Ultrasonic study of hydrogen motion in a Ti-Zr-Ni icosahedral quasicrystal and a 1/1 bcc crystal approximant

We report the first straightforward measurements of the diffusion coefficient of hydrogen migrating in icosahedral (i-) quasicrystal ribbons of Ti45Zr38Ni17 and in two-phase bulk samples containing both the i-phase and the Laves phase. It is found that at 273–353 K diffusion obeys Arrhenius’s law with activation energy 0.24 eV and that the ratio of the volumes of the phases changes at hydrogenization.

Section: Diffusion Of Hydrogencontrasting

confidence: 65%

Diffusion of hydrogen in Ti–Zr–Ni quasicrystals

Azhazha

Grib

Khadzhay

et al. 2003

“…The requirements on the local site symmetry in order for anelastic relaxation to occur are described by the selection rules for anelasticity [29]. Although mechanical spectroscopy has been used to study hydrogen trapped near defects in crystals [30,31], as well as hydrogen in amorphous metals [32,33] and quasicrystals [34], the present discussion will focus on hydrogen in solid solution in crystalline metals. For the latter situation two cases can be distinguished.…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic attenuation and dispersion due to hydrogen motion in the C15 Laves-phase compound TaV₂H_x

Foster

Hightower

Leisure

et al. 2001

Hydrogen in the C15 Laves-phase material TaV2Hx has been studied by means of resonant ultrasound spectroscopy over the temperature range of 15-345 K for a series of hydrogen concentrations (x = 0.00-0.53). Ultrasonic loss peaks and frequency shifts (dispersion) associated with the hydrogen motion were observed, yielding parameters for the hydrogen motion. Hydrogen in these materials is known to occupy the tetrahedral g sites which form a series of interlinked hexagons. The ultrasonic results were associated with H hopping between g-site hexagons. The relaxation rates for x⩽0.18 were best described as a sum of two Arrhenius processes. For x = 0.34 and 0.53 only a single Arrhenius process was needed to fit the results, although the presence of a second Arrhenius mechanism could not be over-ruled. A single relaxation rate was sufficient to fit the data; a distribution of rates was not required. The magnitudes of the attenuation and dispersion depended linearly on the hydrogen concentration implying that it is the relaxation of isolated H atoms (the Snoek effect) that is responsible for the mechanical damping. The faster local motion of H reported from nuclear magnetic resonance measurements for motion within g-site hexagons was not observed in the present study. This suggests that the H hopping rate for the local motion remains above the ultrasonic frequencies over the temperature range of study, or perhaps that too few H atoms participate in the local motion.

“…Here G(t) = e iω 0 t G(t) = e iω 0 t exp i t 0 ω(t ) dt , (5) where ω 0 is the nuclear Larmor frequency. G(t) can be expressed as…”

Section: Theoretical Dynamic Nmr Lineshape For a Distribution Of Loca...mentioning

confidence: 99%

“…It has been demonstrated [1] that Ti-and Zr-based quasicrystals (QCs) exhibit favourable hydrogen-storage properties. The best-studied examples are icosahedral (i) Ti-Zr/Hf-Ni [2][3][4][5][6] and Zr-Cu-Ni-Al [7][8][9][10][11][12][13][14]. The total loading capacity of QCs is competitive with the best known H-storage crystalline alloys (a hydrogen-to-metal ratio H/M ≈ 2.0 can be reached, whereas the maximum capacity per weight of 2.5% is less favourable), the absorption and desorption of hydrogen is quick and the alloys are made of low-cost materials.…”

Section: Introductionmentioning

confidence: 99%

Deuterium dynamics in the icosahedral and amorphous phases of the Ti₄₀Zr₄₀Ni₂₀hydrogen-absorbing alloy studied by²H NMR

Gradišek¹,

Kocjan²,

McGuiness³

et al. 2008

The Ti 40 Zr 40 Ni 20 hydrogen-absorbing alloy was prepared in the icosahedral and amorphous phases by controlling the rotation speed of the melt-spinning method of sample preparation, and the deuterium dynamics was investigated by 2 H NMR dynamic lineshape and spin-lattice relaxation. The results were analysed by the lineshape and relaxation models that assume deuterium thermally activated hopping within a manifold of different chemical environments. The observed 8% larger activation energy for the deuterium hopping over the interstitial sites and the 10% larger static spectrum width of the amorphous phase, as compared to the icosahedral phase, can be accounted for by the larger deuterium content of the investigated amorphous sample. From the deuterium dynamics point of view, the icosahedral phase is not special with respect to the amorphous modification of the same material.