A Multiresonant Ultrabroadband X/Ku-Band Honeycomb Absorber Filled With MXene Aerogel in Inverted-Hexagonal Pyramidal Cavities

This letter presents an ultra-broadband, lightweight honeycomb absorber for X/Ku-band (8–18 GHz) applications to address the persistent challenge of balancing wide bandwidth with structural utility. The proposed absorber features a simulation-optimized structure with inverted-hexagonal pyramidal cavity which extends the wave path by 210% to excite multi-resonant modes as well as a 45% MXene aerogel filler that provides tailored dielectric loss, thereby enabling full-band coverage. The fabricated absorber achieves an exceptional −10 dB absorption bandwidth of 11.36 GHz, with excellent agreement between simulation and measurement (error < 3%). The minimum reflection loss is notably as deep as –38.19 dB. Mechanically, the unit cell demonstrates a high load-bearing capacity, with compressive tests showing a plateau stress 2–2.5 times greater than that of a conical unit, while maintaining a low overall density of 0.23 g/cm³ and exhibiting robust angular stability. This work provides a compact and structurally robust solution for next-generation 5G base stations and airborne radar systems, where ultrawideband absorption and mechanical load-bearing are simultaneously required.