Hydrogen uptake characteristics of mischmetal based alloy

Hydrogen storage properties of Mm(39.2)Ni(42.1)Mn(4.9)Al(1.25)Co(10.2)Fe(2.35) alloy have been systematically studied in the present work. An attempt is made to relate the content of hydrogen with change in resistance. It is found that the resistance of material increases with the increase in value of HIM due to hydrogen absorption. Pressure composition (P-C-T) isotherm using water displacement method has been investigated in the temperature and pressure ranges of 308 <= T <= 338 K and 0.5 <= P <= 10 bar, respectively. The P-C isotherms show the presence of two single (x and P regions one mixed alpha + beta phase. The maximum H (wt%) was found to be around 1.53 at 308 K and around 6 bar. Since enthalpy is an index of thermochernical stability of metal hydride the thermo dynamical parameters viz., the relative partial molar enthalpy (Delta H) and relative partial molar entropy (Delta S) of dissolved hydrogen have been calculated by plotting the Van't Hoff plot. The variation of Delta H and AS with the hydrogen concentration confirm the phase boundaries. (c) 2006 Elsevier B.V. All rights reserved.