Observation of the δ to ε Zr‐hydride transition by in‐situ synchrotron X‐ray diffraction

Maimaitiyili, Tuerdi; Steuwer, A.; Blomqvist, Jakob; Bjerkén, Christina; Blackmur, Matthew S.; Zanellato, Olivier; Andrieux, J.; Ribeiro, Fabienne

doi:10.1002/crat.201600234

Cited by 21 publications

(12 citation statements)

References 28 publications

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“…The transition of ZrH 1.5 to ZrH 2 and Zr (reverse reaction of R1) is also exothermic. This reaction is also observed by recent experiment by Maimaitiyili et al [51]. As suggested by Wang et al, the transition from δ to γ or ε is diffusion controlled.…”

Section: Stability Of Zr Hydrides At Different Temperaturesupporting

confidence: 85%

Structure and thermodynamic properties of zirconium hydrides by structure search method and first principles calculations

Zhu

Lin

Fang

et al. 2018

Computational Materials Science

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Section: Stability Of Zr Hydrides At Different Temperaturesupporting

confidence: 85%

Structure and thermodynamic properties of zirconium hydrides by structure search method and first principles calculations

Zhu

Lin

Fang

et al. 2018

Computational Materials Science

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“…Nevertheless, ab-initio calculations such as reported in Olsson et al (2014Olsson et al ( , 2015 may contribute to fill in the gaps, as well as recently performed experiments, cf. Maimaitiyili et al (2015), Maimaitiyili et al (2016). Further experiments that are especially designed for capturing phase transformation induced by a crack, are recommended.…”

Section: Further Remarksmentioning

confidence: 99%

Phase structural ordering kinetics of second-phase formation in the vicinity of a crack

2017

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The formation of a second phase in presence of a crack in a crystalline material is modelled and studied for different prevailing conditions in order to predict and a posteriori prevent failure, e.g. by delayed hydride cracking. To this end, the phase field formulation of Ginzburg-Landau is selected to describe the phase transformation, and simulations using the finite volume method are performed for a wide range of material properties. A sixth order Landau potential for a single structural order parameter is adopted because it allows the modeling of both first and second order transitions and its corresponding phase diagram can be outlined analytically. The elastic stress field induced by the crack is found to cause a space-dependent shift in the transition temperature, which promotes a second-phase precipitation in vicinity of the crack tip. The spatiotemporal evolution during nucleation and growth is successfully monitored for different combinations of material properties and applied loads. Results for the second-phase shape and size evolution are presented and discussed for a number of selected characteristic cases. The numerical results at steady state are compared to mean-field equilibrium solutions and a good agreement is achieved. For materials applicable to the model, the results can be used to predict the evolution of an eventual second-phase formation through a dimen-

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“…ZrH 2 is more subtle, as depending on small stoichiometry differences and temperature, [26] a fluorite structure (δ phase) with close-packed Zr, or more open body-centered tetragonal (bct) type ɛ phase (I4/mmm) with hydride can be obtained. [27] Our room temperature XRD measurements show a bct-type ɛ phase; we have not yet confirmed the structure at 400°C during ammonia synthesis.…”

mentioning

confidence: 56%

Vanadium Hydride as an Ammonia Synthesis Catalyst

et al. 2020

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Early 3d transition metals, such as Ti, V, or Nb are known to be inactive for the Haber‐Bosch process, due to their strong M−N bonds. However, recently some hydride compounds have been found to effectively counteract this effect, imparting catalytic activity on a wide range of elements. With these hydride catalysts, hydride (and nitride) bulk diffusion mechanisms have been proposed; if so, more open structures should enhance their activity. Here, we expand the study to hydrides of other early transition metals, V and Nb. These metals benefit from body‐centered cubic (bcc) related structures which enhance hydride diffusion, in addition to having relatively lower M−N bond strengths. The activity of vanadium hydride, most likely with an active composition of VH0.44N0.16, is superior to the previously reported BaTiO2.5H0.5, and comparable to TiH2 and Cs−Ru/MgO at 400 °C under 5 MPa. These results show that there is more potential for developing new single‐phase hydride catalysts of previously overlooked elements without sacrificing activity.

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Observation of the δ to ε Zr‐hydride transition by in‐situ synchrotron X‐ray diffraction

Cited by 21 publications

References 28 publications

Structure and thermodynamic properties of zirconium hydrides by structure search method and first principles calculations

Structure and thermodynamic properties of zirconium hydrides by structure search method and first principles calculations

Phase structural ordering kinetics of second-phase formation in the vicinity of a crack

Vanadium Hydride as an Ammonia Synthesis Catalyst

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