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1
Hart, John Francis. "A new multiple scattering technique for X-ray photoelectron diffraction." Thesis, University of Leicester, 1997. http://hdl.handle.net/2381/30673.
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This thesis is concerned with the development and application of a new method of performing multiple scattering calculations of X-ray Photoelectron Diffraction (XPD) from periodic surfaces. The technique is based on the dynamical theory of Reflection High Energy Electron Diffraction (RHEED), allowing more efficient access to high photoelectron energies (1000eV and above) than is available using present calculational schemes. Convergence tests have been performed to identify the limitations of the present method. The method is applied to two overlayer systems for which XPD experimental data is available, c(2 x 2)S and c(2 x 2)O on Ni(001). For the c(2 x 2)S system, which is relatively well understood and therefore a good test system, data at four emission (take-off) angles is fitted, giving optimum agreement with the S atoms occupying hollow sites at a vertical adsorption height of between 1.30A and 1.35A. The agreement is improved slightly for the lowest two take-off angles by an outward relaxation in the top Ni-Ni layer spacing. Comparison is made with single scattering calculations for the system and the present method shown to be far superior at the lowest take-off angle. This clearly demonstrates the importance of multiple scattering at grazing emission angles. For the c(2 x 2)O system, data at two take-off angles is fitted giving optimum agreement with the O atoms in hollow sites at an adsorption height of 0.75A. By allowing a small outward relaxation in the top Ni-Ni layer spacing, an almost equally good fit to the data is found at an adsorption height of 0.80A. An offcentre bonding site which has been proposed, in which the O atoms are displaced from their hollow sites by 0.3A in the [110] direction has been considered and ruled out.
2
He, Yue, and 贺悦. "Characterization of metal stabilization effect by X-ray diffraction technique and nano-indentation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47753067.
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The technological development and application of waste-to-resource strategy is
significantly critical and crucial in both environmental and manufacturing industries, via
which we do not only provide practical treatments to toxic waste materials but also
translate them into usable products. It has been considered as a preferred method which
should be applied in future wastewater treatment strategies.
In this study, we investigated the process of incorporating cadmium oxide and nickel
oxide into ceramic-based materials with the phases of CdAl4O7, and CdFe2O4. Such
products are of less harmful effect to the natural environment and can also be of
beneficial use with their good mechanical properties identified by nano-indentation. We
proved the possibility and provided an opportunity to convert the waste from
wastewater treatment process to a new material resource.
XRD is preferred for characterizing solid mixtures to determine the relative
abundances of crystalline phases during the reaction process. As a result, we can obtain
the relative abundance information on the growth of the crystalline products, such as
CdAl4O7, and CdFe2O4 according to the change of fabrication temperatures. In that case,
the starting reaction temperature and the optimized temperature (at which the completed
reaction could be achieved) could be revealed. In Cd-Al system, the starting temperature
for CdAl4O7 formation is 900 °C, and the optimized formation temperature is around
1020 °C. On the other hand, for Cd-Fe system, such temperatures are of 700 °C and
850 °C correspondingly.
In our research, it is shown that the ceramic-process is an effective strategy to
stabilize the waste hazardous metals (cadmium and nickel) by materials such as
aluminate, ferrite, and kaolin commonly used in ceramic industry. Through this method,
the difficult-to-treat wasted metals would become reusable and applied in building and
infrastructure projects. Products containing CdAl4O7, CdFe2O4 and NiAl2O4 have
shown higher resistance to acidic leaching, comparing to CdO and NiO used as the
starting materials to simulate the waste metal forms discharged from the industrial
stream. Furthermore, similar measurements by alkaline attack on the sintered products
(NiAl2O4 containing samples) were also studied.
Besides the investigation to leaching behavior, the mechanical properties are also
measured by nano-indentation in our work. The incorporation of metal waste into the
fabrication of ceramic products is valuable due to the preferred stabilization
mechanisms of crystal structures and the large volume of ceramic products needed by
the construction industry. Furthermore, because the product safety and functionality
should not be compromised, a fundamental understanding of the surface properties of
metal containing phases should be further established, rather than relying solely on data
from regulatory tests on bulk samples. Therefore, the results of this study demonstrate
the superior mechanical properties of nickel spinel containing products, comparing to
the cristobalite silica matrix, under severe acid attack.published_or_final_version
Civil Engineering
Master
Master of Philosophy
3
Rachwal, James D. "X-ray diffraction applications in thin films and (100) silicon substrate stress analysis." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/1745.
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Silicon is used as a substrate for X-ray mirrors for correct imaging. The substrate needs to be mechanically bent to produce a certain curvature in order to condition and focus the X-ray beam. The X-rays impinge a mirror at very shallow angles, in order to reduce the amount of intensity loss in the diffraction process. The X-ray mirrors need to be bent to an extremely precise profile, and even small distortions from this profile can reduce the effectiveness of the X-ray mirrors. The X-rays that impinge on the mirror also produce large amounts of heat that can change the temperature of the substrate, resulting in its thermal expansion and distortion. By measuring the distortions in-situ caused by these temperature changes it may be possible to correct for these errors. A four-point bending fixture was designed for in-situ X-ray bending experiments in order to measure the distortions to the (100) silicon sample caused by the bending setup.
By being able to measure the distortion caused by the setup, in like manner it would be possible to measure distortion caused by thermal expansion. Several alignments were needed in order to obtain accurate results, including adding copper powder on top of the sample. The copper powder that was added is not under stress, and therefore will not shift its reflection peak when the sample is under bending stress, thus serving as a reference in order to make corrections. The strain results were then compared to values calculated from mechanical deflections from bending. Despite the efforts to control accuracy, a significant variation appeared in the values when the top surface was in compression. As an alternative an IONIC stress-gauge was used to measure the deflections of the sample rather than calculate them.
Another alternative was to calculate the deflection of the substrate by first determining the stress in the layer deposited onto the mirror's substrate by using sin²psi technique, then using Stoney's equation to determine the change in curvature of the substrate, with the stress in the layer being known. Several tests were performed to demonstrate the ability to measure these deflections.
4
Böhm, Jochen. "In situ tensile testing at the limits of X-ray diffraction a new synchrotron-based technique." Stuttgart Max-Planck-Inst. für Metallforschung, 2004. http://deposit.d-nb.de/cgi-bin/dokserv?idn=972182810.
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Nieh, Yeu-Perng. "Development of the large-angle oscillation technique in rapid X-ray diffraction data collection and time-resolved Laue diffraction studies of hydroxymethylbilane synthase enzyme." Thesis, University of Manchester, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680176.
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Voufack, Ariste Bolivard. "Modélisation multi-technique de la densité électronique." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0168/document.
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Il est désormais possible, en utilisant le modèle de densité électronique résolue en spin (CRM2), de combiner les diffractions des rayons X et des neutrons (polarisés) pour déterminer les distributions électroniques de charge et de spin de matériaux magnétiques cristallins. Cette méthode permet la mise en évidence des chemins d’interactions rendant compte de l’ordre magnétique. Le modèle résolu en spin a été appliqué aux complexes de coordination avec un métal de transition portant la majorité du moment magnétique, il a été ensuite utilisé pour étudier les radicaux purs organiques contenant des électrons non appariés délocalisés sur un groupement chimique et les matériaux inorganiques. Dans le radical Nit(SMe)Ph, la modélisation des densités de charge et de spin a permis, en accord avec les résultats antérieurs, de montrer que le spin est délocalisé sur le groupe O-N-C-N-O (fonction nitronyle nitroxyde). Elle a également permis de montrer l’implication des liaisons hydrogène dans les interactions magnétiques ferromagnétique observé en dessous de 0.6K. Cette étude a mis en évidence une répartition dissymétrique de la population de spin sur les deux groupes N—O dont seuls les calculs CASSCF permettent de reproduire l’amplitude. Cette dissymétrie proviendrait d’une combinaison d’effets moléculaires et cristallins. Dans le radical p-O2NC6F4CNSSN de la famille des dithiadiazolyles, la modélisation par affinement joint montre que la majorité du spin est porté par le groupement –CNSSN en accord avec les travaux antérieurs. Grace aux propriétés topologiques de la densité de charge, des interactions halogène, chalcogène et π ont été mis en évidence. Certaines de ces interactions favorisent des couplages magnétiques, notamment les contacts S…N2 entre molécules voisines pouvant contribuer à l’ordre ferromagnétique observé à très basse température (1.3K). Quant au matériau inorganique, YTiO3, les densités de charge en phases paramagnétique et ferromagnétique ont été déterminées ainsi que la densité de spin dans la phase ferromagnétique. Les résultats de cette étude montrent que les orbitales d les plus peuplées en électrons de l’atome de Ti sont dxz et dyz.. L’ordre orbital présent dans ce matériau est observé à 100 et à 20 K suggérant que l’ordre orbitalaire est lié à la distorsion des octaèdres. La fonction d’onde de l’électron non apparié est une combinaison linéaire de ces orbitales t2gX-ray and neutron diffraction methods can be combined to determine simultaneously electron charge and spin densities in crystals based on spin resolved electron density model developed at CRM2. This method enables to carry out the study of interaction paths leading to the observed ferromagnetic order. First applications of this model were to coordination complexes, where the unpaired electron is mainly located on the transition metal, then generalized to explore organic radicals and to inorganic materials. In radical Nit(SMe)Ph, the modeling of the experimental charge and spin densities showed localization of spin density on O-N-C-N-O group (nitronyl -nitroxyde function), in agreement with previous works. It is also evidenced the involvement of the hydrogen bonds in the magnetic interactions leading to the ferromagnetic transition at very low temperature (0.6K). This study revealed dissymmetrical spin population of the two N-O groups that only CASSCF-type calculations can reproduce in amplitude (not DFT). This dissymmetry originates from both molecular and crystal effects. In radical p-O2NC6F4CNSSN belonging to the family of dithiadiazolyl, the joint refinement showed that the majority of the spin is distributed on -CNSSN group in agreement with the previous works. From topological properties of the charge density, halogen, chalcogen and π interactions have been highlighted. The most important magnetic interactions are observed through the network formed by contacts S ... N2 between neighboring molecules leading to the ferromagnetic order below 1.23K. Concerning the inorganic material, YTiO3, the charge densities in both paramagnetic and ferromagnetic phases and spin density were modelled. The results show that the most populated d orbitals of Ti atom are dxz and dyz. The orbital ordering evidenced in this material is observed at 100 and 20 K due to the orthorhombic distorsion. The wave function of the unpaired electron is a linear combination of these particularly populated t2g orbitals
7
Dogan, Ilker. "Fabrication And Characterization Of Aluminum Oxide And Silicon/aluminum Oxide Films With Si Nanocrystals Formed By Magnetron Co-sputtering Technique." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609687/index.pdf.
