complete record of ticks found on arthropods. Amblyomma americanum and A. maculatum were both confirmed to crawl onto arthropods, giving support to occasional, unintentional dispersal by phoresy. There was no conclusive evidence that larval A. maculatum feed on arthropods, however data supported feeding by larval A. americanum. These results have interesting implications regarding evolution of pathogens/endosymbionts. I provided the first evidence that larval A. maculatum can attach to humans. Rickettsia parkeri, a human pathogen transmitted by this species has recently been shown to be capable of transovarial transmission. Therefore, larval A. maculatum may provide another avenue of transmission. I have demonstrated that A. maculatum are difficult to collect off-host in part because they prefer to quest low to the ground. In choice studies, 5-cm-tall stems were most likely to be occupied by nymphs released into an array of stems. Low vapor pressure deficit encouraged questing, while higher VPD and warmer temperature increased questing height. These results may have implications in understanding host-seeking behavior in other tick species as well.
158

Etude de l'Influence de la vapeur d'eau sur l'oxydation à haute température d'un alliage chromino-formeur à base de nickel / Study of water vapor influence in high temperature oxidation for a chromia forming nickel base alloy

Rolland, Raphaël 14 March 2012 (has links)
Ce travail s’inscrit dans un cadre de recherche qui a pour objectif essentiel l’étude de l’influence de la vapeur d’eau sur l’oxydation à haute température d’un alliage formeur de Cr2O3 à base de nickel. L’alliage étudié pour cette étude est le SY 625. L’originalité de cette étude repose sur l’utilisation d’un montage expérimental, mis en oeuvre au laboratoire. Ce montage appelé « montage vapeur d’eau » permet de réaliser l’oxydation du SY 625 à haute température (900-1100°C) en présence de vapeur d’eau (7,5 et 33% de vapeur d’eau) avec différents gaz vecteurs (oxygène, air, argon et azote) en conditions isotherme ou cyclique. Les résultats cinétiques obtenus sous air, ne montrent pas de différences notables que l’oxydation soit réalisée en conditions sèche ou humide (quelque soit le taux de vapeur d’eau). Les résultats n’ont pas montré de breakaway pour les durées d’oxydation allant jusqu’à 48 heures. Ceci est attribué au fait qu’il n’y a pas formation d’oxydes de fer sachant que l’alliage contient seulement 0,23% en masse de fer. Les résultats de DRX montrent la formation des mêmes phases quel-que-soit le gaz vecteur utilisé (en atmosphère sèche ou humide). A 900 et 1000°C, l’oxyde Cr2O3 est détecté ainsi que deux composés intermétalliques : Ni3Mo et NbNi4. En revanche à 1100°C, l’oxyde Cr2O3 est toujours présent mais les composés intermétalliques sont oxydés pour donner un oxyde mixte CrNbO4. L’oxydation du molybdène au dessus de 1000°C conduit à la formation de MoO3 qui est un oxyde volatil. Les analyses morphologiques, ont montré la présence de couches de chromine plus plastiques avec une porosité répartie sur toute l’épaisseur de la couche pour les essais réalisés en présence de vapeur d’eau. Les couches d’oxyde sont alors plus adhérentes. Ceci a été confirmé par des essais d’oxydation en conditions cycliques, qui ont montré notamment à 1100°C, une meilleure tenue mécanique de la couche d’oxyde en présence de vapeur d’eau. Les tests d’oxydation en présence d’un marquage à l’or a aussi permis de mettre en évidence un mécanisme d’oxydation mixte pour les oxydations réalisées en atmosphères riche en oxygène que l’on soit sous atmosphère sèche ou humide. En revanche, le marquage à l’or a montré la présence d’un mécanisme d’oxydation interne pour les atmosphères pauvres en oxygène, avec des couches d’oxydes présentant une adhérence parfaite. Le fait d’ajouter de la vapeur d’eau à ces atmosphères pauvres en oxygène, entraine la réapparition d’un mécanisme de diffusion mixte. / This work is a part of a research project which has for essential objective the study of water vapor influence in high temperature oxidation for a chromia forming nickel base alloy. Alloy studied for this study is the SY 625. Originality of this study is based on an experimental assembly use, create in the laboratory. This assembly called “water vapor assembly” is used for realized SY 625 high temperature oxidation (900-1100°C) in presence of water vapor (7,5 and 33 vol. % water vapor) with various carriers gas (oxygen, air, argon and nitrogen) in isothermal and cyclic conditions. The kinetic results obtained under air, do not show considerable differences that the oxidation is realized in dry or wet conditions (with the various water vapor rate). The results do not show breakaway for the oxidation durations going to 48 hours. This is attributed to the fact that there is no formation of oxides iron knowing that the alloy contains only 0,23 mass % of iron. The XRD results show the formation of the same phases which is the carrier gas used (in dry or wet atmosphere). At 900 and 1000°C, the Cr2O3oxide is detected with two intermetallic compounds : Ni3Mo and NbNi4. On the other hand at 1100°C, the oxide Cr2O3 is always present but the intermetallic compounds are oxidized to give a mixed oxide CrNbO4. The oxidation of the molybdenum above 1000°C leads to the formation of MoO3 which is a volatile oxide. The morphological analyses, showed the presence of more plastic chromia layers with a distributed porosity on all the thickness of the layer for the test realized in water vapor presence. The oxide layers are then more adherents. This was confirmed by oxidation test in cyclic conditions, which showed in particular at 1100°C, a better mechanical behavior of oxide layer in water vapor presence. The oxidation tests with gold marker experiments are also showed a mixed oxidation mechanism for the oxidations realized in rich oxygen atmospheres under dry or wet atmosphere. On the other hand, gold marker experiments showed the presence of a internal oxidation mechanism for poor oxygen atmospheres, with oxides layers showing a perfect adhesion. The fact of adding water vapor to these poor oxygen atmospheres, lead to the reappearance of a mixed diffusion mechanism.
159

