Magnetic porous N-doped carbon composites with adjusted composition and porous microstructure for lightweight microwave absorbers

Composition and microstructure are two determinative factors for carbon-based absorbers, therefore, balancing the dual coordination possess a formidable importance in the final performance. In this paper, magnetic particles (Fe, Co and Ni) encapsulated in porous N-doped carbon as lightweight and efficient microwave absorbers are reported. The coordination assembly strategy is firstly used to fabricate metal-organic polymer coordination composites, then, these metal ions are in situ reduced by a carbonization process, resulting in magnetic porous N-doped carbon (Fe@PNC, Co@PNC and Ni@PNC) composites with adjusted composition and porous microstructure. Benefiting from the porous microstructure with large surface area, enhanced polarization loss and the synergetic effects between magnetic and dielectric loss, the composites exhibit unexceptionable attenuation ability. Concretely, the minimum reflection loss for Fe@PNC, Co@PNC and Ni@PNC reaches as high as −61.6 dB, −65 dB and −65.1 dB with the matched thickness of 2 mm, 2.5 mm and 3.5 mm, and the effective bandwidths are 5.3 GHz (at 3.4 mm), 6.7 GHz (at 2 mm) and 8.6 GHz (at 2.5 mm), respectively. This strategy provides not only a new guidance in the fabrication of carbon absorbers, but also a comprehension in the structure design and composition control through the chelating ability.