HYDROGEN ABSORPTION CHARACTERISTICS OF SM2FE17 ALLOY

The hydrogen sorption properties of the Sm2Fe17 alloy were investigated with absorption and desorption measurements. A Sieverts' type apparatus was used with powder samples at temperatures between 299 and 773 K and pressures between 10(3) and 7 . 10(6) Pa. At that temperatures and pressures, the pressure-concentration isotherms (p-c-T relations) in the equilibrium state showed no sign of a distinct hydride phase within hydrogen concentrations of Y < 4.5 in Sm2Fe17Hy. The isotherms were fitted with a model of an ideal interstitial solution to get thermodynamic data. The reaction kinetics of hydrogen absorption at different pressures indicates that the transition of physisorbed hydrogen (H-2) to chemisorbed hydrogen (2H) may be the rate limiting step of this reaction.