Study of Growth Enhancement of Multiwalled Carbon Nanotubes by Chlorine-Assisted Chemical Vapor Deposition

Abstract

In this paper, we investigate the effect of chlorine as a growth promoter in the synthesis of multiwalled carbon nanotubes (MWCNTs). We find that the addition of chlorine gas to the chemical vapor deposition process reduces the amount of amorphous carbon deposited on the MWCNT surfaces and results in a longer catalyst lifetime. By using optimum growth parameters, the catalyst remains active for 75 min. Moreover, the growth rate is also relatively high resulting in the maximum CNT array height of 3.5 mm. The MWCNT arrays grown with and without chlorine are compared.

Effect of growth temperature on the synthesis of carbon nanotube arrays and amorphous carbon for thermal applications

“…This two‐step growth process creates temperature dependent structural properties. At even higher temperatures (around 860 °C), a significant side effect of disproportionate hydrocarbon decomposition is the deposition of an as‐produced graphitic shell around the catalyst particles, preventing further reaction from the carbon feedstock needed for growth and thus reducing catalyst lifetime (often referred to as catalyst poisoning) , which causes growth termination. We see evidence of this catalyst poisoning at temperatures above 860 °C, which show a sudden drop in array height.…”

“…To the best of our knowledge, this is the largest presented temperature range with such small increments, used to study the temperature effects on CNT growth using chemical vapor deposition in detail. Special attention will be focused on the resulting array structure and crystallinity at growth temperature ranges of ∼780–850 °C since these are commonly reported temperatures for CCVD CNT synthesis . Scanning electron microscopy (SEM) was used to examine array heights, tube diameters, and the a‐C content on the canopy of the arrays.…”

The synthesis of carbon nanomaterials using chlorinated hydrocarbons over a Fe-Co/CaCO3 catalyst

“…Modification of CNTs has thus led to the creation of new functional and construction materials. 11 Doping of the carbonaceous materials with non-carbon atoms, such as nitrogen, [12][13][14][15][16][17][18][19] boron, [20][21][22][23][24] sulphur, [25][26][27][28][29] oxygen [30][31][32][33][34][35][36] and halogens 11,[37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] has been explored over the past two decades. Modification of the carbon surface and electronic properties has also been explored but the effect of chlorine (Cl) on the morphology of carbon nanomaterials is not well established.…”

“…It has been shown that incorporation of Cl in the CNMs results in surface functionalization, [41][42][43][44] ease of purification, 40,43,45,46 increased yields [47][48][49] and surface restructuring. 49,50 The presence of chlorine atoms thus produces materials with increased inner diameters, which results in filling of CNTs with metal particles [51][52][53] and provides a chemically modified pathway to an ordered carbon product.…”

“…43 Purification and growth of vertically aligned MWCNTs in the presence of Cl was also reported, which resulted in the synthesis of CNT arrays with 3.5 mm height. 44 The yield of MWCNTs increased from 10 % to over 50 % using an arc discharge method and KCl as a promoter. 47 CNMs produced from chlorobenzene were more ordered and their yield increased as compared to those obtained from benzene.…”