Controlled synthesis of core–shell iron–silica nanoparticles and their magneto-dielectricproperties in polymer composites

Abstract

Low loss core–shell iron–silica nanocomposites with improved magneto-dielectric propertiesat radio frequencies (1 MHz–1 GHz) were successfully fabricated. A new simplemethod was developed to synthesize metallic iron (Fe) nanoparticles with uniformsize distribution in an aqueous environment at room temperature. Citric acidand oleic acid served as surface-capping agents to control the particle size of thesynthesized Fe nanoparticles. Smaller Fe nanoparticles with narrower particle sizedistribution were obtained as the concentration ratio of iron ions to carboxylic acidgroups decreased. The Fe nanoparticles were subsequently coated with silica (SiO2)layers to prevent the iron cores oxidizing. Polymer composites were prepared by incorporatingFe@SiO2 nanoparticles with polydimethylsiloxane (PDMS) elastomers.Experimental results showed that the dielectric permittivity(ε) and magneticpermeability (μ) of the polymer composite increased with increasing amount ofFe@SiO2 nanoparticle doping.The dielectric loss (tanδ) was near 0.020 at a frequency of 1 GHz.