Authors: M A Schettino J C C Freitas M K Morigaki E Nunes A G Cunha E C Passamani F G Emmerich
Publish Date: 2010/04/03
Volume: 12, Issue: 8, Pages: 3097-3103
Abstract
Magnetic carbonbased nanomaterials have promising applications in many fields owing to their biocompatibility and thermal/mechanical stability This study describes a hightemperature Xray diffraction XRD study of the chemical and structural transformations suffered by superparamagnetic iron oxide nanoparticles embedded in porous carbons The nanoparticles were prepared from the decomposition of iron pentacarbonyl over porous carbons resulting in nanometersized iron oxides homogeneously dispersed into the carbon matrix The thermally induced changes in these materials were followed by in situ hightemperature XRD using synchrotron radiation The growing of the nanoparticles and of the carbon crystallites were first observed followed by the reduction of the iron oxides to form αFe at temperatures as low as 400 °C in some cases and γFeC The temperatures at which these chemical reactions occurred were dependent on the total time spent on heating and on the nature of the iron oxides formed in the as prepared materials A noticeably large thermal expansion coefficient was also observed for the iron oxide nanocrystals The formation of austenitic iron stabilized by the presence of carbon was found to be only partially reversible upon cooling
Keywords: