Tesis: "In situ SEM characterization"

1

Berthier, Rémy. "Development of characterization methods for in situ annealing and biasing of semiconductor devices in the TEM". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY014/document.

Texto completo

Resumen

Dans cette thèse, nous abordons les défis rencontrés lors de la caractérisation des mémoires non volatiles par microscopie en transmission in situ. Les innovations récentes menées sur les porte-objets de TEM in situ basés sur l'utilisation de puces en silicium apportent de grands avantages comparée aux précédents modèles. Cependant, cette technique reste complexe et les expériences de MET in situ sont difficiles à mener à terme. Ce manuscrit tente d'apporter de nouvelles solutions pour permettre l'observation à l'échelle atomique pendant le recuit, ou la polarisation d'un échantillon dans le MET. Ce projet a été mené à travers plusieurs améliorations effectuées au cours des différentes étapes des expériences de MET in situ. Cette thèse se focalise plus particulièrement sur les problèmes rencontrés lors de la polarisation de dispositifs de mémoires résistives de taille nanométrique. Ces travaux furent conduits à travers une étude des instruments utilisés, le développement de nouvelles méthodes de préparation d'échantillons, et une analyse de l'impact de l'imagerie électronique sur le fonctionnement d'un dispositif dans le MET.Tout d’abord, une nouvelle méthode est développée spécifiquement pour les expériences de MET in situ en température. Grâce à ces développements, la cristallisation de mémoires à changement de phase en GeTe est observée en temps réel. Ces résultats ont notamment permis d'obtenir des informations utiles pour le développement de mémoires à changement de phase de type chalcogénure. Ensuite, de nouvelles puces en silicium dédiées à la polarisation in situ sont développées et produites. Une étude est ensuite menée sur la préparation d'échantillons par FIB afin d'améliorer la qualité des contacts électriques pour la polarisation in situ, ainsi que la technique de préparation elle-même. La qualité de cette méthode est ensuite démontrée à travers des mesures quantitatives obtenues pendant la polarisation in situ d'un échantillon de référence de type jonction PN. Ces développements sont ensuite appliqués afin d’observer des dispositifs de mémoires résistives de type CBRAM en fonctionnement dans le microscope électronique en transmission. Ces résultats ont permis d'apporter de nouvelles informations sur les mécanismes de fonctionnement des mémoires résistives, ainsi que sur la technique de polarisation in situ
In this work, we address the current challenges encountered during in situ Transmission Electron Microscopy characterization of emerging non volatile data storage technologies. Recent innovation on in situ TEM holders based on silicon micro chips have led to great improvements compared to previous technologies. Still, in situ is a particularly complicated technique and experiments are extremely difficult to implement. This work provides new solutions to perform live observations at the atomic scale during both heating and biasing of a specimen inside the TEM. This was made possible through several improvements performed at different stages of the in situ TEM experiments. The main focus of this PhD concerned the issues faced during in situ biasing of a nanometer size resistive memory device. This was made possible through hardware investigation, sample preparation method developments, and in situ biasing TEM experiments.First, a new sample preparation method has been developed specifically to perform in situ heating experiments. Through this work, live crystallization of a GeTe phase change Memory Material is observed in the TEM. This allowed to obtain valuable information for the development of chalcogenide based Phase Change Resistive Memories. Then, new chips dedicated to in situ biasing experiments have been developed and manufactured. The FIB sample preparation is studied in order to improve electrical operation in the TEM. Quantitative TEM measurements are then performed on a reference PN junction to demonstrate the capabilities of this new in situ biasing experimental setup. By implementing these improvements performed on the TEM in situ biasing technique, results are obtained during live operation of a Conductive Bridge Resistive Memory device. This allowed to present new information on the resistive memories functioning mechanisms, as well as the in situ TEM characterization technique itself

Los estilos APA, Harvard, Vancouver, ISO, etc.

2

Bignoli, Francesco. "Tailoring mechanical behavior of metallic thin films through nanoengineering design strategies : investigation of metallic glass and high entropy alloy films". Electronic Thesis or Diss., Paris 13, 2024. http://www.theses.fr/2024PA131031.

Texto completo

Resumen

Les couches minces métalliques sont devenues l'objet de recherches intensives ces dernières années en raison de l'activation des effets de taille mécanique améliorant la résistance et la plasticité.Cependant, l'étude de la connexion entre la structure locale et le comportement mécanique d'un film mince n'est pas pleinement comprise et la recherche de nouvelles nanostructures capables d'améliorer leurs propriétés mécaniques est encore un sujet ouvert.Dans ce projet de doctorat, nous exploitons le potentiel du dépôt laser pulsé (PLD) pour synthétiser de nouveaux verres métalliques (TFMG) et des alliages à haute entropie en films minces (TFHEA) avec une microstructure unique et sur mesure, y compris assemblée en grappes, en nanolaminés, ajustant la chimie locale (notamment avec l'oxygène) pour produire des couches minces présentant une résistance et une plasticité améliorées.Pour le cas des TFMGs, le contrôle de la structure locale permet de retarder et de supprimer les bandes de cisaillement et d'améliorer la résistance, ce qui se traduit par des films ayant la limite d'élasticité > 3 GPa et une déformation homogène de 15 %.Pour le cas des TFHEAs, le PLD peut contrôler la taille des grains obtenant des valeurs élevées de dureté (11 GPa) et une résistance à la fissuration lors de tests de traction sur Kapton® (3,44 %) par rapport aux échantillons fait par pulvérisation (8,3 GPa et 2 %). Dans l'ensemble, dans cette thèse, nous ouvrons la voie à l'utilisation du PLD comme nouvelle technique de synthèse de films métalliques avec une nanostructure et une composition uniques et de grandes propriétés mécaniques pour des applications en revêtements structuraux haute performance
Metallic thin films have become object of intense research in recent years due to the activation of mechanical size effects improving strength and plasticity.However, the study of the connection between the local structure and the mechanical behavior of a thin film is not fully understood yet and the research for new nanostructures capable to further improve and tailor their mechanical properties is still an open subject.In this PhD project, we exploit the potential of Pulsed Laser Deposition (PLD) to synthetize novel thin film metallic glasses (TFMGs) and high entropy alloys (TFHEAs) with unique and tailored composition-microstructure including cluster-assembled, nanolaminate, while tuning local chemistry (especially with O incorporation) to produce thin films with improved strength and plasticity.For the case of TFMGs the control of the local structure allows the delay and suppression of shear bands and improvement of the strength resulting in films with yield strength > 3 GPa and 15% homogeneous deformation.For the case of TFHEAs, PLD can control the grain size obtaining large values of hardness (11 GPa) and have improved crack resistance on tensile tests on Kapton® (3.44%) with respect to sputtered samples (8.3 GPa and 2%).Overall, within this thesis we open the way to the use of PLD as a new technique to synthetize metallic films with unique nanostructure and composition and large mechanical properties for applications as high-performance structural coatings

Los estilos APA, Harvard, Vancouver, ISO, etc.

3

Willeman, Héloïse. "Multi-scale characterization of deformation mechanisms of poly-ether-ether-ketone (PEEK) under tensile stretching". Electronic Thesis or Diss., Lyon, INSA, 2023. http://www.theses.fr/2023ISAL0006.

Texto completo

Resumen

L’objectif de cette thèse est d’établir le scénario multi-échelles de déformation du PEEK lorsqu’il est sollicité en traction uniaxiale. Préalablement à la mise en oeuvre d’échantillons de deux grades commerciaux de PEEK, les propriétés thermiques et mécaniques de ces matériaux ont été caractérisées. La température d’oubli thermodynamique ainsi que la sensibilité aux vitesses de refroidissement ont été établies. Des éprouvettes de traction ont été obtenues à partir de plaques thermocompressées, procédé choisi pour obtenir des morphologies les plus isotropes possibles. Les propriétés mécaniques en traction ont ensuite été caractérisées au-dessus et au-dessous de la transition vitreuse de la phase amorphe (Tg). Grâce à un dispositif expérimental fabriqué sur mesure, des essais de traction à deux températures distinctes au-dessous et au-dessus de Tg ont été suivis par diffusion des rayons X aux petits (SAXS) et grands angles (WAXS) pour caractériser les déformations à l’échelle des empilements lamellaires et à l’échelle de la maille cristalline. Simultanément, le champ de déformation a été mesurée par corrélation d’images (DIC) afin de comparer la déformation macroscopique et microscopique. Pour les deux températures, les lamelles tendent à s’orienter perpendiculairement à la direction de traction (TD). Ce mécanisme d’orientation local (que nous appelons « modèle de réseau de chaînes ») est induit par la transmission des contraintes par les chaînes amorphes reliant les lamelles cristallines adjacentes. Au-dessus de Tg, l’allongement local est plus faible que l’allongement macroscopique dans les lamelles perpendiculaire à TD, ce qui implique que les lamelles inclinées doivent être cisaillées. L’évolution de la distribution d’orientation des lamelles appuie ce résultat. Une morphologie fortement orientée est finalement obtenue quelle que soit la température. Cependant, le profil d’endommagement est différent. En-dessous de Tg, le profil de diffusion centrale indique l’existence de petites entités (lamelles ou crystallites) orientées aléatoirement. A hautes température, le matériau est fibrillaire et présente des cavités
The aim of this PhD work is accessing the microscopic deformation mechanisms of bulk poly-ether-ether-ketone (PEEK) under tensile stretching. Beforehand, the thermal and mechanical properties of two commercial grades of PEEK were characterized. Tensile specimens were then compression-molded to obtain morphologies as isotropic as possible and characterized below and above the glass transition temperature. Deformations at the scales of lamellar stacks and of the crystalline unit cell have been characterized by small and wide-angle X-ray scattering (SAXS and WAXS) performed in-situ during tensile tests. Simultaneously, the strain field within the samples was followed by digital image correlation (DIC) in order to compare microscopic and macroscopic strains. At both temperatures, lamellae tend to orient perpendicular to the tensile direction (TD). This orientation mechanism (which we denote as ‘Chain Network model’) is driven by the amorphous chains which transmit the stress between adjacent lamellae. The tensile strain in lamellar stacks perpendicular to TD is lower than the macroscopic tensile strain, which must be compensated by increased shear in inclined stacks. Some differences of behavior have been observed depending on the test temperature, especially at high deformation. A highly oriented morphology is ultimately obtained in all cases. However, the central scattering profiles changes with testing temperatures. Below Tg, the presence of small entities randomly oriented is indicated. Above Tg, the material is fibrillar and contains cavities

Los estilos APA, Harvard, Vancouver, ISO, etc.

4

Chavez, Castillo Ana Gabriela. "Apport des modèles réduits pour la caractérisation thermique de matériaux de construction : mesures in situ d'isolants et étude multi-échelle d'un bois sec". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST040.

Texto completo

Resumen

En simulation numérique thermique, le problème inverse consiste à partir de mesures de température, à retrouver un ou plusieurs paramètres de l'équation de la chaleur discrétisée. C'est une procédure complexe qui reste souvent limitée à une géométrie simple. L'idée est alors d'utiliser des modèles réduits thermiques de type modaux, qui vont permettre de diminuer considérablement le nombre d'inconnues tout en maintenant une précision satisfaisante sur l'intégralité du domaine modélisé. Ces modèles vont alors permettre d'étendre la technique des problèmes inverses à tout type de géométrie, quelle que soit sa complexité.L'objectif de ce travail de thèse consiste à évaluer l'efficacité d'une telle méthode pour une application liée à la thermique du bâtiment, dans laquelle on cherche à identifier les propriétés de matériaux isolants (capacité et conductivité thermiques).Le principal travail a été la mise en application de cette technique pour une mesure in situ, via une sonde de type fil chaud, jusqu'ici inadaptée aux isolants thermiques.Une seconde application de cette technique de résolution de problèmes inverses par modèle réduit est la caractérisation d'un matériau bio-sourcé à partir de relevés tomographiques à l'échelle microscopique.Pour ces deux applications, les développements numériques effectués ont permis la réalisation de premiers essais expérimentaux encourageants
In numerical thermal simulation, the inverse problem consists in finding one or more parameters of the discretized heat equation from temperature measurements. This is a complex procedure that often remains limited to simple geometry. The idea is then to use modal-type thermal reduced models, which will considerably reduce the number of unknowns while maintaining satisfactory accuracy over the entire modelled domain. These models will then allow to extend the technique of inverse problems to any type of geometry, whatever its complexity.The objective of this thesis work is to evaluate the efficiency of such a method for an application related to building thermics, in which one seeks to identify the properties of insulating materials (thermal capacity and conductivity).The main work has been the application of this technique for an in situ measurement, using a hot wire probe, which has so far been unsuitable for thermal insulation.A second application of this technique to solve inverse problems by reduced model is the characterization of a bio-sourced material from tomographic surveys at the microscopic scale.For these two applications, the digital developments carried out have allowed the realization of encouraging first experimental trials

Los estilos APA, Harvard, Vancouver, ISO, etc.

