Дисертації з теми "Oxydes à haute entropie"
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Osenciat, Nicolas. "Propriétés de transport dans les oxydes à haute entropie." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF005.
The aim of this thesis is to assess the potential of a new material for solid-state electrolyte applications in all-solid-state batteries and/or micro-batteries. This new compound, which exhibits remarkable Li+ and Na+ ionic conductivity, belongs to a new class of oxides, recently discovered by Rost et al. (Nature Communication, 2015). This new family is formed through configuration entropy stabilisation, at high temperature, into a simple single phase, from a complex mixture of binary oxides (in our case NaCl-Rocksalt structure). We have studied the charge compensation mechanisms involved in the synthesis of the (MgCoNiCuZn)1−xLixO series and the influence of their composition on their ionic conductivity properties. We have attempted to densify these compounds at low temperature using the original Cold Sintering Process, without succeeding in obtaining defect-free ceramics. Finally, we have also developed and described the crystallographic structure and the electrochemical behaviour of a new anode material (possibly compatible with these entropy-stabilised oxides), the Li2(Mg,Co,Ni,Cu,Zn)Ti3O8 multicationic lithium titanate
Tonus, Florent. "Étude de la chimie redox d'oxydes Ruddlesden-Popper n=1 par diffraction de neutrons in situ à haute température sous flux de H₂ et O₂." Rennes 1, 2011. http://www.theses.fr/2011REN1S023.
This study is concerned with the synthesis and crystal chemistry of new Ruddlesden-Popper n=1, oxides which are of interest because of their potential as electrode materials in SOFC batteries. The sol-gel synthesis of two new families having the compositions has been undertaken, along with their characterisation by thermogravimetric analysis, magnetometry, and X-ray, neutron and electron diffraction. A novel reaction cell for in situ neutron thermodiffraction studies of a redox behaviour under different gas flows has been designed. The evolution of the structure, particularly the disorder of the oxygen atoms, has been followed in situ and in real time under the working conditions of a SOFC anode under hydrogen by neutron thermodiffraction (instrument D20, ILL / Grenoble) as a function of the value of δ. Sequential Rietveld refinements showed a deintercalation of oxygen from the equatorial site controlled by the reduction of the cation M. These materials are promising at the technological level given their excellent chemical and structural stability under operating conditions, which is likely attributable to the presence of Cr³⁺ ions. This in situ monitoring was also applied to the similar compositions synthezised at the University of Birmingham, U. K. Data anlysis by a combination of Rietveld refinements and maximum entropy clarified the details of the average nuclear density of the oxygens for certain values of δ and T, and suggested possible anisotropic diffusion pathways of the oxide ions in these compositions
Broux, Thibault. "Caractérisations structurales in situ avancées d'oxydes dérivées de la pérovskite pour des applications électrochimiques à haute température." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S125/document.
This thesis is focused on oxides related to perovskite such as K2NiF4 structure-type, double perovskite and brownmillerite with mixed conduction properties. This ability to conduct both oxygen ions and electrons is relevant for electrochemical devices operating at high temperature, particularly as an electrode for solid oxide fuel cell. Specifically, this thesis deals with the synthesis and advanced crystal structure characterization of the reactivity of these materials mainly through large scale facilities by means of neutron powder diffraction (NPD) and X-ray synchrotron. Preliminary work in these studies involves inorganic synthesis by solid-state or by sol-gel route, thermogravimetric analysis and the iodometric titration. Original reactivity cells have been developed at the ISCR to study redox behavior under different gas flow and as a function of temperature for both neutron diffraction and X-ray synchrotron experiment. In situ study by NPD of La2-xSrxMnO4 ± δ compounds where x = 2.0 and x = 0.8 which derived from the compound cathode reference La1-xSrxMnO3 allowed to follow the structural evolution as a function of δ in reducing conditions for x = 2.0 and oxidizing conditions for x = 0.8. The synchrotron study of Pr2NiO4.22 helped to highlight the monoclinic symmetry at room temperature while previous studies announced an orthorhombic symmetry. Besides, structural changes including the transition to the HTT phase are accompanied by an incommensurable modulation that persists at least up to 900 °C. The study of double perovskites NdBaCo2-xMnxO5+δ where 0 ≤ x ≤ 2 showed that these materials exhibit a promising electrical conductivities for SOFC applications as cathode. In addition, the comparison of the molecular dynamics and NDP combined with MEM for x = 0 compound has elucidated the oxygen diffusion mechanism in these compounds. The study by NPD in reducing condition of LaSrFeCoO6 to the brownmillerite LaSrFeCoO5 has showed that the reduced structure persists at high temperatures and allowed to follow the evolution in the ordering of the magnetic moments while cooling LaSrFeCoO5
Sow, Mourtada Aly. "Alliages à Haute Entropie (AHE) pour revêtements hautes performances." Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR026.
