New structural design achieves full-frequency microwave absorption with carbon nanotubes

A recent study has demonstrated a novel approach to creating ultra-wideband microwave absorbers using carbon nanotubes (CNTs). Instead of altering the material's chemical composition, researchers achieved exceptional performance through precise macroscopic structural engineering.

The primary challenge with highly conductive CNTs is their tendency to reflect microwaves due to impedance mismatch, preventing the waves from entering the material to be absorbed. To solve this, the research team developed a multilevel structural regulation strategy using CNT film strips on a polyethylene terephthalate (PET) nonwoven substrate.

The optimized design involves three key structural features:

• Longitudinal Regulation: Incorporating low-permittivity PET interlayers to facilitate electromagnetic wave entry.
• In-Plane Patterning: Reducing the CNT coverage to an optimal 67%, which provides the best compromise between wave entry and energy dissipation.
• Staggered Stacking: Alternately stacking complementary patterned layers to redistribute CNT-rich regions and eliminate continuous pathways for wave reflection.

The resulting optimized absorber, designated S67-P5-R15, achieved continuous reflection loss below −10 dB across the entire 2–18 GHz frequency range. This corresponds to an effective absorption bandwidth of 16.0 GHz with a total thickness of only 18.0 mm. This breakthrough, recently published by Frontiers of Materials Science, demonstrates that highly efficient, broadband microwave absorption can be realized through intelligent structural design, offering a promising path for developing lightweight and high-performance materials for electromagnetic compatibility and stealth applications.