Investigation of the Thermal Stability of NdxScyZr1–x–yO2−δ Materials Proposed for Inert Matrix Fuel Applications

Hayes, John R.; Grosvenor, Andrew P.; Saoudi, Mouna

doi:10.1021/acs.inorgchem.5b01886

Cited by 7 publications

(6 citation statements)

References 74 publications

(196 reference statements)

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“…As shown in the normalized X-ray absorption near-edge structure (XANES) spectra (Figure b), the absorption edge position of Y 1 /NC is quite different from that of Y foil and is similar to that of Y 2 O 3 , which indicates the average valence state of Y 1 is approximately +3 . The Fourier-transformed extended X-ray absorption fine structure (FT-EXAFS) spectrum of Y 1 /NC shows a main peak at 1.8 Å, close to the Y–O bond (1.7 Å) of Y 2 O 3 (Figure c). , The wavelet-transform (WT) EXAFS images in Figure d demonstrate that Y 1 /NC has a WT maximum with a k value of 3.6 Å –1 , which can be distinguished from the Y–O ( k = 4.2 Å –1 ) and Y–Y ( k = 7.0 Å –1 ) paths. It is thus deduced that the Y 1 atom is coordinated with N and/or C atoms in Y 1 /NC.…”

Section: Results and Discussionmentioning

confidence: 91%

“…32 The Fourier-transformed extended X-ray absorption fine structure (FT-EXAFS) spectrum of Y 1 /NC shows a main peak at 1.8 Å, close to the Y−O bond (1.7 Å) of Y 2 O 3 (Figure 1c). 33,34 The wavelet-transform (WT) EXAFS images in Figure 1d demonstrate that Y 1 /NC has a WT maximum with a k value of 3.6 Å −1 , which can be distinguished from the Y−O (k = 4.2 Å −1 ) and Y−Y (k = 7.0 Å −1 ) paths. It is thus deduced that the Y 1 atom is coordinated with N and/or C atoms in Y 1 /NC.…”

Section: Resultsmentioning

confidence: 99%

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Rare Earth Single-Atom Catalysts for Nitrogen and Carbon Dioxide Reduction

et al. 2020

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Single-atom catalysts (SACs) have attracted much attention owning to their high catalytic properties. Herein, yttrium and scandium rare earth SACs are successfully synthesized on a carbon support (Y1/NC and Sc1/NC). Different from the well-known M–N4 structure of M–N–C (M = Fe, Co) catalysts, Sc and Y atoms with a large atomic radius tend to be anchored to the large-sized carbon defects through six coordination bonds of nitrogen and carbon. Although Y- and Sc-based nanomaterials are generally inactive to room-temperature electrochemical reactions, Y1/NC and Sc1/NC SACs exhibit catalytic activities to nitrogen reduction reaction and carbon dioxide reduction reaction due to the modulation of the local electronic structure of Y/Sc single atoms by N and C coordination. The catalytic functions of rare earth single atoms not only demonstrate the magical effect of SACs but also promote the application of rare earth catalysts in room-temperature electrochemical reactions.

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Section: Results and Discussionmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Rare Earth Single-Atom Catalysts for Nitrogen and Carbon Dioxide Reduction

et al. 2020

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“…[ 130 ] Figure 16n resolves Y 1 /NC FT‐EXAFS spectra with a primary peak mirroring that of the Y 2 O 3 Y‐O bond (1.8 vs 1.7 Å, respectively). [ 131 ] First‐principles DFT simulations supplement these EXAFS results by resolving the most favorable coordination of Y active sites in Y 1 /NC, [ 132 ] reviewing two carbon defect types (A and B, Figure 16o) within which single Y SACs were inserted. Type A defects consist of graphite carbon planes with two nearest neighbor C site vacancies, as observed in most M−N−C (M = transition metal) SACs in past literature.…”

Section: The Impact Of Composition On Experimental Characterizationmentioning

confidence: 99%

Engineering Single Atom Catalysts to Tune Properties for Electrochemical Reduction and Evolution Reactions

Maiti

Curnan

et al. 2021

Advanced Energy Materials

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Electrocatalysis is important to the conversion and storage of renewable energy resources, including fuel cells, water electrolysers, and batteries. Engineering metal‐based nano‐architectures and their atomic‐scale surfaces is a promising approach for designing electrocatalysts. Single metal atom interactions with substrates and reaction environments crucially modulate the surface electronic properties of active metal centers, yielding controllable scaling relationships and transitions between different reaction mechanisms that improve catalytic activity. Single‐atom catalysts (SACs) allow activity and selectivity tuning while maintaining relatively consistent morphologies. SACs have well‐defined configurations and active centers within homogeneous single‐atom dispersions, producing exceptional selectivities, activities, and stabilities. Furthermore, SACs with high per‐atom utilization efficiencies, well‐controlled substrate compositions, and engineered surface structures develop single atom active sites for molecular reactions, enhancing mass activities. Recent developments in different metal‐based SAC nanostructures are discussed to explain their remarkable bi‐functional electrocatalytic activities and high mechanical flexibility, especially in the oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, hydrogen evolution reaction, and in battery applications. Existing barriers to and future insights into improving SAC performance are addressed. This study develops practical and fundamental insights on single atom electrocatalysts directed towards tuning their electrocatalytic activities and enhancing their stabilities.

