抄録
Amorphous alloys are expected as new cheep membrane materials for hydrogen separation, which is substitutable to expensive palladium alloys, maybe resulting in enlargement of application field. In this study, Zr-Ni based amorphous alloys, typical hydrogen permeable amorphous alloys, were focused on, whose diffusivity was investigated in detail especially with respect to hydrogen concentration dependency. Amorphous alloy membranes 20-40 µm thick were directly prepared from the melt by rapid quenching. All the membranes were coated with palladium using RF sputtering method to remove the difference in surface activity of each alloy. Hydrogen permeation rate was measured for pure hydrogen at elevated temperatures mainly in the range of 473-573 K. Hydrogen solubility was investigated using the Sieverts method. Hydrogen diffusivity at these temperatures was derived from the pressure dependence of permeation rate and solubility. Hydrogen permeation rate was proportional to the square root difference of hydrogen pressures on both sides as is often the case with other metal membranes. On the other hand, hydrogen solubility was found to be proportional to about the quarter power of equilibrium hydrogen pressure. This pressure dependency of hydrogen solubility could be explained using Kirchheim's theory, where potential energy distribution for hydrogen sites in amorphous alloys was taken into account. Using the theory, concentration dependence of diffusivity could be also derived, which was well consistent with experimental diffusivity determined by permeability and solubility.
