Dissertations / Theses on the topic 'XANES'
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Ferrand, Jessica. "Le phénomène de brunissement des vitraux médiévaux : critères d’identification et nature de la phase d’altération." Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1174/document.
Full textThe medieval stained glass windows, which glass composition contain manganese, are often affected by an alteration commonly designated as "browning". This phenomenon results in the presence of Mn-rich brown spots at the surface or subsurface of the glass thus limiting the passage of light and hindering the interpretation of the artwork. Poorly documented, the occurrence of browning among stained glass windows is not precisely described. Currently, one of the major problems in terms of conservation and restoration is that long-term treatments are not available. In these conditions, the recommendations are not to treat the affected glasses, a solution that satisfies neither the architects nor the curators, nor the restorers. In order to answer the questions and expectations of curators and restorers the comprehension of this phenomenon is essential. In this work, a panel of 24 historical and 3 archaeological stained glass samples were studied by microscopic and spectroscopic methods in order to i) establish reliable criteria for identifying the browning phenomenon due to manganese and ii) obtain information on the nature of the dark phases and the oxidation state of manganese in these phases. In parallel with the study of ancient samples, synthetic glasses with medieval-like compositions were synthesized for: i) understanding the reaction between manganese and iron, as well as the influence of the process parameters on the color of glasses and ii) studying the influence of bacteria in the development of the browning phenomenon
Gatuingt, Laure. "Etude des mécanismes de formation des patines manganésifères des grès du château de Lunéville." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1085/document.
Full textThe formation of iron and/or manganese black patina on sandstone buildings is a phenomenon observed for various environments but which is not fully understood yet. The palace of Lunéville, in eastern France, is an interesting example because it has patinas that have developed in different conditions : some seem to have grown naturally while others have appeared on stones which were exposed to a fire. These stones experienced an increase of their surface temperature, but most of all, they were subjected to a substantial volume of water as part of attempts to extinguish the fire. The goal of this thesis is to understand the formation of the patinas by investigating different sandstone facies collected from the palace of Lunéville and from quarry. In order to understand the influence of the sandstones intrinsic parameters, the patinated and unpatinated facies were compared from petrophysical, chemical and mineralogical point of view, using laboratory techniques (optical and electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction, Raman spectrometry, permeability, porosity and capillarity measurements, ...) and large instruments (Particle Induced X-ray Emission (PIXE) on the AGLAE proton accelerator, X-ray micro-diffraction analysis and X-ray absorption micro spectroscopy (XANES) at the SOLEIL synchrotron). In addition to this characterization, patinas coming from different environments were also compared in order to extract the main extrinsic parameters. Finally, the dynamical aspect of the release of manganese from the sandstones was investigated by conducting dissolution experiments at various pH, and by demonstrating the possibility to recreate a Mn patina in laboratory, using sandstone imbibition techniques. The results allow to propose a model for the patina formation based on the dissolution of the Mn-phases initially present in the sandstones’ bulks, followed by the migration through the porous network towards the surface of the ions released in the solution
Mizoguchi, Teruyasu. "Study of Local Atomic and Electronic Structures in Ceramic Materials by ELNES and XANES." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149775.
Full textNemausat, Ruidy. "Etude expérimentale et théorique des fluctuations thermiques quantiques des noyaux par spectroscopies d'absorption X et RMN." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066158/document.
Full textIn this thesis the impact of quantum thermal fluctuations on XANES and solid-state NMR spectra is described using an experimental and theoretical joint study. This project has two components. First, high-quality experimental data are acquired in order to observe and understand the influence of quantum vibrations in light-elements oxides. Second, a theoretical model is set up to reproduce the effects observed experimentally and describe their origin from a fundamental point of view. The developed theoretical approach is based on the density-functional theory. Within the Born-Oppenheimer and quasiharmonic approximations, the quantum thermal fluctuations of nuclei are modeled by generating atomic configurations obeying quantum statistics at finite temperature. The XANES spectra and NMR parameters are subsequently calculated in these configurations and the average results are compared with spectroscopic data at finite temperature. This approach has been validated by a joint theoretical-experimental study conducted in a series of light-element oxides, where the results were found to be in excellent agreement with the original experimental data. In addition, it is shown that the impact of the quantum fluctuations of the nuclei is influenced by the local symmetry of the probed atomic site
Marcaillou, Clément. "Serpentinisation et production d'hydrogène en contexte de dorsale lente : approche expérimentale et numérique." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00676948.
Full textPiton, Marcelo Rizzo. "Síntese e caracterização do composto SrTi1-xMnxO3 nanoestruturado." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-29012015-215637/.
Full textNanostructured SrTi1-xMnxO3 (STM) powder samples with x = 0%, 0.5%, 1%, 2.5%, 5% and 10% were synthesized by the polymeric precursors method. The thermal, structural and optical properties of STM samples heat-treated at different temperatures were analyzed by thermal analysis, X-ray diffraction, X-ray absorption spectroscopy and photoluminescence techniques. The thermal analysis results have shown that manganese ion causes a retarding effect, increasing the onset of the crystallization temperature. The XRD results showed that manganese ion is incorporated in a solid solution in the B site of the SrTiO3 (ST) network for the range of solubility studied, with oxidation states between +3.4 and +3.7, indicating the creation of charge compensation defects, keeping the materials electrical neutrality. The analysis of the photoluminescence (PL) spectra of the STM amorphous samples showed that the PL intensity increases when the amount of manganese is up to 1%. However, higher manganese concentrations leads to a pronounced decrease of the photoluminescence intensity. The amorphous samples showed no significant change of the local order around the titanium atoms, observed as well as in the oxidation state of the manganese atoms as the amount of manganese increases. Thus, the variation of the photoluminescence intensity cannot be explained by these factors. Increasing the calcination temperature leads to a significant decrease of the photoluminescence intensity. An analysis of the XANES spectra measured at the titanium K edge of these samples showed that as the calcination temperature increases, i. e., as it increases the degree of crystallinity, the ordering of the Ti atoms in the oxygen octahedra TiO6 of the samples increases.
Benali, Cherif Nourredine. "Etude structurale de complexes de cuivre par diffraction et spectroscopie d'absorption X (EXAFS et XANES)." Aix-Marseille 3, 1994. http://www.theses.fr/1994AIX30038.
Full textGorczyca, Agnès. "Caractérisation de catalyseurs métalliques supportés par spectroscopie XANES, apports du calcul quantique dans l'interprétation des spectres expérimentaux." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI062/document.
Full textThe study of metallic nanoclusters supported on oxides is of paramount fundamental and technological importance, particularly in the field of energy. The nanoparticles based on platinum supported on gamma alumina are widely used as highly dispersed heterogeneous catalysts especially under reducing hydrogen atmosphere. Their reactivity and selectivity are intimately related to the local geometry and the electronic density of active sites. These are particularly difficult to define, given the very small size of the studied particles (about 0.8 nm in diameter). XANES (X-Ray Absorption Near Edge Structure) spectroscopy requiring synchrotron radiation, is one of the most appropriate tools to study these systems, especially in situ, at the atomic scale. Indeed the XANES spectra are influenced by the geometry and symmetry of the atoms local environment (especially angles between bonds), the degree of oxidation, the bond types involved, and the electronic structure of the system . All these factors are nevertheless difficult to differentiate and even to interpret. It is therefore impossible to infer accurately the structure of the metal particles by experience alone, without any comparison with simulated spectra. The establishment of theoretical models becomes necessary. We are implementing an approach that combines high-resolution XANES experiments in situ and quantum simulations, the latter aimed at proposing relevant structural models to quantify the reactivity of the particles and calculating spectral characteristics for comparison to experiment. The identification of the clusters morphologies, the metal-support interaction and the hydrogen coverage is made possible combining experiments and quantum calculations. The library of existing monometallic Pt particles models supported on Gamma alumina with or without adsorbed hydrogen, is refined. New models considering the two main surface of Gamma alumina, the particle size and hydrogen adsorption are developed. This extended library of models enabled a study of the effect of particle size, morphology, electronic structure, different alumina faces, and the hydrogen coverage on the signature of XANES spectra. This first study of monometallic platinum catalysts, concludes with the discrimination of the morphologies, but especially with the quantification of the hydrogen coverage of the particles for each temperature and hydrogen pressure experimental condition. Then, models of bimetallic Platinum-tin particles supported on the (100) Gamma alumina face are performed with hydrogen adsorption. These models provide insights into the effect of tin on the morphology, the electronic properties and the interaction with the support and hydrogen of these clusters. Different compositions were explored, which provided information on the dilution of platinum by tin. The adsorption of hydrogen was then studied on Pt10Sn3 clusters supported on the (100) face of alumina. Although many parameters are not yet included in these models, the comparison to the experience already provides a first approximation to the description of bimetallic systems
Fernandes, Alessandro. "Síntese e caracterização do composto SrTi1-XNbXO3 nanoestruturado." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-15082012-125906/.
