title: Ostwald-Driven Phase Separation in Bimetallic Nanoparticle Assemblies.
abstract: The compositional stability of bimetallic nanoparticles (NPs) is crucial for many applications. We have studied the coarsening of amorphous carbon-supported Au-Pd NPs during annealing at 873 K. Using scanning transmission electron microscopy and energy-dispersive spectroscopy measurements, we show that, despite a complete miscibility of the two metals, the particle assembly undergoes a phase separation during annealing, which leads to two distinct populations: Au-rich NPs with a mean radius of 3.5 nm and large Pd-rich NPs with a mean radius of 25 nm. Thermodynamic calculations and kinetic Monte Carlo simulations explain this behavior that is driven by the competition between surface and mixing energy and by the different mobilities of the two atomic species.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris , 75005 Paris, France.
authors.forename: Geoffroy
authors.initials: G
authors.lastname: Prévot
authors.affiliation: Laboratoire de Matériaux et Phénomènes Quantiques, Bâtiment Condorcet, CNRS UMR 7162, Université Paris Diderot , 75013 Paris, France.
authors.forename: Nhat Tai
authors.initials: NT
authors.lastname: Nguyen
authors.affiliation: Laboratoire de Matériaux et Phénomènes Quantiques, Bâtiment Condorcet, CNRS UMR 7162, Université Paris Diderot , 75013 Paris, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Alloyeau
authors.affiliation: Laboratoire de Matériaux et Phénomènes Quantiques, Bâtiment Condorcet, CNRS UMR 7162, Université Paris Diderot , 75013 Paris, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Ricolleau
authors.affiliation: Laboratoire de Matériaux et Phénomènes Quantiques, Bâtiment Condorcet, CNRS UMR 7162, Université Paris Diderot , 75013 Paris, France.
authors.forename: Jaysen
authors.initials: J
authors.lastname: Nelayah
keywords: EDS; Ostwald ripening; TEM; gold; kinetic Monte Carlo; palladium; sintering