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DC and RF magnetron co-sputtering techniques are one of the most suitable techniques in fabrication of thin films with different compositions. In this work, Al2O3 and Si/Al2O3 thin films were fabricated by using magnetron co-sputtering technique. For Al2O3 films, the stoichiometric, optical and crystallographic analyses were performed. For Si contained Al2O3 films, the formation conditions of Si nanocrystals were investigated. To do so, these thin films were sputtered on Si (100) substrates. Post annealing was done in order to clarify the evolution of Al2O3 matrix and Si nanocrystals at different temperatures. Crystallographic properties and size of the nanocrystals were investigated by X-ray diffraction (XRD) method. The variation of the atomic concentrations and bond formations were investigated with X-ray photoelectron spectroscopy (XPS). The luminescent behaviors of Si nanocrystals and Al2O3 matrix were investigated with photoluminescence (PL) spectroscopy. Finally, the characteristic emissions from the matrix and the nanocrystals were separately identified.
8
Sibanyoni, Johannes Mlandu. "Nanostructured light weight hydrogen storage materials." University of the Western Cape, 2012. http://hdl.handle.net/11394/4631.
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Philosophiae Doctor - PhDThe main objective of this study was to advance kinetic performances of formation and decomposition of magnesium hydride by design strategies which include high energy ball milling in hydrogen (HRBM), in combination with the introduction of catalytic/dopant additives. In this regard, the transformation of Mg → MgH2 by high energy reactive ball milling in hydrogen atmosphere (HRBM) of Mg with various additives to yield nanostructured composite hydrogen storage materials was studied using in situ pressure-temperature monitoring that allowed to get time-resolved results about hydrogenation behaviour during HRBM. The as-prepared and re-hydrogenated nanocomposites were characterized using XRD, high-resolution SEM and TEM, as well as measurements of the mean particle size. Dehydrogenation performances of the nanocomposites were studied by DSC / TGA and TDS; and the re-hydrogenation behaviour was investigated using Sieverts volumetric technique.
9
Olmo, Osuna Cristian. "Ultrasound micromolding technique and real-time X-ray diffraction using synchrotron radiation : applications to porous scaffolds for biomedical devices and study of thermal-induced transitions." Doctoral thesis, Universitat Politècnica de Catalunya, 2021. http://hdl.handle.net/10803/672329.
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Current market trend is moving to miniaturized specimens, especially in the biomedical field seeking high effective and less invasive treatrnent. Ultrasound (US) micromolding is a new technique developed to the aim of producing microsized pieces based on the use of ultrasound waves as a heating source. This heating method is highly precise and can lead to produce microsized pieces with high energy and material efficiencies by using short cycling times compared to other conventional techniques.
This PhD work explores further possibilities of ultrasound micromolding to the production of polymers with added value. The work is divided in two main blocks: the production of micropieces based on biodegradable polymers focused on biomedical applications and the application of this technique as a new method to obtain nanocomposites with a homogenous dispersion ofthe reinforcing material.
Polylactide (PLA) was selected as polymer matrix in the first block to produce drug loaded pieces and scaffolds with antibacterial activity or increased osteoconductivity by the incorporation of hydroxyapatite (HAp). Chlorhexidine (CHX) and triclosan (TCS), selected as representative bactericide agents, were successfully loaded with a homogenous distribution into the polymer matrix Drugs were slowly released from micropieces and presented clear bactericide and bacteriostatic effect against both Gram-positive and Gram-negative bacteria. Microporous scaffolds have been produced from the subsequent leaching of incorporated salts. By using NaCI cavitation problems could be avoided but pores interconnections were insufficient anda small amount of water soluble polymer (i.e. polyethylene glycol) was required in order to improve the leaching process. Final scaffolds showed enhanced cell proliferation compared to non-porous PLA PLNHAp scaffolds with a porosity degree close to 35% could be achieved with relatively good mechanical properties. lncorporation of HAp increased the thermal stability, hydrophilicity and cell proliferation with respect to neat PLA specimens.
Ultrasound waves are usuallycombined with the conventional method to produce nanocomposite (i.e. solution intercalation and melt mixing) to avoid nanoparticles aggregation and improve their distribution within the polymer matrix Hence the second block ofthis PhD work studies the use of ultrasound micromolding technology in nanocomposites production. To this end, Polycaprolactone and polyamide 12 were selected as polymer matrices whereas multi-walled carbon nanotubes
(MWCNT) and Nanofil 757 (a non-organo modified clay) were chosen as reinforcing agent. Both neat polymers and their nanocom posites were successfully micromolded with minimal polymer degradation under optimal molding condition (amplitude, force and time). US micromolding technique was revealed to be efficient in getting fully exfoliated nanocomposites even when Nanofil 757 was selected. Moreover, the influence of both, MWCNTand Nanofil 757, on crystallization behaviorand morphology were systematically studied by time resolved synchrotron experiments. Crystalline polymorphic transitions of nylon 12 were also evaluated through analyses of real time synchrotron.
A final chapter of this thesis is devoted to the study of structural transitions of nylons 12 9, 8 9, 4 9, 4 5 and copolymers derived from 1,4-diam inobutane and different ratios of glutaric and azelaic acids (nylon 4, 5+9) in order to achieve deeper knowledge on the series of even-odd polyam ides. These polyamides show different crystalline structure and structural transitions compared to the conventional polyamides, which root cause is still unclear.El uso de piezas de tamaño reducido se ha extendido en los últimos años como sinónimo de evolución tecnológica, especialmente en biomedicina, donde se están realizando grandes avances con el fin de mejorar la eficiencia de los tratamientos terapéuticos y aumentar el uso de procedimientos menos invasivos. El micromoldeo por ultrasonidos (USM) es una novedosa técnica para la obtención de micropiezas caracterizada por el uso de ultrasonidos como fuente de calor; gracias a este sistema calefacción el USM presenta tiempos de ciclo extremadamente cortos y un alto rendimiento energético. El trabajo expuesto en esta tesis doctoral se divide en dos partes, un primer bloque enfocado en explorar posibles aplicaciones biomédicas de micropiezas basadas en polímeros biodegradables y un segundo bloque en el que se estudia la posibilidad del uso de dicha técnica para la preparación de nanocompuestos. La polilactida (PLA) fue seleccionada como polímero biodegradable en el primer bloque para la producción de micropiezas cargadas con fármacos y scaffolds con actividad antibacteriana o reforzada con hidroxiapatita (HAp) para incrementar su osteoconductividad. Como agentes bactericidas se escogieron clorhexidina (CHX) y triclosan (TCS), los cuales se cargaron con éxito en la matriz de PLA presentando una distribución uniforme y una clara actividad antibacteriana. Los scaffolds porosos se prepararon por un proceso indirecto al remover la sal soluble en agua tras ser moldeada junto al polímero. Aunque era factible obtener piezas de PLA cargadas con NaCI sin problemas de cavitación o degradación del polímero la conexión entre los poros era insuficiente y una gran cantidad de sal quedaba retenida en la pieza final. Con tal de incrementar dicha interconexión y conseguir un scaffolds poroso libre de NaCI fue necesario agregar polietilenglicol (PEG). Los scaffolds finales cargados con TCS presentan una mejora en la proliferación celular, un efecto bactericida y bacteriostático y una liberación más rápida. En los sistemas PLA/HAp fue crítico el uso HAp libre de impurezas para evitar cavitaciones yamarilleamiento en las muestras. La incorporación de HAp mejoró la estabilidad térmica, la hidrofobicidad y la proliferación y colonización celular. Los procesos convencionales para la producción de nanocompuestos (preparación por disolución y mezclado en fundido) suelen usar ondas de ultrasonidos para mejorar el proceso y evitar la aglomeración de las nanopartículas, aumentando así las interacciones refuerzo-polímero. Con esta premisa en mente el segundo bloque de esta tesis abarca la producción, mediante USM de dos tipos de nanocom puestos: una matriz de policaprolactona (PCL) con nanotubos de carbono (MWCNT) y una matriz de poliamida 12 (Nylon 12) con arcilla. El USM es un proceso adecuado para la obtención de nanocompuestos exfoliados en un solo paso, incluso cuando la arcilla utilizada no ha sido modificada orgánicamente (N757). La influencia de ambos agentes externos (MWCNT y N757) en el proceso de cristalización y la morfología cristalina se han estudiado mediante e>IJ) erimentos de sincrotrón en tiempo real. Las transiciones polimórficas del nylon 12 también fueron estudiadas mediante los datos recopilados en los experimentos con radiación sincrotrón. En un último bloque se han estudiado también las estructuras y transiciones estructurales de los nylons 12 9, 8 9, 4 9, 4 5, así como varias copoliamides derivadas de la 1,4-butanodiamina y distintas proporciones de ácidos glutárico y azelaico (nylon 4,5+9) mediante datos calorimétricos, espectrocópicos y de difracción de rayos X recogidos en barridos de calentamiento y enfriamiento . Estas poliamidas tipo par-impar muestran estructuras peculiares y unas transiciones estructurales diferentes a las de otras poliamidas convencionales y cuyo origen aún no está claro.
Polímers i biopolímers
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Böhm, Jochen [Verfasser]. "In situ tensile testing at the limits of X-ray diffraction : a new synchrotron-based technique / Institut für Metallkunde der Universität Stuttgart ... Vorgelegt von Jochen Böhm." Stuttgart : Max-Planck-Inst. für Metallforschung, 2004. http://d-nb.info/972182810/34.
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Milovich, F. O., N. Y. Tabachkova, V. T. Bublik, E. E. Lomonova, M. A. Borik, A. V. Kulebyakin, and V. A. Myzina. "Study of the Structure and Mechanical Properties of PSZ (Partially Stabilized Zirconia) after Heat Treatment at 1600 ˚C." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35406.
