| Currently,the development and design of composites with exceptional electromagnetic wave absorption properties are increasingly crucial in preventing and controlling hazards caused by excessive exposure to electromagnetic radiation.These composites have diverse applications across military and civilian domains.Biomass offers numerous advantages,such as cost-effectiveness,lack of pollution,renewability,and abundant resources.Empirical verification has confirmed that it is a fundamental source of novel porous carbon,which can be utilized in the design of electromagnetic wave absorption materials.Due to the substantial annual discards of bagasse,its derived carbon possesses numerous advantages such as lightweightness,porousness,and high specific surface area.Therefore,it is an ideal carrier for magnetic components like ferrites and magnetic metals.By leveraging the synergistic effect of magnetic loss,it can be fine-tuned to achieve exceptional electromagnetic wave absorption capabilities.This article delves into two aspects based on the aforementioned:A series of Co/Ni decorated bio-based porous carbon spheres were prepared using the activation-hydrothermal-calcination method.The impact mechanisms of activator content and precursor concentration on their composition structure and electromagnetic responsiveness properties were investigated.Subsequently,the impact of calcination temperature on the porosity,particle morphology,and electromagnetic absorption mechanism of NiCo2O4/CoO supported by porous carbon was investigated,culminating in the production of a flexible self-cleaning absorbent plate.The relevant research findings are as follows:（1）The porosity of Co/Ni decorated bio-based porous carbon spheres is greatly influenced by the quantity of activator added.The material attains its maximum porosity of74.25 m2/g when the mass ratio between activator and porous carbon is 1:2.By adjusting the concentration of cobalt/nickel precursor solutions,the content and structure of Co/Ni nanoparticles decorated on the surface of porous carbon spheres can be modulated.This approach facilitates achieving optimal impedance matching properties while also modulating effects such as magnetic resonance and interface polarization in composites,ultimately leading to excellent absorption performance.At a thickness of 2.5 mm,the maximum reflection loss reaches-76.54 dB at 12.23 GHz,and the effective absorption bandwidth covers the entire Ku band with an ultra-wide range of 7.3 GHz（10.7-18 GHz）achievable at 2.3 mm.The phenomenon can be attributed to the contributions of natural resonance,exchange resonance,quarter-wavelength destructive interference,as well as auxiliary polarization relaxation and structural scattering effects.（2）The calcination temperature exerts a significant influence on the carbon porosity and morphologies of NiCo2O4/CoO particles supported by porous carbon composites.The maximum pore size of the porous carbon was achieved after calcination at 350℃,with an average diameter of 1.13μm.With the increase of calcination temperature,nickel-cobalt ferrite particles exhibit a distinctive strip-like morphology,while CoO particles undergo a transformation from nanosheets to cauliflower-like morphology.At a thickness of 2.5 mm,the material exhibits a maximum reflection loss of-48.41 dB at a frequency of 9.12 GHz,while at a thickness of 2.2 mm,it demonstrates an effective absorption bandwidth ranging from 8.65 to 12.97 GHz with a maximum value of 4.32 GHz.The strong coupling effect of dielectric polarization,magnetic resonance,and eddy current loss enhances the effective microwave absorption in the intermediate frequency X band when suitable impedance matching is achieved.The composite-based absorbent plate not only exhibits hydrophobic self-cleaning properties,but also possesses exceptional flexibility and high breaking strength. |
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