TiCl3 and Ni-added Mg prepared by reactive mechanical grinding processing and comparison with Fe2O3 and Ni-added Mg

摘要

Metallic oxides are brittle and halides have low melting points. They are expected to increase the reaction rates of Mg with hydrogen when added. Samples with compositions of 95 wt% Mg+ 5 wt% TiCl3 (designated as Mg-5TiCl(3)), 90 wt% Mg+ 10 wt% TiCl3 (Mg-10TiCl(3)), and 80 wt% Mg+ 14 wt% Ni+ 6 wt% TiCl3 (Mg-14Ni-6TiCl(3)) were prepared by high-energy ball milling in hydrogen (reactive mechanical grinding). At the first cycle (n = 1), Mg-5TiCl(3) had the highest initial hydrogen uptake rate and the largest quantity of hydrogen absorbed for 60 min at 593 K in 12 bar H-2, followed by Mg-10TiCl(3) and Mg14Ni-6TiCl(3). Mg-5TiCl(3) had an effective hydrogen storage capacity (a quantity of hydrogen absorbed for 60 min) of about 6.3 wt% at n = 1. Mg-5TiCl(3) absorbed 4.84 wt% H for 5 min and 6.27 wt% H for 60 min. Decrease in the Mg proportion in Mg-14Ni-6TiCl(3), compared with those in Mg-5TiCl(3) and Mg-10TiCl(3), and the formation of Mg2Ni, with a lower hydrogen storage capacity than Mg, are thought to decrease the initial hydrogen uptake rate and the quantity of hydrogen absorbed for 60 min for Mg-14Ni-6TiCl(3). At n = 1, Mg-14Ni-6TiCl(3) has the highest initial hydrogen release rate at 593 K in 1.0 bar H-2, followed by Mg-10TiCl(3) and Mg-5TiCl(3). The Mg2Ni formed in Mg-14Ni-6TiCl(3) and the larger content of additives (favoring the nucleation of Mg-H solid solution) are believed to make Mg-14Ni-6TiCl(3) have the highest initial hydrogen release rate among these three samples. The hydrogen storage properties of Mg-14Ni-6TiCl(3) were compared with those of Fe2O3 and Niadded Mg, which were prepared under the conditions similar to those to prepare Mg-14Ni-6TiCl(3).