2Mg–Fe and 2Mg–Fe + 5%C mixtures processed by hot extrusion: Influence of carbon on hydrogen sorption properties
2Mg–Fe and 2Mg–Fe + 5%C mixtures processed by hot extrusion: Influence of carbon on hydrogen sorption properties
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DOI：
10.1016/j.jallcom.2010.11.035
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发表时间：
2011-06
影响因子：
6.2
通讯作者：
R. Cerutti;G. F. Lima;C. S. Kiminami;W. Botta;A. Jorge
中科院分区：
文献类型：
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作者：
R. Cerutti;G. F. Lima;C. S. Kiminami;W. Botta;A. Jorge
镁是一种很有前途的储氢材料，但其吸附温度高，吸附动力学慢，限制了其应用。主要努力集中在克服这两个障碍上。合金化、纳米结构和/或催化剂，特别是在低温下，极大地改善了镁粉的氢化动力学。由于镁基块体材料中的氢脱附仍然处于临界高温，这是其实际应用的主要障碍，因此仍需进一步研究以达到块体材料的相同性质。本工作的目的是评估以下变量对块体镁基复合材料脱附温度的降低和氢化动力学的提高：颗粒/颗粒尺寸、缺陷密度、铁作为催化剂的使用、体积修改和碳作为孔限制元素的存在。我们比较了用高能球磨法制备块体样品的2 mg-Fe粉末混合物的行为：(1)挤压比为5：1的2 mg-Fe热挤压(S-1)；(2)2 mg-Fe的热压(S-2)；(3)球磨2 mg-Fe+5%C的热压(S-3)。样品被活化，然后在15bar的条件下氢化，样品S-1作用24小时，样品S-2和S-3作用5小时。经过氢化处理后，在所有条件下都形成了络合氢化物。脱附温度随工艺条件的不同而变化，结果表明孔隙率是一个重要因素，因为碳的加入加速了脱附动力学。
Mg is a promising candidate material for hydrogen storage but its application is restricted by high sorption temperatures and slow sorption kinetics. Major efforts have focused on overcoming these two obstacles. Alloying, nanostructuring and/or catalysts, particularly at low temperatures, have considerably improved the hydrogenation kinetics of Mg powders. Further investigation is still desirable to reach the same properties for bulk materials because hydrogen desorption in bulk Mg-based systems still remains at a critical high temperature, and this, represents a major obstacle to their practical application. The aim of this work was to evaluate the reduction in desorption temperature and the increase in hydrogenation kinetics of bulk Mg-based composites in response to the following variables: particle/grain size, density of defects, the use of iron as catalyst, volume modifications, and the presence of carbon as a pore-confining element. We compared the behavior of 2Mg–Fe powder mixtures produced by high-energy ball milling processed as follows to produce bulk samples: (i) hot extrusion of 2Mg–Fe with extrusion ratio of 5/1 (S-1), (ii) hot compaction of 2Mg–Fe (S-2), and (iii) hot compaction of ball-milled 2Mg–Fe+5%C, all processed at 300°C (S-3). The samples were activated and subsequently hydrogenated at 15bar, sample S-1 for 24h and sample S-2 and S-3 for 5h. After the hydrogenation treatments, the complex hydride Mg2FeH6was formed in all the conditions. Desorption temperatures varied according to the processing conditions and the results indicated that porosity was an important factor, as it was the addition of carbon, which accelerated the desorption kinetics.