Littérature scientifique sur le sujet « Oxyde à haute entropie »
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Articles de revues sur le sujet "Oxyde à haute entropie"
Pijotat, M., M. Prin, M. Soustelle et Ο. Touret. « Évolution de la texture d’un oxyde de cérium à haute température. I. Caractérisations ». Journal de Chimie Physique 91 (1994) : 37–49. http://dx.doi.org/10.1051/jcp/1994910037.
Texte intégralPijolaf, M., M. Prin, M. Soustelle et Ρ. Nortier. « Évolution de la texture d’un oxyde de cérium à haute température. II. Influence de la vapeur d’eau, de l’oxygène et du dopage aux ions Si4+ et Al3+ ». Journal de Chimie Physique 91 (1994) : 51–62. http://dx.doi.org/10.1051/jcp/1994910051.
Texte intégralPigeat, P., D. Paulmier, N. Pacia et B. Weber. « Évolution de l'émissivité normale monochromatique de WO3 en fonction de son épaisseur : Déduction des indices de réfraction complexes de cet oxyde á haute température entre 1 ET 10 μm ». Thin Solid Films 145, no 2 (décembre 1986) : 185–96. http://dx.doi.org/10.1016/0040-6090(86)90367-6.
Texte intégralLAURENT-BROCQ, Mathilde, et Jean-Philippe COUZINIÉ. « Alliages multi-composants à haute entropie - Concepts, microstructures et propriétés mécaniques ». Étude et propriétés des métaux, décembre 2017. http://dx.doi.org/10.51257/a-v1-re269.
Texte intégralThèses sur le sujet "Oxyde 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.
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