Thèses sur le sujet « Oxyde 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.
Texte intégralThe 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.
Texte intégralThis 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.
Texte intégralThis 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.
Texte intégralThis 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.
Texte intégralLilensten, Lola. « Etudes structurale et mécanique d'alliages réfractaires de haute entropie de configuration ». Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1132.
Texte intégralHigh 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
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.
Texte intégralGuillamet, Sébastien. « Réalisation d'un micro-écran OLED haute luminance ». Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAT060.
Texte intégralThis study focuses on the realization of a high brightness OLED micro-écran on silicon. The limited efficiency of White-OLED combined with color filters prevents the use of this technology in “see-through” applications. We propose a novel approach getting benefits from the optical micro-cavity effect in Top-Emitting OLED to generate colors without using color filters. Cavity modulations at a sub-pixel scale are realized by using a Transparent Conducting Oxide between the anode and the OLED.Following a step-by-step reasoning the work offers to follow all the phases of the realization of a prototype using this principle. In the first part, the technological steps of the processing of oxide cavities with a surface of 16µm² will be discussed. Then we will work on the development of a tandem OLED structure using both fluorescent and phosphorescent emitters optimized for micro-cavities. To this end optical simulation will be used. The two technological blocs will finally be put together to enlighten some issues specific for micro-écran technology and to give some clues to solve them
Izoulet, Antoine. « Élaboration de varistances à base d'oxyde de zinc à très haute tenue énergétique ». Toulouse 3, 2014. http://www.theses.fr/2014TOU30087.
Texte intégralThis work is of a collaboration project between Tridelta Parafoudres S. A. And CIRIMAT. It deals with the development of high energy varistors based on doped zinc oxide which respond to the current standard and to the dimensional specifications of Tridelta. The development of high energy varistors requires the increase of the varistor volume. The shaping of powder has been optimized in order to obtain a defect-free ceramic structure. To enhance the elimination of the shaping additives that are unwanted after the sintering, a cycle profile for debinding, providing a gain of both time and efficiency, has been developed. A research was conducted one the insulating glass in order to enable the varistor to work without additional protective layer. The step should be done without altering the nonlinear properties of the varistor. To reach the optimum properties of non-linearity, a careful study has been made on the sintering cycle. The aim of this part is to control the microstructure and thus the electrical properties of the varistor (non-linearity, energy holding stability under electrical stress). Approval tests were conducted by a certified laboratory according to a protocol defined by the standard (large amplitude shocks 100kA, series of long shocks 1200A-2ms). Finally, a study was carried out in order to optimize the stability of varistors under electrical stress. It leds to the establishment of a new formulation allowing both high induced energy dissipation capability and a high coefficient of nonlinearity
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.
Texte intégralThe 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
Flandre, Xavier. « Nouvelles électrodes pour pile à combustible à oxyde solide et électrolyseur à haute température ». Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10182/document.
Texte intégralIn the current context, fossil energy resources decrease and become more expensive, in addition to environmental concern. In this frame, solid oxide fuel cells (SOFC) are a promising green alternative energy source. Reversibly used, this system can also allow storage of electricity produced intermittently through the electrolysis of water. However, several bottlenecks still remain in terms of performances and stability of materials currently used to improve their lifetime and decrease their working temperature. In this doctoral thesis, our contribution focused on two cathode materials for SOFCs, Ba2Co9O14 and Ca3Co4O9+δ, and compounds derived from La4Ti2O10 which may be relevant as anode material. Our study mainly focused on the understanding of the physicochemical mechanisms involved in these materials by using impedance spectroscopy. For cobaltites, this study has led to the identification of the limiting parameters and will help the future optimization of complete stacks with better performances. For the La4Ti2O10 derived phases with the cuspidine structure, a neutron scattering study confirmed the oxygen diffusion mechanisms in these materials. However, their conductivity and catalytic properties remain insufficient to hope to use these compounds as SOFC’s anode, unlike other lanthanum titanates which display a layered perovskite structure
Dugrenil, Benoit. « Réalisation d’un micro-écran OLED haute luminance ». Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAT116.
