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首先采用二步熔炼法制备了铸态Mm(NiCoMnAl)_5-Mg_2Ni复合储氢合金,然后在不同快淬速度下对铸态Mm(NiCoMnAl)_5-Mg_2Ni复合合金进行快淬处理,获得一系列不同快淬速度的快淬态Mm(NiCoMnAl)_5-Mg_2Ni复合储氢合金。利用X射线衍射(XRD)、扫描电镜及能谱分析(SEM/EDS)和电化学测试方法研究了所有合金的微结构和电化学性能。微结构分析表明,铸态Mm(NiCoMnAl)_5-Mg_2Ni复合合金由LaNi_5和少量的Mg_2Ni相组成。而铸态复合合金经快淬处理后,合金中少量的Mg_2Ni相消失,同时有LaNi_3和极少量的La2Ni3新相形成。快淬态合金中的Mg元素主要以固溶形式优先存在于富稀土LaNi_3相中,形成(La,Mg)Ni_3相。电化学分析表明,恰当的快淬处理能使Mm(NiCoMnAl)_5-Mg_2Ni复合合金的活化性能、最大放电容量、放电特性和循环稳定性得到改善。但快淬速度太大,上述性能均有变坏趋势。当快淬速度为15 m·s-1时,Mm(NiCoMnAl)_5-Mg_2Ni复合合金具有最大的放电容量,此时合金的最大放电容量为303.5 m Ah·g~(-1),比铸态合金的最大放电容量增大了3.3%;快淬速度为20 m·s~(-1)时,复合合金的循环稳定性最佳,80次循环后的容量保持率为98.3%,比铸态合金的容量保持率增大了11.9%。
First, a Mm (NiCoMnAl) _5-Mg_2Ni composite hydrogen storage alloy was prepared by a two-step melting method and then the as-quenched Mm (NiCoMnAl) _5-Mg_2Ni alloy was quenched at different quenching speeds to obtain a series of different Rapid Quenching Speed Quenching State Mm (NiCoMnAl) _5-Mg_2Ni Composite Hydrogen Storage Alloy. The microstructures and electrochemical properties of all the alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (SEM / EDS) and electrochemical measurements. Microstructure analysis shows that the as-cast Mm (NiCoMnAl) _5-Mg_2Ni composite alloy consists of LaNi_5 and a small amount of Mg_2Ni phase. After quenching the as-cast alloy, a small amount of Mg_2Ni phase disappears in the alloy, while LaNi_3 and a very small amount of new La_2Ni_3 phase are formed. The Mg element in the quenched alloy preferentially exists in the rare earth-rich LaNi 3 phase as a solid solution, forming the (La, Mg) Ni 3 phase. Electrochemical analysis showed that the activation properties, the maximum discharge capacity, the discharge characteristics and the cycle stability of Mm (NiCoMnAl) _5-Mg_2Ni composite alloy can be improved by proper quenching treatment. However, the quenching speed is too high, the performance of these trends have become worse. When the quenching speed is 15 m · s-1, the maximum discharge capacity of Mm (NiCoMnAl) _5-Mg_2Ni alloy has the maximum discharge capacity of 303.5 m Ah · g -1, The maximum discharge capacity of the alloy increases by 3.3%. When the quenching speed is 20 m · s -1, the cycle stability of the composite alloy is the best. The capacity retention rate after 98 cycles is 98.3% Alloy capacity retention increased by 11.9%.