5

Ben, Hafsia Khaoula. "Identification des micro-mécanismes de déformation du PET amorphe et semi-cristallin in situ au cours d’un essai mécanique". Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0081/document.

Texto completo

Resumen

Selon leur formulation et leur mise en forme et grâce à leur complexité microstructurale induite, les polymères thermoplastiques bénéficient d’une grande diversité de propriétés thermomécaniques. Cependant, l’évolution de la microstructure de ces matériaux au cours de leur utilisation reste difficile à identifier. Afin de mieux comprendre les modifications microstructurales ayant lieu au cours de sollicitations thermomécaniques, différentes techniques non destructives de caractérisation en temps réel et in situ ont été développées. Dans ce contexte, un Poly (Ethylène Téréphtalate) (PET) amorphe et semi-cristallin a été étudié afin de mettre en évidence l’effet de la microstructure sur les propriétés macroscopiques du matériau. Pour ce faire, plusieurs couplages de techniques expérimentales de caractérisation ont été mis en œuvre tels que la spectroscopie Raman et la diffraction/diffusion des rayons X couplées au système de VidéoTraction™ ou la spectroscopie Raman couplée à la calorimétrie différentielle à balayage (DSC) pour une caractérisation des micromécanismes de déformation et du comportement thermique du matériau respectivement. Le suivi de différentes bandes vibrationnelles judicieusement identifiées a permis d’établir un nouveau critère robuste et capable de mesurer avec exactitude le taux de cristallinité du matériau ou de remonter aux températures caractéristiques de sa morphologie (Tg, Tc, Tcc, Tf) grâce aux informations extraites d’un spectre Raman. De plus, un système de caractérisation relaxationnelle par un couplage de la spectroscopie diélectrique dynamique avec un essai de traction a été utilisé afin de mettre en évidence l’effet de la mobilité moléculaire sur la déformation élasto-visco-plastique du PET. D’un point de vue mécanique, les principaux micromécanismes de déformation ont été étudiés en temps réel pendant un essai de traction à différentes températures et vitesses de déformation vraies constantes : l’orientation macromoléculaire, l’endommagement volumique, le développement de mésophase et la cristallisation induite sous contrainte, ont été observés et quantifiés in situ en utilisant les couplages précédents au synchrotron Petra III de Hambourg et au synchrotron Elettra de Trieste. En parallèle, une étude de la mobilité moléculaire (paramètre déterminant à la prédominance de tel ou tel micromécanisme de déformation) a été menée via des analyses relaxationnelles réalisées au cours de la déformation du matériau. En complément, des expériences en temps réel, des études post mortem par les techniques précédemment citées et par radiographie X, microscopie électronique à balayage et tomographie X ont été réalisées afin d’apprécier l’influence de la relaxation mécanique du PET
According to their formulations and forming processes and thanks to the complexity of their induced microstructure, thermoplastic polymers show a wide range of thermomechanical properties. However, the identification of the evolution of the microstructure of these materials during their use remains difficult. To better understand the microstructural changes occurring during thermomechanical loadings, various in situ and non-destructive techniques of characterization have been used. In this context, a Poly (Ethylene Terephthalate) (PET) amorphous and semi-crystalline was studied in order to highlight the effect of the microstructure on the macroscopic properties of the material. This way, different coupling systems combining several experimental characterization techniques have been implemented such as Raman spectroscopy and X-rays diffraction/scattering coupled to the VidéoTraction™ system or Raman spectroscopy coupled with differential scanning calorimetry (DSC) for the characterization of the deformation micro-mechanisms and the thermal behavior of the material respectively. Monitoring specific vibrational bands thoroughly identified allowed the establishment of a new robust criterion which enables to accurately measure the crystallinity ratio of the material and the identification of the characteristic temperatures of its morphology (Tg, Tc, Tcc, Tm). In addition, a relaxational characterization system by coupling dynamic dielectric spectroscopy to a tensile test has been used in order to highlight the effect of molecular mobility on the elasto-visco-plastic deformation of PET. From a mechanical point of view, the main deformation micro-mechanisms have been studied in real time during a tensile test at different temperatures and constant true strain rates: macromolecular orientation, volume damage, development of mesophase and strain induced crystallization were observed and quantified in situ using the coupled characterization technics presented previously at Petra III (Hambourg) and Elettra (Trieste) synchrotrons. In parallel, a study of the molecular mobility (a determining parameter for the predominance of one deformation micromechanism to another) was conducted via relaxational analysis performed during the deformation of the material. In addition to in situ experiments, post mortem analysis by the previously mentioned technics and by X radiography, scanning electron microscopy and X tomography were performed to assess the influence of the mechanical relaxation of the polymer

Los estilos APA, Harvard, Vancouver, ISO, etc.

6

Chaudemanche, Samuel. "Caractérisation in situ de l'endommagement volumique par Spectroscopie Raman et rayons X de différents polypropylènes déformés en traction uniaxiale". Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0263/document.

Texto completo

Resumen

L'utilisation de matériaux polymères a su s'imposer au cours du 20ième siècle, en remplaçant ou se combinant aux matériaux métalliques, pour des applications mécaniques toujours plus techniques. La grande diversité des propriétés physiques des polymères est intimement lié à leur forte complexité microstructurale, qui malgré leur utilisation massive reste, au demeurant, encore très incomprise. Afin de mieux comprendre les évolutions microstructurales aux échelles nano et micrométrique dont résultent le comportement macroscopique il est nécessaire de développer de nouvelles techniques de caractérisation in situ. Ce travail fait état de l'utilisation de la spectroscopie Raman couplée au système VidéoTractionTM afin d'obtenir des informations microstructurales de la déformation de polymère semi-cristallins. Pour cela, des polypropylènes de formulations diverses ont été étudiés, permettant de souligner le rôle joué par la matrice et les charges organiques et minérales dans le processus de déformation plastique. Des mesures in situ de l'orientation des chaînes macromoléculaires déterminées in situ par Raman ont été confirmées, au synchrotron Petra III d'Hambourg, par une expérience couplant le système VidéoTractionTM-Raman à un dispositif de diffusion des rayons X aux grands angles. L'endommagent volumique des matériaux a été étudié post mortem par Tomographie X et radiographie X. Les améliorations apportées au système VidéoTractionTM-Raman ainsi qu'une étude de la diffusion de la lumière incohérente de nos matériaux au cours de leurs déformations ont permis l'établissement d'un critère de mesure de l'endommagement volumique in situ par Raman
The use of polymer materials - replacing or combining with metallic materials - has successfully established itself in the 20th century for increasingly technical mechanical applications. The great diversity of polymers physical properties is closely related to their high microstructural complexity, which is still very misunderstood despite their massive use. The development of new techniques for in situ characterization allows to better understand the microstructural evolutions on nanoscale and micrometer scale which affect the macroscopic behavior. This work report the use of Raman spectroscopy coupled with the VideoTractionTM system in order to obtain information about the microstructural deformation of polymer. Various formulations of polypropylene were studied to highlight the role played by the polypropylene matrix and the organic and mineral fillers in the plastic deformation process. The in situ measures of the macromolecular chains' orientation determined by Raman were confirmed by the performing of an experimental setup coupling the Raman-VideoTractionTM system with a device of Wide angle X-ray scattering. The volume damage of material was studied post mortem using X-ray tomography. The improvements made to VideoTractionTM-Raman system and a study of the incoherent light scattering of our materials enabled the setting of a Raman criterion for measuring in situ the volume damage. The studies carried out to evaluate in situ macromolecular orientation and volume damage highlight the existence of competition between these two processes. The degree of influence of organic and mineral fillers in this competition within the polypropylene matrix was determined

Los estilos APA, Harvard, Vancouver, ISO, etc.

7

Babinský, Tomáš. "Rekrystalizace automatové oceli studované technikou in-situ SEM/EBSD". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378404.

Texto completo

Resumen

Placing recrystallization annealing in a manufacturing proces is often necessary in order to restore plasticity of worked blanks right before working products to its final shape. For better understanding of processes which are taking place in a material during annealing the use of in-situ techniques is favorable. Such observations enable us to watch changes in the materiál in real time at the original spot. Observations at grain-level are ideally made with scanning electron microscope – SEM by electron back-scattered diffraction – EBSD. The technique makes watching nucleation, growth and potential coarsening of recrystallized grains possible. Special construction of a tensile stage allows us to watch changes of a sample during tensile tests which can be used in observing influence of MnS inclusions on plasticity of free-cutting steels. Materials studied in this work are commonly used free-cutting steel 11SMnPb30 and its lead-free alternative 11SMnBi30.

Los estilos APA, Harvard, Vancouver, ISO, etc.

8

COUTINHO, BETANIA RODRIGUES. "CHARACTERIZATION, IN SITU TESTS, FLUORESCENCE". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2002. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2760@1.

Texto completo

Resumen

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
O tema da dissertação, Caracterização de Áreas Contaminadas Através de Ensaios in Situ, aponta o estado-da-arte dos sensores que estão sendo adaptados ao conepenetrômetro, permitindo a detecção e o registro do poluente no subsolo e lençol freático.Talvez como uma conseqüência da atual conscientização da sociedade para o caráter emergencial no enfrentamento dos problemas relacionados à contaminação do subsolo,tem-se exigido uma significativa demanda de serviços especializados na caracterização dos agentes e processos de contaminação e nos procedimentos de remediação. A pesquisa apresenta técnicas de ensaio in situ para a caracterização de áreas contaminadas em função do contaminante que se quer detectar. O primeiro grande grupo abrange as tecnologias utilizadas na detecção dos hidrocarbonetos, em seguida estão agrupadas as técnicas de detecção dos compostos orgânicos voláteis e, finalmente, o terceiro grande grupo enfoca as técnicas utilizadas na detecção de metais pesados.Neste trabalho ensaios foram feitos em duas etapas: com o LIDAR-PUC e com o Fluorímetro, e são apresentados seus resultados, bem como as conclusões da pesquisa e algumas sugestões para estudos futuros, destacando-se as potencialidades e limitações de cada ensaio realizado.
The subject of the research, Characterization of Contaminated Areas by in Situ Tests, shows the state-of-art of the sensors that are being adapted to the conepenetrometer system, allowing for the detection and register of the polluent in the subsurface and water table.Perhaps as a consequence of the new conscientization of the society about the emergencial character in facing problems related to subsurface contamination, it has been claimed such a significative demand forward specialized services in characterization of agents and contamination processes, besides remediation procedures.In situ sampling techniques for the characterization of contaminated areas related to the targeted polluents are presented in this study. The first group covers technologies used in the detection of hydrocarbons, furthermore there are some techniques for the detection of volatiles organic compounds and, finally, the third group focuses the techniques used in the detection of heavy metals. In this work tests were done in two parts: with the LIDAR- PUC and with the Fluorimeter, and their results are presented as well the conclusions of the research and some suggestions for future works, principally the potentialities and limitations of each test done.

Los estilos APA, Harvard, Vancouver, ISO, etc.

9

Rølvåg, Line Kathinka Fjellstad. "EBSD undersøkelser og in situ strekktesting av stål i SEM". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19246.

