La替代Mm对低钴AB5型贮氢合金电化学性能的影响

The Effects of the Substitution La for Mm on the Electrochemical Properties of Low-Co AB5-Type Hydrogen Storage Alloys

摘要:

用XRD和SEM测试了稀土基低钻AB5型LaxMm1-x（NiMnSiAlFe）4．7Co0.2（x=0,1）贮氢合金的微观结构，并全面测试了合金在铸态及快淬态下的电化学性能。研究了La替代Mm对铸态及快淬态低钻贮氢合金微观结构及电化学性能的影响。对合金的电化学性能研究结果表明：La替代Mm使合金的放电容量提高，并使铸态合金的循环寿命由341次提高到370次；La替代Mm使得快淬态合金的循环寿命的增加幅度较小，主要原因是La替代Mm使快淬态合金的晶粒粗化。微观结构测试结果表明：La替代Mm使合金中的第二相消失，并使合金的晶格常数在a轴方向增加，在c轴方向略有减小，晶胞体积增大，这是La替代Mm使合金放电容量提高的主要原因。

Abstract:

The microstructures of the rare-earth-based Low-Co AB5-type LaxMm1-x(NiMnSiAlFe)4.7Co0.2(x=0,1)alloys for hydrogen storage were determined by XRD and SEM,and the electrochemical performances of the as-cast and quenched alloys were measured synthetically.The effects of the substitution La for Mm on microstructures and electrochemical characteristics of the as-cast and quenched alloys were studied.The obtained results show that the substitution La for Mm extends the cycle life of the as-cast alloy and improves the discharge capacity of the alloys because the substitution La for Mm makes the secondary phase disappear and the cell volume enlarge.Rapid quenching can improve the cycle stability of the alloys,but it isn't notable to the as-quenched La1 alloy.It is mainly attributed to the larger grain produced by substitution La for Mm.