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Abstract
There is strong interest in studying changes in mechanical properties with reducing grain size. The rational is that consequent dislocation glide cannot be sustained, resulting in an increase in material strength. However, this comes with the cost of a reduction in ductility. It has been shown that coherent twin boundaries in nanostructured Cu improve the ductility to 14% [Lu et al., Science 324 (2009) p. 349]. In this paper, we report for the first time the compression of individual nanoparticles using an in situ force probing holder in the transmission electron microscope. Four types of nanoparticles were tested, three with twin boundaries (decahedra, icosahedra and a single twin) and one free of defects (octahedral). Our results indicate the yield strength of the twinned nanoparticles is between 0.5 and 2.0 GPa. The total malleability for the twinned particles range from 80 to 100%. In addition, experimental results were reproduced by MD simulations of the compression phenomena and suggest that the outstanding mechanical properties are related with partial dislocation multiplication at twin boundaries.
Acknowledgements
The authors would like to acknowledge the following agencies: The Welch Foundation Agency, project AX-1615: Controlling the Shape and Particles Using Wet Chemistry Methods and Its Application to Synthesis of Hollow Bimetallic Nanostructures, the National Science Foundation (NSF) PREM grant number: DMR-0934218: Oxide and Metal Nanoparticles: The Interface between life sciences and physical sciences, and CONACYT-Mexico grant number: 106437. The authors would also like to thank the International Center for Nanotechnology and Advanced Materials (ICNAM) at UTSA, and the RCMI Center for Interdisciplinary Health Research (CIHR), and the project award number 2G12RR013646-11 from the National Center for Research Resources. For the intensive calculations, the authors would like to acknowledge the use of computational resources at the Texas Advanced Computer Center (TACC-UT) from University of Texas at Austin, TX, USA, and Centro Nacional de Supercomputo (CNS-IPICYT) at San Luis Potosi, Mexico. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center for Research Resources of the National Institutes of Health.