Texte intégralThis study focuses on the development of high brightness OLED microdisplays based on active matrix (AMOLED). Because these devices are used into near-to-eye (NTE) applications and more precisely « see through » optical systems, high luminances are required. Compared to conventional microdisplays, the high luminances expected are around ten times higher.In order to emit a white spectrum from a top-emitting OLED (TE-OLED), color filters are mandatory to generate the RGB primaries. Nevertheless, by using these filters, the luminance is dramatically reduced because of the light absorption. Therefore, to be free of the filters, a first study is dedicated to the modulation of the optical cavity of the OLED. In this case, the direct generation of the colors is provided by the variation of the TCO anode thickness.The cavity effect observed into the TE-OLED depends on the semi-transparent cathode. The selectivity of the related cavity represents the bottleneck for emitting broad white spectra. To improve the white emission, a second approach deals with the realization of a TCO cathode coupled with a metallic grid.The appropriated materials and deposition techniques were firstly investigated before the characterization of OLED using a transparent anode to modulate the cavity in one hand and a transparent cathode to increase the light emission in another hand. Optical simulations and electrical modelling were employed to highlight the main behaviors driving these OLED. Following a discussion about the strength and the weakness of each structure, some hints of improvement were given
Toulemonde, Pierre. « Nouveaux oxydes supraconducteurs : la famille des cuprates à double couche de mercure ». Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10190.
Texte intégralBen, Elbahri Marwa. « Dévelοppement de matériaux cοmpοsites de haute cοnstante diélectrique ». Caen, 2016. http://www.theses.fr/2016CAEN2022.
Texte intégralThis 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
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.
Texte intégralHigh 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
Coutanceau, Martine. « Un nouvel oxyde mixte de cobalt : TlSr2CoO5 ». Phd thesis, Université Sciences et Technologies - Bordeaux I, 1996. http://tel.archives-ouvertes.fr/tel-00007501.
Texte intégralThommy, Léonard. « Développement de nouveaux matériaux d’électrodes pour convertisseurs électrochimiques à haute température : piles à combustible et électrolyseurs ». Nantes, 2015. http://archive.bu.univ-nantes.fr/pollux/show.action?id=7f5a6fca-209c-49d4-b02e-4d6eef28f439.
Texte intégralThe aim of this work is the development of new materials for the negative electrode of solid oxide fuel cells and electrolysers (SOFC and SOEC), showing a good electrocatalytic activity at intermediate temperatures. New BaIn0,3Ti0,7O3±δ-derived compounds Ba0. 5La0. 5Ti0. 3Mn0. 7O3 (BLTM) and Ba0. 5La0. 5In0. 3Ti0. 1Mn0. 6O3 (BLITIM) were developed in a first part of this work. Ni-BLTM/BIT07 et Ni-BLITIM/BIT07 symmetrical cells were fabricated by tape casting and co-sintering, and were optimised. A polarisation resistance (Rp) value of 0,20 Ω cm2 has been measured at 700°C under Ar/H2 (5%), for a nominal NiO-content of 40%m. In a second part of this work, new MIEC compound family derived from La0. 75Sr0. 25Cr0. 5-xMn0. 5O3-δ (LSCM) by substitution of ruthenium have been prepared. The introduction of ruthenium increased the total conductivity of the compound under both air and reducing atmosphere. The performances of La0. 75Sr0. 25Cr0. 4Mn0. 5Ru0. 1O3-δ (LSC0. 4MRu0. 1) as an anode material have been investigated in symmetrical cells with Ce0. 9Gd0. 1O1. 95 as electrolyte material, and compared to that of La0. 75Sr0. 25Cr0. 5Mn0. 3Ni0. 2O3-δ (LSCM0. 3Ni0. 2), LSCM, and LSCM impregnated with nickel. A metallic particle dispersion has been obtained at the surface of LSCM0. 3Ni0. 2 et LSC0. 4MRu0. 1 and it has been shown to improve a the part of the Rp linked to gas adsorption. The best performances have been obtained for LSC0. 4MRu0. 1. The comparison of the results obtained under Ar/H2 5% and under methane along with a comparison of the cell ageing allowed us to evaluate and discuss the interest of exsolution
Pugnat, Pierre. « Etude de l'irréversibilité et de l'anisotropie du vecteur aimantation des supraconducteurs à haute température critique ». Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10049.
