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Neumann, Stephan, Georg Jacobs, Achim Feldermann, and Felix Straßburger. "Reducing Friction and Leakage by Means of Microstructured Sealing Surfaces – Example Mechanical Face Seal." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-199867.
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By defined structuring of sliding surfaces at dynamic contact seals friction and leakage can be reduced. Compared to macro-structures, micro-structures have the advantage of a quasi-homogeneous influence on the fluid behavior in the sealing gap. The development of suitable microstructures based on prototypes, whose properties are studied on the test bench, is very expensive and time-consuming due to the challenging manufacturing process and measuring technologies, which are necessary to investigate the complex rheological behavior within the sealing gap. A simulation-based development of microstructured sealing surfaces offers a cost- and time-saving alternative. This paper presents a method for simulative design and optimization of microstructured sealing surfaces at the example of a microstructured mechanical face seal.
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Yang, Zhugen. "3D-Microstructured Protein Chip for Cancer Diagnosis." Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00780192.
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Protein microarrays are becoming powerful tools to screen and identify tumor markers for cancer diagnosis, because of the multiplex detection and minute volume of sample requirement. Due to the diversity and variation in different cancers, no single tumor marker is sensitive and specific enough to meet strict diagnostic criteria. Therefore, a combination of tumor markers is required to increase sensitivity and to establish distinct patterns to increase specificity. To obtain reliable tests, the development of reproducible surface chemistry and immobilization procedure are crucial steps in the elaboration of efficient protein microarrays. In this thesis, 3D micro-structured glass slides were functionalized with various surface chemistries like silane monolayer (amino, epoxy and carboxy), and polymer layers of Jeff amine, chitosan, carboxymethyl dextran (CMD), maleic anhydride-alt-methyl vinyl ether copolymer (MAMVE) for physical adsorption or covalent binding with proteins. Surface characterizations, such as X-ray photoelectron spectroscopy (XPS) and Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), confirmed the monolayer/polymer grafting on the glass slides. Colorimetric assay for determining amine density of three aminated surfaces demonstrated that APDMES had more grafting density than Jeffamine and chitosan. Contact angle measurements show that polymer surfaces were more hydrophilic than monolayer surfaces due to the increasing dosages of polar functional groups. Moreover, the parameters such as additives and pH of spotting buffer, probe concentration, blocking procedures etc, were optimized for tumor marker detection. Under the optimized conditions, antibody microarrays were validated with purified tumor antigens. The best analytical performances obtained for each tumor antigen tested were strongly dependent on functionalized surfaces, e.g. MAMVE exhibited best analytical performances for CEA andHsp60 while NHS leads to best results for PDI and CA19-9. Besides, the implemented antibody microarrays were applied to tumor marker detection from colorectal cancer sera. This evaluation shows the interest to combine several tumor markers on the same surface and the combination of tumor markers on their specific surface lead to remarkably increase the positive responses of tested cancer sera (even up to 100 %). A second type of microarrays (tumor-associated antigens - TAA microarrays) was designed to discriminate breast cancer patients from healthy donors through the detection of tumor autoantibodies. This study included a cohort of 29 breast cancer patients' and 28 healthy donors' sera. A panel of fiveTAAs (Hsp60, p53, Her2, NY-ESO-1 and Hsp70) immobilized on their respective optimized surface chemistry allowed to specifically detect over 82% of breast cancer patients.
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Zhang, Bo. "Magnetic fields near microstructured surfaces : application to atom chips." Phd thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2009/2898/.
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Microfabricated solid-state surfaces, also called atom chip', have become a well-established technique to trap and manipulate atoms. This has simplified applications in atom interferometry, quantum information processing, and studies of many-body systems. Magnetic trapping potentials with arbitrary geommetries are generated with atom chip by miniaturized current-carrying conductors integrated on a solid substrate. Atoms can be trapped and cooled to microKelvin and even nanoKelvin temperatures in such microchip trap. However, cold atoms can be significantly perturbed by the chip surface, typically held at room temperature. The magnetic field fluctuations generated by thermal currents in the chip elements may induce spin flips of atoms and result in loss, heating and decoherence. In this thesis, we extend previous work on spin flip rates induced by magnetic noise and consider the more complex geometries that are typically encountered in atom chips: layered structures and metallic wires of finite cross-section. We also discuss a few aspects of atom chips traps built with superconducting structures that have been suggested as a means to suppress magnetic field fluctuations. The thesis describes calculations of spin flip rates based on magnetic Green functions that are computed analytically and numerically. For a chip with a top metallic layer, the magnetic noise depends essentially on the thickness of that layer, as long as the layers below have a much smaller conductivity. Based on this result, scaling laws for loss rates above a thin metallic layer are derived. A good agreement with experiments is obtained in the regime where the atom-surface distance is comparable to the skin depth of metal.
Since in the experiments, metallic layers are always etched to separate wires carrying different currents, the impact of the finite lateral wire size on the magnetic noise has been taken into account. The local spectrum of the magnetic field near a metallic microstructure has been investigated numerically with the help of boundary integral equations. The magnetic noise significantly depends on polarizations above flat wires with finite lateral width, in stark contrast to an infinitely wide wire. Correlations between multiple wires are also taken into account. In the last part, superconducting atom chips are considered. Magnetic traps generated by superconducting wires in the Meissner state and the mixed state are studied analytically by a conformal mapping method and also numerically. The properties of the traps created by superconducting wires are investigated and compared to normal conducting wires: they behave qualitatively quite similar and open a route to further trap miniaturization, due to the advantage of low magnetic noise. We discuss critical currents and fields for several geometries.Mikrotechnologische Oberflächen, sogenannte Atomchips, sind eine etablierte Methode zum Speichern und Manipulieren von Atomen geworden. Das hat Anwendungen in der Atom-Interferometrie, Quanteninformationsverarbeitung und Vielteilchensystemen vereinfacht. Magnetische Fallenpotentiale mit beliebigen Geometrien werden durch Atomchips mit miniaturisierten stromführenden Leiterbahnen auf einer Festkörperunterlage realisiert. Atome können bei Temperaturen im $mu$ K oder sogar nK-Bereich in einer solchen Falle gespeichert und gekühlt werden. Allerdings können kalte Atome signifikant durch die Chip-Oberfläche gestört werden, die sich typischerweise auf Raumtemperatur befindet. Die durch thermische Ströme im Chip erzeugten magnetischen Feldfluktuationen können Spin-Flips der Atome induzieren und Verlust, Erwärmung und Dekohärenz zur Folge haben. In dieser Dissertation erweitern wir frühere Arbeiten über durch magnetisches Rauschen induzierte Spin-Flip-Ratenund betrachten kompliziertere Geometrien, wie sie typischerweise auf einem Atom-Chip anzutreffen sind: Geschichtete Strukturen und metallische Leitungen mit endlichem Querschnitt. Wir diskutieren auch einige Aspekte von Aomchips aus Supraleitenden Strukturen die als Mittel zur Unterdrückung magnetischer Feldfluktuationen vorgeschlagen wurden. Die Arbeit beschreibt analytische und numerische Rechnungen von Spin-Flip Raten auf Grundlage magnetischer Greensfunktionen. Für einen Chip mit einem metallischen Top-Layer hängt das magnetische Rauschen hauptsächlich von der Dicke des Layers ab, solange die unteren Layer eine deutlich kleinere Leitfähigkeit haben. Auf Grundlage dieses Ergebnisses werden Skalengesetze für Verlustraten über einem dünnen metallischen Leiter hergeleitet. Eine gute Übereinstimmung mit Experimenten wird in dem Bereich erreicht, wo der Abstand zwischen Atom und Oberfläche in der Größenordnung der Eindringtiefe des Metalls ist. Da in Experimenten metallische Layer immer geätzt werden, um verschiedene stromleitende Bahnen vonenander zu trennen, wurde der Einfluß eines endlichen Querschnittsauf das magnetische Rauschen berücksichtigt. Das lokale Spektrum des magnetischen Feldes in der Nähe einer metallischen Mikrostruktur wurde mit Hilfe von Randintegralen numerisch untersucht. Das magnetische Rauschen hängt signifikant von der Polarisierung über flachen Leiterbahnen mit endlichem Querschnitt ab, im Unterschied zu einem unendlich breiten Leiter. Es wurden auch Korrelationen zwischen mehreren Leitern berücksichtigt. Im letzten Teil werden supraleitende Atomchips betrachtet. Magnetische Fallen, die von supraleitenden Bahnen im Meissner Zustand und im gemischten Zustand sind werden analytisch durch die Methode der konformen Abbildung und numerisch untersucht. Die Eigenschaften der durch supraleitende Bahnen erzeugten Fallen werden erforscht und mit normal leitenden verglichen: Sie verhalten sich qualitativ sehr ähnlich und öffnen einen Weg zur weiteren Miniaturisierung von Fallen, wegen dem Vorteil von geringem magnetischem Rauschen. Wir diskutieren kritische Ströme und Felder für einige Geometrien.
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Bostanci, Huseyin. "HIGH HEAT FLUX SPRAY COOLING WITH AMMONIA ON ENHANCED SURFACES." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3209.
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Many critical applications today, in electronics, optics and aerospace fields, among others, demand advanced thermal management solutions for the acquisition of high heat loads they generate in order to operate reliably and efficiently. Current competing technologies for this challenging task include several single and two phase cooling options. When these cooling schemes are compared based on the high heat flux removal (100-1000 W/cm2) and isothermal operation (within several oC across the cooled device) aspects, as well as system mass, volume and power consumption, spray cooling appears to be the best choice. The current study focused on high heat flux spray cooling with ammonia on enhanced surfaces. Compared to some other commonly used coolants, ammonia possesses important advantages such as low saturation temperature, and high heat absorbing capability. Moreover, enhanced surfaces offer potential to greatly improve heat transfer performance. The main objectives of the study were to investigate the effect of surface enhancement on spray cooling performance, and contribute to the current understanding of spray cooling heat transfer mechanisms. These objectives were pursued through a two stage experimental study. While the first stage investigated enhanced surfaces for the highest heat transfer coefficient at heat fluxes of up to 500 W/cm2, the second stage investigated the optimized enhanced surfaces for critical heat flux (CHF). Surface modification techniques were utilized to obtain micro scale indentations and protrusions, and macro (mm) scale pyramidal, triangular, rectangular, and square pin fins. A third group, multi-scale structured surfaces, combined macro and micro scale structures. Experimental results indicated that micro- and macrostructured surfaces can provide heat transfer coefficients of up to 534,000 and 426,000 W/m2oC at 500 W/cm2, respectively. Multi-scale structured surfaces offered even a better performance, with heat transfer coefficients of up to 772,000 W/m2oC at 500 W/cm2, corresponding to a 161% increase over the reference smooth surface. In CHF tests, the optimized multi-scale structured surface helped increase maximum heat flux limit by 18%, to 910 W/cm2 at nominal liquid flow rate. During the additional CHF testing at higher flow rates, most heaters experienced failures before reaching CHF at heat fluxes above 950 W/cm2. However, the effect of flow rate was still characterized, suggesting that enhanced surfaces can achieve CHF values of up to 1,100 W/cm2 with 67% spray cooling efficiency. The results also helped shed some light on the current understanding of the spray cooling heat transfer mechanisms. Data clearly proved that in addition to fairly well established mechanisms of forced convection in the single phase regime, and free surface evaporation and boiling through secondary nucleation in the two phase regime, enhanced surfaces can substantially improve boiling through surface nucleation, which can also be supported by the concept of three phase contact lines, the regions where solid, liquid and vapor phases meet. Furthermore, enhanced surfaces are capable of retaining more liquid compared to a smooth surface, and efficiently spread the liquid film via capillary force within the structures. This unique advantage delays the occurrence of dry patches at high heat fluxes, and leads to higher CHF.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering PhD
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Wunderlich, Philipp Verfasser], Ulrich [Akademischer Betreuer] [Simon, and Dirk Uwe [Akademischer Betreuer] Sauer. "Surface-modified microstructured carbon electrodes for lithium-oxygen batteries / Philipp Wunderlich ; Ulrich Simon, Dirk Uwe Sauer." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1220082635/34.
