Analysis of pressure-composition-isotherms for design of non-Pd-based alloy membranes with high hydrogen permeability and strong resistance to hydrogen embrittlement

The hydrogen permeability of Pd-27 mol%Ag alloy membrane has been analyzed in view of the new description of hydrogen permeation based on hydrogen chemical potential. The hydrogen flux is consistently proportional to the PCT factor, fPCT, which reflects the shape of the corresponding pressure-composition-isotherm (PCT curve), regardless of whether hydrogen solubility is expressed in a format of the Sievert's law or not. From the two points of the PCT factor, fPCT, and DBTC (the ductile-to-brittle transition hydrogen concentration), the concept for alloy design of non-Pd-based alloy membranes is obtained. As an example, V-9 mol%Al alloy is designed for applied temperature and pressure condition. For this condition, this alloy membrane possesses excellent hydrogen permeability with strong resistance to hydrogen embrittlement.