12 research outputs found

    Microstructure and Corrosion Behavior of Advanced Alloys

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    In many industrial applications, metallic materials are exposed to harsh operating conditions. Due to a combination of chemical and thermal stresses, the constructional and functional materials are degraded, and their utility properties are lost. These undesirable events are of a physicochemical nature and are commonly known as ‘corrosion’. In this Special Issue Book, 3 reviews and 18 original research papers focused on the complex relationships between the microstructure, phase constitution, and corrosion behavior of metallic materials are collected. Both high temperature and low temperature corrosion studies are included as they investigate the physicochemical processes at the material interfaces. Furthermore, possibilities for increasing the corrosion resistance of metallic materials are studied by means of surface modification and application of protective layers. This Special Issue Book, Microstructure and Corrosion Behavior of Advanced Alloys, displays the diversity and complexity of modern corrosion research. It is hoped that it will become a valuable source of reference for corrosion scientists

    Metals Challenged by Neutron and Synchrotron Radiation

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    Neutron and Synchrotron radiation methods have matured to become powerful techniques for the study of a vast range of materials, including metals. The characterization methods comprise the categories of diffraction, spectroscopy and imaging, which themselves can alter greatly in detail, to include hundreds of variants, problems and sample environments. In a similar way, their applications to metals and hard condensed matter materials cover disciplines spanning engineering, physics, chemistry, materials science and their derivatives such as geology, energy storage, etc. 
 The present book, “Metals Challenged by Neutron and Synchrotron Radiation” is a first compilation in Metals of 20 original and review works on research utilizing or designing those state-of-the-art techniques at modern facilities. The Editorial reviews the context of and identifies thematic links between these papers, grouping them into five interwoven themes, namely Sintering Techniques and Microstructure Evolution, Titanium Aluminides and Titanium Alloys Under Extreme Conditions, Metallic Glass and Disordered Crystals, In Situ and Time-Resolved Response to Mechanical Load and Shock, and Thin Films and Layers. This book represents a good cross-section of the status quo of neutron and synchrotron radiation with respect to questions in the metallurgical field, which by far is not exhaustive. Nor are the methods and other materials, which motivated me to the creation of a new sister-journal, entitled Quantum Beam Science. With this, I would like to thank all authors, reviewers and contributors behind the scene for the creation of this work, presenting to you a piece of interesting reading and reference literature

    Il Museo di Storia Naturale dell'UniversitĂ  degli Studi di Firenze. Le collezioni mineralogiche e litologiche | The Museum of Natural History of the University of Florence.The Mineralogical and Lithological Collections

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    The Museum of Natural History of the University of Florence, founded in 1775 by Grand Duke Pietro Leopoldo d'Asburgo Lorena, is one of the oldest and most prestigious scientific museums in the world. The fourth volume on the Collections of the Mineralogy and Lithology Section, published like the previous volumes by the Firenze University Press, fits perfectly in the series dedicated to the collections of the University's Museum System. The first part of the book describes in great detail the paths that led to the formation of the collections, starting with those dating to the Medici period and arriving at the specimens collected during recent expeditions. The second part illustrates and documents the extraordinary specimens of minerals, hardstone carvings and meteorites which represent the material patrimony of this section. Particular attention is given to the holotypes, the Elban Collection and the minerals of pegmatites, as well as the methods and solutions adopted to realize the project of the new museum exhibition set-up. The third and last part describes the studies carried out on the materials: from the minerals of the systematic collections to the rock specimens that recount not only the geodiversity of a region but also the history of a city

    Metal oxide, Mixed oxide, and hybrid metal@oxide nanocrystals : size-and shape-controlled synthesis and catalytic applications

