Study of MgH2 + NbF5 mixtures: Formation of MgH2−xFx solid solutions and interaction with hydrogen
Study of MgH2 + NbF5 mixtures: Formation of MgH2−xFx solid solutions and interaction with hydrogen
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DOI：
10.1016/j.ijhydene.2015.01.153
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发表时间：
2015-04
影响因子：
7.2
通讯作者：
S. Pighin;G. Urretavizcaya;F. Castro
中科院分区：
文献类型：
--
作者：
S. Pighin;G. Urretavizcaya;F. Castro
在Ar气氛下对MgH_2和（7mol%）NbF_5的混合物进行了机械球磨。通过原位压力监测、XRD、DSC、TG、TPD、SEM和容量式等温吸放氢装置研究了材料的演变过程。在研磨过程中，会产生富氢和富氟的固溶体MgH2 − xFx和MgHyF2 − y。研磨40小时后，两种溶液合并成单一溶液，其式为MgH1.60F0.40。该固溶体在300 °C和6000 kPa H2下热处理90 h后是稳定的。氢化和脱氢动力学的球磨和循环材料是相当快的比在MgH2球磨无添加剂。用NbF5改性后的材料在250 ° C下的脱附温度降低了100 °C，在4min内即可完全脱附。在再结晶过程中形成了富AH溶液，表明了该过程的可逆性。动力学的改善似乎是由于MgHyF2 − y和氢化铌之间的协同效应，前者为MgH2成核提供晶种，后者作为氢转移的通道。
A mixture ofMgH2and (7 mol%)NbF5has been mechanically milled underAratmosphere. The evolution of the materials has been studied byin situpressure monitoring, XRD, DSC, TG, TPD, SEM, and isothermal hydrogen absorption and desorption in a volumetric device. During milling,H-rich andF-rich solid solutionsMgH2−xFxandMgHyF2−yare produced. After 40 h of milling both solutions merge into a single one with formulaMgH1.60F0.40. This solid solution is stable under a thermal treatment of 90 h at 300 °C under 6000 kPa ofH2. Hydriding and dehydriding kinetics in the as-milled and cycled materials are considerably faster than inMgH2milled without additive. Desorption temperature in DSC or TG is lowered 100 °C, and the material modified withNbF5can be hydrided in less than 4 min atT= 250 °C. AH-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 betweenMgHyF2−yand niobium hydride, the former providing seeding crystals forMgH2nucleation, and the latter working as a gateway for hydrogen transfer.