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“…4a and 5a) show that the surfaces of the pellets contained large, faceted grains and that the surfaces were similar to the previously reported surfaces of Nd x Sc y Zr 1-x-y O 2-␦ pellets that were also synthesized using a co-precipitation method and annealed at 800°C. 57 The surfaces became less faceted and more porous upon annealing at 1400°C (Figs. 4b and 4c).…”

Section: Sem and Wdsmentioning

confidence: 99%

“…39 An identical change in topography was also observed by SEM when Nd x Sc y Zr 1-x-y O 2-␦ materials made via co-precipitation were annealed at 1400°C. 57 This indicates that the surface topography depends significantly on annealing temperature, with material composition and synthetic method playing little to no role.…”

Section: Sem and Wdsmentioning

confidence: 99%

Investigation of Nd_xY_0.25–_xZr_0.75O_1.88 inert matrix fuel materials made by a co-precipitation synthetic route

Hayes

Grosvenor

2016

Can. J. Chem.

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Yttria-stabilized zirconia (YSZ) is a material that is being considered for use as an inert matrix fuel in nuclear reactors, but a complete characterization of these materials is required for them to be licensed for use. A series of Nd x Y 0.25-x Zr 0.75 O 1.88 materials have been synthesized using a co-precipitation method, and the thermal stability of these materials has been studied by annealing them at 1400 and 1500°C. (Nd was used as surrogate for Am.) The long-range and local structures of the materials were characterized via powder X-ray diffraction, scanning electron microscopy, wavelength dispersive spectroscopy, and X-ray absorption spectroscopy at the Zr K-and Y K-edges. These results were compared with the previous characterization of Nd-YSZ materials synthesized using a ceramic method. The results indicated that the ordering in the local metal-oxygen polyhedral remains relatively unaffected by the synthetic method, but there was increased long-range disorder in the materials prepared by the co-precipitation method. Further, it was found that the materials produced by the co-precipitation method were unexpectedly unstable when annealed at high temperature. This study highlights the importance of determining the effect of synthetic method on material properties and demonstrates how the co-precipitation route could be used to produce inert matrix fuels.Key words: XAS, ceramics, stabilized zirconia, nuclear energy, XRD.Résumé : La zircone stabilisée par oxyde d'yttrium (YSZ) constitue un matériau dont l'utilisation est envisagée comme combustible à matrice inerte dans les réacteurs nucléaires, mais une caractérisation complète de tels matériaux est nécessaire pour que leur utilisation puisse être autorisée. Nous avons synthétisé une série de matériaux de formule Nd x Y 0,25-x Zr 0,75 O 1,88 par une méthode de coprécipitation et étudié la stabilité thermique de ces matériaux en les soumettant à un recuit à 1 400 et 1 500°C. (Le Nd a été employé comme substitut de l'Am.) Par la suite, nous avons caractérisé les matériaux en effectuant des analyses structurales d'ordre à longue et à courte distance au moyen de techniques de diffraction des rayons X sur poudre, de microscopie électronique à balayage, de spectroscopie de dispersion des longueurs d'onde et de spectroscopie d'absorption des rayons X au seuil K du Zr et de l'Y. Nous avons comparé ces résultats avec les analyses antérieures de caractérisation de matériaux de Nd-YSZ préparés à l'aide d'une méthode de synthèse de céramiques. Les résultats ont montré que la méthode de synthèse a relativement peu d'influence sur l'ordre à courte distance dans le polyèdre métal-oxygène, tandis qu'une augmentation du désordre à longue distance a été observée dans les matériaux synthétisés par la méthode de coprécipitation. De plus, nous avons observé que les matériaux produits par la méthode de coprécipitation présentaient une instabilité imprévue lorsqu'ils étaient soumis au recuit à haute température. La présente étude souligne l'importance de déterminer l...

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Investigation of the Thermal Stability of Nd_xSc_yZr_1–x–yO_2−δ Materials Proposed for Inert Matrix Fuel Applications

Cited by 7 publications

References 74 publications

Rare Earth Single-Atom Catalysts for Nitrogen and Carbon Dioxide Reduction

Rare Earth Single-Atom Catalysts for Nitrogen and Carbon Dioxide Reduction

Engineering Single Atom Catalysts to Tune Properties for Electrochemical Reduction and Evolution Reactions

Investigation of Nd_xY_0.25–_xZr_0.75O_1.88 inert matrix fuel materials made by a co-precipitation synthetic route

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Investigation of the Thermal Stability of NdxScyZr1–x–yO2−δ Materials Proposed for Inert Matrix Fuel Applications

Cited by 7 publications

References 74 publications

Rare Earth Single-Atom Catalysts for Nitrogen and Carbon Dioxide Reduction

Rare Earth Single-Atom Catalysts for Nitrogen and Carbon Dioxide Reduction

Engineering Single Atom Catalysts to Tune Properties for Electrochemical Reduction and Evolution Reactions

Investigation of NdxY0.25–xZr0.75O1.88 inert matrix fuel materials made by a co-precipitation synthetic route

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Investigation of the Thermal Stability of Nd_xSc_yZr_1–x–yO_2−δ Materials Proposed for Inert Matrix Fuel Applications

Investigation of Nd_xY_0.25–_xZr_0.75O_1.88 inert matrix fuel materials made by a co-precipitation synthetic route