Texto completo

Resumen

Denne masteroppgaven har tatt for seg undersøkelser av stål designet for lavtemperaurappliksjoner ved bruk av elektronmikroskop i kombinasjon med diffraksjon av tilbakespredte elektroner (Electron Backscatter Diffraction - EBSD). Målet med oppgaven var å bruke EBSD-teknikken i kombinasjon med in situ deformasjon og en spesiallaget kaldfinger for å kunne studere materialene ved lave temperaturer. To ulike stål ble undersøkt; et smidd finkornet strukturelt stål (F70) og et varmvalset supermartensittisk rustfritt stål (Supermartensitic Stainless Steel - SMSS).F70-stålet ble sveisesimulert for å oppnå en mikrostruktur tilsvarende interkritisk grovkornet HAZ (Heat Affected Zone). Dette ble gjort ved en tosykel sveisesimulering. Prøvestaver av materialet ble varmet opp med en ønsket makstempertur på Tp1= 1350°C og Tp2= 780°C. For å undersøke effekten av ulike avkjølingshastigheter ble halvparten av prøvestavene avkjølt med Dt8/5 = 5 sekund, og den andre halvparten med Dt8/5 = 15 sekund. Ved sveising av stål kan det dannes lokale sprø soner som martensitt/austenitt-faser (MA-faser). Bilder tatt i lysmikroskop viser at strukturen til sveisesimulert F70-stål består av martensitt og noe bainitt. MA-faser er lokalisert langs korngrensene.EBSD-teknikken krever at materialet på forhånd gjennomgår en tilfredsstillende prøvepreparering for å gi gode resultater. Det var tidligere etablert en tilfredsstillende prepareringsteknikk for SMSS. I denne oppgaven ble to ulike prepareringsmetoder testet på sveisesimulerte prøver av F70-stål, som er et forholdsvis nytt materiale. Metodene som ble testet var ionesputtering og elektropolering. Preparerte prøver ble undersøkt med EBSD for å analysere kvaliteten på prepareringen. Det viste seg at MA-fasene reagerte annerledes på prepareringen enn resten av strukturen, og det var derfor vanskelig å få disse fram på EBSD-skann. De to prepareringsmetodene ga også forskjellige utfall for andel austenitt (g-fase) i stålet. Da det i hovedsak er MA-fasene som er interessante ved in situ undersøkelser ble det besluttet å ikke gjennomføre disse på F70-stålet, da en tilfredsstillende preparering må etableres først. Ved bruk av EBSD-teknikken kan orienteringsdataene som lagres behandles i programvaren TSL OIM Analysis 5.32, som tilbyr ulike renseoperasjoner. Grain CI Standarization gir alle punktene i et korn, innenfor en gitt vinkeltoleranse, samme CI-verdi som den maksimale CI-verdien funnet blant punktene i dette kornet. Det er også mulig å legge på et CI-filter som fjerner alle punkter med en CI ≤ 0,05, og erstatter disse med svarte eller grå piksler. Effekten av disse to operasjonene ble undersøkt på et EBSD-skann av SMSS tatt ved romtemperatur, uten noe form for deformasjon. Renseoperasjonene førte til at 8,1 % av alle punkter ble fjernet. 3,8 % av disse var av g-fasen, som utgjør kun 17,3 % av skannet før renseoperasjonene ble benyttet. Punkter som fjernes ligger i hovedsak i forbindelse med korngrenser eller øyer av restaustenitt. For SMSS som inneholder rundt 20 vol.% restaustenitt i opprinnelig (dvs. interkristisk glødet) tilstand, ble det gjennomført undersøkelser av deformasjonsindusert fasetransformasjon ved bruk av in situ strekktesting med påfølgende EBSD karakterisering. Undersøkelsene ble utført ved romtemperatur og -80°C. Et spesiallaget strekkbord ble montert på SEM (Scanning Electron Microscope) stagen med prøven fastmontert, og en kaldfinger ble brukt for å kjøle ned prøven. EBSD karakteriseringen ble foretatt uten deformasjon og ved 1, 2, 3 og 4 % forlengelse. En sammenligning av resultatene ved romtemperatur og -80°C ble deretter utført. Det ble konkludert med at øyer av restaustenitt transformeres til martensitt som følge av plastisk deformasjon i større grad ved -80°C, som følge av høyere termodynamiske drivkrefter for reaksjonen. Ved romtemperatur var det mulig å verifisere at martensitten som ble dannet oppfyller Kurdjomov-Sachs kriteriet som beviser at den er korrekt indisert. Dette var vanskelig å verifisere for lavtemperatursforsøkene, da skannene har en mye lavere kvalitet.

Los estilos APA, Harvard, Vancouver, ISO, etc.

10

Kirch, Dirk Michael. "In-situ SEM investigation of individual and connected grain boundaries in aluminum /". Göttingen : Cuvillier, 2008. http://d-nb.info/988571765/04.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

11

Martis, M. "In situ and ex situ characterization studies of transition metal containing nanoporous catalysts". Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1334587/.

Texto completo

Resumen

The research within this thesis has concentrated around characterization of nanoporous catalysts with metals incorporated or substituted inside the framework, and inside the cavities as small clusters, and in very low concentrations. The main objective has been to advance the understanding of the structure and active sites, and relate them to their catalytic properties through the use of combination in situ and ex situ methods and in some cases combination with optical spectroscopic techniques. Characterisation methods include synchrotron radiation based techniques, high-resolution powder diffraction (HRPD) and X-ray absorption spectroscopy (XAS), and laboratory based X-Ray Diffraction (XRD), Infrared Spectroscopy (IR), Raman Spectroscopy (RS), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy TEM A combination of techniques is used to investigate cobalt substituted AlPO-18 prepared by different compositions. The determination of the nature of cobalt ions, in particular their location in the samples was carried by XAS. Additionally, a new in situ IR cell was developed which allowed to determine the nature of the redox chemistry of cobalt ions in the samples. Structural changes during calcinations and methanol to olefins reaction (MTO) were studied on transition metals substituted (Co, Zn, Si) small pore AlPO-18. Using diffraction methods it was possible to accurately determine the changes in the lattice parameters and correlate this with metal ion incorporation into the lattice, and also determine the negative thermal properties of these materials prior to catalytic reactions; the study also allowed us to follow their stability during calcination. High energy X-ray diffraction (HEXRD PDF method) measurements gave an insight into the direction of possible lattice contraction during calcination which may be related to shape-selective catalytic properties of these solids. Characterization of a series of vanadium containing ZSM-5 was carried by in situ XAS and Raman spectroscopy. The catalytic activity was very different, and detailed understanding of the vanadium environment using XAS and Raman spectroscopy provided an insight into the nature of vanadium ions in the zeolites. In the last part of the thesis, a series of platinum impregnated zeolite beta and ferrierite were characterized to understand how the nano clustered platinum metal particles (active centres) were created during activation, and the study also allowed us to estimate the size and sitting of the platinum cluster inside the zeolite lattice.

Los estilos APA, Harvard, Vancouver, ISO, etc.

12

Lee, Moonyong. "In-situ morphological study of wustite scale growth in a hot stage environment SEM /". The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487266011224367.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

13

Vineis, Christopher J. (Christopher Joseph) 1974. "Characterization of OMVPE-grown GaSb-based epilayers using in situ reflectance and ex situ TEM". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8452.

Texto completo

Resumen

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001.
Includes bibliographical references (leaves 227-238).
The focus of this thesis was to investigate and characterize GaSb, GaInAsSb, and AlGaAsSb epilayers grown by organometallic vapor phase epitaxy (OMVPE). These epilayers were principally characterized using in situ spectral reflectance and ex situ transmission electron microscopy (TEM). An in situ spectral (380-1100 nm) reflectance monitoring system was designed and fitted to the OMVPE reactor. It was determined that longer wavelengths are more useful for quantitative growth rate analysis, while shorter wavelengths are more sensitive to the GaSb substrate oxide desorption process. It was also determined that the GaInAsSb and AlGaAsSb alloy compositions could be determined accurately using in situ reflectance ratios. Use of the in situ reflectance monitor to efficiently perform necessary reactor/growth calibrations was also demonstrated. Analytic functions were used to model the refractive indices of GaSb, AlGaAsSb, and GaInAsSb. Specifically, Adachi's Model Dielectric Function [1, 2] was curve-fit to data for GaSb between 400 and 1000 nm, and fourth-order polynomials were fit to data for GaSb and GaInAsSb between 1 and 3 gnm. A linear interpolation of binary functions was used to generate a refractive index model for AlGaAsSb between 1 and 3 m as a function of Al fraction. These models were helpful in interpreting in situ reflectance data, and also in designing distributed Bragg reflectors. Phase separation in GaInAsSb was studied using TEM. A wide range of microstructures was observed, from nearly homogeneous to strongly phase separated.
(cont.) It was seen that in phase separated samples, the composition modulations typically created and coupled to morphological perturbations in the surface. One interesting manifestation of the phase separation was the spontaneous formation of a natural superlattice (period typically 10-30 nm) throughout the epilayer. This superlattice had two variants: one parallel to the growth surface, and one tilted with respect to the growth surface. It was discovered that the tilted superlattice was coupled to surface to relieve surface strain associated with the superlattice ...
by Christopher J. Vineis.
Ph.D.

Los estilos APA, Harvard, Vancouver, ISO, etc.

14

Silva, Andreia Aparecida da. "Expressão das proteinas da familia PLUNC nas glandulas salivares maiores de pacientes autopsiados com AIDS em fase avançada e sem AIDS". [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288429.

Texto completo

Resumen

Orientadores: Pablo Agustin Vargas, Lynne Bingle
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
Made available in DSpace on 2018-08-13T01:09:27Z (GMT). No. of bitstreams: 1 Silva_AndreiaAparecidada_D.pdf: 22491420 bytes, checksum: 91def4321f81cbc12963ed48ee86d77d (MD5) Previous issue date: 2009
Resumo: Introdução: Inúmeras lesões de origem infecciosa, cística, neoplásica e inflamatória foram reportadas nas glândulas salivares de pacientes HIV+. Objetivos: Os objetivos deste trabalho foram analisar e comparar a resposta do sistema imune inato (proteínas da família PLUNC) em glândulas salivares maiores, provenientes de pacientes autopsiados com AIDS e sem AIDS (grupo controle) no Departamento de Patologia da Faculdade de Medicina da Universidade Estadual de São Paulo (FMUSP) no período de 1996 a 2000. Material e Métodos: Os pacientes autopsiados foram divididos em 05 grupos: grupo 01- controle (pacientes HIV negativos), grupo 02- HIV+ sem alterações nas glândulas salivares maiores, grupo 03- (micobacteriose), grupo 04 (citomegalovirose) e grupo 05 (sialadenite) para a realização de reações de imunohistoquímica para os anticorpos SPLUNC 1, SPLUNC 2 A, SPLUNC 2B e LPLUNC 1. Para o grupo controle foi realizado técnica de hibridização in situ para SPLUNC 2. Resultados: a média de idade dos pacientes selecionados para o grupo controle foi de 60,92 anos + 9,48 anos enquanto que a média de idade dos pacientes HIV positivos foi de 37,75 anos + 11,11. Nos casos de micobacteriose e citomegalovirose foi observada maior intensidade de marcação nas regiões próxima a área de infecção, quando comparada com áreas na periferia da lesão para os anticorpos SPLUNC 2 A e 2B. O anticorpo LPLUNC 1 foi positivo apenas nos ductos salivares e apresentou positividade em 42,22%, 51,06% e 63,88% para as glândulas parótida, submandibular e sublingual respectivamente. Com relação à hibridização in situ, foi observado positividade em todos os casos. Conclusão: a família de proteínas PLUNC pode ter papel fundamental na proteção dos organismos frente a agentes infecciosos, no entanto são necessários maiores estudos.
Abstract: Objectives: The aim of this study was to determine the expression of PLUNC proteins in major salivary glands (MSG) of AIDS patients with or without infectious conditions and non-HIV patients using post-mortem material. Methods: Sex, age, CD4 cell count, and clinical history were obtained retrospectively from the clinical records of all patients (n=63). We analysed the expression of PLUNCs (SPLUNC1, SPLUNC2, LPLUNC1) using immunohistochemistry in parotid (n=45), submandibular (n=47) and sublingual gland (n=37) samples of AIDS patients [30 with normal histology, 21 with mycobacteriosis, 14 with cytomegalovirus (CMV) infection, 30 with chronic nonspecific sialadenitis, and 30 HIV-negative controls. In situ hybridization (ISH) for SPLUNC2 in the MSG of the HIVnegative group was performed. Immunoreactivity was assessed as positive or negative. Results: The mean age of the patients who died of AIDS (n=63) and CD4 cell count (n=44) were 37 years and 63 cells microL(-1), respectively. The mean age of the HIV negative patients was 61 years. SPLUNC 1 expression was detected in the mucous acini of submandibular and sublingual glands, and SPLUNC2 was seen in the serous cells of the MSG. LPLUNC 1 expression was only positive in the salivary ducts of the MSG. There was a higher expression of SPLUNC2 in AIDS patients with CMV infection and mycobacteriosis when compared with all other groups. The intensity of staining for SPLUNC2 was greater around the lesions than the peripheral ones. There were no significant differences between control subjects and AIDS patients without histologic alterations or with chronic nonspecific sialadenitis. ISH for SPLUNC 2 showed perinuclear positivity in the serous cells in all HIV-negative cases. Conclusions: SPLUNC1 and LPLUNC1 proteins were similarly expressed in the MSG of AIDS patients and non-HIV patients. CMV infection and mycobacteriosis increase SPLUNC2 expression in serous cells in the MSG of AIDS patients. Further studies are needed to understand the biological processes involved in SPLUNC2 expression in the MSG infected by CMV and mycobacteriosis.
Doutorado
Patologia
Doutor em Estomatopatologia

Los estilos APA, Harvard, Vancouver, ISO, etc.

