Metal micro powder/conductive polymer absorbing material

Carbonyl iron powder (CIP) is a traditionalMicrowave absorbing materialsDue to its high saturation magnetization and magnetic loss characteristics, CIP has been widely used in the field of electromagnetic absorption. However, its high density severely limits its application [73]. By modifying carbonyl iron and combining it with conductive polymers to improve the impedance matching of the material, the material exhibits both dielectric and magnetic losses, thereby enhancing its microwave absorption capacity.

A novel self-assembly polymerization method was synthesized using dopamine as a mediatorThree dimensional carbonyl iron/polypyrrole aerogel compositesThe preparation process is shown in Figure 11 [74].
The vector network analyzer is used to test the electromagnetic properties of the material. When the content of polypyrrole aerogel is 33%, the thickness is 2.2mm, and the frequency is 12.2 GHz and 14.2 GHz, the peak value of the minimum reflection loss is -38.9 dB and -39.5 dB respectively, and the effective absorption bandwidth can reach 6.1 GHz. Interface polarization and geometric effect are the key to improving the wave absorption ability of this material. The carbonyl iron is in sheet shape, and the polypyrrole spherical aerogel grows along the edge of the carbonyl iron to form a 3D network structure while fixing the carbonyl iron. Under the effect of electric field, the free charge in the medium moves, and is captured by the interface between the carbonyl iron sheet particle structure and the particles, forming a local aggregation of space charges, which makes the distribution of free charges in the medium uneven, thus producing a macroscopic dipole moment phenomenon, which attenuates the electromagnetic wave energy, and the synergy and complementary effects between the two particles also play a certain role.

Advanced Institute Technology has prepared a new type of material through simple blending technologyLightweight microwave absorbing nanocompositesThe composite material is composed of hollow microspheres of carbonyl iron modified with carbon nanotubes and polyaniline. The weight ratio of hollow carbonyl iron modified with multi walled carbon nanotubes to polyaniline is 2:1. The dielectric constant, magnetic permeability, and microwave absorption capacity of the material were studied in the frequency range of 8.5-12.5 GHz. When the material thickness is 2mm and the frequency is 11 GHz, the minimum reflection loss is -25.5 dB, and the effective absorption bandwidth is 3.6 GHz. Hollow carbonyl iron was prepared by pitting method. Effective pitting can effectively eliminate the skin effect of the material, and the corrosion of the inner surface of the sphere can achieve multiple reflections of electromagnetic waves, improving microwave attenuation ability. Composite with polyaniline and multi walled carbon nanotubes improved the impedance matching of the material, resulting in both dielectric and magnetic losses.

The electromagnetic wave absorption ability of poly (pyrrole)/silicone rubber filled nano carbon and carbonyl iron nanocomposites in the X-band was studied. Poly (pyrrole) and silicone rubber were mixed in a ratio of 10:90 to obtain a PP-SR matrix, and nano carbon and carbonyl iron were loaded on the matrix to test its absorption ability. When the material thickness was 1mm and the frequency was 10.27 GHz, the minimum reflection loss was -13 dB; As a matrix, PP-SR not only enhances the absorbing ability of the material, but also improves its flexibility, mechanical properties, and hydrophobicity. Nano carbon is dispersed in the PP-SR matrix, and charges accumulate at the interface boundary between nano carbon and rubber. These aggregates form a conductive network inside the material, resulting in a monotonic increase in the real part of the dielectric constant. Carbonyl iron, as a magnetic filler in the matrix, can effectively counteract the magnetic component of electromagnetic waves.