Magnetite (Fe₃O₄)-filled carbon nanofibers as electro-conducting/superparamagnetic nanohybrids and their multifunctional polymer composites

A mild-temperature, nonchemical technique is used to produce a nanohybrid multifunctional (electro-conducting and magnetic) powder material by intercalating iron oxide nanoparticles in large aspect ratio, open-ended, hollow-core carbon nanofibers (CNFs). Single-crystal, superparamagnetic Fe₃O₄ nanoparticles (10 nm average diameter) filled the CNF internal cavity (diameter <100 nm) after successive steps starting with dispersion of CNFs and magnetite nanoparticles in aqueous or organic solvents, sequencing or combining sonication-assisted capillary imbibition and concentration-driven diffusion, and finally drying at mild temperatures. The influence of several process parameters—such as sonication type and duration, concentration of solids dispersed in solvent, CNF-to-nanoparticle mass ratio, and drying temperature—on intercalation efficiency (evaluated in terms of particle packing in the CNF cavity) was studied using electron microscopy. The magnetic CNF powder was used as a low-concentration filler in poly(methyl methacrylate) to demonstrate thin free-standing polymer films with simultaneous magnetic and electro-conducting properties. Such films could be implemented in sensors, optoelectromagnetic devices, or electromagnetic interference shields