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用铸造及快淬工艺制备了A2B7型电极合金,合金的名义成分为La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1(x=0,0.05,0.1,0.15,0.2)。深入研究了Zr替代La对合金微观结构及电化学性能的影响。用XRD、SEM、TEM分析了合金的结构。结果表明,铸态及快淬态合金均具有多相结构,含有两个主相(La,Mg)Ni3和LaNi5以及一个残余相LaNi2。Zr替代La使合金中LaNi5相明显增加,并促进快淬态合金中形成非晶相。电化学测试的结果表明,Zr替代La明显降低合金的放电容量,但显著改善合金的电化学循环稳定性。当Zr含量小于0.1时,合金的放电容量随淬速的增加而先增加后减小,合金的循环稳定性随淬速的增加而单调增加。
A2B7 electrode alloy was prepared by casting and rapid quenching process. The nominal composition of the alloy is La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1 (x = 0,0.05,0.1,0.15,0.2). The effects of Zr substitution on the microstructure and electrochemical properties of the alloys were investigated. The structure of the alloy was analyzed by XRD, SEM and TEM. The results show that the as-cast and quenched alloys all have a multi-phase structure with two main phases (La, Mg) Ni3 and LaNi5 and a residual phase LaNi2. The substitution of La for Zr increases the LaNi5 phase obviously and promotes the formation of amorphous phase in the rapidly quenched alloy. The results of electrochemical tests show that the substitution of La for Zr significantly reduces the discharge capacity of the alloy, but significantly improves the electrochemical cycling stability of the alloy. When the content of Zr is less than 0.1, the discharge capacity of alloy increases first and then decreases with the increase of quenching rate. The cycling stability of the alloy monotonically increases with the increase of quenching rate.