This thesis aims to develop high performance coatings from high entropy alloys powders (HEA) and to characterize them. This work is divided in two parts. The first part consists in the synthesis of HEA powders for a family of alloy elements Al, Cr, Fe, Mn and Mo by mechanical alloying.These powders were characterized by XRD, SEM and Mössbauer spectrometry. These powders have a CC1 and CC2 type crystal structure. The heat treatment of the powders (500, 650, 800 and 950 °C) allowed to obtain a structural stability at 650 °C/ 1h, at 800 °C/ 1h and 950°C/ 1h and 4h, a structural evolution of the powders was noticed. The CC1 phase disappears in favor of the CC2 phase and the M23C6 et M6C type carbides. At the result of these characterizations, the chemical composition 19Al-22Cr-34Fe-19Mn-6Mo powder was preserved and produced in suffering quantities by mechanical synthesis (powder A) and by mixing (powder B).In the second part of this work, thick and thin HEA coatings were developed by laser fusion and magnetron sputtering respectively from A and B powders. The thick laser-melted coatings were deposited on steel substrate. The structure and microstructure of the deposits were carefully characterized by XRD, SEM, EDS, EBSD and TEM. The results of these characterizations revealed that the thick deposits are chemically heterogeneous. Moreover, these coatings showed different structures and microstructures of solidification depending on the deposition conditions and the powders (A or B) pre-deposited to realize these coatings.The HEA thin film were deposited on silicon wafer and steel substrate. The deposition conditions of the thin films were optimized and the chemical composition was controlled. The heat treatments of the thin films revealed good structural and microstructural stability up to 800 °C/ 72h. Corrosion resistance, mechanical properties and tribological performances were evaluated
Sortais-Soulard, Céline. "Équilibres oxydo-réducteurs dans les dichalcogénures de platine et de palladium : influence de la pression sur la redistribution du nuage électronique." Phd thesis, Université de Nantes, 2004. http://tel.archives-ouvertes.fr/tel-00007453.
Barriquand, François. "Rmn dans les oxydes supraconducteurs a haute temperature critique." Paris 11, 1991. http://www.theses.fr/1991PA112345.
Lannelongue, Pierre. "Oxydes polycationiques pour supercondensateurs à haute densité d'énergie volumique." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS146/document.
Supercapacitors are attractive electrochemical energy storage devices for high power applications. However, volumetric energy density is the main limitation for their integration in such applications as terrestrial transport systems. The use of high density pseudocapacitive oxides as electrode material could lead to a volumetric energy density improvement. With this aim, materials from Ba0,5Sr0,5CoxFe1-xO3-δ family, so called BSCFs, have been studied. Several compositions have been prepared and evaluated as positive electrode materials in aqueous neutral electrolyte. Volumetric capacitances have shown to be greater than those of activated carbons, already used in marketed supercapacitors. They have also shown to depend on cobalt and iron ratio, charge rate, electrolyte composition... The study of the charge storage mechanism in these materials has been investigated thanks to in situ (X-Ray absroption spectroscopy) and operando (X-Ray diffraction) technics performed at SOLEIL (France) and SPring-8 (Japan) synchrotron facilities. Finally, devices coupling BSCF based positive electrode material with activated carbon or FeWO4 based negative electrode materials have demonstrated the added value of such materials to improve the volumetric energy density of supercapacitors
Lilensten, Lola. "Etudes structurale et mécanique d'alliages réfractaires de haute entropie de configuration." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1132.
High entropy alloys (HEA) are a new promising type of materials. Breaking with the traditional alloying concepts, solid solution(s) based on 5 elements in equiatomic concentration with simple crystal structures are obtained. In this study, the equiatomic composition TiZrNbHfTa is investigated, in order to provide an in-depth characterization of a “reference” body centered cubic refractory HEA.First, the microstructure and structure of the alloy are studied. Thermomechanical treatments procedures are established to access recrystallized microstructures. The local environment is studied by EXAFS in sub-components of the TiZrNbHfTa system. The double approach used, based on EXAFS fit and reverse Monte-Carlo coupled with evolutionary algorithm allowed to quantify both the mixing of the elements at the atomic scale and the lattice distortion. For all the investigated compositions, good mixing is achieved, and the distance distribution of first nearest neighbors becomes less precise with increasing atomic size mismatch.Then, the impact of such concentrated multi-element solid solution on the mechanical properties and the deformation mechanism of the material is investigated by specific tests. The activation volumes and the flow stress partition are extracted. The mechanical results are coupled with a TEM study. This part evidences that the alloy displays an impressive yield strength. However, the high lattice friction controlling the dislocation glide does not differ from classical bcc structures, leading to a rather low work hardening. A new design approach aiming at increasing the work-hardening in such materials is finally proposed, and a proof of concept is given
Ben, Elbahri Marwa. "Dévelοppement de matériaux cοmpοsites de haute cοnstante diélectrique". Caen, 2016. http://www.theses.fr/2016CAEN2022.