Texte intégralBrizé, Virginie. « Elaboration de céramiques CaCu3Ti4O12 à haute constante diélectrique et réalisation de condensateurs "tout oxyde" par ablation laser pulsé ». Tours, 2006. http://www.theses.fr/2006TOUR4026.
Texte intégralThe oxide CaCu3Ti4O12 (CCTO) shows a very high permittivity (~ 105) in a large range of temperature (100-60K) and frequencies (10Hz-1MHz). A part of this study is an atttempt to deposit "all oxide" capacitors based on CCTO using the laser on CCTO using the laser ablation technique. At first, epitaxial films of CCTO were deposited on single crystal LaA1O3(100) (LAO) after optimisation of the target sintering. Capacitors LSNO/CCTO/LSNO/LAO with LaSrNiO4 (LSNO) as electrodes were then structured in-situ by shadow-masking. In an attempt to reduce the diffusion of La and Cu and to improve the quality interface with electrode, LSNO was replaced by CaCu3Ru4O12 which was isostructural of CCTO. In a second part, CCTO in the form of pure and doped powder and thin film was studied by electron spin resonance. New results are important to understand the mechanisms giving rise to the high permittivity value
Cásek, Petr. « Propriétés électroniques d'oxydes de métaux de transition ». Paris 11, 2004. http://www.theses.fr/2004PA112015.
Texte intégralIn this work we report results of our theoretical studies of the electronic properties of two different types of transition metal oxides. In the first part, we concentrate on the structural and electronic properties of SrTiO3 overlayers on MgO(001) using density functional theory (DFT) within the local density approximation (LDA). In particular, we show that only the TiO2/MgO contact is thermodynamically stable, and that many characteristics of the true SrTiO3(001)/MgO(001) interface are recovered already when a SrTiO3 bilayer is adsorbed (e. G. , vanishing valence band offset, structural distortions, charge transfer, etc. ). Considering an oxygen vacancy at the interface, we show that its formation energy is basically determined by the one of the corresponding clean surface. In the second part, we focus on the optical response of the high-Tc cuprate superconductors. We use a simple many-body hamiltonian and the finite temperature perturbation theory to calculate the real part of the conductivity. In particular, we explore the origin of the onset located for optimum doped Yba2CU3O(7-[delta]) around ~ 350 cm^(-1). We also discuss the position and the shape of the peak in the effective spectral function W(w)
Richard, Laurence. « Défauts, plasticité et propriétés physiques induites des supraconducteurs à haute température critique : YBa2Cu3O7-x ». Poitiers, 1997. http://www.theses.fr/1997POIT2265.
Texte intégralCatania, Philippe. « Synthèses, caractérisations et mises en forme du supraconducteur haute température YBa2Cu3O7 ». Montpellier 2, 1990. http://www.theses.fr/1990MON20258.
Texte intégralKentheswaran, Vasuki. « Alliages réfractaires à forte entropie : comportement mécanique sous sollicitations complexes, mise en place d’une nouvelle voie d’élaboration ». Thesis, Sorbonne Paris Cité, 2019. http://www.theses.fr/2019USPCD052.
Texte intégralFrom Japanese sabres to modern aircraft engines alloying elements have been used to enhance mechanical properties. Adding alloying elements to a main constituent enables to achieve a desired microstructure or to combine mechanical properties. High-entropy alloys, namely multicomponent metallic alloys, break with the past traditional approach since they contain several major elements in equiatomic or quasi-equiatomic proportions resulting in a single-phase disordered solid solution stabilised by its configurational entropy increased with the number of constituents, hence the name of such alloys. High-entropy alloys blaze a trail to new alloy design strategies and new type of metallic materials. The enthusiasm of the scientific community has been triggered by the oustanding mechanical properties of these alloys and particularly upon combining antagonist properties such as strength and ductility. Refractory high-entropy alloys are very promising materials for high temperature applications and need to be characterised upon various types of loading before considering them for potential applications. Process and characterisation are considered in the framework of this thesis. Under dynamic loading, the studied refractory high-entropy alloys with BCC structure exhibited either a thermal softening behaviour or a work-hardening behaviour. Fatigue endurance ratio has an oustanding level of 0.43 under four-point bending fatigue loading. The other aspect investigated in this study is the ability to process these alloys by powder metallurgy route and especially by Self-propagating High temperature Synthesis (SHS) and Spark Plasma Sintering (SPS)
Perriere, Loic. « Élaboration par solidification dirigée et comportement mécanique de céramiques eutectiques à base d'oxydes réfractaires : rôle de la microstructure sur la fissuration et la déformation plastique à haute température ». Phd thesis, Université Paris-Est, 2008. http://tel.archives-ouvertes.fr/tel-00348355.
