La替代Mg对Mg2Ni型合金电化学贮氢性能的影响

用快淬工艺制备了纳米晶和非晶Mg2Ni型Mg2 -xLaxNi (x=0,0.2,0.4,0.6)贮氢电极合金,获得长度连续,厚度约为30μm,宽度约为25 mm的薄带.用XRD、SEM和HRTEM分析了快淬合金薄带的微观结构,测试了合金薄带的电化学性能及电化学交流阻抗谱(EIS).快淬无La合金具有典型的纳米晶结构,...

Influence of Substituting Mg with La on Electrochemical Hydrogen Storage Properties of Mg_2Ni-type Alloys

The rapid quenching technique is applied to the preparation of the nanocrystalline and amorphous Mg2Ni-type alloys with nominal compositions of Mg2-xLaxNi（x=0,0.2,0.4,0.6）.The as-quenched alloy ribbons with a continuous length,a thickness of about 30 μm and a width of about 25 mm were successfully obtained.The structures of the as-spun alloy ribbons were characterized by XRD,SEM and HRTEM.The electrochemical hydrogen storage performances and the electrochemical impedance spectra（EIS） of the as-quenched alloy ribbons were tested.The results show that the as-quenched La-free alloy holds a typical nanocrystalline structure,whereas the as-quenched alloys substituted by La exhibit an evident amorphous structure,meaning the substitution of La for Mg facilitates the glass formation of the Mg2Ni-type alloy.For x≤0.2,the substitution of La for Mg leads to forming small amount of secondary phases LaMg3 and La2Mg17 without changing major phase Mg2Ni.The major phase of the alloys are changed into the（La,Mg）Ni3＋LaMg3 phases by increasing La content to x≥0.4.The discharge capacity of the as-cast alloy always increases with rising amount of La substitution,whereas the discharge capacity of the as-quenched alloy has a maximum value with the incremental variation of La content.Furthermore,the substitution of La for Mg significantly enhances the cycle stability of the as-cast and quenching alloys.