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Widyaya, Vania Tanda [Verfasser], and Karen [Akademischer Betreuer] Lienkamp. "Three-dimensional, bioactive microstructured surface-attached polymer network by microcontact printing - simultaneous antimicrobial activity, protein repellency, and cell compatibility." Freiburg : Universität, 2019. http://d-nb.info/1205663304/34.
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Yata, Vishnu Vardhan Reddy. "Investigation of Spray Cooling Schemes for Dynamic Thermal Management." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc984153/.
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This study aims to investigate variable flow and intermittent flow spray cooling characteristics for efficiency improvement in active two-phase thermal management systems. Variable flow spray cooling scheme requires control of pump input voltage (or speed), while intermittent flow spray cooling scheme requires control of solenoid valve duty cycle and frequency. Several testing scenarios representing dynamic heat load conditions are implemented to characterize the overall performance of variable flow and intermittent flow spray cooling cases in comparison with the reference, steady flow spray cooling case with constant flowrate, continuous spray cooling. Tests are conducted on a small-scale, closed loop spray cooling system featuring a pressure atomized spray nozzle. HFE-7100 dielectric liquid is selected as the working fluid. Two types of test samples are prepared on 10 mm x 10 mm x 2 mm copper substrates with matching size thick film resistors attached onto the opposite side, to generate heat and simulate high heat flux electronic devices. The test samples include: (i) plain, smooth surface, and (ii) microporous surface featuring 100 μm thick copper-based coating prepared by dual stage electroplating technique. Experimental conditions involve HFE-7100 at atmospheric pressure and 30°C and ~10°C subcooling. Steady flow spray cooling tests are conducted at flow rates of 2 - 5 ml/cm².s, by controlling the heat flux in increasing steps, and recording the corresponding steady-state temperatures to obtain cooling curves in the form of surface superheat vs. heat flux. Variable flow and intermittent flow spray cooling tests are done at selected flowrate and subcooling conditions to investigate the effects of dynamic flow conditions on maintaining the target surface temperatures defined based on reference steady flow spray cooling performance.
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Aqil, Sanaa. "Wetting of microstructured surfaces." Thesis, Nottingham Trent University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431843.
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Rjiba, Narjes. "Fibre de coton : microstructures et propriétés de surface." Mulhouse, 2007. http://www.theses.fr/2007MULH0873.
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Le principal objectif de ce travail était de caractériser d'un point de vue physico-chimique la surface de la fibre de coton. Une fibre brute et une fibre extraite à l'éthanol ont été analysées. Cette caractérisation a été principalement menée par chromatographie gazeuse inverse (IGC), permettant de déterminer l'énergie de surface de ces fibres en fonction de la température ainsi que leur morphologie de surface à une échelle moléculaire, avant et après traitement. Il a été montré que l'énergie de surface de la fibre brute dépend fortement de la présence de cires et de pectines qui recouvrent un tel type de fibre. En particulier, la fusion des cires en surface des fibres est nettement mise en évidence dans une gamme de températures comprises entre 50 et 90°C. La nano-morphologie de la surface de la fibre de coton est aussi très affectée par la présence des cires : une extraction à l'éthanol conduisant à une surface plus homogène d'un point de vue topographique. Dans la de Kième partie de ce travail, pour confirmer les résultats obtenus par IGC, la fibre de coton a été caractérisée par d'autres techniques microscopiques (microscopies électronique et à force atomique) et spectroscopiques (spectroscopie de photoélectrons, spectroscopies vibrationnelles,. . . )The aim of this work was to characterize the surface of the cotton fibre from a physical and chemical point of view. Raw and ethanol extracted fibres were particularly analysed. This characterization was mainly performed by means of inverse gas chromatography (IGC), which allowed us to determine the surface energy of the fibres as a function of temperature as well as their surface morphology at a molecular scale, before and alter treatment. It was shown that the thermodynamic surface energy of the raw cotton fibre strongly depends on the presence of waxes and pectins which usually cover such a type of fibre. In particular, the melting of waxes on the fibre surface, in a range of temperatures from 50 to 90°C, is clearly pointed out. The nano-morphological aspects of the cotton fibre surface are also greatly affected by the presence of waxes: ethanol extraction leading to a more homogeneous surface from a topographical point of view. To confirm the results obtained by IGC, the characterization of cotton fibres was completed, in the second part of this work, by means of other microscopical (electronic and atomic force microscopies ) and spectroscopie (X-ray photoelectron spectroscopy, vibrational spectroscopies,. . . ) techniques
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Agarwal, Vivek. "Microstructure studies in surfactant systems /." View online ; access limited to URI, 2004. http://wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3160026.
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Tusamda, Wakhloo Nayana. "Deformability of cancer cells on 3D microstructured surfaces." Thesis, Mulhouse, 2018. http://www.theses.fr/2018MULH2259.
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Cette thèse traite de la compréhension du comportement de différents types de cellules cancéreuses sur des surfaces microstructurées. Nous avons étudié le comportement de cellules issues d’ostéosarcome (SaOS-2) et en particulier leur déformation nucléaire sur des micro-piliers confinés. Nous avons analysé le rôle du cytosquelette, des adhésions focales (AF), du nucléosquelette (LINC et lamin A) et de la chromatine, sur cette déformation. L'actomyosine et les filaments intermédiaires de vimentine jouent un rôle crucial dans l'orchestration de la déformation nucléaire. Nous avons constaté que la disposition des AF était principalement sur les parois latérales des piliers et que la connexion LINC-cytosquelette était essentielle pour le processus de déformation nucléaire contrairement à la lamine A. En utilisant des modulations chimio-topographiques des micro-piliers et un modèle de simulation numérique, nous avons démontré que ce sont les forces de traction et non pas les forces de poussée qui permettent la déformation cellulaire et nucléaire des cellules d'ostéosarcome.Nous avons également étudié la déformation nucléaire de SaOS-2 sur des micropiliers en hydrogel présentant différentes chimies et rigidités. Nous avons vu que la morphologie cellulaire, l'organisation de l'actine et le comportement des AF étaient modulés par la chimie et la mécanique du substrat. Pour explorer le rôle de l’origine du cancer, nous avons examiné le comportement de divers carcinomes du côlon sur des microtopographies différentes et constaté que les cancers d'origine épithéliale étaient moins sensibles à la microtopographie que les cellules cancéreuses d'origine mésenchymateuse. Par contre, leur comportement était affecté de manière plus visible sur des grandes cavités plus proches en termes de taille de celles des cryptes et villosités intestinalesThis thesis deals with understanding behaviour of different cancer cell types on microstructured topography. We studied the behaviour of osteosarcoma cell line (SaOS-2) on confined micropillar structures and in particular their nuclear deformation. We analysed the role of the cytoskeleton, focal adhesions (FAs), nucleoskeleton (LINC and lamin A) and chromatin in SaOS-2 deformation on micropillar topography. Actomyosin and vimentin intermediate filament were shown to play a crucial role in orchestrating nuclear deformation. We found that FAs arrangement was mostly on side walls of pillars and that the LINC-cytoskeletal connection was essential for the nuclear deformation process but not lamin A. Employing chemo-topography modulations of pillars and a computational simulation model we demonstrated that the pulling down forces and not pushing down forces drive the cellular-nuclear deformation in osteosarcoma cells. We also studied the nuclear deformation of SaOS-2 on hydrogel micropillars with different stiffness and chemistry. We saw that cell morphology, actin organization and FAs behaviour was modulated by the substrate mechanics and chemistry. To explore the role of cancer origin, we examined the behaviour of various colon carcinomas on various micro-topographies and found that the epithelial origin cancers are less responsive to microscale topography compared to mesenchymal origin cancerous cells. However, their behaviour was affected on large pits which resembled the intestinal crypt and villi arrangement in terms of size
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Bonhomme, Céline. "Turbulences et ondes en milieu naturel stratifié : deux études de cas : étude du mélange turbulent et des ondes internes du lac Pavin (Auvergne, France) ; influence des ondes de Rossby sur la concentration en chlorophylle de surface dans l'upwelling du Pérou." Phd thesis, Université Paris-Est, 2008. http://tel.archives-ouvertes.fr/tel-00558713.
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Dans les milieux aquatiques, les facteurs liés à l'hydrodynamique et au mélange aux échelles de la turbulence sont déterminants pour le transport des substances chimiques et des micro-organismes. Ce travail s'intéresse à ces phénomènes physiques et se situe à la frontière entre la limnologie physique et l'océanographie physique, au travers de l'étude de deux cas : le lac Pavin (Auvergne, France) et la région d'upwelling au large du Pérou. Un des intérêts de ce travail réside dans le changement d'échelle de l'observation de milieux naturels aquatiques allant de l'échelle millimétrique (étude de la microstructure dans le Lac Pavin) à l'échelle de la centaine de kilomètres (étude des ondes de Rossby). Le Lac Pavin est le seul lac méromictique français, ce qui signifie que le compartiment inférieur du lac ne se mélange pas annuellement. La méromicticité concerne pourtant bien d'autres bassins, plus connus et plus vastes comme la Mer Noire, la Mer Caspienne, le lac Baïkal, d'où son importance écologique. Sa méromicticité lui confère des propriétés physiques particulières, étudiées dans le cadre de cette thèse. L'étude de la variabilité du mélange diapycnal à différentes échelles de temps et d'espace dans le lac Pavin au travers de mesures de microstructure et de surveillance en continu des principaux paramètres physiques a conduit à mettre en évidence la variabilité de la stabilité de la colonne d'eau à l'échelle interannuelle. Par ailleurs, les propagations d'ondes internes de gravité sont étudiées dans ce cadre particulier à l'aide d'un modèle linéaire bidimensionnel. Elles génèrent des mouvements advectifs verticaux importants dans toute la colonne d'eau dont il faut tenir compte dans les protocoles d'échantillonnage chimiques ou biologiques. Enfin, une intrusion sous lacustre semble avoir une grande importance dans la détermination de la profondeur du mélange hivernal et le maintien de la méromicticité. La zone de l'upwelling du Pérou est parmi les plus poissonneuses au monde. Elle est caractérisée par une forte productivité primaire, observable par satellite. L'observation des ondes de Rossby a permis de mettre en évidence qu'elles génèrent plus de 50% de la variabilité observée à l'échelle intra saisonnière sur la concentration en chlorophylle de surface, à distance des côtes. Les ondes transportent la chlorophylle vers le large et participent à la détermination de l'extension de la zone de forte productivité primaire. A travers des mesures variées allant de la microstructure à l'observation satellite et grâce à l'utilisation de modèles conceptuels, la thèse met en évidence l'influence certaine des facteurs hydrodynamiques sur l'organisation des paramètres biogéochimiques de ces deux écosystèmes
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Qin, Ren-Yan. "Etude de la microtexture et de la microstructure superficielle et des propriétés physico-chimiques des surfaces des fibres de carbone." Mulhouse, 1992. http://www.theses.fr/1992MULH0235.
