Effects on field emission properties of carbon nanotubes by air oxidation

Multiwall carbon nanotubes (CNTs) were prepared by the catalytic decomposition of acetylene at 600°C using Ni as catalysts and the CNTs were treated by ball-milling for 0.5 -1 h. The treated CNTs were purified by removing most of amorphous carbon using air oxidation at the temperature of 300 -500°C. The morphologies and field emission properties of the oxidized CNTs were changed, mainly depending on the oxidation temperature. The field emission current density was increased , reached a maximum, and then decreased with increasing of the oxidation temperature. When the CNTs were oxidized at 400°C for 10 min, the field emission current density reached to 126. 5 μA/cm² at the applied field of 4. 41 V/μm. As a result, the most of amorphous carbon was removed and the purity of the CNTs was improved greatly. When the oxidized temperature is 400-450°C, the purified CNTs showed excellent field emission properties, such as high emission current density and uniform luminescence spots distribution.