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为了改善铸态La3MgN i14合金的电化学性能,在0.3 MPa氩气气氛下对La3MgN i14合金进行了10 h退火处理,退火温度分别为1 123,1 223和1 323 K。采用X射线衍射(XRD)、扫描电镜(SEM)和电化学实验研究了合金的微观结构和电化学性能。结果表明,铸态及1 123 K温度退火后的合金由LaN i5相、(La,Mg)2N i7相以及少量的LaN i2相组成。1 223 K温度退火后合金含有LaN i5,(La,Mg)2N i7和(La,Mg)N i3相。1 323 K温度退火后合金的主相为LaN i5和(La,Mg)N i3相。与铸态合金相比,退火后合金组织更加均匀,晶粒长大。随着退火温度的增加,合金的一些电化学性能(如最大放电容量、放电效率、循环稳定性)以及动力学参数(如高倍率放电性能)增强,而电位差和电荷迁移电阻降低。在本研究范围内,为了放电容量和循环稳定性之间的平衡,铸态La3MgN i14合金的适宜退火温度为1 323 K。
In order to improve the electrochemical performance of the as-cast La3MgN i14 alloy, the La3MgN i14 alloy was annealed for 10 h in a 0.3 MPa argon atmosphere at annealing temperatures of 1 123, 1 223 and 1 323 K, respectively. The microstructure and electrochemical properties of the alloy were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. The results show that the as-cast and 1 123 K annealed alloys consist of LaNi5 phase, (La, Mg) 2Ni7 phase and a small amount of LaNi2 phase. 1 223 K annealed alloys containing LaN i5, (La, Mg) 2N i7 and (La, Mg) Ni 3 phases. 1 323 K The main phases of the alloy after annealing are LaN i5 and (La, Mg) Ni 3 phases. Compared with the as-cast alloy, the alloy structure is more uniform after annealing and the grains grow up. With the increase of annealing temperature, some electrochemical properties (such as maximum discharge capacity, discharge efficiency, cycle stability) and kinetic parameters (such as high-rate discharge performance) of the alloy increase, while the potential difference and charge transfer resistance decrease. Within the scope of this study, a suitable annealing temperature for the as-cast La3MgN i14 alloy was 1 323 K for the balance between discharge capacity and cycle stability.