Mechanical properties of face-centered cubic supercrystals of nanocrystals.
We report the first nanoindentation studies of well-ordered nanocrystal supercrystals composed of 7 nm lead sulfide nanocrystals stabilized with oleic acid ligands as a model system. Their modulus and hardness were found to be similar to hard polymers at 1.7 GPa and 70 MPa, respectively, and the fracture toughness was 40 KPa/m(1/2), revealing the brittle nature of these materials. The mechanical properties are dominated by the organic capping agents surrounding the inorganic cores. The close-packed structure distributes stress evenly increasing the modulus and hardness. The relatively short ligands are not likely to be highly interdigitated leading to low dissipation during crack propagation and a low-fracture toughness value.
Tam
Enrico
E
Chemicals and Materials Department, Universite Libre de Bruxelles, Bruxelles, Belgium.
Podsiadlo
Paul
P
Shevchenko
Elena
E
Ogletree
D Frank
DF
Delplancke-Ogletree
Marie-Paule
MP
Ashby
Paul D
PD