Rapid Millifluidic Synthesis of Stable High Magnetic Moment Fe_xC_y Nanoparticles for Hyperthermia

A millifluidic reactor with a 0.76 mm internal diameter was utilized for the synthesis of monodisperse, high magnetic moment, iron carbide (Fe_xC_y) nanoparticles by thermal decomposition of iron pentacarbonyl (Fe(CO)₅) in 1-octadecene in the presence of oleylamine at 22 min nominal residence time. The effect of reaction conditions (temperature and pressure) on the size, morphology, crystal structure, and magnetic properties of the nanoparticles was investigated. The system developed facilitated the thermal decomposition of precursor at reaction conditions (up to 265 °C and 4 bar) that cannot be easily achieved in conventional batch reactors. The degree of carbidization was enhanced by operating at elevated temperature and pressure. The nanoparticles synthesized in the flow reactor had size 9-18 nm and demonstrated high saturation magnetization (up to 164 emu/g_Fe). They further showed good stability against oxidation after 2 months of exposure in air, retaining good saturation magnetization values with a change of no more than 10% of the initial value. The heating ability of the nanoparticles in an alternating magnetic field was comparable with other ferrites reported in the literature, having intrinsic loss power values up to 1.52 nHm² kg^-1.