Mechanical Properties of Face-Centered Cubic Supercrystals of Nanocrystals

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• 作者：Enrico Tam ; Paul Podsiadlo ; Elena Shevchenko ; D. Frank Ogletree ; Marie-Paule Delplancke-Ogletree ; Paul D. Ashby
• 刊名：Nano Letters
• 出版年：2010
• 出版时间：July 14, 2010
• 年：2010
• 卷：10
• 期：7
• 页码：2363-2367
• 全文大小：370K
• 年卷期：v.10,no.7(July 14, 2010)
• ISSN：1530-6992

文摘

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.

Keywords:

Nanocrystals; supercrystals; modulus; hardness; fracture toughness