Single layer coconut shell-based microwave absorbers

This paper presents a study of single layer radar absorbing material made using coconut shell-based activated carbon. Flaxane-80 was used as binder and was mixed to give 10 wt%, 15 wt%, 20 wt% and 25 wt% variation of activated carbon obtained from coconut shell to study the microwave properties of the absorber material. An industry standard electromagnetic simulator was used to predict the absorber behaviour, while microwave non-destructive testing (MNDT) technique was used to measure microwave properties and reflection characteristics of the samples. The relative permittivity of 25 wt% carbon sample was found to be the highest with a value of 12. The sample also has the highest tan δ of 0.4. The thicknesses of absorbers made of 25 wt% carbon were varied at 3.2 mm, 6.4 mm, 9.6 mm and 13.8 mm to determine the reflection characteristics. The 6.4 mm sample was found to offer minimum reflection at 9.6 GHz with -22 dB reflection loss. Sample 9.6 mm has a minimum reflection loss of -17dB at 11.3 GHz. The results of this study offer great opportunities for RF application seeking for low cost and light-weight radar absorber material using coconut-shell.