This thesis presents an in-depth study of the dielectric properties and the interface effects of a dielectric material based on amorphous laminates of Al2O3 and TiO2 with sub-nanometer individual layer thicknesses, deposited by Pulsed Laser Deposition. A high dielectric constant compared to nanometric laminates due to the Maxwell-Wagner effect is obtained. This effect is well-known in inhomogeneous dielectrics related to the interfaces between insulating and semiconducting regions. Thin films of Al2O3 and TiO2 are studied separately in order to determine the optimal conditions for the growth of the subnanometric laminates by producing and combining the best physical qualities of both constituent layers. An optimization of the capacitor structure is performed varying the bottom electrode and the total thickness of the laminate. Laminates with a better insulating character of the Al2O3 layers achieve higher dielectric constants. The characteristics of the charge carriers governing the dielectric relaxation and their activation energy are discussed by analyzing the dielectric properties (the dielectric constant ε', the dissipation factor tan δ, the electric modulus M" and the conductivity σac) as a function of temperature and frequency
BARNOLE, VALERIE. "Structure electronique locale dans les oxydes supraconducteurs a haute temperature critique." Paris 6, 1990. http://www.theses.fr/1990PA066029.
Khammari, Mohamed. "Etude de propriétés thermooptiques de divers oxydes réfractaires à haute température." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37598693g.
Rozier, Yoann. "Caractérisation d'oxydes cristallins à haute permittivité (LaAIO3, SrTiO3) en vue d'une intégration en microélectronique." Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0029/these.pdf.
Continuous scaling of micro-electronics components will require integrating, in short-term, alternative insulating films to SiO2. The replacement of traditional silica by a dielectric with a higher permittivity (high-K) allows pushing back the fundamental limits of integration and reduces leakage currents vertically flowing through transistors. Short to middle-term industrial choices are based onto integration of amorphous material like silicon oxynitride or hafnium silicates based oxides. Considering some key guidelines like thermodynamic stability or electrical properties these choices clearly lead to some limitations. Particularly, the research of ultimate electric equivalent thicknesses is considered as one of the most important crucial point. For future CMOS technology nodes, ternary materials systems, through an epitaxial approach, currently offer the most promise toward the ultimate goal of integrating a gate dielectric. Therefore, this thesis work is based on the development of electrical and physical properties of two insulators: LaAlO3 (ɛLaAlO3=25) deposited with Molecular Beam Epitaxy (MBE) approach and SrTiO3 (ɛSrTiO3=340) deposited with liquid injection MetalOrganic Chemical Vapor Deposition (MOCVD) equipment. In the case of LaAlO3, amorphous films lead to the best electrical characteristics. We have obtained a bulk permittivity of ɛLaAlO3=12. 5 with only 0. 5nm of interfacial thickness. This result is comparable to the state of the art. Various strategies of deposition and ex-situ treatments were tested in order to minimize the impact of the charges present in the first nanometers. As for SrTiO3, we have shown that electrical properties of polycrystalline stacks strongly depend on the thickness, on crystallinity and on composition. The presence of two interfacial stacks, 2-2. 5 nm of silica and 2. 5-4. 0 nm of a strontium silicate, strongly penalizes the global permittivity (ɛfilm=45-50 for 80 nm). Finally, we highlighted through Atomic Force Microscopy (AFM) acquisitions heterogeneous conduction on the surface of polycrystalline films. Leakage is dominated by conduction through grains in SrTiO3 deposited films. Ex-situ treatments in oxidizing atmosphere could lower leakage current in the crystalline part
Pereira-Ramos, Jean-Pierre. "Contribution à l'étude électroanalytique de matériaux d'intercalation de type "oxyde" en milieu diméthylsulfone fondue." Université Paris-Est Créteil Val de Marne (UPEC), 1988. http://www.theses.fr/1988PA120033.
Delhaye, Gabriel. "Oxydes cristallins à haute permittivité diélectrique épitaxiés sur silicium : SrO et SrTiO3." Ecully, Ecole centrale de Lyon, 2006. http://bibli.ec-lyon.fr/exl-doc/gdelhaye.pdf.
