Microwave absorption and EMI shielding properties of NiZn ferrites/MWCNT/wax

Ferrite/carbon nanotubes composites are widely used in the fields of electromagnetic wave absorption and electromagnetic shielding. In present work, NiZn ferrite composites with different carbon nanotube contents (0 mg, 25 mg, 50 mg) were prepared by the hydrothermal method. TEM and XRD confirmed the formation of ferrite and the presence of carbon nanotubes. The content of carbon nanotubes and the weight fraction of the composite in paraffin wax have a significant impact on the electromagnetic parameters. Adjusting these two quantities can make the matching thickness of the sample equal to both 1/4 wavelength and meet the impedance matching, thus achieving relatively good absorption. In this work, for the material with 25 mg of carbon nanotubes and a mass fraction of 50%, the minimum reflection loss reached -67.5 dB at 10.8 GHz and a wide EAB of 4.3 GHz (ranging from 13.0 to 17.3 GHz). For the material with 50 mg of carbon nanotubes and a mass fraction of 40%, the minimum reflection loss reached -54.4 dB at 5.6 GHz and an EAB value of 1.8 GHz. In addition, the higher the carbon nanotube content and the larger the mass fraction of the material, the higher the shielding effectiveness.