Full text loading...
Experimental load vs deformation curve (dots) and FEA model (solid line) for a 20 nm diameter NT and 15 nm radius indenting tip.
Models used in MD simulations. [(a) and (b)] Double-wall NT with inner and outer tube diameters of 2.6 nm and 3.9 nm, respectively. The tube is compressed between two molybdenum layers with fixed atoms to simulate an infinite, nondeformable tip. [(c) and (d)] The double-wall NT is approximated by an infinite double layer. The small, nondeformable Mo tip has a diameter of approximately 4 Å at its apex. Mo and S atoms are shown as red and yellow spheres, respectively.
(a) Energy vs normalized deformation curve for a double-walled NT pressed between two fixed Mo layers to simulate a large tip [Fig. 2(a)]. The curve can be fitted by a harmonic function (solid line, ) showing elastic behavior to 25% deformation. (b) The force vs normalized deformation curve obtained from the medium tip shows a plateau, which can be ascribed to the formation of a local depression in the NT. Maximum deformation of 25% corresponds to 5 Å deformation of this 2 nm diameter NT. (c) Experimental force curve obtained with a 15 nm radius tip on 20 nm diameter NT, showing semiquantitative correspondence with curve in (b).
Radial modulus of NTs. Values (in gigapascal) obtained from AFM nanoindentation experiments fitted with a finite element model to derive the radial modulus.
Article metrics loading...