Tunable Microwave\nAbsorbers Using Hierarchical-Structured\nComposites of Carbon Nanotubes with Low-Frequency Minimum Reflection\nLoss

Abstract

Tunable\nstrong microwave absorption (MA) materials with minimum\nreflection loss (RL_min) in the low-frequency range (2–8\nGHz) are crucial for civilian and military applications, yet remain\ninsufficiently explored. Herein, we design and fabricate hierarchical-structured\ncarbon nanotube (CNT)/Fe₃O₄(FeS₂)/MoS₂ composite materials using a facile solvothermal and hydrothermal\nsynthetic method, achieving tunability in MA frequencies from the\nS-band (2–4 GHz) to the C-band (4–8 GHz) by manipulating\nthe sulfur source. The optimal sample exhibits an RL_min of −70.06 dB at 3.74 GHz, a maximum effective absorption\nbandwidth (EAB_max) of up to 5.6 GHz at 2–18 GHz,\nand an EAB_max of 2.1 GHz at 2–8 GHz. Furthermore,\nthe optimal sample shows excellent radar cross-section values and\nrobust corrosion-resistive properties for practical radar stealth\nwithin corrosive environments. Our work provides a strategy to fabricate\nnot-previously reported tunable strong microwave CNT-based absorbers\nwith RL_min in low frequencies and give insights into their\nstructures, physical properties, and potential applications.