Peculiarities of carbon spheres obtained by hydrocarbon pyrolysis in hermetically closed container

Abstract

Perfect in shape, pure carbon spheres were obtained on a large scale from xylene, benzene, toluene and naphthalene by means of pyrolysis in a closed iron container at temperatures in the range 500–800°C and a pressure of 20MPa. A part of the experiment was carried out in the presence of water vapor. Synthesis in closed space stimulated particle growth and due to which the sphere diameters were from 1 to 12μm. Some of the spheres were docked one to another in the course of growth and built a chain like a necklace of pearls.The obtained material was investigated by TEM, SEM, EDS and XRD. The results showed that carbon atoms in the spheres were arranged in concentric incompletely closed graphitic shells, which made them stable in air up to 600°C. Oxygen reacted with carbon atoms situated at the shell edges during heating in air and a part of them remained as spheres. Oxygen penetration was temperature dependent and oxygen concentration increased with temperature treatment. Hence, the spheres accumulated up to 20at% oxygen at 600°C in half an hour.