Well-Dispersed Ni Nanoparticles Loaded on Uniform Hollow N-Doped Carbon Spheres for Outstanding Microwave Absorption Performance at a Low Filler Loading

The agglomeration of magnetic nanoparticles can have a negative effect on the microwave absorption performance. However, the novel nickel-ion-polydopamine complex coating strategy can avoid this occurrence. Hence, ultrafine nickel nanoparticles (Ni NPs) with uniform size loaded on the surface of hollow N-doped carbon spheres (HNC(sic)Ni) have been fabricated by a facile method. The HNC(sic)Ni composites with different amount of nickel ions are investigated. Interestingly, the introduction of nickel ions has three advantages: (1) Decreases the rate that dopamine self-polymerizes into polydopamine, thus avoiding the serious agglomeration. (2) Improves the thermal stability and maintain the original shape without destroying. (3) Acts as a catalyst to enhance the degree of graphitization. Because of the increase of interfacial polarization and conduction loss, the HNC(sic)Ni composites with only 10 wt.% filler loading possess better microwave absorption performance compared to HNC (without adding nickel salt), covering the whole Ku band and the entire X band. Surprisingly, the broadest effective absorption bandwidth (EAB) for three samples of HNC(sic)Ni composites are all 6.8 GHz (11.2-18 GHz). The minimum reflection loss (RLmin) reaches -55.15 dB for HNC(sic)Ni-1 and -62.96 dB for HNC(sic)Ni-2. We believe that this work provides a high-production and low-cost route to synthesize advanced microwave absorption absorbers. [GRAPHICS] .