Structural and Kinetic Hydrogen Sorption Properties of Zr(0.8)Ti(0.2)Co Alloy Prepared by Ball Milling

The effects of ball milling on the hydrogen sorption kinetics and microstructure of Zr(0.8)Ti(0.2)Co have been systematically studied. Kinetic measurements show that the hydrogenation rate and amount of Zr(0.8)Ti(0.2)Co decrease with increasing the ball milling time. However, the dehydrogenation rate accelerates as the ball milling time increases. Meanwhile, the disproportionation of Zr(0.8)Ti(0.2)Co speeds up after ball milling and the disproportionation kinetics is clearly inclined to be linear with time at 500°C. It is found from X-ray powder diffraction (XRD) results that the lattice parameter of Zr(0.8)Ti(0.2)Co gradually decreases from 3.164 Å to 3.153 Å when the ball milling time extends from 0 h to 8 h, which is mainly responsible for the hydrogen absorption/desorption behaviors. In addition, scanning electron microscope (SEM) images demonstrate that the morphology of Zr(0.8)Ti(0.2)Co has obviously changed after ball milling, which is closely related to the hydrogen absorption kinetics. Besides, high-resolution transmission electron microscopy (HRTEM) images show that a large number of disordered microstructures including amorphous regions and defects exist after ball milling, which also play an important role in hydrogen sorption performances. This work will provide some insights into the principles of how to further improve the hydrogen sorption kinetics and disproportionation property of Zr(0.8)Ti(0.2)Co.