Influence of boron on the hydriding of nanocrystalline Mg2Ni

Nanocrystalline Mg2Ni(B) alloys (Mg64Ni32B4 and Mg58Ni29B13) were synthesized by ball milling and their hydrogen sorption properties were characterized by three different methods: Sievertʹs type apparatus, High-pressure DSC and by electrochemical hydrogen charge/discharge. The main idea was to elucidate the influence of boron on the hydriding behavior of Mg2Ni, an intermetallic compound largely investigated for hydrogen storage, but still needing improvement. Boron was selected because of its small atomic radius and large electronegativity, as well as chemical resistance in solutions of alkaline basics. en capacity and hydriding/dehydriding cycle life of the alloys were found to depend on the presence of B. Whereas small amounts of boron (4 at.%) increase the maximum hydrogen capacity of Mg2Ni, at higher B concentration (13 at.%) the capacity and cycle life deteriorate significantly due to the Mg2Ni(B) solid solution decomposition during hydriding/dehydriding. Rapid worsening was found to take place during the first 2–3 electrochemical charge/discharge cycles to a much larger extent for Mg2Ni(B), compared to pure Mg2Ni.