2 research outputs found
GoldāCopper Nano-Alloy, ā<i>Tumbaga</i>ā, in the Era of Nano: Phase Diagram and Segregation
Goldācopper (AuāCu)
phases were employed already
by pre-Columbian civilizations, essentially in decorative arts, whereas
nowadays, they emerge in nanotechnology as an important catalyst.
The knowledge of the phase diagram is critical to understanding the
performance of a material. However, experimental determination of
nanophase diagrams is rare because calorimetry remains quite challenging
at the nanoscale; theoretical investigations, therefore, are welcomed.
Using nanothermodynamics, this paper presents the phase diagrams of
various polyhedral nanoparticles (tetrahedron, cube, octahedron, decahedron,
dodecahedron, rhombic dodecahedron, truncated octahedron, cuboctahedron,
and icosahedron) at sizes 4 and 10 nm. One finds, for all the shapes
investigated, that the congruent melting point of these nanoparticles
is shifted with respect to both size and composition (copper enrichment).
Segregation reveals a gold enrichment at the surface, leading to a
kind of coreāshell structure, reminiscent of the historical
artifacts. Finally, the most stable structures were determined to
be the dodecahedron, truncated octahedron, and icosahedron with a
Cu-rich core/Au-rich surface. The results of the thermodynamic approach
are compared and supported by molecular-dynamics simulations and by
electron-microscopy (EDX) observations
GoldāCopper Nano-Alloy, ā<i>Tumbaga</i>ā, in the Era of Nano: Phase Diagram and Segregation
Goldācopper (AuāCu)
phases were employed already
by pre-Columbian civilizations, essentially in decorative arts, whereas
nowadays, they emerge in nanotechnology as an important catalyst.
The knowledge of the phase diagram is critical to understanding the
performance of a material. However, experimental determination of
nanophase diagrams is rare because calorimetry remains quite challenging
at the nanoscale; theoretical investigations, therefore, are welcomed.
Using nanothermodynamics, this paper presents the phase diagrams of
various polyhedral nanoparticles (tetrahedron, cube, octahedron, decahedron,
dodecahedron, rhombic dodecahedron, truncated octahedron, cuboctahedron,
and icosahedron) at sizes 4 and 10 nm. One finds, for all the shapes
investigated, that the congruent melting point of these nanoparticles
is shifted with respect to both size and composition (copper enrichment).
Segregation reveals a gold enrichment at the surface, leading to a
kind of coreāshell structure, reminiscent of the historical
artifacts. Finally, the most stable structures were determined to
be the dodecahedron, truncated octahedron, and icosahedron with a
Cu-rich core/Au-rich surface. The results of the thermodynamic approach
are compared and supported by molecular-dynamics simulations and by
electron-microscopy (EDX) observations