Effect of ferrocene concentration on the quality of multiwalled CNTs grown by floating catalytic chemical vapor deposition technique

Abstract

Controllable synthesis of quality carbon nanotubes is a precondition for their broad applications. The objective of the work was to study the effect of catalyst concentration on the quality, diameter, length, alignment and crystallinity of the grown multiwalled carbon nanotubes (MWCNTs). To meet the stated objective, MWCNTs were successfully synthesized by using floating catalytic chemical vapor deposition technique. The ferrocene concentration was varied from 0.1 to 0.2 g and MWCNTs were synthesized with ethylene as a carbon precursor at reaction temperature of 850 • C. The grown MWCNTs were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The obtained data revealed that an increase in concentration of the ferrocene significantly affects the diameter, crystallinity and growth of nanotubes, however, negligible effect on the CNTs forest length was noticed. The dense, uniform and meadow like patterns of grown CNTs were observed for 0.15 g ferrocene. The average diameter of the grown CNTs was ranged from 32-75 nm. Above 0.15 g ferrocene, some of the grown CNTs were found defective and few black spots were also appeared in TEM images.

High Production of Carbon Nanotube Bundles with Fe₂O₃/Al₂O₃ Catalyst

“…The peak intensity ratio of the G and D-bands (I G /I D ) was frequently used to understand the structure, purity and quality of MWCNTs. This ratio (I D /I G ) also reflects the degree of disorder and the higher ratio explains the higher amorphous carbon content and defect formation [7,9]. It was observed that MWCNTs synthesized by the A 1 , A 2 , A 4 and A 5 catalysts possessed higher I D /I G ratios (1.2, 1.14, 0.90 and 1.1, respectively) as compared to that of the CNTs synthesized by the A 3 catalyst with intensity ratio of 0.78.…”

“…Since their discovery, CNTs have remained the main subject of most of the research investigation. Different methods have been used to produce carbon nanotubes such as arc discharge [4], laser ablation [5], solar energy furnace [6] and catalytic chemical vapor deposition (CCVD) [7]. CCVD has been identified as the most promising large-scale synthesis route toward CNTs.…”

“…CCVD has been identified as the most promising large-scale synthesis route toward CNTs. The CCVD process appears to be the easiest method to scale-up the production capacity at reduced cost [7]. However, regardless of these advantages, selection of an appropriate catalyst for bulk CNTs production still remains a challenge for researchers and producers.…”

Effect of Ferrocene Catalyst and Hydrogen Feed on Microstructures of Vertically Aligned MWCNTs

“…Owing to the exceptional anisotropic properties, aligned CNTs have been widely investigated for their mechanical, thermal and electrical applications with a significant effort directed at understanding and controlling their growth [1,2]. Untill today, the widely used CNTs synthesis technique is catalytic chemical vapour deposition (CCVD) because it enables the production of CNTs at low cost, easy to scale up and provides better control over the synthesis and growth parameters [3,4]. The floating catalytic chemical vapor deposition (FCCVD) is a kind of CVD in which vertically aligned CNTs can be produced over a metal substrate placed in reactive gaseous environment and in the presence of a catalyst [5].…”

“…The active catalyst, used for CNTs production in CVD reactors, contains the transition metals like Fe, Co, Ni, Pt, Mo, silicon or their alloys and substrates like CaO, MgO, SiO 2 and Al 2 O 3 [6][7][8]. The transition metals are capable of decomposing the carbon sources such as ethylene, methane, acetylene and benzene to initiate CNTs nucleation [4][5][6][7][8]. Shirazi et al [8] found that CNTs synthesized in CVD reactor using iron catalyst contain impurities in the form of amorphous carbon, graphite, nano-particles and metal catalysts.…”