(江蘇科技大學(xué)材料科學(xué)與工程學(xué)院，鎮(zhèn)江 212003)
摘 要: 采用中間合金法在感應(yīng)熔煉爐中制備La4MgNi19-xCox(x=0~2)合金，研究Co部分替代Ni對(duì)合金相結(jié)構(gòu)和電化學(xué)性能的影響。XRD測(cè)試結(jié)果表明：合金主要由La4MgNi19(Ce5Co19+Pr5Co19)相和LaNi5相組成；x的增加有利于促進(jìn)La4MgNi19相的形成，且晶胞體積隨之增大。顯微組織觀察發(fā)現(xiàn)，合金為樹(shù)枝晶結(jié)構(gòu)，x的增加會(huì)使樹(shù)枝晶變細(xì)。電化學(xué)測(cè)試表明：合金均具有良好的活化性能和高倍率放電性能(HRD600＞92.57%)；隨著x的增加，合金的最大放電容量明顯提高(從x=0時(shí)的359.23 mA？h/g增大到x=2的380.85 mA？h/g)，而循環(huán)壽命則先下降后逐漸提升。高倍率放電性能主要由合金電極的擴(kuò)散系數(shù)控制，而循環(huán)穩(wěn)定性的下降則是由于合金中La4MgNi19相的增加使膨脹率和晶間應(yīng)力集中增大加速粉化所致。
關(guān)鍵字: 貯氫合金；A5B19型；晶體結(jié)構(gòu)；電化學(xué)性能；La-Mg-Ni系
（School of Materials Science and Engineering,
Jiangsu University of Science and Technology, Zhenjiang 212003, China）
Abstract:TheLa4MgNi19-xCox(x=0-2) alloys were prepared by intermediate alloy method in vacuum levitation melting furnace, and their phase structure and electrochemical properties were investigated systematically. The XRD results show that all alloys consist of LaNi5 and La4MgNi19 phases (Ce5Co19+Pr5Co19 structure). The increase of x value can promote the formation of La4MgNi19 phase and increase the cell volume of that phase. The microstructure observation reveals that the microstructures of all alloys are dendritic structure, which becomes fine with the increase of x value. The electrochemical measurements show that all alloys have good activation performance and high-rate discharge-ability (D600, HR>92.57%). With the increasing of x value, the maximum discharge capacity of the alloy increases obviously (increasing from 359.23 mA？h/g at x=0 to 380.85 mA？h/g at x=2), and the cycle life first decreases and then increases gradually. The high ratio discharge properties are mainly controlled by the diffusion coefficient of the alloy electrode, and the declination of cycle stability is due to the accelerating pulverization caused by the increase of inter-granular stress concentration and the higher expansion ratio of La4MgNi19 phase.
Key words: hydrogen storage alloy; A5B19 type; crystal structure; electro chemical property; La-Mg-Ni system
