Multilayer Polyvinyl Alcohol/Carbon Composite Aerogels with Broadband Microwave and Noise Absorption and Novel Shape Memory Effect

Abstract With the advent of 5G and 6G technologies, the proliferation of high‐power electromagnetic devices raises significant concerns regarding electromagnetic pollution and noise contamination, threatening data security, electronic functionality, and human health, particularly with the increasing exploration of marine environments. While microwave absorption materials have advanced, their underwater application remains limited due to narrow absorption bandwidth, low efficiency, poor mechanical stability, and complex fabrication processes. To address these limitations, a multilayer graded‐structure polyvinyl alcohol/carbon aerogel composite using high‐speed stirring, foaming, and freeze‐drying techniques is proposed. The resulting aerogels demonstrate exceptional underwater compression recovery capabilities (2000 cycles at 90% strain), shape memory effect, and superior underwater noise reduction performance. The graded structure allows for precise tuning of dielectric properties, achieving broadband microwave absorption (12.7 GHz). Additionally, the unique water adhesion properties of the aerogels facilitate simple multilayer assembly, thereby enhancing structural integrity. Radar cross‐section (RCS) simulations perform on a submarine model show excellent stealth performance, with a minimum RCS value reaching −52 dBsm. This study presents a cost‐effective approach to developing multifunctional materials that address the challenges of broadband microwave absorption and noise pollution in underwater environments, suitable for marine applications, including radar stealth technologies and submarines noise‐dampening systems, etc.