The nanoindentation of a copper substrate by single-walled carbon nanocone tips: amolecular dynamics study

Abstract

This study dealt with deep nanoindentation of a copper substrate with single-walled carbonnanocones (SWCNCs) as the proximal probe tip, using molecular dynamics (MD)simulations. As an important feature, during the indentation the end part of the SWCNCtip will suffer a narrowing effect due to the radial component of resistant compression fromthe substrate and then forms into a somewhat flat arrowhead-like shape. Theeffective cross-sectional area of the SWCNC tip inside the substrate that theresistant force is acting on therefore is reduced to lower the normal resistantforce on the tip. The narrowing effect is more significant for longer SWCNC tips.Two categories of SWCNCs are therefore classified according to whether theSWCNC tip buckles at its part inside or outside the substrate. SWCNCs of the firstcategory defined in this paper are found able to indent into the substrate upto a desired depth. Further analyses demonstrate that a longer SWCNC tip ofthe first category will encounter smaller repulsive force during the indentationand thus require less net work to accomplish the indentation process. Raisingtemperatures will weaken the narrowing effect, so an SWCNC tip of the first categoryalso encounters greater repulsive force and larger net work in the indentationprocess performed at a higher temperature. Notably, a permanent hollow hole withhigh aspect ratio will be produced on the copper substrate, while copper atomsin close proximity to the hole are only slightly disordered, especially when theindentation is manipulated at a lower temperature by using a longer SWCNC tip.