Tunable Microwave Absorbers Using Hierarchical-Structured Composites of Carbon Nanotubes with Low-Frequency Minimum Reflection Loss

Tunable strong microwave absorption (MA) materials with minimum reflection loss (RLmin) in the low-frequency range (2–8 GHz) are crucial for civilian and military applications, yet remain insufficiently explored. Herein, we design and fabricate hierarchical-structured carbon nanotube (CNT)/Fe3O4(FeS2)/MoS2 composite materials using a facile solvothermal and hydrothermal synthetic method, achieving tunability in MA frequencies from the S-band (2–4 GHz) to the C-band (4–8 GHz) by manipulating the sulfur source. The optimal sample exhibits an RLmin of −70.06 dB at 3.74 GHz, a maximum effective absorption bandwidth (EABmax) of up to 5.6 GHz at 2–18 GHz, and an EABmax of 2.1 GHz at 2–8 GHz. Furthermore, the optimal sample shows excellent radar cross-section values and robust corrosion-resistive properties for practical radar stealth within corrosive environments. Our work provides a strategy to fabricate not-previously reported tunable strong microwave CNT-based absorbers with RLmin in low frequencies and give insights into their structures, physical properties, and potential applications.