文摘
Magnetic and structural characteristics were investigated for the nanoparticles of Fe5Si3 grown by a carbon-mediated, kinetically controlled pyrolysis of a thermosetted ferrocenylsiloxane polymeric network. Kinetics of the pyrolysis determined the volume fraction of the crystallographic phase of Fe5Si3 or bcc-Fe that was formed. Nanoparticles of Fe5Si3 were formed during pyrolysis of the network to 1000 °C at 10 °C/min, and silicon-doped bcc-Fe nanoparticles resulted when the network was ramped to 1000 °C at a slower rate of 1 °C/min. Transmission electron microscopy and X-ray diffraction studies revealed that Fe5Si3 nanoparticles were contained in carbon nanocapsules, and the bcc-Fe nanoparticles were associated with linear carbon fibers, an outcome of the distinct interfacial energies of the Fe−Si growth phase and carbon surface at the two pyrolysis rates. Fe5Si3 nanoparticles were found to be ferromagnetic with a Curie temperature of 375 K by magnetic measurements.