Regulating the vacancies of nitrogen-doped carbon nanohorns for high-performance electromagnetic wave absorption

Single-walled carbon nanohorns (SWCNHs), which are sealed on one side with a conical cap and can self-aggregate, are aggregates with spherical morphology ranging from 30 to 100 nm and include dahlia, bud, and seed structures. These SWCNHs are suitable for electromagnetic wave absorption (EMWA) due to their conductivity loss. However, conductivity loss, which is part of three primary loss mechanisms, leads to SWCNHs suffering from impedance mismatching and a narrow effective absorption bandwidth (EAB). In this work, the content of vacancy-type defects in "dahlia-like" nitrogen-doped single-walled carbon nanohorns (NSWCNHs) is regulated by dielectric barrier discharge (DBD) plasma with argon to adjust their polarization and impedance matching. The high-energy argon ions from the plasma impact the bonds between the carbon atoms and adsorbed oxygen, leading to the sputtering of oxygen atoms from the surface and resulting in an increase in surface disorder and defect content. Vacancy-type defects improved polarization loss and optimized impedance matching, leading to the satisfactory EMWA performance of NSWCNHs. The NSWCNHs exhibit an outstanding minimum reflection loss (RL_min) of -57.94 dB when subjected to argon DBD treatment for 5 minutes, achieving this remarkable result at a thickness of 1.9 mm. Additionally, the effective absorption bandwidth (EAB) can cover 4.78 GHz after a treatment period of 1 minute. These results suggest that NSWCNHs have great potential as high-efficiency EMWA materials and demonstrate a new approach for designing high-performance EMWA absorbers.