The study of the epitaxial crystalline oxide growth on silicon is of great interest for the future CMOS technologies or monolithic integration on silicon : the miniaturization of the micro-electronic devices leads to the replacement of the SiO2 gate oxide by crystalline oxides with high dielectric permittivity. The control of the crystalline oxide growth must also allow integration of functional oxide on silicon with ferroelectric, magnetic or optical properties, thus opening the way with the development of new devices. The studies undertaken in this work are related to the growth of crystalline oxides on silicon at low temperatures with molecular beam epitaxy and the development of strategies of suitable interface engineering. The deposited materials were on the one hand the rare earth oxides such as SrO, Ba×Sr1-×O and the other hand, oxides of perovskite type such as SrTiO3, BaTiO3 or LaAIO3. A first step has consisted in defining and optimizing the conditions of homo-epitaxy and hetero-epitaxy of oxide on oxide, for the systems SrO/SrTiO3, SrTiO3/SrTiO, BaTi3/SrTiO3 and LaAlO3/SrTiO3. The feasibility to realise crystalline oxide hetero-structures was thus studied from the point of view of functional oxide integration on semiconducteur. In a second step, we achived to control the crystalline oxide epitaxy on silicon, by studying more particularly the systems SrO/Si and SrTiO3/Si : strontium oxide can be grown at ambient temperature with formation of an abrupt interface, without silica to the interface. At a higher temperature of 500°C, depositing some mono-layers of SrO leads on the other hand to the formation of a mono-crystalline silicate of composition close to Sr2SiO4. However, the interface strontium silicate/Si has a poor thermodynamic stability, due to interfacial reactions during annealings at high temperature. We also developed a strategy of epitaxial growth of SrTiO3 on silicon based on the succession of various steps : an engineering of interface with formation of a strontium silicide, a recrystallization at low temperature of some mono-layers of SrTiO3 and the subsequent epitaxy at higher temperature. Thus, we observe the formation of a layer of good crystalline quality, without being able to avoid the formation of an amorphous silicate interfacial layer of ~1nm. The use of buffer layers of SrO or SrTiO3 on silicon allows the subsquent epitaxy of the LaALlO3 perovskite, of which the direct epitaxy on silicon could not have been obtained. The whole of the results so obtained makes it possible to consider the development of process of integration of new functionalities on silicon and the realization of new devices for micro-electronics
Bourges, Philippe. "DYNAMIQUE DE SPINS DANS LES OXYDES DE CUIVRE SUPRACONDUCTEURS A HAUTE TEMPÉRATURE CRITIQUE." Habilitation à diriger des recherches, Université Paris Sud - Paris XI, 2003. http://tel.archives-ouvertes.fr/tel-00003467.
Oussena, Mohand. "Champs et densités de courants critiques dans les oxydes supraconducteurs à haute Tc." Paris 11, 1989. http://www.theses.fr/1989PA112108.
A field and temperature studies of the high Tc superconductor oxides (La1,85Sr0,15Cu04, YBa2Cu307 and Bi2Sr2CaCu2O8) has revealed several particular behaviours. In sintered samples, the intergranular critical current density varies from 10 to 103 A/cm2 at T = 4. 2 K, whereas the intragranular critical current density exceeds 106 A/cm2 at T = 4. 2 K and is the same in single crystals (magnetic measurements). Both are controlled by the material's structure yielding two irreversible regimes: one at low magnetic field and the other one at high magnetic field (H>Hc1). The low field irreversibility is strongly reduced in powdered samples and disappears in single crystals: it is controlled by intergranular junctions. The intragranular critical current density displays an exponential decay with temperature whereas the intergranular critical current density exhibits power Laws both with magnetic field H and with temperature T. The latter is comparable to what is deduced from transport measurements. A comparison with this method allows us to show that the critical current density determined by transport measurements is not an intrinsic property of the high Tc superconductor oxides but reflects the junction's current. Study of the angular dependence of the magnetization of single crystals revealed a strong and anomalous behaviour of the hysteresis cycle for H oriented out of the symmetry directions. The anisotropy is of order 30. M vs H curves are extremely sensitive to the exact direction of H, particularly close to the (a,b) plane. The isotropical critical state model fails to describe the magnetic cycle except when the applied field is parallel to the c-direction
LE, NOC LOIC. "Etude des oxydes supraconducteurs a haute temperature critique bisrcacuo par resonance magnetique nucleaire." Paris 6, 1993. http://www.theses.fr/1993PA066150.
Deleglise, Florence. "Fibres céramiques oxydes biphasées : relations entre comportement mécanique à haute température et microstructure." ENSMP, 2000. http://www.theses.fr/2000ENMP0980.
Younes, Charles. "Contribution à l'étude thermodynamique par spectrométrie de masse à haute température des oxydes." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37601983m.
Capute, Batalha Weverson. "Alliages amorphes à pseudo-haute entropie à base de fer : structure/microstructure, corrosion et propriétés mécaniques." Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALI098.
