Formation of catalyst particles for carbon nanocoil growth

We have studied the formation process of Fe-Sn-O catalyst particles in the initial stage of carbon nanocoil synthesis by a thermal chemical vapor deposition method. A series of variance in height and morphology of catalyst particles are observed in the processes of calcination and reduction of catalyst, absorption of carbon and also the sequential growth of carbon nanocoil buds. It is found that the catalyst precursors with nanoscaled porous structures are formed on the substrate after calcination. By continuous feeding a small amount of acetylene in the reaction chamber, these precursors are gradually deoxidized and then generate lots of Fe-Sn metallic particles with different shapes, which migrate and aggregate with each other. The sizes of these particles increase continuously in the carbon absorption process. After feeding acetylene for 500 s, carbon nanocoil buds have been grown out with catalyst particles on their tips. It is noted that the catalyst particles for carbon nanocoil growth have favorite sizes of 100 to 200 nm, while the particles with other sizes tend to induce the growth of carbon nanofibers.