Experimental investigation on the synthesis of carbon nanotubes (CNTs) by arc-discharge method using a MIG welder

Carbon nanotubes (CNT) are obtained by vaporizing graphite in an inert atmosphere using the arc-discharge method. Helium is found to be a favorable buffer gas for the synthesis of MWNTs compared to argon. Maximum yield of cathode deposit is obtained when the chamber pressure is maintained between 315--355 torr. Purification study of MWNTs showed that heating at 7500 C for 5 mins or 7000 C for 15 mins are desirable conditions for removing amorphous carbon. The vaporization of graphite with 4% Ni-1% Y in a helium atmosphere leads to the formation of SWNTs. The growth of SWNT bundles strongly depends on the chamber pressure. CNT bundles are formed in helium at a pressure in the range of 315--506 torr. Maximum yield was obtained when the helium pressure was 506 torr, at a flow rate of 2l/min. The nucleation and growth of SWNT bundles are explained according the vapor-liquid-solid (V-L-S) model.