M.Morinaga and H. Yukawa Department of Materials Science and Engineering
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Graduate School of Engineering
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Nagoya University
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Furo-cho
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Chikusa-ku
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Nagoya 464-8603
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Japan
金属学报(英文版)
The electronic structures are calculated by the DV-Xa molecular orbital method employing small model clusters in order to clarify the roles of the hydride forming elements, A, (e.g., La, Zr Ti, Mg) and non-forming elements, B, (e.g., Ni, Mn, Fe) in hydrogen storage alloys. It is confirmed from this calculation that hydrogen interacts more strongly with hydride non-forming elements, B, than hydride forming elements, A, in agreement with our previous calculations. However,the B-H interaction is enhanced only when some A element exists in the neighborhood. Otherwise, such a B-H interaction never operates in the alloy. In this sense,the coexistence of A and B elements are essential in the constitution of hydrogen storage alloys. Also, it is shown that the A/B compositional ratio of hydrogen storage alloys is understood in terms of a simple parameter, 2Bo(A - B) / /Bo(A - A)+ Bo(B-B)], where the Bo(A-B), Bo(A-A) and the Bo(B-B) are the bond strengths between atoms given in the parentheses.
关键词:
electronic structure
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null
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null
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null
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张国芳
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张羊换
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许剑轶
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胡锋
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张胤
稀有金属
doi:10.13373/j.cnki.cjrm.2014.06.016
采用球磨法制备Mg2Ni-Ni-xCeO2(x=0％,1％,3％,5％(质量分数))复合材料,系统研究了材料的结构、形貌、电化学及动力学储氢性能,从机制上分析了CeO2添加剂对Mg2Ni合金储氢性能的影响.X射线衍射(XRD)结果表明,随着CeO2添加量的增加及球磨时间的延长,复合材料中非晶纳米晶含量增大;扫描电镜(SEM)结果说明材料的颗粒细致,但存在一定程度的团聚现象;通过测试材料的电化学及动力学储氢性能可知,随着球磨时间的延长及CeO2含量的增大,复合材料的最大放电容量及循环稳定性得到显著提高;CeO2的添加优化了材料的高倍率放电性能,同时材料表面的电荷转移能力、交换电流密度以及极限电流密度也有明显提升.以上结果表明采用球磨法在Mg2Ni中添加CeO2能够有效提高材料的综合储氢性能,其原因在于CeO2可以促进合金的非晶化,从而提高合金的表面活性,同时CeO2特殊的敞开型晶体结构及Ce离子的易变价特性对提高材料的储氢动力学性能也起到了良好的催化作用.
关键词:
球磨法
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CeO2
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Mg2Ni
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复合材料
