期刊
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
卷 40, 期 13, 页码 4585-4596出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijhydene.2015.01.153
关键词
Hydrogen storage; Magnesium hydride; Niobium fluoride; Mechanical alloying
资金
- Universidad Nacional de Cuyo, FONCyT PAE [133]
- CONICET [PIP 112 201101 00524]
A mixture of MgH2 and (7 mol%) NbF5 has been mechanically milled under Ar atmosphere. The evolution of the materials has been studied by in situ pressure monitoring, XRD, DSC, TG, TPD, SEM, and isothermal hydrogen absorption and desorption in a volumetric device. During milling, H-rich and F-rich solid solutions MgH2-xFx and MgHyF2-y are produced. After 40 h of milling both solutions merge into a single one with formula MgH1.60F0.40. This solid solution is stable under a thermal treatment of 90 h at 300 degrees C under 6000 kPa of H-2. Hydriding and dehydriding kinetics in the as-milled and cycled materials are considerably faster than in MgH2 milled without additive. Desorption temperature in DSC or TG is lowered 100 degrees C, and the material modified with NbF5 can be hydrided in less than 4 min at T = 250 degrees C. A H-rich solution is formed upon rehydriding the material, showing the reversibility of the process. The kinetic improvement seems to be due to a cooperative effect between MgHyF2-y and niobium hydride, the former providing seeding crystals for MgH2 nucleation, and the latter working as a gateway for hydrogen transfer. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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