Chiral absorbing materials, nano absorbing materials, ferrite absorbing materials, and their different applications in radar

1.Nano absorbing materialsMaterials with dimensions on the nanometer scale in a certain direction (between 0.1-100nm) are called nanomaterials, which are located in the transition region between atoms and macroscopic objects. Due to their unique structure, nanomaterials possess some special properties, such as quantum size effect, surface and interface effect, small size effect, macroscopic quantum tunneling effect, etc. The radar absorption performance of nano absorbing materials is excellent, so many research institutions abroad have focused on their research and application. It is reported that a research institution in the United States has developed a nano absorbing material called "super black powder", which has an absorption rate of up to 99% for radar waves and has been successfully applied on the B-2 stealth bomber. Currently, research is underway on nano composite materials covering centimeter wave, millimeter wave, infrared, visible light and other wavelengths. At present, the main research on nano absorbing materials includes nano metal and alloy absorbing materials, nano ferrite and its composite absorbing materials, nano ceramic absorbing materialsNano graphite absorbing materialNano silicon carbide absorbing materials, nano conductive polymer absorbing materials, etc.

2.Ferrite absorbing materialThe research on ferrite absorbing materials started earlier and their application time is relatively long. According to their different structures, they can be roughly divided into two types: spinel ferrite absorbing materials and hexagonal ferrite absorbing materials. Among them, spinel ferrite has lower cost, simpler preparation process, and the longest application history. However, spinel ferrite has lower magnetic permeability, and the relative dielectric constant and relative magnetic permeability are difficult to match, making it difficult to achieve good absorption performance. When developing the F-117A fighter jet, Lockheed Martin of the United States used a large amount of ferrite absorbing material on the surface of the fuselage to achieve good radar stealth effect. NEC Corporation has made improvements to ferrite absorbing materials, achieving a -10dB absorption effect in the 6-13GHz range, with a -20dB absorption effect in the 8.5-12.2GHz range. The total thickness is about 4.7mm, with a unit area mass of 8kg/m2. At present, the research and application level of ferrite absorbing materials by domestic research institutions is lower than that of foreign countries. In the frequency range of 8-18GHz (X, Ku band), the electromagnetic wave reflectivity can only reach the level of -10dB.

3.Chiral absorbing materialChiral materials refer to materials that do not have geometric symmetry and cannot be completely aligned with an object's mirror image through translation, rotation, and other means. As early as the 1980s, research on chiral absorbing materials gradually became a focus of attention. The ability to generate cross polarization under the action of electromagnetic fields is one of the important reasons why it can absorb electromagnetic waves and has good radar absorption performance.

Compared with other types of absorbing materials, it has two obvious advantages:

(1) It is easier to adjust the chiral parameter ratio of chiral materials and thus adjust the dielectric and magnetic permeability of the materials, which can achieve non reflective absorption effects over a wide frequency band;

(2) Chiral absorbing materials have lower frequency sensitivity than dielectric constant and magnetic permeability, making it easier to achieve wideband electromagnetic wave absorption. Therefore, chiral materials have great potential in expanding the absorption frequency band and low-frequency absorption.

Compared to other types of absorbing materials, chiral absorbing materials can enhance the absorption performance to a certain extent, broaden the existing absorption frequency band, and utilize the adjustability of chiral parameters of chiral materials to prepare high-performance radar absorbing materials. But at the same time, its preparation process is relatively complex and the preparation cost is high, which limits its application scope.

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