Full textNanostructured \'SR\'TI IND.1-x\'NB IND.x\'O IND.3\' samples in a powder form containing up to 10 mol% of niobium have been prepared by the polymeric precursor method. The thermal, structural and optical properties of these samples were characterized by different techniques. The results show that in the limit of concentration of niobium added to the samples, the dopant was incorporated into the \'SR\'TI\'O IND.3\' matrix lattice forming a \'SR\'TI IND.1-x\'NB IND.x\'O IND.3\' solid solution. The increasing on the amount of niobium leads to an increased agglomeration of the particles as well as an increase in the crystallization temperature of the samples. In good agreement with the literature data, a significant photoluminescence intensity was only observed in amorphous or partially crystalline samples. Samples in the form of thin films were obtained using the electron beam evaporation technique. X-ray diffraction (XRD) show that in certain compositions, beyond the \'SR\'TI\'O IND.3\' phase, it was also observed the presence of phase \'SR\'CO IND.3\' phase. Through the XRD and Atomic Force Microscope (AFM) results, it has been observed that, as in the case of the samples in powder form, the concentration of niobium inhibits the crystallization process of the sample. Electrical resistance measurements showed that all samples, independent of the concentration of niobium, present higher values of resistance of the order of \'10 POT.15\' \'ômega\' . This value is much higher than expected and reported in the literature and does not allowed to measure the sensibility of thin films to different species of gases.
Santos, Sheila Renata. "Dinâmica do fósforo no solo em função da adição de ácidos orgânicos de baixa massa molar." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-10052016-131749/.
Full textPhosphate fertilization of acidic, highly weathered soils is inefficient because of the adsorption of phosphorus (P) to 1:1 silicate clays and, especially, to Fe and Al oxides. Different soil management practices to induce solubilization of unavailable forms of P to plants nutrition have been intensively studied in recent years. The mobilization of P with anions of low molecular weight organic acids (LMWOA) increases the concentration of available P in the soil solution for plant uptake. Anions derived from LMWOA exudates from plants root or excreted by microbes are associated with some rhizosphere conditions, as deficiency of P and Al phytotoxicity, and they interact with the soil in order to increase P availability. Depending on the soil attributes, and degree of dissociation, properties, and number of carboxyl groups from organic anions, P can be mobilized from soil mainly because of complexometric dissolution of soil minerals and ligand exchange of functional carboxyl groups and P adsorbed in soil surface sites. The capacity of citrate, malate and oxalate anions to mobilize P from a Typic Quartzipsamment (RQ) and an Anionic Acrudox (LVwf) was evaluated in a column leaching study. Because no P was detectable in columns effluents from LVwf, another column leaching study was performed, but only citrate was leached with a greater volume of solution, and citrate-induced changes at P forms in the soil were identified by P K-edge X-ray absorption near edge structure - XANES - spectroscopy. The capacity of LMWOA anions to solubilize P was more dependent of P status and other soil attributes, than number of carboxyl groups of organic anions. Only oxalate mobilized P from RQ, and all LMWOA anions were able to mobilize P from LVwf. Increasing of P mobilization and soil pH were followed by increases of Al mobilization from RQ (pH water = 5), and Ca mobilization from LVwf (pH water = 5.6) at lower volumes of LMWOA anions leaching. Phosphorus was solubilized by complexation of Al, Ca or Fe from insoluble phosphate minerals, or by inhibition of Al, Ca or Fe phosphate precipitation. After leaching a greater volume of citrate through LVwf, P was still undetectable in effluents from columns, but there was an intensively leaching of Al and Fe, as well as changes in proportions of adsorbed P characterized in soil XANES spectra. Although we have found evidences about the action of main mechanisms of P solubilization (complexometric dissolution, and ligand exchange of carboxylic functional groups for adsorbed P on soil minerals) by LMWOA anions, they had a little potential to really increase P availability.
Muñoz, Manuel. "Comportement d'éléments formateurs et modificateurs de réseau dans des magmas hydratés." Marne-la-Vallée, 2003. https://tel.archives-ouvertes.fr/tel-00008421.
Full textThis study consists of a better understanding of physical and chemical properties of hydrated magmatic systems associated to subduction zones. We are particularly interested in determining the behavior of network modifiers “trace” elements (Ni and Zr), as well as network formers major elements (Ga and Ge) in this kind of geomaterials. The study is essentially based on an experimental approach, using high-pressure systems (diamond-anvil cell, Paris-Edingurgh press) coupled to X-ray Absorption Fine Structure (XAFS) spectroscopy. For the different chemical systems studied, the results collected under high temperature and/or high pressure show well different behavior for nickel and zirconium as a function of water content. The local structural environment of nickel is highly affected by the presence of water, suggesting a significant interaction between nickel and the aqueous phase. In contrast, the local structure around zirconium is practically unchanged. Moreover, for major analog elements (Ga and Ge), no significant structural modification is observed as a function of temperature, pressure or water content; suggesting possibly that water does not depolymerize the silicate network. Additional experiments shown the usefulness of XANES (X-ray Absorption Near Edge Structure) spectra for determining, in situ, nickel contents as well as densities of hydrous silicate magmas. Results show a “water/silicate” partitioning coefficient near 0. 2; suggesting a low but significant mobilization of nickel by the aqueous phase during the magmatic ascension. Also at around 780 °C / 520 MPa, the apparent-density of hydrated magmas near 1 g/cm3, suggests a structural aspect of “emulsion” type including particularly high water content, as well as a very important dynamic of magmatic ascension in its homogeneous flow regime
Rigault, Cécile. "Cristallochimie du fer dans les chlorites de basse température : implications pour la géothermométrie et la détermination des paléoconditions redox dans les gisements d'uranium." Poitiers, 2010. http://theses.edel.univ-poitiers.fr/theses/2010/Rigault-Cecile/2010-Rigault-Cecile-These.pdf.
