Carbon Nanocoils/Carbon Foam as the Dynamically Frequency‐Tunable Microwave Absorbers with an Ultrawide Tuning Range and Absorption Bandwidth

Abstract

The absorption frequency of conventional microwave absorbing materials (MAMs) is hardly tuned in operando, while such dynamic frequency regulation of MAMs is of great significance to meet the high demands of modern radars and intelligent electron devices. Here, an ingenious frequency-tuning strategy by means of the pressure variations is developed by fabricating highly compressible carbon nanocoils/carbon foam (CNCs/CF) as a dynamically frequency-tunable microwave absorber. Through adjusting the compression strain, the absorption bandwidth of CNCs/CF can be precisely tuned from S-band (2−4 GHz) to Ku-band (12−18 GHz). The adjustable effective absorption bandwidth is as wide as 15.4 GHz, which covers 96% of the entire microwave frequency. Under 10% compression strain, CNCs/ CF shows an attractive bandwidth of 9.0 GHz and a strong reflection loss of −64.6 dB. Furthermore, the CNCs/CF also exhibit a good thermal insulation, strong hydrophobicity, and strain-sensitive conductivity, endowing them with fascinating functions of heat insulation and self-cleaning. The method of utilizing an external pressure to dynamically adjust the absorption frequencies of CNCs/CF is demonstrated for the first time, which opens an avenue for the applications of dynamically frequency-tunable MAMs with an ultrawide adjusting range and absorption bandwidth.

Indium tin oxide as a dual-band compatible stealth material with low infrared emissivity and strong microwave absorption

“…The m 0 and m 00 values of all the ITO samples are around 1 and 0, indicating that the magnetic loss capabilities of the ITO samples are negligible. 33,34 Fig. S4 (ESI †) depicts the dielectric loss tangent (tan d e = e 00 /e 0 ) and the magnetic loss tangent (tan d m = m 00 /m 0 ), which represent the dielectric and magnetic loss capacities, respectively.…”

Optimizing impedance matching and interfacial characteristics of aromatic polyimide/graphene by molecular layer deposition for heat-conducting microwave absorption

“…[1][2][3][4][5] Although substantial efforts have been devoted to improving reection loss (RL) and expanding bandwidth, MAMs still face severe limitations due to the complexity and severity of the practical application environment. [6][7][8][9][10][11] Notably, heat accumulation and dissipation issues resulting from high-power, high-density, and highly integrated electronic devices are becoming increasingly prominent. Long-standing overheating may result in thermal breakdown and damage the equipment directly or even lead to re incidents.…”

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. − …”