退火处理对新型无镁Y0.7La0.3Ni3.25Al0.1Mn0.15储氢合金结构和电化学性能的影响

Effect of Annealing Treatment on Structure and Electrochemical Properties of New Mg-free Y0. 7La0. 3Ni3. 25Al0. 1Mn0. 15 Hydrogen Storage Alloys

通过电弧熔炼制备了无镁La⁃Y⁃Ni系A2B7型Y0.7La0.3Ni3.25Al0.1 Mn0.15合金,并在高纯0.2 MPa Ar气氛下分别对合金进行850~1050℃真空24h退火热处理.通过X射线衍射(XRD)、中子衍射(ND)、扫描电子显微镜/能量分散谱(SEM/EDS)和电化学测试方法研究了退火温度对合金结构和性能的影响.结构分析表明,铸态合金由CaCu5,Ce5Co19,Gd2Co7,Ce2Ni7多相构成,随着退火温度升高,CaCu5,Ce5Co19,Gd2Co7相逐步减少直至消失,Ce2Ni7主相相丰度逐步增加.900~950℃退火时,合金为单相Ce2Ni7结构.退火温度继续升高,合金中出现少量PuNi3相.合金电极的最大放电容量随着退火温度的升高先增加后降低.从铸态的307.6 mA·h/g增加到900℃退火时的最大值393.1 mA·h/g,后又降到1050℃退火时的366.4 mA·h/g.合金电极的电化学循环稳定性随退火温度的升高而升高,循环100次后电化学容量保持率(S100)从铸态的66%上升到1050℃退火后的88.5%,900~950℃退火时,合金电极具有较好的综合电化学性能.

Mg-free A2B7 type Y0.7La0.3Ni3.25Al0.1Mn0.15 alloy of La-Y-Ni system was prepared by arc melting and annealed for 24h in high purity Ar atmosphere at 800—1050℃.X-ray diffraction(XRD),neutron diffraction(ND),scanning electron microscopy and energy dispersive spectroscopy(SEM/EDS)and electrochemical test methods were used to research the influence of annealing temperature on the structure and properties of the alloys.Structural analysis shows that as-cast alloy consists of CaCu5,Ce5Co19,Gd2Co7 and Ce2Ni7.As the annealing temperature increases,CaCu5,Ce5Co19 and Gd2Co7 gradually decrease to disappear,while the phase abundance of Ce2Ni7 main phase increases gradually.When annealing at 900—950℃,the alloy is single-phase Ce2Ni7 structure.When annealing temperature continues to rise,a small amount of PuNi3 phase appears in the alloy.The maximum discharge capacity of the alloy electrodes increases first and then decreases as the annealing temperature increases.It increases from 307.6 mA·h/g for the as-cast alloy to 393.1 mA·h/g at the nnealing temperature of 900℃,and then decreases to 366.4 mA·h/g at the nnealing temperature of 1050℃.The electrochemical cycle stability of alloy electrodes increase with the increase of annealing temperature.After 100 cycles,the electrochemical capacity retention rate(S100)increases from 66%for the as-cast alloys to 88.5%at the nnealing temperature of 1050℃.When annealing at 900-950℃,the alloy electrodes have better comprehensive electrochemical properties.