Full textIn contexts of uranium deposits, redox conditions constitute the main factor controlling the uranium deposition. Often observed in these deposits, chlorites are the unique clay mineral which can be able to record in their structure the redox conditions through their Fe3+/SFe ratio. However, the common presence of several populations of chlorites makes difficult to understand the message carried out by these minerals. Thanks to µ-XANES spectroscopy, we are now able to measure on thin sections the Fe3+/SFe ratio in chlorites with an accuracy of 5 %. Measurements show that it can reach 60 % in di-trioctahedral chlorites and 5 % to more than 40 % for trioctahedral chlorites. In hydrothermal contexts where chlorites crystallize through a dissolution-recrystallization process, their Fe3+/SFe ratio decreases with the increase of the global Fe content. Diagenetic chlorites observed resulting from the polymorphic transformation of berthierine have a different behavior because there is no link between their total iron content and their Fe3+/SFe ratio: their chemistry is directly inherited from the one of the precursor mineral because this transformation does not allow a reorganization of cations in the structure. This transformation explains that thermodynamic models cannot work for these phases. For the use of chlorites as makers of redox paleoconditions in contexts of uranium deposits where diagenetic and hydrothermal chlorites can be present, it is decisive to determine their origin, for example analyzing their polytype: Ib (b=90°) for chlorites crystallized from solid-state transformation and IIb for chlorites crystallized through dissolution-recrystallization process
Mantovani, Françoise Cagniant D. "Réactivité et propriétés spectrographiques en série benzo (b) sélénophénique." Metz : Université de Metz, 2008. ftp://ftp.scd.univ-metz.fr/pub/Theses/1972/Mantovani.Francoise.SMZ7203.pdf.
Full textBaca, Manuel. "Oxydation sélective du propane en acide acrylique su des oxydes mixtes MoVTeNbO et MoVSbNbO." Lyon 1, 2004. http://www.theses.fr/2004LYO10134.
Full textThe selective oxidation of propane into acrylic acid has been studied over one of the most promising catalysts which is a MoVTe(Sb)NvO mixed metal oxide. We have confirmed that this catalyst may contained several phases. These phases have been identified, prepared and tested separately. The study clearly showed that the active and selective phase of the catalysts was a new phase. We have characterizd this phase usign several techniques (EXAFS, XANES, SPS, ESR. . . ) that allowed to determine its total stoichiometry which was (Te iv O)1,3V iv 3,3 Vv 0,3 Mov 1,0Movi 13,3Nbv 2,0 O56. Another phase which gave a synergy effect in mixture with the first one has also been characterized. Its stoichiometry was (Te iv O)1,8V iv 1,2Vv 0,1 Mov 0,6Movi 3,7Nbv 0,4O18. The synergy effect observed between the two phases has been studied and explained
Warburton, D. R. "Surface EXAFS and XANES studies of sulphur absorption on the (110) and (111) faces of nickel." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237271.
Full textMonir, Mehdi. "XANES study of chemistry of localised corrosion in artificial pits of 316L stainless steel and titanium." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3258/.
Full textWeißhaupt, Jannick. "Ultrafast Modulation of electronic Structure by coherent Phonon Excitations in ionic Crystals." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/21400.
Full textThis thesis explores the subtle interplay between electronic and nuclear excitation in the Raman effect with time resolved XUV absorption spectroscopy. Coherent stimulated Raman scattering, the type of Raman interaction we induce, is a variant of the well known Raman scattering, where a sufficiently short pulse excites nuclear vibrations coherently, i.e. with actual displacement of the nuclei. In standard Raman scattering, due to its incoherent, spontaneous nature, there is no displacement of nuclei. We were able to observe nuclear displacements as small as 10^-4 in real time by their effect on the XUV absorption spectrum. Specifically we studied non-resonant NIR pump XUV probe absorption spectroscopy on lithium borohydride (LiBH_4). In the XUV absorption experiments in this thesis we concentrate on the Lithium K-edge absorption spectrum around 60 eV which consists of a strong excitonic peak at the onset of absorption and a plateau at higher energies. Upon excitation with a NIR pulse we observe oscillatory changes in the absorption spectrum with a frequency of 10 THz, which we identify as the effect of coherent phonon excitations of an external A_g phonon mode. The coherent oscillation changes the distance between Li^+ anions and BH_4^- cations, which modifies the electronic environment around the Li anion. XUV absorption spectroscopy, especially XANES, is highly sensitive to such changes of the chemical environment around the absorbing atom. We use two different approaches to derive the absolute displacement, which are observed in the experiment. Our results allow for a fascinating new insight into Raman scattering as they connect a direct observation of the driving mechanism, the induced polarization, with a direct observation of the outcome the oscillatory nuclear displacement. With XUV absorption spectroscopy nuclear displacements in the order of 10^-4 A were resolved with sub picosecond accuracy in the time domain.
Loos, Michel. "Contribution au développement des spectroscopies d'absorption et d'excitation X : application à l'étude structurale des espèces catalytiques actives dans un procédé industriel d'oxychloration de l'éthylène." Nancy 1, 1990. http://www.theses.fr/1990NAN10483.
Full textAlbertelli, Marine. "Etude de la transformation des formes chimiques du mercure par des bactéries sulfato-réductrices à différentes échelles d'observation." Thesis, Pau, 2017. http://www.theses.fr/2017PAUU3031/document.
Full textMercury is a wide spread pollutant that build up in living tissues. The transformation of mercury into methylmercury is primarily a natural and biological process mediated by anaerobic bacteria. Understanding the parameters influencing the formation of methylmercury is critically important due to its highly toxic, bioaccumulative and persistent nature. Herein we aim to study the mechanism by which model strains used in laboratories can transform inorganic and methylmercury. The objectives of this study are determining where mercury methylation and demethylation processes take place at the cell scale and identifying the mercury ligands involved in these processes. At first, the toxicity of inorganic mercury (IHg) and MMHg were measured on the bacterial growth. The methylation and demethylation potentials, the localization of mercury and its ligands were determined in the culture and at the cell scale. These parameters were evaluated at different concentrations of mercury as well as during kinetic. This study has highlighted that IHg and MMHg have less impact on the growth of both strains in sulfate reduction because of the high precipitation of mercury. One or more limiting steps would occur in the methylation process. In addition, a difference in cell localization of mercury has been observed over time, suggesting an export at 24h of exposure. Mercury localization also depends on the bacterial strain suggesting different cell mechanisms. TEM EDX imaging and elemental analysis by X-ray nano-fluorescence showed mercury co-localized with sulfur. The study of HR XANES speciation confirmed the predominance of thiol ligands associated with methylation and demethylation processes. A tetragonal form is predominant in samples exposed to growing HgCl2 suggesting that this species is formed via a biological process
Orthous-Daunay, François-Régis. "Empreinte moléculaire des processus post-accrétionnels dans la matière organique des chondrites carbonées." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENU017/document.
Full textType 1 and 2 carbonaceous chondrites include the most chemically and petrologically pristine meteorites. This intactness goes along with the abundance of organic matter which is a phase of choice to investigate the presolar material processing in the nebula and then on the first bodies. The purpose of this thesis is to study the influence of post-accretional processes on the molecular characteristics of organic matter and in particular the extent of oxidation effects due to aqueous alteration. We have carried out a comparative study based on the carbon structure and functional analysis of more than ten meteorites whose geologic histories were independently determined. The redox degree of sulfur in the insoluble fraction was measured by SK-Xanes spectroscopy. FT-IR spectroscopy gave access to the fine structures of aliphatic chains and oxygen-rich functions. Orbitrap very high resolution mass spectrometry was used to describe the heteroatomic diversity of soluble molecules in the Renazzo (CR2) chondrite. The aliphatic chains of CI chondrites and Murchison differ from others by a higher and unchanging abundance of methyl groups. Type 1 chondrites are the only carriers of oxidized sulfur functions whereas the sulfur speciation in type 2 chondrites is invariable. For all studied chondrites, the carbonyl groups are mainly under the form of ketones and their abundance can’t be related to the degree of aqueous alteration. Any parameters we have measured in this study lead us to conclude that the molecular variability among type 1 and 2 carbonaceous chondrites are less due to the footprint left by the hydrothermal activity than due to the heterogeneity of an organic precursor accreted by each parent body. In particular, our measurements invalidate the hypothesis that the alteration would cause an oxidative conversion of aliphatic chains to carboxylic acid functions
Paris, Eleonora. "Structural studies of minerals and glasses by X-ray absorption spectroscopy." Thesis, University of Bristol, 1996. http://hdl.handle.net/1983/2eab35bf-1d11-4dca-9901-6e3e32e51931.