Texte intégralVillain, Franck. « Etude de l'origine de l'acétaldéhyde présent dans le poly(téréphtalate d'ethylène glycol) soumis à hautes températures ». Rouen, 1991. http://www.theses.fr/1991ROUES054.
Texte intégralEyidi, Dominique. « Microstructures d'oxydes supraconducteurs à haute température critique à base de mercure ; modification par déformation plastique ». Poitiers, 1999. http://www.theses.fr/1999POIT2317.
Texte intégralBignon, Madeleine. « Contribution à la conception computationnelle d'alliages de titane ou à haute entropie : prédiction de l'occurrence de la transformation martensitique de trempe ou de déformation ». Thesis, Nantes, 2020. http://www.theses.fr/2020NANT4053.
Texte intégralThe object of this work is to develop tools for the design of titanium alloys displaying TRIP (TRansformation-Induced Plasticity) effect, through modelling the occurrence of martensitic transformation as a function of composition. The applicability of the approach to high entropy alloys is discussed. Using computational thermodynamics, and calculating the contribution of the elastic strain energy, we propose a method to predict the martensite start temperature (Ms). We suggest that the retention of the high temperature beta phase upon quenching may be due to the thermally activated character of martensite nucleation, rather than to an Ms below room temperature. Additionally, we exploit the phenomenological theory of martensite crystallography (PTMC) to suggest an explanation to the inhibition of martensite in conditions where it is thermo-elastically favourable. Martensite formation may in turn be prevented, for some compositions, by the impossibility to crystallographically accommodate the transformation via an invariant plane strain. Eventually, we use a multi-objective genetic algorithm to illustrate the approach through the theoretical design of alloys expected to display TRIP effect with maximized solid solution hardening and minimal environmental impact or geo-political risk. Other design examples show how alloys can be designed from recycled alloys, or how pairs of alloys can be simultaneously designed, in such a way as to obtain a bi-metal structure producible by additive manufacturing
Nuzzo, Manon. « Influence de l'environnement gazeux sur les performances électrochimiques de cellules à oxyde solide (SOC) en mode Electrolyse à Haute Température (EHT) ». Paris 6, 2013. http://www.theses.fr/2013PA066141.
Texte intégralHigh Temperature Steam Electrolysis (HTSE) is a promising technology for hydrogen production, leading candidate as future fuel. However, massive hydrogen production remains difficult considering the fast performance degradation of solid oxide electrolyser cells (SOEC) mainly due to extreme experimental conditions (high working temperature (700-1000°C), oxidising atmosphere, high current density). In these conditions, degradation is due to reactivity between SOEC components, evolution of their microstructure and internal stresses emphasized by temperature and gas composition gradients. This work is dedicated to the study of the influence of the gaseous environment on electrochemical performance on SOEC in HTSE mode and to the development of a homogeneous method for gas distribution over the SOEC surface to enable a more uniform cells operation and limit internal stresses. Commercial electrolyte supported cells are studied (Ni/CGO–3YSZ–LSM/YSZ). First to start with, the SOEC electrochemical behaviour is studied with a traditional experimental set-up. Electrochemical characterisations are carried out in situ through chronopotentiometry and impedance spectroscopy. Secondly, new specific experimental sets-up were developed in order to vary the homogeneity of the gas distribution over the hydrogen electrode. To finish with, the influence of the gas distribution method has been studied on the initial electrochemical behaviour and then on the SOEC durability
Henry, Sandrine. « Influence de la vapeur d'eau sur l'oxydation à haute température du chrome et de quelques aciers inoxydables ferritiques ». Grenoble INPG, 2000. http://www.theses.fr/2000INPG0122.
Texte intégralBoucetta, Hassiba. « Mécanismes de cristallisation du dioxyde de ruthénium lors de la vitrification des déchets de haute activité ». Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20031.
