Characteristics of niobium hydrogen solid solution

Abstract

Some characteristics of niobium hydrogen solid solution (hydrogen content, C H = 0.00-3.14 at.% H) were investigated in order to reveal the influence of hydrogen on the characteristics of niobium. The lattice parameter, the elastic moduli and the Vickers hardness of the niobium hydrogen solid solution were found to increase with increasing the hydrogen content. In addition to this experimental work, the electronic structure of the niobium hydrogen solid solution was evaluated by a first principle molecular orbital calculation. Finally, the mechanical properties of niobium hydrogen solid solution were discussed in terms of the calculation results.

Observation of a Martensitic Structural Distortion in V, Nb, and Ta

“…Our assessment is that interstitial oxygen suppresses the martensitic phase transition that is intrinsic to high-purity V, Nb, and Ta, in contradiction to these reports, and that hydrogen contamination does not play a role. Furthermore, our Vickers hardness and lattice parameter measurements are consistent with hydrogen levels of <0:05 at:% H=Nb [19].…”

“…Vicker's hardness of the Nb crystals was measured with a LECO LM100AT; the obtained value (49(2)VH0.200) is consistent with an upper limit of 0.05 at. % hydrogen [19].The linear thermal expansion ÁL=L 296 K ¼ ðLðTÞ À L 296 K Þ=L 296 K was measured along the three orthogonal h100i directions (relative to cubic structure) of the Nb single crystal. The ÁL=L 296 K data clearly show a structural distortion beginning below 296 K that results in distinct differences at 5 K for each direction, with one direction's ÁL=L 296 K larger than the other two (which are comparable).…”

“…Vicker's hardness of the Nb crystals was measured with a LECO LM100AT; the obtained value (49(2)VH0.200) is consistent with an upper limit of 0.05 at. % hydrogen [19].…”

On the proposed martensitic-like structural transformation in V, Nb, and Ta

“…5 of Ref. 26 (setting c H ≡ x in NbH x ) do not allow estimates better than ∆x ∼ 0.005. This estimate may still seem to exclude that the precipitation of H is at the origin of the anomalies with onset just below room temperature, since the solvus line x (T ) separating α and α + β phases in NbH x is close to 0.03 at room temperature.…”