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The phase composition and twin structure of PSZ crystals after heat treatment at 1600 ˚C have been studied in relation to the content of the stabilizing impurity (Y2O3) by X-ray diffraction and transmission electron microscopy. The measurement of both hardness and fracture toughness by microindentation has been carried out. Studies have shown that crystals of PSZ obtained by directional solidification of the melt consist of two tetragonal phases (t and t’), with varying degrees of tetragonality. The yttrium-enriched phase t’ is ‘‘untransformable’’ in contrast to the t phase, with a lower content of yttrium, which, under the influence of mechanical stress, undergoes a martensitic transition to the monoclinic form. Increasing the stabilizing impurity concentration leads to an increase in the volume fraction of the ‘‘untransformable’’ phase. Increasing the concentration of Y2O3 also affects the form and dispersion of the twin domains. In this work it is shown that the quantity of hardening (fracture toughness) is proportional to the content of the transformable t phase. This work was supported by grants from the company "OPTEC"
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35406
12
Milovich, F. O., N. Y. Tabachkova, V. T. Bublik, V. V. Osiko, E. E. Lomonova, M. A. Borik, A. V. Kulebyakin, and V. A. Myzina. "The Influence of Stabilizing Impurities and Annealing on the Structure and Mechanical Properties of Partially Stabilized Zirconia." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35071.
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The phase composition and evolution of the twin structure of PSZ crystals, depending of the concentration
stabilizing impurities have been investigated by X-ray diffraction and transmission electron microscopy.
The measurements of hardness and fracture toughness by microindentation have been carried out. In
work is shown that the high mechanical characteristics of PSZ crystals are related to features of their
phase composition and structure, namely the degree of tetragonality the phase and the presence of domains
ranging in size from tens to hundreds of nanometers.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35071
13
Bell, A. M. T. "Structural studies using synchrotron X-ray powder diffraction and other techniques." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596545.
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Chapter 1 gives an introduction to X-ray and neutron powder diffraction and the use of these techniques for crystal structure determination and refinement. The Rietveld structure refinement method is described and examples of different methods of structure determination from powder diffraction data are given. The techniques of EXAFS and Mössbauer spectroscopy, which were used to provide additional structural information, are also introduced. Chapter 2 describes the different radiation sources and experimental techniques used in this work. Chapter 3 describes a structural study of magnetite, Fe3O4, below the Verwey phase transition (120 K). The P2/c structure of Fe3O4 at 60 K has been refined with lattice parameters of a = 5.9412(3) Å, b = 5.9290(3) Å, c = 16.789(1) Å and β = 90.196(4). A variable temperature study of the Fe3O4 lattice parameters between 2-280 K shows this transition is first-order. An EXAFS study between 8-270 K shows that there is no significant change in the average Fe-O distance in Fe3O4 around the transition. Chapter 4 describes a structural study on a material related to magnetite, Fe2OBO3. Two phase transitions have been found for this material. The first of these is due to magnetic ordering and takes place at 155 K. The second is due to charge ordering and takes place at 315 K, this is a structural (P21/c ↔ Pnma) transition. Chapter 5 describes a resonant scattering experiment done on CsI. Resonant scattering parameters have been refined from synchrotron X-ray powder diffraction data collected at room temperature and at 4 K close to the Cs and I K-edges. The refined f parameters are -6.2(2) e/atom (Cs, λ = 0.3453 Å), -9.0(I) e/atom (I, λ = 0.374105 Å) and -6.2(2) e/atom (I, 4 K, λ = 0.37367 Å). Chapter 6 describes the ab initio structure determination of 4-(2'3'4'-trifluorophenyl)-1235 dithiadiazolyl (C7S2N2F3H2; P2/n, a = 11.543(4) Å, b = 20.666(8) Å, c = 7.045(2) Å and β = 100.35(4) using synchrotron X-ray powder diffraction data. A global optimisation method was used to provide a starting model for Rietveld refinement.
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Dent, A. J. "The development of anomalous (resonance) X-ray diffraction techniques for solution." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384555.
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Rosa, Nunes Danilo. "Synthesis of organogels and characterization by X-ray techniques." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS006.
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Les organogels sont un type particulier de gels formés dans des liquides organiques par un réseau de polymères supramoléculaires. Ces matériaux diffèrent principalement des autres classes de gels en raison de la nature de leur réseau. Les gélifiants de faible poids moléculaire (LMWG) ont tendance à s'auto-agréger dans une direction préférentielle. Cela conduit à la formation de structures allongées, principalement des fibres, qui, par une évolution continue du processus d'assemblage, forment un réseau fibrillaire auto-assemblé enchevêtré (SAFIN). Ce mécanisme d'auto-assemblage est dirigé par des interactions non covalentes telles que la liaison hydrogène, l'empilement π – π, les interactions donneur – accepteur, la coordination des métaux et les interactions de van der Waals. La formation d'un réseau basé uniquement sur des interactions faibles affecte considérablement l'intégrité structurelle, rendant les organogels métastables et thermoréversibles.Il existe une grande variété structurelle d'organogélifiants, ce qui en fait un type de matériau intéressant, permettant une large gamme de propriétés et d'applications. Le principal défi des organogels est de prédire quel gélifiant est capable de gélifier quel liquide. Par conséquent, la découverte de nouveaux organogélateurs se fait encore principalement fortuitement, et leurs capacités de gélification sont généralement vérifiées par des processus exhaustifs d'essais et erreurs. Ainsi, il devient nécessaire de développer une méthodologie capable de réduire le temps et les dépenses nécessaires à la recherche de nouveaux organogélateurs ou du réglage de leurs propriétés.Cette thèse contient deux approches expérimentales principales. La première porte sur la détermination de l’empilement moléculaire d'organogélateurs dans les fibres par des techniques de diffusion de rayons X. La deuxième approche consiste à optimiser une méthodologie basée sur les paramètres de solubilité de Hansen, qui peut être utilisée pour rationaliser la formation d'organogel. La combinaison de ces deux outils a permis d’étudier l’effet qu’une altération structurelle du gélifiant a sur l’organogélation. Cinq familles d'organogélateurs ont été synthétisées avec des chaînes alkyles linéaires de différentes longueurs. À partir de ces cinq familles, nous avons pu déterminer l’assemblage cristallin de trois d’entre elles. Ces familles montrent une évolution régulière de la sphère de gélification qui est cohérente avec l’empilement cristallin. Ainsi, pour cette famille, la prédiction des sphères de gélification est possible. Les deux familles restantes d'organogélateurs ont présenté une évolution irrégulière de la gélification et il n'a pas été possible de déterminer avec précision l’empilement cristallin. Ce comportement est probablement dû à de petites différences du mode de cristallisation des membres de la familleOrganogels are a particular type of gels formed in organic liquids by a supramolecular polymer network. These materials mainly differ from other classes of gels due to the nature of their network. Low molecular weight gelators (LMWG) tend to self-aggregate in a preferential direction. This leads to the formation of elongated structures, mainly fibers, that by continuous evolution of the assembly process form an entangled Self-Assembled Fibrillar Network (SAFIN). This mechanism of self-assembly is led by non-covalent interactions like hydrogen-bonding, π–π stacking, donor–acceptor interactions, metal coordination and van der Waals interactions. Forming a network only based on weak interactions highly affects the structural integrity, making organogels metastable and thermoreversible.There is a wide structural variety of organogelators that makes them such an interesting type of materials, allowing a wide range of properties and applications. The main challenge with organogels is predicting which gelator is capable of gelating which liquid. Therefore, the discovery of new organogelators is still mainly the result of serendipity and their gelation abilities are usually probed by exhaustive trial and error processes. Thus, arises a need to develop a methodology capable to decrease time and expenses when researching new organogelators or tuning their proprieties.This thesis contains two main experimental approaches. The first focuses on the determination of the molecular packing of organogelators within the fibers by scattering techniques. The second approach consists in the optimization of a methodology based on Hansen solubility parameters, that can be used to rationalize organogel formation. The combination of these two tools has allowed to study the effect that a structural alteration of the gelator has on organogelation. Five families of organogelators were synthesized with linear alkyl chains at different lengths. From these five families we could determine the crystal packing for three of them. These families show a regular evolution of the gelation sphere that is coherent with the crystal packing. Thus, for these families the prediction of the gelation spheres is possible. The remaining two families of organogelators presented and erratic evolution of gelation and it was not possible to accurately determinate the crystal packing. This behavior is probably due to small differences in the crystal habit between all members of the family
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Zhu, Da'an. "Reconstruction of X-ray diffraction and confocal images using iterative deconvolution techniques." Thesis, University of East Anglia, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410084.
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Nervo, Laura. "Characterisation of the deformation mechanisms in HCP metals by combined use of X-ray imaging and diffraction techniques." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/characterisation-of-the-deformation-mechanisms-in-hcp-metals-by-combined-use-of-xray-imaging-and-diffraction-techniques(50fe7be6-4fbf-48e3-86de-942589bb000d).html.
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We envisage a fundamental study of the physical mechanisms (dislocation slip versus deformation twinning) involved in plastic deformation of hexagonal close-packed (HCP) metals like titanium and magnesium. A novel combination of X-ray imaging and diffraction techniques, termed X-ray diffraction contrast tomography (DCT), will be used to investigate details of the deformation process in the bulk of polycrystalline specimen. DCT provides access to the position, 3D shape, (average) orientation and elastic strain tensor of grains in polycrystalline sample volumes containing up to 1000 grains and more. Ultimately, an extension of the X-ray DCT technique is associated with a section topography methodology on the same instrument. This combination enables the measurement of local orientation and elastic strain tensors inside selected bulk grains. A very preliminary study of this approach is carried out on a magnesium alloy, underlying the current limitations and possible improvements of such approach. In this thesis, the data acquisition and analysis procedures required for this type of combined characterisation approach have been developed. The work is supported by the use of neutron diffraction, for an in-situ loading experiments, and two-dimensional electron backscatter diffraction (EBSD), for the initial microstructure of the materials and cross-validation of the results obtained with the X-ray DCT technique.
