Local enhancement of hydrogen production by the hydrolysis of Mg17Al12 with Mg “model” material

The effect of galvanic coupling on the corrosion behavior of Mg and Mg17Al12 in Mg-Al alloys was studied by Scanning ElectroChemical Microscopy (SECM). The effect of galvanic coupling between Mg and Mg17Al12 was investigated using a “model” Mg+Mg17Al12 material with a controlled microstructure to evaluate the hydrogen evolution at a micrometric scale. SECM maps revealed that galvanic coupling between Mg and Mg17Al12 accelerates the corrosion rate (formation of a thicker passive layer) of both components. Mg17Al12 acts controversially to a conventional cathode in galvanic system since hydrogen production by its hydrolysis reaction was found to increase due to the electron transfer with the anode (Mg).Fil: Al Bacha, S.. Lebanese University, Faculty Of Sciences Ii; Líbano. Universite de Bordeaux; Francia. Université Paris-Saclay; FranciaFil: Farias, Eliana Desiree. Universite de Bordeaux; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Garrigue, Patrick. Universite de Bordeaux; FranciaFil: Zakhour, Mirvat. Lebanese University, Faculty Of Sciences Ii; LíbanoFil: Nakhl, Michel. Lebanese University, Faculty Of Sciences Ii; LíbanoFil: Bobet, Jean Louis. Universite de Bordeaux; FranciaFil: Zigah, Dodzi. Universite de Bordeaux; Francia. Université de Poitiers; Franci

LE BROYAGE ENERGETIQUE APPLIQUE A (- L'OBTENTION DE MELANGES COMPOSITES A BASE DE MAGNESIUM UTILISABLES POUR LE STOCKAGE DE L'HYDROGENE ; - LA MODIFICATION DES PROPRIETES MAGNETIQUES D'INTERMETALLIQUES A BASE DE GADOLINIUM)

LE MAGNESIUM EST UN CANDIDAT PROMETTEUR POUR LE STOCKAGE DE L'HYDROGENE (7,6% MASSIQUE). CEPENDANT, SON HYDRURE MGH 2 EST STABLE ET SES CINETIQUES D'HYDRURATION ET DE DESHYDRURATION SONT FAIBLES. AFIN DE PALIER A CES INCONVENIENTS, NOUS AVONS PREPARE PAR BROYAGE ENERGETIQUE DES MELANGES COMPOSITES A BASE DE MAGNESIUM MG + X% YNI ET MG + X%Y 1 XNI 2. L'AJOUT DE CES INTERMETALLIQUES (YNI ET/OU Y 1 XNI 2) AMELIORE CONSIDERABLEMENT LES CINETIQUES D'HYDRURATION ET DE DESHYDRURATION DU MG. LES MEILLEURES PROPRIETES DE SORPTION D'HYDROGENE SONT OBTENUES POUR LA COMPOSITION MASSIQUE MG + 25% YNI ET UN TEMPS DE BROYAGE DE 3 HEURES. LA MECANOSYNTHESE A AUSSI ETE UTILISEE AVEC SUCCES POUR ELABORER LES COMPOSES YNI ET Y 1 XNI 2. YNI A ETE OBTENU AVEC UNE STRUCTURE DIFFERENTE DE CELUI OBTENU PAR FUSION. Y 1 XNI 2 OBTENU PAR MECANOSYNTHESE (Y 0 , 9 7NI 2) EST INSTABLE THERMIQUEMENT ET SE DECOMPOSE EN DEUX PHASES Y 0 , 9 2NI 2 ET YNI 1 , 8 4. L'EFFET DU BROYAGE SUR LES PROPRIETES D'HYDRURATION DE YNI ET Y 1 XNI 2 OBTENUS APRES FUSION A ETE ETUDIE. D'AUTRE PART, L'EFFET DU BROYAGE SUR LES PROPRIETES STRUCTURALES ET MAGNETIQUES DES COMPOSES A BASE DE GADOLINIUM GDX 2 ET GDXAL (X = MN, NI, CU) A ETE DETERMINE. CET EFFET SUR LES PROPRIETES MAGNETIQUES DE GDMN 2 EST COMPARABLE A CELUI D'UNE PRESSION ISOSTATIQUE APPLIQUEE IN-SITU SUR LE MATERIAU, BIEN QUE LES CAUSES SOIENT PROBABLEMENT DIFFERENTES.BORDEAUX1-BU Sciences-Talence (335222101) / SudocBELFORT-UTBM-SEVENANS (900942101) / SudocSudocFranceF

