engleski

ON STRUCTURAL AND HYDROGEN SORPTION PROPERTIES OF THE RENi5-XAlX (RE = Gd, Tb, Dy, Ho, Er AND Y) ALLOYS

The results of our studies on the crystal structure and hydrogen sorption properties of the RENi5-xAlx (RE = Gd, Tb, Dy, Ho, Er and Y) alloys are reviewed and discussed with respect to the kind of the rare earth metal and the aluminium content. In all the investigated systems it was found that the binary prototype structure (CaCu5 type) is preserved up to x=2. Beyond this composition a transformation into the YCo3Ga2 structure type occurs, whereby the later structure is stable for x3. It was also found that only ternary alloys with the CaCu5 structure react with hydrogen under pressures up to 15 MPa and temperatures between 77 and 700 K to form hydrides. The unit cell parameters of the alloys increase, while the alloy hydrogen capacity and the hydrogen equilibrium pressure decrease with the increased aluminium content. At a particular Ni/Al ratio the alloy unit cell parameters decrease, as does their hydride stability, while the hydrogen capacity generally decreases with the increasing atomic number of the RE. The alloys containing Y fit well with the above trends. However, some minor deviations were observed and are pointed out.

Hydrogen storage materials; Intermetallics

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