YIELD OF FULLERENES GENERATED BY CONTACT ARC METHOD UNDER HE AND AR - DEPENDENCE ON GAS-PRESSURE

The yields of toluene-soluble material from carbon soot depend on the buffer ps as well as the pressure. Helium was more effective for yielding fullerenes than argon, and the optimum pressure was 20 Torr, under which a maximum yield of about 13 wt% was obtained. C60 showed a maximum abundance at 20 Torr, while C70 and higher fullerenes (C76, C78 and C84) at a slightly higher pressure between 20 and 50 Torr. Raw soot was also studied by electron microscopy. The pressure dependence of the fullerene yield is discussed in terms of the cooling rate and diffusion of carbon vapor around the evaporation source.