Hydrogen permeation and surface characteristics of Pd-coated Ni-Nb-Ta amorphous alloy membrane

Abstract

The hydrogen permeability of a palladium coated Ni60Nb30Ta10 amorphous alloy was examined in the temperature range of 573-673 K and pressures up to 0.6 MPa. Commercialized Pd60Cu40 alloy membranes were also evaluated in the same manner. The permeated hydrogen flux increased with increasing temperature and difference in the square-roots of hydrogen pressures on both sides of the membrane. It indicates that the diffusion of hydrogen atoms is the main factor for the hydrogen permeation in this alloy. The maximum hydrogen permeability of the Ni60Nb30Ta10 glassy alloy was 4.1 x 10(-8) [mol/m s Pa-1/2] at 673 K, which was much higher than that of Pd60Cu40 membranes measured under the same conditions, 1.9 X 10(-8) [mol/m s Pa-1/2] at 673 K. These permeation characteristics imply the possibility of future practical use of the amorphous alloys as the hydrogen permeable membrane. The thickness and compositional variations of sputtered overlayer were measured by using FE-SEM and AES, respectively, to examine the surface characteristics of Pd-coated membranes. The high-quality overlayer was achieved successfully by RF sputtering method.