Wave absorbing materials are widely used in military equipment to prevent the detection of radar wave and civil electromagnetic shielding. The absorbing properties of wave absorbing materials are determined by a combination of the electromagnetic parameters and the thickness of the composite material. In the actual processing process, the theoretical design of the reflection loss peak intensity and the bandwidth of wave absorbing materials deviate from the engineering practice. There are few reports on the variation of the intensity of the reflection loss absorption peak with thickness and the bandwidth mechanism of the reflection loss absorption peak. In this paper, based on an interfacial reflection model, the reflective properties of radar wave at the air interface of the absorbing coating were investigated. The dependence of the matching impedance on the matching thickness of the absorbing material was determined, and the matching impedance parameters were further used to design absorbing composites, which exhibit excellent microwave absorption properties with an average value of reflection loss(RL) being below -10 dB at 4-18 GHz in different thicknesses and an average value of reflection loss(RL) being below -20 dB at 6-18 GHz in different thicknesses. The bandwidth of the reflection loss peak at the matched thickness is discussed deeply in principle based on the interface reflection model and the theoretical calculations agree with the experimental results.
A variety of new challenges are being faced in the development of high temperature microwave absorbing materials in the X band. Recently, some of the 2:17 phase rare-earth soft magnetic alloys with high permeability and curie temperature have potential to be a novel X band high temperature microwave absorbing material. In this paper, a high temperature microwave absorbing material (Nd2Co17@C/Na2SiO3) is prepared with Nd2Co17 as a raw material. After carbon cladding and Na2SiO3 treatment, the composite can work stably at 723 K. The calculated absorption properties display that the reflection loss (RL) intensity of the composite with a thickness of 1.5 mm is below -6 dB in the whole X band. Moreover, the thermogravimetric (TG) analysis results and static magnetic properties before and after sintering indicate that the material has excellent resistance to oxidation. Rare earth alloy materials provide a new possibility for the research of innovative high temperature absorbing materials.
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