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Multiwalled carbon nanotubes (MWCNTs) with uniform diameters (10−20 nm) and high densities per unit area were synthesized in a 5−10 s combustion process using a mixture of butane and air at 880 °C. The growth mechanism of MWCNTs was studied via time-sequence experiments to reveal that the catalyst nanoparticles were formed on a 3 nm thick Ni-coated wafer after 3 s in the flame. Short and uniform MWCNTs were synthesized using a 5 s process, whereas MWCNTs with a maximum density and length were obtained using a 10 s process. It is believed that both the synthesis temperature and the combustion products, such as CO, H2O, C n H m (n = 1 or 2), and polycyclic aromatic hydrocarbons, play an important role in the growth of the MWCNTs. Furthermore, the field emission properties of the combustion-generated carbon nanotube (CNT) films were studied, and an emission current density of 0.18 mA/cm2 at 7 V/μm was obtained. These results suggested that this fabrication method provided rapid and direct growth of field-emission CNTs on a desired substrate.

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