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Effect of temperature, pressure, and gas ratio of methane to hydrogen on the synthesis of double-walled carbon nanotubes by chemical vapour deposition

Double-walled carbon nanotubes (DWCNTs) were synthesized by chemical vapour deposition using Fe–Mo catalyst supported on magnesium oxide particles. A mixture of gases of methane and hydrogen was used for the growth. The effect of gas pressure, ratio of methane to hydrogen, and growth temperature on the structure, purity, and yield of DWCNTs has been studied in detail. Transmission electron microscope studies revealed that the growth temperature is the crucial factor determining the size of the catalyst particles. Scanning electron microscope studies were also carried out to provide information on the purity and diameter of DWCNTs synthesized under various conditions.