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L'objectif de cette étude est d'examiner, grâce à la microscopie à effet tunnel (STM), la microtexture et la microstructure superficielle des fibres de carbone de diverses origines, et de caractériser physico-chimiquement, grâce à la mise en oeuvre de plusieurs méthodes analytiques, la surface des fibres de carbone ayant subi différentes températures de traitement thermique (TTT) et différentes intensités d'oxydation anodique. En premier lieu, la STM a permis de distinguer les aspects superficiels des fibres de carbone qui sont liés à la filature du précurseur et de mettre en évidence les trois types de microtextures nodulaire, en marches et « graphène » à l' échelle atomique. L'évolution de la microstructure avec la TTT a également été étudiée et les paramètres structuraux des cristallites superficiels ont été mesurés directement sur les images. Pour la première fois, nous avons pu observer directement les micropores des fibres de carbone activées, et évaluer les effets des traitements d'oxydation à l'échelle atomique. En deuxième lieu, la chromatographie gazeuse inverse (CGI) a permis de caractériser l'hétérogénéité énergétique entraînée par l'hétérogénéité structurale. Nous avons montré que les sites des plans de base sont prédominants à la surface des fibres et que l'oxydation anodique introduit des sites ayant un caractère acide. La composante dispersive de l'énergie de surface mesurée par CGI à dilution infinie ne caractérise que les sites de haute énergie. L'évolution de cette énergie avec la TTT et l'oxydation anodique a été interprétée en termes de sites de bordure, de défauts superficiels et d'hétéroatomes de haute polarisabilité
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Hollabaugh, Kate R. "Microstructure and rheology of mixed ionic surfactants." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 108 p, 2009. http://proquest.umi.com/pqdweb?did=1654493531&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Thesis (M.Ch.E.)--University of Delaware, 2008.Principal faculty advisors: Norman J. Wagner, Dept. of Chemical Engineering; and Eric W. Kaler, College of Engineering. Includes bibliographical references.
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Festy, Frederic. "Structural and spectroscopic studies of surfaces on the nanometre scale." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368802.
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Anders, Sebastian [Verfasser]. "Interactions between biosystems and 3D microstructured surfaces / Sebastian Anders." München : Verlag Dr. Hut, 2019. http://d-nb.info/1181514142/34.
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Yeung, Chun L. "Design and fabrication of microstructured and switchable biological surfaces." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1712/.
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The research presented in this thesis explores the design and fabrication of microstructured and switchable biological surfaces, which may have potential applications of nanobiotechnology. The thesis focuses on the fabrication of biological surfaces which can be controlled via external stimuli. Chapter 1 - Introduction to Nanobiotechnology - presents an introduction to the background of this research including the role of self-assembled monolayers (SAMs) in nanobiotechnology, microstructure fabrication techniques, stimuli responsive surfaces and cell migration. Chapter 2 - Surface characterization techniques - presents surface characterization techniques employed throughout this research. Chapter 3 - Study of Arp2/3 complex activity in filopodia of spreading cells using patterned biological surfaces - presents the fabrication and characterization of patterned biological (fibronectin) surfaces using patterning technology (microcontact printing) and several surface analytical techniques. This study explores the role of filopodia in the spreading of Mouse Embryonic fibroblast (MEF) cells and the function of Arp2/3 complex in this process. The results demonstrated that filopodia, produced by MEF cells interacted with the patterned fibronectin surface and guided lamellipodia protrusion. Arp2/3 complex, which is absent on the filopodia adhesion site, does not facilitate in the adhesion of filopodia on the fibronectin surface. Chapter 4 - Tuning specific biomolecular interactions using electro-switchable oligopeptide surfaces - presents the fabrication of responsive surfaces that rely on electro-switchable peptides to control biomolecular interactions on gold surfaces. This system is based upon the conformational switching of positively charged oligolysine peptides that are tethered to a gold surface. The bioactive molecular moieties (biotin) terminates on the oligolysines can be reversibly exposed (bio-active state) or concealed (bio-inactive state) on demand, as a function of surface potential. Chapter 5 - Experimental procedures, protocols and synthesis - describes the experimental techniques used during the investigations performed throughout the work described in this thesis. Experimental protocols and data analysis by various equipment are described.
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Ruleman, Karlen E. (Karlen Elizabeth). "Heat transfer via dropwise condensation on hydrophobic microstructured surfaces." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54510.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 22).
Dropwise condensation has the potential to greatly increase heat transfer rates. Heat transfer coefficients by dropwise condensation and film condensation on microstructured silicon chips were compared. Heat transfer coefficients are found to be seventy percent higher in the hydrophobic, dropwise condensation case relative to the hydrophilic, film condensation case. With this increased heat transfer coefficient, dropwise condensation using microstructures could improve many heat exchange applications, particularly electronics cooling.
by Karlen E. Ruleman.
S.B.
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Safdar, Adnan. "Microstructures and surface roughness of EBM produced Ti-6Al-4V." Licentiate thesis, Malmö högskola, Teknik och samhälle, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-7791.
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The work presented in this dissertation is concerned with the microstructures andsurface roughness of test slabs of Ti-6Al-4V produced by one of powder based AdditiveManufacturing (AM) technique namely Electron Beam melting (EBM). The effects of processparameters of a EBM system and geometry factors of a EBM build such as slabs’ thickness andheight etc. on the microstructure and the surface roughness of the EBM produced Ti-6Al-4Vhave being investigated. The processing parameters of the EBM system involved in the presentwork include beam current, scan speed, offset focus and scanning length etc. In this study threedifferent batches of samples were prepared. Microstructures of EBM built Ti-6Al-4V werestudied using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), TransmissionElectron Microscopy (TEM), and X-ray diffraction (XRD). Confocal microscopy and imageanalysis codes ImageJ’s routine SurfCharJ were used to quantify the surface roughness of the testslabs. The microstructures of EBM built Ti-6Al-4V in general consist of columnar grains of priorβ phase. Inside the columnar grains there is a typical (α+β) microstructure of titanium alloyscontaining Widmanstätten α platelets and rod-shaped β phase. Grain boundary α layer has alsobeen observed on the grain boundaries of prior b columnar grains. By using TEM, the β phase inEBM built Ti-6Al-4V has been identified as a rod-like structure located on the grain boundariesof the fine a grains and often grows up along the build direction. The size of the β rods is about200nm and the distance between the β rods is ranged between 0.5 -2μm. Chemical compositionsfor different phases have been measured by TEM/EDX and volume fraction of the β phase in theEBM Ti-6Al-4V has been determined to be 2.7%. The phase transformation sequence in EBMbuilt Ti-6Al-4V has been discussed according to processing history and microstructuresobserved. It has been observed that, the size, number and geometry of prior β columnar graindepend on the sample thickness and other process parameters setting. The diameter of columnargrain varies between 2-70μm. The increase in size, number and regularity of columnar grains hasbeen observed with increase in sample thickness, beam energy density and scanning length.While with increase in height of the build it decreases. The length and smoothness of α plateletsincreases with increase in diameter of prior β columnar grain. The β phase rods are unaffected bysample thickness and process parameter settings. The sample thickness and beam energy densityhas a strong effect on the surface roughness of the test slabs. The value of surface roughnesscoefficient Ra for different test slabs varies between 1-20μm. It is observed that the surfaceroughness increases of the test slab increases with increase in thickness of the slab and beamenergy density. The possible reasons for these variations in microstructures and surfaceroughness have been discussed.
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Henrie, Benjamin L. "Elasticity in Microstructure Sensitive Design Through the use of Hill Bounds." Diss., CLICK HERE for online access:, 2002. http://contentdm.lib.byu.edu/ETD/image/etd60.pdf.
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Abdelaziz, Gamal E. "Microstructural analysis of surface and interface zones in concrete." Thesis, Aston University, 1997. http://publications.aston.ac.uk/13268/.
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Several of OPC paste and concrete specimens, with different mix proportions, were cast against CPF and impermeable formwork (IF) and the profiles of pore structure, microhardness and scratch hardness of the cover zone were established. The chloride ingress and the depth of carbonation of the surface zone of concrete cast against CPF and IF were investigated. The main mechanisms controlling the ECR processes and the factors affecting such treatment were critically reviewed. Subsequently, as a means of restoring passivation of steel embedded in carbonated concrete, such HCP specimens were subjected to ECR. The influence of ECR on the chemistry of the pore solution and the microstructure of the surface and the steel/cement past interface zones were also studied. The main findings of this investigation were as follows: (a) The thickness of the microstructure gradient of cover concrete is significantly decreased with increasing period of water curing but is relatively unaffected by curing temperature, w/e ratio and the use of cement replacement materials. (b) The scratch hardness technique was shown to be potentially useful for characterising the microstructure and microhardness gradients of the surface zone. (c) A relationship between the microstructure gradient and mass transport properties of the surface zone was established. (d) The use of CPF resulted in a significant reduction in porosity of both the cement paste matrix and the aggregate/cement paste transition zone, and a marked improvement in the resistance of the surface zone to carbonation and the ingress of chloride ions. (e) The ECR treatment resulted in a marked densification of the pore structure and in changes to the pore solution chemistry and the cement phases of near-surface and steel/cement paste transition zones. This effect was more pronounced with current density, period of treatment and particularly with the use of sodium phosphate as an electrolyte.
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Lesage, Thibault. "Grippage des aciers inoxydables : influence de la nature des matériaux, de la microstructure et des traitements thermochimiques de surface." Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2486/document.
