A Calorimetric Study of the Phase Transformation in Tantalum Hydrides

Asano, Hajime; Yamada, R.; Hirabayashi, Makoto

doi:10.2320/matertrans1960.18.155

Cited by 11 publications

(2 citation statements)

References 13 publications

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“…Tantalum, a group 5 element, is of fundamental interest due to its superconducting properties, − and many aspects of tantalum and its compounds have been studied in depth. , In recent decades, several stoichiometries of tantalum hydrides have been investigated at ambient pressure. Asano et al reported that tantalum hydrides form an interstitial solid solution of hydrogen in tantalum over a wide composition range, and nine phases of Ta–H compounds were reported by Schober et al Simonović et al synthesized tantalum hydrides of various compositions by equilibrating tantalum with hydrogen in the temperature range 573–823 K under a constant hydrogen pressure of 1 bar . Near Ta 2 H, hydrogen ordering occurs.…”

Section: Introductionmentioning

confidence: 99%

Pressure-Stabilized Superconductive Ionic Tantalum Hydrides

et al. 2017

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High-pressure structures of tantalum hydrides were investigated over a wide pressure range of 0-300 GPa by utilizing evolutionary structure searches. TaH and TaH were found to be thermodynamically stable over this entire pressure range, whereas TaH, TaH, and TaH become thermodynamically stable at pressures greater than 50 GPa. The dense Pnma (TaH), R3̅m (TaH), and Fdd2 (TaH) compounds possess metallic character with a strong ionic feature. For the highly hydrogen-rich phase of Fdd2 (TaH), a calculation of electron-phonon coupling reveals the potential high-T superconductivity with an estimated value of 124.2-135.8 K.

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Section: Introductionmentioning

confidence: 99%

Pressure-Stabilized Superconductive Ionic Tantalum Hydrides

et al. 2017

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“…[6] In the Ta-H system, the ordered b-Ta 2 H phase exists around H/Ta = 0.5 at room temperature. [23,28] Thus, we can propose that when the temperature reaches the ordering temperature during cooling, multiple cracks such as concentric-and microcracks are introduced in Ta, finally giving rise to flaky debris and powders. In other words, the hydrogen-induced cracking and pulverization are due to the ordered b-Ta 2 H formation.…”

Section: Discussionmentioning

confidence: 99%

Microstructural Observation of Ordered β-Ta2H in Hydrogenated Tantalum

Semboshi

Konno

Masahashi

et al. 2007

Metall Mater Trans A

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SATOSHI SEMBOSHI, TOYOHIKO J. KONNO, NAOYA MASAHASHI, and SHUJI HANADA The microstructural changes accompanying the formation of the ordered b-Ta 2 H phase in pure tantalum (Ta) by hydrogenation have been investigated to elucidate fundamentals for hydrogeninduced cracking and pulverization. Concentric cracks as well as a number of microcracks with relieflike straight line contrasts on {001} bcc planes of a Ta grain are introduced by annealing and cooling in a hydrogen atmosphere. These contrasts correspond to boundaries between grains of the ordered b-Ta 2 H phase having a pseudo-tetragonal structure. Furthermore, the transformation of the ordered b-Ta 2 H lattice leads to an anisotropic misfit in the boundaries between the Ta matrix and the adjacent hydride grains and between hydrides with different variants. Thus, the hydride formation brings about strain large enough to trigger multiple cracks. Hence, the hydrogen-induced cracking in Ta plates occurs in the following sequence: hydrogen absorption, formation of the ordered b-Ta 2 H phases, strain accommodation, microcrack nucleation at the boundaries, and concentric crack propagation.

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