Hydrogen permeability and mechanical properties of NiNb-M (M = Sn, Ti and Zr) amorphous metallic membranes

• NiNb-M(M = Sn, Ti and Zr) membranes were synthesized in amorphous state.
• Nanoindentation indicated that H2 charging changes membranes’ mechanical properties.
• Hydrogen permeability decreased during test while amorphous structure maintained.
• Free volume occupied by hydrogen can explain the permeability decrease during test.
• The enthalpy of hydride formation of elements influences the hydrogen permeability.

In this paper, we report on the hydrogen permeability at 673 K of 45-μm thick splat-quenched Ni60Nb35M5 (M = Sn, Ti and Zr) amorphous metallic membranes. Changes in mechanical properties, induced by hydrogen, were evaluated by nanoindentation. The effect of different elemental substitutions on both the hydrogen permeability and the thermal stability are discussed. Membrane crystalline structure was probed with X-ray diffraction and membrane thermal properties were analyzed with differential scanning calorimetry. The Young’s modulus and hardness changes of the membranes were measured by nanoindentation. All of these ternary Ni–Nb membranes maintain their amorphous structure after 24 h of hydrogen permeability testing at 673 K. The Ni60Nb35Zr5 alloy membranes exhibited a hydrogen permeability of 10−10 mol m−1 s−1 Pa−0.5, the maximum of the three compositions tested. The hydrogen permeability declined slightly with time during the testing. Overall the amorphous metallic membranes were thermally stable and maintained their amorphous structure. A decrease in free volume is hypothesized to be the reason for i) the increase of Young’s modulus and hardness; ii) hydrogen permeability decrease over time.