The effect of microstructure on the hydrogenation of Mg/Fe thin film multilayers
The effect of microstructure on the hydrogenation of Mg/Fe thin film multilayers
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微观结构对Mg/Fe薄膜多层膜氢化的影响
DOI：
10.1016/j.ijhydene.2014.08.035
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发表时间：
2014
影响因子：
7.2
通讯作者：
B. Dam
中科院分区：
文献类型：
--
作者：
Lennard Mooij;T. Perkisas;G. Pálsson;H. Schreuders;M. Wolff;B. Hjörvarsson;S. Bals;B. Dam
当纳米氢化镁与钛和铁等材料接触时，可以同时受到保护和热力学不稳定。我们通过光学技术氢谱研究了薄膜 Fe/Mg/Fe/Pd 多层膜中一维纳米限制的 Mg (<14 nm) 薄层的氢化。 Fe/Mg/Fe 多层中纳米级镁层的氢化令人惊讶地显示出多个平台压力的存在，其性质与厚度有关。相反，氢解吸通过单一平台发生，该平台不依赖于镁层厚度。通过 X 射线衍射/反射测量和截面 TEM 的结构和形貌分析，我们发现沉积在 Fe 上的 Mg 层粗糙度很大，并且还包含大角度晶界 (GB)。当在 Ti 上生长时，Mg 层粗糙度较低，并且未检测到大角度 GB。从 Ti/Mg/Fe 多层中，其中 Mg 层是平坦的并且几乎没有或没有晶界，我们得出结论，MgH2 确实因与 Fe 的界面而不稳定。在这种情况下，与 Ti/Mg/Ti 多层中 Mg 的氢化相比，吸收平台压力和解吸平台压力均增加了两倍。我们假设 Fe/Mg/Fe 多层中的晶界充当 Pd 的扩散途径，众所周知，当两种材料共享界面时，Pd 会极大地改变 Mg 的氢化行为。
Nanoconfined magnesium hydride can be simultaneously protected and thermodynamically destabilized when interfaced with materials such as Ti and Fe. We study the hydrogenation of thin layers of Mg (<14 nm) nanoconfined in one dimension within thin film Fe/Mg/Fe/Pd multilayers by the optical technique Hydrogenography. The hydrogenation of nanosized magnesium layers in Fe/Mg/Fe multilayers surprisingly shows the presence of multiple plateau pressures, whose nature is thickness dependent. In contrast, hydrogen desorption occurs via a single plateau which does not depend on the Mg layer thickness. From structural and morphological analyses with X-ray diffraction/reflectometry and cross-section TEM, we find that the Mg layer roughness is large when deposited on Fe and furthermore contains high-angle grain boundaries (GB's). When grown on Ti, the Mg layer roughness is low and no high-angle GB's are detected. From a Ti/Mg/Fe multilayer, in which the Mg layer is flat and has little or no GB's, we conclude that MgH2is indeed destabilized by the interface with Fe. In this case, both the ab- and desorption plateau pressures are increased by a factor two compared to the hydrogenation of Mg within Ti/Mg/Ti multilayers. We hypothesize that the GB's in the Fe/Mg/Fe multilayer act as diffusion pathways for Pd, which is known to greatly alter the hydrogenation behavior of Mg when the two materials share an interface.