engleski

A study of structural and thermodynamic properties of the YNi_5_-_xAl_x - hydrogen system

Alloys of the composition YNi5-xAlx were prepared and studied by means of X-ray powder diffraction. It was found that the hexagonal symmetry of YNi5 (space group P6/mmm), CaCu5 type is retained up to the composition YNi3Al2. However, beyond this composition and up to YNi2Al3 there also exists a ternary single phase region, but with a hexagonal structure of the YCo3Ga2 type (space group P6/mmm). It was found that all ternary alloys having the CaCu5 structure react readily with hydrogen and absorb between 1.85 and 3.96 hydrogen atoms per alloy formula unit at room temperature. Binary YNi5 as well as the remaining ternary alloys do not exhibit any significant absorption of hydrogen up to 673 K and 15 MPa of hydrogen. At room temperature the hydrogen capacity and the equilibrium pressure decrease with increasing content of aluminium. The entalphy and the entropy have been extracted for the systems that exhibit an equilibrium pressure plateau.

yttrium-nickel-aluminium alloys; hydrogen sorption; crystal structure

nije evidentirano