Design and characterizations of novel Nb-ZrCo hydrogen permeation alloys for hydrogen separation applications

Novel Nb–ZrCo hydrogen permeable alloys are developed as potential membrane materials for hydrogen separation applications. Microstructures, hydrogen permeation behavior and the resistance to hydrogen embrittlement of NbxZr(95-x)/2Co(105-x)/2 (x = 15 … 40) alloys are studied. Three different microstructures are found in these alloys, particularly (a) the primary ZrCo phase and eutectic {bcc-(Nb, Zr) + B2-ZrCo} for x 25. Alloys with Nb content between 20 and 30 at.% present higher permeation results. Increase in Nb content lead to higher hydrogen permeability (Φ), but poorer embrittlement resistance, which can be attributed to an increase in hydrogen solubility. Nb25Zr35Co40 exhibits an appropriate balance between hydrogen permeability and embrittlement resistance. Permeability is improved apparently and hydrogen embrittlement resistance is also further strengthened for directionally solidified (DS) Nb25Zr35Co40, which is mainly attributed to a decrease in hydrogen solubility and the significant increment of hydrogen diffusivity. The present work demonstrates that the newly developed alloys could be used as potential candidate for hydrogen separation applications. •A new family of metallic hydrogen permeation membranes was developed.•A new compositional window for hydrogen permeable Nb-ZrCo alloys is established.•DS Nb25Zr35Co40 exhibits a substantial enhancement of hydrogen permeability.•Nb25Zr35Co40 is promising to make high-performance membranes for H2 separation.