Abstract
The multi-walled carbon nanotubes (MWCNTs) with controlled diameter distribution are useful in the fabrication of composite materials as reinforcement, due to their superior strength and toughness. Chemical vapor deposition (CVD) is a viable process to synthesize MWCNTs. In this investigation, an attempt has been made to study the effect of CVD process parameters (reaction temperature, flow rate of precursor gas, process time) on the mean diameter of MWCNTs. The MWCNTs of controlled diameter distribution was selectively grown on NiO catalyst supported by Al2O3 nano particles. The argon and acetylene were used as carrier and carbon precursor gas, respectively. The catalyst and carbon samples were characterized using field emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy and thermogravimetric/differential thermal analysis. From this investigation, it is understood that the increase in reaction temperature and flow rate of precursor gas increased the mean diameter of MWCNTs but increase in process time decreased the diameter. The diameter distribution and quality of MWCNTs are strongly influenced by the diameter of the catalyst particles.
Highlights
The significance of carbon nanotubes (CNTs) in the field of nanotechnology was noticed abundantly by the researchers, after the tubular needle growth model, proposed by the Ijima in 1991 [1]
(ii) If the precursor gas flow rate was less than 100 ml min−1, there was no tubular morphology in the samples, due to insufficient diffusion of carbon atoms to the catalyst particles
From the field emission scanning electron microscopy (FESEM) analysis, it is found that the multi-walled carbon nanotubes (MWCNTs) synthesized at 15-mins and 35-mins process time (Fig. 6) yielded controlled diameter distribution and defectless side wall of MWCNTs
Summary
The significance of carbon nanotubes (CNTs) in the field of nanotechnology was noticed abundantly by the researchers, after the tubular needle growth model, proposed by the Ijima in 1991 [1]. From the literature [21,22,23,24] review, the predominant CVD parameters which control the morphology and diameter of MWCNTs were identified They are (a) reaction temperature (b) flow rate of precursor gas (c) process time. (ii) If the precursor gas flow rate was less than 100 ml min−1, there was no tubular morphology in the samples, due to insufficient diffusion of carbon atoms to the catalyst particles. The methanol solution was removed via rotary evaporator and obtained material was heated at 150 °C overnight followed by grinding into a fine powder This resulting product, [11, 25] denoted as NiO/Al was used as a catalyst in this investigation. The MWCNTs samples were subjected to image and analytical techniques, to obtain optimized CVD parameters and to study their effect on structure, stability, and diameter of MWCNTs
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