Constructing interpenetrating structured NiCo2O4/HCNT composites with heterogeneous interfaces as low-thickness microwave absorber

Low matching thickness, broad effective absorption bandwidth (EAB, RL < –10 dB) and excellent reflection loss (RL) are desirable properties for the advanced microwave absorption materials (MAMs). We synthesized novel interpenetrating structured rod-like nickel cobaltite (NiCo 2 O 4 )/helical carbon nanotubes (HCNT) composites using the facile hydrothermal technique and heat-treatment process. Owing to the optimum structural design and electromagnetic parameter regulation, the NiCo 2 O 4 /HCNT composites displayed outstanding microwave absorption (MA) across regions of low thickness. When the thickness was only 1.35 mm, the optimized RL and EAB reached –55.9 dB and 4.8 GHz (13.2–18.0 GHz), respectively. Furthermore, the EAB was 10 GHz as the corresponding thickness was regulated with 1.35–2.10 mm, covering both X and the Ku bands. Multiple reflection and scattering, natural resonance, eddy current loss, strong conduction loss, interface polarization, cross-poalarization, and dipolar polarization can be considered to improve MA. Our study proposes a simple approach of synthesizing low-thickness MAMs based on NiCo 2 O 4 and HCNT .