Alloying Effects on the Hydriding Properties of Niobium Metal

Abstract

Niobium metal forms two kind of hydrides, NbH and NbH₂, by hydrogenation, and the corresponding plateau region appears at low and high hydrogen permeable regions in the PCT curve of the Nb–H system. However, alloying effects have never been investigated in this system. In the present study, alloying effects were firstly investigated with various binary Nb–3 mol%M and Nb–5 mol%M alloys. Here M’s were 4d transition metals, Zr, Mo, Ru, Rh and Pd, all of which were soluble in bcc Nb. The stability of each hydride was found to be varied with the addition of a small amount of alloying elements into niobium metal. For example, the β (NbH) phase became most unstable by the addition of Ru, whereas δ (NbH₂) phase became most unstable by the addition of Mo. These data will be useful for the design of hydrogen permeable niobium-based membranes.