Microstructures of Directionally Solidified NbTiFe Alloy and Its Hydrogen Permeation Properties in the Presence of HS.

Currently, the main limitations of Pd-coated Nb-TiFe dual-phase alloys include insufficient hydrogen permeability, susceptibility to hydrogen embrittlement (HE), and poor tolerance of HS poisoning. To address these issues, this study proposes a series of improvements. First, a novel NbTiFe alloy composed of a well-aligned Nb-TiFe eutectic was successfully prepared using directional solidification (DS) technology. After deposition with a Pd catalytic layer, this alloy exhibits high hydrogen permeability of 3.71 × 10 mol H m s Pa at 673 K, which is 1.4 times greater than that of the as-cast counterpart. Second, to improve the HS corrosion resistance, a new PdAu catalytic layer was deposited on the surface using a multi-target magnetic control sputtering system. Upon testing in a 100 ppm H/HS mixture, this membrane exhibited better resistance to bulk sulfidation and a higher permeance recovery (ca. 58%) compared to pure Pd-coated membrane. This improvement is primarily due to the lower adsorption energies of the former with HS, which hinders the formation of bulk PdS. Finally, the composition region of the Pd-Au catalytic membrane with high comprehensive performance was determined for the first time, revealing that optimal performance occurs at around 12-18 at.% Au. This finding explains how this composition maintains a balance between high H permeability and excellent sulfur resistance. The significance of this study lies in its practical solutions for simultaneously improving hydrogen permeability and resistance to HS poisoning in Nb-based composite membranes.