Broad Effective Absorption Bandwidth Research Articles

Multidimensional Engineering Induced Interfacial Polarization by in-Situ Confined Growth of MoS2 Nanosheets for Enhanced Microwave Absorption.

Interface design has enormous potential for the enhancement of interfacial polarization and microwave absorption properties. However, the construction of interfaces is always limited in components of a single dimension. Developing systematic strategies to customize multidimensional interfaces and fully utilize advantages of low-dimensional materials remains challenging. Two-dimensional transition metal dichalcogenides (TMDCs) have garnered significant attention owing to their distinctive electrical conductivity and exceptional interfacial effects. In this study, a series of hollow TMDCs@C fibers are synthesized via sacrificial template of CdS and confined growth of TMDCs embedded in the fibers. The complex permittivity of the hollow TMDCs@C fibers can be adjusted by tuning the content of CdS templates. Importantly, the multidimensional interfaces of the fibers contribute to elevating the microwave absorption performance. Among the hollow TMDCs@C fibers, the minimum reflection loss (RLmin) of the hollow MoS2@C fibers can reach -52.0dB at the thickness of 2.5mm, with a broad effective absorption bandwidth of 4.56GHz at 2.0mm. This work establishes an alternative approach for constructing multidimensional coupling interfaces and optimizing TMDCs as microwave absorption materials.

In situ encapsulation of heterostructures induced microscopic factors to enhance polarization loss of transition metal sulfides microwave absorbers

With the rapid development of modern electronic devices, electromagnetic wave pollution has become increasingly severe. In the field of materials science research, developing superior microwave absorbers holds immense importance. Light-weight carbon nanotube composites are developed for their unique electronic structure and excellent mechanical properties for wide applications in electronics, communication devices, and other specific parts, considering ideal candidates for the preparation of new types of electromagnetic wave absorption materials. This study focuses on embedding Fe7S8/FeS2 heterostructures into nitrogen doped carbon nanotubes through in-situ packaging to optimize interface engineering and improve the electromagnetic wave absorption efficiency of the material. Through pyrolysis and sulfidation processes, we successfully synthesized Fe7S8/FeS2 heterostructures in situ encapsulated within N-doped carbon nanotubes (NCNTs). Fe7S8/FeS2/NCNT shows microwave absorbing ability with a strong absorption (−36.83 dB at 14.08 GHz with a small thickness of 1.6 mm) and a broad effective absorption bandwidth (5.14 GHz). The excellent microwave absorption capability is mainly attributed to the efficient conductive network of NCNTs and the synergistic effect of Fe7S8/FeS2 heterostructures. This not only confirms the potential of transition metal sulfides/NCNTs composites in microwave attenuation applications, but also provides new strategies for the design and development of future microwave absorbers.

Fabrication of 3D micro-flower structured BiFeO3 growing on rGO nanosheets for enhanced electromagnetic wave absorption

Because of the distinctive structure and superior properties of graphene and its derivatives, which have been widely studied in the field of electromagnetic wave (EMW) absorption. However, the impedance mismatch caused by excessive conductivity of graphene and the single loss mechanism greatly limit its application. Herein, we prepare 3D micro-flower structured BiFeO3 grown on graphene oxide nanosheets (BiFeO3-rGO) to both improve the impedance matching and introduce abundant interfacial polarization loss. Moreover, the electromagnetic parameters of the materials are adjusted by changing the ratio of BiFeO3 and rGO to obtain prominent EMW absorption and satisfactory impedance matching performances. More importantly, the conductive loss and polarization loss of the materials are quantitatively analyzed to further explore the loss mechanism of EMW. As a result, the fabricated BiFeO3-rGO 1:1 and BiFeO3-rGO 2:1 both achieve remarkable EMW absorption performances with strong reflection loss (RL) of −49.5 and −45.3 dB and broad effective absorption bandwidth (EAB) of 8.12 and 8.08 GHz with a low filling contents of 5 %. This work demonstrates that polarization loss is as important as conduction loss and the key point to further improve the EMW absorption performance is to crack the code of polarization loss.

