Compressibility of porous materials

Balankin, S. A.; Bubnov, A S; Skorov, D. M.

doi:10.1007/bf01117275

Cited by 3 publications

(5 citation statements)

References 4 publications

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“…Similar temperature dependencies were observed earlier in acoustic investigations of the HfV 2 and ZrV 2 systems [8,9]. The found anomalies were related to the structural transformation of the cubic high-temperature phase into the orthorhombic (HfV 2 system) low-temperature phase or the rhombohedral (ZrV 2 system) low-temperature phase.…”

Section: Resultssupporting

confidence: 77%

“…It was supposed that this phase transition caused by softening of lattice modes was observed at a wide temperature range, beginning from the melting temperature [9]. As regards the nature of sound damping in the area of the transition it was supposed that it is governed by relaxation of domain boundaries arising at the transition in the phase that is less symmetric, than cubic [8].…”

Section: Discussionmentioning

confidence: 99%

“…Acoustic investigations of structural transformations in the ZrV 2 system were carried out earlier [8][9][10]. It was supposed that this phase transition caused by softening of lattice modes was observed at a wide temperature range, beginning from the melting temperature [9].…”

Section: Discussionmentioning

confidence: 99%

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Acoustic investigations of the ZrV2–H system

Arabajian

Serdobintsev

Kvirikashvili

et al. 2005

Journal of Alloys and Compounds

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Section: Resultssupporting

confidence: 77%

Section: Discussionmentioning

confidence: 99%

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Acoustic investigations of the ZrV2–H system

Arabajian

Serdobintsev

Kvirikashvili

et al. 2005

Journal of Alloys and Compounds

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“…The C15 phase has more than 1000 binary and ternary forms among the three types of Laves phases. Uniquely, only HfV 2 and UMn 2 C15 Laves phases exhibit peculiar physical and mechanical properties, including: temperature-induced structural phase transformations (Lawson & Zachariasen, 1972;Hafstrom et al, 1978;Lawson et al, 1987;Chu et al, 1996), anomalous thermal softening of elastic properties (Finlayson et al, 1978;Balankin & Skorov, 1982;Chu et al, 1994), mechanical deformation twinning in low temperatures (Livingston & Hall, 1990;Chu & Pope, 1993) and the highest superconducting temperature (T sc = 9.6 K) among intermetallics (Chu et al, 1996). For more than three decades, continuous efforts have been made to understand the observed anomalies, reveal driving mechan-isms and illustrate relationships between unusual physical properties.…”

Section: Introductionmentioning

confidence: 99%

Structural phase transitions of HfV₂ at low temperatures

Zhao

Chu

Dreele

et al. 2000

Acta Crystallogr Sect B

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We report a high-resolution synchrotron X-ray powder diffraction study on HfV(2), hafnium divanadium, at low temperatures. In this work we show, for the first time, a complete sequence of structural phase transitions of HfV(2) from cubic (Fd3m) to tetragonal (I4(1)/amd) to orthorhombic (Imma) in succession as temperature decreases. Peak splitting and extra diffraction peaks owing to lattice distortion can be clearly distinguished for the low-symmetry phases. The atomic positions and lattice parameters were obtained by Rietveld refinement. The bond lengths and angles of the HfV(2) crystal structure at the low-symmetry phases were correctly determined from the structure refinement. The face-centered cubic (Fd3m) unit cell (Z = 24) transforms to a body-centered tetragonal (I4(1)/amd) phase with a 45 degrees rotation relative to the cubic cell and with a reduced number of atoms (Z = 12) in the unit cell at a temperature of T = 112 K. The orthorhombic phase occurs at T = 102 K and it keeps the body-centered symmetry (Imma) and Z = 12 in the unit cell. The refinement results indicate that there may be a small amount of untransformed cubic phase left over in the lower symmetry phases. The abnormal thermal contraction of both tetragonal phase and orthorhombic phase marks the significance of structural change in HfV(2).

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“…There is evidence from a series of experimental studies that a structural phase transition occurs at roughly 100 K in cubic HfV 2 and ZrV 2 . 30,32,[52][53][54][55] The first-order structural phase transition appears to be preceded by an electronic transition at 125 and 160 K for HfV 2 and ZrV 2 , respectively. 30 It is within this temperature range at which unusual effects were observed for Poisson's ratio, G(T), E(T), and B(T) in these systems.…”

Section: Resultsmentioning

confidence: 99%

Strong hydrogen-related electronic effects on the shear elastic constant ofTaV2H(D)x
Foster
¹
,
Hightower
²
,
Leisure
³

et al. 2002
Phys. Rev. B
9
0
5
0
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Resonant ultrasound spectroscopy has been used to measure the shear modulus of the C15 Laves-phase compounds TaV 2 H(D) x . Polycrystalline samples with x(H)ϭ0. 00, 0.06, 0.10, 0.18, 0.34, and 0.53 and x(D)ϭ0.17 were investigated. Measurements were made over a temperature range of 3-345 K. Both the temperature dependence and the magnitude of the shear modulus ͓G(T)͔ were found to be highly dependent on the hydrogen concentration ͑x͒. At 20 K, G(T) for TaV 2 H 0.53 was 55% greater than that of TaV 2 . For H concentrations of xр0.10, G(T) of TaV 2 H x shows anomalous stiffening with increasing temperature almost across the entire temperature range of study. For H concentrations xу0.18 the temperature dependence of G(T) was reversed compared to that of the lower concentrations, exhibiting a more normal softening with increasing temperature. A minimum was found in G(T) for TaV 2 H 0.10 and TaV 2 H 0.18 at approximately 40 and 300 K, respectively. The results are in agreement with a model detailing electronic contributions to the single-crystal elastic constant c 44 . The symmetry of the C15 structure results in doubly degenerate electronic energy levels at the X point of the Brillouin zone. These levels couple to an e 4 strain with resulting effects on c 44 . The experimental results imply that the Fermi level of TaV 2 lies very close to the double-degeneracy point. The effect of hydrogen is to raise the Fermi level above the double-degeneracy point with a resulting large change in the electronic contribution to c 44 , which in turn affects the polycrystalline modulus G(T). The shift of the Fermi level with increasing hydrogen concentration determined from the elastic constant measurements is in remarkable agreement with the shift calculated from the electronic density of states available from other experiments. The results imply that each hydrogen atom contributes approximately one electron at the Fermi energy.

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Compressibility of porous materials

Cited by 3 publications

References 4 publications

Acoustic investigations of the ZrV2–H system

Acoustic investigations of the ZrV2–H system

Structural phase transitions of HfV₂ at low temperatures

Strong hydrogen-related electronic effects on the shear elastic constant ofTaV2H(D)x
Foster
¹
,
Hightower
²
,
Leisure
³

et al. 2002
Phys. Rev. B
9
0
5
0
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Compressibility of porous materials

Cited by 3 publications

References 4 publications

Acoustic investigations of the ZrV2–H system

Acoustic investigations of the ZrV2–H system

Structural phase transitions of HfV2 at low temperatures

Strong hydrogen-related electronic effects on the shear elastic constant ofTaV2H(D)xFoster1, Hightower2, Leisure3 et al. 2002Phys. Rev. B9050View full textAdd to dashboardCite

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Structural phase transitions of HfV₂ at low temperatures

Strong hydrogen-related electronic effects on the shear elastic constant ofTaV2H(D)x
Foster
¹
,
Hightower
²
,
Leisure
³

et al. 2002
Phys. Rev. B
9
0
5
0
View full text Add to dashboard Cite