Alloy Of Tife Hydrogen Storage Properties

In the first part of the paper the importance and development of hydrogen energy, various means and mechanisms of hydrogen storage, especially the applications of metallic hydrides are reviewed generally, then hydrogen storage performance, the mechanisms of activation characteristics and important modification methods for improvement of hydrogen storage ability of TiFe alloys such as alloying, chemical treatment of surface are discussed in detail. Since alloying with other elements is one of the most effective and economical methods to improve the activation characteristics and hydrogen storage capabilities of TiFe alloy, the addition of LaNi5 to Ti12Fe by alloying was investigated. Then hydrogen storage performance of the non-stoichiometrical quatemionic Ti12Fe+xwt% LaNi5 type alloys was evaluated systematically. The results of study show that hydrogen storage properties of the alloys, such as the initial activation behavior and the hydrogen storage capacity, are influenced by the LaNi, content in the alloy. Among all the alloys studied, Ti1 2Fe?wt%LaNi5 has the best overall hydrogen storage performance, which can be hydrogenated at the temperature of 353K and the pressure of 3.5MPa after a short period of incubation, which is only 12 minutes. The hydrogen storage capacity of the alloy reaches 1 87m1/g at 293K, and hydrogen desorption capacity is 173.7ml/g at 3 33K. The thermodynamics parameters of Ti1 2Fe+xwt% LaNi5 and Ti1 2Fe+zwt%Ni alloys, su~h~ as A H0 A S0, were calculated according to Van Hoff equation. The XRD results show that excessive Ti in Ti1 2Fe+xwt% LaNi5 alloy exists as f3-Ti phase, and no LaNi5 phase was detected. The crystallographic parameters of Ti1 2Fe+xwt% LaTh5 alloy increased with the increasing of LaNi5 content. The study of hydrogen absorption-desorption mechanisms of the alloys indicates that the activation characteristic of the alloys is related to the cracks in the TiFe matrix generated due to the volume expansion of 13-Ti and La inclusions as a result of preferential hydrogenation. The improvement of the activation characteristics could be attributed to the oxide-free surfaces, through which hydrogen can be absorbed readily, On the other hand, the existence of Ni in the alloy could be attributed to the catalysis of H2 to H atom, which reacted with clean surface of TiFe easily. The alloy will be activated after several hydrogen absorption-desorption cycles.