TY - JOUR
T1 - When More Is Less
T2 - Plastic Weakening of Single Crystalline Ag Nanoparticles by the Polycrystalline Au Shell
AU - Sharma, Amit
AU - Amodeo, Jonathan
AU - Gazit, Nimrod
AU - Qi, Yuanshen
AU - Thomas, Olivier
AU - Rabkin, Eugen
N1 - Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/9/28
Y1 - 2021/9/28
N2 - 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. Our molecular dynamics simulations demonstrate that particle weakening at low strains is attributed to the plasticity confinement in the polycrystalline shell, in which the grain boundaries play a dual role of dislocations sources and sinks. At higher strains, the plasticity within the Ag core is initiated by the dislocations nucleating at the Ag-Au interphase boundary. The widespread of energy barriers for dislocations nucleation at the interphase boundaries and their lower value as compared to the barriers for surface nucleation ensure particle weakening and more homogeneous deformation. The results of this study show that adding imperfect material to superstrong single crystalline metal nanoparticles makes them weaker. At the same time, thin nanocrystalline coatings can be employed to improve the formability of metals at the nanoscale.
AB - 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. Our molecular dynamics simulations demonstrate that particle weakening at low strains is attributed to the plasticity confinement in the polycrystalline shell, in which the grain boundaries play a dual role of dislocations sources and sinks. At higher strains, the plasticity within the Ag core is initiated by the dislocations nucleating at the Ag-Au interphase boundary. The widespread of energy barriers for dislocations nucleation at the interphase boundaries and their lower value as compared to the barriers for surface nucleation ensure particle weakening and more homogeneous deformation. The results of this study show that adding imperfect material to superstrong single crystalline metal nanoparticles makes them weaker. At the same time, thin nanocrystalline coatings can be employed to improve the formability of metals at the nanoscale.
KW - core-shell nanoparticles
KW - dislocation nucleation
KW - grain boundaries
KW - nanoscale plasticity
KW - silver nanoparticles
UR - http://www.scopus.com/inward/record.url?scp=85113933229&partnerID=8YFLogxK
U2 - 10.1021/acsnano.1c02976
DO - 10.1021/acsnano.1c02976
M3 - 文章
C2 - 34379398
AN - SCOPUS:85113933229
SN - 1936-0851
VL - 15
SP - 14061
EP - 14070
JO - ACS Nano
JF - ACS Nano
IS - 9
ER -