Hydrogen Permeable Nb-Based Amorphous Alloys with High Thermal Stability

Abstract

In this work, the Nb-based Nb₄₂Ni₄₀Co_18−xZr_x (x = 0, 4, 12) and Nb₄₂Ni₃₂Co₆Zr₁₂M₈ (M = Ta, Ti, Zr) amorphous alloy ribbons were successfully prepared by single roller melt-spinning technique. These amorphous alloys exhibit high thermal stability with the crystallization temperature (T_x) exceeding 850 K. It has been found that T_x of the Nb₄₂Ni₄₀Co₁₈ alloy decreased with Zr addition, while hydrogen permeability increased linearly with Zr content. The hydrogen permeability of the Nb₄₂Ni₄₀Co₁₈, Nb₄₂Ni₄₀Co₁₄Zr₄, Nb₄₂Ni₄₀Co₆Zr₁₂ and Nb₄₂Ni₃₂Co₆Zr₂₀ amorphous alloys at 673 K are 0.03 × 10⁻⁸, 0.23 × 10⁻⁸, 0.69 × 10⁻⁸ and 1.40 × 10⁻⁸ mol·m⁻¹·s⁻¹·Pa^−1/2, respectively. It is noticed that hydrogen permeability of the Nb₄₂Ni₃₂Co₆Zr₂₀ alloy is comparable with that of Pd–23%Ag alloy (1.14 × 10⁻⁸). Meanwhile, permeability of the above mentioned alloy decreased to 60% of the initial value while it still maintains amorphous structure after 24 h long term durability test. Both thermal stability and hydrogen permeability are enhanced by substituting 8 at% Ni with Ta or Ti in the Nb₄₂Ni₄₀Co₆Zr₁₂ alloy. The present result indicates that the Nb-based amorphous alloys possess the potential of applying as a kind of hydrogen permeable membrane at high temperature.