Bidirectional, Multilayer MXene/Polyimide Aerogels for Ultra-Broadband Microwave Absorption.

To obtain high-performance electromagnetic microwave (EM) absorption materials with broad effective absorption bandwidth (EAB) and reduced thickness, designing structures has proved to be a promising way. Herein, ultra-broadband multilayer bidirectional MXene/polyimide EM absorption aerogels containing multi-structures on scales ranging from the micro- to the macroscale are produced with the aid of electric and temperature fields. On the microscale, under the action of electric force and temperature gradient, the ordered structures made of aligned Ti3C2Tx MXene nanosheets and the microscale layered aerogel walls enable the bidirectional aerogel to achieve a wide EAB of 8.58GHz at a thickness of 2.1mm. This is ascribed to the numerous aligned nanosheets and layered aerogel walls perpendicular to the incident EMs, facilitating the conversion of electromagnetic energy into electrical energy. Furthermore, on the macroscale, the multilayer bidirectional aerogel with non-gradient structures effectively resolves the conflict between impedance matching and energy loss, resulting in an ultrawide EAB of 9.41GHz at a thickness of 3mm. This innovative design of electric-field-assisted multilayer bidirectional aerogels with multiscale structural coupling may provide feasible and effective pathways for the development of advanced EM absorption materials.

One‐Pot Synthesis of Conductive Metal–Organic Framework@polypyrrole Hybrids with Enhanced Electromagnetic Wave Absorption Performance

Rational heterostructure design can bring interfacial polarization relaxation to significantly enhance the electromagnetic wave (EMW) absorption performance. However, intelligently building a homogeneous heterostructure with superior EMW absorption properties remains a great challenge. Herein, a typical conductive metal–organic framework Cu3(HHTP)2 (hexahydroxytriphenylene, HHTP) is delicately packed onto a polypyrrole (PPy) conductive polymer surface via a one‐step in situ polymerization approach. Results show that Cu3(HHTP)2 is well packed on the PPy surface to form an elegant Cu3(HHTP)2@PPy hybrids interfacial microstructure with a unique superiority regarding EMW absorption compared with single components of PPy and Cu3(HHTP)2. Interestingly, the interfacial microstructure of Cu3(HHTP)2@PPy hybrids can be tuned by adjusting the composition of the PPy and Cu3(HHTP)2, resulting in the improvement of impedance matching, conductive loss, and enhancement of interfacial polarization relaxation, endowing the optimization of the EM wave absorption properties of the Cu3(HHTP)2@PPy. The broad effective absorption bandwidth covers a range as broad as 6.68 GHz (11.00–17.68 GHz), which is higher than most reported metal‐organic frameworks (MOFs) and conductive polymer‐based EM absorbing materials. Herein, new insight for developing highly efficient EMW absorption materials through hybridized interfacial microstructure engineering is provided.

Ultralight Hierarchical Fe3O4/MoS2/rGO/Ti3C2Tx MXene Composite Aerogels for High-Efficiency Electromagnetic Wave Absorption.

Aerogel-based composites, renowned for their three-dimensional (3D) network architecture, are gaining increasing attention as lightweight electromagnetic (EM) wave absorbers. However, attaining high reflection loss, broad effective absorption bandwidth (EAB), and ultrathin thickness concurrently presents a formidable challenge, owing to the stringent demands for precise structural regulation and incorporation of magnetic/dielectric multicomponents with synergistic loss mechanisms within the 3D networks. In this study, we successfully synthesized a 3D hierarchical porous Fe3O4/MoS2/rGO/Ti3C2Tx MXene (FMGM) composite aerogel via directional freezing and subsequent heat treatment processes. Owing to their ingenious structure and multicomponent design, the FMGM aerogels, featured with abundant heterogeneous interface structure and magnetic/dielectric synergism, show exceptional impedance matching characteristics and diverse EM wave absorption mechanisms. After optimization, the prepared ultralight (6.4 mg cm-3) FMGM-2 aerogel exhibits outstanding EM wave absorption performance, achieving a minimal reflection loss of -66.92 dB at a thickness of 3.61 mm and an EAB of 6.08 GHz corresponding to the thickness of 2.3 mm, outperforming most of the previously reported aerogel-based absorbing materials. This research presents an effective strategy for fabricating lightweight, ultrathin, highly efficient, and broad band EM wave absorption materials.

