3.2. Relationship between CNC yield and acetylene flow rate
Fig. 5a and b shows the morphologies of CNCs grown at the C2H2
flow rates of 50 and 100 sccm, respectively; the gas flow rates of Ar
and H2 were kept at 5000 and 100 sccm, respectively. Compared
with the CNCs shown in Fig. 2a, which were grown using 25 sccm
C2H2, no apparent morphological difference was observed among
these three samples, except that some straight CNFs were present
in the 25 sccm C2H2 sample, as indicated by the arrows in Fig. 2a.
The results indicated that a change in the concentration of the
carbon source gas did not alter the fundamental morphology of the
CNCs. However, the growth rate (mg/hr) of nanocarbonaceous
materials increased when the C2H2 flow rate increased, as shown in
Fig. 6. Also note that the fractions of CNCs in the synthesized
carbonaceous materials with the C2H2 flow rates of 25, 50, and 100
sccm were 85, 94, and 96%, respectively. This fraction was calculated
from the ratio of the total area of CNCs to that of all nanocarbonaceous
materials on the SEM images. As mentioned in