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Le grippage dans le cas des aciers inoxydables est un phénomène complexe nécessitant une approche multi-échelle et multi-physique. Les 6 nuances d’aciers inoxydables sélectionnées au cours de cette thèse (316L, 316LN, Nitronic60, AISI660, Uranus45N et 17-4PH) ont été étudiées à l’état de réception et après traitements thermochimique de surface de type S3P. Ces matériaux ont subi un essai de grippage selon la norme ASTM G98 et les échantillons qui en résultent ont été caractérisés selon une approche d’abord surfacique (évolution de la morphologie de la surface, observations MEB…) puis en volume, notamment par le biais de l’approche originale de la microstructure (EBSD, DRX et MET notamment). Cette thèse a ainsi permis d’étudier les différents mécanismes intervenant lors du grippage des aciers inoxydables ainsi que d’étudier l’impact de différentes microstructures et composition chimiques sur ce phénomèneGalling is a complex phenomenon requiring a multi-scale and multi-physical approach. During this thesis, 6 stainless steel grades (316L, 316LN, Nitronic60, AIS1660, Uranus45N et 17-4PH) are studied, both untreated and after S3P thermochemical heat surface treatment. These materials are tested according to ASTM G98 galling test and resulting samples are then characterized. This characterization is at first realized on the surface (surface morphology evolution, SEM investigations...), then on the bulk material, consisting mainly into a microstructural characterization based on EBSD, XRD and TEM investigations. It results from this thesis a better comprehension of the galling mechanisms in the case of stainless steel. The various effects of material composition, microstructure and material properties in general are also discussed
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Deng, Dunyong. "Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties." Licentiate thesis, Linköpings universitet, Konstruktionsmaterial, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-144491.
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Additive manufacturing (AM), also known as 3D printing, has gained significant interest in aerospace, energy, automotive and medical industries due to its capabilities of manufacturing components that are either prohibitively costly or impossible to manufacture by conventional processes. Among the various additive manufacturing processes for metallic components, electron beam melting (EBM) and selective laser melting (SLM) are two of the most widely used powder bed based processes, and have shown great potential for manufacturing high-end critical components, such as turbine blades and customized medical implants. The futures of the EBM and SLM are doubtlessly promising, but to fully realize their potentials there are still many challenges to overcome. Inconel 718 (IN718) is a nickel-base superalloy and has impressive combination of good mechanical properties and low cost. Though IN718 is being mostly used as a turbine disk material now, the initial introduction of IN718 was to overcome the poor weldability of superalloys in 1960s, since sluggish precipitation of strengthening phases λ’/λ’’ enables good resistance to strain-age cracking during welding or post weld heat treatment. Given the similarity between AM and welding processes, IN718 has been widely applied to the metallic AM field to facilitate the understandings of process-microstructure-property relationships. The work presented in this licentiate thesis aims to better understand microstructures and mechanical properties EBM and SLM IN718, which have not been systematically investigated. Microstructures of EBM and SLM IN718 have been characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and correlated with the process conditions. Monotonic mechanical properties (e.g., Vickers microhardness and tensile properties) have also been measured and rationalized with regards to the microstructure evolutions before and after heat treatments. For EBM IN718, the results show the microstructure is not homogeneous but dependant on the location in the components, and the anisotropic mechanical properties are probably attributed to alignment of porosities rather than texture. Post heat treatment can slightly increase the mechanical strength compared to the as-manufactured condition but does not alter the anisotropy. SLM IN718 shows significantly different microstructure and mechanical properties to EBM IN718. The as-manufactured SLM IN718 has very fine dendritic microstructure and Laves phases in the interdendrites, and is “work-hardened” by the residual strains and dislocations present in the material. Mechanical properties are different between horizontally and vertically built samples, and heat treatment can minimize this difference. Results from this licentiate thesis provide the basis for the further research on the cyclic mechanical properties of EBM and SLM IN718, which would be the focus of following phase of the Ph.D. research.Information about opponent and seminar are missing.
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Durand, Corinne. "Atomisation de gouttes liquides sur une cible tournante microstructurée." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI035.
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L’objectif de ce travail est de concevoir un outil d’atomisation adapté à la production de poudres de carburede tungstène dans l’entreprise Technogenia, située à Saint-Jorioz (74). Plus généralement, nous avons étudiéune nouvelle conception d’atomiseur rotatif pour lequel les surfaces d’atomisation sont orientées selon un angled’incidence non nul. Une telle orientation permet alors d’exploiter de façon plus efficace la fréquence de rotationde l’atomiseur ainsi que les forces de centrifugation et de Coriolis. A partir de cette base de réflexion, troisgéométries de surface d’atomisation ont été étudiées : des surfaces lisses, des surfaces pourvues de structurationsde long de leur bord de fuite et des surfaces matricées de perforations.Les différents modes de déstabilisation des écoulements liquides ont été observés grâce à l’acquisition de vidéosultra-rapides des différentes étapes de l’impact d’une goutte unique sur les différentes géométries de surfacesd’atomisation étudiées. Les processus d’atomisation peuvent ainsi varier entre la rupture de jets liquides régulierscausée par des instabilités de type Rayleigh-Plateau et la rupture de nappes liquides causée par des instabilitésde type Rayleigh-Taylor et/ou l’initiation de perforations au coeur des nappes et films liquides. Les vidéos dessprays aqueux ainsi que l’observation au microscope des poudres métalliques nous permettent de caractériser lessprays produits. Sur l’ensemble de nos expériences nous observons que la finesse de l’atomisation s’améliore àmesure que la fréquence de rotation augmente ; ce qui constitue l’objectif prioritaire du procédé développé dans lathèse. Cependant, les surfaces texturées, certes compatibles avec les liquides classiques (aqueux ou organiques),ne le sont plus avec les contraintes induites par du métal à haute température de fusion, tel le carbure detungstène fondu objet de la thèse. En conséquence, seules les surfaces lisses sont aujourd’hui retenues et fontl’objet de développements dans le cadre de la production de poudres métalliques au sein de TechnogeniaThe aim of this work is to design a spray tool for the production of tungsten carbide powder for the companyTechnogenia, located in Saint-Jorioz (74). Thus, we have studied a new design of rotary atomizer based onatomization surface oriented at a non-zero incidence angle. Such an orientation can then allow to use moreeffectively the rotation frequency of the atomizer and the centrifugal and Coriolis forces. From this base reflection,three geometries of atomization surface were studied : smooth surfaces, surfaces with serrated structurationsalong their trailing edge and multi-perforated surfaces.The different destabilization modes of liquid flows were observed through high-speed videos of the different stagesof the single drop impact on each atomization surfaces. The atomization process can thus vary between liquid jetbreakup caused by Rayleigh-Plateau instabilities and liquid sheet breakup caused by Rayleigh-Taylor instabilitiesand/or initiating of holes in liquid films or sheets. Videos of aqueous sprays and microscopic observation of metalpowders allow us to characterize sprays. On all of our experiments, we observe that the atomisation gets better(producing finer spray), as the frequency of rotation increases. Although the textured surfaces are compatiblewith usual liquids (aqueous or organical), they can’t stand the constraints imposed by metal with a high meltingtemperature such as tungsten carbide, the object of this thesis. Therefore, only the smooth surfaces are nowthe subject of an industrial development to produce metallic powder with Technogenia company
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Zhu, Yangying. "Magnetic tunable microstructured surfaces for thermal management and microfluidic applications." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82355.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 46-47).
Micro and nanostructured surfaces have broad applications including heat transfer enhancement in phase-change systems and liquid manipulation in microfluidic devices. While significant efforts have focused on fabricating static micro/nanostructured arrays, uniform arrays that can be dynamically tuned have not yet been demonstrated. In this work, we present a novel fabrication process for magnetically tunable microstructured surfaces, where the tilt angle can be controlled upon application of an external magnetic field. We also demonstrated this platform for droplet manipulation in heat transfer applications. The tunable surfaces consist of ferromagnetic nickel (Ni) pillars on a soft PDMS substrate. The pillars have diameters of 23-35 [mu]m, pitches of 60-70 [mu]m, and heights of 70-80 [mi]m. We used vibrating sample magnetometry to obtain hysteresis loops of the Ni pillar arrays which match well the properties of bulk Ni. With a field strength of 0.5 tesla and a field angle of 600, a uniform 10.5± 1 tilt angle of the pillar arrays was observed. Furthermore, we developed a model to capture the tilt angle as a function of the magnetic field, and showed that by replacing nickel to cobalt, the tilt angle could be increased to 30' with the same field. Meanwhile, simulations show good agreement with the experiments. Future work will focus on using these surfaces to actively transport water droplets and spread the liquid film via pillar movement. This work promises tunable surface designs for important device platforms in microfluidics, biological and optical applications.
by Yangying Zhu.
S.M.
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Tanguy, Perrine. "Impact de la microstructure des revêtements ZnAlMg sur les mécanismes de formation et la performance des couches de conversion sans Cr." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEC007.
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Les revêtements multiphasés ZnAl(Mg) se caractérisent par une microstructure et une chimie de surface très différentes de celles des revêtements traditionnels de zinc pur. La réactivité de ces surfaces est par conséquent différente de celle avec l'acier galvanisé et la compatibilité avec les traitements de surface nécessairement impactée. Ce constat est à l’origine de cette proposition de thèse qui, tout en développant des compétences robustes sur la thématique des traitements de surface sur revêtements multiphasés, permettra d’améliorer notre connaissance des mécanismes mis en jeu lors de la déposition et corrosion des traitements de surface sur différents supports à base de ZnAlMgMultiphase ZnAlMg coatings are characterized by a particular microstructure and surface chemistry compared to traditional pure zinc coatings. Its surface reactivity is different from pure zinc ones as well as its compatibility with common conversion coatings. The aim of this PhD is to develop a strong knowledge regarding conversion coatings through the comprehension of the deposition and corrosion mechanisms of conversion coatings on various ZnAlMg surfaces
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Jay, Olivier. "Magnesium for biomedical applications as degradable implants : thermomechanical processing and surface functionalization of a Mg-Ca alloy." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI104/document.