Full textTitov, Andrey. "Electronic properties of the diluted magnetic semiconductors : Ga1-xMnxN, Ga1-xMnxAs, Ge1-xMnx." Université Joseph Fourier (Grenoble), 2006. http://www.theses.fr/2006GRE10285.
Full textElectronic properties of the diluted magnetic semiconductor (Ga,Mn)N were studied by x-ray absorption spectroscopy at the K-edge of Mn. The measured x-ray absorption spectra were further interpreted using the ab-initio calculations. Two pre-edge absorption lines are observed in the x-ray absorption spectra: the first line was attributed to electronic transitions into 3d states of Mn of spin up, while the second line corresponds to transitions into 3d states of Mn of spin down. This interpretation allows us to determine the valence state of Mn: two absorption lines are present in the pre-edge structure of Mn3+ and only one line remains in case of Mn2+. Such a change of the pre-edge structure was checked experimentally on (Zn,Mn2+)Te and on (Ga,Mn2+)As. In addition, the distribution of Mn in (Ga,Mn)N can be studied using the interpretation: the shape of the spectra points to a homogeneous distribution of Mn in our (Ga,Mn)N samples
Tobase, Tsubasa. "Experimental investigation for local structures of IVb transition metal elements in minerals and glasses formed under extreme conditions." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0200/document.
Full textElucidation of the formation mechanism of various natural glasses can help to understand the dynamics of the Earth because these materials record the formation condition in their structures. XAFS applied to natural meteorite-related glasses provides information about the local structural changes of elements therein. By performing high-accuracy XAFS analyses for trace elements and their local structure in sedimentary rocks, in the glass phase of meteorites and in the meteorite impact-related glasses such as tektite and impact glass, information on the formation condition of these materials can be obtained. We have performed local structure analysis of IVb transition metal elements (Ti, Zr) in natural minerals and glasses K-edge XANES and EXAFS as well as high-temperature laser heating and gas flow experiments on zircon, to observe structural changes at high temperature in the crystalline phases that accompany the meteoric glass. The local structure of these materials is similar to that of of Zr in K-Pg sediments, which do not show any influence from diagenesis and weathering, suggesting that K-Pg sediments maintain the thermal quenching history of the meteorite impact. However, the low abundance of Zr in sediments prompted us to study Ti, which belongs to the same group as Zr and is much more abundant. Combination of the information about the local structures of Ti and Zr allows a higher reliability for the estimation of meteorite impact event. The local structure of Zr in the fusion crust and inner glassy part of the Martian meteorite of Tissint are similar, respectively, to that in tektite and accompanying impact glass and to that in baddeleyite and fulgurite. The latter was likely vitrified part during the passage through the atmosphere. It should be possible to estimate the conditions of meteorite impact on Mars and the passage of meteorites through the Earth’s atmosphere through the analysis of the local structure of Zr in the glassy part of meteorites. In order to confirm this hypothesis, we performed heating experiments of zircon with in-situ powder X-ray diffraction experiment was performed for ZrSiO4 and ZrO2. SEM analysis confirmed evaporation of the SiO2 component. We have obtained a new ZrO2-SiO2 phase diagram where the liquid-immiscible region proposed earlier does not appear
El, Kari Hamza. "Croissance des molécules aromatiques sur substrat d'Au(111)." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP042.
Full textOrganic molecules adsorbed on surfaces offer numerous perspectives to build real molecular nano-machines with different electronic (memories, logic functions), optical (photon nanosources) or mechanical (motors) functions. The scanning tunneling microscope, with an ultimate spatial resolution of 0.1 nm (nanometer), is the ideal tool for exploring these electronic, optical and mechanical properties at the single-molecule scale. In this PhD thesis, the growth of large aromatic molecules was carried out on the Au(111) surface. Organic polycyclic aromatic hydrocarbon molecules have been used to fabricate different nanostructures. The growth of these molecules was explored by scanning tunneling microscopy (STM) which revealed their self-assembly in the form of columns while scanning tunneling spectroscopy (STS) gave the access to the local electronic structure of these nanostructures. The columnar structure presents a semiconductor character while the isolated molecules present a metallic character. Photoelectron spectroscopies (XPS) and near edge X-ray absorption fine structure (NEXAFS) indicated that these molecules are adsorbed flat on the gold surface. Theoretical calculations carried out as part of the ANR-BOGART project have helped to understand these structures
Burresi, Emiliano. "Ab-initio determination of x-ray absorption near edge structure (xanes) spectra in an ultrasoft and norm conserving pseudopotentials scheme." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5937/.
Full textFialho, Batista Ana Teresa. "Atomic scale insight into platinum based catalysts supported on chlorinated gamma-alumina." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEN062.
Full textBifunctional heterogeneous catalysts consisting of metallic sites and acidic sites are used in various processes and the impact of active site proximity in catalytic efficiency can be expressed as an “intimacy criterion” according to the literature. Platinum supported on chlorinated γ-Al2O3 is the traditional catalyst for catalytic naphtha reforming and is at the core of the present work. Herein, a multi-technique approach, including HR-HAADF-STEM, electron tomography, high field MAS NMR, HERFD-XANES, EXAFS, and DFT calculations, was applied to determine the location of the metallic and acidic sites on the Al2O3 support crystallites for Pt/ γ-Al2O3 -Cl catalysts and to estimate the distance between such sites. The samples, representative of the industrial catalysts, were synthesized so as to vary the distance between the two types of sites as a function of three key parameters: %Pt, %Cl and γ-Al2O3 crystallite size and shape.By building the first DFT model of crystallite edge between the (110) and (100) surfaces, an improved 1H NMR peak assignment was proposed and it was found that µ1-OH on the edge are preferably exchanged with Cl. STEM analysis showed that reduced Pt nanoparticles are of 0.9 nm and that around 20% of Pt is in the form of single atoms, which are stabilized by Cl. By electron tomography it was revealed that Pt nanoparticles are mostly located on the edges of alumina crystallites and that the quantified inter-Pt particles distance is directly tuned through %Pt. A first geometrical model of the location of Pt and Cl on the catalyst is proposed. The improved understanding of the location of active sites and their proximity in catalytic reforming catalysts gained though this work paves the way to catalyst improvement based on tuning of active site location
Stetten, Lucie. "Spéciation et mobilité de l'uranium dans des sols et des sédiments lacustres en aval d'anciens sites miniers." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS249.
Full textUranium scavenging in soils and sediments located downstream from former U mines is expected to naturally limit uranium dispersion in downstream waterways. However, uranium mobility in such contaminated sites may depend on the identity of U traps as well as the geochemical conditions. The aim of this thesis was to improve our knowledge on the geochemical behavior and the mobility of uranium in U contaminated lacustrine sediments and wetland soils, whose reducing conditions is expected to mitigate uranium mobility because U(IV) species are less soluble than U(VI) ones. X-ray absorption spectroscopy and scanning electron microscopy analyzes combined with geochemical analyzes were carried out. In U contaminated lake sediments, we show that indirect reduction of U(VI) by Fe(II) associated to clay minerals may be a major diagenetic process responsible for the scavenging of uranium. For organic-rich weltand soils, we show a sharp uranium redox boundary mainly controlled by the water-table. For both sites, U(IV) mononuclear species and U(IV)-phosphate minerals were identified as the major species controlling uranium solubility, while uraninite is virtually absent. For the highly U-contaminated wetland soil, we suggest a major uranium redistribution via the oxidative dissolution of U(IV)-minerals followed by U(VI) organic matter complexation. Soil incubation experiments have confirmed these redistribution mechanisms and suggest different geochemical behaviors for lermontovite (U(PO4)(OH)•H2O) and ningyoite (CaU(PO4)2•2H2O). These experiments also highlight the role of organic matter in the control of uranium mobility, favoring the remobilization of U(IV) organic complexes under reducing conditions. Altogether, our results call for the need to consider both non-uraninite U(IV) minerals and mononuclear U(IV) complexes in such anoxic environments as major species controlling uranium solubility
Deniau, Benoît. "Étude des états d'oxydation et de la substitution des éléments constitutifs des phases M1 MoVTe(Sb)NbO pour l'oxydation du propane en acide acrylique." Lyon 1, 2007. http://www.theses.fr/2007LYO10315.
