Nanomechanical testing of multiple twinned nanoparticles in-situ TEM
In the present paper we report the experimental and theoretical analysis of uniaxial loading to study mechanical properties of nanoparticles by direct compression inside a TEM. These experiments are sensitive to the sample and tip geometry limiting the accuracy of the measurements. Nevertheless, very valuable quantitative information can be obtained. It is found that an outstandingly high plasticity near to 100% present on some metal nanoparticles. Molecular dynamics (MD) calculations with as much as possible the same experimental conditions were carried out in order to understand the mechanism at the atomic level of the deformation process of the nanoparticles, and good agreement has been found among them. Three different particles containing twins, decahedral (Dh) and icosahedral (Ic) nanoparticles, and one single twinned (Ts) nanoparticle. The deformation process involves a displacement of the cantilever of about 1000 nm; therefore the experiments are watched at fairly low magnifications to avoid losing sight of the particles. Figure 1 shows two different decahedra before and after deformation. In Figure 1A-B the deformation was very slow to avoid tilting the particle. We can observe how the top part of the particle is flattened compared with the bottom part, which retains some pyramidal shape. The amount of true compressive strain was 80%. Figures 1C-F show an experimental sequence of a Dh nanoparticle while recording the force measurements (true stress vs. true strain is shown in Fig. 3).