Expanded graphite-Phenolic resin composites based double layer microwave absorber for X-band applications

In this investigation, double layer microwave absorbers are designed and developed with paired combination of 5 wt.%, 7 wt.%, 8 wt.%, and 10 wt.% expanded graphite-novolac phenolic resin (EG-NPR) composites, in the frequency range of 8.2-12.4 GHz. The thickness and compositional combination of the two layers constituting the absorber are optimized to achieve minimum value of reflection loss (dB) and a broad microwave absorption bandwidth. Double layer combinations showing 25 dB absorption bandwidth >2GHz and 30 dB absorption bandwidth >1GHz are chosen for fabrication. The total thickness of the fabricated double layer microwave absorber is varied from 3mm to 3.4 mm. Absorption bandwidths at 10 dB, 20 dB, 25 dB and 30 dB are determined for the fabricated structure. The maximum 25 dB and 30 dB absorption bandwidth of 2.47 GHz and 1.77GHz, respectively, are observed for the double layer structure with (5wt.%-8 wt.%) EG-NPR composites with total thickness of 3.2mm, while 10 dB bandwidth covers the entire X-band range. (C) 2014 AIP Publishing LLC.