Nanocrystalline composite for storage of hydrogen

A method for preparing a material adapted for reversible storage of hydrogen, comprising the successively performed steps of:

• (a) providing a first powder of a magnesium-based material;
• (b) hydrogenating the first powder to convert at least part of the first powder into metal hydrides;
• (c) mixing the first hydrogenated powder with a second powder of an additive, the proportion by mass of the second powder in the resulting mixture ranging from between 1 and 20% by mass;
• and
• (d) milling the mixture of the first and second powders,
• the method further comprising forming said additive, to be mixed with said first hydrogenated powder, by mechanosynthesis by co-milling of a first metal mixture (m1) and a second metal mixture (m2):
• said first metal mixture (m1) comprising either:
• a first metal alloy (a1), of body-centered crystal structure, based on titanium (Ti), on vanadium (V), and on another metal M selected from among chromium (Cr), manganese (Mn), and alloys of these metals;
• or
• a mixture of the metals forming said first metal alloy (a1), in the proportions of said first metal alloy (a1), these metals being present in the mixture as simple metals or as metal alloys;
• and
• said second metal mixture (m2) comprising either:
• a second metal alloy (a2) comprising:
• from 38 to 42 mol % of a first metal selected from among zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), tungsten (W), and mixtures of these metals;
• and
• from 56 to 60 mol % of a second metal selected from among nickel (Ni), copper (Cu), and alloys of these metals;
• or
• a mixture of the metals forming said second metal alloy (a2), in the proportions of said second metal alloy (a2), these metals being present in the mixture as simple metals or as metal alloys;
• wherein said first and second metal mixtures (m1, m2) have a mass ratio (m2)/(m1+m2) ranging from 0.1% to 20% by mass in the mechanosynthesis step,
• wherein the additive has a majority phase based on titanium, vanadium, and chromium and/or manganese, scattered in the form of grains, and at least one intergranular phase based on said first and second metals of said second metal mixture (m2).