Raman diagnostics of multi‐wall carbon nanotubes with a small wall number

Abstract

Raman spectroscopy study of multi‐wall carbon nanotubes (MWNTs) of different diameters (with a small controllable number of walls) produced using Fe–Co catalyst with a variable size of the same active component has been performed. We have characterized as produced MWNTs with different diameters (series 1) and two types of tubes with fixed mean diameters (∼10 and 20 nm) heated in a flow of pure argon at various temperatures (2200, 2600 and 2800 °C – series 2). The Raman spectra of MWNTs have been registered in three spectral regions, corresponding to D (disorder‐induced), G (graphite) and 2D (two‐phonon scattering) bands. A ratio of intensities I2D/ID for tubes of series 1 has demonstrated almost a linear dependence on the nanotube diameter. After heating (series 2), D (disorder‐induced) Raman band has shown a substantial decrease in intensity. The variation of the Raman spectra parameters is discussed in terms of defectiveness of nanotubes.

Reinforcement of CVD grown multi-walled carbon nanotubes by high temperature annealing

“…The HRTEM images showed that the annealing temperature 2200 o C considerably improved the outer layers but was sometimes was not enough to eliminate all the defects of the inner walls. The gradual structural development of MWNTs with annealing temperature increase was also confirmed by Raman-spectroscopy 34 which showed the increase of the relative intensities of 2D and D peaks (I2D/ID) with the increased annealing temperature testifying the systematic structural improvement of MWNT wall regularity. The temperature and field dependences of conductivity measurements of annealed MWNTs corroborate with the above findings.…”

Manifestation of coherent magnetic anisotropy in a carbon nanotube matrix with low ferromagnetic nanoparticle content

“…The first overtone of the D band (2D band) is usually found at ≈2715 cm −1 , is always present for CNT Raman spectra and its intensity tends to increase with graphitization [43]. Moreover, as it has been shown recently, carbon defects are clearly manifested by analyzing the ratio of intensitiy I 2D /I D [44]. It has been demonstrated that the 2D/D ratio intensity is increased with the decrease in the defectiveness of carbon which occurs when the nanotube diameter increases [44,45].…”

On-chip purification via liquid immersion of arc-discharge synthesized multiwalled carbon nanotubes

“…The high crystallinity of AD-MWNTs should show up in the Raman spectra as a weak D-band, which is associated with disorder in graphitic materials [1,30]. In a nice work on Raman spectroscopy of bulk CVD MWNT material [31], it was shown that a high temperature treatment (2800…”