Nanofaceted Metal Surfaces

Chen, Wenhua; Wang, Hao; Bartynski, Robert

doi:10.1016/b978-0-12-801217-8.00011-6

Cited by 2 publications

(1 citation statement)

References 299 publications

(348 reference statements)

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“…Indeed, an initially stable surface may facet as oxygen exposure modifies the surface energy anisotropy [70,71]. This process is known as adsorbate-induced faceting and can be used as nanotemplates, for instance, to synthesize metallic nanoparticles [72]. This makes the faceting problem of practical interest also.…”

Section: Faceting Instabilitymentioning

confidence: 99%

Regularized anisotropic motion-by-curvature in phase-field theory: Interface phase separation of crystal surfaces

2022

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The kinetic equation for anisotropic motion-by curvature is ill-posed when the surface energy is strongly anisotropic. In this case, corners or edges are present on the Wulff shape, which span a range of missing orientations. In the sharp-interface problem the surface energy is augmented with a curvature-dependent term that rounds the corners and regularizes the dynamic equations. This introduces a new length scale in the problem, the corner size. In phase-field theory, a diffuse description of the interface is adopted. In this context, an approximation of the Willmore energy can be added to the phase-field energy so as to regularize the model. In this paper, we discuss the convergence of the Allen-Cahn version of the regularized phase-field model toward the sharp-interface theory for strongly anisotropic motion-by-curvature, in three dimensions. Corners at equilibrium are also compared to theory for different corner sizes. Then, we investigate the dynamics of the faceting instability, when initially unstable surfaces decompose into stable facets. For crystal surfaces with trigonal symmetry, we find the following scaling law L ∼ t 1/3 , for the growth in time t of a characteristic morphological length scale L, and coarsening is found to proceed by either edge contraction or cube removal, as in the sharp-interface problem. Finally, we study nucleation of crystal surfaces in a two-phase system, as for a terrace-and-step surface. We find that, as compared with saddle point nucleation, ridge crossing is dynamically favoured. However, the induced nucleation mechanism, when a facet induces at its wake formation of additional facets, is not evidenced with a type-A dynamics.

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Section: Faceting Instabilitymentioning

confidence: 99%

Regularized anisotropic motion-by-curvature in phase-field theory: Interface phase separation of crystal surfaces

2022

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Ultra-fast Cu-based A³-coupling catalysts: faceted Cu₂O microcrystals as efficient catalyst-delivery systems in batch and flow conditions

Bao

Kairouz

et al. 2022

Can. J. Chem.

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Cu(I) catalysts were studied for the synthesis of a propargylamine via A3-coupling of aldehyde, amine, and alkyne, under solvent-free and low loading conditions, using batch microwave or flow thermal heating. We explore ultra-low loading conditions with Cu(I) salts as ultra fast and active catalysts featuring TOFs above 105 h-1. Well-defined octahedral and cubic Cu2O microcrystals were also successfully applied and compared to this reaction. Both types of microcrystals exhibited excellent catalytic activities within minutes, via in-situ generation of low dose of Cu(I) ions within the reaction medium, to achieve TON beyond 2000 and recycling up to 10 times in a flow reactor. The study of the catalytic system demonstrated that the activity was surface-structure dependent and allowed for the design of low Cu contamination A3-coupling systems, affording a product at the decigram scale, with Cu contamination below FDA recommendations for drug synthesis, without the need for a purification procedure.

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Nanofaceted Metal Surfaces

Cited by 2 publications

References 299 publications

Regularized anisotropic motion-by-curvature in phase-field theory: Interface phase separation of crystal surfaces

Regularized anisotropic motion-by-curvature in phase-field theory: Interface phase separation of crystal surfaces

Ultra-fast Cu-based A³-coupling catalysts: faceted Cu₂O microcrystals as efficient catalyst-delivery systems in batch and flow conditions

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Nanofaceted Metal Surfaces

Cited by 2 publications

References 299 publications

Regularized anisotropic motion-by-curvature in phase-field theory: Interface phase separation of crystal surfaces

Regularized anisotropic motion-by-curvature in phase-field theory: Interface phase separation of crystal surfaces

Ultra-fast Cu-based A3-coupling catalysts: faceted Cu2O microcrystals as efficient catalyst-delivery systems in batch and flow conditions

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Ultra-fast Cu-based A³-coupling catalysts: faceted Cu₂O microcrystals as efficient catalyst-delivery systems in batch and flow conditions