Texte intégralRuthenium, arising from the reprocessing of spent uranium oxide fuel, has a low solubility in glass melt. It crystallizes in the form of particles of RuO2 of acicular or polyhedral morphology dispersed in fission product and actinides waste containment glass. Since the morphology of these particles strongly influences the physico-chemical properties, the knowledge and the control of their mechanism of formation are of major importance. The goal of this work is to determine the chemical reactions responsible for the formation of RuO2 particles of acicular or polyhedral shape during glass synthesis. Using a simplification approach, the reactions between RuO2-NaNO3, and more complex calcine RuO2-Al2O3-Na2O and a sodium borosilicate glass are studied. In situ scanning electron microscopy and XANES at increasing temperatures are used to follow changes in composition, speciation and morphology of the ruthenium intermediate species. Those compounds are thoroughly characterised by SEM, XRD, HRTEM, and ruthenium K-edge X-ray absorption spectroscopy. This combined approach allows us to show that the ruthenium speciation modification during vitrification is the key of control of the morphology of RuO2 particles in the glass. In particular, the formation of a specific intermediate compound (Na3RuO4) is one of the main steps that lead to the precipitation of needle-shaped RuO2 particles in the melt. The formation of polyhedral particles, on the contrary, results from the direct incorporation of RuO2 crystals in the melt followed by an Ostwald ripening mechanism
Duc, Fabienne. « Structure du supraconducteur à haute Tc HgBa2CuO(4+(delta) : étude en fonction de la température ». Université Joseph Fourier (Grenoble ; 1971-2015), 1998. http://www.theses.fr/1998GRE10146.
Texte intégralJeanneau, Justin. « Synthèse et propriétés physiques sous haute pression de composés à base de Cr4+ ». Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY088.
Texte intégralAfter 25 years of research on the superconducting cuprates, the discovery of high Tc superconductivity in related iron based pnictides in 2008[1] has stimulated the search of new superconductors. In particular antiferromagnet (AFM) with high Néel temperature, moderate magnetic moments and with crystallographic 2D layers could be adequate parent phases for new unconventional superconductors. In particular, other systems with 3d transition elements are very interesting systems for potential new high Tc superconductors.In this context we have reinvestigated the physical properties of n=1, 2,3 and + members of the Srn+1CrnO3n+1Ruddlesden Popper (RP) series. We have successfully synthesized at HP-HT Sr2CrO4 (n=1), Sr3Cr2O7(n=2), Sr4Cr3O10 (n=3) and SrCrO3 (n=infinite). We present some results of several studies performed on these phases such as neutron powder diffraction, Synchrotron X-ray diffraction under high pressure and low temperature, electrical transport properties under high pressure. Even if no superconductivity was observed, interesting properties had been discovered such as an unusual “anti-Jahn-Teller” in Sr2CrO4 at low temperature or an orbital ordering in Sr3Cr2O7.To explore new Cr-based systems where superconductivity could potentially be induced by changing Cr-Cr interactions in the Sr2CrO4 and Sr3Cr2O7RP phases, new chromates have been synthesized under HP-HT by substituting Sr2+ with other alkaline earth elements in order to “play” with the cation size effect. For the n=1 RP Ca2CrO4 phase, substitution with Ca2+ as a replacing element lead to a weakening of both the insulating behavior and AFM ordering. Synthesis to form the n=2 RP Ca-based lead to the formation of the unexpected and new n=3 phase Ca4Cr2O10.Ba2+ as a replacing element broke the RP structure configuration and led to a new phase, whose crystal structure was solved using electron diffraction tomography.In 2014, superconductivity has been discovered in CrAs (Tc=2.2K at P=0.8GPa), the first superconducting Cr-based system. In this context, we have look for other AFM Cr-based system with relatively high Néel temperature and moderate Cr magnetic moment. In consequence, we investigated another system, the narrow-gap semiconductor CrSb2. We find a metal-insulating transition from transport measurement at 10 GPa for both polycrystalline and single crystals samples we synthesized. At this pressure, we also observed a phase transition on synchrotron XRD under pressure. Finally, pressure dependence of the AFM ordering had been established by NPD under high pressure
Wang, Kun. « Algorithmes et méthodes pour le diagnostic ex-situ et in-situ de systèmes piles à combustible haute température de type oxyde solide ». Phd thesis, Université de Franche-Comté, 2012. http://tel.archives-ouvertes.fr/tel-01017170.
