具有超点阵结构的R-Mg-Ni化合物储氢机理及其影响因素

To solve some key scientific problems of R-Mg-Ni hydrogen storage alloys, a research project for the study on hydrogen storage mechanism and its influencing factors of the R-Mg-Ni compounds with superlattice structures is proposed on the basis of our previous investigations. The site occupations of hydrogen atoms in new hydrides will be studied to reveal their hydrogen storage mechanisms. Then a comparative investigation on the hydrogen absorption-desorption characteristics and mechanism between 2H and 3R phases will be made to find the correlation between superlattice structures and hydrogen storage properties. In order to clarify the influencing factors of hydrogen storage properties, in the meantime, the lattice expansions and strains of the R-Mg-Ni compounds in the hydrogen absorption process will be researched in detail. Furthermore, the effects of alloying on the solid solubility of Mg and hydrogen storage properties of the R-Mg-Ni compounds will also studied to explore the reasons for the roles of various elements. All the investigations in this project can provide us new information on the understanding of the essence and mechanism of the interaction between the intermetallic compound with superlattice structure and hydrogen, offering a theoretical foundation for the researches and developments of novel hydrogen storage alloys.

针对R-Mg-Ni系储氢合金存在的关键科学问题，结合申请人的前期工作积累，本项目提出研究具有超点阵结构的R-Mg-Ni化合物储氢机理及其影响因素这一课题。拟研究新型氢化物中氢原子占位，揭示新型结构的储氢机理；探索2H相和3R相吸放氢特性和储氢机理的异同点，发现超点阵结构和储氢性能之间的内在联系；研究R-Mg-Ni化合物在吸氢过程中晶格膨胀和点阵应变的变化规律，掌握影响其储氢性能和机理的因素；研究合金化对R-Mg-Ni化合物中Mg的固溶度和储氢性能影响规律，发现各种合金元素对其储氢性能的影响机制。通过这些研究工作，查明复杂结构金属间化合物与氢相互作用的本质，为高性能新型储氢合金的研究和探索提供理论依据。

为了解决R-Mg-Ni系储氢合金存在的关键科学问题，本项目详细研究了具有超点阵结构的R-Mg-Ni化合物储氢机理及其影响因素。研究了新型氢化物Ca3Mg2Ni13H15.6的晶体结构及其放氢机理，发现氢原子不仅占据[CaNi5]和[CaMgNi4]亚单元而且占据亚单元之间界面的间隙位置，放氢时亚单元之间界面上氢原子首先释放出来，随后[CaNi5]和[CaMgNi4]亚单元中的氢原子同时释放，最后仍有少量氢原子残留在[CaNi5]亚单元中。探索了2H相和3R相吸放氢特性和储氢机理，发现2H相和3R相吸放氢的热力学几乎相同，吸放氢性能主要与化合物中间隙大小有关。研究了R-Mg-Ni化合物在吸氢过程中晶格膨胀和点阵应变的变化规律，发现在吸放氢过程中，当氢的固溶体相和氢化物相共存时点阵应变达到最大值，吸放氢后三元化合物中的残余应变和晶格膨胀比二元化合物R-Ni小的多。同时，通过研究合金化对R-Mg-Ni化合物中Mg的固溶度和储氢性能影响规律，发现A侧替代对R-Mg-Ni化合物中Mg的固溶度影响不大、但会导致化合物中间隙大小发生变化，B侧替代则会降低化合物中Mg的固溶度，从而储氢性能也发生相应的变化。此外，还研究了[AB5]/[AB2]单元比例对吸放氢性能的影响，发现随着AB5/AB2单元比的增大，吸放氢平衡压力降低、循环稳定性提高。通过这些研究工作，查明了复杂结构金属间化合物与氢相互作用的本质，为高性能新型储氢合金的研究和探索提供了理论依据。