15

bin, Abdul Rahman Rushan. "Nest site selection by flatback sea turtles: Characterization of nesting beach topography with airborne LiDAR". Thesis, bin Abdul Rahman, Rushan (2018) Nest site selection by flatback sea turtles: Characterization of nesting beach topography with airborne LiDAR. Honours thesis, Murdoch University, 2018. https://researchrepository.murdoch.edu.au/id/eprint/42041/.

Texto completo

Resumen

Protecting sea turtle nesting beaches is a commonly used management strategy for sea turtle conservation as gravid sea turtles are more vulnerable to predation and disturbance during oviposition. Therefore, understanding where sea turtles nest and the characteristics of their nesting sites is fundamental for their conservation. However, the process of nest site selection is not well understood. Beach topography is one factor that is believed to drive nest site selection, but considering that many nesting beaches, particularly in Australia, are large and remote, effectively acquiring beach topographic information is challenging. Airborne light detection and ranging (LiDAR) data can obtain accurate information on beach topography and can be used to understand how topography influences nest site selection. The aims of this study were to (i) characterize beach topography using LiDAR data of Eighty Mile Beach, a remote 220 km long beach in north-west Australia, and (ii) determine which features influenced nest site selection of the flatback sea turtle (Natator depressus) population nesting there. Metrics of beach features that were believed to be relevant for nest site selection were calculated from piecewise linear regression models fitted to beach profiles extracted from transects generated along Eighty Mile Beach. Aerial photographic survey data were used to quantify flatback sea turtle nesting and were converted to presence-absence and nesting density classes per photograph. Classification tree models were used to model the influence of beach topography on the density and presence-absence of nests. Nests were predicted to be present if the highest elevation in the profile was 9 to 12 m (overall accuracy = 60%, detection rate = 80%), though density could not be modelled successfully (overall accuracy = 18%, detection rate = 80%). These results agree with the hypothesis that the silhouette in front of a sea turtle influences nest placement, though moderate model performance suggests that nest site selection by flatback sea turtles at Eighty Mile Beach are also influenced by other factors besides beach topography. The methods used in this study successfully characterized the beach topography of Eighty Mile Beach using LiDAR data and have the potential to be used on remote and large beaches in other parts of the world.

Los estilos APA, Harvard, Vancouver, ISO, etc.

16

Desai, Neil Bipinchandra. "Molecular Characterization of Ductal Carcinoma In Situ: Pilot Studies". Yale University, 2010. http://ymtdl.med.yale.edu/theses/available/etd-03242010-174328/.

Texto completo

Resumen

Ductal carcinoma in situ (DCIS); is thought directly to precede invasive breast cancer (IBC). Screening mammography has driven the incidence of this key precursor lesion to >65,000 cases per year. However, little is known about the factors controlling the natural history or risk for recurrence following treatment of a particular patients DCIS. Though the heterogeneity of the disease is well established, no histologic or demographic criteria have been able to stratify DCIS for treatment. We hypothesize that at initial diagnosis there exist biologically distinct subsets of DCIS with associated prognoses that may be recognized by molecular markers. Molecular approaches have been limited by technical design issues related to the types of tissue available for analysis, namely degraded formalin-fixed paraffin embedded (FFPE) specimens and small core biopsy samples. However, new technologies promise to overcome these issues. In the first phase of our investigation, we aimed a) to pilot feasibility studies on the use of FFPE DCIS for molecular analyses including gene expression microarray and b) to pilot feasibility study of selective, high throughput sequencing through the use of "exon capture" on small input material that simulated expected DCIS core biopsy amounts. The results of this work offer specific technical guidelines for the molecular study of DCIS. Moreover, they have enabled the initiation of the second phase of this study, which aims to assess molecular profiles of DCIS recurrence and progression.

Los estilos APA, Harvard, Vancouver, ISO, etc.

17

Seger, Eric Matthew. "In-situ electrical terminal characterization of fuel cell stacks". Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/seger/SegerE0510.pdf.

Texto completo

Resumen

This thesis demonstrates in-situ characterization of a 5kW solid oxide fuel cell (SOFC) stack and a 165W proton exchange membrane fuel cell (PEMFC) stack at the electrical terminals, using impedance spectroscopy and time-domain modeling. The SOFC experiments are performed using excitation from the power electronic ripple current and exogenous excitation generated from several different sources including a hybrid system which uses a secondary power source for the generation of the small-signal currents. The PEMFC experiments are performed using exogenous excitation from a boost converter. In contrast to typical off-line analysis using specialized instrumentation, the measurements are made as the stacks deliver power to their respective loads. The power electronic switching waveform is used as a source of excitation. This technique could be implemented on-line for continuous condition assessment of the stack. The results show typical data from the stack, comparison of model predictions and measured data, and whole-stack impedance spectroscopy results.

Los estilos APA, Harvard, Vancouver, ISO, etc.

18

Wickremesinghe, Damika Sampath. "Statistical characterization of soil profiles using in situ tests". Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/29319.

Texto completo

Resumen

Several statistical procedures that would enhance the site characterization capabilities of insitu test data with special emphasis on the cone penetrometer test have been proposed and presented. Two methods to identify different soil layers from a profile have been described. One of these procedures is based on the effects of the individual parameters, namely, cone bearing, sleeve friction and pore pressure, while the other method employs a multivariate scheme of analysis, which has the capability of handling all three or any two parameters, simultaneously. The advantages of these statistical methods over the conventional methods of soil layer identification, have also been highlighted. Critical levels of the values of the Intraclass Correlation coefficient and the D statistic have been proposed for the identification of layer boundaries as primary or secondary for both sand and clay type soils. Methods of trend analysis have been proposed while the complications arising from the presence of correlations have been discussed. The role played by methods of statistical filtering and smoothing, in the identification of trends, have also been illustrated. Statistical procedures have been proposed, for the purpose of verification of non-stationarity or stationarity, in the event it cannot be determined from a visual inspection. The need for the consideration of geotechnical data as random has been emphasized, together with applications of random field theory in the determination of exceedance probabilities of given threshold values over spatial averages of a soil layer. A computationally more convenient method for the determination of the scale of fluctuation has been proposed while emphasizing its importance in several areas of applications, with respect to the cone penetration test. Time Series methods have been employed in order to model the stationary component of soil profiles and also have been extended to obtain the measurement noise of different test methods. A comparison of the measurement noise of different insitu testing devices, obtained by the time series method has been compared to a procedure based solely on the autocorrelation function of the data, resulting in a good agreement. The relatively low value of measurement noise obtained for the cone penetration test confirms its superiority over other insitu testing methods like the field vane test which gave fairly high estimates of the measurement noise. A two dimensional interpolation procedure considering the correlation between data points has been recommended. This procedure which uses the autocorrelation function, has been applied to a set of cone penetrometer test data and the results of which have been compared with the actual profile at that location. The reasonable comparison of the predicted with the actual, clearly indicate the need for the consideration of correlations if they do exist, in interpolating geotechnical data in two or three dimensions. IBM - PC compatible interactive micro computer programs have been developed in order to perform most of the techniques proposed in the thesis. These programs cater to any type of data format and have several inbuilt options available to the user. Detailed user manuals for these programs are also available.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate

Los estilos APA, Harvard, Vancouver, ISO, etc.

19

Mills, Robert Jeffrey. "Abrasive Blasting with Post-Process and In-Situ Characterization". Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/49680.

Texto completo

Resumen

Abrasive blasting is a common process for cleaning or roughening the surface of a material prior to the application of a coating. Although the process has been in practice for over 100 years, the lack of a comprehensive understanding of the complex interactions that exist with the process can still yield an inferior surface quality. Subsequently, parts can be rejected at one of many stages of the manufacturing process and/or fail unexpectedly upon deployment. The objective of this work is to evaluate the effect of selected input parameters on the characteristics of the blasted surface characteristics so that a more useful control strategy can be implemented. To characterize surface roughness, mechanical profilometry was used to collect average roughness parameter, Ra. Decreasing blast distance from 6” to 4” gave ΔRa = +0.22 µm and from 8” to 6” gave ΔRa = +0.22 µm. Increasing blast pressure from 42 psi to 60 psi decreased the Ra by 0.33 µm. Media pulsation reduced Ra by 0.56 µm and the use of new media reduced Ra by 0.47 µm. Although blasting under the same conditions and operator on different days led to ΔRa due to shorter blast times, there was no statistically significant variance in Ra attributed to blasting on different days. Conversely, a ΔRa = +0.46 µm was observed upon blasting samples with different cabinets. No significant ΔRa was found when switching between straight and Venturi nozzles or when using different operators. Furthermore, the feasibility of fiber optic sensing technologies was investigated as potential tools to provide real time feedback to the blast machine operator in terms of substrate temperature. Decreasing the blast distance from 6” to 4” led to ΔT = +9.2 °C, while decreasing the blast angle to 45° gave ΔT= -11.6 °C for 304 stainless steel substrates. Furthermore, increasing the blast pressure from 40 psi to 50 psi gave ΔT= +15.3 °C and changing from 50 psi to 60 psi gave ΔT= +9.9 °C. The blast distance change from 8” to 6” resulted in ΔT = +9.8 °C in thin stainless steel substrate temperature. The effects of substrate thickness or shape were evaluated, giving ΔT= +7.4 °C at 8” distance, ΔT= +20.2 °C at 60 psi pressure, and ΔT= -15.2 °C at 45° blasting when comparing thin stainless steel against 304 stainless steel (thick) temperatures. No significant ΔT in means was found when going from 6” to 8” distance on 304 stainless steel, 40 psi and 60 psi blasting of thin SS, as well as angled and perpendicular blasting of thin SS. Comparing thick 304 and thin stainless steel substrates at a 6” blast distance gave no significant ΔT.
Master of Science

Los estilos APA, Harvard, Vancouver, ISO, etc.

20

Robertson, Kevin. "Characterization of nickel hydroxide sludge using the variable pressure SEM". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80865.

Texto completo

Resumen

Acid mine drainage lime treatment sludge is characterized with the variable pressure scanning electron microscope. The major components are shown to be detrital material such as silicates and clay minerals and neutralization products such as gypsum and metal hydroxides.
X-ray mapping and progressive sludge leaching experiments are performed to locate the major nickel bearing species. Progressive leaching was performed for two hours at pH 4, 3.5, and 3. It is observed that there is incomplete nickel extraction for all leach conditions. X-ray mapping establishes that the remaining nickel is due to minor amounts of Ni/S and Ni/O and more significantly colloidal sized nickel-silicon-aluminum complexes; which seem to result from neutralization.
Charge contrast imaging was also considered for characterization. It was studied on the mineral gibbsite to establish optimum working conditions for maximum contrast. Pressure, working distance, bias, scan rate and beam current are varied independently while the specimen current was monitored. Maximum contrast is shown to occur consistently at a specimen current of 3 nA. This implies that the user can operate over a wide range of conditions as long as the specimen current is maintained at its optimum value. This technique is then applied to the analysis of precipitated nickel hydroxides. Charge contrast proved not too informative because the particles are too small. Large electron doses at high magnifications can mask the subtle variation in local charging.

Los estilos APA, Harvard, Vancouver, ISO, etc.

21

Huguet-Garcia, Juan Francisco. "In situ and ex situ characterization of the ion-irradiation effects in third generation SiC fibers". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066221/document.

Texto completo

Resumen

L'utilisation des fibres SiC Tyranno SA3 (TSA3) et Hi Nicalon S (HNS) pour le renforcement de composites céramiques dédiées aux applications nucléaires impose l'étude de leur stabilité microstructurale et de leur comportement mécanique sous irradiation. La cinétique d'amorphisation des fibres a été étudiée et comparée à celle d'un matériau modèle, 6H-SiC monocristallin, sans que des différences significatives puissent être observées. La dose seuil d'amorphisation totale a été évaluée à ~0,4 dpa à température ambiante et aucune amorphisation complète n'a pas être obtenue pour des températures d'irradiation supérieures à 200 ºC. Les échantillons amorphes ont ensuite été recuits thermiquement ce qui a conduit, pour des températures élevées, à leur recristallisation mais également à une fissuration et une délamination de la zone irradiée. Ce processus d'endommagement était activé thermiquement avec une énergie d'activation de 1,05 eV. En ce qui concerne le comportement mécanique, le fluage d'irradiation des fibres TSA3 a été étudié en utilisant une machine de traction in situ implantée sur deux plateformes d'irradiation aux ions. On montre que sous irradiation ces fibres se déforment en fonction du temps avec des chargements thermique et mécanique où le fluage thermique est négligeable. Cette déformation est plus élevée pour les faibles températures d'irradiation en raison d'un couplage entre le gonflement et le fluage d'irradiation. Pour des températures voisines de 1000 ºC, le gonflement devient négligeable ce qui permet l'étude spécifique du fluage d'irradiation dont la vitesse de déformation présente une dépendance linéaire au flux d'ions
The use of Tyranno SA3 (TSA3) and Hi Nicalon S (HNS) SiC fibers as reinforcement for ceramic composites for nuclear applications requires the characterization of its structural stability and mechanical behavior under irradiation. Ion-amorphization kinetics of these fibers have been studied and compared to the model material, i.e. 6H-SiC single crystals, with no significant differences. For all samples, full amorphization threshold dose yields ~0.4 dpa at room temperature and complete amorphization was not achieved for irradiation temperatures over 200 ºC. Successively, ion-amorphized samples have been thermally annealed. It is reported that thermal annealing at high temperatures not only induces the recrystallization of the ion-amorphized samples but also causes cracking and delamination. Cracking is reported to be a thermally driven phenomenon characterized by activation energy of 1.05 eV. Regarding the mechanical irradiation behavior, irradiation creep of TSA3 fibers has been investigated using a tensile device dedicated to in situ tests coupled to two different ion-irradiation lines. It is reported that ion-irradiation (12 MeV C4+ and 92 MeV Xe23+) induces a time-dependent strain under loads where thermal creep is negligible. In addition, irradiation strain is reported to be higher at low irradiation temperatures due to a coupling between irradiation swelling and irradiation creep. At temperatures near 1000 ºC, irradiation swelling is minimized hence allowing the characterization of the irradiation creep. Irradiation creep rate is characterized by a linear correlation between the ion flux and the strain rate and square root dependence with the applied load

Los estilos APA, Harvard, Vancouver, ISO, etc.

