Reorientation relaxation of hydrogen in the C16 compounds CoZr2 and NiZr2

Sinning, H.‐R.

doi:10.1002/pssa.2211310219

Cited by 9 publications

(3 citation statements)

References 19 publications

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“…All three crystal symmetries have a large number of tetrahedral interstitial sites. Many of these compounds are known to absorb considerable amounts of hydrogen and have been studied extensively with a variety of experimental techniques [6][7][8][9][10][11][12][13][14][15][16]. The present discussion will focus on the C15 structure.…”

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

J. Phys.: Condens. Matter

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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.

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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

J. Phys.: Condens. Matter

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“…In addition, ultrasound couples to the hydrogen motion differently than the other techniques which can be a source of additional information. There have been few reports of the use of ultrasound to study hydrogen motion in intermetallic compounds, although hydrogen hopping in C-16 type materials has been studied experimentally and theoretically [15,16]. It appears that such work has not been carried out on C-15 materials.…”

Section: Introductionmentioning

confidence: 99%

An ultrasonic study of hydrogen (deuterium) motion in the C-15 Laves-phase compound

Foster

Leisure

Skripov

1999

J. Phys.: Condens. Matter

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Ultrasonic measurements have been carried out on TaV 2 H(D) x over the temperature range of 15-335 K. Temperature-dependent attenuation peaks were observed with maxima near 250 K for measurement frequencies near 1 MHz. These peaks are believed to be due to the same process as responsible for maxima in NMR spin-lattice relaxation rates observed at higher frequencies and temperatures, and associated with long-range hydrogen diffusion. The present results for activation energies and attempt frequencies are in agreement with the NMR results in the temperature range of the spin-lattice relaxation rate measurements, but the ultrasonic data suggest the presence of two Arrhenius processes for the long-range motion below about 200 K. The most significant result of the present measurements concerns a possible second peak at low temperatures associated with the local motion found in NMR and neutron measurements. For the present results, such a peak was not found in TaV 2 H x , but there was an indication of such a peak in TaV 2 D x for temperatures below 50 K. These results suggest that the H hopping rate for the local motion in TaV 2 H(D) x remains well above the ultrasonic frequencies used throughout the temperature range of the measurements, but that the D hopping rate is somewhat lower.

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“…metals for the heavier interstitials C, N, 0 [1,4] but not for hydrogen, for reasons not to be discussed here. For hydrogen we know of "Snoek-type" reorientation relaxations in amorphous alloys [5 to 71, intermetallic compounds [8,9], and in cases where H atoms are trapped by other, relatively immobile impurities like substitutional or interstitial solutes in b.c.c. metals For the reorientation relaxation of hydrogen in amorphous alloys which is the subject of this paper, it is still a matter of debate how the experimentally observed behaviourwidth, asymmetry and low-temperature shift of the relaxation peak, decrease of the average activation energy, and the variations of the relaxation strength with increasing H concentrationcan be understood by theoretical models.…”

Section: Introductionmentioning

confidence: 99%

On the concentration dependence of the hydrogen reorientation relaxation in amorphous alloys

Sinning

1993

Phys. Stat. Sol. (a)

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The anelastic reorientation relaxation of hydrogen in amorphous alloys, only partially understood as yet, is studied with respect to its concentration dependence, using recent internal friction results on Co33Zr67 with H concentrations between about 0.001 and 1 H/metal atom as an example. Three characteristic ranges are distinguished with increasing H concentration: I. an overall growth of the relaxation peak, II. a growth with suppression of high‐activation‐energy processes, and III. the range of maximum relaxation strength. This behaviour can be understood by an increasing mutual hindering of reorientation jumps between next‐nearest neighbours (NNN) due to the local HH repulsion, which counteracts the augmentation of relaxation processes by adding more H atoms. Quantitatively, the relaxation strength can be described by adding a NNN occupation probability to the respective equation from the Berry‐Pritchet model. Most of the as yet unexplained discrepancies between different amorphous alloys can be considered formally as a shift of the ranges I to III along the H concentration scale. As the physical origin of the different behaviour, different types of inhomogeneities (e.g. a chemical decomposition) as well as intrinsic alloying effects are possible.

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Reorientation relaxation of hydrogen in the C16 compounds CoZr2 and NiZr2

Cited by 9 publications

References 19 publications

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

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

An ultrasonic study of hydrogen (deuterium) motion in the C-15 Laves-phase compound

On the concentration dependence of the hydrogen reorientation relaxation in amorphous alloys

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Reorientation relaxation of hydrogen in the C16 compounds CoZr2 and NiZr2

Cited by 9 publications

References 19 publications

Ultrasonic attenuation and dispersion due to hydrogen motion in the C15 Laves-phase compound TaV2Hx

Ultrasonic attenuation and dispersion due to hydrogen motion in the C15 Laves-phase compound TaV2Hx

An ultrasonic study of hydrogen (deuterium) motion in the C-15 Laves-phase compound

On the concentration dependence of the hydrogen reorientation relaxation in amorphous alloys

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Product

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

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