材料期刊网

为了改善Mg2Ni型合金的电化学贮氢性能,用La部分替代Mg,并用铸造及快淬工艺制备了Mg2-xLaxNi（x=0、0.2、0.4、0.6）电极合金,获得长度连续,厚度约为30μm,宽度约为25mm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、电化学交流阻抗谱（EIS）及氢在合金中的扩散系数（D）。结果发现,在快淬无La合金中没有出现非晶相,但快淬La替代合金显示了以非晶相为主的结构,表明La替代Mg提高了合金的非晶形成能力。当x≤0.2时,La替代Mg不改变合金的Mg2Ni型主相,但出现少量的LaMg3及La2Mg17相。La替代及快淬明显改善合金的电化学贮氢性能。其中,Mg2La0.2Ni合金具有最佳的综合电化学性能。当淬速从0m/s（铸态被定义为淬速0m/s）增加到30m/s时,Mg2La0.2Ni合金的放电容量从197.2mAh/g增加到406.5mAh/g,20次充放循环后的容量保持率从52.7%增加到81.4%,高倍率放电能力从48.3%增加到56.8%,氢扩散系数（D）从8.12×10-12cm2/s增加到1.80×10-11cm2/s。

In order to improve the electrochemical hydrogen storage properties of the Mg2Ni-type alloys,Mg in the alloy was partially substituted by element La,and melt-spinning technology was used for the preparation of the Mg2-xLaxNi（x=0,0.2,0.4,0.6） alloys.The as-spun alloy ribbons with a continuous length,a thickness of about 30μm and a width of about 25mm 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） as well as the hydrogen diffusion coefficients of the as-spun alloy ribbons were tested.It was found that the as-spun La-free alloy holds a typical nanocrystalline structure,whereas the as-spun alloys substituted by La exhibit an evident amorphous structure,suggesting 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,instead of changing major phase Mg2Ni,leads to forming small amount of secondary phases LaMg3 and La2Mg17.Both the La substitution and the melt spinning evidently ameliorate the electrochemical hydrogen storage properties of the alloy.Among of all the alloys,the as-spun Mg2La0.2Ni alloy possesses the superior electrochemical hydrogen storage properties.As the spinning rate is enhanced form 0 m/s（as-cast is defined the spinning rate of 0m/s） to 30m/s,the discharge capacity of the Mg2La0.2Ni alloy increases form 197.2 to 406.5mAh/g,the capacity retaining rate at 20th cycle rises from 52.7% to 81.4%,high rate discharge ability grows from 48.3% to 56.8%,and hydrogen diffusion coefficient（D） augments from 8.12×10-12 to 1.80×10-11cm2/s.