Hydrogen Diffusivity and Permeability In Pd50-xTi50(Cr, Fe)x Alloys
Hydrogen diffusivity (D) and permeability (q) in Pd50-xTi50(Cr, Fe)x alloys were measured at temperature range between 570 and 770 K. During a heating measurement of Pd47Ti50Cr3 alloy, both D and q abruptly increased by factors of 5 and 2, respectively, at 712 K, with a phase transformation from B19 to B2 structures. However, q was far smaller than those in pure bcc metals (eg. V, Nb and Ta), where the hydrogen atoms occupy the tetrahedral interstitial sites. A first-principles calculation revealed that hydrogen atoms occupy the octahedral interstitial sites in Pd50Ti50 with B2 structure. It is concluded that the small hydrogen diffusivity in B2 Pd50-xTi50(Cr, Fe)x alloys is due to the long distance hydrogen jump and the resultant high activation energy for the diffusion.
Young Won Chang, Nack J. Kim and Chong Soo Lee
O. Yoshinari and D. Itoh, "Hydrogen Diffusivity and Permeability In Pd50-xTi50(Cr, Fe)x Alloys", Materials Science Forum, Vols. 561-565, pp. 2353-2356, 2007