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Leonardi, Alberto. "Molecular Dynamics and X-ray Powder Diffraction Simulations: Investigation of nano-polycrystalline microstructure at the atomic scale coupling local structure configurations and X-ray powder Diffraction techniques." Doctoral thesis, Università degli studi di Trento, 2012. https://hdl.handle.net/11572/368091.
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Atomistic simulations based on Molecular Dynamics (MD) were used to model the lattice distortions in metallic nano-polycrystalline microstructures, with the purpose of supporting the analysis of the X-ray powder diffraction patterns with a better, atomic level understanding of the studied system.
Complex microstructures were generated with a new modified Voronoi tessellation method which provides a direct relation between generation parameters and statistical properties of the resulting model. MD was used to equilibrate the system: the corresponding strain field was described both in the core and in surface regions of the different crystalline domains. New methods were developed to calculate the strain tensor at the atomic scale.
Line Profile Analysis (LPA) was employed to retrieve the microstructure information (size and strain effects) from the powder diffraction patterns: a general algorithm with an atomic level resolution was developed to consider the size effects of crystalline domains of any arbitrary shape. The study provided a new point of view on the role of the grain boundary regions in nano-polycrystalline aggregates, exploring the interference effects between different domains and between grain boundary and crystalline regions. Usual concepts of solid mechanics were brought in the atomistic models to describe the strain effects on the powder diffraction pattern. To this purpose the new concept of Directional - Pair Distribution Function (D-PDF) was developed. D-PDFs calculated from equilibrated atomistic simulations provide a representation of the strain field which is directly comparable with the results of traditional LPA (e.g. Williamson-Hall plot and Warren-Averbach method).
The D-PDF opens a new chapter in powder diffraction as new insights and a more sound interpretation of the results are made possible with this new approach to diffraction LPA.
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Leonardi, Alberto. "Molecular Dynamics and X-ray Powder Diffraction Simulations: Investigation of nano-polycrystalline microstructure at the atomic scale coupling local structure configurations and X-ray powder Diffraction techniques." Doctoral thesis, University of Trento, 2012. http://eprints-phd.biblio.unitn.it/843/1/PhDThesis_ALeonardi.pdf.
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Atomistic simulations based on Molecular Dynamics (MD) were used to model the lattice distortions in metallic nano-polycrystalline microstructures, with the purpose of supporting the analysis of the X-ray powder diffraction patterns with a better, atomic level understanding of the studied system.
Complex microstructures were generated with a new modified Voronoi tessellation method which provides a direct relation between generation parameters and statistical properties of the resulting model. MD was used to equilibrate the system: the corresponding strain field was described both in the core and in surface regions of the different crystalline domains. New methods were developed to calculate the strain tensor at the atomic scale.
Line Profile Analysis (LPA) was employed to retrieve the microstructure information (size and strain effects) from the powder diffraction patterns: a general algorithm with an atomic level resolution was developed to consider the size effects of crystalline domains of any arbitrary shape. The study provided a new point of view on the role of the grain boundary regions in nano-polycrystalline aggregates, exploring the interference effects between different domains and between grain boundary and crystalline regions. Usual concepts of solid mechanics were brought in the atomistic models to describe the strain effects on the powder diffraction pattern. To this purpose the new concept of Directional - Pair Distribution Function (D-PDF) was developed. D-PDFs calculated from equilibrated atomistic simulations provide a representation of the strain field which is directly comparable with the results of traditional LPA (e.g. Williamson-Hall plot and Warren-Averbach method).
The D-PDF opens a new chapter in powder diffraction as new insights and a more sound interpretation of the results are made possible with this new approach to diffraction LPA.
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Intisar, Amir. "A portable CCD array detector for in-situ analysis of powder samples using combined X-ray diffraction/X-ray fluorescence techniques." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4401.
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This work describes the design, development and testing of a portable charge-coupled device detector system to be used for the simultaneous collection of X-ray diffraction and X-ray fluorescence data from powdered samples. The detector was designed for both terrestrial and extra-terrestrial applications that require in-situ analysis of samples, where access to a laboratory instrument is restricted. The detector system incorporates 4 e2v technologies CCD30-11 devices, employing multi-phase pinned technology for low noise operation. Geometrical calculations and thermal studies concerning the design of the detector are presented, with particular emphasis on motivations for the chosen geometry. Initial characterisation and calibration of the detector was performed in a laboratory environment using a purpose built test facility. The test facility included a high brightness X-ray micro-source from Bede Scientific Instruments, coupled with an XOS polycapillary collimating optic, which was used to deliver a focused beam of low divergent X-rays to the sample. The design of the test facility is discussed and the spectra and flux produced by the X-ray micro-source are investigated. The operational performance of the detector is highlighted and the use of the instrument in different applications is described, namely the planetary sciences and pharmaceuticals sector. Finally, based on the knowledge gained from initial testing of the instrument, improvements to the detector design are outlined, which greatly enhance the combined X-ray diffraction/X-ray fluorescence performance of the instrument.
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Leonard, Simon. "Solid-state structural chemistry at high pressure using X-ray synchrotron radiation diffraction techniques." Thesis, University of Leicester, 1990. http://hdl.handle.net/2381/33783.
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Energy dispersive X-ray diffraction with synchrotron radiation has been used to probe the room temperature, high pressure phase diagrams of several inorganic compounds. A review of the publications for high pressure X-ray diffraction at synchrotron sources is given. The techniques, theory, apparatus and errors of high pressure X-ray diffraction are discussed. A spectroscopic system used to enable pressure calibration is refined and its merits discussed. The calibration of this instrument against an NaC1 standard is presented. CuGeO3 undergoes two phase transitions at 73 kbar and 110 kbar respectively. The effect of pressure on the Jahn-Teller distortion around copper is discussed. The first high pressure polymorph of hafnia (beginning at 26 kbar) is shown to be iso-structural with that of zirconia. A mechanism for the transition is offered. The effect of pressure on the series of iso-structural vanadates MVO3 (M = K, Rb, Cs, NH4) reveals phase transitions in KVO3 and RbVO3 at 27 and 40 kbar respectively. Models for the transitions are offered. Intuitive expectations of an increase in compressibilities with an increase in cation size are not realised. NH4VO3 transforms to an amorphous phase at 47 kbar. A full structural model for (COD)PtNPhS(O)2NPh is offered with an R- factor of 2.54%. A discussion of ring-puckering in this and similar systems is given. An improved structural model for powdered hafnia is offered. High resolution synchrotron techniques are used in combination with Rietveld refinement methods. A discussion of the structure is given.
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Edwards, Clare M. "Applications of high-pressure spectroscopic and powder x-ray diffraction techniques to inorganic materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0005/NQ44419.pdf.
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Phung, Tran M. "Developing analytical techniques using x-ray reflectivity and diffraction to study thin film systems /." view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1251857031&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.
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Thesis (Ph. D.)--University of Oregon, 2006.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 208-221). Also available for download via the World Wide Web; free to University of Oregon users.
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Edwards, Clare M. "Application of high-pressure spectroscopic and powder X-ray diffraction techniques to inorganic materials." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37544.
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The vibrational spectra (IR, Raman) of (eta6-C 6H5CO2CH3)Cr(CO)3, (eta 6-C6H5CO2CH3)Cr(CO) 2(CS), [Pt(NH3)4][PtCl4] (MGS), [Pt(ND 3)4] [PtCl4] (MGS-D), [Pt(NH 3)4][PtBr4] (MGS-Br), ReH7(dppe) (dppe = 1,2-bis(diphenylphosphino)ethane) and CpCo(C64H4) (Cp = cyclopentadiene) have been studied under pressures up to ∼45 kbar. The magnitude and direction of the pressure-induced shift of the Raman-active nu(CO) and nu(CS) vibrational modes of (eta6-C6H 5CO2CH3)Cr(CO)3 and (eta6 -C6H5CO2CH3)Cr(CO) 2(CS) indicate an increase in the amount of pi-backbonding to the CO and CS ligands, under pressure, the increase being greater to the CO ligand than to the CS ligand. Wavenumber vs. pressure plots revealed a phase transition in both the tricarbonyl and thiocarbonyl complexes between 10--15 kbar. For CpCo(C64H4), discontinuities in the wavenumber vs. pressure plots at 10 kbar indicate a phase transition at this pressure, most likely involving rotation of the Cp ring. Insertion of the Co atom into the cage does not occur under compression; a shift to higher wavenumbers was observed for all the Raman and IR vibrational modes of CpCo(C64H4) and the parent fulleride, C 64H4. Phenyl ring rotation is thought to occur in ReH 7(dppe) under compression. Three pressure regions, from ambient pressure to ∼16 kbar, between 16 and 29 kbar and above 29 kbar, were identified from the wavenumber vs. pressure plots. A broad, weak feature in the ER spectrum appears from 5 kbar, increasing in intensity with increasing pressure. This peak has been assigned to the nu(HH) mode of a coordinated dihydrogen ligand, Re(eta2-H2). Ring rotation may assist the pressure-induced dihydride-dihydrogen interconversion. The pressure-tuning IR study of MGS and its derivatives probed the intermolecular interactions, in particular the interactions of the NH3 groups and investigated the hypothesis that hydrogen bonding of the type N- H&cdots;Cl exists in MGS. Splitting of the IR bands at ambient pressure, and
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Browne, Peter Anthony. "Determination of residual stress in engineering components using diffraction techniques." Thesis, University of Salford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365984.
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Hofmann, Felix. "Probing the deformation of ductile polycrystals by synchrotron X-ray micro-diffraction." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:4a5db5b9-1673-40bf-a25f-2e09a572a108.
