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本文系统地研究了LaNi_3-H_2体系的吸放氢特性,并通过X射线衍射相分析及差热分析对LaNi_3在加热脱氢过程中发生的相变及相分解机理进行了研究。LaNi_3在室温下氢化后变成微晶氢化物,该氢化物在350℃以上放氢时则分解成LaNi_5和LaH_3,其相分解模型为:在分解过程形成中间相LaNi_2。该中间相随反复的加热而消失。氢致分解的最终结果是:LaNi_3-H_2体系的特性归结为LaNi_5-H_2体系的特性;P-C等温线随加热由两个平台变成一个平台。 从晶体结构和化合物的热力学稳定性等方面对LaNi_3的氢致分解机理进行了讨论,同时对P-C等温线出现的两个平台以及第二个平台消失的原因进行了分析。
In this paper, the hydrogen absorption and desorption characteristics of LaNi_3-H_2 system were systematically studied. The phase transformation and phase decomposition mechanism of LaNi_3 in the process of thermal dehydrogenation were studied by X-ray diffraction and differential thermal analysis. LaNi_3 becomes hydrogenated at room temperature and then becomes a microcrystalline hydride. The hydride decomposes into LaNi_5 and LaH_3 when desorbed at above 350 ° C. The phase decomposition model of LaNi_3 is as follows: LaNi_2 is formed during decomposition. The mesophase vanishes with repeated heating. The final result of hydrogen-induced decomposition is that the properties of LaNi_3-H_2 system are attributed to the characteristics of LaNi_5-H_2 system. The P-C isotherm changes from two platforms to one platform with heating. The mechanism of hydrogen decomposition of LaNi_3 was discussed in terms of the crystal structure and the thermodynamic stability of the compounds. The reasons why two P-C isotherms appeared and the disappearance of the second platform were also analyzed.