Magnetic behaviour of the Fe-C nanopowders prepared by laser synthesis from ethylene / iron pentacarbonyl gas phase mixture

0177665 - UFM-A 20013169 RIV SIGLE IE eng C - Conference Paper (international conference)
David, Bohumil - Vondráček, Martin - Schneeweiss, Oldřich - Morjan, I. - Alexandrescu, R.
Magnetic behaviour of the Fe-C nanopowders prepared by laser synthesis from ethylene / iron pentacarbonyl gas phase mixture.
COST-ACTION 523 Mid term Meeting and Workshop On Nanomaterials: Fundamentals and Applications - Abstracts. Limerick: Department of Physics, University of Limerick, 2001, s. 55.
[COST-ACTION 523 Mid term Meeting and Workshop On Nanomaterials: Fundamentals and Applications. Limerick (IE), 04.10.2001-06.10.2001]
R&D Projects: GA AV ČR KSK1010104; GA MŠMT OC 523.20
Institutional research plan: CEZ:AV0Z2041904
Keywords : nanopowder * laser synthesis * Mössbauer spectroscopy
Subject RIV: BM - Solid Matter Physics ; Magnetism

Nanopowders of the Fe-C based material were prepared by laser irradiation of the Fe(CO)5 vapors mixed with C2H4 as a carrier gas. The as prepared powder was characterized by TEM, XRD and IR. Magnetic behaviour was investigated using Mössbauer spectroscopy and magnetic measurements. In the sample of the as prepared state there were identified bcc alpha-Fe, Fe3C and iron oxide phases in agreement of all methods applied. Comparison of Mössbauer spectra taken at 300K and at 20K shows that prevailing amount of oxide particles exhibits superparamagnetic behaviour. The hysteresis loop corresponds well to an assembly of nanoparticles. In the thermomagnetic curve (measured in vacuum at increasing temperature up to 800°C) critical temperatures of the phases alpha-Fe, Fe3C and gamma-Fe2O3 can be identified. The part of the curve corresponding to decreasing temperature and subsequent measurement of the Mössbauer spectra witnesses that changes in the phase composition of the sample occurred. During the heatingat measurement of the thermomagnetic curve the Fe3C decomposed and important amount of wustite (FeO) was formed. The hysteresis loop indicates particle (grain) coarsening.
Permanent Link: http://hdl.handle.net/11104/0074584