Full textThe study of the M1 phase MoVTe(Sb)NbO, one of the best catalysts for the propane oxidation into acrylic acid has been carried out in two parts : the first one is the substitution of the elements belonging to the M1 phase, the second one is the characterisation of the oxidation states under catalytic conditions. We substitued Mo, V, Nb elements with an oxidation state equal to or higher than IV. The substitution ratio in M1 phase is weak and does not exceed 1 atom out 20. The M1 phase with substitution always shows weaker catalytic performance than the one without substitution even though some specific effects from dopants have been observed. Some hypotheses on the origin of these effects are proposed based on M1 phase characterisation with different techniques. The operando XANES studies allowed us to determine the oxidation states under reaction conditions and to show their sensitivity to temperature and the redox atmosphere
Wispelaere, Sidoine de. "Étude par dynamique moléculaire et diffusion multiple de verres d'intérêt géologique." Université de Marne-la-Vallée, 2005. http://www.theses.fr/2005MARN0227.
Full textPham, Thi Hanh Nguyen. "Speciation and Reactivity of Cr(III) Nutritional Supplements in Biological Media." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/10033.
Full textAsakura, Hiroyuki. "Study of X-ray Absorption Spectroscopy of Heavy Elements and Transient Chemical Species." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/198946.
Full textSilva, Fernando Henrique Martins da. "Estudo da estrutura local de nanopartículas de ferrita de manganês por xanes e difração de nêutrons e raios x." reponame:Repositório Institucional da UnB, 2011. http://repositorio.unb.br/handle/10482/9709.
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Neste trabalho, investigamos as propriedades estruturais locais de fluidos magnéticos à base de nanopartículas de ferritas de manganês. Tais nanopartículas são obtidas durante a etapa de coprecipitação hidrotérmica e são dispersas em meio ácido graças à estratégia núcleo-superfície, o que impede que os nanogrãos sofram a ação corrosiva do ácido. Este tratamento modifica a composição química que pode ser descrita por um núcleo de ferrita estequiométrica e uma camada superficial de composição química γ-Fe2O3 num modelo “core-shell”. Dosagens químicas permitem determinar a fração volumétrica em nanopartículas assim como a espessura da camada superficial. A espectroscopia de absorção de raios x é utilizada para determinar o estado de oxidação médio do átomo absorvedor. Os resultados obtidos pela análise na região de XANES mostram a presença de íons Mn3+ e a presença destes induz distorções chamadas de efeito Jahn-Teller. Difração de raios x e de nêutrons é utilizada a fim de se obter informações sobre a estrutura local dos nanocristais, em particular a distribuição catiônica nos sítios intersticiais da estrutura espinélio. Os resultados apresentados indicam uma inversão catiônica diferente daquela encontrada para a ferrita maciça. O refinamento de Rietveld dos difratogramas de raios x e nêutrons é utilizado para determinar o tamanho médio e o parâmetro de malha das nanopartículas com qualidade e precisão. ______________________________________________________________________________ ABSTRACT
We investigate the local structure of magnetic fluids based on nanosized particles of manganese. These nanoparticles were obtained by soft chemistry method and they are dispersed thanks a core-shell strategy which prevents the acid attack. This treatment modifies the chemical composition of the particles and they can be described as a core of stoechiometric ferrite surrounded by a surface layer with a mean composition of maghemite γ-Fe2O3 in a “core-shell” strategy. Chemical titration allows us to determine the thickness of this surface layer. X-ray absorption spectroscopy is used to determine the mean oxidation state of the absorber atom. The results obtained by XANES analysis shows the presence of Mn3+ ions and such presence induces some distortions known by Jahn-Teller effect. X-ray and neutron diffractions were used to obtain information about the local structure of the nanosized particles, in particular the cation distribution. The results indicate an inversion degree that is different of the bulk ferrite. Rietveld refinement of the x-ray and neutron diffractograms is used to determine the size and lattice parameter with precision and quality.
Nemausat, Ruidy. "Etude expérimentale et théorique des fluctuations thermiques quantiques des noyaux par spectroscopies d'absorption X et RMN." Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066158.
Full textIn this thesis the impact of quantum thermal fluctuations on XANES and solid-state NMR spectra is described using an experimental and theoretical joint study. This project has two components. First, high-quality experimental data are acquired in order to observe and understand the influence of quantum vibrations in light-elements oxides. Second, a theoretical model is set up to reproduce the effects observed experimentally and describe their origin from a fundamental point of view. The developed theoretical approach is based on the density-functional theory. Within the Born-Oppenheimer and quasiharmonic approximations, the quantum thermal fluctuations of nuclei are modeled by generating atomic configurations obeying quantum statistics at finite temperature. The XANES spectra and NMR parameters are subsequently calculated in these configurations and the average results are compared with spectroscopic data at finite temperature. This approach has been validated by a joint theoretical-experimental study conducted in a series of light-element oxides, where the results were found to be in excellent agreement with the original experimental data. In addition, it is shown that the impact of the quantum fluctuations of the nuclei is influenced by the local symmetry of the probed atomic site
Collin, Blanche. "Rôle du silicium sur la tolérance au cuivre et la croissance des bambous." Thesis, Aix-Marseille 3, 2011. http://www.theses.fr/2011AIX30038.
Full textThis study aims at assessing the role of silicon (Si) on the plant growth and alleviation of copper (Cu) toxicity in bamboos. Several approaches have been performed. Firstly, the distribution and variability of Si and Cu were investigated in several bamboo species grown under natural pedo-climatic conditions in order to obtain reference values for Cu and Si in bamboos. Secondly, hydroponic experiments were carried out to characterize the macroscopic response of bamboo plants exposed to Si and Cu and, investigated in parallel the Cu speciation and Si and Cu localisation in different part of bamboos (roots, stems, leaves).Significant differences were measured between bamboo species, suggesting that a genotypic character may be responsible for Si and Cu accumulation. Silicon supplementation modified the Cu speciation but did not induce significant improvement of Cu tolerance. The main strategy of bamboo to cope with high Cu concentrations in its tissues is initially an important sequestration in the roots apoplast, mainly in epidermis, and then a Cu complexation with organic and inorganic sulphur compounds. These results will allow the optimisation of phytoremediation processes using bamboo plants
Abbe, Jean-Baptiste. "Ingénierie de bactéries magnétotactiques pour la bioremédiation du cobalt." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0051.
Full textMagnetotactic bacteria (MTB) are organisms able to synthesize magnetic crystals within a specific organelle, the magnetosome. The assembly of these magnetosomes gives them magnetization and orientation properties in magnetic fields. In the context of the development of biotechnology, we have performed the functionalization of MTBs for cobalt bioremediation applications.We have thus developed vectors suitable for MTB for the expression of enzymatic machineries of Staphylococcus aureus and Pseudomonas aeruginosa allowing the production of metallophores analogous to nicotianamine. We observed a double phenotype, increased resistance toward metals and increased cobalt accumulation in Escherichia coli or MTBs Magnetospirillum magneticum AMB-1 and Magnetospirillum gryphiswaldense MSR-1. We have also observed that the expression of metal import systems such as Rhodopseudomonas palustris NiCoT permease NxiA in strains expressing nicotianamine analogs further increases the accumulation of metals.Moreover, we have shown that the production of these analogs allows a cobalt enrichment of the magnetosomes, but does not lead to a modification of the speciation of this metal in MTB.We introduce here the use of MTBs as cellular chassis for new biotechnological applications
Chevreux, Pierrick. "Comportement de l’uranium et de ses simulants dans les verres d’aluminosilicates en contact avec des métaux fondus." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0257/document.
