Hydrogen Permeation of Pure Niobium Metal in Highly Soluble Hydrogen State

Abstract

The hydrogen permeation through pure niobium metal was investigated using a gas permeation technique, focusing mainly on the measurements in a highly soluble hydrogen state. The hydrogen diffusion was found to be the rate determining step for the hydrogen permeation reaction. However, the Sieverts law that the hydrogen solubility in a metal is proportional to the square root of hydrogen pressure, was no longer satisfied in the experimental condition of the temperatures of 473 K to 673 K and the applied pressures of 260 kPa at the inlet and 60 kPa at the outlet for hydrogen. This was mainly due to the presence of a large amount of soluble hydrogen in the metal under this condition. As a result, the measured apparent hydrogen permeability decreased monotonously with decreasing temperature in pure niobium. This was completely the reverse of the temperature dependence of the hydrogen permeability in the low solubility state where the Sieverts law was satisfied. It was stressed here that the permeation measurement of hydrogen in the high solubility state was indeed necessary for getting some performance data of metal membranes in practical use.

Application of Extended Permeability to a Thick Palladium Membrane

“…The permeability, ϕ [mol H 2 /m s Pa 0.5 ], is commonly used as a measure of membrane material. However, deviation from the law has been widely reported [1][2][3][4][5].…”

Consistent description of hydrogen permeation through metal membrane based on hydrogen chemical potential and its application to alloy design

“…The detailed explanation of the hydrogen permeation test is given elsewhere. 8 It is noted that the hydrogen permeation tests for pure niobium are performed successively without sample failure even under the testing condition where the hydrogen concentration exceeds the boundary of the ductile-to-brittle transition. However, a brittle fracture takes place readily during the shutting down process due to hydrogen embrittlement.…”

“…8 The disk sample is set in a cell of hydrogen permeation test apparatus and then evacuated. Subsequently, it is heated up to 673 K and then high purity (99.99999%) hydrogen gas is introduced to both sides of the disk sample.…”

“…This is because they are less expensive and possess higher hydrogen permeability than Pd-based alloys. [7][8][9][10][11] However, a brittle fracture likely occurs during the operation under high pressure H 2 gas atmosphere which impedes the practical use of these alloy membranes. 6,12 Recently, the mechanical properties of niobium (Nb) and vanadium (V) membranes in hydrogen gas atmosphere at high temperature have been investigated by the in situ small punch (SP) test method.…”

“…5 Recently, there has been a great demand for the development of new hydrogen permeable alloys to reduce the material cost as well as to improve the hydrogen permeability. [6][7][8][9][10][11] Nb-based and V-based alloys are promising materials for hydrogen permeable membrane to be substituted for currently used Pd-based alloys. This is because they are less expensive and possess higher hydrogen permeability than Pd-based alloys.…”