Auswahl der wissenschaftlichen Literatur zum Thema „Oxydes à haute entropie“
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Zeitschriftenartikel zum Thema "Oxydes à haute entropie"
Sacuto, Alain, Yann Galais, Maximilien Cazayous und Sarah Houver. „La supraconductivité à haute température dans les oxydes de cuivre : où en est-on ?“ Reflets de la physique, Nr. 70 (Oktober 2021): 4–17. http://dx.doi.org/10.1051/refdp/202170004.
Der volle Inhalt der QuelleMAKNI, Amine, Abdallah HAOUAM, Jérôme FAVERGEON, Laurent LAHOCHE und Gérard MOULIN. „Caractérisation par émission acoustique de la formation des oxydes obtenus sur l’acier sollicité en flexion à haute température sous atmosphère contrôlée“. Revue des composites et des matériaux avancés 27, Nr. 1-2 (30.06.2017): 209–26. http://dx.doi.org/10.3166/rcma.27.209-226.
Der volle Inhalt der QuelleLAURENT-BROCQ, Mathilde, und Jean-Philippe COUZINIÉ. „Alliages multi-composants à haute entropie - Concepts, microstructures et propriétés mécaniques“. Étude et propriétés des métaux, Dezember 2017. http://dx.doi.org/10.51257/a-v1-re269.
Der volle Inhalt der QuelleDissertationen zum Thema "Oxydes à haute entropie"
Osenciat, Nicolas. „Propriétés de transport dans les oxydes à haute entropie“. Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF005.
Der volle Inhalt der QuelleThe 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.
Der volle Inhalt der QuelleThis 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.
Der volle Inhalt der QuelleThis 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.
Der volle Inhalt der QuelleThis 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.
Der volle Inhalt der QuelleBarriquand, François. „Rmn dans les oxydes supraconducteurs a haute temperature critique“. Paris 11, 1991. http://www.theses.fr/1991PA112345.
Der volle Inhalt der QuelleLannelongue, Pierre. „Oxydes polycationiques pour supercondensateurs à haute densité d'énergie volumique“. Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS146/document.
Der volle Inhalt der QuelleSupercapacitors 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.
Der volle Inhalt der QuelleHigh 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.
Der volle Inhalt der QuelleThis 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.
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