Coalescence-induced crystallisation wave in Pd nanoparticles.

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Palladium nanoparticles are crucial for catalysis, hydrogen storage, and gas sensing.
• Nanoparticle performance is highly dependent on surface structure and active site morphology.
• Nanoparticle coalescence significantly influences the final structure of active sites.

Purpose of the Study:

• To investigate the mechanisms governing palladium nanoparticle coalescence.
• To understand how surface structure evolves during coalescence.
• To correlate coalescence mechanisms with potential applications.

Main Methods:

• Classical molecular dynamics (MD) simulations.
• Magnetron-sputtering inert gas condensation deposition.
• High-resolution transmission electron microscopy (HRTEM) for structural analysis.

Main Results:

• Initial interactions driven by surface energy minimization formed interfaces/necks.
• Atomic rearrangements triggered crystallization waves in amorphous nanoparticles.
• Formation of mono- or polycrystalline face-centered cubic (fcc) structures observed.
• Almost-epitaxial alignment, twins, and surface protrusions formed in crystalline nanoparticles.

Conclusions:

• Palladium nanoparticle coalescence involves both surface energy minimization and dynamic atomic rearrangements.
• Coalescence leads to the formation of ordered crystalline structures with specific features like twins and protrusions.
• Understanding these mechanisms is key to controlling nanoparticle structure for optimized applications.