Structure and Phase State of Ti<sub>49.4</sub>Ni<sub>50.6</sub> (at%) Hydrogenated in Normal Saline
The paper analyzes the surface structure and phase state of Ti<sub>49.4</sub>Ni<sub>50.6</sub> (at%) hydrogenated at 295 K in normal saline (0.9% NaCl aqueous solution with pH = 5.7) at 20 A/m<sup>2</sup> for 0.5–6 h. The analysis shows that the average hydrogen c...
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| Autores principales: | , , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/20b1a216a0e24429be08446a7177c9f1 |
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| Sumario: | The paper analyzes the surface structure and phase state of Ti<sub>49.4</sub>Ni<sub>50.6</sub> (at%) hydrogenated at 295 K in normal saline (0.9% NaCl aqueous solution with pH = 5.7) at 20 A/m<sup>2</sup> for 0.5–6 h. The analysis shows that the average hydrogen concentration in the alloy increases with the hydrogenation time t<sub>H</sub> as follows: slowly to 50 ppm at t<sub>H</sub> = 0.5–1.5 h, steeply to 150 ppm at t<sub>H</sub> = 1.2–2 h, and linearly to 300 ppm at t<sub>H</sub> = 2–6 h. According to Bragg–Brentano X-ray diffraction data (θ–2 θ, 2 θ ≤ 50°, CoKα radiation), the alloy in its scanned surface layer of thickness ~5.6 µm reveals a TiNiH<sub>x</sub> phase with x = 0.64 and x = 0.54 after hydrogenation for 4 and 6 h, respectively. The structure of this phase is identifiable as an orthorhombic hydride similar to β<sub>1</sub>–TiFeH<sub>0.94</sub> (space group Pmcm), rather than as a tetragonal TiNiH<sub>x</sub> hydride with x = 0.30–1.0 (space group I4/mmm). Time curves are presented to trace the lattice parameters and volume change during the formation of such an orthorhombic phase from the initial cubic B2 phase in Ti<sub>49.4</sub>Ni<sub>50.6</sub> (at%). |
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