Impressive Transmission Mode Electromagnetic Interference Shielding Parameters of Graphene-like Nanocarbon/Polyurethane Nanocomposites for Short Range Tracking Countermeasures

Shielding the microwave signature (8.2–12.4 GHz, X-band) of a locked in target is a tactically important electronic countermeasure. Herein, we report on mitigation in X-band transmission mode shielding parameters for polyurethane (PU), after incorporating graphene-like nanocarbon sheets (GNCs). Initially, PU and variable weight percent (1–25) GNCs/PU paste samples were subjected to Fourier transform infrared, Raman spectroscopy, and scanning electron microscopy. These samples were molded into toroidal shaped specimens by adiabatic hot-pressing technique, for microwave scattering measurements. Parameters, such as complex permittivity (ϵ′–jϵ″), alternating current (ac) conductivity, skin thickness, transmission (S₂₁), effective transmission loss (SE_T), and shielding effectiveness were determined, in addition to direct current (dc) conductivity. The real and imaginary components are increased, respectively, by ∼5 and ∼30 times, whereas loss tangent, by ∼7, at 25 wt % loading of GNCs. The ac conductivity is enhanced from 0.248 (PU) to 7.288 S/m (25 wt %) by maximizing transmission loss to −26.45 dB (99.9%) and minimizing thickness to 1–2 mm. The dc percolation threshold is found to be low at ∼5 wt %, indicating superior dispersibility of GNCs, thereafter. In analysis, the atomic polarization (at ∼10 GHz) associated with the aromatic urethane amide rings acts as a backbone to engage incident electromagnetic field wiggles. The coupling occurs via charge transfer polarization currents at doubly bonded nitrogen, oxygen, and hydrosorpted sp³ carbon sites in GNCs. The field–matter interaction is dominant at the microvoid skin interface between GNCs and PU. Possible polarization mechanism is explained. The GNCs/PU nanocomposites are realized as an effective electromagnetic interference shielding block in the tracking band. The details are presented.