Carbonyl iron powder, an old traditional absorbent

Release time:

2023-06-13 17:26

Because of its good temperature stability, high permeability and low production cost, carbonyl iron powder has a wide range of application prospects in absorbing materials. It is the most in-depth research, the most widely used, and excellent absorbing performance of electromagnetic wave absorbers at home and abroad, and widely used in active weapons and equipment. For example, the F / A-18C / D Bumblebee aircraft in the United States, in order to reduce its RCS, uses carbonyl iron powder as the main radar absorbing material on the fuselage surface and wings. The F-15SE "silent Eagle" is the final improvement of the F-15 heavy fighter. In order to ensure its air superiority in the face of the third generation and the third generation of semi fighter, its stealth performance is improved A large number of radar absorbing materials, mainly carbonyl iron powder, are used in many parts of the joint, wing and fuselage, which reduces the radar reflection cross-sectional area of the front to the level of F-35.            Carbonyl iron powder is the iron powder obtained from the direct decomposition of carbonyl iron. When Fe (CO) is heated 5 times to 70 ~ 80 ℃, it begins to decompose into Fe and Co. at 155 ℃, it decomposes in large quantities, and finally forms the onion like carbonyl iron powder. The main carbonyl iron powder is iron. The common carbonyl iron powder has two kinds of morphologies: spherical and flaky. Figure 1 shows the photos of carbonyl iron powder particles under scanning electron microscope. The high-frequency magnetic properties of spherical carbonyl iron powder are limited by the Snoek limit, so it is difficult to meet the requirements of "thin, light, wide and strong" microwave absorbing properties. However, the flake carbonyl iron powder can break through the limit to obtain excellent high-frequency electromagnetic properties.

For materials with good absorbing properties, one is to lose the incident radar wave as much as possible inside the absorbing material; the other is to match the impedance of the radar absorbing material with that of the incident radar wave, so as to achieve the condition of no reflection. In order to achieve the first condition, the permittivity and permeability are important parameters that affect the interaction between electromagnetic wave and medium. Where dielectric constant: ε = ε '- I ε ". The permeability is μ = μ '- I μ ", ε" and μ "represent dielectric loss and magnetic loss respectively. For the medium material, it has the ability of electromagnetic wave dissipation and absorption. To achieve the second condition, in free space, when the impedance is Z0, the radar wave can project to the dielectric layer surface with the impedance of Z0, and the reflection coefficient r = (1 – Z / Z0) / (1 + Z / Z0).            In essence, the study of absorbing materials is the study of their electromagnetic parameters, which depend on their composition, structure and appearance. Therefore, by exploring the relationship between the structure and appearance of the material and the electromagnetic parameters, the structural characteristics of the material can be adjusted, so as to obtain excellent microwave absorption properties. Therefore, it is the key to realize the free regulation of microwave electromagnetic parameters of absorbers. Carbonyl iron powder is one of the most important research objects in the field of absorbers because of its high saturation magnetization and low price.


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