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Depuis la dernière décennie, les implants dégradables pour fixation de fracture connaissent un intérêt grandissant. Parmi tous les matériaux, le magnésium apparait comme un candidat prometteur dû à une combinaison unique de propriétés. Le magnésium est très bien toléré par le corps, il a une tendance naturelle à la dégradation et son faible module élastique peut aider à réduire le stress-shielding durant la reconstitution de l'os. Cependant, une combinaison optimale entre les propriétés mécaniques et la vitesse de dégradation doit être obtenue. Le calcium étant biocompatible et procurant différents effets bénéfiques, l'alliage sélectionné pour ce projet est le Mg-2wt.%Ca. Afin d'optimiser cet alliage, nous proposons une stratégie volume/surface : modifier la microstructure interne par des traitements thermomécaniques et fonctionnaliser la surface à l'aide d'une technique additive.Du laminage et de l'extrusion à chaud ainsi que de l'extrusion coudée à aires égales (ECAE), ont été utilisé afin de modifier la microstructure. La déformation plastique sévère induite par l'ECAE produit la plus fine microstructure (taille de grain et particules de seconde phase). Alors que différentes caractéristiques microstructurales (dislocations, macles, taille de grain) peuvent justifier l'augmentation de la résistance mécanique, l'évolution de la résistance à la corrosion semble principalement affectée par la microstructure de la seconde phase et la taille de grain. Cette influence résulte de la combinaison d'un effet micro-galvanique et de la dispersion des particules de Mg2Ca et possiblement d'une couche d'oxide plus stable. L'ECAP apparait comme le traitement le plus efficace pour augmenter les propriétés mécaniques et le comportement à la corrosion.La fonctionnalisation de surface a été réalisée par un dépôt à motif réguliers à l'aide d'une technique de microdéposition de nanoparticules d'argent afin d'apporter un effet antibactérien à la surface. La déposition est suivie d'un procédé de frittage par laser. Une série de déposition a été conduite afin d'optimiser les conditions du dépôt de nanoparticules d'argent. La topographie de la couche déposée, la qualité du frittage ainsi que l'impact thermique du traitement laser sur la microstructure du substrat a été caractérisée par profilommétrie, SEM et TEM. Une modélisation par éléments finis a été réalisé afin de décrire l'impact thermique du traitement laser. Cette simulation pourra être utilisée à des fins d'optimisation du procédé de dépôt.Combiner une approche sur la microstructure interne et la surface du matériau a permis d'obtenir un alliage de magnésium fonctionnalisé ayant des propriétés améliorées qui peut être considéré dans de futurs tests biomédicauxSince the last decade, degradable implants for bone fixation have attracted special attention. Among different materials, magnesium appears as a promising candidate due to its unique combination of properties. Magnesium is very well tolerated by the body, it has a natural tendency for degradation and its low elastic modulus helps to reduce stress-shielding effect during bone healing. However, an optimal compromise between mechanical resistance and degradability kinetics has to be achieved. Since calcium is biocompatible and has several beneficial effects on magnesium, the alloy selected for this project is: Mg-2wt.%Ca alloy. To optimize this alloy for implant application, we propose a bulk/surface approach: i.e. tailoring the bulk microstructure by thermomechanical treatments and surface functionalization by additive manufacturing.Hot rolling and extrusion, and equal channel angular pressing (ECAP) have been used to tailor the microstructure. Severe plastic deformation induced by the ECAP process produces the finest grain and second particle phase microstructure. While different microstructural features (dislocations, twins, grain size) can account for the increase of the mechanical strength, the evolution of the corrosion resistance appears as primarily affected by grain size and second phase microstructure. This influence results from the combination of a micro galvanic effect, the dispersion of the second phase Mg2Ca and possibly a more stable oxide layer. Finally ECAP appears as the most efficient processing to improve both mechanical and corrosion behavior.Surface functionalization is achieved by designing a surface pattern using microdeposition with silver nanoparticles to add an antibacterial effect. The deposition is followed by a laser sintering process. A series of deposition were performed to optimize the deposition conditions for silver nanoparticles. The layer topography, the sintering, and the thermal impact of the laser treatment on the substrate microstructure have been characterized by profilommetry, SEM, TEM. A finite element simulation has been realized to describe the thermal effect of the laser treatment. This simulation can be further used for optimizing the patterning deposition process.Combining the bulk and surface approach have permitted to obtain a functionalized magnesium alloy with enhanced properties that can be considered for further biomedical tests
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Farajollahi, Farid [Verfasser]. "Formation of self-assembled microstructure on the polymer surface / Farid Farajollahi." Ulm : Universität Ulm. Fakultät für Naturwissenschaften, 2016. http://d-nb.info/1084767732/34.
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Mason, Stephen. "The microstructure, mechanical properties and surface transformations of a syalon ceramic." Thesis, University of Warwick, 1988. http://wrap.warwick.ac.uk/73126/.
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The potential application of nitride based ceramics in structural applications is dependent on their performance at elevated temperatures. To meet these demands the microstructure of a syalon ceramic has been refined. Improved processing techniques, by the use of high purity powders and "balanced" compositions, have been shown to improve the degree of inter granular crystallisation. The key aspects are the reduction of impurity levels, particularly calcium, and the use of high nitrogen compositions such that full crystallisation is achieved. The achievement of complete crystallisation results in the elimination of subcritical crack growth during fracture and high temperature creep processes dominated by non-cavitational grain boundary diffusional processes. The mechanism for oxidation has been identified by determination of the kinetics, surface and sub-surface reactions. A temperature limit of l300 oC has been identified by the reversion of YAG to a eutectic liquid by reaction with the Si02-rich oxidation layer. In this regime oxidation rates are determined by the YAG reversion and cation out-diffusion to the oxide layer. Oxidation effects have been shown to be responsible for the onset of sub-critical crack growth at temperatures above 1300oC, where crack extension results directly from YAG reversion effects. Enhanced high temperature performance above and beyond l300oC by surface transformation and surface coating was investigated. Surface microstructures based upon BI and Si2N20 have been shown to increase oxidation resistance upto 1375oC but are difficult to form without substantial surface degradation. Si3N4 and SiC coatings deposited by chemical vapour deposition (CVD) were found to have similar effects, increasing oxidation resistance beyond 1300oC.
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Reitmeier, Zachary J. "The Chemistry and Surface Microstructure of Si-Based Substrates and their Effect on the Evolution of the Microstructures of III-Nitride Films Grown via Metalorganic Vapor Phase Epitaxy." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-03202005-194018/.
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The present research was undertaken with the goals of understanding the evolution of defects and strain in heteroepitaxial AlN and GaN films deposited via metalorganic vapor phase epitaxy and minimizing those defects through manipulation of the substrate. As observed with atomic force microscopy (AFM), AlN initially grew in the form of flat-topped islands on as-received SiC substrates. Threading dislocations (TDs) observed in transmission electron microscopy (TEM) images initiated at the AlN/SiC interface as the result of defects at the surface of the mechanically polished substrate and/or condensation of point defects. GaN initially grew in the Stranski-Krastanov mode on AlN/SiC before transitioning to the dislocation-mediated step flow mode. The TDs in GaN resulted from the propagation of the TDs present in the AlN layer. The biaxial strain in the GaN layers varied with buffer layer material and layer thickness yet all samples investigated remained in residual compression due to incomplete relaxation of the coherent strain. The presence of strain during the initial growth of AlxGa1-xN layers directly on as-received SiC also resulted in phase-separated regions of Al-rich and Al-poor film. A high temperature hydrogen etch was then used to remove mechanical polishing scratches from the SiC substrates. Subsequently deposited AlN layers featured reduced pit density and the elimination of scratch-induced undulations. GaN layers deposited with AlN buffer layers on these substrates resulted in slightly reduced TD densities as observed by AFM, TEM, and high resolution X-ray diffraction (HRXRD). Regions of dramatically reduced dislocation densities were observed by HRXRD, TEM, and cathodoluminescence for GaN layers on stripe-patterned Si substrates. However, long growth times resulted in outdiffusion of Si from the substrate and subsequent film roughening. Finally, it was demonstrated that the presence of ammonia during heating of GaN templates to the growth temperature for homoepitaxy resulted in removal of carbon- and oxygen-based contaminants from the template surface.
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Mammen, Lena [Verfasser]. "Controlled wetting on silica-based nano- and microstructured surfaces / Lena Mammen." Mainz : Universitätsbibliothek Mainz, 2015. http://d-nb.info/1076186890/34.
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Wu, Tso-chang. "Laser Surface Modification of AZ31B Mg Alloy Bio-Implant Material." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1248459/.
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Magnesium and its alloys are considered as the potential biomaterials due to their biocompatibility and biodegradable characteristics but suffer from poor corrosion performance. Various surface modification techniques are employed to improve their corrosion resistance. In present case, laser surface melting was carried out on AZ31B Mg alloy with various laser energy densities using a continuous wave ytterbium laser. Effect of laser treatment on phase and microstructure evolution was evaluated by X ray diffraction and scanning electron microscopy. Multi-physics thermal model predicted time temperature evolution along the depth of the laser treatment zone. Additionally, electrochemical method and bio-immersion test were employed to evaluate the corrosion behavior in simulated body fluid medium. Microstructure revealed grain refinement and even distribution of Mg17Al12 phase along the grain boundary for laser treated samples leading to substantial enhancement in the corrosion resistance of the laser treated samples compared to the untreated alloy. The laser processed samples also possessed a superior wettability in SBF solution than the untreated sample. This was further reflected in enhanced bio-integration behavior of laser processed samples. By changing the parameters of laser processing such as power, scanning speed, and fill spacing, a controllable corrosion resistance and bioactivity/biocompatibility of the implant material was achieved.
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Adams, Brandy Rogers. "Ceramic materials mimicking normal bone surface microstructure and chemistry modulate osteoblast response." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50292.
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Bone consists of collagen/hydroxyapatite (HA) composites in which poorly crystalline carbonated calcium phosphate is intercalated within the fibrillar structure. Normal bone mineral is a carbonated-apatite, but there are limited data on the effect of mineral containing carbonate on cell response. Although the exact biological role of silicate in bone formation is unclear, silicate has been identified at trace levels in immature bone and is believed to play a metabolic role in new bone formation. To mimic the inorganic and organic composition of bone we have developed a variety of bone graft substitutes. In the present body of research, we characterized the surface composition of human cortical and trabecular bone. When then characterized the surface compositions of the following potential bone substitutes: carbonated hydroxyapatite (CO₃²-HA), silicated hydroxyapatite (Si-HA), and collagen sponges mineralized with calcium phosphate using the polymer-induced liquid-precursor (PILP) process. In the latter substitutes, the PILP process leads to type I collagen fibrils infiltrated with an amorphous mineral precursor upon which crystallization leads to intrafibrillar HA closely mimicking physiological bone mineral. We then determined the osteoblast-like cell response to each bone substitute to characterize the substrate’s effect on osteoblast differentiation. The observations collectively indicate that cells are sensitive to the formatting of the mineral phase of a bone substitute and that this format can be altered to modulate cell behavior.
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Munzer, Charlotte. "Etude de l'action d'un bioadjuvant aux substances extracellulaires sur la microstructure et les caractéristiques de surface de pâtes cimentaires pour des bétons plus éco-respectueux." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAD028/document.
