Construction of cactus-like BNNS@C composites with enhanced microwave absorption properties

Abstract

Addressing growing electromagnetic pollution, carbon materials, with low density, high specific surface area, designability, and excellent dielectric properties, are strong candidates for electromagnetic wave absorption. However, their high conductivity causes poor impedance matching, severely limiting applications. By combining them with BN materials that have a low dielectric constant and controlling their morphology and interfacial bonding at the micro-nano scale, it is expected to resolve this issue. Therefore, by constructing a carbon nanoparticle coating layer on the surface of boron nitride nanosheets (BNNS), cactus-like BNNS@C composites were successfully prepared. The results indicated that the carbon nanoparticles were uniformly distributed on the surface of BNNS. Importantly, this BNNS@C composites exhibit relatively low graphitization degree, high defect content, and nitrogen doping characteristics. And at the thickness of 1.0 mm, the cactus-like BNNS@C composites achieved a minimum reflection loss value (RL_min) of −35.54 dB and an effective absorption bandwidth (EAB) of 2.86 GHz (15.14–18.00 GHz). This benefit was due to the conduction loss, dipole polarization loss, and the multiple reflection losses within the heterogeneous interfaces of the cactus-like BNNS@C composites. Therefore, this study provides a reliable reference for the preparation of lightweight and thin high-efficiency microwave absorbing composite materials.