Site Change of Hydrogen Owing to Lattice Distortion in Niobium Alloys

概要

論文の詳細を見る
The site occupancy of hydrogen in Nb alloyed with oversized Ta (atomic radius; r_{\text{Nb}}=1.43 Å and r_{\text{Ta}}=1.44 Å), Nb<inf>0.50</inf>Ta<inf>0.50</inf>H<inf>0.021</inf>and Nb<inf>0.50</inf>Ta<inf>0.50</inf>H<inf>0.053</inf>, has been investigated at room temperature by the channelling method utilizing a nuclear reaction 1H(11B,\alpha)\alpha\alpha with a 11B beam of an energy of 2.02 MeV. It was observed that, in both specimens, approximately 100% of H atoms are located at tetrahedral (T) sites. The half-widths of X-ray reflection lines have been measured for the non-hydrogen-doped Nb<inf>0.50</inf>Ta<inf>0.50</inf>specimens. The half-widths for the Nb<inf>0.50</inf>Ta<inf>0.50</inf>specimens are smaller than those for Nb alloyed with approximately the same concentration of undersized Mo atoms (r_{\text{Mo}}=1.36 Å), Nb<inf>0.52</inf>Mo<inf>0.48</inf>, and close to the value for pure Nb. This result indicates that, in the Nb<inf>0.50</inf>Ta<inf>0.50</inf>specimens, the lattice is undistorted or very weakly distorted as compared with the Nb<inf>0.52</inf>Mo<inf>0.48</inf>specimens. From the present results on the half-widths and the site occupancy of hydrogen in the Nb<inf>0.50</inf>Ta<inf>0.50</inf>alloys and those hitherto obtained for the Nb<inf>0.52</inf>Mo<inf>0.48</inf>alloys, it is demonstrated that, in these two alloys, in the undistorted or very weakly distorted lattice, hydrogen occupies T sites, while, in the lattice more distorted at the intermediate level, hydrogen occupies d-T sites. The d-T sites are sites displaced from T sites by about 0.25 Å towards their nearest neighbour O sites. Thus, the solute concentration dependence of the site occupancy of hydrogen hitherto observed in the Nb--Mo and Nb--Ta alloys in the solute concentration range up to 60 at. % can be well explained on the basis of the lattice distortion induced by alloying.
2013-07-15

Site Change of Hydrogen Owing to Lattice Distortion in Niobium Alloys

スポンサーリンク

概要

著者

関連論文

スポンサーリンク