Electrochemical hydrogen storage property of NiTi alloys with different Ti content prepared by mechanical alloying

Abstract

In this paper, three kinds of TiNi alloys, TiNi,Ti₃Ni₂,Ti₂Ni, were prepared by mechanical alloying (MA). The procedures of phase evolution during MA are as follows: elements Ni and Ti → formation of NiTi alloy → amorphization of alloy. For milling 70 h, all three TiNi alloys show typical amorphous character. Oxygen will prevent the amorphization process of TiNi alloys during MA process. Crystallization of amorphous TiNi will take place at about 530 °C. For TiNi, Ti₃Ni₂, Ti₂Ni, the main crystalline phase is TiNi. Ti₂Ni + TiNi, Ti₂Ni, respectively. For amorphous TiNi base alloys, the initial capacity of Ti₂Ni, Ti₃Ni₂ is higher than TiNi. But it decreases gradually with the charge-discharge process. Capacity of TiNi increases with the cycle process. The capacity of crystallized TiNi alloys is higher than amorphous ones. The initial capacity of Ti₂Ni can get 289 mAh/g which is double than amorphous Ti₂Ni. But it decreases sharply with the charge-discharge process. After 80 cycle, capacity of Ti₂Ni is lower than that of TiNi. As same as amorphous TiNi, capacity of crystallized ones increases gradually with the charge-discharge process.