The quest for alternative materials to replace conventional stainless steel for marine applications has gained prominence recently. Among the emerging candidates, low-chromium Fe-based amorphous alloys have shown great promise, albeit needing a deeper understanding of their behavior. This research investigates the effect of devitrification on the corrosion and mechanical properties of two novel FeCrMoNbB and FeCrMoNiB pseudo high entropy amorphous compositions and their behavior when applied as coatings, shedding light on the critical role of passive film characterization.In the first stage, ribbons prepared through melt-spinning were subjected to annealing in an Ar protective atmosphere for simulation of crystallization. Corrosion tests were performed in a three-electrode cell, revealing the sensitivity of corrosion properties to the devitrification process, especially for the FeCrMoNbB composition in the first stages of crystallization. Both compositions presented outstanding corrosion properties in the amorphous state with a passivation plateau extending over 800mV relative to OCP. Electrochemical Spectroscopy Impedance (EIS) data was validated by Measurement Model software, and the Power Law model was applied to interpret the diagrams, allowing the calculation of resistivity at the metal/film interface (ρ0) for both alloys. The value of ρ0 was higher for the Nb-containing alloy, on the order of 1013 Ωcm2. X-ray photoelectron spectroscopy was applied for passive film study, and the compact passive layer composed of Cr, Nb, and Mo was linked to the superior corrosion resistance of the Nb-containing alloy compared to the Ni-containing one.Erosion-corrosion behavior was assessed using a disk of both compositions generated from commercial precursors' spray-forming process. Despite surface defects such as inherent pores and fissures resulting from the coating application process, both coatings exhibited hardness greater than three times that of conventionally used stainless steels. The erosion-corrosion behavior of the samples appeared to be significantly influenced by both porosity and particle oxidation. From an electrochemical perspective, as determined through Open Circuit Potential (OCP) measurements, it was impossible to differentiate between the two analyzed samples.In a subsequent step, coatings were applied using the DC magnetron sputtering technique, creating two compact, amorphous thin films with high hardness. The results from the coatings were comparable with those obtained from the ribbon samples. The passive film analysis via EIS and X-ray Photoelectron Spectroscopy XPS enabled the characterization of the passive films described by the Young model for the Nb-containing alloy and the Power Law model for the alloy containing Ni. Pitting was absent in the case of the Nb-containing coating, which exhibited markedly superior properties compared to the substrate.The comprehensive investigation of these Fe-based alloys offers valuable insights into their potential for marine and industrial applications, addressing corrosion and erosion-corrosion challenges. These materials have demonstrated outstanding performance and corrosion resistance, positioning them as viable alternatives to conventional stainless steels in harsh operating conditions
Schnuriger, Benoît. "Oxydes à valence mixte : supraconducteurs à haute température critique Bi2-yTeySr2-zNazCaCu2O8+d et oxydes du système Sr-V-O : synthèse et caractérisation." Toulouse 3, 1992. http://www.theses.fr/1992TOU30089.
Poncelet, Olivier. "Précurseurs moléculaires d'oxydes de haute pureté : alcoxydes métallosiloxanes et bêta-dicétonate de lanthanides (yttrium, cérium, néodyme) d'aluminium et de zirconium : synthèse, caractérisation, valorisation." Nice, 1988. http://www.theses.fr/1988NICE4217.
TADUY, THANH. "Diffusion et electromigration dans des oxydes cubiques a haute temperature. Application aux oxydes de cobalt co#1##o et de manganese mn#1##o." Paris 11, 1992. http://www.theses.fr/1992PA112214.
Salmon, legagneur Hubert. "Caractérisation de l’endommagement à haute température d’aciers ferritiques renforcés par dispersion de nano-oxydes (ODS)." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM034/document.
The development of the fourth generation of nuclear power plants relies on the improvement of cladding materials, in order to achieve resistance to high temperature, stress and irradiation dose levels. Strengthening of ferritic steels through nano-oxide dispersion allows obtaining good mechanical strength at high temperature and good resistance to irradiation induced swelling. Nonetheless, studies available from open literature evidenced an unusual creep behavior of these materials: high anisotropy in time to rupture and flow behavior, low ductility and quasi-inexistent tertiary creep stage. These phenomena, and their still unclear origin are addressed in this study.Three 14Cr ODS steels rods have been studied. Their mechanical behavior is similar to those of other ODS steels from open literature. During creep tests, the specimens fractured by through crack nucleation and propagation from the lateral surfaces, followed by ductile tearing once the critical stress intensity factor was reached at the crack tip. Tensile and creep properties did not depend on the chemical environment of specimens. Crack propagation tests performed at 650°C showed a low value of the stress intensity factor necessary to start crack propagation. The cracks followed an intergranular path through the smaller-grained regions, which partly explains the anisotropy of high temperature strength.Notched specimens have been used to study the impact of the main loading parameters (deformation rate, temperature, stress triaxiality) on macroscopic crack initiation and stable propagation, from the central part of the specimens.These tests allowed revealing cavities created during high temperature loading, but unexposed to the external environment. These cavities showed a high chemical reactivity of the free surfaces in this material. The performed tests also evidenced different types of grain boundaries, which presented different damage development behaviors, probably due to differences in local chemistry. The nature of these grains boundaries and their origin are still to be explained
Stern, Anthony. "Comportements métallurgique et mécanique des matériaux de gainage du combustible REP oxydes à haute température." Paris, ENMP, 2007. http://www.theses.fr/2007ENMP1506.
Zirconium alloys are used as cladding materials in PWR. As they are submitted to very extreme conditions, it is necessary to check their behaviour and especially to make sure they meet the safety criteria. They are therefore studied under typical in service-loadings but also under accidental loadings. In one of these accidental scenarios, the cladding temperature may increase above 800°C, in a steam environment, and decrease before a final quench of the cladding. During this temperature transient, the cladding is heavily oxidised, and the metallurgical changes leads to a decrease of the post quench mechanical properties. It is then necessary to correlate this drop in residual ductility to the metallurgical evolutions. This is the problem we want to address in this study. As oxygen goes massively into the metallic part - a zirconia layer grows at the same time – during the high temperature oxidation, the claddings tubes microstructure shows three different phases with various mechanical properties. In order to reproduce the behaviour of this multi-layered material, the first part of this study consisted in creating samples with different oxygen contents, similar to those observed in the different phases of the real cladding. The study was especially focused on the phase transformation upon cooling. A mechanism was proposed to describe this phase transformation. Then, these materials were mechanically tested at various temperatures and for various mean oxygen contents. It was thus possible to start some preliminary finite element calculations to describe the cladding behaviour under the standard technological ring compression test
Gillet, Jean-Alain. "Etude par résonance magnétique nucléaire des oxydes supraconducteurs à haute température critique YBa2Cu3O(6+x)." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10113.
Rey, Marie-Jeanne. "Supraconducteurs à haute température critique : étude de nouveaux oxydes de structure dérivée de la pérovskite." Grenoble INPG, 1990. http://www.theses.fr/1990INPG0105.
Mathieu, François. "Etude des transformations sous haute pression des oxydes de fer submicroniques à structure spinelle : analyse structurale des mécanismes réactionnels." Toulouse 3, 1990. http://www.theses.fr/1990TOU30043.
Toulemonde, Pierre. "Nouveaux oxydes supraconducteurs : la famille des cuprates à double couche de mercure." Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10190.
Mroz, Michal. "Design et optimisation structurale d'un alliage à forte entropie (HEA) de la famille CoCrFeMnNi a haute résistance mécanique." Thesis, Lyon, 2018. https://tel.archives-ouvertes.fr/tel-02869758.
High entropy alloys (HEAs) are a new class of materials obtained with a novel approach. They are made of at least 5 elements in similar proportions, which results in increased configurational entropy of the system and in some cases in higher stability of single solid solutions.In this work, a novel HEA based on equiatomic CoCrFeMnNi was optimized, characterized and patented. This alloy, referred to as A3S (austenitic super stainless steel), consists of 5 elements in non-equiatomic proportions (Co20Cr15Fe26Mn17Ni22). This composition was optimized with CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) in Thermo-Calc software. The material possesses stable face-cubic centered solid solution structure and, unlike the equiatomic one, remains stable after annealing at 500oC up to 300 days. The facility of forming a nanostructure after hot forging is remarkable, and results in high resistance as well as ductility compared to stainless steels. These properties are improved at cryogenic temperatures where an additional mechanism of deformation by twinning is being activated. This compilation of properties is very promising for industry where new materials are required.A comparative study between the novel A3S and the equiatomic reference material has been conducted. First, the procedure of the alloy optimization by thermodynamic calculations has been presented. Then, microstructures and mechanical properties in different conditions (various annealing temperatures and times as well as types of deformation) have been examined. Finally, the last part reviews the mechanisms of recovery and recrystallization which differ significantly from classical materials
Retoux, Richard. "Etude cristallochimique et caracterisation de nouveaux oxydes supraconducteurs a haute temperature critique, a base de bismuth." Caen, 1990. http://www.theses.fr/1990CAEN2047.
Martin, Christine. "Etude cristallochimique et caracterisation de nouveaux oxydes supraconducteurs a haute temperature critique, a base de thallium." Caen, 1990. http://www.theses.fr/1990CAEN2041.
Burin, Jean-Philippe. "Effets de la granularite sur les proprietes de transport des oxydes supraconducteurs a haute temperature critique." Rennes, INSA, 1991. http://www.theses.fr/1991ISAR0004.
Courty, Colette. "Détermination par diffraction X des contraintes résiduelles dans les oxydes formés sur les métaux à haute température : cas des sytèmes Ni/NiO et Co/Co3O4." Compiègne, 1988. http://www.theses.fr/1988COMPD115.
JAKUBOWICZ, NATHALIE. "Modulations simples ou doubles des oxydes supraconducteurs a haute tc bi 2 xpb xsr 2cacu 2o 8 + et des oxydes apparentes bi 2 xpb xsr 2coo 6." Caen, 1999. http://www.theses.fr/1999CAEN2040.
Artizzu, Paola. "Combustion catalytique du méthane à haute température : application dans les turbines à gaz." Lyon 1, 1996. http://www.theses.fr/1996LYO10261.
Balédent, Victor. "Paramètre d'ordre magnétique dans la phase de pseudogap des oxydes de cuivre supraconducteurs à haute température critique." Phd thesis, Université Paris Sud - Paris XI, 2010. http://tel.archives-ouvertes.fr/tel-00683440.
Huve, Marielle. "Etude cristallochimique et caracterisation de nouveaux oxydes supraconducteurs a haute temperature critique a base de tha;llium." Caen, 1993. http://www.theses.fr/1993CAEN2034.
Adamczyk, Evan. "Nouveaux matériaux d'électrodes à haute densité d'énergie pour batteries Na-ion." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC286/document.
N the coming years, the production of Energy will have to go through the use of more environmentally friendly means such as renewable energies. However, their intermittent nature requires the establishment of a large-scale storage. Among the various technologies available, Na-ion batteries appear as a solution of choice thanks to unlimited sodium resources. In this context, we are interested in the synthesis and characterization of new positive electrode materials for Na-ion batteries. The transition metal oxides, and more particularly the Na-Mn-O system, have drawn our attention to the benefits of manganese in terms of non-toxicity, low cost and abundance. The phase Na4Mn2O5 (with oxygen vacancies) and Na2Mn3O7 (with manganese vacancies) show interesting specific capacities by the action of various redox phenomena. Na2Mn3O7 may be reduced, to form the phase Na4Mn3O7 and oxidized, by the action of the oxygen redox activity, giving capacities of 160 and 120 mAh/g, respectively. In order to extend the study to a transition metal that can be oxidized to a +V valence state, Na2V3O7 has also been studied and one Na+ can be reversibly extracted from it
Bion, Nicolas. "Réduction sélective des oxydes d'azote en excès d'oxygène sur oxydes métalliques à moyenne et haute température : Etude par couplage : spectroscopie IRTF-spectroscopie de masse et proposition de mécanisme." Caen, 2001. http://www.theses.fr/2001CAEN2045.
Labaiz, Mohamed. "Étude de l'oxydation et du frottement à haute température d'aciers au carbone et inoxydable : comparaison avec quelques matériaux céramiques." Compiègne, 1993. http://www.theses.fr/1993COMPD606.
Pawula, Florent. "Particularités des oxydes de ruthénium sondées par l'effet Seebeck." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC225/document.
This thesis deals with the synthesis, the structural study and the magnetic properties and electronic transport studies of different ruthenium oxide families, presenting various magnetic and electronic behaviors, with rutile, R-type hexaferrite and hollandite structures. The goal of this thesis was the study of the ruthenium oxide peculiarities probed by the Seebeck effect in the following materials: RuO2 rutile (edge-shared RuO6 chain interconnected by their vertices) with Boltzmann type transport dominated by electron-phonon interactions, BaCo2Ru4O11 et BaMn2Ru4O11 R-type hexaferrites (edge-shared RuO6 octahedra, forming kagome planes, and face-shared RuO6 octahedra) soft ferromagnetic bad metals, and two new hollandites Sr1.5Ru6.1Cr1.9O16 et Ba1.5Ru6.1Cr1.9O16 (double chains of edge-shared RuO6 octahedra, interconnected by their vertices) with localized transport and cluster-glass behavior. The synthesis of both new hollandites by solid state reaction allowed us to show the existence of negative magnetoresistance in this compound family. This thesis shows that the behavior of the Seebeck coefficient of ruthenium oxides with structures mainly consisting of edge-shared RuO6 octahedra presents two different behaviors. At low T, S strongly depends on the crystallographic structure and on the associated electronic structure. On the other hand, in the high T limit, S tends a common value independently of the structure as reported here for the R-type hexaferrites and the hollandites and as previously observed in the ferromagnetic metal SrRuO3 perovskite (apex-shared RuO6 octahedra) and in the metallic with Pauli-type magnetism quadruple perovskite LaCu3Ru4O12 (apex-shared RuO6 octahedra). In these R-type hexaferrites BaCo2Ru4O11 and BaMn2Ru4O11 and these two new hollandites Sr1.5Ru6.1Cr1.9O16 and Ba1.5Ru6.1Cr1.9O16, the high temperature Seebeck coefficient reaches a value dominated by the Ru spin entropy term
Debord, Régis. "Développement d'une cellule haute pression haute température dans la presse Paris-Edimbourg pour la mesure de propriétés élastiques et de densité : Application sur les oxydes de fer." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2001. http://tel.archives-ouvertes.fr/tel-00189118.
