ON THE STRUCTURAL AND HYDROGEN DESORPTION PROPERTIES OF THE ZR(CR1-XNIX)2 ALLOYS

X-ray powder diffraction studies of the Zr(Cr1-xNix)2 system revealed that chromium can be replaced by nickel up to the composition Zr(Cr0.5Ni0.5)2 without changing the basic hexagonal MgZn2-type structure of ZrCr2. It was also found that all these alloys react readily with hydrogen to form hydrides having about 3.4 hydrogen atoms per formula unit under a hydrogen pressure of 0.81 MPa at room temperature. Pressure-composition hydrogen desorption isotherms were determined over the temperature range 296-473 K. In general, the dissociation equilibrium pressure increases with increasing nickel content; for example, at 353 K it rises from 5 kPa for the ZrCr2-H2 system to 50 kPa for the Zr(Cr0.5Ni0.5)2-H2 system. The unit cell volumes of the hydrides are about 21% larger than those of the corresponding alloys. © 1990.