22

Huguet-Garcia, Juan Francisco. "In situ and ex situ characterization of the ion-irradiation effects in third generation SiC fibers". Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066221.

Texto completo

Resumen

L'utilisation des fibres SiC Tyranno SA3 (TSA3) et Hi Nicalon S (HNS) pour le renforcement de composites céramiques dédiées aux applications nucléaires impose l'étude de leur stabilité microstructurale et de leur comportement mécanique sous irradiation. La cinétique d'amorphisation des fibres a été étudiée et comparée à celle d'un matériau modèle, 6H-SiC monocristallin, sans que des différences significatives puissent être observées. La dose seuil d'amorphisation totale a été évaluée à ~0,4 dpa à température ambiante et aucune amorphisation complète n'a pas être obtenue pour des températures d'irradiation supérieures à 200 ºC. Les échantillons amorphes ont ensuite été recuits thermiquement ce qui a conduit, pour des températures élevées, à leur recristallisation mais également à une fissuration et une délamination de la zone irradiée. Ce processus d'endommagement était activé thermiquement avec une énergie d'activation de 1,05 eV. En ce qui concerne le comportement mécanique, le fluage d'irradiation des fibres TSA3 a été étudié en utilisant une machine de traction in situ implantée sur deux plateformes d'irradiation aux ions. On montre que sous irradiation ces fibres se déforment en fonction du temps avec des chargements thermique et mécanique où le fluage thermique est négligeable. Cette déformation est plus élevée pour les faibles températures d'irradiation en raison d'un couplage entre le gonflement et le fluage d'irradiation. Pour des températures voisines de 1000 ºC, le gonflement devient négligeable ce qui permet l'étude spécifique du fluage d'irradiation dont la vitesse de déformation présente une dépendance linéaire au flux d'ions
The use of Tyranno SA3 (TSA3) and Hi Nicalon S (HNS) SiC fibers as reinforcement for ceramic composites for nuclear applications requires the characterization of its structural stability and mechanical behavior under irradiation. Ion-amorphization kinetics of these fibers have been studied and compared to the model material, i.e. 6H-SiC single crystals, with no significant differences. For all samples, full amorphization threshold dose yields ~0.4 dpa at room temperature and complete amorphization was not achieved for irradiation temperatures over 200 ºC. Successively, ion-amorphized samples have been thermally annealed. It is reported that thermal annealing at high temperatures not only induces the recrystallization of the ion-amorphized samples but also causes cracking and delamination. Cracking is reported to be a thermally driven phenomenon characterized by activation energy of 1.05 eV. Regarding the mechanical irradiation behavior, irradiation creep of TSA3 fibers has been investigated using a tensile device dedicated to in situ tests coupled to two different ion-irradiation lines. It is reported that ion-irradiation (12 MeV C4+ and 92 MeV Xe23+) induces a time-dependent strain under loads where thermal creep is negligible. In addition, irradiation strain is reported to be higher at low irradiation temperatures due to a coupling between irradiation swelling and irradiation creep. At temperatures near 1000 ºC, irradiation swelling is minimized hence allowing the characterization of the irradiation creep. Irradiation creep rate is characterized by a linear correlation between the ion flux and the strain rate and square root dependence with the applied load

Los estilos APA, Harvard, Vancouver, ISO, etc.

23

Tuttle, Richard W. "ELECTROSPUN ALUMINA FIBERS:SYNTHESIS AND CHARACTERIZATION". University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1164040902.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

24

Bourguignon, Thibaut. "Implémentation et évaluation de la mesure Overlay in-situ par microscopie électronique pour la production de puces électroniques". Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALT001.

Texto completo

Resumen

Les circuits intégrés sont fabriqués via un empilement de diverses couches. L’alignement précis de ces niveaux, dit « overlay (OVL)», est critique pour assurer la fiabilité des puces. Les spécifications sont très strictes : sur une plaque de 300mm de diamètre, chaque motif doit être aligné avec une précision de quelques nanomètres. Les méthodes actuelles, basées sur l'observation optique de mires dédiées, montrent leurs limites en termes de représentativité et d'évaluation de la variabilité locale.Cette thèse propose une approche novatrice, exploitant la microscopie électronique à balayage (SEM), afin de mesurer avec précision ces variations locales et d'appréhender les biais induits par les mires. Pour cela, un algorithme innovant permettant la mesure de l’overlay à partir de contours SEM a été développé. Par le recalage de contours de référence sur les contours extraits, l’overlay est mesuré directement sur le produit, nécessiter de mire spécifique, même en présence de niveaux partiellement masqués.Suite à l'évaluation de cette méthode sur des images synthétiques, son application sur des plaques de production a permis de quantifier la variabilité locale de l'overlay sur le produit, de mettre en évidence les écarts par rapport aux mesures en ligne, tout en révélant les limites de la métrologie SEM-OVL
Integrated circuits are manufactured via a stack of various layers. The precise alignment of these layers, known as "overlay" (OVL), is critical to chip reliability. The specifications are very strict: on a 300mm-diameter wafer, each pattern must be aligned to within a few nanometres. Current methods, based on optical observation of dedicated test patterns, show their limitations in terms of representativeness and assessment of local variability.This thesis proposes an innovative approach, using scanning electron microscopy (SEM), to accurately measure these local variations and to understand the biases induced by the test patterns. To this end, an algorithm for measuring the overlay from SEM contours has been developed. By registering reference contours on the extracted contours, the overlay is measured directly on the product, without the need for a specific test pattern, even in the presence of partially masked levels.Following the evaluation of this method on synthetic images, its application to production wafers enabled us to quantify the local variability of the overlay on the product, highlighting deviations from on-line measurements, while revealing the limits of SEM-OVL metrology

Los estilos APA, Harvard, Vancouver, ISO, etc.

25

Long, Renhai. "In-situ Scanning Electron Microscopy for Electron-beam Lithography and In-situ One Dimensional Nano Materials Characterization". ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/966.

Texto completo

Resumen

In this thesis, we demonstrate in-situ scanning electron microscopy techniques for both electron beam lithography (EBL) and in-situ one dimensional nano materials electrical characterization. A precise voltage contrast image positioning for in-situ EBL to integrate nanowires into suspended structures for nanoswitch fabrication has been developed. The in-situ EBL eliminates the stage movement error and field stitching error by preventing any movements of the stage during the nanolithography process; hence, a high precision laser stage and alignment marks on the substrate are not needed, which simplifies the traditional EBL process. The ZnO piezoelectronics is also studied using nano-manipulators in scanning electron microscope. Methods to improve the contact have been demonstrated and the contacts between probe tips and the nanowires are found to have significant impact on the measurement results.

Los estilos APA, Harvard, Vancouver, ISO, etc.

26

Delatolla, Robert. "Nitrifying biofilms at cold temperatures: kinetics and in-situ characterization". Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32550.

Texto completo

Resumen

The biological process of nitrification is currently the most economical and commonly employed means of removing ammonia from wastewater. Although nitrification is cost-effective and has been used in many treatment facilities in North America, the temperature sensitivity of suspended growth nitrifying bacteria is of considerable concern when designing wastewater treatment facilities in many North American cities. Notwithstanding the limited ability of suspended growth treatment systems to achieve nitrification at low temperature, there is evidence that attached growth nitrification processes have the potential to consistently achieve ammonia removal at low temperatures. The objective of this dissertation is to investigate the effect of prolonged exposure to cold temperatures on the kinetics of attached growth nitrification in wastewater treatment facilities as well as the subsequent consequences on the nitrifying bacterial community. Methodological techniques to characterize the weight, nitrogen content and volume of the biofilm along with the volume of nitrifying biomass were developed that minimize loss of mass and manipulation of the biofilm samples. Subsequently, laboratory experiments were performed on attached growth nitrifiers at 4°C. In addition, field experiments were conducted on attached growth laboratory-scale and pilot-scale treatment systems at 4°C. The laboratory experiments demonstrated significant rates of attached growth nitrification at 4°C for the approximate span of a cold climate, North American winter. Specifically, significant nitrification rates were confirmed after 115 days at 4°C. A pronounced kinetic reduction of the rate of nitrificati
À présent, le processus biologique de nitrification est le moyen le plus économique d'enlever l'ammoniaque des eaux usées. Bien que cette méthode soit utilisée dans des installations de traitement à travers l'Amérique du Nord, la sensibilité des bactéries à la température est problématique pour la conception de certaines nouvelles installations. Même si les bactéries ont une plus faible capacité de nitrification à basse température, la recherche suggère que cette méthode pourrait enlever l'ammoniaque systématiquement même à basse température. L'objectif de cette thèse était d'investiguer l'effet d'une exposition prolongée à de basses températures sur la cinétique de nitrification de bactéries fixées dans une installation de traitement, ainsi que les effets subséquents sur la communauté de bactéries. Des techniques méthodologiques pour caractériser le poids, la teneur en azote, le volume de biofilm ainsi que le volume de bactéries nitrifiantes ont été développées qui minimisent la perte de masse et la manipulation des prélèvements de biofilm. Ensuite, des expériences ont été effectuées avec une biomasse nitrifiante fixée à 4°C. De plus, des expériences de terrain ont été accomplies avec des bactéries fixées à 4°C avec des unités pilote et de laboratoire. Les expériences ont démontré des taux significatifs de croissance des bactéries fixées et de nitrification à 4°C pendant une durée correspondant à un hiver froid nord-américain. En particulier, des taux significatifs de nitrification ont été confirmés après 115 jours à 4°C. Le taux a baissé immédiatement après la période d'acclimatation et après

Los estilos APA, Harvard, Vancouver, ISO, etc.

27

Xu, Lu M. Eng Massachusetts Institute of Technology. "An improved in situ sensing device for freshwater DOM characterization". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104251.

Texto completo

Resumen

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 27-28).
DOC characterization of freshwater is poorly understood at areas of harsh or difficult to access, especially areas like peatland rainforest. In order to figure out the level of DOC transport, an in situ instrument was previously designed to measure the DOC concentration at remote locations. However, the data collected by the instrument is not as meaningful as expected due to the complex environment, high DOC concentration and inner shielding. A new instrument is required to be designed to fulfil the objectives. Like the previous instrument, the new instrument still needs to measure the fluorescence and absorbance data to give an estimation of DOC concentration. There are three LEDs to provide fluorescence measurements, a wideband lamp to provide light for absorbance measurement and a spectrometer to record the resulting spectra. Unlike general in situ fluorometers, the orientation between the excitation source and detector is 90 degrees for the new optical configuration. The new designed optical configuration solves the problem of window obstruction and also successfully prevents the problem of misalignment caused by water turbulence. Furthermore, the instrument also solves the problem of long light path lengths with the new configuration. The instrument was tested to work well in the lab with a range of DOC concentration from 5 ppm to 60 ppm. The recorded data showed a strong positive relationship between fluorescence intensity and concentration of DOC.
by Lu Xu.
M. Eng.

Los estilos APA, Harvard, Vancouver, ISO, etc.

28

Lee, Kyoung-Ho. "Synthesis and characterization of in situ whisker-reinforced glass-ceramics". Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/38638.

