X-ray diffraction, Mössbauer spectroscopy, Scanning Electron Microscopy
(SEM) and Transmission Electron Microscopy (TEM) techniques were used to
characterize the Fe-C phases in the soots synthesized by the DC arc
discharge method. Various equilibrium and non-equilibrium Fe-C compounds
were identified, with fractions depending on both the location in the
reactor and the helium gas pressure. The soots obtained are composed of the
same five phases (C-graphite, α-Fe, γ-Fe, Fe3C and
Fe5C2) whatever the helium gas pressure and wherever they are
situated in the reactor. However, the location in the reactor has a
considerable influence on the size of the particles in the nanostructure.
The Fe-C compounds in the Pyrex vessel samples (CL) seem only to be present
in the form of nanoparticles embedded in an amorphous gangue, while the
water-cooled copper cylinder samples (RS) contain, in addition to these
nanoparticles, large composite crystalline particles.