Hydrogenation and corrosion properties of nanocrystalline A(2)B(7) type, La-Mg-Ni based intermetallics modified by nickel sputtering

In the paper, hydrogenation and corrosion properties of three kinds of nanocrystalline La1.5Mg0.5Ni7 type alloys obtained by mechanical alloying (MA) method are discussed in view of their application as anodic materials for Ni/MH batteries. Partial substitutions of cobalt for nickel and gadolinium for lanthanum and then magnetron sputtering of the intermetallic powders with amorphous nickel distinctly change functional parameters of the hydrogen storage material. It is shown that 5.5 at.% cobalt addition markedly improves the alloy activation but worsens its corrosion resistance in concentrated KOH solution. On the other hand, partial substitution of lanthanum by Gd (2.2 at.%) ensures large exchange currents for H2O/H-2 system. Presence of Ni coatings on alloy particles is generally advantageous from the material H-storage properties, although they slow down a little hydrogen transport during electrode discharge.