Microstructure and hydrogen transport behaviour of Nb5Ti58Fe35M2 alloy membranes

Abstract

The dual-phase alloy developed based on Group 5B metals (V, Nb, Ta) is a promising material for hydrogen purification. Especially, Nb-Ti-Fe dual-phase alloys have attracted much attention due to their dual advantages, i.e., low price and good hydrogen permeability. Nevertheless, the challenge of developing higher comprehensive performance alloys in the face of the needs of practical applications remains. To address this need, a series of alloys with the formula Nb5Ti58Fe35M2 (atom %), where M is W, Mo, Cr, Pd, Cu, Al, Co, or Ni, was devised and prepared, and their microstructure characteristics and hydrogen transport properties were investigated. The results show that alloying of different elements will lead to great changes in permeability and hydrogen embrittlement (HE), whereas the structure type is less dependent on element types. Specifically, introducing doping elements W, Mo, Cr, or Co deteriorates the performance, especially the resistance to HE. Similarly, adding Pd, Al, or Ni reduces permeability but increases HE resistance. By contrast, the alloying of Cu improves both hydrogen permeability and hydrogen brittleness. Nb5Ti58Fe35Cu2 shows a high permeability of 4.32 × 10−8 mol H2 m−1s−1Pa−0.5 at 673 K, which is better than our newly developed Nb5Ti60Fe35 alloy. In addition, this paper also demonstrated that a change of phase size and morphology arising from alloying has greater influence on permeability than a change in the orientation relationship (OR) between the phases.