Role of defect structure on hydrogenation properties of Zr0.9Ti0.1V2 alloy

The pseudobinary Zr0.9Ti0.1V2 compound was prepared by induction melting method. The microstructure and phase compositions were examined by the scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Hydrogen absorption pressure composition isotherms (P-C isotherms) were investigated by pressure reduction method using Sievert apparatus at temperature ranging from 673 to 823 K. The compositional homogeneity of the alloy was achieved under the homogenizing treatment at 1373 K for 100 h. Twin defects with {111}<022> orientation relationship were observed in the Zr0.9Ti0.1V2 annealed at 1373 K for 100 h. The phase compositions of the annealed Zr0.9Ti0.1V2 alloy could be attributed to ZrV2 Laves phase and V BCC solid solution. After hydrogenation, the alloy hydrides were consisted of ZrV2H3.6 and V4H2.88. Titanium substitution in the Zr0.9Ti0.1V2 alloy induced the formation of twin defect structures and the multiphase consisting of Laves (C15 type) related with BCC solid solution phases. The especial phase compositions and structures in the alloy were favorable to decrease the equilibrium pressure and improve the hydrogen absorption kinetics due to the twin defects in Zr0.9Ti0.1V2 comparing with the primary ZrV2 alloy. The desorption hysteresis could be decreased to a certain extent in the Ti-doped alloy under the experimental condition. V-based BCC phase in the Zr0.9Ti0.1V2 alloy could improve hydrogen absorption and desorption properties by an autocatalytic mechanism.