Electronic structure and bonding of the hydrides Mg3TH7 (T = Mn, Re) from first principles

From pseudo-potentials and all-electrons computations within density functional theory, desorption energies within range of MgH2 and covalent like hydrogenated intermetallic compounds are identified for hydrogen rich Mg3TH7, (T = Mn, Re). The rhenium based compound is found with a lower desorption energy which has been quantified from the analysis of the Bader charges within the {TH6}5- complex anion as related with a decreasingly ionic charge on hydrogen from Mn to Re. The electronic densities of states show insulating compounds in agreement with literature relevant to this class of salt-like hydrides with a larger band gap for the Re compound. From chemical bonding analyses stronger Mn-H bonding versus Re-H is identified in agreement with desorption energies magnitudes favoring Mg3ReH7

Electronic structure and chemical bonding in LaIrSi-type intermetallics

The cubic LaIrSi type has 23 representatives in aluminides, gallides, silicides, germanides, phosphides, and arsenides, all with a valence electron count of 16 or 17. The striking structural motif is a three-dimensional network of the transition metal (T) and p element (X) atoms with TX3/3 respectively XT3/3 coordination. Alkaline earth or rare earth atoms fill cavities within the polyanionic [TX]δ− networks. The present work presents a detailed theoretical study of chemical bonding in LaIrSi-type representatives, exemplarily for CaPtSi, BaIrP, BaAuGa, LaIrSi, CeRhSi, and CeIrSi. DFT-GGA-based electronic structure calculations show weakly metallic compounds with itinerant small magnitude DOSs at EF except for CeRhSi whose large Ce DOS at EF leads to a finite magnetization on Ce (0.73 μB) and induced small moments of opposite sign on Rh and Si in a ferromagnetic ground state. The chemical bonding analyses show dominant bonding within the [TX]δ− polyanionic networks. Charge transfer magnitudes were found in accordance with the course of the electronegativites of the chemical constituents

Effect of ball milling in presence of additives (Graphite, AlCl3, MgCl2 and NaCl) on the hydrolysis performances of Mg17Al12

In most of the Mg–Al alloys, Al forms with Mg the intermetallic compound Mg17Al12. In order to understand the hydrogen production from the Mg–Al alloys waste by the hydrolysis reaction in “model” seawater (i.e. 3.5 wt % NaCl), hydrolysis with Mg17Al12 was investigated. The effect of ball milling time, the nature of the additives (graphite, NaCl, MgCl2 and AlCl3) and the synergetic effects of both graphite and AlCl3 were investigated. It has been established that increasing ball milling time up to 5 h is necessary to activate the intermetallic and to decrease sufficiently its crystallites and particles size. On one hand, the presence of AlCl3 provides the best hydrolysis performance (14% of the theoretical hydrogen volume in 1 h). On the other hand, the mixture obtained by simultaneous addition of graphite and AlCl3 shows the best hydrolysis performances with 16% of the theoretical H2 volume reached in 1 h

Hydrolysis properties, corrosion behavior and microhardness of AZ91 “model” alloys

A model AZ91 alloy containing the same amount of Mg and Mg17Al12 than a commercial AZ91 alloy was reproduced using various strategies. These “model” materials consist of a “homemade AZ91” powder, Mg melted or milled with Mg17Al12. The properties of the various model materials were compared to the commercial alloy (used as reference). The weak bond between Mg and Mg17Al12 is highlighted by SEM observations. Milling Mg with Mg17Al12 enhances the formation of microstructural defects due to the brittleness of the intermetallic. Vickers microhardness of pure Mg17Al12 is 250 Hv while that of AZ91 is 72 Hv. The hardness of Mg17Al12 decreases gradually from the center of the particle to its border in contact with Mg while the hardness of Mg is higher at the interface Mg-Mg17Al12. The galvanic coupling between Mg and Mg17Al12 improves the hydrolysis performance of the materials. The best hydrolysis performance was 80% of the theoretical capacity of hydrogen production reached in 60 minutes by the milled Mg + Mg17Al12. The preparation method of the models strongly affects their corrosion behavior. The passivation layer formed during the corrosion of highly-reactive materials affects the electrochemical measurements results. The mechanical properties and the corrosion behavior of the model materials depends on their composition and their structure

