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Effect of Atomic Layer Fluorination on the Structural and Electrochemical Properties of LiNi 0.5 Mn 1.5 O 4 High Voltage Electrodes
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Solid-state design of alkali-mixed transition metal layered sulfides : synthesis and crystal chemistry
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Unlocking New Frontiers: Photo‐Isomerism and Magnetic Properties in Multifunctional Hetero‐Tetra‐Metallic Complexes
No full textInternational audienceHetero‐tetra‐metallic complexes, FeNOCuLnCo (Ln = Gd, Tb, Dy), combining magnetic properties and photo‐isomerism, were obtained through the rational assembly of the photo‐switching nitroprusside anion FeNO with new magnetic Schiff base CuLnCo precursors. Herein, we describe the synthesis and characterisation of these compounds followed by a demonstration of their multifunctional character. Particularly noteworthy is the FeNOCuTbCo complex, one of the few examples of a photo‐isomerizable single‐molecule magnet (SMM) and a significant first step toward achieving synergistic properties
Improving the reliability of, and confidence in, DFT functional benchmarking through active learning
No full textInternational audienceValidating the performance of exchange-correlation functionals is vital to ensure the reliability of DFT calculations. Typically, these validations involve benchmarking datasets. Currently, such datasets are typically assembled in an unprincipled manner, suffering from uncontrolled chemical bias, and limiting the transferability of benchmarking results to broader chemical space. In this work, a data-efficient solution, based on active learning, is explored to address this issue. Focusing -as a proof of principle -on pericyclic reactions, we start from the BH9 benchmarking dataset, and design a chemical space around this initial dataset by combinatorially combining reaction templates and substituents. Next, a surrogate model is trained to predict the standard deviation of the activation energies computed across a selection of 20 distinct DFT functionals. With this model, the designed chemical space is explored, enabling the identification of challenging regions, for which representative reactions are subsequently acquired. Remarkably, it turns out that the function mapping molecular structure to DFT functional divergence is readily learnable; convergence is reached upon the acquisition of less than 100 reactions. With our final model, a more challenging – and arguably more representative – pericyclic benchmarking dataset is curated, and we demonstrate that the functional performance has changed significantly compared to the original BH9 subset
Understanding the processability of graphite blend electrodes with silicon nanoparticles
No full textThe manufacturing process aims to optimize the parameters leading to enhanced Lithium-Ion Battery (LiB) electrode properties. Particularly, developing silicon/graphite blends could be an alternative for boosting LiB energy density while using the longstanding properties of graphite. Here, we report the manufacturing parameters impact of the mixing, coating, and calendering steps on the properties of silicon/graphite blend electrodes. The mixing process was assessed by the solid and silicon content dependency, where the viscosity increases when increasing the solid and decreasing the silicon content. Moreover, the slurry rheology directly impacts the mechanical stability of the electrode when coating using thicker comma gaps. The calendering step evidences a porosity threshold necessary for adequate ionic resistance and cycling life. We found that porosities between 45% to 56% for these silicon/graphite blends yield higher performance. Lower than 30% porosity highly impacts the electrochemical performance in a detrimental way
Modelling high power devices across scales
No full textInternational audienceElectrochemical double layer capacitors, often called supercapacitors, are energy storage systems which accumulate and release energy through reversible ion adsorption at electrode/electrolyte interfaces. Porous carbons are commonly used as electrode materials due to their relatively low cost and good electronic conductivity. Over the past decade, most of the simulations of supercapacitors were performed at the microscopic scale, using Molecular Dynamics (MD) simulations. This allowed to understand the adsorption of ions and the effect of surface porosity on some electrochemical properties. However it is well known from experiments that commercial materials are highly inhomogeneous, while molecular simulations, where