Fe3C nanopowder prepared by laser-induced pyrolysis

The Fe3C-based nanocrystalline composite was prepared by the laser pyrolysis method, using a cross-flow reactor in which the laser orthogonally irradiates the gas mixture of Fe(CO)5 and C2H4. Vapours of iron pentacarbonyl served as a source of Fe atoms. Ethylene absorbed CO2 laser radiation but was also a source of C atoms (after its decomposition on hot surfaces of freshly formed Fe particles). The synthesized nanopowder was in-situ passivated with air. The as-synthesized powder was characterized by HRTEM, XRD, Moessbauer spectroscopy, and low temperature magnetic measurements. The nanopowder consisted of aggregated nanoparticles (around 20 nm large) having carbonaceous shells. In our contribution we present the results of the above mentioned characterization techniques. We concentrate especially on the interpretation of the Moessbauer spectra measured at high temperatures (up to 300 grad C) and low temperatures (down to 4 K). (authors)