Endofullerenes with Metal Atoms Inside as Precursors of Nuclei of Single-Walled Carbon Nanotubes

Abstract

Thermodynamic estimations have been made which show that amorphous carbon cannot be the source of single-walled carbon nanotube growth during carbon/metal vapor condensation. Thus the source of carbon material for nanotube growth seems to be small carbon clusters into gas phase or clusters in the adsorbed state on the nanotube surface. Kinetic analysis of carbon/metal vapor condensation in the arc process was performed and showed that metal vapor becomes supersaturated at temperatures that are close to the temperature of the highest rate of fullerene shell formation. A new model of the nucleation of single-walled carbon nanotubes is proposed. In the model an endometallofullerene serves as the precursor of a nanotube nucleus, and the nucleus itself forms as an adduct arising after metal atoms attach to the endofullerene shell. The relative efficiencies of La/Ni, Gd/Ni, Ce/Ni, and Pr/Ni catalysts, in comparison with Y/Ni catalyst, were measured, and their high efficiency in buckytube formation was demonstrated. This fact was explained by the double action of a metal catalyst in buckytube nucleus formation. First, metal takes part in the formation of endometallofullerenes. Second, the metal atoms attach to the endofullerene shell to transform an endofullerene into a nanotube nucleus. The high performance of bimetallic catalysts lies in adjusting the values of two metal concentrations separately for each of these purposes. In accordance with observations, the proposed model predicts increasing size of endofullerenes with increasing concentration of the metal that controls endofullerene formation.

Nylon-6 and single-walled carbon nanotubes polyamide composites

“…Synthesis and characterization of the SWCNTs supplied by the company are described in detail. [41][42][43] Synthesis of PIs PI-NH 2 -I and PI-NH 2 -II (Co)PIs PI-NH 2 -I and PI-NH 2 -II were synthesized by onestep high-temperature polycondensation of respective tetracarboxylic acid dianhydrides and diamines in m-cresol at 180 C in accordance with previously reported procedure. 44 Both PI-NH 2 -I and PI-NH 2 -II were prepared at diamines and tetracarboxylic acid dianhydrides molar ratio equal to 1.0:0.9.…”

Comprehensive spectral and instrumental approaches for the easy monitoring of features and purity of different carbon nanostructures for nanocomposite applications

“…In this case, fullerene molecular clusters will provide vibrational modes characterized by a precise dipole variation, whereas graphenic materials such as carbon nanotubes will not be appreciatively detected [30]. Metal catalyzed synthesis of CNT, however, will generally yield non-fullerenic carbon phases, as the metal catalysts favor the production of extended nanostructures [31,32]. Possible traces of fullerenes within CNT materials can be however simply extracted and eliminated by extraction in an aromatic solvent (e.g., toluene, 1,2-dichlorobenzene), in which fullerene species are the only soluble molecular carbon allotropes [33].…”

Synthesis of carbon nanostructures in an RF induction plasmatron

“…These Raman spec tra are typical of single wall CNTs. As follows from the low frequency part of the spectrum (where the contri bution of the breathing modes of CNTs is detected), the nanotube diameter is mainly 1.2 nm (band at 180 cm -1 ), and a relatively small fraction of nanotubes 0.9 nm in diameter (band at 220 cm -1 ) is also detected [10][11][12][13]. Peak D in the spectra is observed at a fre quency of 1342 cm -1 , which is also characteristic of single wall CNTs (Fig.…”

“…The point is that the Raman scattering cross section of CNTs is significantly larger than that of other carbon materials [10][11][12][13]. Therefore, possible impurities of other phases, such as graphite, weakly manifest them selves in Raman spectra against the background of CNT spectra.…”

“…Therefore, the carbon nanotubes detected from Raman spectra either do not form periodic structures and, correspondingly, cannot manifest themselves in X ray diffraction pat terns or have a low concentration in the samples as compared to graphite. The final conclusion regarding the CNT concentration in the samples can only be drawn after the separation and cleaning of CNTs, which is a separate subject of investigation [10][11][12][13].…”