Research on Efficient Electromagnetic Shielding Performance and Modulation Mechanism of Aero/Organo/Hydrogels with Gravity‐Induced Asymmetric Gradient Structure

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-12, Vol.20 (51), p.e2403210-n/a
• Main Authors: He, Man, Lv, Xuelian, Li, Zhonghui, Li, Haoyuan, Qian, Wen, Zhu, Shengyin, Zhou, Yuming, Wang, Yongjuan, Bu, Xiaohai
• Format: Article
• Language: English
• Subjects: aerogel; Asymmetry; Cellulose fibers; Composite materials; Concentration gradient; Effectiveness; electromagnetic interference shielding; Electromagnetic radiation; Electromagnetic shielding; Fillers; Glycerol-Water; hydrogel; Hydrogels; liquid metal; Liquid metals; Microwave absorption; Modulation; organogel; Polyvinyl alcohol; Reflectance; Wave reflection
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202403210

To eliminate electromagnetic pollution, it is a challenging task to develop highly efficient electromagnetic shielding materials that integrate microwave absorption (MA) performance with high shielding capability and achieve tunability in shielding performance. Asymmetrically structured aero/organo/hydrogels with a progressively changing concentration gradient of liquid metal nanoparticles (LMNPs), induced by gravity, are prepared by integrating the conductive fillers Ti3C2Tx MXene and LMNPs into a dual‐network structure composed of polyvinyl alcohol and cellulose nanofibers. Benefiting from the unique structure, which facilitates the absorption‐reflection‐reabsorption process of electromagnetic waves along with conductive fillers and the porous structure, three types of gels demonstrate efficient shielding performance. HPCML achieves a total shielding effectiveness (SET) of up to 86.9 dB and a reflection shielding effectiveness (SER) of as low as 2.85 dB. Especially, APCML, with an ultra‐low reflection coefficient (R) of 6.4%, achieves compatibility between shielding performance and MA properties. The relationship between dispersing media (air, water, and glycerol/water) and the shielding performance of aero/organo/hydrogels is explored, thereby achieving modulation of the shielding performance of the gel system. The work has paved a clear path for integrating absorption and shielding capabilities into a composite material, thereby providing a prototype of a highly efficient shielding material with MA performance. Asymmetric aero/hydro/organogels with a concentration gradient are constructed via gravity‐induced sedimentation of LMNPs. Benefiting from their unique structure, the three gels exhibit ultra‐high shielding performance (SET ≥ 71.1 dB) characterized by the absorption‐reflection‐reabsorption of electromagnetic waves. Among them, APCML aerogel, with a low reflection coefficient (R = 6.4%), achieves a favorable combination of effective shielding and microwave absorption performance.