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L’influence de l’incorporation d’un produit bio sourcé comme adjuvant dans les matériaux cimentaires tant à l’état frais qu’à l’état durci a été étudiée. La présence du bioproduit ne provoque pas de modifications sur les résistances mécaniques et sur la microstructure des pâtes de ciment (ATG/ATD et DRX). Des essais de caractérisation du réseau poreux de mortiers et pâtes cimentaires ont montré un effet du bioproduit sur la qualité de la peau des échantillons. Un protocole de réalisation et de conservation d’échantillons de pâte cimentaire a été mis au point afin de permettre différents essais sur des surfaces identiques dans le cas du projet « substances extracellulaires pour les bétons » impliquant des partenaires microbiologistes. L’étude de l’évolution de l’angle de contact dynamique d’une goutte d’eau posée sur des pâtes de ciment a montré que la présence du bioproduit favorise l’étalement au détriment de la pénétration de celle-ci au sein du matériau, en modifiant la tortuosité des capillaires de la matrice cimentaire. Une méthode d’analyse d’évolution de l’angle de contact en fonction du diamètre de la goutte a été développée et validée avec des données de la littérature. Cette technique originale a permis une détermination précise des angles d’avancée et de recul sur des substrats poreuxThe influence of the incorporation of a product organically sourced in cementitious materials (at fresh and hardened state) was studied. The presence of the bioproduct does not cause changes on mechanical strength and on cement past microstructure (TGA / DTA and XRD). Porous network characterization tests on mortar and cement paste showed an effect of bioproduct on the quality of skin samples. A protocol of realization and conservation of cement paste samples was developed in order to allow various tests on same surfaces for the microbiologists partners of the « extra cellular substances for concrete » project. The study of the evolution of the dynamic contact angle of a drop of water placed on cement pastes showed that the presence of the bioproduct favored at the expense of spreading the penetration of water within the material, modifying the tortuosity of the capillaries of the cementitious matrix. An analytical method of drop behaviour (contact angle versus diameter) was developed and validated with literature data. This original technique allowed an accurate determination of the angles of advance and retreat on porous substrates
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Marquier, François. "Interaction des ondes de surface avec des microstructures périodiques : émission thermique cohérente et transmission résonante." Phd thesis, Ecole Centrale Paris, 2004. http://tel.archives-ouvertes.fr/tel-00010113.
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Certains matériaux ont des modes électromagnétiques confinés à leur surface, qui sepropagent le long de celle-ci. Ces modes, qui sont appelés ondes de surface, peuvent être couplés à des ondes propagatives à l'aide d'un réseau.
Nous avons utilisé un code de calcul électromagnétique exact, basé sur l'analyse rigoureuse des ondes couplées (RCWA), pour optimiser des structures périodiques dont les dimensions sont de l'ordre ou inférieures au micron. Nous avons ainsi conçu des micro ou nanostructures pour deux types d'applications : l'émission thermique cohérente, et la transmission résonante.
En émission, nous avons optimisé des sources thermiques émettant un rayonnement
quasi-monochromatique dans une direction privilégiée de l'espace ou bien dans toutes les directions. Nous avons de plus conçu, dimensionné et mis en place un montage de mesure de l'émissivité de telles sources. Nous avons pu retrouver de manière quantitative les résultats que nous avons obtenus numériquement, puis déterminer expérimentalement la longueur de cohérence spatiale de la source.
Le second axe de cette thèse a été consacré à la transmission résonante. Nous avons
mis en évidence les mécanismes de transmission de structures métalliques en montrant l'existence de modes propres de ces structures qui sont des modes couplant modes de surface et modes de cavité. En remontant aux caractéristiques de ces modes, nous pouvons en particulier retrouver toutes les caractéristiques des pics de transmission, hauteur, largeur et position. Nous avons par ailleurs montré que des effets analogues apparaissent pour des réseaux de cristaux polaires. Finalement, des études de transmission résonante par des cristaux 2D ont montré que des modes d'ordre élevé peuvent être fortement transmis. Ces modes sont faiblement couplés à des ondes planes mais peuvent se coupler fortement à des particules ou molécules.
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Dixon, Richard John. "Ion scattering studies of the surface and near surface region of metals and semiconductors." Thesis, University of Warwick, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343788.
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Mazinanian, Neda. "Influence of microstructure and proteins on the metal release of micron-sized stainless steel powder particles." Thesis, KTH, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-98082.
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Knowledge on metal release processes from stainless steel powder, which can be potentially inhaled at occupational settings, is essential within the framework of human health and environmental risk assessments. An in-depth knowledge concerning powder history, physical properties of particles (e.g. size, morphology, and active surface area) combined with their chemical properties (such as the chemical composition of the particles and their metal release behavior) is needed for better understanding of the interaction mechanisms between metal powders and humans. So far, limited in vitro and in vivo studies exist that assess the correlation between stainless steel surface properties, protein adsorption effects, and metal release processes. The aim of this study is to add information to fill this knowledge gap through in vitro investigations of protein-induced metal release (iron, nickel, chromium, and manganese) and induced surface changes of five differently sized and/or produced (water-atomized (WA) and gas-atomized (GA)) stainless steel powder particles (three austenitic: AISI 316L, 310B, and 304B; one martensitic: AISI 410L; and one ferritic: AISI 430L) after exposure up to one week into a phosphate buffer saline (PBS) solution of pH 7.2-7.4 containing either lysozyme (LYS) or bovine serum albumin (BSA). The results show that the outmost surface oxide composition of the powders strongly depends on the production method and particle size. Gas-atomized 316L powder particles (with spherical shapes) indicated a high relative manganese content in their surface oxide (more significant in the case of 316L particles sized <4µm), while no manganese compounds were detectable in the surface oxide of water-atomized powders (of irregular particle shapes). Although austenitic stainless steels should present non-magnetic properties, the investigation of magnetic properties indicated that differently sized gas-atomized 316L particles and water-atomized 304B were to some extent ferromagnetic suggesting the presence of ferrite. BSA induced a significant enrichment of chromium in the surface oxide of all investigated powders (especially for ferritic WA430L and austenitic WA316L), except in the case of 316L powders (<4µm) showing no significant change. Metal release studies illustrated that both proteins enhanced the amount of released metal, with a preferential iron release from water-atomized particles and manganese release from gas-atomized powders. BSA-containing medium induced the highest extent of metal release in comparison with other tested biological media (up to 35-fold increase in the case of ferritic 430L particles produced by water atomization). Comparison between the metal release behavior of particulate and massive stainless steel indicated a significantly higher extent of metal released from abraded stainless steel sheets compared with particles, which is most probably an effect of freshly abraded surfaces of the massive metal sheets, not true for the particles with aged surface oxides, along with the presence of higher relative chromium content in the surface oxide.
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Högström, Herman. "Optical Studies of Periodic Microstructures in Polar Materials." Doctoral thesis, Uppsala University, Department of Engineering Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6896.
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The optical properties of matter are determined by the coupling of the incident electromagnetic radiation to oscillators within the material. The oscillators can be electrons, ions or molecules. Close to a resonance the dielectric function exhibits strong dispersion and may be negative. A negative dielectric function gives rise to a complex wave vector which is associated with no allowed states for photons, i.e. high extinction and bulk reflectance, as well as the possibility to support surface waves.
It is possible to manufacture a dielectric material that generates a complex wave vector. Such materials are called photonic crystals and they may exhibit a frequency range without allowed states for photons, i.e. an energy gap. A photonic crystal has a periodically varying dielectric function and the lattice constant is of the same order of magnitude as the wavelengths of the gap.
In this thesis, two optical phenomena causing a complex wave vector are combined. Polar materials, which have lattice resonance in the thermal infrared causing strong dispersion, are studied in combination with a periodic structure. The periodicity introduced is achieved using another material, but also by structuring of the polar material. One, two and three dimensional structures are considered. The polar materials used are silicon dioxide and silicon carbide. It is shown, both by calculations and experiments that the two optical phenomena can co-exist and interact, both constructively and destructively. A possible application for the combination of the two phenomena is discussed: Selective emittance in the thermal infrared. It is also shown that a polar material can be periodically structured by a focused ion beam in such way that it excites surface waves.
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Srivastava, Ashish Kumar Mirshams Reza. "Orientation, microstructure and pile-up effects on nanoindentation measurements of FCC and BCC metals." [Denton, Tex.] : University of North Texas, 2008. http://digital.library.unt.edu/permalink/meta-dc-6050.
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Egbujor, Grace. "Surface Microstructure Evolution of Metallic Specimens Using the Large Chamber Scanning Electron Microscope." TopSCHOLAR®, 2015. http://digitalcommons.wku.edu/theses/1473.
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An initial study into the use of the large chamber scanning electron microscope (LCSEM) to interrogate the surface microstructure evolution of metallic specimens has been carried out. The LC-SEM located at Western Kentucky University is the largest instrument of its type at any university in the world. As such, unique measurements can be performed due to the size of its chamber and extended view of its optic system. Strain was varied for each individual specimen, and imaged using Secondary Electrons within the gauge length as well as near the grip position. Results will show progression of surface microstructures and nickel content of metallic specimens. Additionally, results will demonstrate the capability of the LC-SEM to carry out these types of measurements. Future measurements will include the incorporation of an in-situ uniaxial load frame for dynamic studies.
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Larrouturou, Florent. "Amélioration des propriétés radiatives des récepteurs solaires surfaciques haute température par microstructuration." Thesis, Perpignan, 2015. http://www.theses.fr/2015PERP0030.
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La filière solaire thermodynamique, et plus précisément la technologie des centrales à tour, est l'une des ressources d'énergies renouvelables les plus prometteuses. Le travail de thèse s’inscrit dans le cadre général de l’augmentation des rendements de centrales solaires à tour où l’augmentation de l'efficacité et de la température du récepteur joue un rôle clé. L’originalité de la thèse réside dans l’étude du rôle des sélectivités spectrale et directionnelle sur le rendement de récepteurs surfaciques à haute température. L’objectif poursuivit a été d’améliorer simultanément la géométrie, le matériau, la rugosité et la microstructuration des récepteurs surfaciques pour créer une sélectivité permettant l’augmentation des rendements. La première étape a consisté à l’élaboration d’un modèle approché d’une centrale solaire pour quantifier l’influence du rendement du récepteur sur le rendement de la centrale. Dans un second temps, un modèle de récepteur détaillé incluant la résolution précise des transferts radiatifs (grâce à la méthode Monte Carlo) a été développé pour déterminer le gain en rendement que l’on peut obtenir grâce à la sélectivité spectrale et directionnelle. Ensuite, la modification des propriétés radiatives des surfaces par des microstructures unipériodiques et bipériodiques a été étudiée dans l'objectif d'augmenter la sélectivité spectrale du récepteur. Cette étape a nécessité la résolution des équations de Maxwell par la méthode RCWA. La microstructure retenue et qui offre le meilleur potentiel possède un relief pyramidal bipériodique. L’optimisation de la période et de la hauteur de ce relief permet d’obtenir une absorptivité solaire maximale égale à 0,98Concentrated solar power (CSP) technology is an alternative for renewable thermal energy generation and a promising source of energy. Managing the optical properties of a cavity solar receiver to create spectral and directional selectivities is a solution to improve receiver and solar power plant efficiencies in order to reduce cost. The two main steps of the development are to quantify the potential gain that may result from theoretical selectivities and then the optimization of microstructuration to increase as possible the spectral selectivity. At first, a calculation code was built in order to quantify the influence of receiver on the global solar power plant efficiency. Then a parametric study which takes into account thegeometry, the material, the roughness and the microstructure of the receiver was conducted. At last, an optimization of microstructuration with uniperiodic and biperiodic structures was studied. As a conclusion the best structure is a biperiodic pyramidal relief which offers a huge gain of absorptivity
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Carmagnola, Carlo Maria. "Mesure, analyse et modélisation des processus physiques du manteau neigeux sec Implementation and evaluation of prognostic representations of the optical diameter of snow in the SURFEX/ISBA-Crocus detailed snowpack model Snow spectral albedo at Summit, Greenland: measurements and numerical simulations based on physical and chemical properties of the snowpack." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU014.
