Single layer microwave absorber based on expanded graphite–novolac phenolic resin composite for X-band applications

Abstract

Expanded graphite–novolac phenolic resin (EG/NPR) composites in (5, 7, 8 and 10)wt.% of EG are developed as dielectric radar absorbing material in the X-band. Complex permittivity (εr=εr′–jεr″) of the composites measured in X-band are used to compute the reflection loss (RLc) of conductor backed single layer EG/NPR composites by optimizing the composites thickness (d). Practical reflection loss measurements are carried out using free space technique. Impedance matching condition and quarter wavelength criteria are used for analysis of the reflection loss performance of the composites. The 5wt.% EG/NPR composite shows measured reflection loss peak of value ∼−43dB at 12.4GHz which is in close agreement with that of calculated reflection loss value ∼ −53dB at the same frequency. The reflection loss peak shifts towards low frequency with increase in wt.% of EG and a −10dB absorption bandwidth ∼1GHz is found for conductor backed single layer absorber with 7, 8 and 10wt.% EG/NPR compositions.