Effect of Hf/Ni ratio on microstructure and hydrogen permeation of Nb–Hf–Ni ternary alloys

Shi, Feng; Song, Xiping

doi:10.1016/j.jallcom.2010.12.072

Cited by 13 publications

(9 citation statements)

References 8 publications

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“…The slope of each straight line in the plot of J Â L vs. DP 0.5 corresponds to the hydrogen permeability (F). Such a method is usually used to determine F for other alloys such as NbeTieNi [3,4], NbeTieCo [5] and NbeHfeNi [6] etc. Further on the basis of F ¼ D Â K, the value of D for each sample can be derived.…”

Section: Resultsmentioning

confidence: 99%

“…However, since Pd is too expensive and a rare metal, much of the current research [3e7] on hydrogen permeable alloys is focused on Nb-based alloys containing less or no Pd, such as NbeTiNi [3,4], NbeTiCo [5] and NbeHfNi [6] etc. These alloys generally contain a multi-phase microstructure containing a primary BCC-Nb solid-solution phase and eutectic phases.…”

Section: Introductionmentioning

confidence: 99%

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Changes in microstructures and hydrogen permeability of Nb30Hf35Co35 eutectic alloy membranes by annealing

Yan

Sun

et al. 2016

International Journal of Hydrogen Energy

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a b s t r a c tChanges in microstructures and hydrogen permeability by long-time annealing (168 h) at 1073, 1173 and 1173 K for eutectic Nb 30 Hf 35 Co 35 alloy are investigated. After annealing at 1073 K and 1173 K for 168 h, the fully lamellar eutectic microstructure in as-cast state has disappeared and turned to a duplex microstructure. Correspondingly, the hydrogen permeability at 673 K, decreases from 3.3 Â 10 À8 to (0.82e1.5) Â 10 À8 mol H 2 m À1 s À1 Pa À0.5 after annealing. The annealed (a-) sample at 1273 K for 168 h is brittle and susceptible to hydrogen embrittlement that results from the appearance of the additional Hf 2 Co phase. The hydrogen solubility coefficient (K) for each a-samples at 673 K is almost the same as that for the as-cast sample, while the hydrogen diffusion coefficient (D) for the a-samples are (1/4e1/2) times than that for the as-cast one. It is thus concluded that the lower permeability by annealing for eutectic Nb 30 Hf 35 Co 35 is mainly attributed to the significant reduction of hydrogen diffusivity after annealing.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Changes in microstructures and hydrogen permeability of Nb30Hf35Co35 eutectic alloy membranes by annealing

Yan

Sun

et al. 2016

International Journal of Hydrogen Energy

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“…1 and 2. It should be noted that these intermetallic phases are inherently brittle and cannot be eliminated by annealing [39]. Further evaluation of ductility is needed for alloys containing these phases.…”

Section: Microstructuresmentioning

confidence: 99%

Changes in microstructure, ductility and hydrogen permeability of Nb–(Ti, Hf)Ni alloy membranes by the substitution of Ti by Hf

Liu

Chen

et al. 2015

Journal of Membrane Science

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“…Nb-based alloys, such as Nb-TiNi [1][2][3][4][5][6], Nb-TiCo [7][8] and Nb-HfNi [9][10][11] etc, are ones of the most promising materials for hydrogen permeable membrane to be substituted for currently used Pd-Ag alloys, because they possess higher hydrogen permeability than Pd-based alloys [12][13][14][15]. These alloys generally contain a multi-phase microstructure containing a primary BCC-Nb solid-solution phase and eutectic phases.…”

Section: Introductionmentioning

confidence: 99%

“…A large J can be obtained not only by operating a thin alloy membrane under a large pressure difference (small L) but also by using a high-performance hydrogen permeation alloy (large Φ). Although several special processing methods such as melt-spinning technique [5,[21][22][23] and rolling followed by annealing [24][25][26] can be used to fabricate a thinner alloy membrane with the aim to obtain larger J, composition design with the aim to improve the immanent hydrogen permeability of these alloys is also important [1,7,8,10,12,18,[27][28][29][30]. Obviously, finding favorable composition to tailor the above multi-phase microstructure and hydrogen permeability for higher Φ value in these alloy systems is the first issue to be addressed for defining their usefulness in hydrogen permeation.…”

Section: Introductionmentioning

confidence: 99%

Changes in microstructure, solidification path and hydrogen permeability of Nb–Hf–Co alloy by adjusting Hf/Co ratio

Yan

Sun

et al. 2016

International Journal of Hydrogen Energy

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The effect of Hf/Co ratio on microstructure, solidification path and hydrogen permeability of as-cast Nb 40 Hf 30+x Co 30-x and Nb 35 Hf 32.5+x Co 32.5-x (x=-2, 0, 2, 4) alloys is investigated. The above two series of alloys mainly consist of the primary BCC-(Nb, Hf) and the eutectic {BCC-(Nb, Hf) + B f-HfCo} phases, while Nb 40 Hf 34 Co 26 alloy additionally contains small fractions of the Hf 2 Co phase that results from a ternary eutectic reaction. Increase of Hf/Co ratio induces higher fraction of primary BCC-(Nb, Hf) and Hf 2 Co phases. Two kinds of solidification paths are found in this two series of alloys, particularly [L→BCC-(Nb,Hf)]→[L→BCC-(Nb,Hf) + B f-HfCo] and [L→BCC-(Nb,Hf)]→[L→BCC-(Nb, Hf)+B f-HfCo]→[L→BCC-(Nb, Hf) + B f-HfCo+ Hf 2 Co]. The permeability increases with increasing Hf/Co ratio and increasing volume fraction of the primary BCC-(Nb, Hf) phase. Nb 40 Hf 32 Co 28 (x = 2) exhibits a high hydrogen permeability of 5.21×10 −8 mol H 2 m-1 s-1 Pa-1/2 at 673 K and excellent durability in hydrogen permeation (~72 h), which becomes superior to that of the Nb 40 Hf 30 Co 30 previously reported to be the best in the Nb-Hf-Co alloy series. The present work demonstrates that the hydrogen permeability of this alloy series can be optimized by appropriately adjusting the Hf/Co ratio for a given niobium content.

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Effect of Hf/Ni ratio on microstructure and hydrogen permeation of Nb–Hf–Ni ternary alloys

Cited by 13 publications

References 8 publications

Changes in microstructures and hydrogen permeability of Nb30Hf35Co35 eutectic alloy membranes by annealing

Changes in microstructures and hydrogen permeability of Nb30Hf35Co35 eutectic alloy membranes by annealing

Changes in microstructure, ductility and hydrogen permeability of Nb–(Ti, Hf)Ni alloy membranes by the substitution of Ti by Hf

Changes in microstructure, solidification path and hydrogen permeability of Nb–Hf–Co alloy by adjusting Hf/Co ratio

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