Synthesis of nitrogen-doped horn-shaped carbon nanotubes by reduction of pentachloropyridine with metallic sodium

Nitrogen-doped horn-shaped carbon nanotubes (CNTs) have successfully been prepared by reducing pentachloropyridine with metallic sodium at 350 degrees C. A typical CNT has an open-end diameter of similar to 2 pm, a close-end diameter of similar to 0.3 pin, a wall thickness of similar to 30 nm, and a length up to 8 pin. TEM observation indicates that the CNTs account for similar to 30% of the products, and the rest is solid and hollow carbon nanospheres (CNSs) with a diameter of about 50-290 nm. Elemental analysis shows that the N/C atomic ratio of the carbon nanostructures is about 0.0208. XRD and HRTEM measurements reveal that the CNTs are amorphous. To understand the growth process and refine the growth condition, various control experiments have been finished. At last, a sodium-catalysis-reduction solid-liquid-solid growth mechanism of the CNTs has been suggested on the basis of the experiments. (c) 2007 Elsevier Ltd. All rights reserved.