The radar absorption properties of the hollow Fe3O4 microspheres synthesized by the plasma dynamic method

Abstract

This work presents the investigations of the radar absorbing properties of the hollow magnetite microspheres. They were produced in one short-time process of the plasma dynamic synthesis. The obtained particles was separated into fractions with sizes from 3 μm to 30 μm (fraction 1), from 30 μm to ∼ 100 μm (fraction 2) and the fraction with size greater than 100 μm (fraction 3). In order to investigate the microwave characteristics of materials, the selected fractions of the hollow microspheres were placed in an epoxy compound. The weight content of the filler in the compound was equal to ≈ 50%. The electromagnetic response of the samples was studied in the coaxial waveguide on the toroidal samples with thickness t = 2.2 mm. It was found that particles with sizes ≤ 30 μm provide the greatest signal attenuation up to −40 dB at the frequency ∼ 10.5 GHz. There is also a shift of the absorption maxima in the region of low frequencies with increase in the size of hollow spheres. The samples provide a reflection coefficient smaller than −10 dB in following frequency ranges: 8.8 + 16.2 GHz (No. 1), 7.4 + 11.3 GHz (No. 2) and 3.7 + 5.0GHz (No. 3). Thus, fraction 1 has a band of operating frequencies at the −10dB level of almost an octave. The sample on the base of initial synthesized powder allows attenuating the EM signal (below −10 dB) in the frequency range from 3.7 to 15.6 GHz, due to the presence of particles with a broad size distribution.