Mechanical Properties Obtained by Indentation of Hollow Pd Nanoparticles

Abstract

Palladium nanoparticles are technologically important for catalysis, hydrogen storage, and many other applications. Here, we investigate the mechanical properties of Pd hollow nanoparticles of different sizes and thicknesses by means of classical molecular dynamics simulations. Hollow nanospheres of sizes ranging from 5 to 40 nm are compressed using planar indenters. Our results suggest that the mechanical response of hollow nanoparticles can be tailored by tuning the external radius (R) and shell thickness (ω). The largest elastic limit for a given thickness is achieved when the aspect ratio A = R/ω is 3 ≤ A ≤ 4. This delay of the onset of plastic deformation is due to the fact that, for this geometry, hollow nanoparticles can buckle, avoiding stress concentration in the contact; this in turn favors stress accumulation and dislocation emission at the inner surface, in sharp contrast to the behavior of solid nanoparticles and "bulk" surfaces.

Polycrystalline Ni nanotubes under compression: a molecular dynamics study

“…This criterion was chosen based on Cao et al 21 findings, which show a strong surface reorientation when the NT thickness is close to 1 nm. We note that this behavior has also been observed in other hollow structures [49][50][51] , for a specific combination of radius and thickness. In those cases, the surface stress is not compensated by the shell, originating a partial shrinkage, and the surface reorientation is assisted by Shockley partial dislocations as the dominant mechanism.…”

Atomistic Simulation of Nanoindentation of Ice Ih

“…The latter were carried using the large 20 × 20 × 10 nm 3 cell with double the surface area to reduce image effects due to the larger indenter size. With the exception of the faster rise of the elastic part due to the increased contact area and minor dislocation activity at 50 K, 19 the general features of the FP curves obtained for both indenter sizes are the same with similar sequences of events The Journal of Physical Chemistry C and the activity of the same main relief mechanisms of bilayerby-bilayer amorphization/melting, including its serrated character just below the melting point. The fact that the serrated nature of the FP curve close to the melting point is present for both indenter radii contrasts the findings of Gelman Constantin et al 27 in which an indenter radius of 0.55 nm was found to produce a peak-like structure whereas a value of 1.80 nm was not.…”

“…A comparison between the results obtained for both force fields provides insight into the role of water's molecular nature and the inherent asymmetry of the hydrogen bonds. 19,30 The cells used for the TIP4P/Ice model correspond to defect-free, proton-disordered ice I h structures with zero total dipole moment. 19 The cells for the mW model correspond to the same structures generated for the TIP4P/Ice model but with the protons removed.…”

“…19,30 The cells used for the TIP4P/Ice model correspond to defect-free, proton-disordered ice I h structures with zero total dipole moment. 19 The cells for the mW model correspond to the same structures generated for the TIP4P/Ice model but with the protons removed. Most of the simulations presented here were carried out using a small indenter on a cell of 10 × 10 × 10 nm 3 containing 32,032 water molecules with free surfaces on the indentation axis (z) and periodic boundary conditions in the x and y directions.…”

“…In this scenario, atomistic simulation techniques can often offer complementary insight, providing a tool for in situ computational "microscopy", 18 capable of providing details of material behavior on atomistic time and length scales. 19,20 This approach has been particularly useful in the interpretation of nanoindentation experiments for providing atomic-scale details of the processes that occur underneath an indenter tip and are inaccessible experimentally. 21−26 Nanoindentation simulations for ice, however, have been extremely scarce.…”