Resin-free aramid honeycombs with extraordinary microwave absorption, thermal insulation, flame retardant and mechanical performance

Abstract

Although lightweight aramid paper honeycombs are highly desirable for microwave absorption owing to their dual functions of both load-bearing and microwave-absorbing, unsatisfactory microwave absorption, inferior mechanical and inadequate thermal properties present significant challenges for practical applications in diverse complex scenarios. Herein, lightweight, high-strength and flame-retardant aramid nanofibers-based honeycombs (MANHs) for integrated microwave absorption and thermal insulation are successfully fabricated via the hydrogen bonding assembly, mold forming and aerogel filling strategy using aramid waste as raw material. The dense network structure formed by the interwoven aramid nanofibers (ANFs) in the honeycomb body acts as a framework endows the MANH with impressive mechanical performance, and the specific strength and toughness of MANH reach 153.6 MPa g⁻¹ cm⁻³ and 13.9 MJ m⁻³, respectively, which are 3.5 and 19 times higher than those of commercial microwave absorption honeycombs (CMAH). The ultralight MXene/ANFs aerogels (a density of 25 mg cm⁻³) with multiscale pore structure filled in the honeycomb apertures give the honeycomb outstanding microwave absorption performance, with a minimum reflection loss of −62.5 dB, and can cover the entire X-band with a thickness of only 3.5 mm. Meanwhile, compared with CMAH, the thermal insulation and flame-retardant performance of MANH are also significantly improved. Notably, MANH also demonstrates favorable sound absorption performance at high-frequency bands. The MANH is considered to be a promising candidate for aerospace and military stealth applications as a result of its lightweight, high strength, exceptional microwave absorption, and remarkable thermal insulation performance.