Carbon Nanocage‐in‐Microcage Structure With Tunable Carbon‐Coated Nickel as a Microwave Absorber With Infrared Stealth Property

The rational design of microwave absorption (MA) material featuring light weight, wide absorption bandwidth, and infrared stealth property is crucial for military stealth and health protection but remains challenging. Herein, an innovative N-doped carbon nanocage-in-microcage structure with tunable carbon-coated Ni (NC/Ni(HS)) is reported via a reliable Ni-catalyzed and Ni-templated method. The hierarchically hollow structure of nanocage-in-microcage composites can optimize the impedance matching and respond to multiple reflections and scattering of incident microwaves and infrared waves. Moreover, the magnetic Ni nanoparticles improve the synergistic interactions between confined heterointerfaces and promote interfacial polarization. Such an ingenious structure endows NC/Ni(HS) with outstanding MA performance and infrared stealth properties. Specifically, NC/Ni(HS)-10 with an optimal dielectric property, exhibits excellent MA performance. At an ultralow fill loading of 4 wt.%, a wide absorption bandwidth of 6.16 GHz is achieved at a thickness of 2.63 mm, and a strong reflection loss of -63.67 dB is obtained at a thickness of 2.00 mm. In addition, NC/Ni(HS)-10 shows a low infrared emissivity in the range of 3‒14 µm, which is the key to compatibility with infrared stealth. This work paves the way for the design of advanced MA materials that meet the requirements of multispectral-compatible stealth.