Size dependent compressibility of nano-ceria: Minimum near 33 nm

Rodenbough, Philip P.; Song, Junhua; Walker, David; Clark, S. M.; Kalkan, Bora; Chan, Siu‐Wai

doi:10.1063/1.4918625

Cited by 16 publications

(13 citation statements)

References 24 publications

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“…That is, the surface ions prefer to be further aside from neighboring ions. The amount of expansion observed here exceeds the prediction partly due to bulk modulus of nanoparticles is likely crystallite size dependent, as illustrated in CeO 2 , 50 and we only use a bulk modulus reported from bulk materials. In addition, the surface adsorption of hydroxide groups gives rises to added comprehensive surface stress.…”

Section: Discussioncontrasting

confidence: 57%

Lattice Expansion in Metal Oxide Nanoparticles: MgO, Co₃O₄, & Fe₃O₄

et al. 2016

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Uniform sets of mono‐crystalline nanoparticles ranging from 6 nm to over 100 nm were prepared for the MgO, Co3O4, and Fe3O4 oxide systems. The nanoparticles were characterized by transmission electron microscopy (TEM) and x‐ray diffraction (XRD). A careful analysis shows increased lattice parameter for smaller nanoparticles of each oxide system: 0.47% expansion from bulk for 7 nm MgO crystallites, 0.15% expansion from bulk for 9 nm Co3O4 crystallites, and 0.13% expansion from bulk for 6 nm Fe3O4 crystallites. The compressive surface stresses and expansion energies against hydrostatic pressure for each oxide system were calculated, respectively, to be 4.13 N/m and 1.8 meV/formula unit for MgO, 3.09 N/m and 0.87 meV/formula unit for Co3O4, and 1.26 N/m and 0.67 meV/formula unit for Fe3O4. The fundamental understanding of oxide nanoparticle mechanics as presented here will facilitate integration of these materials into technological applications in a rationally designed manner.

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Section: Discussioncontrasting

confidence: 57%

Lattice Expansion in Metal Oxide Nanoparticles: MgO, Co₃O₄, & Fe₃O₄

et al. 2016

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“…Considering the increase in ionic radius of the cerium cation with a reduction from Ce 4+ to Ce 3+ , it is reasonable that the increased Ce 3+ concentration in CeO 2 nanocrystals caused the lattice expansion . Lattice expansion can also occur in metal oxide nanoparticles without the valence state change, but for this specific case of CeO 2 , the valence change is coupled with the size‐dependent lattice expansion …”

Section: Discussionmentioning

confidence: 99%

Atomic‐Scale Valence State Distribution inside Ultrafine CeO₂ Nanocubes and Its Size Dependence

Hao

Yoko

Chen

et al. 2018

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Atomic-scale analysis of the cation valence state distribution will help to understand intrinsic features of oxygen vacancies (V ) inside metal oxide nanocrystals, which, however, remains a great challenge. In this work, the distribution of cerium valence states across the ultrafine CeO nanocubes (NCs) perpendicular to the {100} exposed facet is investigated layer-by-layer using state-of-the-art scanning transmission electron microscopy-electron energy loss spectroscopy. The effect of size on the distribution of Ce valence states inside CeO NCs is demonstrated as the size changed from 11.8 to 5.4 nm, showing that a large number of Ce cations exist not only in the surface layers, but also in the center layers of smaller CeO NCs, which is in contrast to those in larger NCs. Combining with the atomic-scale analysis of the local structure inside the CeO NCs and theoretical calculation on the V forming energy, the mechanism of size effect on the Ce valence states distribution and lattice expansion are elaborated: nano-size effect induces the overall lattice expansion as the size decreased to ≈5 nm; the expanded lattice facilitates the formation of V due to the lower formation energy required for the smaller size, which, in principle, provides a fundamental understanding of the formation and distribution of Ce inside ultrafine CeO NCs.

