Periodic cavity-induced dielectric response enhancement enabling magnetic metal alloy@N-doped bamboo-like carbon nanotubes with broadband absorption and corrosion protection

Effective modulation of dielectric response serves as the key to enhancing electromagnetic wave absorption performances (EMWAPs), while a periodical hollow cavities (PHCs) structure provides an ideal material platform to achieve this goal. This study leverages metal (Fe/Co/Ni)-nitrilotriacetic acid chelate precursors and dicyandiamide (DCD) as a bifunctional carbon/nitrogen source to propose a simple synthesis strategy for preparing metal alloy@N-doped bamboo-like carbon nanotubes (N-BLCNTs) featuring PHCs magnetic/dielectric composites (MDCs). Simultaneously, adjusting the pyrolysis temperature, categories of initial reactants, and DCD content allows the precise regulation of graphitization degree, kind, and electromagnetic parameters for the resulting MDCs. Benefiting from the optimized dielectric response and magnetic/dielectric synergy regulated by the PHCs, together with the interfacial polarization, the CoNi@N-BLCNTs exhibit outstanding corrosion resistance and EMWAPs with an effective absorption bandwidth of 7.80 GHz and a minimum reflection loss of −58.62 dB. In summary, this work provides a scalable and versatile platform to develop the desirable novel microwave absorbers featuring broad bandwidth, strong absorption, and environmental adaptability.