Microstructures of Directionally Solidified Nb<sub>15</sub>Ti<sub>55</sub>Fe<sub>30</sub> Alloy and Its Hydrogen Permeation Properties in the Presence of H<sub>2</sub>S
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 H<sub>2</sub>S poisoning. To address these issues, this study proposes a series of improvements. First,...
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| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-12-01
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| Series: | Membranes |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2077-0375/14/12/253 |
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| Summary: | 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 H<sub>2</sub>S poisoning. To address these issues, this study proposes a series of improvements. First, a novel Nb<sub>15</sub>Ti<sub>55</sub>Fe<sub>30</sub> 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<sup>−8</sup> mol H<sub>2</sub> m<sup>−1</sup> s<sup>−1</sup> Pa<sup>−1/2</sup> at 673 K, which is 1.4 times greater than that of the as-cast counterpart. Second, to improve the H<sub>2</sub>S corrosion resistance, a new Pd<sub>88</sub>Au<sub>12</sub> catalytic layer was deposited on the surface using a multi-target magnetic control sputtering system. Upon testing in a 100 ppm H<sub>2</sub>/H<sub>2</sub>S 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 H<sub>2</sub>S, which hinders the formation of bulk Pd<sub>4</sub>S. 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<sub>2</sub> permeability and excellent sulfur resistance. The significance of this study lies in its practical solutions for simultaneously improving hydrogen permeability and resistance to H<sub>2</sub>S poisoning in Nb-based composite membranes. |
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| ISSN: | 2077-0375 |