The Effect of Additional Elements on Hydrogen Permeation properties of Melt-Spun Ni-Nb-Zr Amorphous Alloys

The (Ni_0.6Nb_0.4)₄₅Zr₅₀X 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_0.6Nb_0.4)₄₅Zr ₅₀X₅ (X = Al, P, Pd, Si or Sn) amorphous alloys are higher than that of the (Ni_0.6Nb_0.4)₄₅Zr₅₀ amorphous alloy (727 K). Although the hydrogen permeability of the (Ni _0.6Nb_0.4)₄₅Zr₅₀X₅ (X = Si, Sn, Ta or Ti) amorphous alloys could not be measured due to severe embrittlement during the permeation test, the (Ni_0.6Nb _0.4)₄₅Zr₅₀X₅ (X = Al, Co, Cu, P or Pd) amorphous alloys had high ductility which was enough to measure the permeability. The hydrogen permeabilities of the (Ni_0.6Nb _0.4)₄₅Zr₅₀Co₅ and the (Ni _0.6Nb_0.4)₄₅Zr₅₀Cu₅ amorphous alloys were 2.46 × 10^-8 and 2.34 × 10 ^-8 [mol·m^-1 ·s^-1 ·Pa ^-1/2] at 673 K, respectively. The (Ni_0.6Nb _0.4)₄₅Zr₅₀P₅ amorphous alloy possesses the lowest permeability of 1.36 × 10^-8 [mol·m^-1·s^-1·Pa^-1/2] at 673 K among the alloys where the permeability was measured. The reduction of the permeability in the (Ni_0.6Nb_0.4)₄₅Zr ₅₀P₅ 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.