熔体快淬对纳米晶和非晶Mg2Ni型合金贮氢动力学性能的影响

摘要

The Mg2Ni-type alloys with nominal compositions of Mg2Ni1-xCox (x=0,0.1,0.2,0. 3, 0.4) are fabricated by melt-spinning technique. The as-spun alloy ribbons, which have a continuous length, a thickness of about 30μm and a width of about 25mm, are obtained. The structures of the as-spun alloy ribbons are characterized by XRD and TEM. The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloy ribbons are tested by an automatic galvanostatic system. The electrochemical impedance spectrums (EIS) and the Tafel polarization curves are plotted by an electrochemical workstation. The hydrogen diffusion coefficients in the alloys are calculated by virtue of potential-step method. The results show that the as-spun alloys have nanocrystalline/amorphous structure, and the amorphization degree of the alloys visibly increases with rising spinning rate. Furthermore, the melt spinning treatment significantly improves the hydrogen storage kinetics of the alloys. As the spinning rate increases from 0 (As-cast is defined as the spinning rate of Om/s) 30m/s, the hydrogen absorption saturation ratio (Ra5) of the (x=0.3) alloy increases from 81.9％ to 94.7％, the hydrogen desorption ratio (Ra20) from 34.9％ to 57.3％, the hydrogen diffusion coefficient (D) from 7.24× 10-12 to 3.66 × 10-11cm2/s and the limiting current density (IL) from 121.7 to 811. 63mA/g, respectively.%用快淬技术制备了名义成分为Mg2Ni1-xCox(x=0、、0.1、0.2、0.3、0.4)的贮氢合金.获得长度连续,厚度约为30μm,宽度约为25mm的快淬合金薄带.用XRD、HRTEM表征了快淬态合金薄带的微观结构,用自动控制的Sieverts设备测试了合金的吸放氢动力学性能.用程控电池测试仪测定了合金薄带的电化学贮氢动力学.用电化学工作站测试了快淬薄带的交流阻抗谱(EIS)和Tafel极化曲线,测试了电位阶跃后的阳极电流与时间相应曲线,并计算了氢在合金中的扩散系数(D).结果表明,快淬态合金具有纳米晶/非晶结构,且非晶化程度随淬速的增加而增加.此外,快淬处理显著地提高舍金的贮氢动力学,当淬速从0m/s(铸态被定义为淬速0m/s)增加到30m/s时,快淬态(x=0.3)合金在5min内的吸氢饱和率(Ra5)从81.9%增加到94.7%,20min的放氢率(Ra20)从34.9%增加到57.3%,氢扩散系数(D)从7.24×1012cm2/s增加到3.66×10-11cm2/s,极限电流密度(IL)从121.7mA/g增加到880.7mA/g.