electrode sizes are a few nanometers, only allow for the inclusion of a few pores. It is therefore necessary to simulate electrodes and supercapacitors at larger scales.To this end, we develop a software, Lattice Porous Carbon 3D (LPC3D), designed for mesoscopic simulations of capacitive properties of carbon-carbon capacitors, based on a lattice-gas model. The code calculates properties such as quantities of adsorbed ions, diffusion coefficients and Nuclear Magnetic Resonance (NMR) spectra for ions adsorbed in porous carbons. I will show how the mesoscopic model allows to bridge the gap between the time and length scales of atomistic simulations, accurate but computationally expensive, and experimental results such as electrochemical measurements and nuclear magnetic resonance spectroscopy. I will then describe how the latest code improvements allowed us to simulate systems with length scales up to hundreds to thousands of microns and how we are moving towards coupling LPC3D with molecular simulations codes (molecular DFT and MD simulations) to increase the accuracy of the model. I will also discuss possible perspectives to tackle different types of high power devices
Novel Inhibitors Of Organic Cation Transporters For The Treatment Of Mood Disorders
No full textThe present invention relates to novel inhibitors of organic cation transporters (OCT), having formula (I) or (II): (I) (II), and a pharmaceutically acceptable salt, solvate, enantiomer or tautomer of same. The present invention also relates to the use of these compounds as a drug for the prevention and/or treatment of mood disorders, such as depressive disorders or anxiety disorders
Recyclage par voie solide des alliages d’aluminium : conditions d’élaboration, microstructure et propriétés mécaniques
No full textThis thesis focuses on the solid-state recycling of AA6060 aluminum by hot extrusion. This process, which avoids remelting the scrap, reduces energy consumption by a factor of 3 to 4 compared with conventional recycling and limits material losses. It involves three steps: the compaction of machining chips to obtain a billet with an apparent density of 70%, reheating between 400 and 550 °C to reach the forming temperature, and extrusion, which welds the chips in the solid state and produces cylindrical profiles. This study concentrates on oxidation during processing, leading to the formation of an oxide network at chip boundaries after extrusion and on its influence on mechanical properties.Oxidation during reheating, comparable to an isothermal anneal, was studied chemically by X-ray Photoelectron Spectroscopy (XPS) and kinetically by ThermoGravimetric Analysis (TGA). Below 400 °C, oxidation remains limited and forms a continuous, protective amorphous alumina layer. Above 450 °C, magnesia islands form on the surface and grow according to parabolic kinetics. Two growth phases are observed: initially horizontal, where the islands maintain constant thickness while the coverage rate increases; then mixed, with an additional vertical growth that increases both the thickness and the coverage rate of the islands. Oxidation kinetics accelerate with temperature, and the parabolic rate constant follows an Arrhenius law, enabling the prediction of mass gain as a function of time and temperature. To limit oxidation during reheating, the temperature must remain below 400 °C or the time must be minimized.During extrusion, ex-situ hot compression tests on bulk samples analyzed by XPS, and chip billets analyzed by Transmission Electron Microscopy (TEM), show that thermomechanical coupling accelerates oxidation. Interrupted extrusion experiments reveal that this step occurs in two phases: densification, which closes the billet porosities and raises the apparent density to nearly 100%, and elongation, during which the highly deformed chips bond together. Different extrusion temperatures were studied. The density of the oxide network formed in the extruded profiles, measured by a microprobe, is 8 mm⁻¹, independently of the processing conditions. In contrast, the oxide dimensions, measured by TEM, increase with extrusion temperature: thicknesses range from 50 to 300 nm and lengths from 140 to 550 nm. As for reheating, the parabolic rate constants and their Arrhenius law were determined as a function of extrusion temperature.Precipitation hardening was evaluated by hardness measurements and TEM observations. Magnesium consumption by oxidation leads to precipitate free zones, which can be eliminated by a homogenization annealing at 550 °C for 1 hour. This new heat treatment was applied to extruded samples, and their mechanical properties were then