Hydro/Organo/Ionogels: “Controllable” Electromagnetic Wave Absorbers

Abstract

Demand for electromagnetic wave (EMW) absorbers continues to increase with technological advances in wearable electronics and military applications. In this study, a new strategy to overcome the drawbacks of current absorbers by employing the co‐contribution of functional polymer frameworks and liquids with strong EMW absorption properties is proposed. Strongly polar water, dimethyl sulfoxide/water mixtures, and highly conductive 1‐ethyl‐3‐methylimidazolium ethyl sulfate ([EMI][ES]) are immobilized in dielectrically inert polymer networks to form different classes of gels (hydrogels, organogels, and ionogels). These gels demonstrate a high correlation between their dielectric properties and polarity/ionic conductivity/non‐covalent interaction of immobilized liquids. Thus, the EMW absorption performances of the gels can be precisely tuned over a wide range due to the diversity and stability of the liquids. The prepared hydrogels show good shielding performance (shielding efficiency > 20 dB) due to the high dielectric constants, while organogels with moderate attenuation ability and impedance matching achieve full‐wave absorption in X‐band (8.2–12.4 GHz) at 2.5 ± 0.5 mm. The ionogels also offer a wide effective absorption bandwidth (10.79–16.38 GHz at 2.2 mm) via prominent ionic conduction loss. In short, this work provides a conceptually novel platform to develop high‐efficient, customizable, and low‐cost functional absorbers.

Reduced Graphene Oxide/Barium Ferrite Ceramic Nanocomposite Synergism for High EMI Wave Absorption

“…The attenuation constant is represented by the symbol (α) and expressed in decibels (dB). It is used to evaluate the integral loss ability, as expressed in eq α = 2 π f c ( false( μ ″ ε ″ − μ ′ ε ′ false) + false( μ ″ ε ″ − μ ′ ε ′ false) 2 + false( μ ′ ε ″ + μ ″ ε ′ false) 2 ) …”

“…The attenuation constant is represented by the symbol (α) and expressed in decibels (dB). It is used to evaluate the integral loss ability, as expressed in eq …”

Flexible and Ultrathin Graphene/Aramid Nanofiber Carbonizing Films with Nacre-like Structures for Heat-Conducting Electromagnetic Wave Shielding/Absorption

“…With the continuous promotion of portable/wearable electronic devices and electronic communication technologies, the development of efficient electromagnetic interference (EMI) shielding and electromagnetic wave absorption (EWA) materials is urgently needed to ensure the stable performance of electronic devices and protect human health. − Consequently, much effort has been made on developing novel EMI shielding or EWA materials and further enhancing their shielding and absorption capabilities by structural design and hybridization compounding. − In effect, multitudinous electromagnetic materials explored in recent years almost completely fulfill the performance demands and variations, whether shielding or absorption utility. − However, the booming evolution of integrated and miniaturized electronic devices, especially the rise of smart wearable electronics, has put forward some higher demands to EMI shielding and EWA materials. , Both the heat management property and flexibility have also become two indispensable important features that should be considered simultaneously in designing electromagnetic materials. − …”

Hierarchical Carbon Network Composites Derived from ZIF-8 for High-Efficiency Microwave Absorption

“…Microwave absorption materials (MAMs) have become important to address the problems of electromagnetic pollution and transmission signal attenuation in practical applications due to the rapid adoption of communications systems [1][2][3][4]. To date, concerted efforts have been devoted to designing heterogeneous MAMs, such as carbon-based materials [5][6][7][8], magnetic metals [9,10], and conductive polymers [11].…”