Texto completo

Resumen

The effects of in situ Ti0₂ whisker reinforcement on mechanical and thermal properties of glass-ceramics in the Li₂O-Al₂0₃-P₂0₆-Si0₂ system were investigated. When Ti0₂ whiskers, having an average aspect ratio of 28, are precipitated from the glass-ceramic matrix, (Li_0.4,Ca_0.05)AI(Si_{0.75>/sub>,P_0.5)_04.5, flexural strength is improved from 72 to 134 MPa. Fracture toughness, K_Ic, is increased from the 1.1 to 1.6 MPa·m^1/2 due to crack deflection by the Ti0₂ whiskers. In situ Ti0₂ whisker-reinforced glass-ceramic exhibits rising fracture resistance, K_R, with increasing crack extension. The fracture resistance, K_R, is increased from 1.89 to 2.5 MPa·m^1/2 over the crack extension range range of 40 to 200 μm. The composite shows a narrow failure strength distribution compared to the glass-ceramic without Ti0₂ whisker precipitation. The coefficient of thermal expansion (CTE) changes from -2.8x10⁻⁷/"C to -1.7xl0⁻⁷/°C due to the precipitation of Ti0₂ phase which has a positive CTE (7.3xl0⁻⁶/°C).

With the matrix composition, (Li_0.41,Mg_0.035)AI(Si₀0.48},P_O.52)O₄, a three-fold increase in flexural strength was observed with a Ti0₂ content of 12 wt%. CTE value of the composite increases linearly from a negative to a positive value with increasing Ti0₂ content up to 12 wt%. The in situ composite containing 8-10 wt% Ti0₂ exhibits near zero CTE values up to l000°C.
Ph. D.

Los estilos APA, Harvard, Vancouver, ISO, etc.

29

Deshpande, Anushree. "Synthesis and Characterization of in-situ Nylon-6/Epoxy Blends". University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1480328231030708.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

30

Bofanova, Mariia. "Optimization and ex-situ characterization of MnHCF electrodes for ZIBs". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.

Buscar texto completo

Resumen

Manganese hexacyanoferrate (MnHCF) was synthesized with a simple co-precipitation method. The slurries in 3 ratios 85/10/5, 80/10/10, 70/20/10 of active material (MnHCF)/ carbon black/ binder (PVDF) were mixed using ball miller and coated onto Al-foil. The material was characterized with TGA, MP-AES, and SEM, and through cyclic voltammetry and electrochemical impedance spectroscopy. The studied system consists of Zn-anode and MnHCF-cathode immersed in 3M ZnSO4 electrolyte. The system was tested by electrochemical techniques in the el-cell, which is a specific cell for joint electrochemical and spectroscopical studies. Experimental conditions and parameters of the el-cell performances were optimized within the testing. The pellets were prepared in the el-cell for further ex-situ monitoring of different redox stages with Raman and ATR-IR spectroscopies.

Los estilos APA, Harvard, Vancouver, ISO, etc.

31

Kail, Norbert. "Quantitative in-situ particle characterization using focused beam reflectance measurements". Düsseldorf VDI-Verl, 2009. http://d-nb.info/993097561/04.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

32

Jackson, Jarom Silver. "In Situ Magnetic Field Characterization with the Directional Hanle Effect". BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/5982.

Texto completo

Resumen

We present a novel method of in situ magnetic field mapping related to the Hanle effect. This method uses the change in spatial radiation pattern of scattered light, which we call a 'directional Hanle effect,' rather than the loss of polarization more commonly associated with the Hanle effect. It is particularly well suited for fields in a magneto-optical trap (MOT), requiring only the addition of a narrow slit and a camera to typical MOT components. The use of this method is demonstrated by measuring the gradient through, and location of, the zero-point of the field in our strontium MOT.

Los estilos APA, Harvard, Vancouver, ISO, etc.

33

Casaus, Dana M. "DSC, FTIR and SEM Characterization of As-received Colored Elastomeric Chains". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236179988.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

34

Blankemeier, Andrew R. "Characterization of Pseudomonas fluorescens Biofilm". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1307731184.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

35

MacIver, Michael Ryan. "In situ mineral sediment characterization with light scattering and image analysis". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57743.

Texto completo

Resumen

In this study, optical backscattering (OBS) and in situ image analysis are used to measure sediment bed density and aggregate size. A method is described for the measurement and interpretation of OBS height scans to obtain a measurement of aggregate size and solid concentration profiles in sediment beds of flocculated minerals. It was found that when OBS height scans were measured during batch settling and from multiple angles at the end of batch settling, the resulting root-mean-square, 𝐹rms, and mean, 𝐹mean, signal values can be analysed to quantify the sediment bed solids concentration and aggregate size as a function of height in the sample. A size calibration method was applied which relates the 𝐹rms values obtained from model solid ceramic spheres and silica particles to 𝐹rms values measured from sediment beds of flocculated kaolin. An iterative fitting method is applied to obtain a calibration function which can be applied to obtain a quantitative description of solid volume as a function of height and time during the batch settling experiment, 𝜙s(ℎ,𝑡). Evaluation of the fitted solid volume versus height functions resulted in a reasonable relative error when compared with the measured solid volume in the sample. A brief analysis on a statistical interpretation of image data for various samples of flocculated mineral sediment beds is given. This study suggests that the evaluation of OBS signal values and high magnification image analysis can be applied on the lab scale for determination of aggregate size and sediment bed density and may form the basis of a measurement system that can be applied to larger scale batch settling or pilot thickening equipment to measure rheological properties and mass flux.
Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate

Los estilos APA, Harvard, Vancouver, ISO, etc.

36

Rehan, Mohammad. "In situ hydrothermal synthesis and process characterization of titanium dioxide nanoparticles". Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582157.

Texto completo

Resumen

Hydrothermal synthesis of titanium dioxide (Ti02) nanoparticles has been studied in situ using synchrotron radiation energy dispersive X-ray diffraction (EDXRD) together with other analytical techniques. The main objective of this research study was to investigate the reaction kinetics and mechanisms of Ti02 crystallization under hydrothermal conditions. The nanoparticles have been produced from hydrothermal treatments of acid (HN03) and alkaline (tetrabutylammonium hydroxide; TBA) peptized sol-gels of different compositions at various temperatures, pressures and time durations. The in situ EDXRD spectra clearly showed that pure Ti02 anatase phase particles were crystallized from TBA peptized sol-gels, whereas pure Ti02 rutile phase particles were produced from the HN03 peptized sol-gels. The crystallization curves constructed from the EDXRD data showed that the rate of the particle formation increased with an increase in the hydrothermal process temperature for both types of sol-gel processes.

Los estilos APA, Harvard, Vancouver, ISO, etc.

37

Li, Xiaxi. "In situ characterization of electrochemical processes of solid oxide fuel cells". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54256.

Texto completo

Resumen

Solid oxide fuel cells (SOFCs) represent a next generation energy source with high energy conversion efficiency, low pollutant emission, good flexibility with a wide variety of fuels, and excellent modularity suitable for distributed power generation. As an electrochemical energy conversion device, SOFC’s performance and reliability depend sensitively on the catalytic activity and stability of the electrode materials. To date, however, the development of electrode materials and microstructures is still based largely on trial-and-error methods because of inadequate understanding of the mechanisms of the electrode processes. Identifying key descriptors/properties of electrode materials or functional heterogeneous interfaces, especially under in situ conditions, may provide guidance to the design of electrode materials and microstructures. This thesis aims to gain insight into the electrochemical and catalytic processes occurring on the electrode surfaces using unique characterization tools with superior sensitivity, high spatial resolution, and excellent surface specificity applicable under in situ/operando conditions. Carbon deposition on nickel-based anodes is investigated with in situ Raman spectroscopy and SERS. Analysis shows a rapid nucleation of carbon deposition upon exposure to small amount of propane. Such nucleation process is sensitive to the presence of surface coating (e.g., GDC) and the concentration of steam. In particular, operando analysis of the Ni-YSZ boundary indicates special function of the interface for coking initiation and reformation. The coking-resistant catalysts (BaO, BZY, and BZCYYb) are systematically studied using in situ Raman spectroscopy, SERS, and EFM. In particular, time-resolved Raman analysis of the surface functional groups (-OH, -CO3, and adsorbed carbon) upon exposure to different gas atmospheres provides insight into the mechanisms related to carbon removal. The morphology and distribution of early stage carbon deposition are investigated with EFM, and the impact of BaO surface modification is evaluated. The surface species formed as a result of sulfur poisoning on nickel-based anode are examined with SERS. To identify the key factors responsible for sulfur tolerance, model cells with welldefined electrode-electrolyte interfaces are systematically studied. The Ni-BZCYYb interface exhibits superior sulfur tolerance. The oxygen reduction kinetics on LSCF, a typical cathode material of SOFC, is studied using model cells with patterned electrodes. The polarization behaviors of these micro- electrodes, as probed using a micro-probe impedance spectroscopy system, were correlated with the systematically varied geometries of the electrodes to identify the dominant paths for oxygen reduction under different electrode configurations. Effects of different catalyst modifications are also evaluated to gain insight into the mechanisms that enhance oxygen reduction activity. The causes of performance degradation of LSCF cathodes over long term operation are investigated using SERS. Spectral features are correlated with the formation of surface contamination upon the exposure to air containing Cr vapor, H2O, and CO2. Degradation in cathode performance occurs under normal operating conditions due to the poisoning effect of Cr from the interconnect between cells and the high operating temperature. The surface-modified LSCF cathode resists surface reactions with Cr vapor that impairs electrode performance, suggesting promising ways to mitigate performance degradation.

Los estilos APA, Harvard, Vancouver, ISO, etc.

38

Chowdhury, Sudip. "Advancing characterization techniques for structure-property determination of in-situ lignocelluloses". Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/39189.

Texto completo

Resumen

The global progression towards sustainable energy, materials and chemicals requires novel and improved analytical tools to understand and optimize lignocellulosic biomass utilization. In an effort to advance lignocellulose characterization, gain insights into biomass processing, and obtain novel perspectives on cell wall ultrastructure, this study utilizes three principal polymer characterization techniques, namely compressive-torsion dynamic mechanical analysis (DMA), deuterium quadrupolar nuclear magnetic resonance (2H NMR) and rheo-infrared spectroscopy. A novel parallel-plate compressive-torsion DMA protocol is developed to analyze very small solvent-plasticized biomass specimens with or without mechanical integrity. The benefits and limitations of this technique are demonstrated by comparing it to a conventional tensile-torsion DMA while analyzing various solvent-plasticized lignocelluloses. The rheology of wood in various organic solvents is studied through dynamic thermal scans, Time/temperature superposition (TTS) and fragility analysis. Plasticizing solvents and wood grain orientation significantly affected the lignin glass-transition temperature. Dynamic TTS reveals that while all storage modulus data shift smoothly, the thermorheological complexity of solvent-plasticized wood becomes evident in loss component master curves. It is argued that the plasticized lignocellulose TTS is insightful and potentially useful, although it fails to satisfy the classic TTS validity criteria. Subsequently, it is justified that the fragility analysis is a better suited treatment than the WLF model to investigate cooperative segmental motions of plasticized wood. Deuterium quadrupolar NMR reveals a new perspective on the orientation of amorphous wood polymers and two distinct amorphous polymer domains: a highly oriented phase in the S2 layer of the secondary cell wall and an isotropic phase postulated to occur in the compound middle lamella (CML). If the origin of the isotropic phase is confirmed to arise from the CML, then this technique provides a way to independently investigate the morphology and phase dynamics of CML and S2 in an intact tissue, and should bring novel insights into deconstructive strategies specific to the oriented and unoriented domains. Finally the effects of a wood-adhesion promoter (hydroxymethyl resorcinol, HMR) on in-situ wood polymers are studied to elucidate the still unresolved HMR-lignocellulose interactions. DMA, creep-TTS and 2H NMR reveal that HMR increases the crosslink density and restricts the mobility of wood amorphous phase. Rheo-IR spectroscopy shows that the molecular stress-transfer mechanism is altered within the wood cell wall.
Ph. D.

Los estilos APA, Harvard, Vancouver, ISO, etc.

39

Wittee, Lopes Christian. "Characterization of metallic species on porous materials by in situ XAS". Doctoral thesis, Universitat Politècnica de València, 2018. http://hdl.handle.net/10251/107953.

