Structures and Electrochemical Hydrogen Storage Properties of the As-Spun RE-Mg-Ni-Co-Al-Based AB 2 -Type Alloys Applied
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THE end of the Stone Age is not because of the depletion of the stone. Likewise, the end of the fossil fuel era does not need to wait until it dries up. In other words, human beings cannot be forced to abandon the car due to the exhaustion of fossil fuels; instead, mankind is very likely to initiatively give up fossil fuels in the case of the great development of the automobile. The excessive consumption of limited fossil fuels causes a series of environmental problems. Especially, the dramatic growth of the global warming rate and air pollution index has attracted widespread international attention and concerns. Also, it was reported that approximately 25 pct of world total energy was consumed by transport[1] and globally above 23 pct CO2 emissions from vehicular waste gases via the combustion of fossil fuels.[2,3] Hence, a widespread application of electric vehicle (EV) and hybrid electric vehicle (HEV) is considered to be a potential approach to reduce both
YANGHUAN ZHANG is with the Elected State Key Laboratory, Inner Mongolia University of Science and Technology, 7 Aerding Avenue, Baotou 014010, People’s Republic of China, and also with the Department of Functional Material Research, Central Iron and Steel Research Institute, 76 Xueyuannan Road, Beijing 100081, People’s Republic of China. Contact e-mail: [email protected] ZEMING YUAN, HONGWEI SHANG, YAQIN LI, YAN QI and DONGLIANG ZHAO are with the Department of Functional Material Research, Central Iron and Steel Research Institute, People’s Republic of China. Manuscript submitted November 10, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
carbon dioxide emissions and fossil energy consumption. Some hydrogen storage materials are considered to be candidates as the negative electrode of Ni-MH batteries, especially the rare earth (RE)-based AB2 and AB5-type alloys which have achieved a large-scale commercial application, but none of them is satisfactory because of some of their inherent shortcomings, including the difficulty of being activated for AB2 alloy and the relatively low specific capacity for AB5 alloy. Considering comprehensive electrochemical property, RE-Mg-Ni-based AB2-type and A2B7-type alloys were viewed as the most attractive and potential candidates for the negative electrode[4,5] due to their lower production cost and reach to 380 to 410 mAh/g of discharge capacities, as claimed by Kohno et al.[6] and Kadir et al.[7] Wang et al.[8] provided LaMgNi4 alloys synthesized by mechanical milling and measured its maximum discharge capacity which was about 400 mAh/g. Although extensive studies have been recently performed to achieve the goal of commercial application as supported by Liu et al.,[9,10] however, those attempts were thwarted by the poor cycle stability of those alloys. Consequently, researchers in this area still face a major challenge: finding a new type hydrogen storage alloy that can be applied in practical negative electrode. Microstructure refining and alloying are verified to be effective methods for improving the hydrogen storage
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