[P1-26] On the role of amorphous shells on mechanical properties of fcc Ni nanoparticles under compression
Nano-objects, such as nanoparticles, nanowires, nanopillars etc., are characterized by the large surface to volume ratio that, to a certain degree, defines their exceptional physical properties, significantly different from those in their bulk counterparts. In particular, nanocrystals are known for their promising mechanical properties: a size-dependent elastic regime, large values of yield strength and ductility, that are mainly linked to the dislocation nucleation from surface.
In this context, the various surface states of a sample are expected to lead to significant differences in terms of mechanical behavior. So far, in situ nano-compression experiments in the TEM occasionally report the presence of amorphous overlay at the top of nano-objects [1], while theoretical atomic scale studies are mainly focused on perfect crystalline systems [2, 3, 4].
Here we present a Molecular Dynamics (MD) study that aims to investigate the influence of amorphous shells on mechanical response of Ni nanospheres upon compression. In order to avoid complex effects of chemistry on the onset of plasticity, we focus on pure Ni compound, without adding alloying elements to the amorphous overlay. Based on multiple EAM potentials and various sample elaboration tests, a unique methodology that provides a reasonably slow “crystallization” rate of the amorphous Ni on fcc substrate is proposed. Then, mechanical properties of the designed 20 nm nanospheres with different shell thickness are investigated under uniaxial compression. The mechanical response of the composite systems is compared with that of purely crystalline and amorphous particles, with a particular focus on dislocation-based deformation processes.
References
[1] W. Han et al., Advanced Materials 27, 3385 (2015)
[2] J.-J. Bian & G.-F. Wang, J Comput Theor Nanosci 10, 2299 (2013)
[3] D. Mordehai et al., Acta Materialia 59, 5202 (2011)
[4] S. Bel Haj Salah et al., Comput Mater Sci 129, 273 (2017)
In this context, the various surface states of a sample are expected to lead to significant differences in terms of mechanical behavior. So far, in situ nano-compression experiments in the TEM occasionally report the presence of amorphous overlay at the top of nano-objects [1], while theoretical atomic scale studies are mainly focused on perfect crystalline systems [2, 3, 4].
Here we present a Molecular Dynamics (MD) study that aims to investigate the influence of amorphous shells on mechanical response of Ni nanospheres upon compression. In order to avoid complex effects of chemistry on the onset of plasticity, we focus on pure Ni compound, without adding alloying elements to the amorphous overlay. Based on multiple EAM potentials and various sample elaboration tests, a unique methodology that provides a reasonably slow “crystallization” rate of the amorphous Ni on fcc substrate is proposed. Then, mechanical properties of the designed 20 nm nanospheres with different shell thickness are investigated under uniaxial compression. The mechanical response of the composite systems is compared with that of purely crystalline and amorphous particles, with a particular focus on dislocation-based deformation processes.
References
[1] W. Han et al., Advanced Materials 27, 3385 (2015)
[2] J.-J. Bian & G.-F. Wang, J Comput Theor Nanosci 10, 2299 (2013)
[3] D. Mordehai et al., Acta Materialia 59, 5202 (2011)
[4] S. Bel Haj Salah et al., Comput Mater Sci 129, 273 (2017)