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La neige est un matériau poreux dont la microstructure change en permanence. L'ensemble de ces transformations, qui prend le nom de ``métamorphisme", est susceptible d'affecter les propriétés thermiques, mécaniques et électromagnétiques de la neige au niveau macroscopique. En particulier, les échanges d'énergie et de matière à l'intérieur du manteau neigeux et entre la neige et l'atmosphère sont fortement influencés par l'évolution au cours du temps de la microstructure de la neige. Une représentation adéquate du métamorphisme dans les modèles de manteau neigeux s'avère donc cruciale. La microstructure d'un matériau poreux peut être raisonnablement décrite en se servant d'un nombre réduit de variables. En effet, la masse volumique, la surface spécifique (SSA) et la distribution de courbure permettent de caractériser la microstructure d'un matériau. Cependant, dans le cas de la neige cette approche n'en est qu'à ses débuts et n'a pas encore été appliquée de façon systématique. Des variables semi-empiriques, difficiles à mesurer et dépourvues de lien direct avec d'autres propriétés physiques, sont encore largement utilisées dans les modèles détaillés de manteau neigeux. Ce travail de thèse s'inscrit dans cette tentative de représenter la microstructure de la neige au cours du temps à l'aide de variables bien définies et mesurables sur le terrain. Parmi ces variables, nous nous sommes attachés notamment à la SSA, qui constitue une grandeur essentielle pour l'étude du manteau neigeux et de son évolution temporelle. Différentes lois d'évolution de la SSA ont été étudiées, à partir de relations empiriques basées sur des ajustements de données expérimentales jusqu'aux modèles physiques qui représentent le flux de la vapeur d'eau entre les grains de neige. Ces lois ont été dans un premier temps testées à l'aide d'un modèle simplifié de manteau neigeux et puis introduites directement dans le modèle SURFEX/ISBA-Crocus. Pour ce faire, la SSA dans Crocus a été transformée en variable prognostique, en remplaçant d'autres variables semi-empiriques préexistantes. Les différentes formulations de l'évolution temporelle de la SSA ont été comparées à des mesures de terrain, acquises lors de deux campagnes à Summit (Groenland) et au Col de Porte (France). Ces mesures ont été effectuées en utilisant de nouvelles techniques optiques et ont permis d'obtenir un riche jeu de données avec une grande résolution verticale. Les résultats montrent que les différentes formulations sont comparables et reproduisent bien les mesures, avec un écart quadratique moyen entre les valeurs de SSA simulées et observées inférieur à 10 m^2/kg. Enfin, nous avons contribué à faire le pont entre la microstructure de la neige et ses propriétés macroscopiques. En particulier, nous nous sommes intéressés au lien entre, d'une part, la SSA et, d'autre part, les propriétés mécaniques et optiques. Dans le premier cas, nous avons investigué la corrélation entre la SSA et la résistance à l'enfoncement mesurée avec un Snow Micro Pen (SMP). Les résultats encore préliminaires semblent indiquer que la SSA peut être dérivée de la masse volumique et de grandeurs micro-mécaniques estimées à partir du signal du SMP avec un modèle statistique. Dans le deuxième cas, nous avons simulé l'albédo de surface à Summit à partir des profils mesurés de masse volumique et de SSA et du contenu en impuretés. Les résultats de cette étude ont démontré que l'albédo spectral peut être correctement simulé à l'aide d'un modèle de transfert radiatif et l'énergie absorbée par le manteau neigeux peut être estimée avec une précision d'environ 1%Snow is a porous medium whose microstructure is constantly subjected to morphological transformations. These transformations, which take the name of ``metamorphism", are likely to affect the thermal, mechanical and electromagnetic properties of snow at the macroscopic level. Specifically, the exchange of energy and matter within the snowpack and between the snow and the atmosphere above are strongly impacted by the evolution over time of the snow microstructure. Therefore, an adequate representation of metamorphism in snowpack models is crucial. The microstructure of a porous medium can be reasonably described using a reduced number of variables. Indeed, the density, the specific surface area (SSA) and the curvature distribution are able to characterize the microstructure of such a material. However, in the case of snow this approach is still in its infancy and has not yet been systematically applied. Semi-empirical variables, difficult to measure and not directly linked to other relevant physical properties, are still widely used in so-called detailed snowpack models. This work contributes to the attempt to represent the state of the snow using well-defined and easily measurable microstructural variables. Among these variables, we focused particularly on the SSA, which is a key quantity for the study of snow and its temporal evolution. Different evolution laws of SSA were studied, starting from empirical relationships based on experimental data adjustments to physical models that represent the flow of water vapor between snow grains. These laws were initially tested using a simplified snowpack model and then introduced directly into the SURFEX/ISBA-Crocus snowpack model. To this end, the SSA in Crocus was turned into a prognostic variable, replacing other preexisting semi-empirical variables. The different formulations of the temporal evolution of the SSA were compared with field measurements, acquired during two campaigns at Summit (Greenland) and the Col de Porte (France). These measurements were carried out using new optical techniques and yielded a rich dataset with high vertical resolution. The results show that the different formulations are comparable and reproduce well the observations, with an average root-mean-square deviation value between simulated and measured SSA lower than 10 m^/kg. Finally, we contributed to bridge the gap between snow microstructure and macroscopic properties. In particular, we investigated the link between the SSA on the one hand and the mechanical and optical properties on the other hand. In the first case, we investigated the correlation between the SSA and the penetration resistance measured with a Snow Micro Pen (SMP). The preliminary results suggest that the SSA can be retrieved from the snow density and the micro-mechanical parameters estimated from the SMP signal using a statistical model. In the second case, we simulated the surface albedo at Summit from the measured profiles of density, SSA and impurities within the snowpack. The results of this study showed that the spectral albedo can be simulated successfully using a radiative transfer model and the energy absorbed by the snowpack can be estimated with a good accuracy (about 1%)
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Goujat, Alexis. "Inlays/onlays usinés par CFAO : critères d’évaluation in vitro des assemblages collés, complémentarité des études expérimentales." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1001/document.
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De nombreux paramètres interviennent dans la longévité des inlays/onlays réalisés par CFAO tels que l’usinabilité et les propriétés mécaniques des matériaux utilisés, l’adaptation de la restauration ainsi que la qualité de l’interface entre le matériau de restauration en céramique ou en composite et le matériau d’assemblage. Dans un premier temps, au travers d’une revue systématique de la littérature, nous avons sélectionné les méthodes expérimentales et les paramètres permettant d’évaluer l’adaptation de ces restaurations. Il existe des techniques en 2D qui mesurent l’espace dent-matériau à des points de référence présélectionnées et des techniques en 3D (Triple-scan, micro-CT) qui mesurent l'ensemble de l'interface. Cette revue de la littérature nous a permis de mettre en évidence que : le matériau de restauration, le type de préparation, le vieillissement, le collage ou non de la restauration et des paramètres propres à la CFAO ont une influence sur l’adaptation. Dans un deuxième temps, nous avons étudié les propriétés mécaniques de blocs en céramique et en composite et l’adaptation interne in vitro d’inlays usinés à partir de ces mêmes matériaux. L’influence de la nature du matériau de restauration et de son usinabilité sur l’adaptation a été mise en évidence. La troisième partie de notre travail a porté sur la qualité de cette interface par un test de résistance en microtraction et une analyse du type de fracture. Une relation étroite a été démontrée entre la microstructure du bloc testé et le type de traitement de surface utilisé. Ce travail a souligné l’importance d’utiliser plusieurs méthodologies et de les croiser entre elles afin de mieux corréler nos résultats. L’étude du vieillissement de ce joint dento-prothétique constitue un travail à part entière dans laquelle certaines méthodologies utilisées dans cette thèse (profils de rupture, essais mécaniques) peuvent être transposéesSeveral parameters are involved in the longevity of CAD-CAM inlays/onlays restorations such as the machinability and mechanical properties of the materials used, the adaptation of the restoration and the quality of the resin cement-ceramic or composite interface. Initially, through a systematic review of the literature, the experimental methodologies and parameters to evaluate the adaptation of these restorations were selected. The gap between the tooth and the material, at preselected reference points, is measured by 2D techniques. 3D techniques (Triple-scan, micro-CT) are able to measure the entire interface. This review of the literature allowed us to highlight that: the restorative material, the preparation design, aging, the use of a bonding-system and parameters regarding the CAD-CAM technology have an influence on the marginal adaptation. Afterwards, we assessed the mechanical properties of CAD-CAM ceramic and composite blocks and the internal adaptation in vitro of inlays milled with these same materials. The influence of the nature of the restorative material and its machinability on adaptation was put forward. The third part of our work focused on the quality of this interface using a microtensile bond strength test and a fracture type analysis. A tight association has been shown between the microstructure of the tested blocks and the type of surface treatment applied. This work underlined the importance of using several methodologies and crossing them to better correlate our results. Studying the aging of this dento-prosthetic joint constitutes a whole work in which some approaches used in this thesis (fracture profiles, mechanical tests) can be implemented and transposed
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Gunnerek, Rasmus. "Fatigue behavior of Ti-6Al-4V alloys manufactured by Selective Laser Melting : Influence of microstructure, surface roughness and surface morphology." Thesis, Karlstads universitet, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-67514.
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The intention of this thesis is to investigate the fatigue behavior of the Ti-6Al-4V alloy manufactured by the relatively new additive manufacturing process called Selective Laser Melting(SLM). SLM has been shown the interest from important industries such as the aerospace and biomedical industry for its potential of manufacturing lightweight and complex parts to net shape without the need of conventional methods like machining. Due to the short history of SLM there is little knowledge about how fatigue properties are influenced by the manufacturing process. This project aims to add to that knowledge by studying how the microstructure, surface roughness and surface morphology influences the fatigue life of SLM made Ti-6Al-4V alloys. Fatigue tests are done by conducting 3-point bending tests on SLM and conventional samples. It was found that the SLM samples only managed 9% of the fatigue life obtained for conventional samples. This was assumed to be caused by the poor surface roughness of SLM samples, acting as stress concentrations resulting in multiple crack nucleation leading to final fracture. It was also found that a surface morphology of 90°, relative to the length of the sample, had worse fatigue life compared to 60° and 30° due to the pattern of the sample being perpendicular to the applied load.
