Mechanical behavior of core-shell nanostructures

Nanotexturing reduces the effective contact between surfaces in relative motion, which can result in a lower coefficient of friction. However, nanotextured surfaces lack structural integrity, resulting in permanent deformation even at moderate contact forces. Therefore, core-shell nanostructures (CSNs) have been developed to protect the structural integrity of nanotextured surfaces. These CSNs can withstand higher contact forces, might include some plastic deformation (dislocations), but during unloading there is no evidence of residual plastic deformation. Therefore, the CSN is deformation resistant. In the current study, molecular dynamics simulations are used to study the effect of core (aluminum) radius, shell (amorphous silicon) thickness, and the random atomic distribution in the amorphous shell, on mechanical properties of core-shell nanostructures. The results suggest that core radius does not have a significant influence on the initial plastic deformation of the CSN. The shell thickness should be chosen so that the core to shell ratio is less than two to have deformation resistant CSNs. Further we observe that with an increase in core radii or shell thickness, the ability of a CSN to fully recover decreases. These results will help in the design of deformation resistant surfaces for MEMS/NEMS applications.