Texto completo

Resumen

El objetivo de esta tesis es estudiar la agrupación y el crecimiento de especies metálicas confinadas o soportadas en materiales porosos mediante espectroscopia de absorción de rayos X in situ. Para lograrlo, las especies de paladio y plata se han introducido en materiales porosos (¿-alúmina, carbón activo y zeolitas) mediante impregnación vía húmeda y métodos de intercambio iónico, respectivamente. Luego, el agrupamiento de estas especies metálicas se ha controlado mediante tratamientos de activación en diferentes atmósferas (inerte, oxidativa y reductiva) y seguido por XAS de manera detallada. El objetivo principal del trabajo actual es demostrar que tanto XANES como EXAFS pueden proporcionar información valiosa y, en cierto punto, innovadora durante el control de especies metálicas (en términos de tipo y tamaño de las especies). Aprovechando los procedimientos de análisis inusuales, como el análisis de los cumulantes, el ajuste de la parte imaginaria de la transformada de Fourier y otros, es posible obtener información refinada sobre los sistemas investigados. En la sección de introducción, se proporciona una compilación de estudios en los que se ha utilizado XAS como técnica importante para caracterizar especies metálicas en materiales porosos. Conscientes de que las personas pueden usar dicha introducción como base para estudios más complejos en el futuro, la discusión se ha dirigido tentativamente hacia este objetivo. El capítulo 4 se centra en el estudio de la influencia de los precursores de paladio y la naturaleza del soporte en las nanopartículas resultantes. El proceso de activación completo, es decir, la transformación precursor --> nanopartícula, ha sido seguido por XAS in situ. El análisis estuvo compuesto por el punto de partida (material impregnado), calcinación en flujo de O2 y reducción posterior con H2. La consecuencia del uso de diferentes precursores metálicos y soportes se ha discutido en términos del número de coordinación promedio obtenido a partir del análisis de datos de EXAFS, que fue respaldado por técnicas de caracterización de laboratorio. El capítulo 5 está dedicado al estudio de la agrupación de plata durante y después de los tratamientos de activación utilizando zeolitas de poro pequeño intercambiadas con plata como precursores y nanocontenedores. Se ha estudiado la influencia de la estructura y la composición química de los materiales basados en plata sobre las especies metálicas formadas en diferentes condiciones de agrupamiento y redispersión del metal (calcinación usando atmósferas distintas, reducción en H2, redispersión en O2) utilizando métodos de caracterización in situ o ex situ. Después, se discuten las consecuencias catalíticas de las zeolitas que contienen Ag en la reacción de SCO-NH3. En esta sección, la combinación de XAS in situ con varias técnicas de laboratorio ha demostrado ser fundamental para un completo entendimiento del trabajo. Finalmente, una lista de proyectos desarrollados en paralelo a esta tesis se proporciona al final de este documento.
The aim of this thesis is to study the clustering and growth of metallic species either confined or supported in porous materials by in situ X-ray absorption spectroscopy. To accomplish this task, palladium and silver species were introduced into porous materials (¿-alumina, activated carbon and zeolites) by wetness impregnation and ion-exchange methods, respectively. Then, the clustering of these metallic species was controlled by activation treatments in different atmospheres (inert, oxidative and reductive) and followed by XAS in a comprehensive way. The principal goal of current work is to demonstrate that both XANES and EXAFS can provide valuable and, at certain point, innovative information during tuning of metallic species (in terms of type and size). Taking advantage of unusual analysis procedures, such as cumulant approach, fitting of imaginary part of Fourier transform and others, it is possible to obtain refined information about the investigated systems. In the introduction section, a compilation of studies in which XAS was used as important technique to characterize metallic species in porous materials is provided. Conscious that people can use such introduction as a basis for more complex studies in the future, the discussion has been tentatively directed toward this goal. The chapter 4 is focused on the study of the influence of palladium precursors and the nature of support on the resultant nanoparticles. The whole activation process, i.e. the transformation precursor --> nanoparticle, was followed in situ by XAS. The analysis pathway was composed by the starting point (as-impregnated), calcination in O2 flow and posterior reduction with H2. The consequence of using distinct metal precursors and supports were discussed in terms of average coordination number obtained from EXAFS data analysis, which was co-supported by laboratory characterization techniques. The chapter 5 is dedicated to the study of silver clustering during and after activation treatments using Ag-containing small-pore zeolites as precursors and nanocontainers. The influence of framework structure and chemical composition of Ag-based materials on formed Ag species at different clustering and metal redispersion conditions (calcination using distinct atmospheres, reduction in H2, redispersion in O2) were studied using either in situ or ex situ characterization methods. After, the catalytic consequences of tuned Ag-containing zeolites in SCO-NH3 are discussed. In this section, the combination of in situ XAS with several laboratory techniques proved to be pivotal to have a full picture of the investigated system. Finally, a list of projects developed in parallel to this thesis is provided at the end of this document.
L'objectiu d'aquesta tesi és estudiar l'agrupació i el creixement d'espècies metàl·liques confinades o suportades en materials porosos mitjançant espectroscòpia d'absorció de raigs X in situ. Per a això, les espècies de pal·ladi i plata s'han introduït en materials porosos (¿-alúmina, carbó activat i zeolites) per mitjà de la impregnació via humida i mètodes d'intercanvi iònic, respectivament. Una vegada preparats els materials, l'agrupament de les espècies metàl·liques s'ha controlat fent ús de tractaments d'activació en diferents atmosferes (inert, oxidant i reductora) s'ha estudiat exhaustivament per XAS. L'objectiu principal del treball és demostrar que tant el XANES com l'EXAFS proporcionen informació rellevant i, en certa manera, innovadora per al control d'espècies metàl·liques (en termes de tipus i grandària d'aquestes espècies). Fent ús de procediments de tractament de dades no molt habituals com l'anàlisi de cumulants, l'ajust de la part imaginària de la transformada de Fourier i altres, és possible obtenir informació detallada sobre els sistemes estudiats. En l'apartat de la introducció, es proporciona una recopilació d'estudis en els quals s'ha utilitzat XAS com a tècnica principal per a caracteritzar les anomenades espècies metàl·liques en materials porosos. Aquesta introducció ha estat redactada per a que puga servir com a punt de partida per a futurs estudis que requereixen la utilització de XAS per a la caracterització de les espècies metàl·liques presents en els catalitzadors. El capítol 4 es centra en l'estudi de la influència dels precursors de pal·ladi i la naturalesa del suport front a les nanopartícules resultants. El procés d'activació, és a dir, la transformació precursor --> nanopartícula, ha sigut estudiat per XAS in situ. L'anàlisi per XAS va comprendre els següents passos: punt de partida (material impregnat), calcinació en flux d'O2 i reducció posterior amb H2. La utilització de diferents precursors i suports metàl·lics ha permès dur a terme una discussió, referent al nombre de coordinació mitjà obtingut a partir de l'anàlisi de dades de la zona EXAFS, que ha estat recolzat per altres tècniques de caracterització. El capítol 5 s'ha dedicat a l'estudi de l'agrupació de plata intercanviada en els catalitzadors durant i després dels tractaments d'activació. S'han utilitzat zeolites de porus xicotet, com la CHA i RHO, intercanviades amb plata. L'estudi de la influència de l'estructura zeolítica i la composició química dels materials enfront dels diferents tractaments d'activació (calcinació utilitzant diferents atmosferes, reducció en presència d'H2, re-dispersió en atmosfera d'O2) es va realitzar fent ús de mètodes de caracterització in situ o ex situ. A continuació, es discuteix la influència d'aquestes espècies metàl·liques formades, utilitzant els diferents mètodes d'activació, per a la reacció d'SCO-NH3. En aquest sentit, s'ha demostrat que la combinació de XAS in situ amb diverses tècniques habituals de laboratori és fonamental per al desenvolupament d'aquest treball. Finalment, es presenta una llista de projectes, en els quals també s'ha treballat paral·lelament, on s'ha utilitzat XAS com a tècnica de caracterització.
Wittee Lopes, C. (2018). Characterization of metallic species on porous materials by in situ XAS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/107953
TESIS

Los estilos APA, Harvard, Vancouver, ISO, etc.

40

Simeone, Felice Carlo. "Local characterization and modification of surfaces with the in-situ STM". [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-64065.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

41

Zobell, Brock Don. "In Situ Characterization of Voids During Liquid Composite Molding". BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6557.

Texto completo

Resumen

Global competition is pushing the composites industry to advance and become more cost effective. Liquid Composite Molding or LCM is a family of processes that has shown significant promise in its potential to reduce process times and cost while maintaining high levels of part quality. However, the majority of research and information on composite processes have been related to prepreg-autoclave processing which is significantly different than LCM. In order for LCM processes to gain large scale implementation, significant research is required in order to model and simulate the unique nature of the resin infusion process. The purpose of this research is to aid in the development of in situ void measurement and characterization during LCM processing, particularly for carbon fiber composites. This will allow for the gathering of important empirical data for the validation of models and simulations that aid in the understanding of void formation and movement during LCM. For such data to be useful, it needs to include details on the formation, mobility and evolution of the void over time during infusion. This was accomplished by creating a methodology that allowed for in situ images of voids to be captured during the infusion process. A clear mold was used to visually monitor infusions during RTM with UV dye and lighting to enhance contrast. Consecutive images were acquired through the use of macro lens photography. This method proved capable of yielding high quality images of a variety of in situ voids during infusions with carbon fiber composites. This is believed to be the first instance where this was accomplished. A second methodology was then developed for the analysis of the collected images. This was done by using ImageJ software to analyze and process the acquired images in order to identify and characterize the voids. Success was found in quantifying the size and circularity of a wide range of micro and macrovoids in both a satin weave and double bias NCF woven fabrics. To facilitate the burden of collecting large amounts of data, this process was made to be automated. A user generated macro script could be applied to large sets of images for rapid processing and analysis. This automated method was then evaluated against manually processed images to determine its overall effectiveness and accuracy as tool for validating void theory.

Los estilos APA, Harvard, Vancouver, ISO, etc.

42

Perez, Toralla Karla. "Microfluidic systems for in situ molecular characterization of circulating tumor cells". Paris 7, 2013. http://www.theses.fr/2013PA077121.

Texto completo

Resumen

L'analyse de cellules tumorales circulantes (CTCs) dans le sang des patients atteints de cancer représente aujourd'hui une procédure non invasive pour évaluer le risque de récidive. Les CTCs semblent avoir une valeur pronostic importante mais leur caractérisation reste limitée à cause de leur extrême rareté (généralement une par milliard de cellules sanguines). Ce projet de recherche vise à développer une plateforme microfluidique dédiée à la capture et l'analyse moléculaire des CTCs. Nous nous sommes d'abord intéressés au développement de nouveaux outils pour la microfabrication de puces en matériaux thermoplastiques. Nous avons élaboré des structures complexes à haute résolution de manière reproductible, avec une faible rugosité de surface. Nous avons développé des stratégies de revêtements de surface pour contrôler l'absorption non spécifique de biomolécules à la surface de canaux hydrophobes faits en COC (Cyclo olefin copolymer). Pour détecter des modifications géntiques et chromosomiques dans les cellules cancéreuses, nous avons implémenté la technique de FISH (hybridation in situ en fluorescence) à l'intérieur de la puce en COC et optimisé les différentes étapes du protocole pour les rendre compatibles avec le format microfluidique et l'utilisation de microparticules magnétiques. Nous avons étudié l'amplification du gène HER-2 sur différentes lignées cellulaires et sur des échantillons cliniques pertinents, avec des résultats comparables au protocole classique sur lame de verre. Les développements futurs seront axés sur l'analyse par FISH des CTC capturés, à l'intérieur de notre microsystème de tri cellulaire, en combinaison avec de nouveaux outils de diagnostic
Tha analysis of circulating tumour cells (CTCs) from blood of cancer patients appears today as a non invasive procedure to monitor metastatic disease. As they represent a marker of therapeutic response, CTCs may provide clinicians with valuable prognostic information. Due to their extreme rarity (typically one per billion blood cells) the selective capture and characterization of CTCs remains challenging. The framework of this project is to develop a fully integrated microfluidic platform for high throughput sorting and molecular analysis of CTCs from raw biological samples. The complex design and multidimensional structures of our system required to produce new flexible master molds for the microfabrication of thermoplastic polymers, achieving high resolution and replication fidelity with low surface roughness. A key issue has been to control the surface properties of the hydrophobic channels, made with Cyclo Olefin Copolymer (COC), to prevent the non specific adsorption of biomolecules. To detect genetic and chromosomal alterations in cancer cells, we implement the Fluorescence in situ Hybridization (FISH) technique inside the COC chip and optimized the different steps of the protocol to make them compatible with the microfluidic format and the use of magnetic microparticles. We validated the feasibility of the entire FISH protocol for HER-2 gene amplification using different cell lines and relevant clinical samples, showing similar results as compared to the conventional protocol on glass slides. Future work will be focused on performing FISH analysis directly on captured CTCs inside our cell sorting microfluidic platform ant to combine it with novel diagnosis tools

Los estilos APA, Harvard, Vancouver, ISO, etc.

43

Amadi, F. C. "Integration of nano CT and SEM in the characterization of Marcellus shale". Thesis, University of Salford, 2016. http://usir.salford.ac.uk/40106/.

