HYDROGEN PERMEATION OF TERNARY Ni-Ti-Nb ALLOYS

摘要

Hydrogen permeation characteristics of Pd-coated ternary Ni-Ti-Nb alloys have been investigated using the gas permeation technique in the hydrogen pressure range of 0.20-0.97 MPa on the upstream side and in the temperature range of 523-673 K. The Ni_(30)Ti_(31)Nb_(39) alloy shows the highest hydrogen permeability of 1.93x10~(-8) [mol H_2 m~(-1) s~(-1) Pa~(-0.5)] at 673 K in the alloys investigated in the present work, which is equivalent to that of pure Pd. This alloy consists of the primary NbTi (Ni_4Ti_(13)Nb_(83)) phase and the eutectic NiTi-NbTi (Ni_(41)Ti_(38)Nb_(21)) phases, but does not contain the brittle NiTi_2 compound. The eutectic structure, which surrounds the primary phase, plays a dominant role in the prevention of the hydrogen embrittlement of the Ni_(30)Ti_(31)Nb_(39) alloy. On the other hand, the primary NbTi phase determines the hydrogen permeation of this alloy. The present work demonstrates that duplex phase alloys consisting of the hydrogen permeable phase and the one having the large resistance to the hydrogen embrittlement are promising for a new hydrogen permeation membrane.