Effect of surface coating element on hydrogen permeability of melt-spun Ni 40Nb 20Ta 5Zr 30Co 5 amorphous alloy

Abstract

The effect of the surface coating element on hydrogenation and hydrogen permeation of a Ni 40Nb 20Ta 5Zr 30Co 5 amorphous alloy membrane was investigated. A Pd-coated membrane absorbed hydrogen almost to saturation within the initial 20 s of measurement at 573 K. On the contrary, a Ni-coated membrane displayed a much slower hydrogen absorption rate. The Pd-coated sample exhibited hydrogen permeation one order of magnitude larger than the Ni-coated sample. Ni-coated samples showed more significant degradation of permeation flux at 673 K than the Pd-coated samples, because Ni atoms can diffuse into the membrane more easily than Pd atoms, resulting in faster degradation of catalytic activity for the Ni-coated sample than the Pd-coated sample. Furthermore, it was found that the element deposited on the lower-stream side surface of the membrane affected the promotion of hydrogen permeation more significantly than that on the upper-stream side surface. The hydrogen permeation of the sample with Ni coated on the lower-stream side surface of the membrane was much smaller than that with Pd coated on the lower-stream side surface. This observation suggests that the recombination of two H atoms and emission of H 2 molecules can be the significant barrier to hydrogen permeation. Therefore, it was concluded that the hydrogen concentration gradient in the membrane and the reaction on the lower-side surface affected the hydrogen permeability of the membrane.