Thermal Stability and Hydrogen Permeation of Ni₄₂Zr₃₀Nb_28−xTa_x Amorphous Alloys

Abstract

The thermal stability and hydrogen permeability of Ni₄₂Zr₃₀Nb_28−xTa_x (x=0,7,14,21,28) amorphous alloys have been studied in the present work. The substitution of Nb by Ta was found to be effective in improving the thermal stability of the Ni₄₂Zr₃₀Nb₂₈ amorphous alloy. The onset crystallization temperature of the Ni₄₂Zr₃₀Nb_28−xTa_x amorphous alloys was increased by 58 K from 807 K for Ta-free composition to 865 K for Ni₄₂Zr₃₀Ta₂₈ due to the Ta addition. The hydrogen permeability of the Pd-coated Ni₄₂Zr₃₀Ta₂₈ amorphous membrane was measured to be about 0.86×10⁻⁸ mol·m⁻¹·s⁻¹·Pa^−1⁄2 at 673 K, which is slightly lower than that of the Pd-coated Ni₄₂Zr₃₀Nb₂₈ amorphous membrane. The hydrogen permeability of the Ni₄₂Zr₃₀Ta₂₈ amorphous membrane was revealed to be more temperature dependent in comparison to that of the reference membrane. The higher thermal stability combined with good hydrogen permeability give rise to the possibility of the practical use for Ni₄₂Zr₃₀Ta₂₈ amorphous alloy as a dense metal membrane operating at higher temperatures.