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用高频感应熔炼方法制备了稀土系A2B7型La0.83-xGdxMg0.17N i3.05Co0.3A l0.15(x=0~0.5)储氢合金,在Ar气氛中和1173 K下对铸态合金进行退火处理,通过X射线衍射(XRD)、电子探针显微分析方法(EPMA)和电化学测试等分析方法系统研究了稀土Gd部分替代La元素对合金微观组织和电化学性能的影响规律。研究结果表明,合金退火组织主要由Ce2N i7型、Gd2Co7型、Pr5Co19型、PuN i3型和CaCu5型相组成,稀土Gd元素能有效减少和抑制退火组织中CaCu5型相的形成,随Gd含量x增加,合金相组成中A2B7型(Ce2N i7和Gd2Co7型)相丰度呈先增加后减小的规律,当x=0.2时其相丰度最大(91.0%)。合金的PCT吸氢平台压随Gd含量的增加而升高,x=0.5时吸氢平台压力接近0.1 MPa,x=0.2时合金的吸氢量达到最大值1.34%。电化学测试分析表明,随Gd含量x的增加,合金电极最大放电容量和容量保持率均呈先增加后减小的规律,适量的Gd元素可明显改善合金的综合电化学性能。当x=0.2时,合金电极放电容量达到最大值392.9 mAh.g-1,经100次充放电循环后其电极容量的保持率S100为91.2%,具有较好的综合电化学性能。
The rare earth A2B7 La0.83-xGdxMg0.17N i3.05Co0.3A l0.15 (x = 0 ~ 0.5) hydrogen storage alloy was prepared by high frequency induction melting method. The as-cast alloy The microstructure and electrochemical properties of the alloy were investigated by X-ray diffraction (XRD), electron probe microanalysis (EPMA) and electrochemical measurements. The results show that the microstructure of the alloy annealed mainly consists of Ce2N i7, Gd2Co7, Pr5Co19, PuN i3 and CaCu5 phases. The rare earth Gd can effectively reduce and inhibit the formation of CaCu5 phase in the annealed microstructure. With the increase of Gd content x , The phase abundance of A2B7 (Ce2N i7 and Gd2Co7) first increases and then decreases in the phase composition of the alloy, and its phase abundance is the largest (91.0%) when x = 0.2. The pressure of PCT hydrogen absorption platform increased with the increase of Gd content, and the pressure of hydrogen absorption platform was close to 0.1 MPa when x = 0.5. The maximum hydrogen absorption capacity of alloy reached 1.34% when x = 0.2. Electrochemical tests show that with the increase of Gd content, the maximum discharge capacity and the capacity retention rate of the alloy electrode first increase and then decrease, and the appropriate amount of Gd can obviously improve the electrochemical performance of the alloy. When x = 0.2, the discharge capacity of alloy electrode reached the maximum value of 392.9 mAh.g-1. After 100 cycles of charging and discharging, its electrode capacity retention S100 was 91.2%, which showed good electrochemical performance.