Nanographite structures formed during annealing of disordered carbon containing finely-dispersed carbon nanocapsules with iron carbide cores

Disordered carbon containing finely-dispersed carbon nanocapsules with iron carbide cores were synthesized by a modified method in which low-current plasma discharge was generated in liquid ethanol with ultrasonic irradiation. The structure of nanographite forms prepared by the annealing at 900 °C for 2 h of disordered carbon containing finely-dispersed carbon nanocapsules was studied. Transmission electron microscopy (TEM) studies of the powder sample after annealing revealed most part of disordered carbon was transformed into nanographite ribbons, hollow polyhedral graphitic cages and thick carbon shells with the turbostratic structure of carbon layers. TEM observations of the carbon layers revealed stacking defects. Selected-area diffraction and fast Fourier transforms of digitized images revealed that carbon inter-layer spacings vary from 3.4 to 3.5 Å. XRD analysis showed that annealing of the powder sample at 900 °C for 2 h resulted in the decompositions of iron carbide cores and a well-defined broad carbon peak (0 0 2) centered at 2θ ≈ 25.9° (d₀₀₂ = 3.44 Å) was detected. The growth of the I_D/I_G ratio and shift of the D peak to a lower wavenumber may indicate increase in size the graphite clusters and ordering carbon structure, i.e. appearance of nanographite structures.