Clean hydrogen production by the hydrolysis of magnesium-based material: Effect of the hydrolysis solution

Autonomous low-pressure hydrogen on demand system was found promising to supply fuel cell technology for light or short distance mobility applications. Among the various hydrogen production technologies, the hydrolysis reaction method of magnesium-based materials is one of the most suitable. Magnesium (Mg) powder ball milled with the simultaneous addition of graphite and nickel under Ar was used as the hydrolysis reagent for hydrogen production. The effects of the solution composition (i.e. NaCl, NH4Cl and HCl) and the temperature (i.e. from 0 °C to 60 °C) of the solution on the hydrolysis performances were discussed. The hydrolysis reaction was complete (i.e. yield = 100%) in less than 5 minutes, except that performed at 0 °C, regardless the hydrolysis solution. The activation energy of the reaction decreases with lowering the pH of the hydrolysis solution. Semi-quantitative analysis was performed to evaluate the variation of CH4, CO, CO2 and moisture contents in the hydrogen produced by the hydrolysis. The exothermicity of the reaction and the composition of the hydrolysis solution showed a major impact on the purity of hydrogen. Under standard pressure and ambient temperature conditions, the hydrolysis of magnesium-based materials is considered as a clean hydrogen production technique. Our results should be taken as the starting point to evaluate the purity of the hydrogen produced by the hydrolysis of Mg-based materials according to the ISO standard 14687:2019

Towards polymeric nanoparticles with multiple magnetic patches

Fabricating future materials by self-assembly of nano-building blocks programmed to generate specific lattices is among the most challenging goals of nanotechnology and has led to the recent concept of patchy particles. We report here a simple strategy to fabricate polystyrene nanoparticles with several silica patches based on the solvent-induced self-assembly of silica/polystyrene monopods. The latter are obtained with morphological yields as high as 99% by seed-growth emulsion polymerization of styrene in the presence of 100 nm silica seeds previously modified with an optimal surface density of methacryloxymethyl groups. In addition, we fabricate “magnetic” silica seeds by silica encapsulation of preformed maghemite supraparticles. The polystyrene pod, i.e., surface nodule, serves as a sticky point when the monopods are incubated in a bad/good solvent mixture for polystyrene, e.g., ethanol/tetrahydrofuran mixtures. After self-assembly, mixtures of particles with two, three, four silica or magnetic silica patches are mainly obtained. The influence of experimental parameters such as the ethanol/tetrahydrofuran volume ratio, monopod concentration and incubation time is studied. Further developments would consist of obtaining pure batches by centrifugal sorting and optimizing the relative position of the patches in conventional repulsion figures

YNi and its hydrides : phase stabilities, electronic structures and chemical bonding properties from first principles

Within density functional theory, establishing the equations of states of previous termYNinext term in two different controversial previous termstructuresnext term in the literature, leads to determine the orthorhombic FeB-type as the ground state one with small energy difference. For YNiH3 and YNiH4 previous termhydridesnext term crystallizing in the orthorhombic CrB-type previous termstructurenext term the geometry optimization and the ab initio determination of the H atomic positions show that the previous termstabilitynext term of hydrogen decreases from the tri- to the tetra- previous termhydride.next term New states brought by hydrogen within the valence band lead to its broadening and to enhanced localization of metal density of states. The previous termchemical bondingnext term analysis shows a preferential Ni–H previous termbondingnext term versus Y–H

Rapid and direct reactive synthesis of Ti–Al intermetallics by microwave heating of TiH2 and Al powder without microwave susceptor

TiAl and TiAl3 titanium aluminide intermetallic compounds are synthesized directly within a few ten seconds by microwave technique. An initial mixture of TiH2 and Al powders has been used. Such mixture avoids the use of a microwaves susceptor. The hydrogen desorbed during the experiment keep the mixture in a reductive atmosphere thus avoiding possible oxidation. The role of TiH2 is then: (i) to act as a microwave absorber, (ii) to provide a reductive atmosphere and (iii) to provide energy through the hydrogen release reaction. The formation of the various intermetallics has been highlighted by X-ray diffraction and EPMA analysis