Salt template assisted preparation of magnetic modified nitrogen doping hollow carbon microcapsules for broadband microwave absorption

The rational structural design and precise compositional regulation of lightweight and broadband carbon-based absorbing materials is an urgent task at present to deal with the complex electromagnetic environment. The soluble salt template assisted preparation technology holds good feasibility for constructing unique hollow carbon-based microwave absorbents due to their reusability and economy of salt templates. Nevertheless, magnetic modified nitrogen doping hollow carbon microcapsules fabricated by employing salt-template technique have not been explored. Herein, we adopt a green and low cost NaCl soluble salt template assisted synthesis strategy to universally fabricate 3D unique hollow carbon-based microwave materials loaded with precursors of magnetic particles. Following the high-temperature pyrolysis and wash desalting template, we have successfully achieved mass preparation of magnetic modified nitrogen doping hollow carbon microcapsules. Benefiting from the unique chemical component dominance and distinctive structural merits, the optimized Ni magnetic modified nitrogen doping hollow carbon microcapsules (Ni@N-HCNs) delivered extremely outstanding microwave absorption performance (MAP), including an optimal minimum reflection loss value (RLmin) of −37.7 dB and an effective absorption bandwidth of 5.5 GHz under a filling level of only 5 wt%. More excitingly, the widest effective absorption bandwidth could cover up to 7.87 GHz (10.03–18.0 GHz) at a thin matching thickness of 2.6 mm. Due to the large-scale production and simple preparation process, Ni@N-HCNs composites might be considered as one of the most competitive candidates for the design of lightweight and high performance microwave absorbents.