Mimicking ‘sea-urchin’ like heirarchical carbon structures self-assembled from carbon fibers for green EMI shielding

•‘Self-assembly’ of micro-spikes from carbon fiber mimicking ‘sea-urchin’ like structures.•Size of the carbon-urchins depend on the chemical ambience.•Green EMI shielding materials.•The shielding effectiveness was as high as -52 dB in X-band with green index close to 1.•Excellent thermal interface material. Self-assembled structures offer myriad opportunities to explore them for a wide range of applications. Herein, ‘sea-urchin’ like hierarchical structures were obtained from self-assembly of carbon fibers (CF) assisted by refluxing in an acid medium. This unique template-free synthesis of carbon urchins (CU) yields different sizes when the chemical ambiance (pH) around the CF varies. Electromagnetic (EM) pollution has recently gained attention due to the widespread usage of electronics and requires lightweight and reliable solutions to suppress EM interference. Polymer nanocomposite-based shielding serves as an effective solution due to its ability to be tuned as per the commercial requirement. To this end, dispersing flakes of nanoparticles in a polymer matrix has been researched widely but is not amenable to suppressing the EM interference. Herein, the self-assembled structures offer micro-spikes resulting from the sea-urchin-like carbon structure coupled with the incoming field and facilitate the absorption of the EM radiation. The spatial distribution of CU was controlled in different polymeric matrices (thermoplastic, Ethylene vinyl acetate (EVA) and thermoset, epoxy) to realize the potential of these hierarchical structures in EMI shielding applications. The composites with CU show shielding effectiveness (SET) in the range of -45 dB to -52 dB in the X-band, and the green index is close to 1. The shield with the highest SET also showed a quick heat dissipation ability, an added advantage in terms of applicability. Our results begin to suggest that CU can be blended with a wide range of plastics to develop a universal solution in designing lightweight composites for EMI shielding applications. [Display omitted]