Biomass-Derived Integrated Hierarchical Porous Carbon Embedded with Ni@C Nanoparticles for High-Performance and Cost-Effective Microwave Absorbent Design

High-performance and cost-effective microwave absorbing materials are of vital importance in not only military but also civil fields. Here, an in situ generation-carbonization one-step method is proposed to synthesize excellent absorbents based on a common solid waste, willow catkins. The results demonstrate that the microwave absorption performance has been successfully improved owing to the magnetic particles, the core-shell nanoparticles, and the hierarchical porous structure, which results in strong conductivity loss, dielectric loss, magnetic loss, interface polarization, and multiple scattering. The maximum reflection loss (RLmax) reaches up to -50.66 dB and -49.09 dB, respectively, at 16.6 and 17.1 GHz with the thickness of 1.65 mm, resulting in double-peak absorption. What's more, the effective absorption bandwidth (EAB, RL < -10 dB) can get up to 5.7 GHz (from 12.4 to 18 GHz) with the thickness of 1.84 mm. Great absorption performance can be obtained simply through impregnation and carbonization, which constructs a fruitful and cost-effective paradigm for resource utilization of solid waste such as willow catkins.