Synthesis, characterization and hydrogenation of [formula omitted][formula omitted] alloys

Abstract

Hydrogen storage properties and structural properties in ZrFe 2 - x Ni x ( x = 0.2 , 0.4 , 0.6 , 0.8 ) alloys, prepared by arc melting in argon atmosphere, have been investigated. Powder XRD study shows that the lattice constants and the unit cell volume of ZrFe 2 - x Ni x ( x = 0.2 , 0.4 , 0.6 , 0.8 ) alloys having C15 Laves phase cubic structure decreases with increasing Ni content due to the smaller atomic radius of Ni compared to Fe. Surface morphology and elemental composition of the alloys were investigated by SEM and EDX. Hydrogen absorption pressure–composition ( P – C ) isotherms were investigated in the ranges 303 K ⩽ T ⩽ 373 K and 0.5 bar ⩽ P ⩽ 50 bar using a Sievert type apparatus. The P – C isotherms show the single plateau region in the temperature and pressure range studied. The plateau pressure increases with increasing Ni content for a given temperature. The entropy and enthalpy of dissolved hydrogen in ZrFe 2 - x Ni x – H ( x = 0.2 , 0.4 , 0.6 , 0.8 ) have been calculated by means of the vant Hoff plot and the variation of these parameters with hydrogen content is discussed with respect to the existence of α , α + β , and β phase regions in the P – C isotherms.