Hierarchically nitrogen-doped carbon hollow microspheres assembled with loose and porous magnetic carbon sheets for enhanced microwave absorption

Combining hollow materials with magnetic particles to construct hierarchical structures favors enhancement of microwave absorption properties. However, the fabrication of the well-defined materials possessing both hollow and hierarchical features still faces a huge challenge. Herein, a facile two-step method is developed to synthesize hierarchically nitrogen-doped carbon hollow microspheres assembled with loose and porous magnetic carbon sheets. Especially, many magnetic Fe/Fe3C NPs covered with N-doped graphitic layers are embedded in the mesoporous N-doped carbon sheets layers. Benefited from the special structure, the optimal nitrogen-doped carbon hollow microspheres exhibit an excellent microwave absorption property with an EAB of ∼4.00 GHz at a thickness of 2.5 mm and the minimal reflection loss of −39.87 dB at a frequency of 7.76 GHz, while the filler ratio is only 10 wt% in the paraffin wax. Electromagnetic parameters analysis reveals that unique hierarchical structure and rich heterogeneous interfaces result in the enhancement of dielectric and magnetic losses as well as optimized the impedance matching. The computer simulation technology (CST) simulation further verifies the practical applicability of the optimal nitrogen-doped carbon hollow microspheres. This work provides an effective way for the efficient synthesis of hierarchical and hollow materials for microwave absorption.