Combinatorial Structural Engineering of Multichannel Hierarchical Hollow Microspheres Assembled from Centripetal Fe/C Nanosheets to Achieve Effective Integration of Sound Absorption and Microwave Absorption

Abstract

Electromagnetic radiation and noise pollution are two of the four major environmental pollution sources. Although various materials with excellent microwave absorption performances or sound absorption properties have been manufactured, it is still a great challenge to design materials with both microwave absorption and sound absorption abilities due to different energy consumption mechanisms. Herein, a combination strategy based on structural engineering was proposed to develop bi-functional hierarchical Fe/C hollow microspheres composed of centripetal Fe/C nanosheets. Both of the interconnected channels created by multiple gaps among the adjacent Fe/C nanosheets and the hollow structure have positive effects on the absorbing performances by promoting the penetration of microwaves and acoustic waves and prolonging action time between microwave energy and acoustic energy with materials. In addition, a polymer-protection strategy and a high-temperature reduction process were applied to keep this unique morphology and further improve the performances of the composite. As a result, the optimized hierarchical Fe/C–500 hollow composite exhibits a wide effective absorption bandwidth of 7.52 GHz (10.48–18.00 GHz) at only 1.75 mm. Furthermore, the Fe/C–500 composite can effectively absorb sound wave in the frequency of 1209–3307 Hz, basically including part of the low frequency range (<2000 Hz) and most of the medium frequency range (2000–3500 Hz), and has 90% absorption of sound at 1721–1962 Hz. This work puts new insight into the engineering and development of microwave absorption–sound absorption-integrated functional materials with promising applications.

Gradient Hierarchical Hollow Heterostructures of Ti3C2Tx@rGO@MoS2 for Efficient Microwave Absorption

“…The booming development of electronic information technology has greatly improved the quality of human life, but it has also inevitably brought much unacceptable electromagnetic (EM) radiation. − These radiated electromagnetic waves (EMW) are harmful to human health and may cause the malfunction of electronic products. − As a consequence, there is an urgent need to explore advanced materials to effectively eliminate undesirable EM radiation. Microwave absorption (MA) materials can convert EM energy into thermal energy by interacting with EMW to reduce harmful radiation. − To achieve high performance, MA materials are required to possess good impedance matching and strong attenuation capability simultaneously. , Among them, good impedance matching allows more EMW to be incident inside materials instead of being reflected off the surface. , The strong attenuation capability means that the microwave absorbers can dissipate the EMW entering its interior to the greatest extent possible . Unfortunately, the design of microwave absorbers with both strong EM dissipation capacity and good impedance matching is usually challenging because these two characteristics are usually contradictory. − …”

Flexible, Stretchable, and Lightweight Hierarchical Carbon-Nanotube-Decorated Carbon Fiber Structures for Microwave Absorption

“…For this purpose, several high-performing EMA’s have been created in which carbon-based polymer composites are regarded as advantageous and promising candidates for highly efficient EMA with excellent thermal management capacities, lightweight, cost-effective, enhanced electric and heat conductivity, high dielectric loss, high mechanical stability, and excellent corrosion resistance. − However, the ability of the carbon nanofillers to agglomerate in the form of bundles results from the presence of powerful intermolecular van der Waals interaction, deteriorates the capabilities of carbon nanofillers for EM absorption, and restricts their applicability in industrial applications. , For this purpose, various techniques have recently been used to construct carbon-decorated hybrid morphologies consisting of magnetic or dielectric particles. − For example, Bao et al synthesized the bifunctional hollow Fe@C microsphere and fabricated the nanocomposite microwave absorber by mixing Fe@C (60 wt %) in paraffin, displaying a wide EAB of 7.52 GHz (10.48–18 GHz) at a 1.75 mm thickness . Gou et al made a 2.5 mm thickness nanocomposite consisting of polydimethylsiloxane (PDMS)/CeFe 2 O 4 /graphene oxide (GO) (60 wt %) in paraffin (40 wt %) and achieved the minimum R L value of −52 dB with an EAB of 2.1 GHz (Ku band) .…”

Rough‐Endoplasmic‐Reticulum‐Like Hierarchical Composite Structures for Efficient Mechanical‐Electromagnetic Wave‐Energy Attenuation

“…[ 6 ] Integrating these features to form wave‐energy attenuation materials is a big challenge, especially in a single intrinsic structure without the assistance of metamaterials, and relative research is rare. [ 7 ] Applying the decoupling strategy may be an effective option. [ 8 ] Specific to our work, this strategy attempts to enhance sound absorption through a certain method, while the electromagnetic absorption is barely affected by it, then effective wave‐energy attenuation may be conducted.…”

“…Compared with relative works, some researchers use microspheres as wave‐energy absorbers and solid rigid polymer as protection, which might tremendously jeopardize the sound absorption performance. [ 7 ] Meanwhile, other researchers apply a material array for electromagnetic absorption, which, like metamaterials, limits the design freedom in specific scenarios. [ 20 ] This work not only opens up a new avenue for harnessing nano‐carbon materials in sound wave absorption but also successfully manifests leading properties of wave attenuation in both mechanical and electromagnetic domains.…”