In order to improve the cyclic stability of La-Mg-Ni system （Ce2Ni7-type） alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure ...In order to improve the cyclic stability of La-Mg-Ni system （Ce2Ni7-type） alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure of the alloys were investigated in detail. XRD results showed that the alloys had multiphase structure composed of （La, Mg）2Ni7, LaNi5 and small amount of LaNi2 phases. The discharge capacity of the alloys first increased and then decreased with increasing Co content. At a discharge current density of 900 mA/g, the HRD of the alloy electrodes increased from 81.3% （x=0） to 89.2 % （x=0.2）, and then reduced to 87.8 % （x=0.6）. After 60 charge/discharge cycles, the capacity retention rate of the alloys enhanced from 52.67% to 61.32%, and the capacity decay rate of the alloys decreased from 2.60 to 2.05 mAh/g per cycle with increasing Co content. The obtained results by XPS and XRD showed that the fundamental reasons for the capacity decay of the La-Mg-Ni system （Ce2Ni7-type） alloy electrodes were corrosion and oxidation as well as passivation of Mg and Lain alkaline solution.展开更多
基金the National Natural Science Foundation of China (50701011)Natural Science Foundation of Inner Mongolia, China (200711020703)Science and Technology Planned Project of Inner Mongolia, China (20050205)
文摘In order to improve the cyclic stability of La-Mg-Ni system （Ce2Ni7-type） alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure of the alloys were investigated in detail. XRD results showed that the alloys had multiphase structure composed of （La, Mg）2Ni7, LaNi5 and small amount of LaNi2 phases. The discharge capacity of the alloys first increased and then decreased with increasing Co content. At a discharge current density of 900 mA/g, the HRD of the alloy electrodes increased from 81.3% （x=0） to 89.2 % （x=0.2）, and then reduced to 87.8 % （x=0.6）. After 60 charge/discharge cycles, the capacity retention rate of the alloys enhanced from 52.67% to 61.32%, and the capacity decay rate of the alloys decreased from 2.60 to 2.05 mAh/g per cycle with increasing Co content. The obtained results by XPS and XRD showed that the fundamental reasons for the capacity decay of the La-Mg-Ni system （Ce2Ni7-type） alloy electrodes were corrosion and oxidation as well as passivation of Mg and Lain alkaline solution.
文摘研究了Sr、La单独和复合添加对SAl 4047铝合金焊丝氢含量以及6082焊接接头力学性能的影响。结果表明:单独添加0.015%(质量分数,下同)Sr的SAl 4047焊丝铸态组织中α-Al枝晶的二次枝晶臂间距减小,初晶硅相受抑制而消失,共晶硅相的平均尺寸为0.56μm,与不做任何添加的焊丝合金相比平均尺寸下降了84%;固体测氢试验结果表明添加0.015%Sr的SAl 4047焊丝氢含量为0.53 mL/100 g Al,采用该焊丝焊接得到的6082焊缝气孔率为1.81%,焊丝氢含量和焊缝气孔率均超标。单独添加0.08%La可使SAl 4047焊丝氢含量降低到0.18 mL/100 g Al,铸态组织中初晶硅尺寸减小且边角钝化,部分α-Al枝晶向等轴晶转变,共晶硅颗粒平均尺寸为1.24μm,La变质效果明显弱于Sr,当La添加量超过0.08%时,反而会导致针状的富La相产生,降低焊丝及焊缝的力学性能。复合添加的Al-12Si-0.015Sr-0.08La焊丝铸态组织中初晶硅和共晶硅相均完全变质,共晶硅颗粒平均尺寸为0.6μm,α-Al相以柱状晶和等轴晶形式共存;复合焊丝氢含量为0.31 mL/100 g Al,该焊丝焊接所得的6082焊缝气孔率为0.38%,焊丝氢含量和焊缝气孔率均满足标准;接头力学性能试验结果表明,复合焊丝焊接得到的接头的抗拉强度、断后伸长率、弯曲断裂角度分别为186.7 MPa、8.4%、45~52°,与未添加Sr或La的焊丝所得焊接接头相比,分别提高了6.7%、29.2%、76%。