Texte intégralCourtin, Emilie. « Mise en forme de revêtements sol-gel pour piles à combustible et électrolyseurs haute température ». Thesis, Tours, 2011. http://www.theses.fr/2011TOUR4031/document.
Texte intégralThis thesis describes the fabrication of thin films with controlled thickness and microstructure to synthesize YSZ electrolytes and LSCF electrodes using the sol-gel process, in order to decrease the working temperature of solid oxide fuel cells and electrolyzers. Composite sols are synthesized from powder dispersed in sol-gel solutions. This technique allows a good control of particles size and stoichiometric. The composite sols viscosity is tuned to process homogeneous films with thickness ranging from 5 to 20 μm on various supports. To fabricate dense electrolytes, two syntheses are developed: the first one in alcoholic media, the other one in aqueous media, which makes this process environment-friendly. The influence of the sintering treatment, the nature of support, the sol composition and stability on the film microstructure is studied to obtain dense films. LSCF composite sols are also prepared from a binder synthesized via the polymeric route in which a powder prepared from this same binder is dispersed, after calcination at 1000°C to obtain the pure perovskite structure. The sol composition is changed for synthesizing films with a good homogeneity. The films performances are measured in a full cell in order to evaluate their electrochemical performances in fuel cell and in electrolyzer cell
Cheikh, Monia. « Spectroscopie infrarouge à haute résolution et photodissociation à l'aide d'un laser à CO d'une molécule asymétrique : le chlorure de nitrosyle ». Paris 11, 1988. http://www.theses.fr/1988PA112085.
Texte intégralONCI est une toupie asymétrique §table en phase ga,euse. Son énergie de dissociation est relativement basse vers 1300 cm⁻ ᴵ ce qui permet d'envisager sa photodissociation rnultiphotonique ou par tranfert VV. Elle possède trois vibrations fondamentales v ₁ , v₂ et v ₃. V ₁ située à 1800 cm⁻ ᴵ et associée à la vibration NO, peut donner lieu à des coïncidences avec l'émission du laser à CO. V₂et et v ₃sont beaucoup plus basses à 596 et 332 cm⁻ ᴵ, ce qui donne une forte densité de niveaux à haute énergie vibrationnelle. L'irradiation de ONCI par le laser à CO utilisé en multiraies, la porte dans les états excités du mode v ₁. Le couplage éventuel entre les niveaux rotationnels des autres modes de combinaison peut conduire la dissociation de ONCI. L'étude par spectroscopie infrarouge à haute résolution de ONCI est nécessaire. En effet, l'étude de la bande v ₁ nous a permis de connaître les coincidences des raies d'absorption de ONCI avec celles émises par le laser à CO. Afin d'améliorer ces coincidences, on élargit les raies de ONCI par un "Puffer" : l'Argon. On a ausi interprété la bande v ₁ + v ₃ qui se prêterait à une excitation par le laser à co₂. Cette étude spectroscopique nous a permis de déterminer des constantes rotationnelles des états (100), (101) et (011). On a monté le dispositif expérimental nécessaire à l'expérience de photodissociation de ONCI. L'excitation infrarouge du mélange ONCI-Ar, par le laser à CO utilisé en multiraies conduît à la dissociation. Les produits sont analysés par spectroscopie d'absorption infrarouge à l'aide d'une diode laser. On a observé la croissance de l'absorption de NO
Antunes, Laurent. « Caractérisation de composites supraconducteurs aléatoires - phases au bismuth/argent : contribution à l'étude des jonctions faibles dans ces matériaux ». Phd thesis, Université Sciences et Technologies - Bordeaux I, 1998. http://tel.archives-ouvertes.fr/tel-00163366.
Texte intégralKazakov, Serguei. « A la recherche de nouveaux supraconducteurs à haute température critique dans le système Sr-K-Bi-O ». Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10169.
Texte intégralVirette, David. « Étude de transformées temps-fréquence pour le codage audio faible retard en haute qualité ». Rennes 1, 2012. http://www.theses.fr/2012REN1E014.
