1. Initial oxidation of low index Mg surfaces investigated by SCLS and DFTZhe Xing, Mattia Fanetti, Sandra Gardonio, Elsebeth Schröder, Dmytro Orlov, 2024, izvirni znanstveni članek Ključne besede: oxidation mechanism, surface core level shift, density functional theory, surface reconstruction, magnesium oxidation Objavljeno v RUNG: 25.07.2024; Ogledov: 766; Prenosov: 3 Celotno besedilo (7,92 MB) |
2. Efficiency of the grid energy storage technology based on iron-chloride material cycleUroš Luin, doktorska disertacija Opis: Future high-capacity energy storage technologies are crucial for a highly renewable energy mix, and their mass deployment must rely on cheap and abundant materials, such as iron chloride. The iron chloride electrochemical cycle (ICEC), suitable for long-term grid energy storage using a redox potential change of Fe2+/Fe, involves the electrolysis of a highly concentrated aqueous FeCl2 solution yielding solid iron deposits. For the high overall energy efficiency of the cycle, it is crucial maximizing the energy efficiency of the electrolysis process. The thesis presents a study of the influence of electrolysis parameters on energy efficiency, performed in an industrial-type electrolyzer system. We studied the conductivity of the FeCl2 solution as a function of concentration and temperature and correlated it with the electrolysis energy efficiency as a function of current density. The contribution of the resistance polarization increases with the current density, causing a decrease in overall energy efficiency. The highest energy efficiency of 89 ±3 % was achieved using
2.5 mol dm-3 FeCl2 solution at 70 °C and a current density of 0.1 kA m-2.
In terms of the energy input per Fe mass, this means 1.88 Wh g-1. The limiting energy input per mass of the Fe-deposit, calculated by extrapolating experimental results toward Eocell potential, was found to be 1.76 Wh g-1. For optimal long-duration electrolysis efficiency and performance, the optimal catholyte concentration range is
1-2 mol dm-3 FeCl2. We performed in situ X-ray absorption spectroscopy experimental studies to validate theoretical conclusions from literature related to the population and structure of Fe-species in the FeCl2 (aq) solution at different concentrations (1 - 4 mol dm-3) and temperatures (25 - 80 °C). This revealed that at low temperature and low FeCl2 concentration, the octahedral first coordination sphere around Fe is occupied by one Cl ion at a distance of 2.33 (±0.02) Å and five H2O at a distance of 2.095 (±0.005) Å. The structure of the ionic complex gradually changes with an increase in temperature and/or concentration. The apical H2O is substituted by a Cl ion to yield a neutral Fe[Cl2(H2O)4]0. The transition from the charged Fe[Cl(H2O)5]+ to the neutral Fe[Cl2(H2O)4]0 causes a significant drop in the solution conductivity, which well correlates with the existing state-of-the-art conductivity models. An additional steric impediment of the electrolytic cell is caused by the predominant neutral species present in the catholyte solution at high concentration. This correlates with poor electrolysis performance at a very high catholyte concentration (4 mol dm-3 FeCl2), especially at high current densities (> 1 kA m-2). The neutral Fe[Cl2(H2O)4]0 complex negatively affects the anion exchange membrane ion (Cl-) transfer and lowers the concentration of electroactive species (Fe[Cl(H2O)5]+) at the cathode surface. The kinetics of hydrogen evolution from the reaction between Fe powder and HCl acid was studied under the first-order reaction condition. The activation energy was determined to be 55.3 kJ mol-1. Ključne besede: ICEC, Power-to-Solid, energy storage, hydrogen, ferrous chloride, electrolysis, Fe deposition, efficiency, XAS, structure and population, ionic species, ion association, conductivity Objavljeno v RUNG: 18.04.2023; Ogledov: 2197; Prenosov: 33 (1 glas) Celotno besedilo (4,34 MB) |
3. Enhancing the mechanical properties of biodegradable Mg alloys processed by warm HPT and thermal treatmentsAndrea Mizelli-Ojdanic, Jelena Horky, Bernhard Mingler, Mattia Fanetti, Sandra Gardonio, Matjaž Valant, Bartosz Sulkowski, Erhard Schafler, Dmytro Orlov, Michael J. Zehetbauer, 2021, izvirni znanstveni članek Ključne besede: severe plastic deformation, SPD, precipitates, vacancy agglomerates, magnesium alloys, biodegradability Objavljeno v RUNG: 03.12.2021; Ogledov: 2264; Prenosov: 45 Povezava na celotno besedilo |
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6. Atomic-level mechanisms of magnesium oxidationSandra Gardonio, Mattia Fanetti, Matjaž Valant, Dmytro Orlov, 2016, objavljeni znanstveni prispevek na konferenci Opis: Magnesium has been recently becoming an increasingly popular material for various applications. However, excessive chemical reactivity, and oxidation rate in particular, is a major obstruction on the way of Mg to become widely adopted. A significant problem causing the lack of Mg reactivity control is insufficient understanding of mechanisms involved in the oxidation of magnesium surface. Herewith we present the investigation of atomic-level mechanisms of oxidation initiation and propagation in pure Mg. Namely, X-ray photoelectron spectroscopy at synchrotron Elettra was used as a surface sensitive direct method to determine the valence of Mg and O and the valence band states at the early stage of oxide formation over a principal, most densely packed, crystallographic plane (0001) in pure Mg. The mechanisms of oxygen adsorption on magnesium free surface followed by oxidation (i.e. initiation and kinetics of MgO formation) are clarified. Copyright © 2016 by The Minerals, Metals & Materials Society. All rights reserved. Ključne besede: Magnesium, Oxidation, Synchrotron radiation, X-ray photoelectron spectroscopy Objavljeno v RUNG: 25.08.2017; Ogledov: 5667; Prenosov: 0 Gradivo ima več datotek! Več... |
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8. Particle evolution in Mg-Zn-Zr alloy processed by integrated extrusion and equal channel angular pressing : evaluation by electron microscopy and synchrotron small-angle X-ray scatteringDmytro Orlov, Kei Ameyama, Yuri Estrin, Daniele Pelliccia, Xiya Fang, Laure Bourgeois, Nigel Kirby, Andrei Y. Nikulin, 2014, izvirni znanstveni članek Ključne besede: magnesium, intermetallic particles, severe plastic deformation, small angle X-ray scattering Objavljeno v RUNG: 16.06.2016; Ogledov: 6295; Prenosov: 19 Povezava na celotno besedilo |
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