Multi-scale CoNi nano-alloy/CoNi@C microsphere/3D macropores N-doped carbon foam composites: Lightweight and efficient electromagnetic wave absorption characteristics

Abstract

Light carbon foam is considered to be one of the most promising candidate materials to provide excellent electromagnetic absorption properties in portable electronics and aerospace. However, it is still a challenge to prepare a wide-band, strong-absorbing carbon foam. In this work, melamine foam was used as a template and nitrogen source. We adopted the template method with simple operation and controllable microstructure, a new multi-scale CONi nanoalloy/CoNi@C microsphere/3D macropores porous N-doped carbon foam (CoNi/MF-P) composite material was prepared by simple hydrothermal and subsequent pyrolysis processes in an inert atmosphere as a microwave absorber. On the surface of the microstructure, CoNi nanocrystals (CoNi NCs) dispersed in the CoNi@C microspheres, and all the CoNi@C microspheres are uniformly attached to the edge of the carbon foam, and the complete melamine three-dimensional structure is retained. Combining the synergistic advantages of dielectric loss, magnetic loss and nano/micro/macropores porous structure, at a filling amount as low as 20%, it shows much higher electromagnetic wave (EMW) absorption performance than the carbon foam control group without CoNi NCs attached. It was observed that the effective absorption bandwidth of CoNi/MF-P4 covered the whole Ku-band frequency range of 11.93–18 (6.07) GHz, and the absorber thickness was only 1.6 mm. The minimum reflection loss (RLmin) of CoNi/MF-P5 was −60 dB at 3.98 GHz. At the same time, in the thickness range of 1.2–5 mm, a super broadband of 14 GHz (4–18 GHz) was also obtained. These results indicate that the interfacial interaction and synergy between CoNi NCs, CoNi@C and N-doped carbon foam play an important role in enhancing microwave absorbing properties.