Electromagnetic (EM) wave absorbing materials play an increasingly important role in modern society for their multi‐functional in military stealth and incoming 5G smart era. Dielectric loss EM wave absorbers and underlying loss mechanism investigation are of great significance to unveil EM wave attenuation behaviors of materials and guide novel dielectric loss materials design. However, current researches focus more on materials synthesis rather than in‐depth mechanism study. Herein, comprehensive views toward dielectric loss mechanisms including interfacial polarization, dipolar polarization, conductive loss, and defect‐induced polarization are provided. Particularly, some misunderstandings and ambiguous concepts for each mechanism are highlighted. Besides, in‐depth dielectric loss study and novel dielectric loss mechanisms are emphasized. Moreover, new dielectric loss mechanism regulation strategies instead of regular components compositing are summarized to provide inspiring thoughts toward simple and effective EM wave attenuation behavior modulation.

Dielectric Loss Mechanism in Electromagnetic Wave Absorbing Materials

Electromagnetic (EM) absorbers play an increasingly essential role in electronic information age, even towards coming intelligent life. The remarkable merits of heterointerface engineering and its peculiar EM characteristics inject a fresh and infinite vitality to design high-efficiency and stimuli-responsive EM absorbers. However, there still exist huge challenges in understanding and reinforcing these interface effects from the micro and macro perspectives. Herein, the EM response mechanisms of interfacial effects are dissected in depth, and advanced characterization as well as theoretical techniques is highly focused on. Then, the representative optimization strategies are systematically discussed with an emphasis on component selection and structural design. More importantly, the most cutting-edge smart EM functional devices based on heterointerface engineering are reported as highlights. Finally, current challenges and concrete suggestion are proposed, and future perspectives on this promising field are predicted as well. This article is protected by copyright. All rights reserved.

Heterointerface Engineering in Electromagnetic Absorbers: New Insights and Opportunities

MXene nanomaterials stand out among 2D nanomaterials and have been extensively studied by researchers because of their unique layered structure, chemical diversity, and outstanding chemical and physical properties. In recent years, MXene materials have rapidly opened the market for electromagnetic interference shielding technology due to their excellent electromagnetic wave absorption (EMA) capability. However, so far, compared with the development of electromagnetic (EM) shielding technology, there is still much room for development in the construction of MXenes and the application of electromagnetic wave absorption. Herein, the construction strategies, electromagnetic wave conversion mechanism, and applications of MXenes materials are reviewed. Through meticulous material design and an interdisciplinary approach, 2D MXene materials are expected to become one of the smart tunable wave absorbers, and their application scenarios will also become broader.

2D MXene Nanomaterials: Synthesis, Mechanism, and Multifunctional Applications in Microwave Absorption

Two-dimensional nanomaterials for high-efficiency electromagnetic wave absorption: An overview of recent advances and prospects

The recent progress of MXene-Based microwave absorption materials

Intelligent microwave absorption (MA) materials possess the ability to dynamically change their microwave absorption performance, according to real‐time requirements, and it is of great significance in future civil and military fields. For the first time, the reduced graphene oxide/VO2 composite aerogels are developed with off/on switchable MA performance, and the switchable mechanism is originated from the unique phase change behavior of VO2. As temperature increases (>68 °C), the VO2 displays the phase change from monoclinic to rutile phase, which accompanies with significant changes in aerogel's electrical conductivity as well as its permittivity, and consequently leads to off/on switchable MA performance. Particularly, two different off/on switch modes, “on to off” and “off to on”, can be separately realized by different composite aerogels as temperature increases, and this off/on switchable MA performance is also confirmed with good cycling stability. More importantly, during the off/on switch process, the maximum changes for the effective absorption bands (ΔEAB) and RL values (ΔRL) can be as high as 7.27 GHz and 49 dB, which exceeds most current reports. Besides, the RCS simulations on aircrafts have been performed and verified this intelligent MA performance, thus providing useful guidance for next‐generation smart electromagnetic devices in various fields.

Intelligent Off/On Switchable Microwave Absorption Performance of Reduced Graphene Oxide/VO2 Composite Aerogel

Hierarchical surface engineering of carbon fiber for enhanced composites interfacial properties and microwave absorption performance

Multifunctional graphene/carbon fiber aerogels toward compatible electromagnetic wave absorption and shielding in gigahertz and terahertz bands with optimized radar cross section

High-performance electromagnetic wave-absorbing (EMA) materials used in high-temperature environments are of great importance in both civil and military fields. Herein, we have developed the ultralight graphene/polyaramid composite foam for wideband electromagnetic wave absorption in both gigahertz and terahertz bands, with a higher service temperature of 300 °C. It is found that strong interfacial π-π interactions are spontaneously constructed between graphene and polyaramids (PA), during the foam preparation process. This endows the foam with two advantages for its EMA performance. First, the π-π interactions trigger the interfacial polarization for enhanced microwave dissipation, as confirmed by the experimental and simulation results. The composite foam with an ultralow density (0.0038 g/cm3) shows a minimum reflection loss (RL) of -36.5 dB and an effective absorption bandwidth (EAB) of 8.4 GHz between 2 and 18 GHz band. Meanwhile, excellent terahertz (THz) absorption is also achieved, with EAB covering the entire 0.2-1.6 THz range. Second, the interfacial π-π interactions promote PA to present a unique in-plane orientation configuration along the graphene surface, thus making PA the effective antioxidation barrier layer for graphene at high temperatures. The EMA performance of the foam could be completely preserved after 300 °C treatment in air atmosphere. Furthermore, the composite foam exhibits multifunctions, including good compressive, thermal insulating, and flame-retardant properties. We believe that this study could provide useful guidance for the design of next-generation EMA materials used in harsh environments.

Interfacial π-π Interactions Induced Ultralight, 300 °C-Stable, Wideband Graphene/Polyaramid Foam for Electromagnetic Wave Absorption in Both Gigahertz and Terahertz Bands.

Yishu Cao

Papers

The recent progress of MXene-Based microwave absorption materials

Intelligent Off/On Switchable Microwave Absorption Performance of Reduced Graphene Oxide/VO2 Composite Aerogel

Hierarchical surface engineering of carbon fiber for enhanced composites interfacial properties and microwave absorption performance

Multifunctional graphene/carbon fiber aerogels toward compatible electromagnetic wave absorption and shielding in gigahertz and terahertz bands with optimized radar cross section

Interfacial π-π Interactions Induced Ultralight, 300 °C-Stable, Wideband Graphene/Polyaramid Foam for Electromagnetic Wave Absorption in Both Gigahertz and Terahertz Bands.