LaMgNi4-xCox合金的制备及储氢性能

采用悬浮熔炼加烧结的方法制备LaMgNi4?xCox(x=0,0.3,0.5)化合物。XRD的测试结果表明，所制得的LaMgNi4?xCox (x=0,0.3,0.5)均为单相，其结构为SnMgCu4(AuBe5型)。利用PCI 对LaMgNi4在不同温度下的吸放氢性能进行测试，结果表明在373 K、4.3 MPa氢气的条件下吸氢量达到最大(1.45%)，在吸氢过程中发生了由立方结构的α-LaMgNi4到正交结构的β-LaMgNi4H3.41再到立方结构的γ-LaMgNi4H4.87的变化，而放氢过程中只能观测到部分氢气放出。随着温度的升高，合金的吸氢量有所降低，同时吸氢平台的数量由2个变为1个，但吸氢动力学性能得到提高。采用模拟电池实验测试了LaMgNi4?xCox (x=0,0.3,0.5)的电化学性能，结果表明合金的最大放电容量随着Co含量的增加而增大。

Preparation of LaMgNi4-xCox alloys and hydrogen storage properties

The LaMgNi_4-xCo_x (x=0, 0.3, 0.5) compounds were prepared by the method of levitation melting and a subsequent heat treatment at 1073 K for 10 h. XRD analysis shows that the obtained LaMgNi_4-xCo_x alloys consist of a single phase with the structure of cubic SnMgCu₄ (AuBe₅ type). The hydrogen absorption/desorption properties of LaMgNi₄ were investigated by PCI measurement at various temperatures (T=373, 398, 423 K) and the results show that the maximum absorbed hydrogen capacity reaches 1.45% (5.79H/M) under a hydrogen pressure of 4.3 MPa at 373 K. The XRD patterns during absorbing procedure at 373 K indicate the phase structure changing from cubic (α-LaMgNi₄) to orthorhombic (β-LaMgNi₄H_3.41) and after hydrogenation finally back to cubic (γ-LaMgNi₄H_4.87), and a partial desorption was also observed under this condition. With increasing temperature, a slight decrease of the absorbed hydrogen content was observed and the number of plateaus reduces from two to one, but the hydrogen absorption kinetics improves. The electrochemical properties of the LaMgNi_4-xCo_x were measured by simulated battery test, which shows that the discharge capacity of the alloys significantly improves with the increase of Co content.