Some physical aspects of hydrogen behaviour in the H-Storage bcc alloys Ti 35V xCr 65− x, Ti 40V xMn 50− xCr 10 and Ti xCr 97.5− xMo 2.5

Abstract

Hydrogen absorption/desorption has been investigated in the three series of solid solution bcc alloys Ti 35V x Cr 65− x ( x = 18,22), Ti 40V x Mn 50− x Cr 10 ( x = 32,36) and Ti x Cr 97.5− x Mo 2.5 ( x = 43,46). It has been found that the H absorption at pressures smaller than 1 bar can only occur after elimination of the oxide films by heating the alloys to temperatures higher than 600 K. Hydrogen desorption from pre-loaded materials ( n H = H/Me ≤ 0.27) takes place on heating at much lower temperatures in the Ti 40V x Mn 50− x Cr 10 and Ti 35V x Cr 65− x than in the Ti x Cr 97.5− x Mo 2.5 alloys. The H diffusion parameters W and D o deduced from high temperature (>450 K) absorption experiments are as follows: W = 0.318 ± 0.005 eV, D o = (4 ± 1)×10 −7 m 2/s for Ti 40V x Mn 50− x Cr 10; W = 0.32 ± 0.02 eV, D o = (3 ± 2)×10 −7 m 2/s for Ti 35V x Cr 65− x ; W = 0.79 ± 0.06 eV, D o = (4 ± 2)×10 −8 m 2/s for Ti x Cr 97.5− x Mo 2.5. The higher value of the activation energy for H diffusion in Mo containing alloys is most likely due to remarkable attractive interactions between H and Mo atoms.