LaNi_(5.5)Sn_(1.5)⁃C⁃Si合金优异的长期吸/放氢循环性能

Excellent Long⁃term Hydrogen Absorption/Desorption Cycling Property of LaNi_(5.5)Sn_(1.5)⁃C⁃Si Alloy

AB_(5)型储氢合金在气固储氢、氢压缩、镍氢电池等领域具有广阔的应用前景,其循环稳定性是人们的一个关注点。本实验通过电弧熔炼的冶金方法,结合长时间退火的热处理工艺,制备了以CaCu_(5)相为主相,以富Ni/Sn相为次要相,以及少量C相和Si相弥散分布的LaNi_(5.5)Sn_(1.5)⁃C⁃Si合金,并结合LaNi5基础合金,研究了LaNi_(5.5)Sn_(1.5)⁃C⁃Si合金在1000周吸/放氢循环过程中的储氢性能变化规律。结果表明,随着吸/放氢循环,合金的储氢容量略有降低,吸/放氢平台发生细微的倾斜,但以上变化远远小于LaNi_(5)合金循环1000周的变化。LaNi_(5.5)Sn_(1.5)⁃C⁃Si合金循环1000周的容量保持率高达98%,这可能是由于C和Si相的弥散分布对合金颗粒的粉化起到了缓冲作用。此外,LaNi_(5.5)Sn_(1.5)⁃C⁃Si合金具有良好的吸氢动力学性能,在383~423 K、2 MPa氢压下200 s内即可完全吸氢,合金良好的吸氢动力学性能可能与富Ni/Sn相的催化作用有关。

LaNi_(5)-based hydrogen storage alloys have wide application prospect in many areas such as gaseous hydrogen storage, hydrogen compressing, Ni/MH batteries etc. Their cycling stability has always been an important problem. In this study, LaNi_(5.5)Sn_(1.5)⁃C⁃Si alloy with CaCu_(5) main phase and a small amount of Ni/Sn phase, C phase and Si phase was prepared by arc melting metallurgical method combined with long time annealing treatment. The evaluation trend in the hydrogen storage performance of the LaNi_(5.5)Sn_(1.5)⁃C⁃Si alloy during 1 000 hydrogen absorption/desorption cycles are studied in comparison with LaNi5-base alloys. It is found that with increasing cycle number, the hydrogen storage capacity is slightly decreased, and the hydrogen absorption/desorption plateaus become a little tilted. However, the above changes are far less than that of LaNi5 alloys. LaNi_(5.5)Sn_(1.5)⁃C⁃Si alloy preserve a high cycling stability of reach 98% probably because of the buffering effect of the C and Si dispersion phases which relive the pulverization of the alloy particles. Moreover, the alloys have good kinetics performance and can fully absorb hydrogen within 200 s in the temperature range of 383-423 K at 2 MPa. The good hydrogen absorption kinetics may be related to the catalytic effect of the Ni/Sn-rich phase.