Carbon nanocoils (CNCs) were synthesized by the catalytic pyrolysis of acetylene over a mixture of Fe and SnO2 particles in a chemical vapor deposition (CVD) apparatus. The effects of reaction temperature, the composition of Fe and SnO2 in the catalyst, and the ratio of acetylene (C2H2) to helium (He) gas were examined. An optimum output was obtained when the Fe/SnO2 ratio was 2/1, the flow rates of C2H2 and He gases were 150 and 700 sccm, respectively, and the reaction temperature was 700°C. Under these conditions, the CNCs were of 80% purity, with average coil diameters of 750 nm, fiber diameters of 300 nm and pitches of approximately 750 nm. The CNC yield weighed up to 60 times that of the catalyst in 10 min.

In the present study, an automatic production system with sequencer control for the synthesis of carbon nanofibriform based on catalytic CVD using a substrate was developed. The carbon nanotwist (CNTw), which is one of the helical carbon nanofibers, was then synthesized in powdery form with an Ni-SnO 2 -composed catalyst. The production rate was 5 400 times that of the conventional CVD system and Ni-Cu-In 2 O 3 catalyst. The powdery CNTw was easily scraped off the substrate, then pasted with organic binder, and printed by a squeegee method on ITO glass substrate for an electron field emitter. The field emission performance was found to be better than that of the directly grown CNTw film in conventional CVD with Ni-Cu catalyst.

Abstract. Twisted carbon nanofibers, named carbon nanotwists (CNTws), in a flocculated form were pasted, printed on the conductive silicon substrate, and then treated by dielectric barrier discharge using He and N 2 gases. Vertically upright nanofibers were clearly obtained by "filament discharge mode" in N 2 gas. As the treating time increased up to ~60 s, the height of the nanofiber tips became uniform. Consequently, the field emission property was greatly enhanced and showed a threshold electric field of 4.6 V/µm and maximum current of 0.433 mA/cm 2 at 8 V/µm.

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