Towards the low temperature growth of uniform diameter multi walled carbon nanotubes by catalytic chemical vapour deposition technique

Abstract

Mesoporous MCM-41 molecular sieves containing f-block transition elements (gadolinium) with various Si/Gd ratios (50, 75 and 100) were synthesised by a hydrothermal method. Their mesoporous structure was confirmed by X-ray diffraction, nitrogen sorption studies, thermogravimetric analysis, scanning and transmission electron microscopy. The local environment of Gd in the material was studied by electron paramagnetic resonance. The compatibility of the catalyst for the synthesis of uniform diameter CNTs by varying the temperature from 400 to 650°C with fixed flow rates of N 2 and C 2 H 2 (140 ml/min and 40 ml/min, respectively). The product is mostly metal containing thin MWCNTs with diameter of 10a20 nm. Characterisation shows that a combination of Gd-MCM-41 (100) catalyst gives a high yield of high quality MWCNTs under optimum growth conditions. [7]. The major drawback of arc discharge and laser evaporation methods is that they are extremely uncontrolled in terms of process parameters, resulting in CNTs that contains significant fractions of unwanted material and that are difficult to manipulate and assemble in specific designs. CVD method is based on the thermal decomposition of hydrocarbon compounds over transition metal catalyst particles.It appears to be a simple and economic technique to synthesize this kind of material at a low temperature, ambient pressure and it represents the best hope for large scale production.To date, all the metal-catalyzed CNT growth studies have mainly focused on transition metals. Curiously, f-block transition elements also referred to as inner transition elements have still not been well explored. One reason could be that inner transition elements are not known to be highly catalytic as the transition elements. It has also been suggested that lanthanoids such as gadolinium and europium exhibit insufficient carbon solubility, slow carbon diffusion, and limited carbide formation to catalyze CNT growth [8]. Recently, gadolinium and europium were used

Synthesis of Multi-Walled Carbon Nanotubes by Fluidized-Bed Chemical Vapor Deposition over Co/Al₂O₃

“…The decreased level of MWCNT production with respect to temperatures above 600°C is possibly due to the rapiddecomposition of ethylene catalyzed by the metal catalyst to form a deposit of amorphous carbon, as previously reported elsewhere (Gulino et al, 2005;Morançais et al, 2007;Somanathan and Pandurangan, 2010).…”