Dominant Formation of Carbon Nano or Microcoils By the Manipulation of SF₆ Injection Flow

Carbon nano or microcoils were synthesized using C2H2 flow as a source gas along with an injection of SF6 flow as an incorporated additive gas under the thermal chemical vapour deposition (TCVD) system. These syntheses were carried in the reaction temperature range of 550―850°C. According to the different reaction temperature the ratio of SF6/C2H2 injection gases flows and the injection time of SF6 flow were varied respectively. At the lowest reaction temperature (550°C) in this work, the carbon microcoils could be formed within a relatively short initial injection time (less than 15min) of SF6 flow. With increasing the injection time of SF6 flow, the carbon nanocoils could be well-developed on the surface of the sample. At 750°C, the formation of the carbon microcoils was dominated on the whole surface of the sample, irrespective of the ratio of SF6/C2H2 injection gases flows and the injection time of SF6 flow. At the highest reaction temperature (850°C) in this work, any coil-like morphology could not be observed on the surface of the sample. Based on these results the optimal condition for the formation of the carbon nano or microcoils in the viewpoints of the reaction temperature, the ratio of SF6/C2H2 injection gases flows, and the injection time of SF6 flow were suggested. Furthermore, the cause for the formation of carbon nano or microcoils within a limited reaction condition was discussed.