140 research outputs found
The transformation of pentlandite to violarite under mild hydrothermal conditions: a dissolution-reprecipitation reaction
No full textAllan Pring, Christophe Tenailleau, Barbara Etschmann, Joel Brugger & Ben Grguri
Apostolic Life and Experience of God, According to Libermann
No full textTranslation of a paper read by the author, Father Bernard Tenailleau, of the French Seminary, Rome, to the Community of the Generalate and of the French Seminary, in the presence of Archbishop Tchidimbo, formerly of Guinea, on Libermann Day, February 2, 1980
Realization of aligned three-dimensional single-crystal chromium nanostructures by thermal evaporation
No full textAligned three-dimensional single-crystal chromium nanostructures are fabricated onto a silicon substrate by thermal evaporation in a conventional thermal evaporator, where the incident angle of Cr vapor flux with respect to the substrate surface normal is fixed at 88°. The effects of the deposition time and incident angle on the morphology of the resulting nanostructures are investigated. The achieved Cr nanostructures are characterized by scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and surface area measurement. This study provides a convenient way to fabricate three-dimensional single-crystal Cr nanostructures, which is suitable for batch fabrication and mass production. Finally, the same technique is employed to fabricate the nanostructures of other metals such as Ag, Au, Pd, and Ni
Integrating Al with NiO nano honeycomb to realize an energetic material on silicon substrate
No full textNano energetic materials offer improved performance in energy release, ignition, and mechanical properties compared to their bulk or micro counterparts. In this study, the authors propose an approach to synthesize an Al/NiO based nano energetic material which is fully compatible with a microsystem. A two-dimensional NiO nano honeycomb is first realized by thermal oxidation of a Ni thin film deposited onto a silicon substrate by thermal evaporation. Then the NiO nano honeycomb is integrated with an Al that is deposited by thermal evaporation to realize an Al/NiO based nano energetic material. This approach has several advantages over previous investigations, such as lower ignition temperature, enhanced interfacial contact area, reduced impurities and Al oxidation, tailored dimensions, and easier integration into a microsystem to realize functional devices. The synthesized Al/NiO based nano energetic material is characterized by scanning electron microscopy, X-ray diffraction, differential thermal analysis, and differential scanning calorimetry
Inorganic halide perovskite thin films preparation and characterization : Photovoltaic devices stabilization with 2D phase Cs2PbCl2I2 addition
No full textL'objectif des travaux de thèse est de développer un matériau photovoltaïque de 3e génération à base de pérovskites halogénées inorganiques qui soit plus stable et plus efficace. Dans le chapitre 1, un état de l'art sur les pérovskites halogénées est présenté, en mettant l'accent sur les phases 100% inorganiques présentant des propriétés intéressantes pour des applications photovoltaïques. Différentes voies de stabilisation sont discutées, notamment par la substitution cationique et la réduction de la dimension structurale. Le chapitre 2 décrit les méthodes de synthèse utilisées pour l'obtention des matériaux sous forme de poudres, monocristaux et films minces, ainsi que les techniques de caractérisation (micro-) structurales et physiques employées pour déterminer leurs propriétés. Dans le chapitre 3, la phase de type Ruddlesden-Popper Cs2PbCl2I2, mise au jour en 2018 par Li et ses collègues, fait l'objet d'une étude spécifique en raison de sa structure " 2D " originale. L'obtention sous la forme pulvérulente a été facilitée et les préparations de films minces et de monocristaux ont été développées au cours de ces travaux. Par la suite, des substitutions cationiques, sur le site du plomb, ont également permis de modifier les propriétés microstructurales et optoélectroniques. Dans le chapitre 4, les (trans-)formations de films minces de pérovskites dites "3D", de compositions CsPbI3 et CsPbI2Br, ont été analysées en détails par diffraction des rayons X in-situ. La phase noire a été mise en évidence juste après la première étape de spin-coating, à l'ambiante. Deux transitions de phases ont pu être caractérisée à la montée (jusqu'à 320°C) et à la descente. La présence de la phase "2D" permet d'accroître la stabilité de la phase noire de la forme 3D. Enfin au chapitre 5, l'optimisation réalisée sur des dépôts de couches minces d'un mélange de formes 3D et 2D "tout inorganique" est présentée. Un procédé de dépôt sous flux d'azote permet d''obtenir des films minces plus homogènes et compacts. Différents dopages visant à remplacer le plomb dans les films et améliorer la morphologie pour obtenir de meilleures performances ont été réalisés. La stabilité des films ainsi obtenus est discutée. Ces composés, intégrés dans des dispositifs photovoltaïques préparés au laboratoire XLIM de Limoges, ne permettent pas d'augmenter les rendements de conversion des cellules 3D seules mais montrent leur impact sur la stabilité de la phase "3D" noire. Enfin, une étude de la texture des films et des micro-contraintes permet de décrire les effets stabilisateurs de la phase noire.The objective of the thesis is to develop an efficient and stable 3rd generation photovoltaic material based on all- inorganic halide perovskite with 2D phase addition. In Chapter 1, a state of the art on halide perovskite is presented, with an emphasis on 100% inorganic phases exhibiting interesting properties for photovoltaic