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The increasing use of high-frequency electromagnetic technologies, including advanced radar systems, millimetre-wave communications, and emerging sub-terahertz applications, creates a growing demand for lightweight, flexible, and efficient electromagnetic shielding materials. Conventional conductive shields predominantly reflect incident radiation, whereas practical applications increasingly require absorption-dominant shielding that minimizes secondary electromagnetic interference. This work presents two complementary strategies for developing thin, scalable polymer–inorganic composites with enhanced microwave and sub-terahertz absorption: engineering magnetic core–satellite pigment fillers and integrating functionally graded multilayer coatings with woven carbon fabric metastructures. The first strategy involves modifying an industrial copper chromite-based pigment with metallic nanoparticles to enhance its electromagnetic response. The original multiphase pigment, comprising predominantly CuCr₂O₄ spinel together with chromium oxide and hematite, exhibits interfacial polarization but relatively weak magnetic properties. Surface functionalization with an aminosilane followed by the chemical reduction of nickel or silver precursors produces core–satellite architectures. Nickel decoration increases the saturation magnetization approximately fourteen-fold, from 3.5 to 48 emu/g, and raises the composite permittivity from 6.8 to 8.8. In metal-backed X-band measurements, an epoxy composite containing nickel-decorated pigment achieves a reflection-loss minimum of -24.7 dB at 10.2 GHz with a thickness of only 2.6 mm, corresponding to more than 99% absorption at the resonance minimum. In contrast, silver decoration produces comparatively modest improvements, highlighting the importance of magnetic losses in conjunction with dielectric dissipation. The second strategy exploits the intrinsic quasi-periodic architecture of twill-woven carbon fabric as a scalable electromagnetic metastructure. The fabric is coated with a functionally graded sequence of plasticized epoxy layers containing graphite nanoplatelets and magnetic fillers, including nickel or γ-Fe2O3. The layer arrangement is designed to provide a gradual impedance transition from air towards the conductive substrate while combining ohmic, dielectric, magnetic, and geometric resonance effects. The resulting flexible composites are approximately 1.3-1.8 mm thick. Free-space quasi-optical measurements demonstrate absorption-related shielding contributions reaching 75-80 dB across the 90-330 GHz range, accompanied by reflection-related shielding contributions below approximately 5 dB over most of the measured band and near-zero reflection above 250 GHz. The response also exhibits pronounced polarization dependence associated with the fabric weave. A transfer-matrix model incorporating magnetic dispersion and anisotropic effective permittivity reproduces the measured behaviour using a consistent parameter set, supporting the interpretation that the observed performance arises from coupled resonances rather than a simple additive effect of individual layers. Auxiliary samples further demonstrate the critical role of the first graphite-containing layer in establishing impedance matching and coupling the multilayer stack to the fabric metastructure.
Together, these results establish complementary materials-design approaches for lightweight, absorption-dominant electromagnetic shielding. Combining engineered magnetic fillers with naturally structured carbon fabrics offers a promising, scalable route towards broadband absorbers for high-frequency electronics, radar-related applications, and electromagnetic protection.
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