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Microscopic beams of penetrating synchrotron radiation provide a unique tool for the analysis of material structure and deformation. This thesis describes my contributions to the development of new synchrotron X-ray micro-beam diffraction experimental techniques and data interpretation, and the use of experimental results for the validation of material deformation models. To study deeply buried material volumes in thick samples, the micro-beam Laue technique was extended to higher photon energies. Through-thickness resolution was achieved either by a wire scanning approach similar to Differential Aperture X-ray Microscopy (DAXM), or by applying tomographic reconstruction principles to grain-specific Laue pattern intensity. Both techniques gave promising first results. For reliable micro-beam Laue diffraction measurements of elastic strains in individual grains of a polycrystal, understanding of the error sources is vital. A novel simulation-based error analysis framework allowed the assessment of individual contributions to the total measurement error. This provides a rational basis for the further improvement of experimental setups. For direct comparison of experimental measurements and dislocation dynamics simulations, diffraction post-processing of dislocation models in two and three dimensions was developed. Simulated diffraction patterns of two-dimensional dislocation cell/wall type structures captured correctly some of the features observed experimentally in reciprocal space maps of a large-grained, lightly deformed aluminium alloy sample. Crystal lattice rotations computed from three-dimensional dislocation dynamics simulations of a Frank-Read source showed anisotropic orientation spread similar to that observed in micro-beam Laue experiments. For the experimental study of crystal lattice distortion, a novel technique was proposed that combines micro-beam Laue diffraction with scanning white-beam topography. Diffraction topography allows the study of lattice rotation at scales smaller than the scanning beam size. The new technique makes it possible to apply classical topography methods to deformed samples.
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Strusevich, Dmitry. "Development of in-situ synchrotron X-ray powder diffraction techniques for studies of catalytic systems." Thesis, Birkbeck (University of London), 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497909.
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Ananthaviravakumar, Nada. "Investigation of residual stresses in engineering components using neutron and synchrotron x-ray diffraction techniques." Thesis, University of Salford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248906.
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Siddiqui, Samera. "Crystallographic and microstructural studies of dental enamel using synchrotron X-ray diffraction and complementary techniques." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8987.
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The complex microstructure and properties of dental enamel have been studied for decades using a variety of quantitative and qualitative techniques in order to gain a greater depth of understanding behind the chemical and physical processes that are associated with the formation and destruction of this biological apatite. Dental enamel is composed of highly ordered carbonated hydroxyapatite crystals which, together with its small organic component, are responsible for its mechanical strength, allowing it to serve its functional purpose. Environmental changes at any stage of the biomineralisation process or post eruption can disrupt the orientation and alter the structure and function, which can have detrimental clinical effects. The aim of this study is to understand and characterise the structural and crystallographic properties of disrupted enamel, and compare this to healthy unaffected tissue. Enamel affected by the genetic disorder, Amelogenesis Imperfecta, alongside enamel disrupted by dissolution and caries were studied using Synchrotron X-ray diffraction, 3D X-ray Microtomography, and Scanning Electron Microscopy techniques to relate these features to the clinically observed characteristics; to the chemistry; and to the known genetics of the tooth. Synchrotron radiation was used to map changes in preferred orientation, while the corresponding mineral density distributions were seen by using an in house developed, non-destructive microtomography system. Structural information on dental enamel at the crystallographic and micron length scales can benefit a variety of different disciplines. This project has the potential to inform early diagnosis, develop a tool for an early recognition of progressive or highly variable medical conditions, and design potential treatment regimes. The comparison of affected enamel to that of healthy enamel will provide a unique opportunity to identify the developmental pathways required for normal tooth development and give insights into the basic principles underlying mammalian biomineralisation.
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Patel, Shamim. "Single photon counting X-ray diffraction techniques for the investigation of shock compressed condensed matter." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:864f1766-eb75-456e-a66d-950faa6c24ed.
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X-ray diffraction has now become a key tool in dynamic compression experiments, with a rich variety of mature diagnostics available. It is a technique which measures the arrangement of atoms in solid material, a direct measurement of the structure and density of materials. This thesis presents two new diffraction diagnostics where the key innovation is the use of a single photon counting CCD to measure energy resolved diffraction signal. Using CCDs in this way has not been done before in a high power laser experiment. The first diagnostic measures diffraction from a poly-crystalline sample and along with experimental results, a simulation code was created to support the development of the technique. The second technique is for use with single crystal samples. The energy resolving ability of the CCD is shown to give extra information about the state of the compressed material it is probing. As an extension to the experimental work, Molecular Dynamics simulations of germanium are presented which show qualitative agreement with previous work in which a phase transition occurs. The structure of the phase changed material is covered in detail.
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Larsson, Cecilia. "Determination of residual stresses and mechanical properties using neutron, X-ray diffraction, micro- and nanoindentation techniques /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/tek856s.pdf.
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Krogh, Andersen Anne. "Studies of Inorganic Layer and Framework Structures Using Time-, Temperature- and Pressure-Resolved Powder Diffraction Techniques." Doctoral thesis, Stockholm University, Department of Physical, Inorganic and Structural Chemistry, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-23.
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This thesis is concerned with in-situ time-, temperature- and pressure-resolved synchrotron X-ray powder diffraction investigations of a variety of inorganic compounds with twodimensional layer structures and three-dimensional framework structures. In particular, phase stability, reaction kinetics, thermal expansion and compressibility at non-ambient conditions has been studied for 1) Phosphates with composition MIV(HPO4)2·nH2O (MIV = Ti, Zr); 2) Pyrophosphates and pyrovanadates with composition MIVX2O7 (MIV = Ti, Zr and X = P, V); 3) Molybdates with composition ZrMo2O8. The results are compiled in seven published papers and two manuscripts.
Reaction kinetics for the hydrothermal synthesis of α-Ti(HPO4)2·H2O and intercalation of alkane diamines in α-Zr(HPO4)2·H2O was studied using time-resolved experiments. In the high-temperature transformation of γ-Ti(PO4)(H2PO4)·2H2O to TiP2O7 three intermediate phases, γ'-Ti(PO4)(H2PO4)·(2-x)H2O, β-Ti(PO4)(H2PO4) and Ti(PO4)(H2P2O7)0.5 were found to crystallise at 323, 373 and 748 K, respectively. A new tetragonal three-dimensional phosphate phase called τ-Zr(HPO4)2 was prepared, and subsequently its structure was determined and refined using the Rietveld method. In the high-temperature transformation from τ-Zr(HPO4)2 to cubic α-ZrP2O7 two new orthorhombic intermediate phases were found. The first intermediate phase, ρ-Zr(HPO4)2, forms at 598 K, and the second phase, β-ZrP2O7, at 688 K. Their respective structures were solved using direct methods and refined using the Rietveld method. In-situ high-pressure studies of τ-Zr(HPO4)2 revealed two new phases, tetragonal ν-Zr(HPO4)2 and orthorhombic ω-Zr(HPO4)2 that crystallise at 1.1 and 8.2 GPa. The structure of ν-Zr(HPO4)2 was solved and refined using the Rietveld method.
The high-pressure properties of the pyrophosphates ZrP2O7 and TiP2O7, and the pyrovanadate ZrV2O7 were studied up to 40 GPa. Both pyrophosphates display smooth compression up to the highest pressures, while ZrV2O7 has a phase transformation at 1.38 GPa from cubic to pseudo-tetragonal β-ZrV2O7 and becomes X-ray amorphous at pressures above 4 GPa.
In-situ high-pressure studies of trigonal α-ZrMo2O8 revealed the existence of two new phases, monoclinic δ-ZrMo2O8 and triclinic ε-ZrMo2O8 that crystallises at 1.1 and 2.5 GPa, respectively. The structure of δ-ZrMo2O8 was solved by direct methods and refined using the Rietveld method.
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Gonzalez, Vallejo Isabel. "Study of the structural dynamics of phase transitions using time resolved electron and X-ray diffraction." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS496.
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L'application d'une perturbation externe à certains matériaux (tels que la température, la pression ou la lumière) provoque souvent l'émergence de nouvelles propriétés macroscopiques dont l'origine se situe au niveau atomique. Par conséquent, une étude détaillée de la dynamique atomique devient essentielle pour la compréhension de processus tels que les transformations chimiques ou les transitions de phase. Dans le cas particulier des transitions de phase structurales, la symétrie du cristal est soumise à une transformation entre deux états différents à une valeur critique. Les échelles de temps typiques de la dynamique structurale sont de l'ordre de quelques centaines de femtosecondes à plusieurs picosecondes. Le développement des impulsions laser femtosecondes a permis aux chercheurs d'accéder aux échelles de temps nécessaires pour explorer la dynamique structurale ultra-rapide. Plus précisément, la diffraction résolue en temps s'est révélée être une technique idéale pour suivre et dévoiler les voies hors équilibre suivies par le réseau après une courte impulsion laser. Cette thèse présente des études expérimentales réalisées par des techniques de diffraction d'électrons et de rayons X résolue en temps sur deux transitions de phase structurelles différentes. Dans une première partie, nous démontrons les capacités du montage expérimental de diffraction d'électrons ultra-rapide (UED) développé au Laboratoire d'Optique Appliquée. Nos résultats expérimentaux réalisés sur des échantillons monocristallins de haute qualité sont présentés ainsi qu'une étude quantitative des implications des effets de diffraction dynamique dans les expériences UED. Dans une deuxième partie, nous présentons un ensemble d'expériences de diffraction d'électrons pompe-sonde réalisée sur GdTe₃, un composé appartenant à la famille des Tritellurides de terres rares qui présente un état d'onde de densité de charge. L'arrivée d'une excitation optique déclenche la transition de phase de manière non thermique. La dynamique de relaxation est caractérisée par un ralentissement qui augmente avec la fluence incidente ainsi qu'avec la température initiale de l'échantillon. Ces résultats éclairent les interprétations controversées actuelles concernant l’ émergence de défauts topologiques photo-induits.Dans une troisième partie, nous présentons des expériences de diffraction des rayons X en temps résolu réalisées à la ligne CRISTAL du synchrotron SOLEIL. Dans ce cas, nous avons étudié le composé A15 Nb₃Sn, qui présente une transition de phase d'une symétrie cubique à une symétrie tétragonale à l'équilibre thermique. Les résultats de notre expérience pompe-sonde mettent en évidence une réponse différente du réseau par rapport à la transition d’ équilibre thermique, ce qui encourage les futures recherches sur la dynamique structural de ce matériauThe application of an external perturbation in certain materials (such as temperature, pressure or light) often gives rise to the emergence of new macroscopic properties with their origin at the atomic level. Therefore, a detailed study of the atomic dynamics becomes essential to the understanding of processes such as chemical transformations or phase transitions. In the particular case of structural phase transitions, the symmetry of the crystal undergoes a transformation between two different states at a given critical value. The typical time scales of the structural dynamics occur on the order of few hundreds of femtoseconds to several picoseconds. The development of femtosecond laser pulses has enabled scientists to access the required time scales to explore the ultrafast dynamics of the lattice structure in the relevant time scales. More precisely, time-resolved diffraction has proven to be an ideal technique to track and unveil the out-of-equilibrium pathways followed by the lattice after a short laser pulse.This thesis presents experimental studies performed by time-resolved electron and X-ray diffraction techniques on two different structural phase transitions. In a first part, we demonstrate the capabilities of the ultrafast electron diffraction (UED) experimental setup developed at Laboratoire d’Optique Apliquée. Our UED experimental results performed on high quality single crystal samples are presented along with a quantitative study of the implications of dynamical diffraction effects in UED experiments. In a second part, we present a set of pump-probe electron diffraction experiments performed on GdTe₃, a compound belonging to the rare-earth Tritellurides family which presents a charge density wave state. The arrival of an optical excitation triggers the phase transition non-thermally with the out-of-equilibrium relaxation dynamics of the charge density wave state characterized by slowing down that increases with incident fluence as well as with initial sample temperature. These results shed more light on current controversial interpretations involving the emergence of photoinduced topological defects. In a third part, we present time resolved X-ray diffraction experiments performed at CRISTAL beamline at SOLEIL synchrotron. In this case we have studied the A15 compound Nb₃Sn, which displays a displacive phase transition evolving from cubic to tetragonal symmetry at thermal equilibrium. Our pump-probe results present evidence of a different lattice response with respect to the thermal equilibrium transition, encouragingf uture investigations on the dynamics of this material
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BEOLCHI, RAFAEL da S. "Adicao de complexo vitaminico em duas bioceramicas e seu efeito na regeneracao ossea." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11529.
