Papers by Author: J. Typek

Abstract: Two different concentrations of nanocrystalline material: α-Fe/C were prepared by the carburization of nanocrystalline iron and characterized by XRD and SEM. The nanoparticles were next used as fillers in polymer nanocomposites using the in situ polycondensation reaction in a poly(ether-ester) matrix with two concentrations: 0.1 wt. % and 0.3 wt. %. The temperature dependence of the ferromagnetic resonance (FMR) spectra was investigated to study magnetic interactions in the compounds. The introduced FMR parameters (intensity and position of the right peak) describe well the temperature dependence of FMR spectra of strongly interacting magnetic nanoparticles. The FMR spectra depend strongly on the concentration of magnetic nanoparticles, which influence the magnetic interactions between them. Two main critical points of the matrix (the glass state and the freezing of benzene rings) influence the behaviour of the FMR spectra.

Abstract: As a result of the Schiff base condensation the gadolinium macroacyclic and macrobicyclic Schiff base complexes have been synthesized and investigated by infrared spectroscopy (IR) and electron paramagnetic resonance (EPR). Both electron ionization and electron spray Molecular Spectroscopy spectra confirmed the [1:1] proportion of a ligand to metal in gadolinium macrocyclic and mocrobicyclic Schiff base complex samples. The thermogravimetrydifferential thermal analysis (TG-DTA) indicated the presence of two water molecules in the innersphere of the macrobicyclic complex and confirmed no water coordination of the metal ion in the macroacyclic complex. The temperature dependence of the integrated intensity of the EPR spectra enabled the magnetic interactions in the spin system of these compounds to be revealed.

Abstract: Agglomerated cobalt magnetic nanoparticles coated with carbon, dispersed in a paraffin matrix, were prepared and investigated by FMR (ferromagnetic resonance) at room temperature. Four samples with different C/Co content, ranging from 0.175 to 1.011, dispersed at low concentration in paraffin were investigated. Very intense and broad FMR spectra with different intensities, line widths and positions of the resonance fields were recorded for the samples. A strong dependence of the FMR signal intensity and resonance on the concentration of magnetic nanoparticles was observed. Various magnetic interactions affecting the observed FMR spectra have been analyzed. It was found that with increasing concentrations of magnetic nanoparticles the magnetic dipole interaction between the agglomerates plays a more important role.