Debord, Régis. "Développement d'une cellule haute pression haute température dans la presse Paris-Edimbourg pour la mesure de propriétés élastiques et de densité : application sur les oxydes de fer." Paris 6, 2004. http://www.theses.fr/2004PA066448.
Aicart, Jérôme. "Modélisation et validation expérimentale d'un co-électrolyseur de la vapeur d'eau et du dioxyde de carbone à haute température." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI095/document.
This work investigates the high temperature co-electrolysis of H2O and CO2 in Solid OxideCells. A detailed model was developed, encompassing electrochemical, chemical, thermal andmass transfer phenomena, and introducing a macroscopic representation of the co-electrolysismechanism. This model allows predicting the performances and outlet compositions in singlecell and stack environments. An experimental validation protocol was implemented on twotypes of commercial Cathode Supported Cells, ranging from polarization curves, obtained insingle and co-electrolysis modes, to micro gas analyses. These tests aimed both at determiningthe different exchange current densities, representative of the kinetics of electrochemicalreactions, and validating the simulated cell global behavior and mechanism proposed.Comprehensive analysis of the simulations led to the identification of limiting processes andpaths for optimization, as well as to the establishment of co-electrolysis operating maps
Jaffré, Yoann-Nicolas. "Optimisation de réacteurs à plasmas non-thermiques pour le traitement des oxydes d'azote." Phd thesis, Ecole Centrale de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00567149.
Gressent, Alicia. "Caractérisation et modélisation sous-maille des panaches d'éclairs : implication sur le bilan de l'ozone et les espèces azotées de la haute troposphère." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30150/document.
Lightning emissions are one of the most important sources of nitrogen oxides (NOx = NO+NO2 ) in the upper troposphere. They imply high N Ox concentrations where their lifetime is longer in this part of the atmosphere and can be associated to large plumes transported over long distance. Furthermore, the decisive role of lightning emissions in the upper tropospheric chemistry and especially on the ozone production and the oxidizing capacity of the atmosphere is well known. My PhD is dedicated to the characterization of the lightning-NOx related plumes and the associated sub-grid modeling in order to determine their impact on the ozone and nitrogen oxyde burden in the upper troposphere. The analysis of the MOZAIC measurements in the northern-mid-latitudes coupled with FLEXPART Lagrangian model calculations, ground and space-based observations of lightning flashes and clouds is made. This study highlights the existence of large scale plumes of NOy from lightning emissions and describes their frequency, their chemical composition and evolution during the long-range transport. A negative (positive) gradient of NOy (O3) is found within the large scale plumes of about -0.4(+18) ppbv difference, during spring, and -0.6(+14) ppbv difference, in summer, between North America and Europe. Therefore, for the first time, a plume parameterization for lightning NOx emissions is implemented into CTM. This approach allows the transport of the non-linear chemistry effects occurring within plumes. The implementation of the plume-in-grid parameterization leads to a significant NOx and O3 decrease over the region characterized by a strong lightning activity (up to -25 % and -8 %, respectively, over Central Africa, in July) and a relative increase downwind of lightning NOx emissions (up to +10 % and +1 %, respectively, over Atlantic ocean, in July). This work allows to reduce the uncertainties on the representation of the non-linear processes at a smaller scale than the model grid in order to provide better estimates of (i) the nitrogen oxide distribution related to lightning and (ii) the associated ozone production at the large scale
Silva, Mosquera Maribel. "Elaboration par OMCVD et caractérisation de films de revêtements d'alumine avec ou sans élément réactif (terres rares ou molybdène) : application à l'anticorrosion des aciers à haute temperature." Dijon, 1997. http://www.theses.fr/1997DIJOS032.
Journeau, Christophe. "L'étalement du Corium : Hydrodynamique, Rhéologie et Solidification d'un Bain d'Oxydes à Haute Température." Phd thesis, Université d'Orléans, 2006. http://tel.archives-ouvertes.fr/tel-00343671.
Poletti, Antoine. "Contribution à l'étude du frittage des mélanges UO2+x - CeO2 traités sous atmosphère oxydante : Comparaison avec le système UO2+x - PuO2." Limoges, 2001. http://www.theses.fr/2001LIMO0023.
This study is a physical and chemical approach of reactive sintering,in a carbon dioxyde environment, of ceramics with the following composition 0,7 UO2+x-0,3CeO2 with x equal to 0,06 - 0,20 or 0,27