Carbon nanomaterials for broadband EMI shielding

The increasing complexity of ultra-wideband (UWB) radar systems, high-frequency electronics, and densely integrated communication networks has intensified the need for lightweight, broadband electromagnetic interference (EMI) shielding materials. Conventional metallic shields, though highly conductive, are limited by high density and reflection-dominated mechanisms that increase secondary electromagnetic pollution and radar cross-section (RCS). This review critically examines carbon-based polymer composites as advanced alternatives for EMI shielding and stealth applications. Emphasis is placed on the role of carbon nanomaterials including carbon nanotubes, graphene, carbon nanofibers, and carbon black in forming percolative conductive networks that enable tunable electrical conductivity, interfacial polarization, and absorption-dominant shielding. Key parameters such as conductivity, permittivity, permeability, and thickness are analyzed in relation to impedance matching and broadband attenuation across UWB frequencies. Recent developments in hybrid systems incorporating MXenes, ferrites, and metamaterial-inspired structures are discussed for their ability to synergistically enhance dielectric and magnetic losses. The influence of fabrication techniques on microstructure and shielding effectiveness is also evaluated. Despite significant advancements, challenges related to dispersion, scalability, cost, and long-term stability remain critical barriers. This review provides a consolidated framework for designing next-generation multifunctional EMI shielding materials.