three-dimensional observation of plasticity onset in a Pt nanoparticle.

Defects in nanocrystals can dramatically alter their physical and chemical behavior. It is thus crucial to understand the defect behavior at the nanoscale to enhance material properties. Here, we report three-dimensional defect characterization at the onset of plasticity in a 550 nm Pt nanoparticle.

Capturing Catalyst Strain Dynamics during CO Oxidation.

Understanding the strain dynamic behavior of catalysts is crucial for the development of cost-effective, efficient, stable, and long-lasting catalysts. Using time-resolved Bragg coherent diffraction imaging at the fourth generation Extremely Brilliant Source of the European Synchrotron (ESRF-EBS), we achieved subsecond time resolution during chemical reactions. Upon investigation of Pt nanoparticles during CO oxidation, the three-dimensional strain profile highlights significant changes in the surface and subsurface regions, where localized strain is probed along the [111] direction.

Unveiling Core-Shell Structure Formation in a NiFe Nanoparticle with In Situ Multi-Bragg Coherent Diffraction Imaging.

Solid-state reactions play a key role in materials science. The evolution of the structure of a single 350 nm NiFe nanoparticle, , its morphology (facets) as well as its deformation field, has been followed by applying multireflection Bragg coherent diffraction imaging. Through this approach, we unveiled a demixing process that occurs at high temperatures (600 °C) under an Ar atmosphere.

Solid-State Dewetting of Thin Au Films for Surface Functionalization of Biomedical Implants.

Biomaterial-centered infections of orthopedic implants remain a significant burden in the healthcare system due to sedentary lifestyles and an aging population. One approach to combat infections and improve implant osteointegration is functionalizing the implant surface with anti-infective and osteoinductive agents. In this framework, Au nanoparticles are produced on the surface of Ti-6Al-4V medical alloy by solid-state dewetting of 5 nm Au film and used as the substrate for the conjugation of a model antibiotic vancomycin via a mono-thiolated poly(ethylene glycol) linker.

Enhancing the detection capabilities of nano-avalanches via data-driven classification of acoustic emission signals.

Acoustic emission (AE) is a powerful experimental method for studying discrete and impulsive events termed avalanches that occur in a wide variety of materials and physical phenomena. A particular challenge is the detection of small-scale avalanches, whose associated acoustic signals are at the noise level of the experimental setup. The conventional detection approach is based on setting a threshold significantly larger than this level, ignoring "false" events with low AE amplitudes that originate from noise.

Bragg coherent diffraction imaging with the CITIUS charge-integrating detector.

The CITIUS detector is a next-generation high-speed X-ray imaging detector. It has integrating-type pixels and is designed to show a consistent linear response at a frame rate of 17.4 kHz, which results in a saturation count rate of over 30 Mcps pixel when operating at an acquisition duty cycle close to 100%, and up to 20 times higher with special extended acquisition modes.

Anomalous Glide Plane in Platinum Nano- and Microcrystals.

At the nanoscale, the properties of materials depend critically on the presence of crystal defects. However, imaging and characterizing the structure of defects in three dimensions inside a crystal remain a challenge. Here, by using Bragg coherent diffraction imaging, we observe an unexpected anomalous {110} glide plane in two Pt submicrometer crystals grown by very different processes and having very different morphologies.

In Situ Nano-Indentation of a Gold Sub-Micrometric Particle Imaged by Multi-Wavelength Bragg Coherent X-ray Diffraction.

The microstructure of a sub-micrometric gold crystal during nanoindentation is visualized by in situ multi-wavelength Bragg coherent X-ray diffraction imaging. The gold crystal is indented using a custom-built atomic force microscope. A band of deformation attributed to a shear band oriented along the (221) lattice plane is nucleated at the lower left corner of the crystal and propagates towards the crystal center with increasing applied mechanical load.

Imaging the facet surface strain state of supported multi-faceted Pt nanoparticles during reaction.

Nanostructures with specific crystallographic planes display distinctive physico-chemical properties because of their unique atomic arrangements, resulting in widespread applications in catalysis, energy conversion or sensing. Understanding strain dynamics and their relationship with crystallographic facets have been largely unexplored. Here, we reveal in situ, in three-dimensions and at the nanoscale, the volume, surface and interface strain evolution of single supported platinum nanocrystals during reaction using coherent x-ray diffractive imaging.

Structure Refinement and Fragmentation of Precipitates under Severe Plastic Deformation: A Review.

During severe plastic deformation (SPD), the processes of lattice defect formation as well as their relaxation (annihilation) compete with each other. As a result, a dynamic equilibrium is established, and a steady state is reached after a certain strain value. Simultaneously, other kinetic processes act in opposite directions and also compete with each other during SPD, such as grain refinement/growth, mechanical strengthening/softening, formation/decomposition of solid solution, etc.

Grain Boundary Wetting by a Second Solid Phase in the High Entropy Alloys: A Review.

In this review, the phenomenon of grain boundary (GB) wetting by the second solid phase is analyzed for the high entropy alloys (HEAs). Similar to the GB wetting by the liquid phase, the GB wetting by the second solid phase can be incomplete (partial) or complete. In the former case, the second solid phase forms in the GB of a matrix, the chain of (usually lenticular) precipitates with a certain non-zero contact angle.

Bridging the thermodynamics and kinetics of temperature-induced morphology evolution in polymer/fullerene organic solar cell bulk heterojunction.

The performance of organic solar cells (OSC) critically depends on the morphology of the active layer. After deposition, the active layer is in a metastable state and prone to changes that lead to cell degradation. Here, a high efficiency fullerene:polymer blend is used as a model system to follow the temperature-induced morphology evolution through a series of thermal annealing treatments.

