Abstract
The synthesis of tapered carbon nanotubes (TCNTs) by the thermal decomposition of poly(ethylene glycol) at 800°C using Ni as a catalyst is reported. The TCNTs consist of a 50nm diameter graphite tube terminated by a tapered tip, which is about 1μm in length and 20nm in diameter in the tip end. The catalyst particle contained in the tapered tip was found to be a cylindrical with a diameter of about 20nm. Electron microscopy revealed that the catalyst was a single crystal of NiCx and the graphene layers were grown in the [110] direction of the catalyst, forming TCNTs. The unique morphology of the catalyst particle played an important role in the formation of TCNTs. The field emission properties of the TCNTs exhibited a lower turn-on voltage (Eturn-on=3.2V/μm), lower threshold fields voltage (Ethreshold=5.2V/μm) and higher field-enhancement factor β than did multi-walled CNTs.
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