Carbon nanotubes growth from C2H2 and C2H4/NH3 by catalytic LCVD on supported iron–carbon nanocomposites

Laser-assisted growth of carbon nanotubes—A review

“…Morjan et al 74,86 investigated the influence of acetylene and ethylene precursor gas on LACVD growth. The authors reported that their experiments did not lead to any CNT growth by only using ethylene as a feedstock gas which was consistent with their previous work.…”

“…This effect is larger when the ethylene gas is directly heated in the gas phase by the laser as well, which can explain the lower quality and larger diameter CNTs at higher ethylene concentration. 86,87 Some addition of ammonia-gas is commonly used to improve the growth by ensuring the presence of nucleation sites on the catalyst 86 and preventing the formation of amorphous carbon. 54 It can also be used to reduce the oxidized catalyst and remove amorphous carbon.…”

“…However, in combination with laser-assisted growth, too high concentrations of ammonia were found to decrease the quality of the CNTs. 86 This was likely a result of the low absorption of ammonia gas at the laser wavelength causing cooling effects.…”

“…Laser-assisted CVD research shows a wide variety of catalysts as well. The early reports used Fe(CO) 5 as catalyst precursor, 73,74,79,86,87 but iron has been reported most. 78,93,94,[98][99][100][101]107 The control of catalyst morphology allows for a better control of the process, although there has not been a significant advantage of laser-assisted CVD over other CVD methods with respect to catalyst morphology control.…”

“…113 Using precreated catalyst nanoparticles with a narrow diameter distribution allowed for a greater control over the resulting nanotube diameters. 86,87 As an explanation for the observed widening of the nanotube diameter distribution, the tendency for the nanoparticles to cluster has been proposed. This tendency occurs when the substrate and catalyst have a higher temperature resulting in larger particles.…”