用快淬工艺制备了Mg2Ni型合金,其名义成分为Mg2Ni1-xCox(x=0,0.1,0.2,0.3,04).以XRD、SEM、TEM分析了铸态及快淬合金的结构.用程控模拟电池测试仪测试了合金的电化学贮氢动力学.用电位跃迁法计算了氢在合金中的扩散系数.用电化学工作站测试了合金的电化学交流阻抗谱(EIS)和Tafel极化曲线.结果表明,快淬态无Co合金具有典型的纳米晶结构,而Co含量为0.4的快淬态合金具有纳米晶/非晶结构,表明Co替代Ni可以提高Mg2Ni型合金的非晶形成能力,且快淬态合金的非晶化程度随Co替代量的增加而增加.Co替代Ni显著地提高了合金电化学贮氢动力学.当Co含量从0增加到04时,淬速为25 m/s的快淬态合金的高倍率放电能力(HRD)从65.3％增加到75.3％,氢扩撒系数(D)从2.22 cm2/s增加到3.34 cm2/s,极限电流密度(IL)从247.8 mA/g增加到712.4 mA/g.
The Mg2Ni-type Mg2Ni1-xCox (x=0,0.1,0.2,0.3,0.4) alloys were prepared by melt-spinning technique.The structures of the as-cast and spun alloys were characterized by XRD,SEM and TEM.The electrochemical hydrogen storage kinetics of the as-spun alloy ribbons was tested by an automatic galvanostatic system.The hydrogen diffusion coefficients in the alloys were calculated by virtue of potential-step method.The electrochemical impedance spectrums (EIS) and the Tafel polarization curves were plotted by an electrochemical workstation.The results show that the as-spun Co-free alloy exhibits a typical nanocrystalline structure,while the as-spun (x=0.4) alloy displays a nanocrystalline and amorphous structure,confirming that the substitution of Co for Ni facilitates the glass formation in the Mg2Ni-type alloy.The amorphization degree of the as-spun alloys substituted by Co visibly increases with the increase in the amount of Co replacement.The Co replacement for Ni notably improves the electrochemical hydrogen storage kinetics of the alloys.With a growth in the amount of Co replacement from 0 to 0.4,the high rate discharge ability of the as-spun (25 m/s) alloy increases from 65.3％ to 75.3％,the hydrogen diffusion coefficient (D) from 2.22 to 3.34 cm2/s and the limiting current density IL from 247.8 to 712.4 mA/g,respectively.
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