快淬工艺对Mg2Ni型合金气态及电化学贮氢动力学的影响

Influence of Melt Spinning on Gaseous and Electrochemical Hydrogen Storage Kinetics of Mg2Ni-type Alloys

摘要:

用铸造及快淬工艺制备Mg2Ni型Mg2-xLaxNi (x=0, 0.2, 0.4, 0.6)贮氢合金。用XRD、SEM、HRTEM分析铸态及快淬态合金的微观结构，合金的气态贮氢动力学性能用自动控制的Sieverts设备测试，并用程控电池测试仪测试合金的电化学贮氢动力学。结果发现，La替代Mg明显地改变Mg2Ni型合金的相组成。当x≤0.2时，La替代Mg不改变合金的主相Mg2Ni，但出现少量的LaMg3及La2Mg17相。当La替代量x≥0.4时，合金的主相改变为(La, Mg)Ni3+LaMg3。快淬含La合金显示了以非晶相为主的结构，表明La替代Mg提高了Mg2Ni型合金的非晶形成能力。合金的气态及电化学吸放氢动力学对La含量及快淬工艺敏感，适当的快淬处理可以提高合金的气态及电化学贮氢动力学，但获得最佳贮氢动力学的快淬工艺与合金的成分密切相关

Abstract:

The Mg2Ni-type Mg2-xLaxNi (x=0, 0.2, 0.4, 0.6) hydrogen storage alloys were synthesized by casting and direct melt quenching technique. The microstructures of the as-cast and spun alloys were investigated by XRD, SEM and HRTEM. The gaseous hydrogen storage kinetics of the alloys was measured using an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the alloys was tested by constant current to charge and discharge the electrode. The results show that the substitution of La for Mg visibly alters the phase composition of the alloys. For x≤0.2, the substitution leads to formation of a small amount of secondary phases LaMg3 and La2Mg17 without changing major phase Mg2Ni. But the major phase of the alloys are changed to the (La, Mg)Ni3+LaMg3 phases by increasing La content to x≥0.4. The as-spun alloys substituted by La hold an evident amorphous structure, meaning the substitution of La for Mg facilitates the glass formation of the Mg2Ni-type alloy. The gaseous and electrochemical hydrogen storage kinetics of the alloys are sensitive to both the amount of La substitution and the melt spinning technology. The appropriate melt spinning process can significantly ameliorate the gaseous and electrochemical hydrogen storage kinetics of the alloys, whereas the melt spinning technology, by which the optimal hydrogen storage kinetics of the alloy can be yielded, is associated with the chemical composition of the alloy