Geometry Dependent Microwave Absorption Properties in Carbonaceous Materials over X-Band Frequencies (8.2-12.4 GHz) for Stealth Applications

Abstract

: Carbonaceous materials of two different types, viz. spherical nano carbon black (NCB) powder (Brunauer-Emmett-Teller (BET) surface area ~1400 m2/g) and multiwalled carbon nanotube (MWCNT) (BET surface area ~75 m2/g), have been impregnated in room temperature vulcanized (RTV) silicon rubber matrix to study the effect of geometries of filler particles on microwave absorption characteristics, over X-band frequencies (8.2 -12.4 GHz). The rubber-based composites are prepared by dispersion of NCB and MWCNT fillers in the liquid rubber with loading fractions ranging from 0.3-0.9 wt% and 1.1-1.7 wt%, respectively. The dielectric loss tangent (tanδe) profiles were evaluated for the filler-loaded rubber composites at different concentrations. The calculated Reflection loss (RL) profiles suggest that NCB-based rubber provides maximum RL value, (RL)max ~ -20 dB (99.00 % absorption), at a lower filler concentration of 0.5 wt%, as compared to MWCNT. However, the MWCNT-based rubber composite shows enhanced (RL)min values of ~ -29 dB (~99.99% absorption) due to multiple scattering phenomena. The identified NCB and MWCNT-based rubber-based MW absorbers have potential stealth applications for military aerial vehicles.