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RE（RE=Nd,Sm,Pr）部分替代La对A2B7型合金电化学贮氢性能的影响

ISSN号：0258-7076
期刊名称：《稀有金属》
时间：0
分类：TG146.4[金属学及工艺—金属材料;一般工业技术—材料科学与工程;金属学及工艺—金属学]
作者机构：[1]内蒙古科技大学内蒙古自治区白云鄂博矿多金属资源综合利用重点实验室,内蒙古包头014010, [2]钢铁研究总院功能材料研究所,北京100081, [3]北京科技大学材料科学与工程学院,北京100083
相关基金：国家自然科学基金项目（51161015,51371094）; 内蒙古自治区自然科学基金重大项目（2011ZD10）资助

作者：张羊换[1,2], 杨泰[2], 吴征洋, 袁泽明[2], 郭世海[2], 赵栋梁[2]

关键词： A2B7型电极合金, RE替代La, 微观结构, 电化学性能, A2B7-type electrode alloy, substituting RE for La, microstructure, electrochemical performances

中文摘要：

La-Mg-Ni系A2B7型合金由于其高的放电容量被认为是最具希望的Ni-MH电池负极材料,然而,低的电化学循环稳定性制约着合金的实际应用。为了改善La-Mg-Ni系A2B7型合金的电化学贮氢性能,用RE（RE=Nd,Sm,Pr）部分替代合金中的La,用感应熔炼及退火工艺制备了La0.8-xRExMg0.2Ni3.35Al0.1Si0.05（RE=Nd,Sm,Pr;x=0,0.2）电极合金。为了抑制Mg在熔炼过程中的挥发,熔炼过程中采用氦气作为保护气氛。用X射线衍射（XRD）和扫描电镜（SEM）分析了铸态及退火态合金的微观结构,并测试了铸态及退火态合金的电化学贮氢性能,比较了不同稀土元素替代La对合金电化学性能的影响。结果表明,铸态及退火态合金包含两个主相,具有Ce2Ni7型结构的（La,Mg）2Ni7相以及Ca Cu5型结构的La Ni5相。RE（RE=Nd,Sm,Pr）部分替代La未影响合金的相组成,但使合金的相含量发生明显改变。此外,元素替代使铸态及退火态合金的组织明显细化。RE（RE=Nd,Sm,Pr）部分替代La显著改善了合金的电化学贮氢性能,包括电化学循环稳定性、放电容量及电化学动力学性能。

英文摘要：

La-Mg-Ni-based A2B7-type hydrogen storage alloys are considered as the most promising cathode materials for Ni-MH secondary batteries because of their great discharge capacity. However,the poor cycle stability makes them still far from practical applications. The partial substitution of RE（ RE = Nd,Sm,Pr） for La was performed in order to improve the electrochemical performances of RE-Mg-Ni-based A2B7-type electrode alloys. The La0. 8- xRExMg0. 2Ni3. 35Al0. 1Si0. 05（ RE = Nd,Sm,Pr; x = 0,0. 2） electrode alloys were fabricated by induction melting and annealing and their microstructures were characterized by X-ray diffraction（ XRD） and scanning electron microscope（ SEM）. The melting was performed in helium atmosphere for the sake of preventing the volatilization of Mg.The electrochemical hydrogen storage performances of as-cast and annealed alloys were measured and the effects of the replacement of La by different rare earth elements on electrochemical performances of the alloys were investigated systemically. The results revealed that all of the experimental alloys consisted of two major phases：（ La,Mg）2Ni7with hexagonal Ce2Ni7-type structure and LaN i5 with hexagonal CaC u5-type structure. The partial substitution of RE（ RE = Sm,Nd,Pr） for La significantly changed the phase abundances of the alloys while had few effect on their phase composition. Furthermore,such substitution brought about a visible refinement of the grains of as-cast and annealed alloys. The substitution of RE（ RE = Sm,Nd,Pr） for La considerably improved the synthetic electrochemical performances of all the experimental alloys,including the electrochemical cycle stability,discharge capacity and electrochemical kinetics.