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    Le contrĂŽle de la taille et de la morphologie de nanocristaux d’oxydes mĂ©talliques simples, d’oxydes mixtes et d’oxydes mĂ©talliques hybrides est un sujet de grand intĂ©rĂȘt. La dĂ©pendance de leur propriĂ©tĂ©s physio-chimiques avec leurs taille et morphologies, gĂ©nĂšrent une variĂ©tĂ© de leur applications dans plusieurs domaines. Cependant, le dĂ©vellopement des nanocristaux en controllant la taille, la forme, l’assemblage et l’homogĂ©nĂ©itĂ© de la composition chimique pour l’optimisation de propriĂ©tĂ© spĂ©cifiques demandent la combinaison de nombreux parametres de synthĂšse. Les trois diffĂ©rentes approches ont Ă©tĂ© dĂ©veloppĂ©es dans le cadre de la thĂšse pour la synthĂšse d’une variĂ©tĂ© de nouveaux nanomatĂ©riaux d’oxydes simples, d’oxydes mixtes et d’oxydes mĂ©talliques hybrides dont la taille et la forme ont Ă©tĂ© bien controllĂ©es. Ces mĂ©thodes ont Ă©tĂ© nommĂ©es comme des mĂ©thodes solvo-hydrothermiques assistĂ©es par des molĂ©cules structurantes Ă  l’état monophasique (eau ou eau/Ă©thanol) et Ă  l’état biphasique (eau-toluĂšne). Nos approches de synthĂšse ont permi de prĂ©parer des nanocristaux des oxydes de mĂ©taux de transition (V, Cr, Mn, Co, Ni, In), et des terres rares (Sm, Ce, La, Gd, Er, Ti, Y, Zr), ainsi que des oxydes mĂ©talliques mixtes (tungstate, orthovanadate, molybdate). Ces nanomatĂ©riaux sont sous forme colloĂŻdale mono-dispersĂ©e qui prĂ©sente une cristallinitĂ© Ă©levĂ©e. La taille et la forme de tels nanocristaux peuvent facilement ĂȘtre contrĂŽlĂ©es par une simple variation des paramĂštres de synthĂšse telle que la concentration de prĂ©curseurs, la nature de la molĂ©cule structurante, la tempĂ©rature et le temps de rĂ©action. A large variĂ©tĂ© de techniques a Ă©tĂ© utilisĂ©e pour la caracterisation de ces nanomatĂ©riaux telles que TEM/HRTEM, SEM, SAED, EDS, XRD, XPS, FTIR, TGA-DTA, UV-vis, photoluminescence, BET. Les propriĂ©tĂ©s catalytiques de ces matĂ©riaux ont aussi Ă©tĂ© Ă©tudiĂ©es. Dans ce travail, le contrĂŽle de la cinĂ©tique de croissance des nuclĂ©ides ainsi que le mĂ©canisme gouvernant la forme qui conduit Ă  la taille et la morphologie finale du nanocrystal ont Ă©tĂ© proposĂ©. L’effet de la taille et de la forme des nanoparticules d’oxyde mĂ©tallique hybrides sur les propriĂ©tĂ©s catalytiques pour la rĂ©action d’oxydation du CO et la photo-dĂ©gradation du bleue de mĂ©thylĂšne a Ă©tĂ© aussi Ă©tudiĂ©. Car les catalyseurs existant actuellement Ă  base de mĂ©taux nobles sont trĂšs couteux et en plus trĂšs sensibles Ă  l’empoisonnement par le gas H2S ou les Ă©missions polluantes de SOx. L’activitĂ© catalytique des nanocristaux d’oxydes mĂ©tallique hybrides Cu@CeO2 de formes cubiques dans l’oxydation de CO et de Ag@TiO2 de formes de ceinture dans la photo dĂ©gradation du bleue de mĂ©thylĂšne ont montrĂ© la dĂ©pendance de la taille et la forme des nanocristaux avec leur propriĂ©tĂ©s catalytiques.The ability to finely control the size and shape of metal oxide, mixed metal oxide, hybrid metal/oxide nanocrystals has become an area of great interest, as many of their physical and chemical properties are highly dependent on morphology, and the more technological applications will be possible for their use. Large-scale synthesis of such high-quality nanocrystals is the first and key step to this area of science. A tremendous effort has recently been spent in attempt to control these novel properties through manipulation of size, shape, structure, and composition. Flexibly nanocrystal size/shape control for both monodisperse single and multiple-oxide nanomaterial systems, however, remains largely empirical and still presents a great challenge. In this dissertation, new synthetic approaches have been developed and described for the synthetic design of a series of colloidal monodisperse metal oxide, mixed metal oxide, hybrid metal-oxide nanocrystals with controlled size and shape. These materials were generally characterized using TEM/HRTEM, SEM, SAED, EDS, XRD, XPS, FTIR, TGA-DTA, UV-vis, photoluminescence, BET techniques. Effect of the size and shape of these obtained hybrid metal-oxide nanocrystals on the catalytic properties is illustrated. We have developed three different new surfactant-assistant pathways for the large-scale synthesis of three types of nanomaterials including metal oxide, mixed metal oxide, hybrid noble-metal-oxide colloidal monodisperse nanocrystals. Namely, the solvo-hydrothermal surfactant-assisted methods in one-phase (water or water/ethanol) and two-phase (water-toluene) systems were used for the synthesis of metal oxide (transition metal-V, Cr, Mn, Co, Ni, In and rare earth-Sm, Ce, La, Gd, Er, Ti, Y, Zr) and mixed metal oxide (tungstate, orthovanadate, molybdate). The seed-media growth with the assistant of bifunctional surfactant was used for the synthesis of hybrid noble metal@oxide (Ag@TiO2, (Cu or Ag)@CeO2, Au/tungstate, Ag/molybdate, etc.) nanocrystals. A significant feature of our synthetic approaches was pointed out that most resulting nanocrystal products are monodisperse, high crystallinity, uniform shape, and narrow distribution. The size and shape of such nanocrystals can be controlled easily by simple tuning the reaction parameters such as the concentration of precursors and surfactants, the nature of surfactant, the temperature and time of synthetic reaction. The prepared nanocrystals with the functional surface were used as the building blocks for the self-assembly into hierarchical mesocrystal microspheres. The effective ways how to control the growth kinetics of the nuclei and the shape-guiding mechanisms leading to the manipulation of morphology of final products were proposed. Our current approaches have several conveniences including used nontoxic and inexpensive reagents (most using inorganic metal salts as starting precursors instead of expensive and toxic metallic alkoxides or organometallics), relatively mild conditions, high-yield, and large-scale production; in some causes, water or ethanol was used as environmentally benign reaction solvent. Catalytic activity and selectivity are governed by the nature of the catalyst surface, making shaped nanocrystals ideal substrates for understanding the influence of surface structure on heterogeneous catalysis at the nanoscale. Finally, this work was concentrated on demonstration of heterogeneous catalytic activity of hybrid metal-oxide nanomaterials (Cu@CeO2, Ag@TiO2) as a typical example. We synthesized the high-crystalline titanium oxide and cerium oxide nanocrystals with control over their shape and surface chemistry in high yield via the aqueous surfactant-assist method. The novel hybrid metal-oxide nanocrystals were produced by the depositing noble metal ion (Cu, Ag, Au) precursors on the pre-synthesized oxide seeds via seed-mediated growth. The catalytic activity of these metal-oxide nanohybrids of Cu@CeO2 nanocubes for CO oxidation conversion and Ag@TiO2 nanobelts for Methylene Blue photodegradation with size/shape-dependent properties were verified
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