Synergistic effect between Laves phase and Zr-Ni phases in Zr(MnVNi)2 hydrogen storage alloys
(1.Department of Applied Chemistry, Zhejiang University of Technology, Hangzhou 310014, P.R.China;
2.Department of Materials Science and Engineering,Zhejiang University, Hangzhou 310027, P.R.China)
2.Department of Materials Science and Engineering,Zhejiang University, Hangzhou 310027, P.R.China)
Abstract: The effect of annealing treatment on the crystal structure and electrochemical properties of Zr (Mn0.25V0.20Ni0.55)2 and Zr(Mn0.05V0.40Ni0.55)2 hydrogen storage alloys was investigated by means of XRD analysis and electrochemical tests. The results of XRD analysis showed that the as-cast alloys consist of C15, C14 type Laves phase and Zr9Ni11 and ZrNi phases. The composition of alloys homogenized after annealing treatment. The C15 type Laves phase is still stable while the Zr9Ni11 and ZrNi phases decompose and C14 phase disappears partially. The final stable structure of the alloys was a mixture phase of C15 and C14 type Laves phases. The results of the electrochemical tests showed that the discharge capacity and the properties of activation as well as high-rate dischargeability are all decreased after annealing treatment. The exchange current density decreases in some degree too.
Key words: annealing treatment; hydrogen storage alloys; crystal structure; electrochemical properties;synergistic effect