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 he xagonal C14 Laves type alloy has been identified, in a vanadium based, bcc, TiV3Ni0.56 solid solution alloyed with hafnium. The unit cell di mensions 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. I t needed to be heated to above 600 degrees C in vacuum to be dehydride d. From electrochemical measurements on the TiV3Ni0.56 solid solution it was concluded that both the activation and the reaction kinetics we re improved by the presence of the new Laves phase. We assume that the formation of the Laves phase hydride helps to disintegrate the bulk a lloy to give it a large and active surface area. From the structural r efinements of the new Laves phase it was further suggested that hafniu m formed a solid solution on the A-element site with one of the lighte r atoms, probably titanium. Nickel was found on the two B-element site s, mixed with a light atom, probably vanadium.