Han Xingbo

Hydrogen Storage Properties of La1-xYxNi5-yAly Alloys

Abstract The feasibilities of La 1- x Y x Ni 5-y Al y alloys ( x =0.6, 0.7; y =0.1, 0.2) applied in metal hydride high-pressure compressor were investigated systematically in terms of the crystal structure, hydrogen absorption/desorption properties and pulverization resistance. XRD analyses show that all the investigated alloys present CaCu 5 type hexagonal structure and the unit cell volume decreases with the increase of Y, but increases with the increase of Al content. The pressure-composition isotherms and absorption kinetics were measured at 20, 30 and 40 °C by the volumetric method. Hydrogen absorption/desorption measurement reveals that Y and Al could effectively increase and decrease the equilibrium hydrogen pressure, respectively. They are ideal elements to adjust the equilibrium hydrogen pressure of LaNi 5 -based alloys without other remarkable negative influences. We think that the alloys could be matched as ‘alloy pairs’ and applied in a double-stage metal hydride compressor; the compressor could boost the feed hydrogen gas at room temperature from 2 MPa to 35∼40 MPa at 135∼155 °C.

Structures and Hydrogen Storage Properties of La1-xMgxNi4.25Al0.75 (x=0.0, 0.1, 0.2, 0.3) Alloys

Abstract La1-xMgxNi4.25Al0.75 (x=0.0, 0.1, 0.2, 0.3) hydrogen storage alloys were prepared by a three-step induction melting. Their crystal structures and hydrogen storage properties were investigated. Results show that alloys with x=0.0 and 0.1 contain a single LaNi4Al phase; however, those with x=0.2 and 0.3 are composed of LaNi4Al, (La, Mg)Ni3 and AlNi3 phases. With x increasing from 0.2 to 0.3, the abundances of the secondary phases and the plateau pressures in the pressure-composition isotherms are lifted significantly. Meanwhile, their hydrogen storage capacities are remarkably reduced. It is found that the alloy with x=0.1 possesses the fastest absorption kinetics compared to the others as well as a good hydrogen capacity and a low plateau pressure.