Structural studies of a new Laves phase alloy (Hf,Ti)(Ni,V)(2) and its very stable hydride

With Guinier-Hagg X-ray diffraction, a new AB(2) hafnium containing hexagonal C14 Laves type alloy has been identified, in a vanadium based, bcc, TiV3Ni0.56 solid solution alloyed with hafnium. The unit cell dimensions were determined to be a = 5.024(7) and c = 8.194(4) Angstrom. It also forms a hydride with the expanded unit cell dimensions a = 5.234(4) and c = 8.579(7) Angstrom, which was found to be very stable. It needed to be heated to above 600 degrees C in vacuum to be dehydrided. From electrochemical measurements on the TiV3Ni0.56 solid solution it was concluded that both the activation and the reaction kinetics were improved by the presence of the new Laves phase. We assume that the formation of the Laves phase hydride helps to disintegrate the bulk alloy to give it a large and active surface area. From the structural refinements of the new Laves phase it was further suggested that hafnium formed a solid solution on the A-element site with one of the lighter atoms, probably titanium. Nickel was found on the two B-element sites, mixed with a light atom, probably vanadium.