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为了改善Mg2Ni型合金的电化学贮氢性能,用La部分替代Mg,并用铸造及快淬工艺制备了Mg2-xLaxNi(x=0、0.2、0.4、0.6)电极合金,获得长度连续,厚度约为30μm,宽度约为25mm的薄带。用XRD、SEM和HRTEM分析了快淬合金薄带的微观结构,测试了合金薄带的电化学性能、电化学交流阻抗谱(EIS)及氢在合金中的扩散系数(D)。结果发现,在快淬无La合金中没有出现非晶相,但快淬La替代合金显示了以非晶相为主的结构,表明La替代Mg提高了合金的非晶形成能力。当x≤0.2时,La替代Mg不改变合金的Mg2Ni型主相,但出现少量的LaMg3及La2Mg17相。La替代及快淬明显改善合金的电化学贮氢性能。其中,Mg2La0.2Ni合金具有最佳的综合电化学性能。当淬速从0m/s(铸态被定义为淬速0m/s)增加到30m/s时,Mg2La0.2Ni合金的放电容量从197.2mAh/g增加到406.5mAh/g,20次充放循环后的容量保持率从52.7%增加到81.4%,高倍率放电能力从48.3%增加到56.8%,氢扩散系数(D)从8.12×10-12cm2/s增加到1.80×10-11cm2/s。 相似文献
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贮氢合金在高温下会表现出与常温不同的电化学特性,以La0.75Mg0.25Ni3.5Si0.10合金为研究对象,采用交流阻抗谱和电位阶跃方法,对其高温使用环境下(30~70℃)的高倍率放电特性和动力学性能进行了深入的研究。研究结果表明合金的动力学性能是由电化学反应与氢的扩散共同控制的,合金的电荷传递电阻随温度升高而减小,高温有助于电极表面电化学反应速度的提高;但对于La0.75Mg0.25Ni3.5Si0.10合金存在最佳氢扩散温度,当温度高于其最佳温度时,由于释氢等副反应的进行,以及氧化腐蚀反应的加剧等,使合金的扩散系数反而减小;在合金表面电化学反应速度与氢扩散系数共同作用下,La0.75Mg0.25Ni3.5Si0.10合金高倍率放电性能在45℃时最优异,当温度高于45℃时反而降低。 相似文献
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In order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys, Ni in the alloy is substituted by element Co. The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1−x
Co
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(x=0, 0.1, 0.2, 0.3, 0.4) alloys were synthesized by melt-spinning technique. The structures of the as-cast and spun alloys
were studied with an X-ray diffractometer (XRD) and a high resolution transmission electronic microscope (HRTEM). An investigation
on the thermal stability of the as-spun alloys was carried out with a differential scanning calorimeter (DSC). The hydrogen
absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus. The results
demonstrate that the substitution of Co for Ni does not alter the major phase of Mg2Ni but results in the formation of secondary phase MgCo2. No amorphous phase is detected in the as-spun Co-free alloy, but a certain amount of amorphous phase is clearly found in
the as-spun Co-containing alloys. The substitution of Co for Ni exerts a slight influence on the hydriding kinetics of the
as-spun alloy. However, it dramatically enhances the dehydriding kinetics of the as-cast and spun alloys. As Co content (x) increases from 0 to 0.4, the hydrogen desorption capacity increases from 0.19% to 1.39% (mass fraction) in 20 min for the
as-cast alloy, and from 0.89% to 2.18% (mass fraction) for the as-spun alloy (30 m/s). 相似文献
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In order to improve the electrochemical performances of La-Mg-Ni based electrode alloys with PuNi3-type structure, a trace of boron was added in La0.7Mg0.3Ni2.55Co0.45 alloy. The La0.7Mg0.3Ni2.55Co0.45Bx(a=0, 0.05, 0.1, 0.15 and 0.2) alloys were prepared by casting and rapid quenching. The electrochemical performances and microstructures of the as-cast and quenched alloys were investigated. The effects of rapid quenching on the microstructures and electrochemical performances of the above alloys were investigated. The results show that the as-cast and quenched alloys are composed of (La, Mg)Ni3 phase, LaNi5 phase and LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloys containing boron, and the Ni2B phase in the B-contained alloys nearly disappears after rapid quenching. Rapid quenching increases the amount of the LaNi2 phase in the B-free alloy, but it decreases the amount of the LaNi2 phase in the boron-containing alloys. The effects of rapid quenching on the capacities of the boron-containing and boron-free alloys are different. The capacity of the B-free alloy monotonously decreases with increasing quenching rate, whereas the capacities of the B-contained alloys have a maximum value with the change of the quenching rate. The rapid quenching can improve the stability of La-Mg-Ni based electrode alloy but lowers the discharge plateau voltage and decreases the plateau length. The effect of rapid quenching on the activation capabilities of the alloys was complicated. 相似文献
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Fe替代Co对AB5型贮氢合金循环稳定性的影响 总被引:2,自引:0,他引:2
用铸造及快淬的方法制备了稀土基AB5型Mm(NiMnSiAl)4.3Co0.6-xFex(x=0,0.1,0.2,0.3,0.4,0.5,0.6)贮氢合金,用XRD。TEM及SEM观测了铸态及快淬态的微观结构,测试了合金在铸态及快淬态下的电化学循环稳定性。研究了Fe替代Co对铸态及快淬态贮氢合金微观结构及循环稳定性的影响。研究结果表明,Fe替代Co对铸态及快淬态合金的相结构没有明显影响,但对合金的循环稳定性产生显著影响。Fe替代Co能不同程度地改善铸态及快淬态合金的循环稳定性,但对快淬态合金循环寿命的改善更加显著,导致这一结果的主要原因是Fe替代Co使快淬态合金的微观组织显著细化。 相似文献
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对AB5型LaxMm1-x(NiMnSiAlFe)49(x=0,0.45,0.75,1.00,摩尔分数)贮氢合金进行了快淬处理,研究了La含量及快淬工艺对合金微观结构及电化学循环稳定性的影响.结果表明:La含量的增加对铸态合金的循环稳定性没有明显影响,但使快淬态合金的循环稳定性下降,且快淬处理能显著提高合金的循环稳定性.当La替代量从0增加到1.00时,经300次充放循环后,铸态合金的容量保持率(Rh)从59.2%增加到59.8%;16 m/s淬速快淬态合金的容量保持率从83.9%下降到65.0%.对于x=0.45的合金,当淬速从0(铸态被定义为淬速等于0)增加到28 m/s时,容量保持率从59.8%增加到75.8%. 相似文献
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用XRD和SEM测试了稀土基低钻AB5型LaxMm1-x(NiMnSiAlFe)4.7Co0.2(x=0,1)贮氢合金的微观结构,并全面测试了合金在铸态及快淬态下的电化学性能。研究了La替代Mm对铸态及快淬态低钻贮氢合金微观结构及电化学性能的影响。对合金的电化学性能研究结果表明:La替代Mm使合金的放电容量提高,并使铸态合金的循环寿命由341次提高到370次;La替代Mm使得快淬态合金的循环寿命的增加幅度较小,主要原因是La替代Mm使快淬态合金的晶粒粗化。微观结构测试结果表明:La替代Mm使合金中的第二相消失,并使合金的晶格常数在a轴方向增加,在c轴方向略有减小,晶胞体积增大,这是La替代Mm使合金放电容量提高的主要原因。 相似文献