Texte intégralNoudem, Jacques Guillaume. « Texturation des céramiques supraconductrices Bi-Pb-Sr-Ca-Cu-O par combinaison des effets du champ magnétique et de la contrainte uniaxiale à haute température ». Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10169.
Texte intégralPourtier-Marty, Florence. « Étude et réalisation de jonctions tunnel et Josephson à partir d'oxydes supraconducteurs à haute température critique ». Grenoble INPG, 1994. http://www.theses.fr/1994INPG0092.
Texte intégralFortier, Alexandre. « Synthèse de poudres nanométriques d'oxydes mixtes de métaux par plasma inductif haute-fréquence comme matériau d'anode de pile à combustible à oxyde solide ». Mémoire, Université de Sherbrooke, 2004. http://savoirs.usherbrooke.ca/handle/11143/1282.
Texte intégralFortier, Alexandre. « Synthèse de poudres nanométriques d'oxydes mixtes de métaux par plasma inductif haute-fréquence comme matériau d'anode de pile à combustible à oxyde solide ». [S.l. : s.n.], 2004.
Trouver le texte intégralDelerue, Johann. « Matrices de bolomètres supraconducteurs à haute température critique pour l'infrarouge : matériaux, technologies et caractérisations optiques ». Paris 6, 2002. http://www.theses.fr/2002PA066098.
Texte intégralGillet, 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.
Texte intégralBen, Salem Ezzedine. « Halogénation et propriétés structurales et supraconductrices des oxydes La2-xBaxCuO4 (phases de type T) et La1,8-xSmxSr0,2CuO4 (phases de type T, T* ou T') ». Phd thesis, Université Sciences et Technologies - Bordeaux I, 1994. http://tel.archives-ouvertes.fr/tel-00139979.
Texte intégralXavier, Pascal. « Etude de la réponse hyperfréquence des vortex dans des couches minces supraconductrices à haute température critique ». Grenoble 1, 1994. http://www.theses.fr/1994GRE10034.
Texte intégralDecorse, Philippe. « Etude comparative des propriétés de surface et de volume d'oxydes de type pérovskite La#1#-#xSr#xMnO#3#+# (0x1, 0 ou 0) utilisables dans les piles à combustible haute température ». Dijon, 1997. http://www.theses.fr/1997DIJOS061.
Texte intégralLejars, Antoine. « Mécanisme de sélection de l'orientation préférentielle lors de la croissance de couches minces, application au dépôt d'oxyde de zinc par pulvérisation magnétron à impulsions de haute puissance ». Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0182/document.
Texte intégralA piezoelectric fiber constituted of ZnO cylindrical coating on a stainless steel wire has been achieved by High Power Impulse Magnetron Sputtering (HiPIMS) by using a prototype designed and assembled during this PhD work. The piezoelectric fiber can be used as a strain probe or as a vibration harvesting generator for embedded electronics. The analyses of deposited layer allow to understand ZnO growth mechanism in order to optimize to deposition process. A special emphasis has been placed on the selection of preferential orientation during the growth. The low volume of steel wire, allow to control his temperature by adjusting some process parameters, like the pressure and the average power. Temperature sensitive wires (e.g. polymer) can be treated in the mildest conditions. Preferential nucleation followed by self-epitaxy have been proposed to explain the very strong preferential orientation identified in coatings deposited at low temperature. At high peak current, preferential nucleation and evolutionary growth can promote the (101)* orientation. At highest peak currents no preferential orientation was identified and the high residual stress has been attributed to the excess of oxygen in the coating
Leckel, Olivier. « Structures accommodant la non-stoechiométrie dans l'oxyde supraconducteur Tl2Ba2CuO6±x à haute température critique : corrélation avec les propriétés supraconductrices ». Lyon 1, 1995. http://www.theses.fr/1995LYO10149.
Texte intégralYoboue, N'Goran Pamela. « Etude technologique pour l'amélioration des performances d'un capteur de gaz à oxyde métallique : développement d'une plateforme chauffante haute température et intégration de couche sensible nanostructurée ». Phd thesis, Université Paul Sabatier - Toulouse III, 2010. http://tel.archives-ouvertes.fr/tel-00509149.
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