Background:
Laser ablation method has high-yield and pure SWCNHs. On the other hand,
arc discharge methods have low-cost production of SWCNHs. However, these techniques have more
desirable features, they need special expertness to use high power laser or high current discharge that
either of them produces very high temperature. As for the researches, the temperatures of these techniques
are higher than 4727°C to vaporize the graphite. So, to become aware of the advantages of
SWCNHs, it is necessary to find a new way to synthesize SWCNHs at a lower temperature. In other
words, reaction field can be expandable at a moderate temperature. This paper reports a new way to
synthesize SWCNHs at an extremely reduced temperature.
Methods:
According to this study, the role of N2 is the protection of the copper holder supporting the
graphite rod by increasing heat transfer from the holder. After the current of 70 A was supplied to the
system, the temperature of graphite rod was raised to 1600°C. It is obvious that this temperature is
somehow higher than the melting point of palladium, 1555°C, and much lower than graphite melting
point, 3497°C.
Results:
Based on the results, there are transitional precursors simultaneous with the SWCNHs. This
composition can be created by distortion of the primary SWCNTs at the higher temperature. Subsequently,
each SWCNTs have a tendency to be broken into individual horns. With increasing the concentration
of the free horns, bud-like SWCNHs can be produced. Moreover, there are individual horns almost
separated from the mass of single wall carbon nanohorns. This structure is not common in
SWCNHs synthesized by the usual method such as arc discharge or laser ablation. Through these regular
techniques, SWCNHs are synthesized as cumulative particles with diameters about 30-150 nm.
Conclusion:
A simple heating is needed for SWCNTs transformation to SWCNHs with the presence of
palladium as catalyst. The well-thought-out mechanism for this transformation is that SWCNTs were
initially changed to highly curled shape, and after that were formed into small independent horns. The
other rout to synthesize SWCNHs is the pyrolysis of palm olein at 950°C with the assistance of zinc nitrate
and ferrocene. Palm olein was used as a promising, bio-renewable and inexpensive carbon source
for the production of carbon nanohorns.
