Effect of Nd on Subunits Structure and Electrochemical Properties of Super-Stacking PuNi3-Type La–Mg–Ni-Based Alloys
Effect of Nd on Subunits Structure and Electrochemical Properties of Super-Stacking PuNi3-Type La–Mg–Ni-Based Alloys
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DOI：
10.1149/2.0981510jes
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发表时间：
2015
影响因子：
3.9
通讯作者：
Lu Zhang;Shengbiao Cao;Yuan Li;Yumeng Zhao;Wenkai Du;Ding Yanqiao;Shumin Han
中科院分区：
文献类型：
--
作者：
Lu Zhang;Shengbiao Cao;Yuan Li;Yumeng Zhao;Wenkai Du;Ding Yanqiao;Shumin Han
采用感应熔炼后退火处理的方法制备了超堆垛PuNi 3型La0.67-xNdxMg0.33Ni3.0（x= 0，0.12）合金。铸态合金由PuNi 3型主相和CaCu 5-、MgCu 4Sn-、Ce 5Co 19-和Gd 2Co 7型副相组成。当退火温度从850 ℃升高到950 ℃时，少量相通过包埋反应逐渐转变为PuNi 3型相，形成PuNi 3型单相La0.67Mg0.33Ni3.0合金。Nd部分替代La增强了Gd 2 Co 7型相的相稳定性，导致退火处理后的La 0.55 Nd 0.12 Mg 0.33 Ni 3.0合金中存在Gd 2 Co 7型相和PuNi 3型主相作为第二相。结果表明，Nd主要取代PuNi 3型结构中[AB 5]片层中的La，增加了[A2 B 4]片层在晶胞中的体积比，减小了[A2 B 4]片层在氢化/脱氢过程中的体积变化，从而使合金100次循环稳定性从76.3%提高到80.3%。此外，由于Nd置换引起的晶胞体积收缩提高了合金电极的放电平台压力和电位，并且有助于在1200 mA g− 1放电电流密度下将高倍率放电能力（HRD）从55.7%提高到68.1%。
The super-stacking PuNi 3-type La 0.67-x Nd x Mg 0.33 Ni 3.0 (x= 0, 0.12) alloys have been prepared using induction melting followed by annealing treatment method. The alloys are composed of PuNi 3-type main phase and CaCu 5-, MgCu 4 Sn-, Ce 5 Co 19-and Gd 2 Co 7-type minor phases in as-cast alloy. As annealing temperature increases from 850 to 950 C, the minor phases gradually transform to the PuNi 3-type phase via peritectic reactions, forming PuNi 3-type single-phase La 0.67 Mg 0.33 Ni 3.0 alloy. Partial substitution of Nd for La has enhanced the phase stability of Gd 2 Co 7-type phase, resulting in the existence of Gd 2 Co 7-type phase as a secondary phase with the PuNi 3-type main phase in the La 0.55 Nd 0.12 Mg 0.33 Ni 3.0 alloy after annealing treatment. It is found that Nd mainly replace La in [AB 5] slabs in the PuNi 3-type structure, which increases the volume ratio of [A 2 B 4] slabs in the cell and decreases the volume change of [A 2 B 4] slabs during hydrogenation/dehydrogenation process, thus contributing to the improvement in cycling stability at the 100 th cycle of the alloy, from 76.3% to 80.3%. Moreover, the cell volume contraction due to Nd substitution heightens the discharge plateau pressure and potential of the alloy electrode, and helps to the enhancement in high rate dischargeability (HRD) from 55.7% to 68.1% at a 1200 mA g− 1 discharge current density.