Microwave absorption by dextrin-magnetite nanocomposite in frequencies below 2.5 GHz: Role of magnetite content, shape and temperature on magneto-dielectric properties

The influence of temperature, magnetite shape, and content on the electromagnetic interference shielding properties was determined for dextrin based composites. The absorption properties increase linearly with increasing temperature. The usage of dextrin results in the widening of the absorption frequency region in comparison to the pure magnetite nanoparticles. The composite containing 50 wt% of spherical Fe₃O₄ NPs has RL < −10 dB in the frequency range from 1.59 to 2.36 GHz, whereas magnetite nanoparticles have RL < −10 dB in the narrow frequency range i.e. 1.2–1.74 GHz. The cuboidal nanoparticles have much lower reflection losses, which is associated with the decrease of defects number. The minimum reflection loss for composite with spherical particles is equal to −25 dB for a 12 mm layer, whereas for cuboidal particles aged in NaHCO₃ is equal to –22.5 dB for 20 mm thickness. The lowest one was achieved for cuboidal nanoparticles aged in KOH and was equal to –18.7 dB for 16 mm absorber thickness.