La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） hydrogen storage alloys were prepared by induction melting and effect of Al substitution for Ni on phase constitution and electrochemical property was investigated.With the s...La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） hydrogen storage alloys were prepared by induction melting and effect of Al substitution for Ni on phase constitution and electrochemical property was investigated.With the substitution of Al for Ni,LaNi5 and LaNi2 phases occurred and （La,Mg）2（Ni,Co,Al）7 phase with hexagonal Ce2Ni7-type structure replaced （La,Mg）2（Ni,Co）7 phase.The cell volumes of LaNi5 and （La,Mg）2（Ni,Co,Al）7 main phases increased with increasing Al content.Some electrochemical properties and kinetic parameters of the alloys,including discharge capacity,high rate discharge ability （HRD）,loss angle （ψ）,exchange current density （I0） and limiting current density （IL）,decreased with increasing amount of substitution of Al for Ni.Substitution of Al for Ni could be favorable for positive shift in corrosion potential of the alloy electrode,and prolonged cyclic lifetime of La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） alloy electrodes.展开更多
In order to investigate the effect of substituting La with Pr on structural and hydrogen storage properties of La-Mg-Ni system （AB3.5-type） hydrogen storage alloys, a series of La0.65-xPrxNd0.12Mg0.23Ni3.4Al0.1（x=0...In order to investigate the effect of substituting La with Pr on structural and hydrogen storage properties of La-Mg-Ni system （AB3.5-type） hydrogen storage alloys, a series of La0.65-xPrxNd0.12Mg0.23Ni3.4Al0.1（x=0, 0.10, 0.15, 0.2） hydrogen storage alloys were prepared. X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy dispersive spectrometer （EDS） analyses revealed that two alloys （x=0.0 and 0.10） were composed of （La,Mg）2（Ni,Al）7 phase, La（Ni,A1）5 phase and （La,Mg）Ni2 phase, while other alloys （x=0.15 and 0.20） consisted of （La,Mg）2（Ni,A1）7 phase, La（Ni,A1）5 phase, （La,Mg）Ni2 phase and （La,Mg）（Ni,A1）3 phase. All alloys showed, however, only one pressure plateau in P-C isotherms. The Pr/La ratio in alloy composition influenced hydrogen storage capacity and kinetics properties. Electrochemical studies showed that the discharge capacity decreased from 360 mAh/g （x=-0.00） to 335 mAh/g （x=-0.20） as x increased. But the high-rate dischargeability （HRD） of alloy electrodes increased from 26% （x=0.00） to 56% （x=-0.20） at a discharge current density of Id=1800 mA/g. Anode polarization measurements were done to further understand the electrochemical kinetics properties after Pr substitution.展开更多
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 phase structure and electrochemical properties of La1.7＋xMg1.3-x（NiCoMn）9.3（x=0-0.4） alloys were investigated. The XRD analysis reveals that the alloys consist of LaNi5 phase and other phases, such as LaMg2Ni...The phase structure and electrochemical properties of La1.7＋xMg1.3-x（NiCoMn）9.3（x=0-0.4） alloys were investigated. The XRD analysis reveals that the alloys consist of LaNi5 phase and other phases, such as LaMg2Ni9 phase （PuNi3 structure） and La4MgNi19 phases （Ce5Co19＋Pr5Co19 structure, namely A5B19 type）. With the increase of the x value, the LaMg2Ni9 phase fades away and La4MgNi19 phases appear, while the abundance of LaNi5 phase firstly increases and then decreases. At the same time, the cell volume of LaNi5 phase and LaMg2Ni9 phase decreases. The electrochemical measurement shows that alloy electrodes could be activated in 4-5 cycles, and with the increase of the x value, the maximum discharge capacity gradually increases from 330.9 mA-h/g （x=0） to 366.8 mA-h/g （x=0.4）, but the high-rate dischargeability （HRD） and cyclic stability （S） decrease somewhat （x=0.4, HRD600=82.32%, S100=73.8%）. It is found that the HRD is mainly controlled by the electrocatalytic activity on the alloy electrode surface, and the decline of cyclic stability is due to the appearance of A5B19 type phase with larger hydrogen storage capacity, which leads to larger volume expansion and more intercrystalline stress and then easier pulverization during charging/discharging.展开更多
