MAXIMUM HYDROGEN STORAGE CAPACITY OF AMORPHOUS NI1-XZRX ALLOYS

Hydrogen uptake was studied by volumetric method at room temperature f or amorphous and crystalline Ni1-xZrx alloys (x = 0.33; 0.36; 0.39; 0. 41; 0.45 and 0.5). Contrary to expectation, there is no difference in the storage capacity of nanocrystalline (obtained by heat treatment of an amorphous precursor) and microcrystalline (obtained from the ingot material) states. There is a crossover in the plots of the maximal hy drogen content versus Zr concentration at about 40 at% Zr below which the amorphous, and above which the crystalline, state stores more hydr ogen. In connection to the maximum storage, the partial molar volume o f hydrogen has been determined from the shift of the amorphous X-ray d iffraction peak. The volume increase due to hydrogen shows a minimum a t about 50 at% Zr. Such extremes at about 50 at% Zr have been publishe d earlier for other physical parameters as well. Copyright (C) 1996 In ternational Association for Hydrogen Energy