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Made available in DSpace on 2014-10-09T12:52:55Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:03:50Z (GMT). No. of bitstreams: 0
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Martin, Christopher M. "Studies of structural variation in synthetic organic polymers using X-ray fibre diffraction techniques at high temporal and spatial resolution." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327630.
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Oatway, Wayne Brian. "Time resolved study of the deformation of polyethylene at high strain rates using X-ray diffraction and stress-strain techniques." Thesis, Keele University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263196.
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Barnes, Paris W. "Exploring structural changes and distortions in quaternary perovskites and defect pyrochlores using powder diffraction techniques." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1064346592.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xxvi, 255 p.; also includes graphics. Includes abstract and vita. Advisor: Patrick M. Woodward, Dept. of Chemistry. Includes bibliographical references (p. 221-228).
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Watts, Joshua L. "Controlled synthesis of boron carbide using solution-based techniques." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/121556/1/__qut.edu.au_Documents_StaffHome_StaffGroupH%24_halla_Desktop_Joshua%20Watts%20Thesis.pdf.
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This thesis details enhanced techniques for the synthesis and characterisation of boron carbide powder. These controlled synthesis methods in combination with a newly developed X-ray diffraction technique allow for the production of high quality boron carbide with significant technological application, as well as a deeper understanding of the structural characteristics of the material.
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Smith, Thomas. "Studies of p-type semiconductor photoelectrodes for tandem solar cells." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14522.
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Photoelectrodes and photovoltaic devices have been prepared via multiple thin film deposition methods. Aerosol assisted chemical vapour deposition (AACVD), electrodeposition (ED), chemical bath deposition (CBD) and doctor blade technique (DB) have been used to deposit binary and ternary metal oxide films on FTO glass substrates. The prepared thin films were characterised by a combination of SEM (Scanning Electron Microscopy), powder X-ray diffraction, mechanical strength tests and photochemical measurements. Nickel oxide (NiO) thin films prepared by AACVD were determined to have good mechanical strength . with a photocurrent of 7.6 μA cm-2 at 0 V and an onset potential of about 0.10 V. This contrasted with the dark current density of 0.3 μA cm-2 at 0 V. These NiO samples have very high porosity with crystalline columns evidenced by SEM. In comparison with the AACVD methodology, NiO films prepared using a combination of ED and DB show good mechanical strength but a higher photocurrent of 24 μA cm-2 at 0 V and an onset potential of about 0.10 V with a significantly greater dark current density of 7 μA cm-2 at 0 V. The characteristic features shown in the SEM are smaller pores compared to the AACVD method. Copper (II) oxide (CuO) and copper (I) oxide (Cu2O) films were fabricated by AACVD by varying the annealing temperature between 100-325°C in air using a fixed annealing time of 30 min. It was shown by photocurrent density (J-V) measurements that CuO produced at 325 °C was most stable and provided the highest photocurrent of 173 μA cm-2 at 0 V with an onset potential of about 0.23 V. The alignment of zinc oxide (ZnO) nano-rods and nano-tubes fabricated by CBD have been shown to be strongly affected by the seed layer on the FTO substrate. SEM images showed that AACVD provided the best seed layer for aligning the growth of the nano-rods perpendicular to the surface. Nano-rods were successfully altered into nano-tubes using a potassium chloride bath etching method. NiO prepared by both AACVD and the combined ED/DB method were sensitized to absorb more of the solar spectrum using AACVD to deposit CuO over the NiO. A large increase in the photocurrent was observed for the p-type photoelectrode. These p-type photoelectrode showed a photocurrent density of approximately 100 μA cm-2 at 0 V and an onset potential of 0.3 V. This photocathode was then used as a base to produce a solid state p-type solar cell. For the construction of the solid state solar cells several n-type semiconductors were used, these were ZnO, WO3 and BiVO4. WO3 and BiVO4 were successfully produced with BiVO4 proving to be the optimum choice. This cell was then studied more in depth and optimised by controlling the thickness of each layer and annealing temperatures. The best solid state solar cell produced had a Jsc of 0.541 μA cm-2 (541 nA) and a Voc of 0.14 V, TX146 made up of NiO 20 min, CuFe2O4 50 min, CuO 10 min, BiVO4 27 min, using AACVD and then annealed for 30 min at 600°C.
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Swann, Nichola Jean. "Time-resolved studies of the crystallisation and dehydration of lactose and other hydrates using synchrotron X-ray and neutron powder diffraction techniques." Thesis, Keele University, 2015. http://eprints.keele.ac.uk/4216/.
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In-situ time-resolved synchrotron X-ray and neutron powder diffraction techniques have been applied to the study of solid state structural transitions within the organic polymorphic molecular systems of lactose, trehalose and theophylline. Diffraction techniques offer an unequalled method of polymorph identification and quantification, and have repeatedly demonstrated throughout this work that they can be utilised to follow and kinetically evaluate structural transitions in real time. The study of lactose crystallisation provides further proof of the transient ( lo::1/3) mixed crystal polymorph as the initial crystallisation product, which is then followed by the typical beta lactose and alpha lactose monohydrate phases. The formation of the (lo:: l,B) mixed crystal form has been mapped and kinetically analysed; the complex multi-step crystallisation behaviour is likely to result from the high degree of polymorphism which is displayed within the lactose system. The dehydration studies of the three systems show that dehydration kinetics can vary as a function of processing conditions and environments. Evidence of a previously undocumeuted theophylline polymorph has been observed which is accessible via the seeded dehydration of theophylline monohydrate with anhydrous theophylline form II. The best production of beta lactose from the 1-biannual dehydration of alpha lactose monohydrate to date is documented and is attained from dehydration within a hydrophobic cocoa butter environment; this transition is mediated via a crystalline phase whose identity is uncertain, yet displays a unique Bragg peak at rv 12.87° 20. Neutron diffraction techniques reveal that the water content and crystalline weight fraction of trehalose dihydrate are decoupled quantities, and the dihydrate lattice can sustain substantial water loss. These observations provide supporting evidence of a transiently stable, partially hydrated state of trehalose. In addition, the applicability of the Dl9 single-crystal diffraction beamline at the Institut Laue-Langevin in the study of hydrated powder samples is reported, demonstrating the versatility of the instrument with the capability of performing dynamic studies with a time-resolution of 15 s.
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Anjum, Taseer [Verfasser], and Christian [Gutachter] Gutt. "Nanomechanics: Mechanical response analysis of semiconductor GaAs nanowires by using finite element method and x-ray diffraction techniques / Taseer Anjum ; Gutachter: Christian Gutt." Siegen : Universitätsbibliothek der Universität Siegen, 2021. http://d-nb.info/1233483994/34.
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Pettersson, Natalie. "Investigation of material removal techniques for residual stress profile determination on induction hardened steel." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-62618.
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The residual stress profile is a major factor on the fatigue life of components that are subjected to cyclic loading. In order to measure these stresses x-ray diffraction (XRD) is commonly used. The penetration depth of x-rays is limited for this method and thus, it must be combined with material removal to determine in-depth stress profiles.At SKF Manufacturing Development Center (SKF MDC), where the work for this thesis was carried out, the current layer removal method is restricted to a depth of 0.5 mm. Consequently, an additional method of material removal is necessary to obtain information at greater depths. The purpose of this thesis was to investigate possible material removal techniques that can be implemented with XRD measurements. Two different material removal techniques were studied; electrochemical etching and milling in combination with electrochemical etching. The electrochemical etching equipment was developed at SKF MDC prior to this thesis but needed further testing and validation. The residual stress profiles of induction hardened cylinders were studied using the two different removal techniques combined with XRD measurements and the results were compared with stresses measured by Electronic Speckle Pattern Interferometry (ESPI) with hole drilling. In addition, the results were compared with simulations performed at SKF MDC India. It was concluded that both the material removal methods could be successfully combined with XRD measurements. However, for practical reasons the methods should be refined before being implemented on a regular basis. Unfortunately, poor correlation between XRD and ESPI measurements were obtained due to reasons not fully understood.
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Baji, Avinash. "Development of High Toughness Bioactive Composites Using Electrospinning Techniques." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1222895930.
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Djaziri, Soundès. "Élasticité et endommagement sous chargement bi-axial de nano-composites W/Cuen couches minces sur polyimide : apport des techniques synchrotrons." Thesis, Poitiers, 2012. http://www.theses.fr/2012POIT2267/document.
