Investigation Of Fire-retardant And Microwave Absorbing Performance Of Absorbers In Microwave Anechoic Chamber

The fire-retardant performance of compound shell materials and microwave absorbing performance of the inside filling materials use for Absorbers in Anechoic Chamber is studied in the paper. For the shell, in order to improve the fire-retardant of shell of the absorption materials, a novel compound shell material (CSM) which based on the fiber-glass was synthesized. The fiber-glass material, which is low-dissipative and flexible, has good nature of fire-retardant and corrosion resistance. That is the reason that it is widely used in the various architectures. The novel compound shell material (CSM), which is mostly made by fiber-glass material, is improved greatly in the nature of fire-retardant. In the same time, the rectangular shell was prepared by polypropylene cored slab (PCS). The reflection loss (RL) of CSM and PCS were measured using a reflection method in a range from 2 to 18 GHz. The result indicated that containing CSM composite material exhibited good absorption property at low frequency compared to PCS. Whereas, the RL of the composite material was decreased at high frequency.By our analyse, when the microwave is reflected, the reflection loss (RL) is mostly depended on the difference between the intrinsic impedance of two interface.In thispaper, the exist of epikote has influence to the reflection loss. Theε_r andμ_r of epikote is changing along with the frequency of microwave.So the intrinsic impedance has shift, which influence the impedance matching.as a result,the difference of the capability between the low frequency and high frequency happened.For the inside absorbing material, MnO₂ was coated on the EPS-based absorbing spheres by fluid coating in this work. MnO₂ has been using as electrode material for many years since its first applation in 1865 byLanclanche. Now, it is the one of the most widely used electrode materials in the batteries. Meanwhile, MnO₂ is the primary element in the ferrite material.With many closed cavums, the EPS sphere could be considered as a perfect absorber base for its light-weight, high-intensity, good chemical stability and mechanical property. The results demonstrate this method to be efficient in coating dense conductive powder. The proof sample with a thickness of 10mm have an absorbing property of - 8～- 15dB in the frequency 8～18GHz. Moreover, the absorbing property increases with the increasing MnO₂ content in the absorber within the same frequency range. The absorbing property of the spheres covered by MnO₂ is lower than that covered by carbon black with the same thickness of the conductive layer.