Patent ID: 6916434

Claim:
A process for preparing a carbonaceous material comprising iron-carbon composites composed of (a) nested multi-walled carbon nanotubes and (b) iron carbide or iron, wherein 10 to 90% of the internal spaces of the nested multi-walled carbon nanotubes are filled with the iron carbide or iron, said process comprising the steps of: (1) heating an iron halide to a temperature of 600 to 900° C. in a reaction furnace in which the pressure has been adjusted to 10 −5 Pa to 200 kPa in an inert gas atmosphere and the oxygen concentration in the reaction furnace has been adjusted such that the ratio B/A is 1×10 −10 to 1×10 −1 , wherein A is the reaction furnace volume (liters) and B is the oxygen quantity (Ncc); (2) introducing an inert gas to the reaction furnace, and at a pressure of between 10 −5 Pa and 200 kPa, introducing a pyrolyzable carbon source and performing a heat treatment at 600 to 900° C.; (3) replacing the atmosphere inside the reaction furnace with an inert gas while the temperature in step (2) is maintained; (4) elevating the temperature in the reaction furnace, the atmosphere of which has been replaced with the inert gas, to 950 to 1500° C.; (5) maintaining the final temperature at the end of the temperature elevation until nested multi-walled carbon nanotubes are produced; and (6) cooling the temperature in the reaction furnace at a rate of 50° C./h or lower, to thereby produce a carbonaceous material comprising iron-carbon composites composed of nested multi-walled carbon nanotubes and iron carbide or iron that fills 10 to 90% of the spaces inside the tubes.