Hydrogen storage alloy of Mg 2 Ni produced from Mg and Ni ultrafine particles.doc

Hydrogen storage alloy of Mg2Ni produced from Mg and Ni ultrafine particles The State Key Laboratory of Rare Earth Materials Chemistry and Applications, Peking University, Beijing 100871, China Yuejun Yu Abstract: Mg and Ni ultrafine particles were produced by hydrogen plasma metal reaction method, then mixed in the molar ratio of 2:1 and heated in Ar flow atmosphere to get Mg2Ni compound. Structure and hydrogen storage properties of the compound were measured. There are some features about this method: (a) The particles are mixed just by ultrasonic homogenizer, (b) The heating temperature is lower than that in chemical literature and, (c) The process of compound preparation is without hydrogen. This new method has advantages such as short process time, simple equipment and high product purity. The hydrogen absorption rate was enhanced and the plateau pressure was lowered greatly. Keywords: Mg2Ni, ultrafine particles, hydrogen plasma metal reaction, and hydrogen storage alloy. Introduction Mg-based hydrogen storage alloys are always attractive to many investigators, though the hydriding and dehydriding kinetics of Mg are slow and the hydride is too stable for most practical applications. Mg rich intermetallic alloys are being investigated in order to determine the optimum composition leading to the best-reversible hydrogen absorption properties. Among them, Mg2Ni is the most intensively studied compound due to its low specific weight and cost [1]. Several fabrication techniques have been developed to produce nano-scale Mg2Ni, and the typical one is the energetic ball milling of hydrides. But its shortcomings are: the impurity is high, the process time is long, and the product is not uniformity, as a result, application of the method is limited. Nomura et al. [4] and Reily et al. [5] investigated formation of Mg2Ni by heat-treatment of Mg and Ni powder and found that it was possible to get the compound. However, temperature for the treatment was must el