Full textThis study concerns an innovative process used for conditioning nuclear waste that contain metallic parts contaminated with actinides. High actinides concentrations are expected to be incorporated in the glass melt in contact with the molten metals. Among these metals, aluminum and/or stainless steel impose a strongly reducing environment to the glass melt involving redox reactions. These reactions modify actinides oxidation states and therefore change their solubilities in the glass and could also reduce them into the metallic form. In this work, we focus on the behavior of uranium and its surrogates, namely hafnium and neodymium, in aluminosilicate glasses from the Na2O-CaO-SiO2-Al2O3 system melted in highly reducing conditions. The first step consists in comparing the hafnium and uranium solubilities in the glass as functions of redox conditions and glass composition. A methodology has been set up and a specific device has been used to control the oxygen fugacity and the alkali content of the glass. The results show that uranium is far less soluble in the glass than hafnium (HfIV) in reducing conditions. The uranium solubility ranges from 4 to 7 wt% UO2 for an oxygen fugacity below 10-14 atm at 1250°C-1400°C. Uranium oxidation states have been investigated by X-ray absorption spectroscopy (XANES). It has been pointed out that UIV is the main form in the glass for such imposed oxygen fugacities. The second step of this work is to identify the glass-metal interaction mechanisms in order to determine the localization of uranium and its surrogates (Nd, Hf) in the glass-metal system. Mechanisms are mostly ruled by the presence of metallic aluminum and are similar for uranium, neodymium and hafnium. Glass-metal interaction kinetics demonstrate that uranium and its surrogates can temporarily be reduced into the metallic form for particular conditions. A re-oxidation occurs with time which is in good agreement with thermodynamics. Regarding uranium, the re-oxidation process must be corroborated. Finally, the formation and dissolution processes of the different crystalline phases observed during these glass-metal interactions have been studied using a thermodynamic approach based on phase diagrams
Haraux, Pauline. "Nouveaux systèmes intermétalliques 3d-4f à valence intermédiaire." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0033.
Full textThe main part of this work completes and clarifies previous studies on the YbMn6Ge6-xSnx compounds and their Fe derivatives. A second exploratory part focuses on potentially promising new compounds in which an anomalous rare earth is associated with a magnetic 3d sublattice.The YbMn6Ge6-xSnx series shows signatures of quantum criticality at the Yb magnetic instability near x ~ 5.23. The first specific heat measurements performed in this work show the heavy fermion character of the alloys (γ > 100 mJ.K-2.mol-1). These measurements also corroborate the existence of a quantum critical point around x ~ 5.23, given the increase in the Sommerfeld coefficient γ (thus the effective mass) in the corresponding alloys, in agreement with theoretical predictions. In addition, XANES and XMCD measurements under pressure, using a low-gradient transmitter medium (He), show the beginning of a peak in the pressure dependence of the signals, similarly to what is observed in the composition dependence. A thermoelectric study has confirmed the importance of this technique for the study of heavy fermion systems, with thermoelectric response strongly dependent on the state of Yb. The Fe for Mn substitution in YbMn6-yFeyGe0.85Sn5.15 alloys (0.00 ≤ y ≤ 1.00) enhances 3d antiferromagnetism. This yields the reduction of the exchange field generated at the Yb site and induces the collapse of the magnetic character of Yb. This kind of substitution constitutes a new way to cross the Yb magnetic instability.In the last part, we have investigated new compounds involving an anomalous rare earth associated with a magnetic 3d sublattice. The numerous synthesis of YbMn6-yCoyGe6-xSnx and CeMnGe1-xSix compounds allow to specify the stability domains and the structural transitions in these series. However, the quality of the samples needs to be improved. The YbMn6-yCoyGe6-xSnx series might be very promising since it could associate two critical points within the same systems
Jacquamet, Lilian. "Etudes structurales de la protéine Fur (Ferric uptake regulation) d'Escherichia coli par spectroscopie d'absorption des rayons X : XANES et EXAFS." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10044.
Full textEmerson, Erica A. "Analysis of iron oxidation in garnets /." Connect to online version, 2008. http://ada.mtholyoke.edu/setr/websrc/pdfs/www/2008/289.pdf.
Full textGustavsson, Jenny. "Cobalt and Nickel Bioavailability for Biogas Formation." Doctoral thesis, Linköpings universitet, Tema vatten i natur och samhälle, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-73113.
Full textTillsats av spårmetaller kan förbättra rötning av organiskt material till biogas. Typ och mängd av respektive spårmetall som behöver tillsättas för att uppnå stimulerande effekter, varierar mellan processer. Detta är delvis kopplat till specieringen och biotillgängligheten av metallerna. Endast fria metalljoner och vissa metallkomplex antas vara tillgängliga för mikrobiellt upptag. Det är dock i många fall oklart hur metallernas speciering påverkar biotillgängligheten. Syftet med föreliggande studie var därför att undersöka effekten av tillsats av Fe, Co och Ni för biogasproduktion från drank, en restprodukt i produktion av bioetanol från spannmål, samt att undersöka hur dessa metallers speciering påverkar deras biotillgänglighet. Effekten av tillsatserna av Fe, Co och Ni undersöktes på biogasreaktorer i lab-skala. Metallernas speciering bestämdes genom sekventiell extraktion (SE), extraktion av AVS (acid volatile sulfide) och kontinuerligt extraherade metaller (AVS-Me). Svavelformer med betydelse för metallspeciering studerades med S XANES (sulfur X-ray absorption near edge structure). Effekten av olika Co- och Ni-koncentrationer på processens mikroflora undersöktes molekylärbiologiskt med kvantitativ PCR (qPCR) och 454-pyrosekvensering. Resultaten visade att Co och Ni stimulerade och stabiliserade biogasprocessen genom ökad metanproduktion, ökad utrötningsgrad samt låga halter av flyktiga fettsyror i det studerade systemet. 10-20% av totala mängden Co återfanns i löst fas, vilket visar att Co var relativt lättillgängligt för mikroorganismerna. Nickel var däremot enbart bundet till organiskt material/sulfider och AVS och kunde alltså betraktas som otillgängligt. Trots detta hade även tillsatsen av Ni stimulerande effekter på biogasprocessen. Det innebär att mikroorganismerna har förmåga att komma åt Ni bundet i svårlösliga sulfidföreningar och att andra mekanismer än löslighet reglerar tillgängligheten av denna spårmetall. De molekylärbiologiska analyserna visade att framför allt de metanbildande mikroorganismerna påverkades av halten av Co och Ni. De halter, som gav välfungerande processer, dominerades helt av acetiklastiska Methanosarcinales. Vid lägre halter av Co eller Ni, då processerna gick sämre, tillkom vätgasutnyttjande metanogener. Det tyder på ett skift i bildningen av metan från att ha dominerats av acetatklyvning till att vätgasutnyttjarna fått större betydelse och att de förra är mer beroende av Co och Ni.
Vercamer, Vincent. "Propriétés spectroscopiques et structurales du fer dans les verres silicatés." Electronic Thesis or Diss., Paris 6, 2016. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2016PA066077.pdf.
Full textAmong the infinite possibilities of glass compositions, soda-lime silicates represent of 90% of the glass production and are widely used for many industrial applications (e.g. automotive, solar panels, construction). Specific glasses silicate containing 0.5 wt% of Fe2O3 were synthesized with extreme redox. The use of reducing and oxidizing conditions allows to isolate the respective Fe2+ and Fe3+ spectroscopic signatures that are usually mixed due to the heterovalent nature of iron. However, synthesis conditions do not allow to isolate specific iron environment that remains distributed in glasses. Thus, Fe2+- and Fe3+-bearing minerals containing iron in well defined environments were selected. The comprehension of structure-spectroscopy relationships in these crystalline references is a preliminary step to the interpretation of iron spectroscopic signature in glasses. A multi-spectroscopic study was performed on glasses and minerals by combining experi- mental (optical absorption, X-ray absorption at the iron K edge, and electron paramagnetic resonance) and theoretical (multielectronic calculations using ligand field multiplet approach to reproduce the K pre-edge and optical absorption spectra) methods. The study of crystalline references evidenced the influence of local symmetry (Oh, Td, D4h/C4v et D3h/C3v) on iron sites and of p–d hybridization on iron spectroscopic signatures. Concerning the study of reduced silicate glasses, the majority of Fe2+ is present in 5- fold coordination, this speciation can reproduce and explain the iron signature by using a distribution of the crystal field parameters to take into account the amorphous nature of glass. The analysis of oxidized glasses supports the existence of Fe3+ in 5-fold coordination. These species need to be considered, in addition to tetrahedral geometries, for the interpretation of optical spectra. This study shed light on structural and spectroscopic variations of iron due to the substitution of calcium by magnesium or by the absence of alkali in the composition of the glass matrix
Simon, Pardis. "Synthèse de nanoparticules d’oxydes de titane par pyrolyse laser - Etude des propriétés optiques et de la structure électronique." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112240/document.
Full textThe synthesis of titanium oxide nanoparticles by laser pyrolysis is studied in this work. This original gas phase technique is a versatile method which allows us to obtain a one-step synthesis of nanoparticles of controlled size, chemical composition and crystalline structure.In this study, two approaches have been proposed to synthesize titanium oxides nanoparticles with absorption in the visible range. In the first place, the synthesis of nitrogen doped titanium dioxide (TiO2) and second, the synthesis of less oxidized titanium oxides than TiO2.First, the synthesis of titanium dioxide nanoparticles is achieved through the use of titanium tetraisopropoxide as a precursor. The laser pyrolysis allows us to control the obtained TiO2 phase, anatase or rutile. Then, using ammonia as a dopant, we were able to synthesize nitrogen doped TiO2 anatase, with an absorption in the visible.Second, by changing the synthesis parameters, it was possible to synthesize nanoparticles of Magnéli phases, also having absorption in the visible. It was also possible to obtain under atmospheric pressure the TiO2-II phase, a high-pressure phase of TiO2 by oxidation of one of the Magnéli phases.Third, using the reducing effect of ammonia we were able to synthesize titanium oxynitrides, Ti(O,N). A detailed study by X-ray diffraction, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, electron energy loss spectroscopy and a study in temperature, allowed us to characterize the structure of this unusual phase. In addition, the optical properties were very interesting, since the material undergoes a transition metal/semiconductor depending on its oxidation and has a very high absorption in the visible region.Finally, the TiO2 nanoparticles and nitrogen doped TiO2 were used for the development of solid state, dye-sensitized solar cells. Initial results show that the morphology of these nanoparticles is suitable for their use for such devices, with yields close to the world state of the art. Secondly, it shows that the nitrogen doping allows to collect a larger amount of photons, through the area of absorption of these nanoparticles and to generate a higher current density
Belissont, Rémi. "Germanium and related elements in sulphide minerals : crystal chemistry, incorporation and isotope fractionation." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0049/document.
Full textGermanium is a critical metalloid in many high-tech industries, especially for the energy transition and the communication sector. Being distinctly siderophile, lithophile, chalcophile and organophile, Ge can be a particularly useful geochemical tracer. This thesis aims at understanding the Ge geochemistry and the factors controlling its concentration in Ge-bearing minerals and ore deposits. Three contrasted Ge-bearing deposits were studied, the Saint-Salvy Zn vein-type deposit, French Massif Central, the Barrigão Cu vein-type deposit, Iberian pyrite belt, Portugal, and the Kipushi Zn–Cu carbonate-hosted deposit, Central African copper-belt, D.R. Congo. The most important Ge-bearing minerals are sphalerite (up to 2580 ppm Ge), chalcopyrite (up to 5750 ppm Ge), and renierite (5.0–9.1 wt.% Ge). The results show a first order relation between the Ge content and the deposition temperature. Synchrotron-based XANES spectroscopy showed that Ge4+ occur in tetrahedral sites in the studied sulphides. Element correlations suggest that Ge is chiefly incorporated in sphalerite and chalcopyrite through coupled substitutions, e.g., 3Zn2+ ↔ Ge4+ + 2(Cu,Ag)+ and 3Fe3+ ↔ 2Ge4+ + Cu+, respectively, or via the creation of lattice vacancies, e.g., 2Zn2+ ↔ Ge4+ + ?. The positive δ74Ge–Ge content correlation observed in sphalerite from Saint-Salvy could indicate that Ge partition coefficient (KdGe) increases with temperature. Ge isotopes in sulphides yield δ74Ge values spanning from –5.72‰ to +3.67‰. The light δ74Ge compositions of Saint-Salvy and Barrigão ores appear to be related to variations in low to moderate fluid temperatures during Ge uptake in open system (e.g., fluid cooling), while the trend towards heavy δ74Ge compositions observed at Kipushi likely translates a Rayleigh fractionation effect during ore formation in closed system, associated with significant fluid modification
Jourdain, Noémie. "Etude des propriétés du cuivre sous conditions extrêmes et hors de l'équilibre thermique." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0175/document.
Full textUltrashort laser sources development enables nowadays the possibility for matter to reachboth extreme pressure and temperature (~10 000 K) conditions, or what we call "WarmDense Matter ". Working with femtosecond lasers leads to out-of-equilibrium phenomenaduring which a large amount of energy is deposited in the electrons while the lattice remainscold. We used XANES spectroscopy to follow both the ultrafast evolution of the electronicstructure and the local atomic order after the irradiation of such a laser. Moreover,we can nowadays employ Quantum Molecular Dynamics to simulate Warm Dense Matter.We computed XANES spectra for thermal out-of-equilibrium situations and inthermodynamic configurations similar to the experimental ones. The confrontation of experimental data and these calculations brings a deep understanding of the phenomena involvedand their evolutions. The present study deals with the X-ray absorption near copper L3 andL2 edges (respectively 932 and 952 eV). Calculations show a pre-edge structure in the spectra,the evolution of which gives the electronic temperature dynamics. These simulationsalso suggest that the loss of the crystalline order should give rise to the disappearance ofthe post-edge structures. Several experiments have been realized using Eclipse laser and atable-top station dedicated to time-resolved XANES measurements at CELIA laboratory.At frst, some XANES spectra have been acquired using an X-ray source produced by theirradiation of a CsI solid target. This source duration of ~2 10 ps rms { approximately thethermal equilibration timescale for copper { restrained our temporal resolution. We thenused a xenon clusters gas jet to produce an X-ray source of comparable emissivity but asignificantly shorter duration. Numerous out-of-equilibrium XANES spectrahave been acquired and for diferent excitation degrees. The excellent signal-to-noiseratio allows us to follow the evolution of the post-edge structure and deduce the associateddynamics of the loss of crystalline structure. Finally, we performed the same experimentwith an X-ray source coming from the betatron radiation at LOA laboratory. With thissource, a temporal resolution of ~ 100 fs was achieved and allows us to fully characterizethe instantaneous heating of the electrons by the laser and far-from-equilibrium states
Verger, Louisiane. "Les oxydes de chrome dans les pigments et les décors de porcelaine." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066546/document.