基金Project supported by National 863 Program of China (2007AA03Z227, 2007AA03Z230)Natural Science Foundation of Hebei Province (E2010000301)+1 种基金Natural Science Research Planned Project of Hebei University (2009-152)Undergraduate Science and Technology Innovation Project of Hebei University (2010060)
文摘La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） hydrogen storage alloys were prepared by induction melting and effect of Al substitution for Ni on phase constitution and electrochemical property was investigated.With the substitution of Al for Ni,LaNi5 and LaNi2 phases occurred and （La,Mg）2（Ni,Co,Al）7 phase with hexagonal Ce2Ni7-type structure replaced （La,Mg）2（Ni,Co）7 phase.The cell volumes of LaNi5 and （La,Mg）2（Ni,Co,Al）7 main phases increased with increasing Al content.Some electrochemical properties and kinetic parameters of the alloys,including discharge capacity,high rate discharge ability （HRD）,loss angle （ψ）,exchange current density （I0） and limiting current density （IL）,decreased with increasing amount of substitution of Al for Ni.Substitution of Al for Ni could be favorable for positive shift in corrosion potential of the alloy electrode,and prolonged cyclic lifetime of La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） alloy electrodes.
基金supported by the Key Projects in International Science and Technology Cooperation from Ministry of Science and Technology of the PRC (2006DFB52550, 2007DFA51020)the National Natural Science Foundation of China (20363001)
文摘In order to investigate the effect of substituting La with Pr on structural and hydrogen storage properties of La-Mg-Ni system （AB3.5-type） hydrogen storage alloys, a series of La0.65-xPrxNd0.12Mg0.23Ni3.4Al0.1（x=0, 0.10, 0.15, 0.2） hydrogen storage alloys were prepared. X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy dispersive spectrometer （EDS） analyses revealed that two alloys （x=0.0 and 0.10） were composed of （La,Mg）2（Ni,Al）7 phase, La（Ni,A1）5 phase and （La,Mg）Ni2 phase, while other alloys （x=0.15 and 0.20） consisted of （La,Mg）2（Ni,A1）7 phase, La（Ni,A1）5 phase, （La,Mg）Ni2 phase and （La,Mg）（Ni,A1）3 phase. All alloys showed, however, only one pressure plateau in P-C isotherms. The Pr/La ratio in alloy composition influenced hydrogen storage capacity and kinetics properties. Electrochemical studies showed that the discharge capacity decreased from 360 mAh/g （x=-0.00） to 335 mAh/g （x=-0.20） as x increased. But the high-rate dischargeability （HRD） of alloy electrodes increased from 26% （x=0.00） to 56% （x=-0.20） at a discharge current density of Id=1800 mA/g. Anode polarization measurements were done to further understand the electrochemical kinetics properties after Pr substitution.
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
文摘The phase structure and electrochemical properties of La1.7＋xMg1.3-x（NiCoMn）9.3（x=0-0.4） alloys were investigated. The XRD analysis reveals that the alloys consist of LaNi5 phase and other phases, such as LaMg2Ni9 phase （PuNi3 structure） and La4MgNi19 phases （Ce5Co19＋Pr5Co19 structure, namely A5B19 type）. With the increase of the x value, the LaMg2Ni9 phase fades away and La4MgNi19 phases appear, while the abundance of LaNi5 phase firstly increases and then decreases. At the same time, the cell volume of LaNi5 phase and LaMg2Ni9 phase decreases. The electrochemical measurement shows that alloy electrodes could be activated in 4-5 cycles, and with the increase of the x value, the maximum discharge capacity gradually increases from 330.9 mA-h/g （x=0） to 366.8 mA-h/g （x=0.4）, but the high-rate dischargeability （HRD） and cyclic stability （S） decrease somewhat （x=0.4, HRD600=82.32%, S100=73.8%）. It is found that the HRD is mainly controlled by the electrocatalytic activity on the alloy electrode surface, and the decline of cyclic stability is due to the appearance of A5B19 type phase with larger hydrogen storage capacity, which leads to larger volume expansion and more intercrystalline stress and then easier pulverization during charging/discharging.
