Unveiling Core-Shell Structure Formation in a Ni₃Fe Nanoparticle with In Situ Multi-Bragg Coherent Diffraction...

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Chemistry

Background:

• Solid-state reactions are fundamental in materials science.
• Understanding nanoscale transformations is crucial for developing new materials.

Purpose of the Study:

• To investigate the structural evolution of a single Ni3Fe nanoparticle during a solid-state reaction at high temperatures.
• To reveal the mechanisms behind the formation of core-shell structures in nanoparticles.

Main Methods:

• Multireflection Bragg coherent diffraction imaging (BCDI) was used to track the evolution of nanoparticle structure, morphology, and deformation.
• In situ 3D imaging was performed at the nanometer scale with temperature variation.
• Atomistic simulations supported the experimental observations.

Main Results:

• A demixing process was observed at 600 °C under an Ar atmosphere.
• A highly strained core-shell structure emerged, characterized by two distinct lattice parameters (0.4% difference).
• Nanoparticle facets vanished, resulting in a rounded core-shell structure with a Ni-rich outer shell due to preferential iron oxidation.

Conclusions:

• In situ multireflection BCDI is a powerful technique for studying nanoscale solid-state reactions.
• The study provides detailed insights into the mechanisms of core-shell transition during solid-state reactions in nanoparticles.