Platinum nanoparticle compression: Combining in situ TEM and atomistic modeling

Abstract

Platinum Nanoparticle Compression: Combining in situ TEM and Atomistic ModelingThe mechanical behavior of nanoparticles governs their performance and stability in many applications. However, the small sizes of technologically relevant nanoparticles, with diameters in the range of 10 nm or less, significantly complicate experimental examination.These small nanoparticles are difficult to manipulate onto commercial test platforms, and deform at loads that are below the typical noise floor of the testing instruments. Here we synthesized small platinum nanoparticles directly onto a mechanical tester, and used a modified nanomanipulator to enhance load resolution to the nanonewton scale. We demonstrated the in situ compression of an 11.5-nm platinum nanoparticle with simultaneous high-resolution measurements of load and particle morphology. Molecular dynamics simulations were performed on similarly sized particles to achieve complementary measurements of load and morphology, along with atomic resolution of dislocations. The experimental and simulation results revealed comparable values for the critical resolved shear stress for failure, 1.28 GPa and 1.15 GPa, respectively. Overall, this investigation demonstrated the promise of, and some initial results from, the combination of atomistic simulations and in situ experiments with an unprecedented combination of high spatial resolution and high load resolution to understand the behavior of metal nanoparticles under compression.Platinum Nanoparticle Compression: Combining in situ TEM and Atomistic Modeling Metal face-centered-cubic (FCC) nanoparticles possess unique physical, optical, electrical, and magnetic properties with applications in fields including medicine, 1 electronics, 2 water treatment, 3 and energy technologies. 4,5 Because properties depend on nanoparticle shape and size, the performance in these applications depends on the stability of the particle, and its resistance to any mechanical loading or shearing during use. Therefore, understanding the mechanical properties of metal nanoparticles is vital for controlling their performance.Great strides have been made in the experimental measurement of the mechanical properties of metal nanoparticles, including with diamond anvil cells, 6,7 and with in situ compression inside a scanning electron microscope (SEM) 8,9 or a transmission electron microscope (TEM). [10][11][12] These techniques have been extensively applied to larger nanoparticles, with diameters in the range of tens to hundreds of nanometers, but are more challenging to apply to smaller nanoparticles with diameters in the range of 10 nm and below, so the understanding of nanoparticle deformation in this size regime remains incomplete.

Size-Dependent Role of Surfaces in the Deformation of Platinum Nanoparticles

“…In the end, this particle failed inhomogeneously and separated with part of the particle attached to the indenter. While the separation plane appears to be parallel to the indenter surface, our prior work on similar particles indicates failure along the expected Schmid-factor plane; therefore, we attribute the present shape to post-test flattening when the top portion of the particle slid off the lower portion and hit the substrate. The majority of the larger particles failed along an inclined plane, similar to those shown in Supporting Information Section S2.…”

“…This kink in the stress–strain curve and localized shearing (inhomogeneous deformation) is characteristic of displacive deformation, in which the deformation is carried primarily by dislocations. Prior investigations by others on nanowires ,− and earlier work on platinum and palladium nanoparticles have shown that defect plasticity in face-centered cubic (FCC) nanostructures proceeds via Shockley partial dislocations that leave behind stacking faults. However, the present testing was optimized for load measurement and the specific defects were not identified.…”

“…Bare platinum nanoparticles were synthesized directly on silicon wedges using either wet impregnation (WI) (see ref ( 35 ) for details) or physical vapor deposition (PVD) (see Supporting Information Section 7 for details). The nanoparticle-decorated wedges were transferred to a commercial in situ TEM nanomanipulator (biasing manipulator model 1800, Hummingbird Scientific, Lacey, WA) as shown in Figure 5 a.…”

Separating Geometric and Diffusive Contributions to the Surface Nucleation of Dislocations in Nanoparticles

“…This result is also consistent with a previous measurement of an 11.5 nm platinum nanoparticle. 63 While the yield strength measurement is loading-direction-dependent, a simple calculation of all possible loading directions ( Section S2.2 in the Supporting Information) shows that the maximum Schmid factor varies little, with an average value of 0.462 and a standard deviation of 0.033. Therefore, the orientation of the particle is expected to have only a minor effect on measured yield strength.…”

Tuning Elastic Properties of Metallic Nanoparticles by Shape Controlling: From Atomistic to Continuous Models

“…[8] However, the study of the mechanical properties of NPs is much more complex. From an experimental point of view, in situ transmission electron microscopy [9][10][11][12][13][14] or scanning electron microscopy [15,16] nanoindentations have been developed for addressing this issue as they provide real-time monitoring of the deformation. Although powerful, these experimental techniques are applied to nanoparticles, which range in diameter from a few tens to several hundred nanometers and barely suitable for smaller ones.…”