Study of an industrially oriented Mg content control technology during annealing process for the LaMg(Ni[sbnd]Al)3.5 hydrogen storage alloy

Abstract

In this paper, we propose a novel and industrial feasible method for the high temperature annealing process of Mg-contained hydrogen storage alloys. To keep the Mg content in the alloy constant during manufacturing at high temperatures, the annealing process is carried out in a sealed container together with an external Mg vapor-producing source. The closed environment reduces the volume for the forming of Mg vapor pressure during the annealing process and excludes the influence from the “Cold Zone” areas of the furnace. External Mg metal, which is also loaded in the container with the alloy, plays an important role in providing the Mg source for the forming of the Mg vapor. This reduces the required Mg amounts from the alloy to produce saturated Mg vapor pressure during the annealing process. Our experimental results show that alloys annealed by this novel method have better electrical discharge properties and cyclic stability compared to alloys prepared by traditional annealing method used by most of hydrogen storage alloy manufacturers. This method could help to reduce the alloy production costs by making the phases' ratio and performance change of the alloy more controllable during the production of this kind of hydrogen storage alloys.