Hydrogen permeation characteristics of palladium-plated VNi alloy membranes

The hydrogen permeation characteristics of alloy membranes based on V-15 at.%Ni have been investigated in the temperature range 373–673 K. It has been found that palladium-coated V-15 at.%Ni alloy membranes exhibit good resistance to hydrogen embrittlement with a hydrogen permeability larger than that of a palladium membrane. The VNi alloy membrane did not exhibit any cracks even under an upstream hydrogen pressure of 0.2 MPa during the permeation test at 473 K. This revealed a conspicuous hydrogen trapping phenomenon below 473 K. The hydrogen permeability of the VNi alloy membrane increased as a result of adding 0.05 at.% of titanium, zirconium or yttrium, which was nearly equal to the amount of oxygen in the alloy; however, the hydrogen trapping phenomenon could not be eliminated by adding such deoxidizers. The trapping phenomenon could be markedly improved by removing the deformed layer of the alloy membrane before plating with palladium.