Non-uniform polarization boosted electromagnetic wave absorption with high efficiency and a broad frequency range

3-Aminobenzene sulfonic acid (mASA) has been co-polymerized into polyaniline (PANI) surface layers of ferrite nano particles by oxidative polymerization method. The sulfonic group of mASA anchored into PANI molecular have been employed as a dopant of PANI to partially substitute the dissociative dopant, hydrochloric acid (HCl). Owing to the constrained local distribution of mASA in PANI, the non-uniform polarization of PANI has been successfully stimulated by sulfonic acid doping. This results in various scattering loss modes and refined impedance matching in the synthesized ferrite/PANI nano-composite, which contributes to excellent absorbing properties with a high reflection loss of −56.42 dB and a broad effective absorption bandwidth of 3.8 GHz. The exhibited performances in microwave absorption are superior to most of ferrite-related composites. The explored strategy provides a novel way to tailor microwave absorbing composites to enhance their comprehensive microwave absorbing properties.

Hollow engineering of Co/N-doped C@carbon aerogel with hierarchical structure boosting interfacial polarization for ultra-thin microwave absorption and thermal insulation

Rational manipulation of the composition and microstructure design of aerogel materials is considered to be an effective method for achieving the dual functions of microwave absorption and thermal insulation. Herein, hollow Co/N-doped C@carbon aerogel with hierarchical structures was designed and constructed via a synergistic strategy including directed freeze-drying, ZIF-67 in situ growth, chemical etching and calcination treatment. Co/N-doped hollow carbon nanocages derived from ZIF-67 with uniform heterojunctions and layered micro-mesopores were constructed using tannic acid and heat treatment process. After that, abundant macroporous structure from the carbon aerogel itself was further introduced to upgrade the impedance matching property, light weight and interfacial polarization loss capability. Remarkably, as-fabricated Co/N-doped C@carbon aerogel (ZTA@A-900) displays optimal MA performance with a minimum reflection loss (RLmin) value of −54.0 dB at 15.32 GHz and a broad effective absorption bandwidth (EAB) of 4.04 GHz (13.44–17.48 GHz) at a thickness of only 1.4 mm. Furthermore, the ideal CST simulation results and excellent thermal insulation property of ZTA@A-900 make it an outstanding candidate for microwave absorbers under extreme conditions. Thus, our work opens up a new avenue for the design and fabrication of multifunctional lightweight microwave absorbers.

Size-progressively-reduced FeCoNi@C nanoparticles spatially confined within polypyrrole-derived hollow carbon nanoboxes against electromagnetic contamination

Pyrolytic prussian blue analogues (PBAs) are usually faced with serious agglomeration problem, which restrains their application in the field of microwave absorption to some extent. Given that polymer-based encapsulating layer is propitious for resolving the above issue, herein, with the assistance of polypyrrole (Ppy), a series of carbon-coated FeCoNi alloy nanoparticles (FeCoNi@C) spatially confined within hollow carbon nanoboxes (HCNB) are successfully fabricated using FeCoNi PBAs@Ppy with core–shell structure as the precursors. By quantitatively manipulating the thickness of Ppy encapsulating layer, it is found that there exists a competitive correlation between two kinds of forces with opposite directions under high-temperature inert atmosphere, eventually resulting in distinguishable differences in the configurations of derivatives. Specifically, if the thermal-induced inward contraction (FC) of the inner FeCoNi PBAs core is stronger than the heterointerface interaction (FI) provided by interfacial carbon layer derived from the outer Ppy shell, the derivative will exhibit yolk-shell microstructure, and otherwise, the architecture with hollow configuration can be created. When the thickness of Ppy encapsulating layer is optimized, the resultant yolk-shell sample with moderate Ppy-derived carbon content (ca. 32.6 wt%) delivers a broad maximum effective absorption bandwidth (EAB) value of 5.8 GHz and a desirable minimum reflection loss (RL) intensity of − 52.4 dB, which mainly benefit from its eligible impedance matching characteristic and the synergistic effect of dielectric and magnetic losses. It is believed that this work will enrich the pertinent researches about microwave absorbing materials (MAMs) with outstanding performance derived from polymer-encapsulated PBAs.