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Ce travail de thèse porte sur la déformation bi-axiale contrôlée de nano-composites W/Cu en couches minces déposées sur des substrats polyimides. La nano-structuration est obtenue par stratification de deux matériaux immiscibles (W et Cu) par pulvérisation ionique avec contrôle de la taille des grains au sein du film mince par contrôle de l'épaisseur selon la direction decroissance du film. Nous avons développé une procédure permettant de caractériser le comportement mécanique des échantillons à deux échelles différentes. L'essai de traction biaxial est couplé à la diffraction des rayons X (déformation microscopique) et à la corrélation d'images numériques (déformation macroscopique). Nous avons utilisé une machine de tractionbi-axiale développée dans le cadre d’un projet ANR sur la ligne de lumière DiffAbs du synchrotron SOLEIL. Elle permet de contrôler les contraintes dans des films minces supportés par des substrats polyimides. La confrontation des résultats obtenus par ces deux techniques dans le domaine d'élasticité a montré que la déformation est intégralement transmise via l’interfacefilm - substrat. La seconde étape de notre travail a consisté à étudier les déformations du nanocomposite W/Cu au-delà du domaine d’élasticité. Nous avons mis en évidence trois domaines de déformation associés à différents mécanismes de déformation. La limite d'élasticité du nanocomposite W/Cu a été déterminée en comparant la déformation élastique du film mince à la déformation macroscopique du substrat. Enfin, l'étude de la limite d'élasticité du nanocomposite W/Cu pour différents ratios de force a révélé un comportement fragile du nanocomposite W/CuThis thesis focuses on the biaxial deformation of W/Cu nanocomposite thin films deposited on polyimide substrates. The grain size in the thin film is controlled by stratification of two immiscible materials (W and Cu) employing sputtering techniques. We developed a procedure to characterize the mechanical behavior of samples at two different scales. A biaxial tensile test is coupled to X-ray diffraction (microscopic deformation) and digital image correlation (macroscopic deformation) techniques. We used a biaxial tensile setup developed in the framework of an ANR project on the DiffAbs beamline at synchrotron SOLEIL allowing forthe control of stresses in thin films supported by polyimide substrates. By comparing the strains obtained by these two techniques, the applied strain is determined to be transmitted unchanged in the elastic domain through the film - substrate interface. The second part of our work was to study the deformation of W/Cu nanocomposite beyond the elastic range. We have highlighted three domains of deformation associated with different deformation mechanisms. The elastic limit of the W/Cu nanocomposite was determined by comparing the elastic deformation of the thin film to the macroscopic deformation of the substrate. Finally, the elastic limit of W/Cu nanocomposite was studied for different load ratios. The overall results emphasized the brittle behavior of these nanocomposites
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Näsman, Markus. "Evaluation of alternative methods forquality control of Tungsten Carbide : An evaluation of four different particle measuring techniques." Thesis, Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-74670.
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The purpose of this study was to evaluate four different measuring methods as potentialquality control tests for Tungsten Carbide (WC) raw material used in the hard metalmanufacturing at Seco Tools Fagersta. This was warranted as the current quality testcalled the HcK test, is very time consuming and the results provided that are used formilling time calculations cannot be relied on. The four measuring methods chosen wasLaser diffraction, X-Ray diffraction, Brunauer Emmett Teller analysis and Fisher Sub-Sieve Sizer measurement. These measuring techniques were chosen by Seco ToolsThe project followed the general structure of the project cycle modified to fit the projectand involving the steps project planning, present state analysis, goals and requirementdetermination, evaluation elimination of options and final of choice of option. Thealternative methods were evaluated using an evaluation matrix containing therequirements determined to be the most relevant for the quality control process. Therequirements were measurement precision, operator influence, ease of use, time requiredand operator time required. The ability of the measurement method to distinguishbetween all of the different WC powders used a Seco Tools was put as a must requirementas the new method is meant to serve as a verification test as well as a quality test.The analysis methods were evaluated practically through experiments and therefore atesting strategy was established. Initial test on two powder types was performed so thatan early evaluation could be done. During this stage both the Laser diffraction and the XRaydiffraction were eliminated due to poor results. The BET analysis and the Fisher Sub-Sieve Sizer performed better and was therefore tested further. Randomized testing wasthe method chosen when testing with all powders to minimize the environmental impacton the testing as this could affect the results of the study.The testing showed that only the Fisher SSS was able to distinguish between all thedifferent powders making it the only viable option as a new quality test. This was onlypossible when measuring on agglomerated material and the values extracted couldtherefore not be used further in the production. The Fisher SSS also performed the bestwhen ranked against the rest of the requirements, showing a high precision whenmeasuring on deagglomerated material and a combination of the two tests was thereforeconsidered.When compared to the HcK test the Fisher SSS showed a significant reduction in lead timebut also a reduction in information gathered and eventual defects controlled. The FisherSSS provides only an average particle size measurement and since no correlation has yetbeen established between the measured particle size and the required milling times it wasrecommended that the HcK test remains.It was recommended that a study is started aimed at establishing a correlation betweenthe measured particle size and the required milling time is started to investigate if this ispossible.
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Tréhorel, Roxane. "Comportement mécanique haute température du superalliage monocristallin AM1 : étude in situ par une nouvelle technique de diffraction en rayonnement synchrotron." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0055/document.
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Les superalliages monocristallins base nickel sont largement utilisés dans les parties chaudes (aux alentours de 1000°C) des turbines aéronautiques au vu de leur bonne résistance thermomécanique. Pendant le stade II du fluage leur microstructure est formée d’une matrice/couloirs γ (CFC) et de précipités en radeaux γ’ (L12). Le but de cette étude est de mieux comprendre la plasticité de ces matériaux, en particulier celle de l’alliage de 1ère génération AM1. Afin de suivre son comportement mécanique durant des transitions rapides, une nouvelle technique expérimentale par diffraction en transmission des rayons X (synchrotron) a été développée. L’utilisation d’une caméra en champ lointain permet d’enregistrer (une acquisition prend 7 secondes) la tache de diffraction (200) de chacune des deux phases, et donc l’évolution en temps réel du désaccord paramétrique entre les deux phases. En utilisant un modèle mécanique simplifié, il est possible d’en déduire les contraintes internes et la déformation plastique de chaque phase. Une campagne d’essai sur la ligne ID11 de l’ESRF a été réalisée avec cette technique. Deux types d’échantillons présentant une microstructure initiale différente, obtenues par des traitements thermiques adaptés, ont été testés. Ils ont été soumis in situ à des essais de fluage à température constante avec des sauts de contrainte. Après essai, les échantillons ont été caractérisés par MET et MEB afin de déterminer leur microstructure, vérifier les désorientations des échantillons, cartographier la concentration de certains éléments et évaluer la densité de dislocations au sein des radeaux γ’. Dans les couloirs γ, la propagation des dislocations nécessite une contrainte de Von Mises supérieure à la contrainte d’Orowan, et la densité de dislocations mobiles augmente avec la déformation plastique. Le mécanisme limitant la déformation plastique par montée de la phase γ’ est vraisemblablement l’entrée des dislocations dans les radeaux. Les conséquences déduites de cette hypothèse sont détaillées ainsi que le comportement mécanique du matériau résultantNickel-based single crystal superalloys are extensively used for turbines blades (above 1000°C) of aeronautical engines because of their good thermomechanical properties. During stage II of creep, their microstructure consists of a γ matrix (fcc) and raft precipitates γ’ (L12). The aim of this work is to improve the understanding of plasticity of this type of alloy, especially the first generation AM1 superalloy. To follow his mechanical behaviour during fast transients, a new experimental setup using synchrotron radiation diffraction in transmission geometry was developed. A far field camera allows the recording of the (200) diffraction spot of each phase, i.e. the evolution of the lattice misfit in real time (one acquisition takes 7 seconds). By using a simple mechanical model, it is possible to determine the internal stresses and the plastic strains for both phases. An experimental campaign was performed at ID11 beamline of ESRF using this new technique. Two sample types with different initial microstructure (obtained with adapted heat treatments) were tested in situ. They underwent load jumps under high-temperature creep conditions. Further post mortem investigations by SEM and TEM were performed to determine their microstructure, to check on misorientations, map some elements composition and estimate the dislocation density within the γ’ rafts. In the γ channels, dislocation propagation occurred when the Von Mises stress was larger than the Orowan stress. The mobile dislocations density increases with γ plastic strain. The limiting mechanism for γ’ plastic strain is presumably the entry of dislocation within the γ’ rafts. Under this assumption we deduce the mechanisms of interactions between dislocations, vacancies, and pores within the material, and the mechanical behaviour of the γ’ rafts
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Nan, Bo. "Výzkum nových elektrokeramických struktur pro nové aplikace senzorů." Doctoral thesis, Vysoké učení technické v Brně. CEITEC VUT, 2019. http://www.nusl.cz/ntk/nusl-408056.
