Coarsening of nanoporous Au: Relationship between structure and mechanical properties

Pia, Giorgio; Delogu, Francesco

doi:10.1016/j.actamat.2015.07.074

Cited by 42 publications

(15 citation statements)

References 45 publications

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“…2d reveal that the temperature affects the coarsening rate, but not its kinetic features. Indeed, the ligament diameter, s , grows invariably according to a fourth-power law, which is the expected dependence for coarsening processes mediated by diffusion of surface atoms 26 – 29 . Accordingly, the fourth power of s , s 4 , increases linearly with time.…”

Section: Resultsmentioning

confidence: 77%

Ag surface segregation in nanoporous Au catalysts during CO oxidation

Pia

Sogne

Falqui

et al. 2018

Sci Rep

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The present study focuses on the modification of surface compositional profiles induced in nanoporous (NP) Au catalysts by the catalytic oxidation of carbon monoxide to carbon dioxide in the presence of oxygen. The phenomenon has deep implications concerning the catalytic behavior of NP Au foams in particular, and more in general for the design of more efficient catalysts. Aimed at gaining deeper insight into the mechanisms governing surface segregation, we exposed NP Au foams containing residual Ag to a mixture of gaseous carbon monoxide and oxygen at different temperature. Structural and surface composition analyses pointed out the concomitant occurrence of both NP Au coarsening and Ag surface segregation processes. Experimental findings suggest for Ag surface segregation a two-stage kinetics. During the initial, rapid coarsening of the NP Au structure, Ag surface segregation is mediated by surface rearrangements, which allow the Ag atoms to reach the surface at anomalously fast rate. As coarsening decelerates, the slower diffusion of buried Ag atoms towards the surface predominates, due to favorable chemical interactions with adsorbed oxygen. This novel mechanism’s understanding can benefit strategic areas of science and technology.

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Section: Resultsmentioning

confidence: 77%

Ag surface segregation in nanoporous Au catalysts during CO oxidation

Pia

Sogne

Falqui

et al. 2018

Sci Rep

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“…In particular, understanding the mechanical behavior of the coarsened structures is important for device applications of np-Au. Most of current investigations studying mechanical properties of np-Au involve experiments [16,17], atomistic simulations [18,19], and analytical modeling [20]. However, the role of continuum-mechanics simulation is crucial both to access regimes that are currently inaccessible experimentally and to predict the mechanical behavior of the coarsened np-Au with length scales from nano-to micrometers.…”

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confidence: 99%

Finite element analysis of mechanical stability of coarsened nanoporous gold

2016

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The mechanical stability of nanoporous gold (np-Au) at various stages of thermal coarsening is studied via finite element analysis under volumetric compression using np-Au architectures imaged via x-ray nano-tomography. As the np-Au is coarsened thermally over ligament sizes ranging from 185 to 465 nm, the pore volume fraction is determinant for the mechanical stability of the coarsened np-Au, unlike the curvature and surface orientation of the ligaments. The computed Young's modulus and yield strength of the structures are compared with the Gibson-Ashby model. The geometry of the structures determines the locations where stress concentrations occur at the onset of yielding.

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“…Thus, the phenomena discussed in this study are direct results of dislocation-driven coarsening only, which rooted from morphological-caused-instability as discussed earlier and serve as a spontaneous early-stage coarsening mechanism. Nevertheless, surface diffusion under heat-treatment could potentially result in further coarsening and drastically change the morphological properties of the NP structure on a larger timescale, including the increase of feature size and reduction of connectivity, as discussed by multiples studies [28,30,38]. Specifically, Li et al demonstrated that RD also plays a decisive role in determining how structural morphology evolves under diffusion-driven coarsening [38].…”

Section: Surface Stress-driven Dislocation Movementmentioning

confidence: 99%

“…Thus, several researchers suggest that coarsening, a common phenomenon observed in NP materials which changes the morphological properties [28], could have a substantial impact on the mechanical properties of NP materials. For example, Liu and Antoniou [29], as well as Pia and Delogu [30], have investigated mass agglomeration at nodes associated with coarsening that influence the elastic properties of NP structure and proposed a thick beam bending model to account for the presence of massive nodes. Chen-Wiegart et al [28] reported that NP structures became more anisotropic and changed their curvature distribution during coarsening.…”

Section: Introductionmentioning

confidence: 99%