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

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 (epsilon(r) = epsilon'(r) - j epsilon '') 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 5 wt.% EG/NPR composite shows measured reflection loss peak of value similar to-43 dB at 12.4 GHz which is in close agreement with that of calculated reflection loss value 53 dB at the same frequency. The reflection loss peak shifts towards low frequency with increase in wt.% of EG and a -10 dB absorption bandwidth similar to 1 GHz is found for conductor backed single layer absorber with 7, 8 and 10 wt.% EG/NPR compositions. (C) 2013 Elsevier Ltd. All rights reserved.