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Piezoelektrické keramické materiály jsou široce používány v mnoha aplikacích a průmyslových odvětvích, nicméně tradiční materiály obvykle obsahují olovo, které je toxické vůči životnímu prostředí. Většina zemí proto zavedla zákony a omezení, které postupně minimalizují spotřebu olova a podporují výzkum v oblasti bezolovnatých kompozic, které by nahradily olověné protějšky. Bezolovnatá piezoelektrická keramika se tak stala žhavým tématem v posledních letech. Nicméně výzkumy na praktické využití bezolovnatých piezoelektrických materiálů jsou jen zřídka publikovány. V této diplomové práci byl vybrán jeden z nadějných kandidátů na piezoelektrickou bezolovnatou keramiku (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 za účelem zkoumání metody snížení jeho vysoké teploty slinování pomocí dotování uhličitanem lithným, kde syntéza prášku byla připravená pomocí techniky sol-gel. Výsledky byly srovnány s konvenčním práškem syntetizovaným v pevné fázi. Vzorky vyrobené ze sol-gel prášku dopovaného 0.5% hmotn. uhličitanem lithným a slinované při 1300 °C po dobu 2 hodin vykazovaly d33 = 447 ± 9 pC N–1, teplotu Curie 98.7 °C a velikost zrn 7.0 ± 0.3 m. Další důležitou otázkou pro aplikace bezolovnatého piezoelektrického keramického materiálu je jeho výroba v různých konfiguracích. Použitím techniky odlévání pásky a aditivních výrobních postupů byla piezoelektrická keramika zpracována do tří různých konfigurací (2-2, 3-3 a 1-3), aby se překlenula mezera mezi materiálovými vědami a materiálovým inženýrstvím. Pro dolévání pásky byly použity suspenze na bázi oleje a vody. Pro přípravu neslinutých keramických fólií bez trhlin, byly pro odlévání na bázi oleje vyvinuty uhlíkové suspenze s obsahem pevných látek 25% hmotn. a BCZT suspenze s obsahem pevných látek 65% hmotn. Problém práškové hydrolýzy ve vodných suspenzích byl vyřešen povrchovou úpravou prášku Al(H2PO4)3, což umožnilo, aby byly tlusté vrstvy bez trhlin odlety v jednom kroku. Tlusté vrstvy slinované při 1500 °C vykazovaly relativní dielektrickou konstantu 1207, dielektrickou ztrátu 0.018 při 1 kHz, remanentní polarizaci 7.54 µC/cm2 a koercitivní síla intenzity pole (Ec) 0.23 kV/mm při 3 kV/mm. Pro tvarování BCZT v konfiguraci 3-3 a 1-3 byla použita přímá metoda tisknutí inkoustu. Pro správnou úpravu tiskového procesu byla použita inkoustová náplň s viskoelastickým chováním obsahující 41.6% obj. pevných látek BCZT a se zpracovatelskými přísadami (HPMC ~ 2.4% a PEI ~ 0.03%). Vzorky v konfiguraci 3-3, slinované při 1500 °C, vykazovaly nejvyšší dielektrické a piezoelektrické vlastnosti, kde Curieho teplota = 86 °C, tan = 0.021, remanentní polarizace = 4.56 µC/cm2 a d33 = 100 ± 4 pC/N. Vzorky v konfiguraci 1-3 slinované při 1500 °C, které byly smíchány s epoxidem, vykazovaly dielektrickou konstantu 144 a dielektrickou ztrátu 0.035 při 1 kHz. Tato práce popisuje tvarování bezolovnaté piezoelektrické keramiky s vynikajícími vlastnostmi v pokročilých strukturách jako krok k návrhu pro moderní senzorické a energy harvesting aplikace.
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Elbagerma, Mohamed A. "Analytical method development for structural studies of pharmaceutical and related materials in solution and solid state : an investigation of the solid forms and mechanisms of formation of cocrystal systems using vibrational spectroscopic and X-ray diffraction techniques." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4467.
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Analysis of the molecular speciation of organic compounds in solution is essential for the understanding of ionic complexation. The Raman spectroscopic technique was chosen for this purpose because it allows the identification of compounds in different states and it can give information about the molecular geometry from the analysis of the vibrational spectra. In this research the ionisation steps of relevant pharmaceutical material have been studied by means of potentiometry coupled with Raman spectroscopy; the protonation and deprotonation behaviour of the molecules were studied in different pH regions. The abundance of the different species in the Raman spectra of aqueous salicylic acid, paracetamol, citric acid and salicylaldoxime have been identified, characterised and confirmed by numerical treatment of the observed spectral data using a multiwavelength curve-fitting program. The non-destructive nature of the Raman spectroscopic technique and the success of the application of the multiwavelength curve-fitting program demonstrated in this work have offered a new dimension for the rapid identification and characterisation of pharmaceuticals in solution and have indicated the direction of further research. The work also covers the formation of novel cocrystal systems with pharmaceutically relevant materials. The existence of new cocrystals of salicylic acid-nicotinic acid, DLphenylalanine , 6-hydroxynicotinic acid, and 3,4-dihydroxybenzoic acid with oxalic acid have been identified from stoichiometric mixtures using combined techniques of Raman spectroscopy (dispersive and transmission TRS), X-ray powder diffraction and thermal analysis. Raman spectroscopy has been used to demonstrate a number of important aspects regarding the nature of the molecular interactions in the cocrystal. Cocrystals of salicylic acid - benzamide, citric acid-paracetamol and citric acid -benzamide have been identified with similar analytical approaches and structurally characterised in detail with single crystal X-ray diffraction. From these studies the high selectivity and direct micro sampling of Raman spectroscopy make it possible to identify spectral contributions from each chemical constituent by a peak wavenumber comparison of single-component spectra (API and guest individually) and the two- component sample material (API/guest), thus allowing a direct assessment of cocrystal formation to be made. Correlation of information from Raman spectra have been made to the X-ray diffraction and thermal analysis results. Transmission Raman Spectroscopy has been applied to the study cocrystals for the first time. Identification of new phases of analysis of the low wavenumber Raman bands is demonstrated to be a key advantage of the TRS technique.
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Valle, Orero Jessica. "Dynamics and thermal behaviour of films of oriented DNA fibres investigated using neutron scattering and calorimetry techniques." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2012. http://tel.archives-ouvertes.fr/tel-00734670.
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The majority of structural studies on DNA have been carried out using fibre diffraction, while studies of its dynamics and thermal behaviour have been mainly performed in solution. When the DNA double helix is heated, it exhibits local separation of the two strands that grow in size with temperature and lead to their complete separation. This work has investigated various aspects of this phenomenon. The experiments reported in this thesis were carried out on films of oriented fibres of DNA prepared with the Wet Spinning Apparatus. Thus, sample preparation and characterisation are essential parts of the research. The structures of two forms of DNA, A and B, have been explored as a function of relative humidity at fixed ionic conditions. A method to eliminate traces of ever-present B-form contamination in A-form samples was established. The high orientation of the DNA molecules within the samples allowed us to investigate dynamical fluctuations and the melting transition of DNA using neutron scattering, which can provide the spatial information crucial to understand a phase transition, probing the static correlation length along the molecule as a function of temperature. The transition has been investigated for A and B-forms in order to understand its dependence on molecular configuration.Furthermore, after the first melting, denatured DNA films show typical glass behaviour. Their thermal relaxation has been explored using calorimetry.Neutron and X-ray inelastic scattering (INS and IXS) were used in the past to measure longitudinal phonons in fibre DNA, and the results shown disagreement. Recent INS measurements supported with phonon simulations have been crucial to understand the different dispersion curves reported to date. Experiments using INS and IXS have been carried out to continue with this investigation. Attempts to observe the transverse fluctuations associated to the thermal denaturing of DNA, never experimentally investigated before, have been made.
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Khadeeva, Liya. "Photo-isomerization and photo-induced NO release in ruthenium nitrosyl compounds." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S067/document.
Full textAbstract:
Ce travail de thèse est centré sur l'étude expérimentale de deux types de transformations photo-induites observées dans différents complexes métalliques (Fe, Ru, ...) à ligand nitrosyle: (i) la photo-isomérisation au cours de laquelle le ligand NO passe d'un état lié par l'azote (M-NO, état stable GS) à un état lié par l'oxygène (M-ON, état métastable MSI). C'est un processus réversible et un second état métastable, 'side-on' MSII est observable au cours du processus inverse, MSI --> 'side-on' MSII --> GS; (ii) la libération photo-induite du radical NO°. La photo-isomérisation a été étudiée dans le système [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O (sur monocristal) par la diffraction des RX, l'absorption visible statique et l'absorption UV-Vis résolue en temps. Nous avons pu mettre en évidence un processus d'absorption de photons (473 nm) en deux étapes, suivre la dynamique des transformations directes et inverses par l'évolution des paramètres de maille et des l'absorption optique visible, caractériser structuralement l'état 'side-on' MSII. La nature de l'état intermédiaire, MSII, lors du processus direct semble être différente de l'état 'side-on' mais la très faible population de cet intermédiaire n'a pas permis de trancher définitivement. Le rôle de la molécule d'eau dans la maille du complexe [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O a été testé par diffraction des RX sur les échantillons hydratées, déshydratées et réhydratées. L'effet de déshydratation sur l'évolution des paramètres de maille et sur la génération d'espèces MSII au cours de la photo-commutation inverse, MSI --> MSII --> GS, est présenté. La libération photo-induite du radical NO° a été étudiée dans une solution d'acétonitrile du complexe trans-(Cl,Cl)[Ru^{II}(FT)Cl_2(NO)]PF_6 par spectroscopies d'absorption UV-Vis et Mi-IR, statiques et résolues en temps. En observant la dynamique ultra-rapide de la photo-transformation, nous avons mis en évidence un processus d'absorption de photons (406 nm) en deux étapes. La nature de l'état intermédiaire est discuté par rapport à de récents calculs théoriques et au processus de photo-isomérisationThis Ph. D. thesis is focused on the experimental study of two photo-induced processes observed in various [ML_5NO] complexes, where M=Fe, Ru, ..., L=CN, Cl, ... : (i) photo-isomerization, where the system goes from N-bound state (M-NO, stable GS state) to O-bound state (M-ON, metastable MSI state) and a second metastable state, 'side-on' MSII is observed during the inverse photo-transformation, MSI --> 'side-on' MSII --> GS; (ii) photo-induced release of NO° radical. The photo-isomerization is investigated in single crystals of [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O compound by means of X-Ray diffraction, steady state visible and time-resolved UV-visible absorption spectroscopies. During these experiments we observed the evidence of a two-step photon absorption process (473 nm), we followed the dynamics of direct and inverse photo-switching by the evolution of lattice parameters and absorption in the visible range and we caracterised the structure of 'side-on' MSII state. The nature of MSII in the direct photo-switching, GS --> MSI, seems to be different from the 'side-on' configuration, however, we do not have a direct access to this state due to its low population. The role of water molecule in the unit cell of [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O complex was tested by X-Ray diffraction studies on hydrated, dehydrated and rehydrated samples. The effect of sample dehydration on the unit cell parameters evolution and MSII species generation during the MSI --> MSII --> GS inverse photo-switching is presented. The photo-induced NO° release in trans-(Cl,Cl)[Ru^{II}(FT)Cl_2(NO)]PF_6 system in acetonitrile solution is studied by the UV-visible and mid-IR absorption spectroscopies, both steady state and time-resolved. By observing the ultra-fast dynamics of photo-transformation we evidenced a two-step photon absorption process (406 nm). The nature of intermediate state is discussed within the recent theoretical calculations and the photo-isomerization process