Vibrational contributions to phase stability in the Mo-Ru system

Abrecht, David G.; Clark, Richard A.F.; Schwantes, Jon M.

doi:10.1016/j.jallcom.2016.08.071

Cited by 5 publications

(3 citation statements)

References 46 publications

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“…2(a) to evaluate the phase stability and possibility for synthesis. The calculated excess energies exhibit the same tendency as seen in the phase diagram26,27 and as noted in other reports 29. It is obvious that the hcp type is the most stable phase when the Ru ratio is >60% because, in this Ru ratio range, negative excess energy is reported in this study and this has been experimentally proved 27.…”

Section: Resultssupporting

confidence: 89%

Theoretical design of a technetium-like alloy and its catalytic properties

Xie

Koyama

2019

Chem. Sci.

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Section: Resultssupporting

confidence: 89%

Theoretical design of a technetium-like alloy and its catalytic properties

Xie

Koyama

2019

Chem. Sci.

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“…The 4d group metals tend to form fcc metals rather than hcp that is observed with Ru-Mo rich phases in nuclear fuels. 32 We have previously reported on the nature of the metallic particles from these fuels and aspects of their chemistry, including the variability of compositions in the 5-metal particles and the occurrence of Ag-Pd halides. 13,[33][34][35][36] In these earlier studies, we investigated metallic particles throughout the fuel; however, in this investigation, we concentrated on the FCI region and, in particular, the oxidized Zr metal liner nearest to the fuel.…”

Section: Introductionmentioning

confidence: 99%

Distribution of metallic fission-product particles in the cladding liner of spent nuclear fuel

et al. 2020

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We have made observations of noble metal phase fission-product agglomerates and gaseous xenon within the fuel-cladding interaction (FCI) zone of a high-burnup UO 2 fuel. The FCI is the boundary between the UO 2 pellet outer surface and the inner wall of the oxidized Zr-liner/cladding of the fuel rod. These fission-product agglomerates are well known to occur within the spent fuel matrix, and although radionuclides have been reported by others, we reveal aspects of their speciation and morphology. That they occur as discrete particles in the oxidized Zr liner, suggests the occurrence of hitherto unknown processes in the FCI zone during reactor operation, and this may have implications for the long-term storage and disposal of these types of materials. As expected, the particle agglomerates, which ranged in size from the nanometer scale to the micrometer scale, contained mainly Mo, Ru, Tc, Rh, and Pd; however, we also found significant quantities of Te associated with Pd. Indeed, we found nanometer scale separation of the distinct Pd/Te phase from the other fission products within the particles. Often associated with the particles was concentrations of uranium, sometimes appearing as a "cloud" with a tail emanating from the fuel into the oxidized cladding liner. Many of the noble metal phase particles appeared as fractured clusters separated by Xe-gas-filled voids. Possible mechanisms of formation or transport in the cladding liner are presented.

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“…In the same vein, ΔS mix contributions have also been included in the calculations, albeit selectively; including ΔS mix has shown to improve the accuracy of the predicted thermodynamic quantities, such as the order-disorder phase transformation temperature and miscibility gap temperature. 3,4,[10][11][12][13][14][15] The contribution of ΔS mix has often been considered less important, largely due to its relatively smaller size compared to ΔH mix , particularly in the prediction of ordered structures. However, in the past decade, with the development of high entropy alloys (HEAs), 16,17 it is gradually becoming evident that ΔS mix might be equally important in the phase stability predictions.…”

Section: Introductionmentioning

confidence: 99%

Entropy contributions to phase stability in binary random solid solutions

et al. 2018

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High entropy alloys contain multiple elements in large proportions that make them prone to phase separation. These alloys generally have shallow enthalpy of mixing which makes the entropy contributions of similar magnitude. As a result, the phase stability of these alloys is equally dependent on enthalpy and entropy of mixing and understanding the individual contribution of thermodynamic properties is critical. In the overall vision of designing high entropy alloys, in this work, using density functional theory calculations, we elucidate the contributions of various entropies, i.e., vibrational, electronic and configurational towards the phase stability of binary alloys. We show that the contribution of electronic entropy is very small compared to the vibrational and configurational entropies, and does not play a significant role in the phase stability of alloys. The configurational and vibrational entropies can either destabilize or can collectively contribute to stabilize the solid solutions. As a result, even those systems that have negative mixing enthalpy can show phase instability, revealed as a miscibility gap; conversely, systems with positive mixing enthalpy can be phase stable due to entropic contributions. We suggest that including entropic contributions are critical in the development of theoretical framework for the computational prediction of stable, single-phase high entropy alloys that have shallow mixing enthalpies, unlike ordered intermetallics.

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Vibrational contributions to phase stability in the Mo-Ru system

Cited by 5 publications

References 46 publications

Theoretical design of a technetium-like alloy and its catalytic properties

Theoretical design of a technetium-like alloy and its catalytic properties

Distribution of metallic fission-product particles in the cladding liner of spent nuclear fuel

Entropy contributions to phase stability in binary random solid solutions

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