Texto completo

Resumen

Shale has proven to be a major unconventional natural gas play. However, due to its complex bedding orientations, comparatively high clay content and its complex heterogeneity, producing and optimising production is often hindered by its challenging complexities. It is now imperative to critically understand the complexities surrounding the geology of Shale reservoirs and its characterization. The overall aim of this study is to understand and characterise the Marcellus shale with the view of enhancing our knowledge of the geometry and topology of the tight shale rock. This study presents a simplified workflow in the study of the heterogeneity of shale rock sample by the combination of Nano CT imaging and Scanning Electron Microscopy imaging methodologies. The key components involve the uses of an appropriate sample preparation technique and application of complex imaging algorithm in digitising the shale sample and 3dimension image analysis for improved gas recovery. Full networks with parameterised topology have been generated on the scanned images. In this study the measured porosity is 4.73% and calculated porosity is 4.92%. Therefore the average porosity of the Marcellus shale derived in is study is 4.83% .The network predicted absolute permeability at cross points of the correlations; both correlation combinations gave a similar water saturation value of 0.533 while the relative permeability using the Corey/Skjaeveland was 0.044 and Sigmund Mccaffery/Benstine Anli was 0.047. The Nano CT scans were used for both determination of the static petro physical properties-porosity and visualisation of the sample. The SEM was used to discretise the morphology. The integration of Nano CT reconstruction and SEM imaging modalities presented in this study is a new technique in the characterisation of tight formations at a core scale. This technique carried out in the discretization of unconventional/shale reservoirs will not only help in providing understanding onto the complex geometry of tight reservoirs but also provide intricate insight into understanding adaptable optimum production techniques through flow behavioural analysis and characterisation.

Los estilos APA, Harvard, Vancouver, ISO, etc.

44

Ericsson, Leif KE. "Growth and Characterization of ZnO Nanocrystals". Doctoral thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-27156.

Texto completo

Resumen

The understanding of surfaces of materials is of crucial importance to all of us. Considering nanocrystals (NCs), that have a large surface to bulk ratio, the surfaces become even more important. Therefore, it is important to understand the fundamental surface properties in order to use NCs efficiently in applications. In the work reported in this thesis ZnO NCs were studied. At MAX-lab in Lund, synchrotron radiation based Spectroscopic Photoemission and Low Energy Electron Microscopy (SPELEEM) and X-ray Photoelectron Spectroscopy (XPS) were used. At Karlstad University characterization was done using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Scanning Tunnelling Microscopy (STM), Auger Electron Spectroscopy (AES), and XPS. The fundamental properties of ZnO surfaces were studied using distributions of ZnO NCs on SiO2/Si surfaces. The conditions for distribution of ZnO NCs were determined to be beneficial when using ethanol as the solvent for ultrasonically treated dispersions. Annealing at 650 °C in UHV cleaned the surfaces of the ZnO NCs enough for sharp LEEM imaging and chemical characterization while no sign of de-composition was found. A flat energy band structure for the ZnO/SiO2/Si system was proposed after 650 °C. Increasing the annealing temperature to 700 °C causes a de-composition of the ZnO that induce a downward band bending on the surfaces of ZnO NCs. Flat ZnO NCs with predominantly polar surfaces were grown using a rapid microwave assisted process. Tuning the chemistry in the growth solution the growth was restricted to only plate-shaped crystals, i.e. a very uniform growth. The surfaces of the NCs were characterized using AFM, revealing a triangular reconstruction of the ZnO(0001) surface not seen without surface treatment at ambient conditions before. Following cycles of sputtering and annealing in UHV, we observe by STM a surface reconstruction interpreted as 2x2 with 1/4 missing Zn atoms.
Baksidestext The understanding of the surfaces of materials is of crucial importance to all of us. Considering nanocrystals (NCs), that have a large surface to bulk ratio, the surfaces become even more important. In the work in this thesis ZnO NCs were studied. The fundamental properties of ZnO surfaces were studied using distributions of ZnO NCs on SiO2/Si surfaces. Annealing at 650 °C in UHV cleaned the surfaces of the ZnO NCs enough for sharp LEEM imaging and chemical characterization while no sign of de-composition was found. A flat energy band structure for the ZnO/SiO2/Si system was proposed after 650 °C. Increasing the annealing temperature to 700 °C causes a de-composition of the ZnO that induce a downward band bending on the surfaces of ZnO NCs. Flat ZnO NCs with predominantly polar surfaces were grown using a microwave assisted process. Tuning the chemistry in the growth solution the growth was restricted to only plate-shaped crystals, i.e. a very uniform growth. The surfaces of the NCs were characterized using AFM, revealing a triangular reconstruction of the ZnO(0001) surface not seen without surface treatment at ambient conditions before. Following cycles of sputtering and annealing in UHV, we observe by STM a surface reconstruction interpreted as 2x2 with 1/4 missing Zn atoms.

Los estilos APA, Harvard, Vancouver, ISO, etc.

45

Webster, Matthew R. "Material Characterization of Insect Tracheal Tubes". Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/71708.

Texto completo

Resumen

The insect respiratory system serves as a model for both robust microfluidic transport and mate- rial design. In the system, the convective flow of gas is driven through local deformations of the tracheal network, a phenomenon that is dependent on the unique structure and material properties of the tracheal tissue. To understand the underlying mechanics of this method of gas transport, we studied the microstructure and material properties of the primary thoracic tracheal tubes of the American cockroach (Periplaneta americana). We performed quasi-static uniaxial tests on the tissue which revealed a nonlinear stress-strain response even under small deformations. A detailed analysis of the tissue's microstructural arrangement using both light and electron mi- croscopy revealed the primary sources of reinforcement for the tissue as well as heterogeneity on the meso-scale that may contribute to the physiological function of the tracheae during respi- ration. Finally, a custom mechanical testing system was developed with which inflation-extension tests on the tracheae were used to gather data on the biaxial elastic response of the tissue over a wide range of physiologically relevant loading conditions. From information gathered about the material microstructure, a robust constitutive model was chosen to quantify the biaxial response of the tracheae. This model will provide a basis from which to simulate the behavior of tracheal net- works in future computational studies. This study gives the first description of the elastic response of the tracheae which is essential for understanding the mechanics of respiration in insects. Thus it brings us closer to the realization of novel bio-inspired microfluidic systems and materials that utilize mechanical principles from the insect respiratory system.
Ph. D.

Los estilos APA, Harvard, Vancouver, ISO, etc.

46

Wang, Zixi. "Characterization of Friction-stir Riveting AA5754". University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1416509557.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

47

Sætran, Truls Gruben. "Utvikling av metode for bråkjøling i SEM og in situ EBSD-karakterisering av fasetransformasjoner i F 70 stål". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19376.

Texto completo

Resumen

Fasetransformasjoner som skjer ved sveising av F 70 arktisk stål fører til at ugunstige mikrostrukturer oppstår i den varmepåvirkede sonen av grunnmaterialet (HAZ). Ved gjentatt oppvarming av HAZ vil det kunne dannes områder med martensitt/austenitt-fase (MA-fase) langs tidligere austenittkorngrenser. For at den karakteristiske mikrostrukturen som er forbundet med sveising skal kunne oppstå kreves det en rask nedkjøling fra tofaseområdet for stål. Teknikken med å skanne overflaten av en prøve for å ta opp diffraksjonsmønster fra tilbakesprette elektroner (EBSD-teknikken) i SEM, er tidligere blitt brukt for å karakterisere framveksten av austenitt under oppvarming av stål til tofaseområdet. Da det er vakuum i SEM under kjøring vil prøver kjøles sakte ned. Det er aldri før blitt gjort in situ –forsøk på å bråkjøle stål fra tofaseområdet i SEM. Det har derfor ikke vært mulig å studere effektene bråkjøling har på dannelsen av mikrostrukturer som er avhengig av rask nedkjøling, deriblant dannelsen av MA-fase. For å EBSD-karakterisere dannelsen av MA-fase ble en metode for bråkjøling i SEM utviklet. Ved bruk av metoden for bråkjøling i SEM ble det oppnådd en kjølehastighet på ca. 40 oC/s. Dette var tilstrekkelig rask kjøling til å danne MA-faser ved bråkjøling av F 70-stål. Under in situ-forsøkene ble prøver varmet til tofaseområdet for ferritt og austenitt og holdt ved en temperatur i tofaseområdet i 5 minutter før EBSD-skann ble gjort. Prøver som ble varmet for høyt opp i tofaseområdet fikk så store forandringer i mikrostrukturen at mikrostrukturen før oppvarming og etter bråkjøling ikke var sammenliknbar. Da det viste seg vanskelig å måle en pålitelig temperaturen på varme prøver, var det vanskelig å finne en temperatur som gav en mengde austenitt som gjorde det mulig å sammenlikne in situ oppvarmede prøver med tosykel sveisesimulerte prøver. Målet for denne oppgaven var å utvikle et kjølesystem som gir tilstrekkelig rask kjøling for å oppnå sveisesimulering. Det var også viktig å oppnå en mikrostruktur som er lik den som oppstår ved sveisesimulering. En gunstig holdetemperatur måtte derfor finnes ved prøving og feiling.Prøver som ble varmet like over A1 –temperaturen for F 70-stål fikk MA-faser langs tidligere austenittkorngrenser etter bråkjøling. På grunn av holdetid i tofaseområdet ble framveksten av austenitt større ved in situ-forsøk enn ved sveisesimulering. Morfologien av MA-fasen som dannes fra in situ-forsøk ble derfor forskjellig fra de som observeres i tosykel sveisesimulerte prøver.Austenitten som vokser fram i tofaseområdet oppfyller K-S-orienteringssammenheng med BCC-strukturen inne i tidligere austenittkorn. Austenitten er derfor riktig indisert og ikke en artifakt.Ved oppvarming av prøver var det mulig å benyttes dobbelt så høy skannhastighet i forhold til før oppvarming. Dette gjør at større områder av oppvarmede prøver kunne skannes uten å bruke lang tid.

Los estilos APA, Harvard, Vancouver, ISO, etc.

48

Vedantham, Vikram. "In-situ temperature and thickness characterization for silicon wafers undergoing thermal annealing". Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/1181.

Texto completo

Resumen

Nano scale processing of IC chips has become the prime production technique as the microelectronic industry aims towards scaling down product dimensions while increasing accuracy and performance. Accurate control of temperature and a good monitoring mechanism for thickness of the deposition layers during epitaxial growth are critical parameters influencing a good yield. The two-fold objective of this thesis is to establish the feasibility of an alternative to the current pyrometric and ellipsometric techniques to simultaneously measure temperature and thickness during wafer processing. TAP-NDE is a non-contact, non-invasive, laser-based ultrasound technique that is employed in this study to contemporarily profile the thermal and spatial characteristics of the wafer. The Gabor wavelet transform allows the wave dispersion to be unraveled and the group velocity of individual frequency components to be extracted from the experimentally acquired time waveform. The thesis illustrates the formulation of a theoretical model that is used to identify the frequencies sensitive to temperature and thickness changes. The group velocity of the corresponding frequency components is determined and their corresponding changes with respect to temperature for different thickness are analytically modeled. TAP-NDE is then used to perform an experimental analysis on Silicon wafers of different thickness to determine the maximum possible resolution of TAP-NDE towards temperature sensitivity, and to demonstrate the ability to differentiate between wafers of different deposition layer thickness at temperatures up to 600?C. Temperature resolution is demonstrated for ?10?C resolution and for ?5?C resolution; while thickness differentiation is carried out with wafers carrying 4000? and 8000? of aluminum deposition layer. The experimental group velocities of a set of selected frequency components extracted using the Gabor Wavelet time-frequency analysis as compared to their corresponding theoretical group velocities show satisfactory agreement. As a result of this work, it is seen that TAP-NDE is a suitable tool to identify and characterize thickness and temperature changes simultaneously during thermal annealing that can replace the current need for separate characterization of these two important parameters in semiconductor manufacturing.

Los estilos APA, Harvard, Vancouver, ISO, etc.

49

Parasuraman, Jayalakshmi. "Characterization of dynamically-etched nanoprobe arrays for in-situ needle-type sensors". Cincinnati, Ohio : University of Cincinnati, 2007. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1172860665.

Texto completo

Resumen

Thesis (M.S.)--University of Cincinnati, 2007.
Title from electronic thesis title page (viewed Apr.20, 2007). Includes abstract. Keywords: Nanoprobes, Microelectrodes, In situ, sensors, meniscus etching Includes bibliographical references.

Los estilos APA, Harvard, Vancouver, ISO, etc.

50

Reddi, Rahul. "In-situ characterization of Li-ion battery electrodes using atomic force microscopy". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524215477787917.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

Tesis sobre el tema "In situ SEM characterization"

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros