Magnetic resonance study of PTMO - block - PET copolymer filled with a mixture of Fe3O4 and Fe3C nanoparticles at low concentration
|Tomasz Bodziony 1, Nikos Guskos 2, Janusz Typek 1, Zbigniew Roslaniec 3, Urszula Narkiewicz 4, Michał Maryniak 1|
1. Technical University of Szczecin, Institute of Physics (TUS), al. Piastów 48, Szczecin 70-311, Poland
Nanocrystalline iron samples were carburised with CO/CO2 mixture at 400 - 550C. The product obtained contained 29% Fe3C, 35% Fe3O4 and 36% C as carbon fibres. The sample were characterised by XRD, TOC (total carbon, Multi N/C) and SEM after carburisation. This iron-carbon composite was used as a filler for PTMO - block - PET polymer, with low concentration (0.5%) of iron-carbon composite. Electron Spin Resonance investigations of the sample were carried out in the 4-300 K temperature range. At room temperature a strong symmetrical signal with g = 2.229 +- 0.022 and linewidth of 150 mT dominates the spectrum. With the temperature decrease the intensity of the line is decreasing, but at temperature of about 90 K another line appears with g = 2.666 +- 0.032. This low-temperature line is very anisotropic and its low-field shoulder spreads to negative magnetic fields. With decreasing temperature, the linewidth of this line decreases slightly, in contrast to the behavior of the high-temperature line. The intensity of the low-temperature line is approximately independent on temperature, while the intensity of the high-temperature line strongly depends on temperature. The difference in behavior of these two lines suggests that they originate from different magnetic centers. Based on detailed analysis we suggest that the line visible at higher temperatures arises form Fe3O4 (magnetite) nanoparticles, whereas the line visible below 90 K arises from Fe3C (cementite) nanoparticles. The disappearance of the line from magnetite may be caused by the so-called blocking effect, i.e. the interaction between paramagnetic Fe3O4 nanoparticles and the polymer matrix.
Presentation: poster at E-MRS Fall Meeting 2004, Symposium I, by Tomasz Bodziony
See On-line Journal of E-MRS Fall Meeting 2004
Submitted: 2004-04-28 16:02 Revised: 2009-06-08 12:55