硼对稀土系AB5型贮氢合金微观结构及电化学性能的影响

测试分析了稀土系AB5型贮氢合金MmNi3.8Co0.4Mn0.6Al0.2Bx(x=0, 0.1, 0.2, 0.3, 0.4)的微观结构及电化学性能, 研究了硼含量x对贮氢合金电化学性能及微观结构的影响.结果表明, 铸态贮氢合金具有双相组织, 主相为CaCu5型相, 还有少量CeCo4B第二相, 第二相的相丰度随x的增加而增大.对合金进行了不同淬速的快淬处理, 合金中第二相的量随淬速的增加而减少.硼的加入使合金的电化学容量下降, 但活化性能及循环寿命明显提高.特别是对于快淬态合金, 硼对因促进非晶的形成而显著提高循环寿命.

Effect of boron additive on microstructures and electrochemical properties of rare earth-based AB5 hydrogen storage alloy

The microstructures and electrochemical properties of the as-cast and quenched alloys MmNi_(3.8)(Co_(0.4)-)(Mn_(0.6)Al_(0.2)B_x)(x=0, 0.1, 0.2, 0.3, 0.4were analyzed and measured. The effect of boron additive on the microstructures and electrochemical properties of the as-cast and quenched alloys MmNi_(3.8)Co_(0.4)Mn_(0.6)Al_(0.2) were investigated comprehensively. The experimental results show that the microstructure of as-cast alloys MmNi_(3.8)Co_(0.4)Mn_(0.6)Al_(0.2)B_x(x=0, 0.1, 0.2, 0.3, 0.4 is composed of CaCu_5-type main phase and a small amount of CeCo_4B-type secondary phase. The abundance of secondary phase increases with the increase of boron content. The rapid quenching technology was used in the preparation of the alloys. The amount of secondary phase in the alloys decreases with the increase of quenching rate. The electrochemical tests show that the addition of boron modifies the activation properties and dramatically enhances the cycle lives, but lead to the decrease of the capacities of the as-cast and quenched alloys. The influences of boron addition on the electrochemical properties of as-quenched alloys are much stronger than that of as-cast alloys, because boron strongly promotes the formation of amorphous phase in as-quenched alloy.