Microstructure and hydrogen permeation of cold rolled and annealed Nb40Ti30Ni30 alloy

Microstructural stability and its effect on hydrogen permeability in equiaxed and directionally solidified eutectic Nb 30 Ti 35 Co 35 alloys

“…The highest apparent diffusivity is expected if all the bcc-Nb lamellae in the eutectic microstructure are contiguously arranged and perpendicular to the membrane surface. This has been testified by experimental results [10,13] and quantitatively by a rule of mixture based on effective medium theory [15]. In the present case, it is also found that a higher apparent hydrogen diffusion exists in the DS Nb 30 Ti 35 Co 35 samples compared to the EX samples, because the former have more contiguous bcc-(Nb, Ti) regions penetrating the membrane.…”

“…1(b). Such a microstructural change during annealing is attributed to the simultaneous coarsening of the both phases [15]. At the boundaries of the equiaxed eutectic grains in the as-cast state, a transient microstructure from lamellar to rod-shaped commonly appears [10].…”

Hydrogen permeability and microstructure of rapidly quenched Nb–TiNi alloys

“…The microstructure of the arc melted Nb 40 Ti 30 Ni 30 alloy, consisting of the primary (Nb, Ti) phase and the eutectic {TiNi + (Nb, Ti)} phase, turns into the granule (Nb, Ti) phase embedded in the TiNi phase by cold rolling and subsequent annealing. However, two different sizes of the (Nb, Ti) phase are observed, that is, primary one of 10-20 m and precipitates of 2-5 m formed in the eutectic phase, respectively [3]. The value of ˚6 73 K for the conventionally solidified Nb 40 Ti 30 Ni 30 alloy is 1.9 × 10 −8 (molH 2 /m/s/Pa 0.5 ) in the as-cast state, and it reduces to 0.6 × 10 −8 (molH 2 /m/s/Pa 0.5 ) by 50% rolling.…”

“…However, since Pd is very expensive and a rare metal, which give rise to the high cost of hydrogen production, alternative hydrogen permeation alloys containing less or no Pd are strongly desired. Recently, we have found out that Nb-TiNi alloys consisting of the bcc-(Nb, Ti) solid solution and the B2-TiNi intermetallic compound show large ductility, large rolling workability, high hydrogen permeability and large resistance to hydrogen embrittlement [2,3]. Such experimental results indicate that the Nb-TiNi alloys are anticipated to be potential non-Pd based hydrogen permeation alloys.…”

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

“…As we all know, palladium is expensive and not suitable for large-scale industrial application as hydrogen permeation alloy for separation and purification of hydrogen gas; therefore, palladiumbased alloys are not currently preferred for hydrogen purification [1][2][3][4], but niobium-based hydrogen permeation alloys are of the optimal choice [5]. Nb-Ti-Ni and Nb-Zr-Ni alloys have already been investigated [1,5] and Nb-Hf-Ni alloys are also studied [6].…”