Background:
In this work, various carbon nanotubes (MWCNTs) were synthetized by the
spray pyrolysis method. Resulting nanoforest-like and bamboo-like carbon nanotubes, as well as Yjunctions
of carbon nanotubes, possess different shapes and morphology, depending on the kind of carbon
source used and on the number of iron particles on the furnace tube surface, which derives from
various concentrations of ferrocene catalyst.
Methods:
We used the spray pyrolysis method, using different carbon sources (n-pentane, n-hexane, nheptane,
and acrylonitrile) as precursors and two different concentrations of ferrocene as a catalyst.
Reactions of hydrocarbon decomposition were carried out at 800oC. The solution (hydrocarbon and
catalyst) was introduced with a syringe, with a flow of 1 mL/min and the synthesis time of 20 min. Argon
was used as carrier gas (1000 L/min). Preheater and oven temperatures were selected 180°C and
800°C, respectively, for each carbon source. The solution passed into a quartz tube placed in an oven.
Results:
According to the studies of carbon nanostructures, obtained from different precursors, it can
be proposed that the structures synthesized from n-pentane, n-hexane and n-heptane are formed by the
root growth method. The growth mechanism of MWCNTs was studied, confirming that the root
growth formation of products takes place, whose parameters also depend on furnace temperature and
gas flow rate. Dependence of interlayer distance (0.34-0.50 nm) in the formed MWCNTs on precursors
and reaction conditions is also elucidated. The formation of carbon nanotubes does not merely depend
on carbon precursors but also has strong correlations with such growth conditions as different catalyst
concentrations, furnace temperature and gas flow rate. Such parameters as the amount of catalyst and
synthesis time are also needed to be considered, since they are important to find minor values of these
parameters in the synthesis of forest-like carbon nanotubes and other structures such as bamboo-like
carbon nanotubes and Y-junctions in carbon nanotubes.
Conclusions:
As a result of the evaluation of interlayer distance in CNTs formed from different carbon
sources, a standard value of interlayer distance normally for CNTs is 0.34 nm and for pentane A (0.5
wt.%), hexane B (1 wt.%), toluene A (0.5 wt.%) the range is from 0.33 to 0.35 nm. In case of pentane and
acrylonitrile, under an increase of the catalyst concentration, an increase of the value of interlayer distance
takes place from 0.35 and 0.4 to 0.4 and 0.5 nm, respectively, but for hexane, heptane and cyclohexane,
an increase of the catalyst concentration maintains the same interlayer distance. This involves the use of
lower quantities of raw materials and, therefore less cost for obtaining these materials.
Synthesis and Characterization of Carbon Nanotubes Via Spray Pyrolysis Method
