Morphology-Controlled Fabrication Strategy of Hollow Mesoporous Carbon Spheres@f-Fe₂O₃ for Microwave Absorption and...

The design and development of radar--infrared compatible stealth materials are challenging in the field of broadband absorption due to the contradiction of stealth requirements and mechanisms in different frequency bands. However, hollow structures show great promise for multispectral stealth because they can lengthen the attenuation path of electromagnetic waves (EMWs) for microwave absorption, interrupt the continuity of heat-transport channels, and lower the thermal conductivity to realize infrared stealth. Here, a new morphological fabrication strategy has been developed to efficiently prepare compatible stealth nanomaterials. In a specific hydrothermal process, the confined growth of flake α-Fe₂O₃ (f-Fe₂O₃) outside of hollow mesoporous carbon spheres (HMCS) is achieved using NH₃·H₂O as a shape-controlled reagent. The introduction of f-Fe₂O₃ helps to lower infrared emissivity and improve high-frequency impedance matching, which depends on the stable dielectric property of the specific flake shape. Moreover, the size of f-Fe₂O₃ can be regulated by changing the constituent proportion in the hydrothermal suspension to obtain excellent performance. The minimum reflection loss (RL) of the HMCS@f-Fe₂O₃-6 composite is -34.16 dB at 2.4 mm, and the effective absorption bandwidth (EAB) reaches 4.8 GHz. Furthermore, the lowest emissivities of the HMCS@f-Fe₂O₃-6-20 wt %/polyetherimide (PEI) film in the 3-5 and 8-14 μm infrared wavebands are 0.212 and 0.508, respectively. These discoveries may pave the way for the development of radar-infrared compatible stealth materials from the perspective of microstructural design.