Full textChromium oxides are widely used in the ceramic industry because they are characterized by a large variety of colors. At the French porcelain manufacture of Sèvres, their coloring properties have been explored since the discovery of chromium at the end of the 18th century. The researches initiated by Brongniart lead to a group of 76 pigments for porcelain composed of chromium oxides, regularly synthesized at the laboratory of the manufacture. An exhaustive study was done on these pigments, which enables to propose a classification based on their mineralogical analysis and highlights the role of Cr3+ in the color of the pigments, without Cr6+. The mixture of one or two pigments and an uncolored frit is applied on the porcelain, and fired at high temperature to obtain a glaze, i.e. a partly glassy decorative layer on the top of the porcelain. Pigments composed of chromium are used to obtain green, pink, greenish-blue, brown and black glazes. This thesis focuses on a particular pigment, mainly composed of gahnite doped with chromium ZnAl2O4:Cr3+. This kind of pigment was identified in a collection of artefacts produced by the manufacture between the end of the 19th century and the beginning of the 20th century. This period corresponds to the artistic movement Art Nouveau. The solid solution ZnAl2-xCrxO4 was studied to get the structural environment of Cr, showing the role of the second neighbor Cr in the color variation. During firing of the glaze, a mechanism of gradual dissolution of the initial grains of pigments was determined, resulting of reactions with the uncolored frit. Our work shows the low solubility of Cr in glass and its preferential speciation in crystals, leading to crystalline phase changes or modifications of composition along solid solutions during the thermal treatment at high temperature. These modifications enable to understand the origin of color in porcelain glazes and the mechanism of glaze formation
Ventura, Michele. "Deposizione elettrochimica di esacianoferrato di rame tramite un metodo "a due step"; caratterizzazione e valutazione delle prestazioni." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10073/.
Full textHubert, Fabien. "Nucléation et croissance de nanocylindres d'or : mécanismes de développement de l'anisotropie et suivi in situ résolu en temps." Paris 6, 2009. http://www.theses.fr/2009PA066651.
Full textWittee, Lopes Christian. "Characterization of metallic species on porous materials by in situ XAS." Doctoral thesis, Universitat Politècnica de València, 2018. http://hdl.handle.net/10251/107953.
Full textThe aim of this thesis is to study the clustering and growth of metallic species either confined or supported in porous materials by in situ X-ray absorption spectroscopy. To accomplish this task, palladium and silver species were introduced into porous materials (¿-alumina, activated carbon and zeolites) by wetness impregnation and ion-exchange methods, respectively. Then, the clustering of these metallic species was controlled by activation treatments in different atmospheres (inert, oxidative and reductive) and followed by XAS in a comprehensive way. The principal goal of current work is to demonstrate that both XANES and EXAFS can provide valuable and, at certain point, innovative information during tuning of metallic species (in terms of type and size). Taking advantage of unusual analysis procedures, such as cumulant approach, fitting of imaginary part of Fourier transform and others, it is possible to obtain refined information about the investigated systems. In the introduction section, a compilation of studies in which XAS was used as important technique to characterize metallic species in porous materials is provided. Conscious that people can use such introduction as a basis for more complex studies in the future, the discussion has been tentatively directed toward this goal. The chapter 4 is focused on the study of the influence of palladium precursors and the nature of support on the resultant nanoparticles. The whole activation process, i.e. the transformation precursor --> nanoparticle, was followed in situ by XAS. The analysis pathway was composed by the starting point (as-impregnated), calcination in O2 flow and posterior reduction with H2. The consequence of using distinct metal precursors and supports were discussed in terms of average coordination number obtained from EXAFS data analysis, which was co-supported by laboratory characterization techniques. The chapter 5 is dedicated to the study of silver clustering during and after activation treatments using Ag-containing small-pore zeolites as precursors and nanocontainers. The influence of framework structure and chemical composition of Ag-based materials on formed Ag species at different clustering and metal redispersion conditions (calcination using distinct atmospheres, reduction in H2, redispersion in O2) were studied using either in situ or ex situ characterization methods. After, the catalytic consequences of tuned Ag-containing zeolites in SCO-NH3 are discussed. In this section, the combination of in situ XAS with several laboratory techniques proved to be pivotal to have a full picture of the investigated system. Finally, a list of projects developed in parallel to this thesis is provided at the end of this document.
L'objectiu d'aquesta tesi és estudiar l'agrupació i el creixement d'espècies metàl·liques confinades o suportades en materials porosos mitjançant espectroscòpia d'absorció de raigs X in situ. Per a això, les espècies de pal·ladi i plata s'han introduït en materials porosos (¿-alúmina, carbó activat i zeolites) per mitjà de la impregnació via humida i mètodes d'intercanvi iònic, respectivament. Una vegada preparats els materials, l'agrupament de les espècies metàl·liques s'ha controlat fent ús de tractaments d'activació en diferents atmosferes (inert, oxidant i reductora) s'ha estudiat exhaustivament per XAS. L'objectiu principal del treball és demostrar que tant el XANES com l'EXAFS proporcionen informació rellevant i, en certa manera, innovadora per al control d'espècies metàl·liques (en termes de tipus i grandària d'aquestes espècies). Fent ús de procediments de tractament de dades no molt habituals com l'anàlisi de cumulants, l'ajust de la part imaginària de la transformada de Fourier i altres, és possible obtenir informació detallada sobre els sistemes estudiats. En l'apartat de la introducció, es proporciona una recopilació d'estudis en els quals s'ha utilitzat XAS com a tècnica principal per a caracteritzar les anomenades espècies metàl·liques en materials porosos. Aquesta introducció ha estat redactada per a que puga servir com a punt de partida per a futurs estudis que requereixen la utilització de XAS per a la caracterització de les espècies metàl·liques presents en els catalitzadors. El capítol 4 es centra en l'estudi de la influència dels precursors de pal·ladi i la naturalesa del suport front a les nanopartícules resultants. El procés d'activació, és a dir, la transformació precursor --> nanopartícula, ha sigut estudiat per XAS in situ. L'anàlisi per XAS va comprendre els següents passos: punt de partida (material impregnat), calcinació en flux d'O2 i reducció posterior amb H2. La utilització de diferents precursors i suports metàl·lics ha permès dur a terme una discussió, referent al nombre de coordinació mitjà obtingut a partir de l'anàlisi de dades de la zona EXAFS, que ha estat recolzat per altres tècniques de caracterització. El capítol 5 s'ha dedicat a l'estudi de l'agrupació de plata intercanviada en els catalitzadors durant i després dels tractaments d'activació. S'han utilitzat zeolites de porus xicotet, com la CHA i RHO, intercanviades amb plata. L'estudi de la influència de l'estructura zeolítica i la composició química dels materials enfront dels diferents tractaments d'activació (calcinació utilitzant diferents atmosferes, reducció en presència d'H2, re-dispersió en atmosfera d'O2) es va realitzar fent ús de mètodes de caracterització in situ o ex situ. A continuació, es discuteix la influència d'aquestes espècies metàl·liques formades, utilitzant els diferents mètodes d'activació, per a la reacció d'SCO-NH3. En aquest sentit, s'ha demostrat que la combinació de XAS in situ amb diverses tècniques habituals de laboratori és fonamental per al desenvolupament d'aquest treball. Finalment, es presenta una llista de projectes, en els quals també s'ha treballat paral·lelament, on s'ha utilitzat XAS com a tècnica de caracterització.
Wittee Lopes, C. (2018). Characterization of metallic species on porous materials by in situ XAS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/107953
TESIS
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