Thermodynamic investigation of the magnesium-hydrogen system

Thermodynamic properties of the magnesium hydride-magnesium system have bee n investigated using both calorimetric and equilibrium pressure measurement s. Based on calorimetric measurements, on average a satisfactory agreement between experimental and calculated enthalpy and entropy values for the for mation of MgH2 is achieved; systematic deviations are found only at higher temperatures (similar to 480 degrees C). Experimental determination of PCIs (absorption and desorption mode) has been carried out in the temperature r ange 403-520 degrees C, using Mg powders of different origin and particle s ize. According to measurements at 526 degrees C, a minor dependence of H-2 equilibrium pressure over MgH2 on the particle size of Mg powders used exis ts. (C) 1999 Elsevier Science S.A. All rights reserved.