Atomistic dynamics of deformation, fracture, and joining of individual single-walled carbon nanotubes

The tensile deformation process of individual single-walled carbon nanotubes (SWCNTs) was in situ observed with measurements of the mechanical properties by transmission electron microscopy combined with the functions of scanning probe microscopy. The values of Young’s modulus, tensile stress and strain at the fracture of SWCNTs are $950\pm 130\mathrm{GPa}$, $25\pm 1\mathrm{GPa}$, and $0.30\pm 0.03$, respectively. It was shown that two tips of fractured SWCNTs can be recovered to produce a single tubular structure by contact under compressive force and bias voltage. The in situ observations also demonstrated the formation of carbon monatomic wires during the fracture process of SWCNTs.

Figure 1

Time-sequential series of high-resolution images of a single-walled carbon nanotube (SWCNT): (a)–(c) tensile deformation process, (d)–(f) joining process. The illustrations in (g)–(l) correspond to the images in (a)–(f). The SWCNTs formed between the graphitized surfaces of a tip of the cantilever (A) and that of the carbon plate (B). The minimum diameter of the SWCNT is $0.9\mathrm{nm}$ in (a). With stretching along the direction indicated by the bold arrow in (a)–(b), a neck forms as seen in (b), and the SWCNT finally fractures as in (c). After complete fracture, when the tip of the SWCNT on the right-hand side compresses that of the opposite SWCNT at the applied voltage of $2.2\mathrm{V}$, one stable tubular structure is reproduced as shown in (f).

Figure 2

Variations in tensile force, minimum cross-sectional area, tensile stress, and strain as a function of time, and the stress-strain relation during the tensile deformation process of Fig. 1. Times of a–c correspond to those at which Figs. 1a, 1b, 1c were observed.

Figure 3

(a)–(c) Time-sequential series of high-resolution images of the fracture process of a carbon wire of monatomic width and (d) an illustration of (b). A carbon monatomic wire appears between the SWCNTs before the fracture, as indicated by an arrow in (d).

Figure 4

(a) Variation in tensile force as a function of time and (b) histogram for the value of the tensile force corresponding to Figs. 3a, 3b, 3c. In the histogram, strong peaks are recognized at 0.06, 0.11, and $0.16\mathrm{nN}$. The minimum value of the tensile force corresponds to the value at the smallest width of the carbon monatomic wire in Fig. 3b.