Morphology optimization of CCVD-synthesized multiwall carbon nanotubes, using statistical design of experiments

Abstract

The possibility of optimization of morphological features of multiwall carbon nanotubes (MWCNTs) using the statistical design of experiments (DoE) is investigated. In this study, MWCNTs were synthesized using a catalytic chemical vapour deposition (CCVD) method in a horizontal reactor using acetylene as the carbon source. The effects of six synthesis parameters (synthesis time, synthesis temperature, catalyst mass, reduction time, acetylene flow rate and hydrogen flow rate) on the average diameter and mean rectilinear length (MRL) of carbon nanotubes were examined using fractional-factorial design (FFD) coupled with response surface methodology (RSM). Using a 2III6–3 FFD, the main effects of reaction temperature, hydrogen flow rate and chemical reduction time were concluded to be the key factors influencing the diameter and MRL of MWCNTs; then Box–Behnken design (BBD) was exploited to create a response surface from the main factors. The total number of required runs is 26: 8 runs are for FFD parameter screening, 17 runs are for the response surface obtained by the BBD, and the final run is used to confirm the predicted results.

Fluidized bed catalytic chemical vapor deposition synthesis of carbon nanotubes—A review

“…As a result, they proposed that temperature is a dominating factor for CNT diameter control. The same conclusions have been also reported by other researchers [9,10,25,[69][70][71]. The main effects of increasing the reaction temperature are to increase the metal particle size during the CVD growth of CNTs, and consequently the nanotube diameter.…”

“…The most commonly used carbon sources are ethylene [13,32,50,75,76], acetylene [16,33,47,58,70], methane [28,41,42,51,54,61,63], ethanol [19,30,64,80] and CO [21,46]. Recently, Yen et al [84] reported that CNTs could be synthesis from solid-stated polymers-polycarbosilane and polyethylene using FBCVD.…”

Influence of catalyst thickness and temperature gradient on MWCNT growth and morphology in TCVD process

“…Several authors have the same conclusions as our results [19][20][21]. However others have conflicting results for the impact of temperature gradient on the diameter of tubes.…”

Effect of operating variables on synthesis of multi-walled carbon nanotubes in fluidized beds

“…In systems using a different carbon source, carbon yield with respect to reaction temperature shows the same trend, but optimal reaction temperatures vary (Morancais et al, 2007;Philippe et al, 2009;Son et al, 2008). In addition, CNT diameter and crystallinity vary depending on the reaction temperature (Muataz et al, 2006;Andrews et al, 2002;Kim et al, 2005;Nourbakhsh et al, 2007;Xiong et al, 2005;Yao et al, 2004). These results suggest that each system requires reaction temperature optimization.…”