Thermodynamics and structural aspects of hydrogen absorption in alloys

The hydrogen storage properties of Zr 1 - x Cr x Fe 2 ( x = 0.2 , 0.3, 0.4, 0.5) alloys have been obtained in the pressure and temperature range of 0.5 ⩽ P ⩽ 60 bar and 303 K ⩽ T ⩽ 373 K . The alloys have been characterized by XRD and SEM. The results show that all the alloys were having C14 laves phase hexagonal structure. The substitution of Cr in Zr site leads to the contraction of their lattice. The P –C– T isotherms of the alloys showed the existence of α , α + β , and β regions. The maximum hydrogen intake capacity is around 3.131 H/f.u. at 303 K and at 48 bar pressure for Zr 0.8 Cr 0.2 Fe 2 alloy. The average relative partial molar enthalpy and entropy of hydrogen at plateau region have been calculated for all the alloys. The presence of α , α + β , and β region as seen in P –C isotherm has been confirmed by the variation of thermodynamical parameters with hydrogen content.