(Nd(1.5)Mg(0.5))Ni7-based compounds: structural and hydrogen storage properties.
(Nd(1.5)Mg(0.5))Ni7-based compounds: structural and hydrogen storage properties.
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DOI：
10.1021/ic2022962
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发表时间：
2012-02
影响因子：
4.6
通讯作者：
Qingan Zhang;Bin Zhao;M. Fang;Chaoren Liu;Qing-ping Hu;Fang Fang-Fang;Dalin Sun;L. Ouyang;Min Zhu
中科院分区：
文献类型：
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作者：
Qingan Zhang;Bin Zhao;M. Fang;Chaoren Liu;Qing-ping Hu;Fang Fang-Fang;Dalin Sun;L. Ouyang;Min Zhu
（Nd（1.5）Mg（0.5））Ni（7）基合金的结构和储氢性能（即，A（2）B（7）型），同时具有两种结构（六方2 H和菱方3R）。在2 H-和3R-型A（2）B（7）结构中，Mg原子占据Laves型AB（2）亚基的Nd位，而不是AB（5）亚基的Nd位，这是因为Mg取代AB（2）亚基中的Nd更显著地加强了系统中的离子键。A原子半径或B原子半径的增大使2 H结构稳定，但是A原子半径或B原子半径的减小有利于3R结构的形成。2 H-A（2）B（7）相和3R-A（2）B（7）相的吸放氢平衡压力非常相似，与平均亚基体积呈线性关系。（Nd（1.5）Mg（0.5））Ni（7）化合物的分解焓约为-29.4kJ/mol H（2），La部分取代Nd和Co/Cu部分取代Ni时，分解焓变大，Y部分取代Nd时，分解焓变小。
The structural and hydrogen storage properties of (Nd(1.5)Mg(0.5))Ni(7)-based alloys (i.e., A(2)B(7)-type) with a coexistence of two structures (hexagonal 2H and rhombohedral 3R) are investigated in this study. In both 2H- and 3R-type A(2)B(7) structures, Mg atoms occupy Nd sites of Laves-type AB(2) subunits rather than those of AB(5) subunits because Mg substitution for Nd in the AB(2) subunits more significantly strengthens the ionic bond in the system. An increase in the A-atomic radius or the B-atomic radius stabilizes the 2H structure, but a decrease in the A-atomic radius or the B-atomic radius is favorable for formation of the 3R structure. The 2H-A(2)B(7) and 3R-A(2)B(7) phases in each alloy have quite similar equilibrium pressures upon hydrogen absorption and desorption, which show a linear relationship with the average subunit volume. The hydriding enthalpy for the (Nd(1.5)Mg(0.5))Ni(7) compound is about -29.4 kJ/mol H(2) and becomes more negative with partial substitution of La for Nd and Co/Cu for Ni but less negative with partial substitution of Y for Nd.