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New Insight on the Hydrogen Absorption Evolution of the Mg–Fe–H System under Equilibrium Conditions
Mg2FeH6 is regarded as potential hydrogen and thermochemical storage medium due to its high volumetric hydrogen (150 kg/m3) and energy (0.49 kWh/L) densities. In this work, the mechanism of formation of Mg2FeH6 under equilibrium conditions is thoroughly investigated applying volumetric measurements, X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), and the combination of scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS) and high-resolution transmission electron microscopy (HR-TEM). Starting from a 2Mg:Fe stoichiometric powder ratio, thorough characterizations of samples taken at different states upon hydrogenation under equilibrium conditions confirm that the formation mechanism of Mg2FeH6 occurs from elemental Mg and Fe by columnar nucleation of the complex hydride at boundaries of the Fe seeds. The formation of MgH2 is enhanced by the presence of Fe. However, MgH2 does not take part as intermediate for the formation of Mg2FeH6 and acts as solid-solid diffusion barrier which hinders the complete formation of Mg2FeH6. This work provides novel insight about the formation mechanism of Mg2FeH6
Changing the dehydrogenation pathway of LiBH4-MgH2via nanosized lithiated TiO2
Nanosized lithiated titanium oxide (LixTiO2) noticeably improves the kinetic behaviour of 2LiBH4 + MgH2. The presence of LixTiO2 reduces the time required for the first dehydrogenation by suppressing the intermediate reaction to Li2B12H12, leading to direct MgB2 formation.Fil: Puszkiel, Julián Atilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Castro Riglos, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Karimi, F.. Helmholtz-zentrum Geesthacht; AlemaniaFil: Santoru, A.. Helmholtz-zentrum Geesthacht; AlemaniaFil: Pistidda, C.. Helmholtz-zentrum Geesthacht; AlemaniaFil: Klassen, T.. Helmholtz-zentrum Geesthacht; AlemaniaFil: Bellosta von Colbe, J. M.. Helmholtz-zentrum Geesthacht; AlemaniaFil: Dornheim, M.. Helmholtz-zentrum Geesthacht; Alemani
On the thermal stability of ultrafine-grained Al stabilized by in-situ amorphous Al2O3 network
Bulk Al materials with average grain sizes of 0.47 and 2.4μm, were fabricated by quasi-isostatic forging consolidation of two types of Al powders with average particle sizes of 1.3 and 8.9μm, respectively. By utilizing the native amorphous Al2O3 (am-Al2O3) film on the Al powders surfaces, a continuous, ~7nm thick, am-Al2O3 network was formed in situ in the Al specimens. Systematic investigation of the changes to the am-Al2O3 network embedded in the Al matrix upon heating and annealing up to 600°C was performed by transmission electron microscopy (TEM). At the same time, the stability of the Al grain structure was studied by transmission Kikuchi diffraction (TKD), electron back-scatter diffraction (EBSD), and TEM. The am-Al2O3 network remained stable after annealing at 400°C for 24h. In-situ TEM studies revealed that at temperatures ≥450°C, phase transformation of the am-Al2O3 network to crystalline γ-Al2O3 particles occurred. After annealing at 600°C for 24h the transformation was completed, whereby only nanometric γ-Al2O3 particles with an average size of 28nm resided on the high angle grain boundaries of Al. Due to the pinning effect of γ-Al2O3, the Al grain and subgrain structures remained unchanged during annealing up to 600°C for 24h. The effect of the am-Al2O3→γ-Al2O3 transformation on the mechanical properties of ultrafine- and fine-grained Al is discussed from the standpoint of the underlying mechanisms.Fil: Balog, Martin. Slovak Academy of Sciences; Eslovaquia. University of California at Davis; Estados UnidosFil: Hu, Tao. University of California at Davis; Estados UnidosFil: Krizik, Peter. Slovak Academy of Sciences; EslovaquiaFil: Castro Riglos, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Saller, Brandon D.. University of California at Davis; Estados UnidosFil: Yang, Hanry. University of California at Davis; Estados UnidosFil: Schoenung, Julie M.. University of California at Davis; Estados UnidosFil: Lavernia, Enrique J.. University of California at Davis; Estados Unido
A novel catalytic route for hydrogenation-dehydrogenation of 2LiH + MgB2: Via in situ formed core-shell LixTiO2 nanoparticles
Aiming to improve the hydrogen storage properties of 2LiH + MgB2 (Li-RHC), the effect of TiO2 addition to Li-RHC is investigated. The presence of TiO2 leads to the in situ formation of core-shell LixTiO2 nanoparticles during milling and upon heating. These nanoparticles markedly enhance the hydrogen storage properties of Li-RHC. Throughout hydrogenation-dehydrogenation cycling at 400 °C a 1 mol% TiO2 doped Li-RHC material shows sustainable hydrogen capacity of ∼10 wt% and short hydrogenation and dehydrogenation times of just 25 and 50 minutes, respectively. The in situ formed core-shell LixTiO2 nanoparticles confer proper microstructural refinement to the Li-RHC, thus preventing the material's agglomeration upon cycling. An analysis of the kinetic mechanisms shows that the presence of the core-shell LixTiO2 nanoparticles accelerates the one-dimensional interface-controlled mechanism during hydrogenation owing to the high Li+ mobility through the LixTiO2 lattice. Upon dehydrogenation, the in situ formed core-shell LixTiO2 nanoparticles do not modify the dehydrogenation thermodynamic properties of the Li-RHC itself. A new approach by the combination of two kinetic models evidences that the activation energy of both MgH2 decomposition and MgB2 formation is reduced. These improvements are due to a novel catalytic mechanism via Li+ source/sink reversible reactions.Fil: Puszkiel, Julián Atilio. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear. Gerencia Materiales.; Argentina. Helmholtz–Zentrum Geesthacht; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Castro Riglos, Maria Victoria. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Física de Metales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Ramallo Lopez, Jose Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Mizrahi, Martin Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Karimi, F.. Helmholtz–Zentrum Geesthacht; AlemaniaFil: Santoru, Antonio. Helmholtz–Zentrum Geesthacht; AlemaniaFil: Hoell, Armin. Helmholtz-zentrum Berlin; AlemaniaFil: Gennari, Fabiana Cristina. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear. Gerencia Materiales.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Arneodo Larochette, Pierre Paul. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear. Gerencia Materiales.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Pistidda, Claudio. Helmholtz–Zentrum Geesthacht; AlemaniaFil: Klassen, Thomas. Helmut Schmidt University; AlemaniaFil: Bellosta Von Colbe, J.M.. Helmholtz–Zentrum Geesthacht; AlemaniaFil: Dornheim, M.. Helmholtz–Zentrum Geesthacht; Alemani