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Leïchlé, Thierry. "Bioplume : A MEMS-based picoliter droplet dispenser with electrospotting means for patterning surfaces at the micro-and nanometer scales." Toulouse 3, 2006. http://www.theses.fr/2006TOU30267.
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Les travaux présentés dans cette thèse portent sur la conception et la réalisation d'un système de dépôt de gouttes micrométriques à l'aide de matrices de leviers en silicium. L'originalité de ce système, nommé Bioplume, repose sur l'intégration de capteurs de forces et sur l'utilisation de méthodes de dépôt assistées par champ ou par auto-assemblage pour contrôler in-situ la taille, l'uniformité et la composition des motifs réalisés. Le système fonctionne en boucle fermée afin d'automatiser la fabrication de micromatrices de spots tout en garantissant la correction des erreurs d'alignement et le contrôle de la force exercée et du temps de dépôt. Après avoir validé le chargement assisté par électromouillage et le dépôt de solutions biologiques, nous utilisons les phénomènes d'auto-organisation afin de créer directement, à partir de solutions de nanoparticules, des microspots cristallins. Enfin, à l'aide d'électrodes incorporées aux leviers, des réactions électrochimiques sont induites dans les volumes de liquides déposés (de l'ordre du picolitre), permettant l'électrodéposition de cuivre et l'éléctropolymérisation de pyrroles. Les nombreuses fonctionnalités apportées à notre système pendant cette thèse permettent d'étendre ses capacités, faisant de Bioplume une solution fiable et complémentaire aux techniques de jet d'encre et de dip-pen en terme de taille de motifsThe need for patterning surfaces with organic or inorganic materials at a micro and nanometer scale is of crucial importance for designing novel hybrid devices with unconventional properties for photonics, electronics, biosensors, etc. Among various patterning methods, dispensing techniques relying on the use of microcantilevers are very promising for several reasons. The first one is that they permit a direct patterning of the surface with different kinds of materials without any need for prefabricated patterns. Secondly, alignment of the cantilevers with respect to specific regions on the surface is straightforward since the cantilevers themselves can be used as displacement sensors. Moreover, to overcome the serial nature of cantilever-based techniques, parallel approaches can be developed to meet specific requirements in terms of throughput and fabrication costs. Finally, electrically-assisted deposition can be envisaged provided that addressable electrodes are implemented onto the cantilevers. A fully automated MEMS designed for the trim control of a microspotting system (so called "Bioplume") using an integrated parallel force sensor with high precision and sensitivity will be presented. This microsystem improves the results, in terms of size and homogeneity of deposited droplets, through a direct-contact method. It allows the contact time and the force to be controlled during deposition. Using this method, homogeneous spots can be realized leading to a reproducible analysis. Proof-of-concept experiments have been carried out to demonstrate the versatility of our deposition system in terms of deposited materials and spot size ranging from the micro to nanometer scale. More specifically, we will discuss results obtained for surface patterning with oligonucleotides, proteins, molecular imprinted polymers, conductive polymers, nanoparticles, etc. Through direct deposition with and without electrically-assisted techniques
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Robertson, Stephanie. "Microstructural manipulation by laser irradiation of prepared samples : The ’Snapshot Method’." Licentiate thesis, Luleå tekniska universitet, Produkt- och produktionsutveckling, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76150.
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Various metallurgical microstructures and their formation are studied in this thesis by using a laser beam to melt a variety of materials with different chemical compositions over a range of thermal cycles. The laser beam was used conventionally in a narrow gap multi-layer weld, used for welding large depths with filler wire additions, as well as a non-traditional simulated welding approach labelled here as the Snapshot method. In laser beam welding, materials go through rapid heating and cooling cycles that are difficult to mimic by other techniques. In welding, any microstructural development depends on complex combinations of chemistry and thermal cycles but is also influenced by melt flow behavior. In turn, microstructural morphologies influence the mechanical behavior which can suffer due to inappropriate microstructural constituents. The Snapshot method, through control of thermal cycling and material composition, can achieve the same rates while guiding microstructural development to form tailored properties. The tunable laser beam properties can be exploited to develop an experimental welding simulation (Snapshot method), which enables the complex interlinked chemical and thermal events which take place during welding to be studied in a controlled manner. Exploring the microstructural relationships to their thermal history provides a greater knowledge into tailoring microstructural compositions to obtain various required mechanical properties for laser welding, additive manufacturing and also non-laser welding techniques. The feasibility of the Snapshot method is investigated in the three appended journal publications. High speed imaging and thermal recording have proved to be essential tools in this work, with analysis from optical microscopy and EDX/EDS to provide additional support. The Snapshot method is introduced as a concept in Papers I and II, demonstrating successfully guided thermal histories after obtaining molten material. Application of a second and third heating cycle, reheating the structure without melting, yielding altered microstructures. Reaching the austenitisation temperature range allowed for the simulation of complex multi-layer welding thermal histories. Geometrically non-uniform material additions are utilized in Paper III, which investigated the formation of microstructures through the chemical composition route. New chemical compositions were obtained by different degrees of dilution of the weld filler wire by the base material.
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Akhtar, Anisa Shera. "Surface science studies of conversion coatings on 2024-T3 aluminum alloy." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/1713.
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The research in this thesis aims to develop new mechanistic knowledge for coating processes at 2024-Al alloy surfaces, ultimately to aid the design of new protective coatings. Coatings formed by phosphating, chromating, and permanganating were characterized especially by scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy, and scanning electron microscopy . The objective was to learn about growth (nm level) as a function of time for different coating baths, as well as a function of lateral position across the different surface microstructural regions, specifically on the μm-sized Al-Cu-Mg and Al-Cu-Fe-Mn particles which are embedded in the alloy matrix . The research characterizes coating thickness, composition, and morphology.
The thesis emphasizes learning about the effect of different additives in zinc phosphating baths . It was found that the Ni²⁺ additive has two main roles : first, the rate of increase in local solution pH is limited by the slower kinetics of reactions involving Ni²⁺ compared to Zn²⁺, leading to thinner zinc phosphate (ZPO) coatings when Ni²⁺ is present. Second, most Ni²⁺ deposition occurs during the later stages of the coating process in the form of nickel phosphate and a Ni-Al oxide in the coating pores on the alloy surface, increasing the corrosion resistance. Aluminum fluoride precipitates first during the initial stages of the coating process, followed by aluminum phosphate, zinc oxide, and finally ZPO.
When Ni²⁺ is present in the coating solution at 2000 ppm, ZnO predominates in the coating above the A-Cu-Fe-Mn particle while ZPO dominates on the rest of the surface. The Mn²⁺ additive gives a more even coating distribution (compared with Ni²⁺) across the whole surface. The Mn²⁺ -containing ZPO coating is similar to the chromate coating in terms of evenness, while there is more coating deposition at the second-phase particles for permanganate coatings. The oxides on the Al-Cu-Fe-Mn and matrix regions are similar before coating, thereby confirming that a variety of observed differences in ZPO coating characteristics at these regions arise from the different electrochemical characteristics of the underlying metals. Upon exposure to a corrosive solution, the ZPO coating provides more protection to the second-phase particles compared to the matrix.
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Vüllers, Felix [Verfasser]. "Bioinspired Superhydrophobic Nano- and Microstructured Surfaces for Drag Reduction and Optoelectronics / Felix Vüllers." Karlsruhe : KIT Scientific Publishing, 2018. http://www.ksp.kit.edu.
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Rault, Vincent. "Analyse locale de la corrosion des renforts métalliques dans les pneumatiques exposés à des environnements représentatifs : vers un modèle prédictif." Thesis, Dijon, 2015. http://www.theses.fr/2015DIJOS022.
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Le sujet de thèse concerne l’analyse et la prédiction de la corrosion des renforts métalliques exposés dans des environnements représentatifs. Dans cette étude, le système va se complexifier en commençant à partir du renfort métallique délaitonné (acier perlitique) en passant par le renfort métallique laitonné (couche de laiton) pour finir avec le renfort métallique sulfuré (couche de sulfures). Cette approche permet de comprendre pas à pas les phénomènes de corrosion ainsi que l’interaction entre les différentes couches. Les matériaux de l’étude sont caractérisés au départ par des techniques de microscopies (MEB-EBSD, MET) et d’analyses de surface (XPS, Auger). Ces informations microstructurales et de composition chimique sont essentielles pour l’interprétation des essais de corrosion. Les essais électrochimiques sont ensuite réalisés dans 0,1M NaCl pour observer et quantifier le comportement en corrosion des trois types de renforts de l’étude. La quantification est un élément important pour établir des modèles prédictifs de corrosion. Deux types de techniques électrochimiques sont utilisés, les mesures à l’échelle globale (Voltampérométrie, Impédance électrochimique, couplage galvanique…) et les mesures à l’échelle locale (microcellule). Les essais à l’échelle locale sont directement reliés aux cartographies EBSD grâce à la microcellule. Un lien direct microstructure-corrosion est donc établi. A partir des essais électrochimiques, des analyses de solutions (SAA, ICP…) ainsi que des mesures de pH localisées sont réalisés pour quantifier les espèces passant en solution. Ces résultats sont des données d’entrée pour définir un milieu représentatif. De nouveaux essais électrochimiques sont enfin effectués dans le milieu représentatif pour étudier l’impact de ce nouveau milieu sur la corrosion des renforts métalliquesThis work deals with analysis and corrosion prediction of steel cords exposed in representative environments. In this study, the system will become more and more complex starting from “délaitonné” metal reinforcement (perlitic) via the brass metal reinforcement (brass layer) to finish with the metal reinforcement sulfide (sulfide layer). This approach allows you to understand step by step corrosion phenomena and the interaction between different layers. Materials of the study are first characterized by microscopy techniques (SEM-EBSD, TEM) and surface analysis (XPS, Auger). These microstructural informations and chemical composition are essential for interpretation of corrosion tests. Electrochemical tests are worked out in 0,1M NaCl to observe and quantify corrosion behavior of the three kind of steel cords. Quantification is a significant element to establish predictive corrosion models. Two electrochemical techniques are used, measurements at global scale (voltammetry, electrochemical impedance, galvanic coupling ...) and locally measurements (microcell). Measurements at the local scale are directly linked to EBSD maps thanks to the microcell. A direct link microstructure-corrosion is established. From electrochemical tests, solutions analysis (AAS, ICP ...) and local pH measurements are performed to quantify species passing into solution. These results are input data to define a representative environment.New electrochemical tests are then performed in this representative solution to study the impact of this medium on the steel cords corrosion
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Gardner, Timothy John. "The fabrication and characterization of surface-functionalized microstructures : monolayers as precursors to molecular wires." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12484.
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