Direct Evidence of Atomic Structure Conservation Along Ultra-Long Carbon Nanotubes

Abstract

The atomic structure of ultralong carbon nanotubes obtained by catalytic chemical vapor deposition in the kite growth mode has been studied along the nanotube length via electron diffraction and high-resolution transmission electron microscopy. Contrary to other techniques, electron diffraction studies provide a direct determination of the chiral structure of nanotubes. These studies demonstrate that the chirality of the nanotubes remained constant all along their length (i.e., up to several hundreds of micrometers). A tendency of kite-growth nanotubes to be double-walled has been observed as well as a preferential distribution toward high-chiral angles configuration. Furthermore, the studies yield a metallic:semiconducting ratio close to the one expected from a natural distribution of nanotubes (1:2).

Optical visualization and polarized light absorption of the single-wall carbon nanotube to verify intrinsic thermal applications

“…As shown, the thermal conductivity of SWCNTs is approximately 4000 W (K?m) 21 at approximately 250 6 C in our original steps. We attribute this appealing value to the following factors: (i) ultralong SWCNTs that are grown using the flowing mechanism have a nearly ideal crystalline structure, which eliminates unnecessary scattering by defects; (ii) the suspended naked SWCNTs have an increase in thermal conductivity of over 30% compared with the supported SWCNTs because of the elimination of scattering at the substrate-SWCNT interface 34 ; (iii) our method avoids difficult measurements of the input power and thermal boundary resistance (TBR); and (iv) possible overestimation of g' in our ice-enclosing configuration.…”

“…When the temperature of the stage decreased, the individual suspended SWCNTs gradually became visible as a wire across the slit under an optical microscope, as shown in Figure 1d and 1e. We identified the Raman spectrum of the shell, which had an O-H stretching vibration mode at approximately 3200 cm 21 . Thus, we ascertained that, as long as the temperature was sufficiently low, the supercooling water vapor in the surrounding would rapidly condense onto the nanotubes to form a unique SWCNT-ice core-shell structure of a few micrometers.…”

“…MD simulations have predicted the TBC of a SWCNT surrounded by liquid molecules as 1.6 mW (m 2 ?K) 21 33 . Here, we use g < 0.1 mW (m 2 ?K) 21 and g9 < 1.6 mW (m 2 ?K) 21 .…”

“…Despite its obvious importance, a reliable experimental determination of the intrinsic properties of SWCNTs, particularly at the single-tube level, remains a challenge because of the tiny sectional area and enormous difficulty in nanotube manipulation, which in fact hampers its wide use. From the theoretical side, an equilibrium molecular dynamic (MD) simulation has suggested that the lattice thermal conductivity of a (10, 10) SWCNT reaches the maximum value of approximately 37 000 W (K?m) 21 at 100 K and decreases to approximately 6600 W (K?m) 21 at 300 K 1 . However, because of the diversity of measuring methods and sample qualities, the experimentally measured thermal conductivity value (k) significantly varies from 200-25 000 W (K?m) 21 2-5 .…”

“…However, intrinsic thermal response study on individual nanotube remains missing because individual CNT's manipulation and visualization are challenging. Recently, a flowguided synthesis method was reported to grow ultra-long nanotubes with perfect crystalline structure (maintaining the chirality without any change for more than hundreds of micrometers 21 ). Therefore, the ultra-long nanotube is considered an ideal object to characterize intrinsic nanotube properties, particularly the suspended nanotube with unique superiority in avoiding any effects from the substrate 12,22 .…”