La0.7Mg0.3Ni2.55-xCo0.45Alx(x=0～0.4)贮氢合金的循环稳定性

为了提高La-Mg-Ni系贮氢合金的循环稳定性,以Al部分替代Ni,采铸造及快淬工艺制备了La0.7Mg0.3Ni2.55-xCo0.45Alx(x=0,0.1,0.2,0.3,0.4)电极合金,研究了Al替代量及快淬工艺对合金微观结构及电化学循环稳定性的影响。X射线衍射分析结果表明:铸态及快淬态合金具有多相结构,包括(La,Mg)Ni3相、LaNi5相和一定量的LaNi2相;Al替代使铸态合金中LaNi2相的量显著增加,但对快淬态合金中LaNi2相的相丰度影响不显著。电化学测试结果表明:随Al替代量的增加,合金的循环寿命大幅度提高;快淬处理可以提高合金的循环寿命,但随Al替代量的增加,淬速对循环寿命的影响减小。

Cycling stability of La0.7Mg0.3Ni2.55-xCo0.45Alx (x=0-0.4) hydrogen storage alloys

In order to improve the cycle stability of La-Mg-Ni system(PuNi_3-type) hydrogen storage alloy,Ni in the alloy was partly substituted by Al,and La_(0.7)Mg_(0.3)Ni_(2.55-x)Co_(0.45)Al_x(x=0,0.1,0.2,0.3,0.4) hydrogen storage alloys were prepared by casting and rapid quenching.The effects of substituting Ni with Al and rapid quenching on the microstructures and cycle stability of the alloys were investigated.The results obtained by XRD show that the as-cast and quenched alloys have a multiphase structure,including the(La,Mg)Ni_3 phase,LaNi_5 phase and LaNi_2 phase.The substitution of Al for Ni increases the amount of LaNi_2 phase in the as-cast alloys,but it has an inappreciable influence on the abundance of the LaNi_2 phase in the as-quenched alloy.The results obtained by the electrochemical measurement indicate that the cycle stability of the as-cast and quenched alloys significantly increases with the increase of Al content.Rapid quenching can improve the cycle stability of the alloys,but the influence of the quenching rate on the cycle stability of the alloy gradually decreases with the increase of the Al content.