A solvothermal-reduction method for the production of horn shaped multi-wall carbon nanotubes

Horn shaped multi-wall carbon nanotubes (HMWCNTs) with uniform diameter of ∼100 nm, an average wall thickness of 10 nm and length of about 1 μm were prepared using a solvothermal-reduction method employing carbon tetrachloride as a carbon source and metallic copper as reductant. X-ray diffraction pattern indicated the presence of an amorphous carbon phase. Functional groups attached to the surface of the HMWCNTs were identified by diffuse reflectance infrared Fourier transform spectroscopy. The nitrogen sorption isotherm was of Type IIb with the hysteresis typically found for aggregated powders which possess non-rigid slit-shaped pores. The formation of HMWCNTs, as observed by scanning electron microscopy, proceeded through an intermediate fish-bone like morphology.