Hydrogen transport through the V-Cr-Al alloys: hydrogen solution, permeation and thermal-stability

Hydrogen permeable V-Cr-Al alloys have been designed based on the lattice matching principle. To elucidate alloying effects of Cr and Al, the hydrogen solubility and hydrogen permeation flux have been characterized at temperatures between 523 and 673 K. V₉₀Cr₅Al₅ exhibits a highly reduced hydrogen solubility, which contributes to enhanced resistance towards hydrogen embrittlement, at the same time maintaining the high permeability as pure vanadium at 673 K. The stability of the V₉₀Cr₅Al₅ membrane during hydrogen permeation tests at several temperatures has been characterized: V₉₀Cr₅Al₅ shows a constant hydrogen permeation flux up to 500 h at 573 K. A small drop in permeation flux (J×d) by 4% was observed at 623 K after 500 h, i.e. from 1.35 × 10⁻⁴ to 1.30 × 10⁻⁴ mol H₂ m⁻¹s⁻¹. Serious degradation in the hydrogen permeation flux during the long-term test was observed at the temperatures above 673 K. This is attributed to the formation of a new barrier layer caused by the interdiffusion between Pd and V₉₀Cr₅Al₅.