Figure 1

(Color online) (a) TEM images of the as-grown ${\text{Fe}}_3\text{C}$-filled MWCNT and (b) the specimen which has been irradiated at $500°\text{C}$ after exposed to electron-beam irradiation with acceleration voltage of 80 kV at room temperature for $t=40\text{s}$, (c) 147 s, and (d) 500 s. [(e) and (f)] Typical gray scale intensity profiles of the labeled regions measured within MWCNTs only and both MWCNTs and ${\text{Fe}}_3\text{C}$. Labeled regions are shown in (b) and (d). Black (left) vertical dashed line in (f) represents the positions of certain crystal planes of the ${\text{Fe}}_3\text{C}$ measured in (b) and (d) with the same radial distance from the outer surface of the measured zone and the gray (right) dashed-solid line in (f) represents the position of a certain crystal plane of the ${\text{Fe}}_3\text{C}$ measured in (b) and (d), respectively. As the numbers of crystal planes between the black (left) vertical dashed line and the gray (right) dashed-solid line are the same, an expansion of the ${\text{Fe}}_3\text{C}$ core is clear.Reuse & Permissions

Figure 2

(Color online) Effects of SVs and DVs on the (a) radius and (b) Young’s modulus of a (10,10) SWCNT calculated with DFT and DFTB methods, where $R_0\left(=0.68\text{nm}\right)$ and $E_0$ ($=1.03$ or 1.18 TPa for DFT or DFTB) denote the radius and Young’s modulus of the pristine (10,10) SWCNT. Solid and dashed straight lines are the least-squares fitting of the DFT results for SVs and DVs, respectively. The two fitted lines for the effective radius are almost identical, whereas those for Young’s modulus are remarkably different. Inset in (a) shows the atomic networks of a (10,10) SWCNT with a typical 5–1 db SV (left) and a typical DV (right).Reuse & Permissions

Figure 3

(Color online) (a) Model predictions of the pressures $P$ exerted on the ${\text{Fe}}_3\text{C}$ core from the MWCNT vessels with different number of layers (as labeled) vs the knocked-off atom density $n$. (b) The model-predicted interwall spacings between the innermost two walls of the MWCNT extruders $d_{1–2}$ with different layers (as labeled) vs $n$. Results to the left of the vertical dashed line account for DVs with knocked-off atoms density $n$ from 0% to 8% and the results on the right-hand side account for the additional SVs with density from 0% to 3.1% as the DV density fixed at 8%.Reuse & Permissions