The application of stealth and anti stealth absorbing materials in the low-frequency S-band (1.5-3.5GHz) of radar waves is receiving increasing attention

Radar absorbing materialsIt has a wide range of applications in civilian communication and military stealth fields. The stealth and anti stealth applications of radar waves in the low-frequency S-band (1.5-3.5GHz) are receiving increasing attention, and civilian 3G and 4G communication also fall into this frequency band. Its application technology is still a bottleneck. Therefore, Advanced Institute of Technology believes that it is necessary and urgent to study absorbing materials with good absorption characteristics in the low-frequency S-band of radar waves.

Carbonyl iron has good temperature stability and high radar wave permeability, and its industrial technology is mature, making it one of the most researched absorbing materials. However, its low-frequency radar wave absorption performance still needs to be improved.

Preparation of radar low-frequency carbonyl iron/SiO2 and carbonyl iron/MnZn by coating and adding non-magnetic and magnetic insulation materialsFerrite composite absorbing materialBy adjusting its electromagnetic parameters, the absorption performance of the composite material can be improved through SEM XRD、 Characterization methods such as vector network analyzer are used to analyze the microstructure, phase structure, microwave electromagnetic parameters and other characteristics of the obtained samples. The absorption performance of the samples in the low-frequency S-band of radar waves is studied. Finally, the low-frequency S-band reflection loss (RL) is analyzed through the theory of transmission lines.

High performance SiO2/flaky carbonyl iron composite microwave absorbing materials were prepared by the sol gel methodCarbonyl iron absorbing materialThen, SiO2/sheet-like carbonyl iron composite materials were obtained by adding different contents of precursor ethyl orthosilicate (silicon 28). The research results indicate that the composite powders of SiO2/carbonyl iron samples obtained with different contents all exhibit a flat and loose structure, and the thickness of the sheet-like powder increases with the increase of silicon content;

However, XRD showed that the composite material still had a body centered Fe phase structure, and the intensity of the sample diffraction peak decreased with the increase of silicon 28 content; The electromagnetic parameters of composite materials change significantly with the increase of silicon 28 content. The shift of the reflection loss peak of absorbing materials towards lower frequencies is closely related to the increase in dielectric loss values, which is beneficial for improving the low-frequency absorption characteristics of composite materials. The maximum reflection loss peaks of precursors with different contents all appear at low frequencies, demonstrating good low-frequency absorption performance. When the coating thickness is 1mm and the silicon content is 6ml, the loss peak frequency of SiO2/carbonyl iron composite particles is the lowest, and its RL reaches -7.5dB at 4GHz.
　　

Carbonyl iron/SiO2 composite materials were prepared by ball milling method, with SiO2 added to carbonyl iron raw materials at mass fractions of 1%, 2%, 3%, and 4%, respectively, and ball milled for 30 hours. The results showed that SiO2 and carbonyl iron powder formed porous composite particles with flat morphology after high-energy ball milling. With the increase of SiO2 mass fraction, the agglomeration of carbonyl iron after coating was improved, and the high dispersibility of particles improved the dispersion characteristics of carbonyl iron, thereby reducing the dielectric constant of the composite material. XRD shows that the phase of the sample is still Fe phase, with a corresponding increase in dielectric constant and a decrease in magnetic permeability. When the thickness is 2.5mm, the reflection loss peaks of SiO2/carbonyl iron composite particles with different mass fractions appear between 1.5-3.5GHz, and as the SiO2 mass fraction increases, the absorption loss peak of the composite particles shifts towards higher frequencies, and the minimum absorption loss peak decreases accordingly. When the mass fraction of SiO2 added is 4%, the sample has the best reflection loss, and its reflection loss reaches -22.32dB at 3.72GHz.

Finally, carbonyl iron and MnZn ferrite composite low-frequency absorbing materials were prepared using ball milling technology, and MnZn doped with different mass fractions (2%, 4%, 6%, 8%) was studiedFerrite composite absorbing materialThe variation law of low-frequency electromagnetic parameters. Compared to carbonyl iron, MnZn ferrite has a lower dielectric constant (insulator) and lower magnetic permeability. The composite absorbing material prepared by ball milling can complement each other's strengths and weaknesses, reducing the dielectric constant without excessively reducing the magnetic permeability. By comprehensively balancing the electromagnetic parameters of these two absorbing materials, it is possible to obtain a higher magnetic permeability and a suitable dielectric constant in the low-frequency S-band, achieving electromagnetic control and achieving better low-frequency dielectric matching, and improving the low-frequency absorbing performance of the composite material.

The experimental results showed that with the increase of MnZn ferrite content, the agglomeration phenomenon of carbonyl iron after coating was improved. XRD shows that the phase is still Fe phase, and the dielectric constant increases first and then decreases with the increase of MnZn ferrite mass fraction, while the magnetic permeability also shows the same change. According to transmission line theory analysis, as the mass fraction of MnZn ferrite increases, the reflection loss peak first shifts to lower frequencies and then to higher frequencies. When the coating thickness is 2.5mm and the mass fraction of MnZn ferrite is 6%, the loss peak frequency of MnZn ferrite/carbonyl iron composite particles is the lowest, and its RL reaches -10.25dB at 1.65GHz.

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