Alloying Effects on Hydrogen Solubility and Hydrogen Permeability for V-Based Alloy Membranes

Abstract

The alloying effects of chromium, molybdenum, tungsten, iron and cobalt on the hydrogen solubility of vanadium have been investigated systematically. The addition of iron or cobalt into vanadium decreases the hydrogen solubility more significantly than chromium, molybdenum and tungsten. Thus, the addition of iron or cobalt into vanadium improves the resistance to hydrogen embrittlement of the vanadium alloy itself effectively. It is also found that, in view of the new description of hydrogen permeation based on hydrogen chemical potential, these alloying elements enhance the hydrogen flux through the vanadium alloy. This is because the PCT factor, f PCT , increases by the addition of iron or cobalt. Thus, alloying these elements into vanadium improves not only the resistance to hydrogen embrittlement, but also the hydrogen permeation ability.

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

“…From these two points of f PCT and DBTC, Suzuki et al have proposed the most practical way to design alloy composition with high hydrogen flux while preventing brittle fracture during the operation. 20,27,28 A schematic illustration showing the concept for alloy design is shown in Fig. 11.…”

Suppressed Hydrogen (H) Solubility in Body Centered Cubic Vanadium (V) by Alloying with Molybdenum (Mo), Chromium (Cr), Iron (Fe) or Cobalt (Co) Appreciated in Terms of Statistical Thermodynamics

“…24 in Ref. 1)). However, as demonstrated by series of statistical thermodynamics analyses for extensive range of ternary non-stoichiometric interstitial compounds consisting of two metallic constituents, M I and M II and single interstitial component X, (M I ) 1¹y (M II ) y X x (X = H, C, N, P or S), and those consisting of single metal component and two interstitial constituents, Z and X, MZ z X x , 430) suppressed or enhanced X solubility in M I by alloying with M II or by presence of another interstitial constituent Z besides X might be appreciated in terms of modified number ª of available interstitial sites for occupation by the interstitial atom X per metal atom from that in M I by substitutional alloying with M II or by additional presence of another interstitial constituent Z besides X in M and, using the sub-lattice model with the designated value of the ª parameter, nearest neighbour interaction energy terms E(i-j) were evaluated (i, j = M, X).…”

“…Equilibrium isothermal pressure-composition (PC) relationships were recently reported for hydrogen (H) solubility in membranes of body centered cubic (bcc) vanadium (V) alloyed with Mo, Cr, Fe or Co (in the following, simply referred to as V 1¹y M y H x ) over a range of temperature T between 773 K and 673 K by Suzuki et al 1) on a recent issue of this journal. The reported isothermal PC relationships for poly-crystalline bcc V 1¹y M y H x membranes appear to be interpreted straightforwardly in terms of H solubility suppression due to alloying with M to bulk V for which isothermal PC relationships were reported by Veleckis and Edwards.…”

“…2) There appears to be no necessity for interpreting reported isothermal PC relations for V 1¹y M y H x by Suzuki et al 1) to take into account contributions of other factors (such as extremely small thickness of the V film or preferential crystal orientation of the thin film) as was done on statistical thermodynamic analysis for significant modulation of H absorption behavior reported by Andersson et al 3) for epitaxial V (001) thin films with thickness 50 and 100 nm from that for the bulk bcc V.…”

“…Suzuki et al 1) evaluated semi-quantitatively the alloying effect of M towards suppression of H solubility to V 1¹y M y lattice using an arbitrary chosen index referring to equilibrium H 2 partial pressure p(H 2 ) to yield ratio x of H atoms against total metal atoms (V + M) in V 1¹y M y H x to be equal to 0.2 (cf. Figs.…”