One-step synthesis of carbon nanotubes with secondary growth of carbon nanofibers: effect of chlorine, synthesis time and temperature

Abstract

Applications of carbon nanotubes (CNTs) in nanoscale electronic, filtration and adsorption platforms, requires the production of a high density network structure of the CNTs, which are intermeshed and/or chemically connected to each other. Strong network structures can be created if a stable connection is established through cross-linked CNTs. In a previous preliminary study, we reported the secondary growth of carbon nanofibers (CNFs) that grew on top of the CNTs during the CNT synthesis through decomposition of 1,2-dichlorobenzene (DCB). In the current study, we studied in detail the effect of synthesis time and temperature on the secondary growth of CNFs on CNTs as well as the morphology of CNFs that were grown. The amount of CNFs that grew onto the main CNTs increased with an increase in the synthesis time for reactions performed at 60 and 90 min but decreased with a 120 min growth time. It is proposed that decomposition of the DCB let to Cl/carbon radicals that either (i) eroded the CNT surface or (ii) deposited on the CNT surface, depending on the synthesis parameters. The CNFs grew at defective sites of the CNT walls. A synthesis temperature of 700 °C and synthesis time of 90 min were the growth conditions that resulted in the highest formation of the CNFs, presumably due to formation of defects that were uncovered by carbon deposition and allowed for the secondary growth of CNFs. The types of defects created were identified as on-site defects in the graphene sheet by Raman spectroscopy. All other studied synthesis temperatures (i.e. 600, 650, and 750) were unfavorable for growth of secondary CNFs.