Phase diagram and thermodynamic parameters of the quasibinary interstitial alloy Fe0.5Ti0.5Hxin equilibrium with hydrogen gas

Abstract

Heats of absorption and desorption of FeTi in equilibrium with hydrogen were determined in a heat flow calorimeter together with pressure-composition isotherms at 274, 298, 314 and 344K in the composition range of Fe_0.5Ti_0.5H_x for 01/₂ ln (p(H₂))-2-554 K/T (endothermic solution) where p(H₂) is measured in bar. The plateau pressure for the coexistence of the gas phase wth the two hydride phases alpha and beta in the range 0alpha beta )=4.8-1257 K/T; the plateau pressure for the coexistence region ( beta + gamma ) in the range 0.5beta gamma )=6.5-1571 K/T. Very high exothermal heats of reaction observed at low concentrations (Fe_0.5Ti_0.5H_{x) are ascribed to adsorption effects at the surface of the powder (<10 mu m) used for the samples.}