On the structural and thermodynamic properties of the DyNi_5-xAl_x-hydrogen system

Abstract

A structural and thermodynamic study of the DyNi5-xAlx-hydrogen system has been performed. It was found that the hexagonal crystal structure of the prototype compound DyNi5(CaCu5 type; space group, P6/mmm) exists up to DyNi3Al2. Beyond this composition and up to DyNi2Al3 another related hexagonal structure (YCo3Ga2 type; space group, P6/mmm) is stable. All alloys have been exposed to hydrogen gas at pressures up to 15 MPa and temperatures between 77 and 700 K. Under these conditions, ternary alloys having the CaCu5 structure react with hydrogen. Their crystal structures remain the same but the hydrogen uptake increases the unit-cell volume by up to 13%. The remaining ternary alloys as well as the binary DyNi5 do not exhibit any significant hydrogen absorption. The pressure-composition isotherms were measured. The entropy and the heat of formation have been extracted for systems that exhibit an equilibrium pressure plateau. It was found that the hydrogen capacity at ambient temperature and the equilibrium pressure decrease with the increasing content of aluminium.

Hydrogenation and dehydrogenation properties for DyNi5–H system

“…With respect to AB 5 -type Dy-based ternary intermetallic compounds, Sorgic and co-workers [5][6][7][8] In our previous report [9], we studied the P-C isotherms of R H Ni 5 -H systems (R H = Gd, Tb, and Dy) using a modified Sieverts' apparatus up to 35 MPa. We found characteristic P-C isotherms for TbNi 5 -H and DyNi 5 -H systems in that during dehydrogenation another plateau is present at relatively low hydrogen content.…”

Neutron diffraction, magnetic, and transport studies ofNdNi4Al

“…3,4 The case of RϭGd, Dy, and Er was also addressed. [5][6][7] Our interest in the RNi 4 Al series is a consequence of our previous wide research on RNi 4 B compounds. [8][9][10] In this paper we present joint results on NdNi 4 Al, including dc magnetization, ac susceptibility, neutron diffraction, and electrical resistivity measurements.…”

Magnetic and electronic properties of the LaNi5 xAlxsystem

“…Many substitutions were made, particularly on Ni sites, in order to analyse the hydrogen storage capacity, the plateau pressure and the kinetics [4][5][6]. In this context, the crystal structures of RNi 5−x Al x with R = Nd, Gd [5], Er [6], Dy [7] were studied. It was shown that for x < 2 the pseudo-binary systems form solid solutions having hexagonal CaCu 5 -type structure (P6/mmm space group).…”