The Mechanism Of Carbon Nanocoils Growth

Carbon nanocoils exhibit exceptional mechanical, electrical and magnetic properties due to the combination of their helical morphology and the fascinating properties of carbon nanotubes. They are expected for uses in high performance composites, electromagnetic wave absorbers, and field emission device. Research on the growth mechanism of carbon nanocoils is significant for highly efficient synthesis of carbon nanocoils. In this paper, we have studied the formation mechanism of catalyst particles and the roles played by catalyst.First, we study the formation process of catalyst in the initial stage of carbon nanocoil synthesis by a thermal chemical vapor deposition method. A series of variance in morphology of catalyst is observed in the processes of calcination and reduction of catalyst, absorption of carbon and also the growth of carbon nanocoil buds. It is found that the catalyst precursors with nanoscaled porous structures are formed after calcination. By feeding a small amount of acetylene, these deoxidized Fe-Sn metallic particles migrate and aggregate with each other. The sizes of these particles increase continuously in the carbon absorption process. It is noted that the catalyst particles for carbon nanocoil growth have favorite sizes of 100 to 200 nm.Subsequently, we study the root fixation effect of carbon nanocoils. It is considered that the catalyst particles on the tip are used for coils growth, and the deposits on the bottom play an important role in fixing the root of coil to balance torsion force induced by coil growth. The Si-O-Si grid structure formed by TEOS sol is used for fixing the root of coils. Simultaneously, taken advantage of glass softening at high temperature to fix the root of coils, the glass and ITO glass are used as substrate. The results indicate that the TEOS sol is feasible for the fixed root growth of single carbon nanocoil. The ratio of Sn/In in the catalyst is adjusted by further etching the thickness of ITO films on the substrate. The single carbon nanocoil growth is realized ultimately, which can be attributed to the fixed root of coils. It demonstrates that the fixed root is important to balance the force caused by the helical growth of coils, which is significant for generating a carbon nanotube with regular coiled structure. It is also concluded that in the catalyst the elemental ratio of Fe/Sn/In is crucial to the synthesis of carbon nanocoils.