Twin boundary migration in an individual platinum nanocrystal during catalytic CO oxidation.

At the nanoscale, elastic strain and crystal defects largely influence the properties and functionalities of materials. The ability to predict the structural evolution of catalytic nanocrystals during the reaction is of primary importance for catalyst design. However, to date, imaging and characterising the structure of defects inside a nanocrystal in three-dimensions and in situ during reaction has remained a challenge.

When More Is Less: Plastic Weakening of Single Crystalline Ag Nanoparticles by the Polycrystalline Au Shell.

It is well-known that in the case of bulk polycrystalline metals, a reduction in the grain size leads to material hardening, since the grain boundaries represent efficient barriers for slip transfer between the adjacent crystalline grains. Here, we show that coating single crystalline Ag nanoparticles with a thin polycrystalline Au layer leads to a weakening of the particles. Moreover, while the single crystalline Ag nanoparticles yield in a single large displacement burst when loaded in compression, their Ag-Au core-shell counterparts demonstrate a more homogeneous deformation with signs of strain hardening.

The impact of alloying on defect-free nanoparticles exhibiting softer but tougher behavior.

The classic paradigm of physical metallurgy is that the addition of alloying elements to metals increases their strength. It is less known if the solution-hardening can occur in nano-scale objects, and it is totally unknown how alloying can impact the strength of defect-free faceted nanoparticles. Purely metallic defect-free nanoparticles exhibit an ultra-high strength approaching the theoretical limit.

Author Correction: Continuous scanning for Bragg coherent X-ray imaging.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Plastic Forming of Metals at the Nanoscale: Interdiffusion-Induced Bending of Bimetallic Nanowhiskers.

Controlled plastic forming of nanoscale metallic objects by applying mechanical load is a challenge, since defect-free nanocrystals usually yield at near theoretical shear strength, followed by stochastic dislocation avalanches that lead to catastrophic failure or irregular, uncontrolled shapes. Herein, instead of mechanical load, we utilize chemical stress from imbalanced interdiffusion to manipulate the shape of nanowhiskers. Bimetallic Au-Fe nanowhiskers with an ultrahigh bending strength were synthesized employing the molecular beam epitaxy technique.

Continuous scanning for Bragg coherent X-ray imaging.

We explore the use of continuous scanning during data acquisition for Bragg coherent diffraction imaging, i.e., where the sample is in continuous motion.

Anomalous diffusion along metal/ceramic interfaces.

Interface diffusion along a metal/ceramic interface present in numerous energy and electronic devices can critically affect their performance and stability. Hole formation in a polycrystalline Ni film on an α-AlO substrate coupled with a continuum diffusion analysis demonstrates that Ni diffusion along the Ni/α-AlO interface is surprisingly fast. Ab initio calculations demonstrate that both Ni vacancy formation and migration energies at the coherent Ni/α-AlO interface are much smaller than in bulk Ni, suggesting that the activation energy for diffusion along coherent Ni/α-AlO interfaces is comparable to that along (incoherent/high angle) grain boundaries.

Nickel nanoparticles set a new record of strength.

Material objects with micrometer or nanometer dimensions can exhibit much higher strength than macroscopic objects, but this strength rarely approaches the maximum theoretical strength of the material. Here, we demonstrate that faceted single-crystalline nickel (Ni) nanoparticles exhibit an ultrahigh compressive strength (up to 34 GPa) unprecedented for metallic materials. This strength matches the available estimates of Ni theoretical strength.

3D Imaging of a Dislocation Loop at the Onset of Plasticity in an Indented Nanocrystal.

Structural quality and stability of nanocrystals are fundamental problems that bear important consequences for the performances of small-scale devices. Indeed, at the nanoscale, their functional properties are largely influenced by elastic strain and depend critically on the presence of crystal defects. It is thus of prime importance to be able to monitor, by noninvasive means, the stability of the microstructure of nano-objects against external stimuli such as mechanical load.

Self-Healing and Shape Memory Effects in Gold Microparticles through the Defects-Mediated Diffusion.

Some metal alloys subjected to irreversible plastic deformation can repair the inflicted damage and/or recover their original shape upon heating. The conventional shape memory effect in metallic alloys relies on collective, or "military" phase transformations. This work demonstrates a new and fundamentally different type of self-healing and shape memory in single crystalline faceted nano and microparticles of pure gold, which are plastically deformed with an atomic force microscope tip.

Annealing-induced recovery of indents in thin Au(Fe) bilayer films.

We employed depth-sensing nanoindentation to produce ordered arrays of indents on the surface of 50 nm-thick Au(Fe) films deposited on sapphire substrates. The maximum depth of the indents was approximately one-half of the film thickness. The indented films were annealed at a temperature of 700 °C in a forming gas atmosphere.

Cross-Split of Dislocations: An Athermal and Rapid Plasticity Mechanism.

The pathways by which dislocations, line defects within the lattice structure, overcome microstructural obstacles represent a key aspect in understanding the main mechanisms that control mechanical properties of ductile crystalline materials. While edge dislocations were believed to change their glide plane only by a slow, non-conservative, thermally activated motion, we suggest the existence of a rapid conservative athermal mechanism, by which the arrested edge dislocations split into two other edge dislocations that glide on two different crystallographic planes. This discovered mechanism, for which we coined a term "cross-split of edge dislocations", is a unique and collective phenomenon, which is triggered by an interaction with another same-sign pre-existing edge dislocation.