applications. Different stabilization routes are discussed, in particular by cationic substitution and reduction of the structural dimension. Chapter 2 describes the synthetic methods used to obtain materials in the form of powders, single crystals and thin films, as well as the (micro-)structural and physical characterization techniques used to determine their properties. In Chapter 3, the Ruddlesden-Popper Cs2PbCl2I2 phase, described in 2018 by Li and colleagues, is specifically investigated due to its "2D" structure. Obtaining this phase in the powder form was facilitated and preparations of thin films and single crystals were developed during this work. Subsequently, cationic substitutions, at the lead site, also made it possible to modify the microstructural and optoelectronic properties. The integration of this new "2D" structure, derived from perovskite structure, into a solar cell has been studied. In chapter 4, the thin films (trans-)formations of so-called "3D" perovskites, with stoichiometries CsPbI3 and CsPbI2Br, were analyzed in detail by in-situ X-ray diffraction. The black phase was highlighted just after the first spin-coating step, at room temperature. Two phase transitions could be characterized on the rise (up to 320 ° C) and on the way down. The presence of the "2D" phase increases the stability of the black phase of the 3D form. A "flash" heat treatment in air improves film quality and the influence of the "2D" phase on thin film stresses is discussed. Finally in chapter 5, the optimization carried out on thin film deposition of a mixture of 3D and 2D all-inorganic mix is presented. A nitrogen flow deposition process results in more homogeneous and compact thin films. Various dopings aiming at replacing lead in films and improving morphology to obtain better performance have been carried out. The stability of the films thus obtained is discussed. These compounds, integrated into photovoltaic devices prepared at the XLIM laboratory in Limoges, do not make it possible to increase the conversion yields of 3D cells alone but show a great impact on the stability of the black "3D" phase. A study of film texturing and micro-strains allows us to complete the information on thin layers of perovskites
Synthesis of NiO nanowalls by thermal treatment of Ni film deposited onto a stainless steel substrate
No full textTwo-dimensional nanostructures have a variety of applications due to their large surface areas.
In this study, the authors present a simple and convenient method to realize two-dimensional NiO nanowalls by thermal treatment of a Ni thin film deposited by sputtering onto a stainless steel substrate. The substrate surface area is supposed to be significantly increased by creating
nanowalls. The effects on the nanowall morphology of the thermal treatment temperature and duration are investigated. A mechanism based on the surface diffusion of Ni2+ ions from the Ni base film is then proposed for the growth of the NiO nanowalls. The as-synthesized NiO nanowalls are characterized by scanning electron microscopy, energy-dispersive x-ray analysis, x-ray diffraction, transmission electron microscopy and high resolution transmission electron microscopy
Prévention des infections nosocomiales à rotavirus dans le service de pédiatrie du centre hospitalier de Cholet
No full textANGERS-BU Médecine-Pharmacie (490072105) / SudocSudocFranceF
Échos du passé : éclairages nouveaux sur la cochlée des premiers homininés par une approche phylo-morphométrique
No full textNous examinons la variation cochléaire, témoin indirect des capacités auditives des premiers homininés ainsi que d’espèces actuelles de catarrhiniens, afin d’évaluer (i) le signal phylogénétique de la longueur externe relative de la cochlée (RECL) et de la surface de la fenêtre ovale (OWA), (ii) le modèle évolutif montrant la plus forte probabilité d’expliquer nos observations, (iii) certaines valeurs ancestrales d’homininés pour RECL et OWA. RECL montre un signal phylogénétique élevé sous un modèle brownien, mais aussi une corrélation étroite avec la masse corporelle. Notre méthode, basée sur un modèle évolutif, présente l’avantage de tenir compte des longueurs de branches (contrairement aux méthodes cladistiques, basées sur la parcimonie) dans un espace phylo-morphologique soulignant une évolution de RECL vers des valeurs significativement plus élevées uniquement au nœud (Homo erectus, Homo sapiens). Nous observons également que les fossiles StW 53 et KB 6067 (provenant respectivement de Sterkfontein et de Kromdraai) représentent probablement une ou deux forme(s) d’homininé(s) de plus petite taille corporelle et moins dérivée(s), par rapport à Paranthropus représenté à Swartkrans.We investigate cochlear variation, an indirect evidence of auditory capacities among early hominins and extant catarrhine species, in order to assess (i) the phylogenetic signal of relative external cochlear length (RECL) and oval window area (OWA), (ii) the evolutionary model with the highest probability of explaining our observed data, (iii) some hominin ancestral nodes for RECL and OWA. RECL has a high phylogenetic signal under a Brownian motion model, and is closely correlated with body mass. Our model-based method has the advantage over parsimony-based methods of incorporating branch lengths in a phylo-morphospace, and this shows RECL shifted towards significantly higher values at the Homo erectus - Homo sapiens node. We also observe that the StW 53 and KB 6067 fossil specimens from Sterkfontein and Kromdraai likely represent one or two distinct, smaller-bodied and less derived hominin form(s) compared to Paranthropus specimens represented at Swartkrans.</p
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