Microwave absorption properties of carbonyl iron/EPDM composite

In order to explore the relationships among the thickness of , the volume content of absorbents in the RAM and the microwave absorption property, the radar absorbing material employed the carbonyl iron powder and ethylene-propylene-diene monomer (EPDM) as its absorbent and matrix was prepared. Effects of carbonyl iron's content and RAM's thickness on its microwave absorption properties in the range of 2.6-18 GHz were studied by a vector network analyzer. And the microwave absorption properties were analyzed using the electromagnetic theory. Results showed that the minimum reflectivity of RAM with thickness of 3 mm was-21.7 dB at 3.5 GHz when the carbonyl iron's content was 45%. Microwave absorption properties were not in direct proportion to its thickness when the RAM had the same carbonyl iron's volume fraction. Absorption effect of the radar absorbing material was relatively poor when the thickness was less than 2 mm. With the increase of thickness, the maximum absorption peak moved to low frequency band, its numeric value of maximum absorption peak decreased and the absorption bandwidth of the appointed reflectivity showed to be minished when the thickness was more than 2 mm. With the increase of carbonyl iron's content, reflectivity of the absorption peak for the radar absorbing material continuously decreased and the absorption peak also moved to the low frequency under the same RAM's thickness. And the closer to the air's impedance the input impedance was, the better the microwave absorption property was.