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“…22 With recent experimental results on a crystal-size dependent compressibility of nano-ceria, the bulk modulus (K), the reciprocal of compressibility, of 20nm and 7nm ceria are 290 GPa and193 GPa respectively. 23 These K values of different sized ceria nanoparticles indicate that the lattice expansion caused by Madelung model is overestimated at 1.3 times of 20nm nano-ceria and underestimated at 0.9 times of 7nm nano-ceria using "bulk" modulus. By considering a possibly reduced surface adhesive ionic interaction, the overall calculation of oxygen-deficiency may be overestimated using Madelung model.…”

Section: Reduction Mechanism Of Ceo 2 Supported Cu 2 Omentioning

confidence: 95%

Reduction of Nano-Cu₂O: Crystallite Size Dependent and the Effect of Nano-Ceria Support

Song

Rodenbough

et al. 2015

J. Phys. Chem. C

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Copper (I) oxide Cu 2 O is an effective catalyst in the CO oxidation reaction. While high surface-to volume ratio in nanoparticles will increase their catalytic efficiency, it posts a stability problem. Here we study the stability of nano-cuprite against reduction as a function of its crystallite-size, and upon interaction with a nanoceria support. A systematic analysis of isothermal reduction of a series size of mono-dispersed Cu 2 O nanocrystals (±7%) with time-resolved X-ray diffraction (TR-XRD) provides the time-resolved phase fraction of Cu 2 O and the time when reduction product of Cu (f.c.c) first appears. The initial phase fraction of nano-Cu 2 O is less that one with the balance attributed to an amorphous CuO shell. Since no peaks of crystalline CuO (monoclinic) were observed, a core-shell structure with an amorphous CuO shell is proposed. From the analysis, Cu 2+ content in corresponding to shell increases from zero to 33% as Cu 2 O decreases to 8nm from the bulk. Based on the reduction profiles, a Time-Size-Reduction (TSR) diagram is constructed for the observed Cu 2 O phase behavior during reduction. The incorporation onto a nano-CeO 2 support (7nm) significantly stabilizes our nano-Cu 2 O in a reducing atmosphere. The oxygen supply propensity in terms of oxygen non-stoichiometry of CeO 2-y is shown to be lower when a larger crystallite-size CeO 2 (20nm) support is used. The larger oxygen capacity in smaller nano-CeO 2 support is analyzed and explained by the "Madelung Model" with size-dependent bulk modulus of nano-ceria.

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Size dependent compressibility of nano-ceria: Minimum near 33 nm

Cited by 16 publications

References 24 publications

Lattice Expansion in Metal Oxide Nanoparticles: MgO, Co₃O₄, & Fe₃O₄

Lattice Expansion in Metal Oxide Nanoparticles: MgO, Co₃O₄, & Fe₃O₄

Atomic‐Scale Valence State Distribution inside Ultrafine CeO₂ Nanocubes and Its Size Dependence

Reduction of Nano-Cu₂O: Crystallite Size Dependent and the Effect of Nano-Ceria Support

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Size dependent compressibility of nano-ceria: Minimum near 33 nm

Cited by 16 publications

References 24 publications

Lattice Expansion in Metal Oxide Nanoparticles: MgO, Co3O4, & Fe3O4

Lattice Expansion in Metal Oxide Nanoparticles: MgO, Co3O4, & Fe3O4

Atomic‐Scale Valence State Distribution inside Ultrafine CeO2 Nanocubes and Its Size Dependence

Reduction of Nano-Cu2O: Crystallite Size Dependent and the Effect of Nano-Ceria Support

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Lattice Expansion in Metal Oxide Nanoparticles: MgO, Co₃O₄, & Fe₃O₄

Lattice Expansion in Metal Oxide Nanoparticles: MgO, Co₃O₄, & Fe₃O₄

Atomic‐Scale Valence State Distribution inside Ultrafine CeO₂ Nanocubes and Its Size Dependence

Reduction of Nano-Cu₂O: Crystallite Size Dependent and the Effect of Nano-Ceria Support