采用中间合金法在感应熔炼炉中制备La4MgNi19-xCox（x=02）合金,研究Co部分替代Ni对合金相结构和电化学性能的影响。XRD测试结果表明:合金主要由La4MgNi19(Ce5Co19+Pr5Co19)相和LaNi5相组成;x的增加有利于促进La4MgNi19相的形成,且晶胞...采用中间合金法在感应熔炼炉中制备La4MgNi19-xCox（x=02）合金,研究Co部分替代Ni对合金相结构和电化学性能的影响。XRD测试结果表明:合金主要由La4MgNi19(Ce5Co19+Pr5Co19)相和LaNi5相组成;x的增加有利于促进La4MgNi19相的形成,且晶胞体积随之增大。显微组织观察发现,合金为树枝晶结构,x的增加会使树枝晶变细。电化学测试表明:合金均具有良好的活化性能和高倍率放电性能(HRD600>92.57%);随着x的增加,合金的最大放电容量明显提高（从x=0时的359.23 m A·h/g增大到x=2的380.85 m A·h/g）,而循环寿命则先下降后逐渐提升。高倍率放电性能主要由合金电极的扩散系数控制,而循环稳定性的下降则是由于合金中La4MgNi19相的增加使膨胀率和晶间应力集中增大加速粉化所致。展开更多
The effects of the alloy preparation methods, including the conventional casting, annealing and melt-spinning, on the crystallographic and electrochemical properties of the Co-free LaNi4.95Sn0.3 alloy samples were inv...The effects of the alloy preparation methods, including the conventional casting, annealing and melt-spinning, on the crystallographic and electrochemical properties of the Co-free LaNi4.95Sn0.3 alloy samples were investigated. The results reveal that the as-cast alloy consists of a main phase of CaCu5-type structure and a little second phase (Sn) with noticeable composition segregation and rather poor cycling stability (S200=40.1%). While the annealed and melt-spun alloys are of single CaCu5-type structure phase with a more homogeneous composition and lower cell volume expansion rate (?V/V) on hydriding, and a dramatically improved cyclic stability (S200=73.6%?76.2%), although their activation rate, initial capacity and high-rate dischargeability are lowered somewhat. It is found that the decrease in both the electrocatalytic activity and the hydrogen diffusion rate of the annealed and melt-spun alloys is the main cause for their relatively lower high-rate dischargeability, and the improved cycling stability is due to their lower volume expansion on hydriding and more uniform composition.展开更多
La（1-x）MgxNi（1.75）Co（2.05）（x=0.07, 0.08, 0.10, 0.13, 0.15） alloys were prepared by high-frequency inductive method, and then their structure and electrochemical properties were investigated systematically. The...La（1-x）MgxNi（1.75）Co（2.05）（x=0.07, 0.08, 0.10, 0.13, 0.15） alloys were prepared by high-frequency inductive method, and then their structure and electrochemical properties were investigated systematically. The XRD analysis revealed that the alloys consisted of LaNi5 phase and La4MgNi（19）（Ce5Co（19） ＋ Pr5Co（19）） phase, and the introduction of Mg could promote the formation of La4MgNi（19） phase. The observation of microstructure showed that all the alloys processed dendritic structure, which was refined with the increase of x value. The electrochemical measurements showed that all the alloys could be activated within 2 cycles, and with increasing x, the maximum discharge capacity obviously increased from 254.00 m Ah/g（x=0.07） to 351.51 mAh/g（x=0.15）, but the cycling stability（S（80）） decreased somehow from 78.4% to 73.9%. Meanwhile, the appropriate addition of Mg could improve the high-rate discharge capacity（HRD） of the alloy electrodes, which was mainly controlled by the electrochemical reaction rate on the surface of the alloys.展开更多
文摘采用中间合金法在感应熔炼炉中制备La4MgNi19-xCox（x=02）合金,研究Co部分替代Ni对合金相结构和电化学性能的影响。XRD测试结果表明:合金主要由La4MgNi19(Ce5Co19+Pr5Co19)相和LaNi5相组成;x的增加有利于促进La4MgNi19相的形成,且晶胞体积随之增大。显微组织观察发现,合金为树枝晶结构,x的增加会使树枝晶变细。电化学测试表明:合金均具有良好的活化性能和高倍率放电性能(HRD600>92.57%);随着x的增加,合金的最大放电容量明显提高（从x=0时的359.23 m A·h/g增大到x=2的380.85 m A·h/g）,而循环寿命则先下降后逐渐提升。高倍率放电性能主要由合金电极的扩散系数控制,而循环稳定性的下降则是由于合金中La4MgNi19相的增加使膨胀率和晶间应力集中增大加速粉化所致。
基金Project (2008CL068L) supported by the Natural Science Research Project of Higher Education of Jiangsu Province, ChinaProject (50901036) supported by the National Natural Science Foundation of China
基金Project(50131040) supported by the National Natural Science Foundation of China
文摘The effects of the alloy preparation methods, including the conventional casting, annealing and melt-spinning, on the crystallographic and electrochemical properties of the Co-free LaNi4.95Sn0.3 alloy samples were investigated. The results reveal that the as-cast alloy consists of a main phase of CaCu5-type structure and a little second phase (Sn) with noticeable composition segregation and rather poor cycling stability (S200=40.1%). While the annealed and melt-spun alloys are of single CaCu5-type structure phase with a more homogeneous composition and lower cell volume expansion rate (?V/V) on hydriding, and a dramatically improved cyclic stability (S200=73.6%?76.2%), although their activation rate, initial capacity and high-rate dischargeability are lowered somewhat. It is found that the decrease in both the electrocatalytic activity and the hydrogen diffusion rate of the annealed and melt-spun alloys is the main cause for their relatively lower high-rate dischargeability, and the improved cycling stability is due to their lower volume expansion on hydriding and more uniform composition.
基金Project supported by the National Natural Science Foundation of China(50901036)the Graduate Science and Technology Innovation Project of Jiangsu University of Science and Technology(YCX15S-18)Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘La（1-x）MgxNi（1.75）Co（2.05）（x=0.07, 0.08, 0.10, 0.13, 0.15） alloys were prepared by high-frequency inductive method, and then their structure and electrochemical properties were investigated systematically. The XRD analysis revealed that the alloys consisted of LaNi5 phase and La4MgNi（19）（Ce5Co（19） ＋ Pr5Co（19）） phase, and the introduction of Mg could promote the formation of La4MgNi（19） phase. The observation of microstructure showed that all the alloys processed dendritic structure, which was refined with the increase of x value. The electrochemical measurements showed that all the alloys could be activated within 2 cycles, and with increasing x, the maximum discharge capacity obviously increased from 254.00 m Ah/g（x=0.07） to 351.51 mAh/g（x=0.15）, but the cycling stability（S（80）） decreased somehow from 78.4% to 73.9%. Meanwhile, the appropriate addition of Mg could improve the high-rate discharge capacity（HRD） of the alloy electrodes, which was mainly controlled by the electrochemical reaction rate on the surface of the alloys.
