Carbon-Nanotube Formation Mechanism Based on in Situ TEM Observations

Abstract

Carbon nanotubes (CNTs) have attracted much attention for their unique properties, although their formation mechanism is not well understood. The authors have been studying a technique to form CNTs by an electron beam that is carried out in a transmission electron microscope (TEM) and is compatible with in situ and real-time observation of the growth. The observation, where a precursor (polyyne-containing carbon) is heated and irradiated by an electron beam, shows that the growth occurs in two steps: rapid formation of rodlike carbon (first step) and slow graphitization of its wall (second step). The hollow inside the CNT is not formed in the first step and develops during the second. The formation mechanism is discussed in relation to in situ observations.

In Situ TEM observation of the gasification and growth of carbon nanotubes using iron catalysts

“…Recently, in situ observations of the growth of CNTs in a transmission electron microscope (TEM) have provided time-resolved, high-resolution images of the growth process, and TEM has thus become an excellent tool for the study of the growth mechanism of CNTs [9][10][11][12][13][14][15][16][17][18][19]. To study the roles played by metal catalysts, we have carried out the in situ growth of CNTs inside a high resolution environmental TEM (ETEM), using iron as catalyst.…”

A Chain‐Structure Nanotube: Growth and Characterization of Single‐Crystal Sb2S3 Nanotubes via a Chemical Vapor Transport Reaction

“…Although the growth mechanism of carbon nanotubes is not well understood, [13] it is believed that the formation of nanotubes requires the structural reconstruction of the graphite layers in the gas phase at high temperatures. For growing nanotubes based on chain-structure building blocks an alternative approach, a chemical vapor transport technique, was applied in this work.…”

Synthesis of vertically-aligned CNT arrays from diameter-controlled Fe₃O₄ nanoparticles

“…19) One possible explanation is that the higher catalytic ability of the much smaller NPs leads to excessive amorphous or graphitic carbon on the surface, resulting in encapsulation of the active sites on the catalyst NPs, 20) which deactivates them. Therefore, it is difficult to keep the sustainable growth of CNTs and retain their vertical orientation.…”