铸态及快淬态La-Mg-Ni系(PuNi_3型)贮氢合金的循环稳定性

Cycling stability of La-Mg-Ni system (PuNi_3-type) hydrogen storage alloys prepared by casting and rapid quenching

用铸造及快淬工艺制备了LaMgNi系(PuNi3型)La2Mg(Ni0.85Co0.15)9Bx(x=0～0.2)贮氢合金,分析测试了铸态及快淬态合金的微观结构与循环稳定性,研究了硼及快淬工艺对合金微观结构及电化学循环稳定性的影响。结果表明,铸态合金具有多相结构,包括(La,Mg)Ni3相和LaNi5相,一定量的LaNi2相及微量的Ni2B相,经大于15m/s淬速快淬处理后Ni2B相消失,并且其它相的相对量随淬速的变化而变化。硼的加入提高了铸态及快淬态合金的循环稳定性,但其作用机理完全不同。合金的循环寿命随淬速的增加而增加,但快淬工艺对LaMgNi系贮氢合金循环寿命的改善非常有限。

The La-Mg-Ni system (PuNi_3-type) hydrogen storage alloys La_2Mg(Ni_~0.85 Co_~0.15 )_9B_x (x = 0, 0.1, 0.2) were prepared by casting and rapid quenching. The microstructures and electrochemical cycling stabilities of the as-cast and quenched alloys were determined and measured. The effects of boron content and quenching rate on the microstructures and electrochemical cycling stabilities of the alloys were investigated. The results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni_3 phase (PuNi_3-type structure), the LaNi_5 phase and the LaNi_2 phase. A trace of the Ni_2B phase exists in the as-cast alloys containing boron, and after the as-cast alloys are quenched when quenching rate is more than 15m/s, the Ni_2B phase in the alloys nearly disappears. The relative amount of each phase in the alloys changes with the variety of the quenching rate. The addition of boron enhances the cycle stability of the as-cast and quenched alloys, but the mechanism is completely different. The cycle lives of the as-quenched alloys increase with the increasing quenching rate, but the improvement of the rapid quenching treatment on the cycling stability of La-Mg-Ni system hydrogen storage alloys is very limited.