Structural and Kinetic Hydrogen Sorption Properties of Zr0.8Ti0.2Co Alloy Prepared by Ball Milling.

Hui He,Huaqin Kou,Jingwen Ba,Tao Tang,Guanghui Zhang,Zhiyong Huang,Ge Sang,Meng Liu,Wenhua Luo

doi:10.1155/2018/5736742

Abstract

The effects of ball milling on the hydrogen sorption kinetics and microstructure of Zr0.8Ti0.2Co have been systematically studied. Kinetic measurements show that the hydrogenation rate and amount of Zr0.8Ti0.2Co decrease with increasing the ball milling time. However, the dehydrogenation rate accelerates as the ball milling time increases. Meanwhile, the disproportionation of Zr0.8Ti0.2Co 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 Zr0.8Ti0.2Co 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 Zr0.8Ti0.2Co 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 Zr0.8Ti0.2Co.

Highlights

Because of the rapid decrease of fossil fuels and the increasingly serious environmental pollution in recent years, developing a clean and renewable energy has become an urgent task for mankind [1]
We focused on the effects of ball milling on microstructure and kinetic hydrogen sorption properties of Zr0.8Ti0.2Co alloy
It is readily discernible that the disproportionation rate and extent monotonously grow with increasing ball milling time. These results suggest that the dehydrogenation rate and the disproportionation rate of Zr0.8Ti0.2Co can be quickened by ball milling, the mechanism of which will be discussed below

Summary

Introduction

Because of the rapid decrease of fossil fuels and the increasingly serious environmental pollution in recent years, developing a clean and renewable energy has become an urgent task for mankind [1]. Its serious degradation of hydrogen storage properties during the hydrogen sorption cycle obstructs its Scanning wide application, resulting from the concomitant hydrogeninduced disproportionation reaction that happened above 573 K during hydrogen sorption process shown as follows[15,16,17,18]: 2ZrCo + H2 󳨀→ ZrH2 + ZrCo2. Hydrogen sorption cycles do not produce separated ZrCo, TiCo, and ZrH2, suggesting that the antidisproportionation property of ZrCo alloy is improved by Ti substitution. It has extensively shown that mechanical ball milling is an effective technique for improving the kinetic property of hydrogen storage materials [33,34,35,36]. The effects of ball milling on the hydrogen sorption kinetics and microstructure of ZrCo-based alloy have never been investigated. We focused on the effects of ball milling on microstructure and kinetic hydrogen sorption properties of Zr0.8Ti0.2Co alloy. Because study of kinetics is clearly beneficial to understanding of mechanism about hydrogen sorption process [20, 37, 38], kinetic analysis has been carried out for disproportionation of Zr0.8Ti0.2Co in this work

Experimental

Results and Discussion

Conclusion