We prepared the melt-spun (Ni 0:6 Nb 0:4 ) 100Àx Zr x (x ¼ 0 to 40 at%) and other amorphous alloy membranes and examined the permeation of hydrogen through those alloy membranes. The interatomic spacing in the Ni-Nb-Zr amorphous structure increased with increasing Zr content. The crystallization temperature of the Ni-Nb-Zr amorphous alloys decreased with increasing Zr content. The hydrogen flow increased with an increase of the temperature or the difference in the square-roots of hydrogen pressures across the membrane, Á ffiffiffi p p . At relatively higher temperature up to 673 K or at relatively higher hydrogen pressure difference, Á ffiffiffi p p up to 550 Pa 1=2 , the hydrogen flow was more strictly proportional to Á ffiffiffi p p . This indicates that the diffusion of hydrogen through the membrane is a rate-controlling factor for hydrogen permeation.The permeability of the Ni-Nb-Zr amorphous alloys was strongly dependent on alloy compositions and increased with increasing Zr content. However, it was difficult to investigate the hydrogen permeability of the (Ni 0:6 Nb 0:4 ) 60 Zr 40 amorphous alloy in this work due to the embrittlement during the measurement. The maximum hydrogen permeability was 1:3 Â 10 À8 (molÁm À1 Ás À1 ÁPa À1=2 ) at 673 K for the (Ni 0:6 Nb 0:4 ) 70 Zr 30 amorphous alloy. It is noticed that the hydrogen permeability of the (Ni 0:6 Nb 0:4 ) 70 Zr 30 amorphous alloy is higher than that of pure Pd metal. These permeation characteristics indicate the possibility of future practical use of the melt-spun amorphous alloys as a hydrogen permeable membrane.

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The (Ni 0:6 Nb 0:4 ) 45 Zr 50 X 5 (X = Al, Co, Cu, P, Pd, Si, Sn, Ta or Ti) alloy ribbons were produced by the melt-spinning technique. All ribbon specimens were confirmed to have a single amorphous phase by XRD analysis. The crystallization temperatures of the melt-spun (Ni 0:6 Nb 0:4 ) 45 Zr 50 X 5 (X = Al, P, Pd, Si or Sn) amorphous alloys are higher than that of the (Ni 0:6 Nb 0:4 ) 50 Zr 50 amorphous alloy (727 K). Although the hydrogen permeability of the (Ni 0:6 Nb 0:4 ) 45 Zr 50 X 5 (X = Si, Sn, Ta or Ti) amorphous alloys could not be measured due to severe embrittlement during the permeation test, the (Ni 0:6 Nb 0:4 ) 45 Zr 50 X 5 (X = Al, Co, Cu, P or Pd) amorphous alloys had high ductility which was enough to measure the permeability. ] at 673 K among the alloys where the permeability was measured. The reduction of the permeability in the (Ni 0:6 Nb 0:4 ) 45 Zr 50 P 5 amorphous alloy is thought to be due to a preferential development of Zr-P atomic pairs which may suppress hydrogen solubility and hydrogen diffusivity in the alloy, because the heat of mixing for Zr-P atomic pairs is negatively larger than those of other pairs such as Ni-P and Nb-P. It is concluded that the Ni-Nb-Zr-X (X=Co or Cu) amorphous alloys have high potential to hydrogen permeable membranes.

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