measured by shear tests. A loss of shear ductility compared with non-recycled extrusions was observed, with fracture occurring mainly along chip boundaries. This loss increases with decreasing extrusion temperature, which could be explained by the reduction of the inter-oxide distance. However, the sample extruded at the lowest temperature, with the finest oxides, does not follow this trend.Finally, the overall results made it possible to establish a method for characterizing oxidation during solid-state recycling. This work also provided perspectives for improvement: further lowering the temperatures, improving the compaction step, increasing extrusion speed, or sheathing the chips.Cette thèse porte sur le recyclage par voie solide de l’aluminium AA6060 par extrusion à chaud. Ce procédé, sans refusion des déchets, réduit de 3 à 4 la consommation d’énergie par rapport au recyclage classique et limite les pertes de matière. Il comprend trois étapes : la compaction de copeaux d’usinage pour obtenir une billette de densité apparente de 70 %, le réchauffage entre 400 et 550 °C pour atteindre la température de mise en forme et l’extrusion, qui soude les copeaux à l’état solide et produit des profilés cylindriques. Cette étude se concentre sur l’oxydation au cours du procédé conduisant à la formation d’un réseau d’oxydes aux joints de copeaux après extrusion et sur son influence sur les propriétés mécaniques.L’oxydation au cours du réchauffage, assimilable à un recuit isotherme, est étudiée chimiquement par Spectroscopie Photoélectronique X (XPS) et cinétiquement par Analyse ThermoGravimétrique (ATG). En dessous de 400 °C, l’oxydation reste limitée et forme une couche d’alumine amorphe, continue et protectrice. Au-dessus de 450 °C, des îlots de magnésie se forment en surface et croissent selon une cinétique parabolique. Deux phases de croissance sont observées, la croissance est d’abord horizontale, les îlots sont d’épaisseur constante et le taux de recouvrement augmente, puis mixte, une croissance verticale s’ajoute, l’épaisseur et le taux de recouvrement des îlots augmentent. La cinétique d’oxydation accélère avec la température et la constante parabolique suit une loi d’Arrhenius, ce qui permet de prédire la prise de masse en fonction du temps et de la température. Pour limiter l’oxydation pendant le réchauffage, la température doit être inférieure à 400 °C ou le temps doit être minimisé.Lors de l’extrusion, l’étude ex-situ par compression à chaud sur des échantillons massifs étudiés par XPS et des billettes de copeaux étudiés par Microscope Electronique en Transmission (MET), montre que le couplage thermomécanique accélère l’oxydation. L’observation d’échantillons issus d’extrusions interrompues montre que cette étape du recyclage se déroule en deux phases : la densification, qui ferme les porosités de la billette et porte la densité apparente à quasiment 100 %, et l’élongation, où les copeaux fortement déformés se soudent. Différentes températures d’extrusion sont étudiées. La densité du réseau d’oxydes formé dans les profilés après extrusion, mesurée par microsonde de Castaing, est de 8 mm-1, indépendamment des conditions. A l’inverse, les dimensions des oxydes, mesurées au MET, augmentent avec la température d’extrusion, les épaisseurs sont de 50 à 300 nm et les longueurs de 140 à 550 nm. Comme pour le réchauffage, les constantes de cinétique parabolique et leur loi d’Arrhenius sont déterminées en fonction de la température d’extrusion.Le durcissement par précipitation est évalué par des mesures de dureté et des observations MET. La consommation du magnésium par l’oxydation engendre des zones appauvries en précipités durcissants, qui peuvent être supprimées par un recuit d’homogénéisation à 550 °C pendant 1 h. Le nouveau traitement thermique est appliqué aux échantillons extrudés puis leurs propriétés mécaniques sont mesurées par essais de cisaillement. Une perte de ductilité en cisaillement par rapport aux extrudés non-recyclés est observée avec une rupture principalement le long des joints de copeaux. Cette perte augmente avec la diminution de la température d’extrusion ce qui pourrait s’expliquer par la diminution de la distance inter-oxydes. Cependant, l’échantillon extrudé à la plus basse température avec les oxydes les plus fins ne suit pas cette tendance.Enfin, l’ensemble des résultats a permis de définir une méthode de caractérisation de l’oxydation au cours du recyclage par voie solide. Ce travail a également permis de définir des perspectives d’amélioration, réduire davantage les températures, améliorer l’étape de compaction, accélérer la vitesse d’extrusion ou encore gainer les copeaux
