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Structure and Electrochemical Properties of AB_n(n=3.3,3.5) Hydrogen Storage Alloys

Author: JiaQiuRong
Tutor: LuoYongChun
School: Lanzhou University of Technology
Course: Materials Processing Engineering
Keywords: La-Mg-Ni - based hydrogen storage alloy Element substitution Phase structure Electrochemical properties
CLC: TG139.7
Type: Master's thesis
Year: 2009
Downloads: 35
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Abstract


On the basis of a comprehensive review of domestic and foreign La-Mg-Ni-based hydrogen storage alloy research progress to determine the La-Mg-Ni hydrogen storage alloy A287 type using XRD, EPMA, Rietveld whole pattern fitting other materials and electrochemical test methods phase structure and electrochemical properties of the alloy. Examines the influence of rare earth based elements with different atomic radii alternative low phase the Mg hydrogen storage alloy composition and phase structure and electrochemical properties. In La0.63R0.2Mg0.17Ni2.8Co0.2Al0.2Zn0.1 (R = Ce, Pr, Nd, Gd, Y and Sc) alloy as the object of study, this paper investigated rare earth element R partial substitution of La alloy phase structure and the phase composition and electrochemical properties. The results show that the alloy La0.83Mg0.17Ni2.8Co0.2Al0.2Zn0.1 annealing tissue mainly by morphotropic phase Ce2Ni7 (or Gd2Co7 type) the PuNi3 - type phase and CaCu5 type phase composition; Ce, Pr and Nd elements substitute for the alloy phase composition without obvious effect, while Gd element substitution makes alloy CaCu5-type phase significantly reduced Ce2Ni7 - type (or Gd2Co7 type) phase significantly with the increase of its relative abundance degrees 79.03%; Y-and Sc element alternative alloy in Gd2Co7 type phase basic disappear. Electrochemical testing and analysis indicate that the activation properties of the alloy electrode rare earth elements R instead of La, Nd, Gd, Y and Sc partial substitution of La certain extent, improve the maximum discharge capacity of the alloy, and the alloy replacement of Gd the maximum discharge capacity of the electrode reaches 343.1 mAh / g; Gd and Nd element partial substitution of La has been markedly improved cyclic stability of the alloy electrode, the charge and discharge after 100 cycles-capacity retention rate (S1oo) reached 95.3% and 93.0% respectively. In addition, Sc element partial substitution of La alloy electrodes can improve the high-rate discharge performance. On this basis, AB35-type alloys for the study. No Al alloy La0.63Gd0.2M90.17Ni3.2Co0.3 of emphasis on the A1 alloy La0.63Gd0.2Mg0.17Ni3.1Co0.3Al0.1 and low Mg content alloys La0.63Gd0.2Mg0.17Ni3.1Co0.3Al0. with high Mg content the alloy La0.5Gd0.2Mg0.3Ni3.1Co0.3Al0.1 on the the AB35 type of alloy composition and phase structure and electrochemical properties of the law. The results show that the basic La0.63Gd0.2Mg0.17Ni3.1Co0.3Al0.1 alloy for Ce2Ni7 pure phase, the relative abundance of 93.99%, the alloy electrode showed good electrochemical performance, the maximum discharge capacity of 396.2mAh / g, S100 for 95.8%. The other two alloys by Ce2Ni7/Gd2Co7 Pr5Co19 PuNi3 and CaCu5 multiphase composition CaCu5-type phase content. In Pr5Co19 La0.5Gd0.2Mg0.3Ni3.1Co0.3Al0.1 alloy and PuNi3 type phase increased significantly compared with the La0.63Gd0.2Mg0.17Ni3.2Co0.3 alloy. The electrochemical tests, the two alloy electrode discharge capacity and S100 have different degrees of reduction. In addition, La0.63Gd0.2Mg0.17Ni3.2Co0.3 alloy electrode showed good high-rate discharge performance, HRD900 88.6%.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > The alloy learn with a variety of properties of alloys > Other special nature of the alloy > Hydrogen storage alloy
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