HotHumiBox, ett provelement mellan två kammare / HotHumiBox, a test element between two chambers

Lekic, Dragan January 2018 (has links)
HotHumiBox är en försöksutrustning som finns på Linnéuniversitetet och som ska ge bättre kunskap och förståelse om hur fukt och temperatur varierar i en provkropp monterad mellan två kammare där klimatet kan styras var för sig. Syftet med examensarbetet är att undersöka om HotHumiBoxen fungerar väl och huruvida den kan börja användas i undervisningen i olika kurser inom institutionen för byggteknik på Linnéuniversitetet, bl.a. i samband med demonstrationslaborationer vid föreläsningar om fukt. För att genomföra arbetet har mätningar med tre olika klimat utförts på ett provelement som motsvarar en yttervägg som kan finnas i nybyggda typhus. Resultatet av mätningar utförda med HotHumiBoxen presenteras i form av tabeller och diagram och jämförs slutligen med beräkningar av fukt- och temperaturtillstånd. Jämförelsen mellan mätningar och beräkningar visar att givarna som styr klimatet i båda kamrarna visar mycket bra resultat. Däremot visar majoriteten av givarna i provelementet antingen lite för höga eller för låga värden för att resultatet ska anses som tillfredställande. För att få en bekräftelse på att HotHumiBoxen fungerar väl rekommenderas därför att ytterligare mätningar görs. / HotHumiBox is an experimental equipment that is available at Linnaeus University and is supposed to provide better knowledge and understanding about the way moisture and temperature varies in a building element installed between two chambers in which the climate can be controlled separately. The purpose of this work is to investigate whether the HotHumiBox works well and whether it can be used at various courses at the Department of Building Technology at Linnaeus University, such as demonstration laboratory experiments at lectures on moisture. Measurements with three different climates were performed on a building element that corresponds to a wall that could be installed in modern houses. The results of the HotHumiBox measurements are being presented in tables and diagrams and are being compared with moisture and temperature calculations. The comparison between measurements and calculations shows that the sensors which control the climate in both chambers show very good results. On the other hand, the majority of the sensors in the test element show either too high or too low values for the result to be considered as satisfactory. Therefore, it is recommended that some more tests and measurements are done before it can be concluded that the HotHumiBox work well.
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Enhanced adhesives for the encapsulation of flexible organic photovoltaic modules / Adhésifs améliorés pour l'encapsulation des modules organiques photovoltaïques flexibles

Boldrighini, Patrick Mark 30 June 2015 (has links)
La limitation de perméation des gaz aux bordes de l’encapsulation des photovoltaïques organiques flexibles a été adressée par l’identification des chemins de perméation du vapeur d’eau et par la formulation des nanocomposites adhésives. Une version modifiée du test de calcium optique a été développée pour identifier l’importance des chemins de perméation différents présent dans l’encapsulation des modules photovoltaïques organiques flexibles. Les nanoparticules des phyllosilicates et les nanoparticules des zéolithes ont été dispersées dedans les formulations des adhésifs différents incluant les adhésifs acryliques sensibles à pression et les adhésifs UV réticulables. Les propriétés mécaniques, optiques, et barrières de vapeur d’eau des nanocomposites ont été caractérisés en plus de leur photo-stabilité sous irradiation UV. Les nanocomposites ont été également utilisés pour encapsuler les cellules photovoltaïques organiques et la stabilité des dispositifs a été évaluer sous les conditions de vieillissement accélérés d’humidité et température. / In order to address the issue of lateral water and oxygen permeation through the sides of the encapsulation and into flexible organic photovoltaic (OPV) devices, the water vapor permeation pathways were identified and several adhesive nanocomposites formulated and tested to limit these pathways. To identify the relative importance of the various water vapor permeation pathways present in the encapsulation of flexible OPV devices, a modified version of the optical calcium test was developed. Passive nanoparticles (phyllosilicates) and active nanoparticles (zeolites) were both evaluated dispersed in UV curing acrylate adhesives and acrylic block copolymer pressure sensitive adhesives. The nanocomposites were characterized for their mechanical and optical properties as well as their water vapor permeation and UV photostability. The adhesives were also used to encapsulate OPV devices and tested in accelerated humidity aging.

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