A wood-inspired epoxy-based electronic packaging material with vertically aligned thermally conductive channels for electromagnetic waves absorption and thermal management

Multifunctional materials integrating electromagnetic waves absorption (EMA) and heat conductivity functions are urgently desirable to tackle the heat emission and electromagnetic interference issues of advanced electronics. However, simultaneously mustering these features into one material remains a formidable challenge as the incompatibility between high thermal conductivity and excellent EMA performance. Herein, inspired by the water transport process of trees in nature, an epoxy-based electronic packaging material (CFS/EB) with vertical thermal conduction channels is fabricated by encapsulating high thermal conductivity boron nitride/epoxy hybrids into aerogel skeleton with good electromagnetic features. This ingenious design not only can defuse the issue of difficult coexistence of outstanding EMA and thermal conduction performance, but also delivers high through-plane thermal conductivity arised from vertical aligned channels. The resulting CFS/EB composite exhibits strong EMA performance with minimum reflection loss value of −59.2 dB and broad effective absorption bandwidth of 5.82 GHz. Synchronously, the composite also holds the high through-plane thermal conductivity of 1.51 W m−1 K−1 (655 % higher than pure epoxy resin) at low filler loading of 13.15 wt% as well as electrical insulation of 1.43 × 1012 Ω·cm. Such a superior comprehensive performance endows CFS/EB composite a great application prospects in electronic packaging fields, whilst the orientation structure design triggered by this bioinspired strategy offer facile yet feasible alternatives to address heat accumulation and electromagnetic interference problems for integrated electronics.

The Synergistic Effect of Nitrogen-Doped Carbonized Kapok Fiber to Amorphous/Nanocrystalline Fe85 SiAl6 Cr8 for Broad Effective Absorption Bandwidth Microwave Absorber

With the increasing quantity of intelligent and portable electric devices, a broad effective absorption bandwidth (EAB) microwave absorber (MWA) is required for shielding microwave (MW) interference. An MWA with a magnetic-dielectric synergistic effect is necessary for broadening the EAB of it. The amorphous/nanocrystalline [Formula: see text]SiAl6Cr8 (FSAC) is a nanolevel high magnetic loss MWA, and the introduction of medium dielectric loss MWA nitrogen-doped carbonized kapok fiber (NCKF) with an appropriate proportion improved the impedance match and damping ability of the composite and broadened the EAB. The results revealed that the minimum reflection loss ([Formula: see text] of FSAC/NCKF was -22.5 dB at 16.8[Formula: see text]GHz with a thickness of 1.20[Formula: see text]mm, and the EAB was 4.91[Formula: see text]GHz with a thickness of 1.30[Formula: see text]mm. Besides, the EAB moved to the low-frequency range when the thickness increased. Meanwhile, the RL of the simulation and the experiment were remarkably similar. The strategy offers an approach for developing a MWA with broad EAB.

A Novel Nano-Laminated GdB2C2 with Excellent Electromagnetic Wave Absorption Performance and Ultra-High-Temperature Thermostability.

A novel nano-laminated GdB2C2 material was successfully synthesized using GdH2, B4C, and C via an in situ solid-state reaction approach for the first time. The formation process of GdB2C2 was revealed based on the microstructure and phase evolution investigation. Purity of 96.4 wt.% GdB2C2 was obtained at a low temperature of 1500 °C, while a nearly fully pure GdB2C2 could be obtained at a temperature over 1700 °C. The as-obtained GdB2C2 presented excellent thermal stability at a high temperature of 2100 °C in Ar atmosphere due to the stable framework formed by the high-covalence four-member and eight-member B-C rings in GdB2C2. The GdB2C2 material synthesized at 1500 °C demonstrated a remarkably low minimum reflection loss (RLmin) of -47.01 dB (3.44 mm) and a broad effective absorption bandwidth (EAB) of 1.76 GHz. The possible electromagnetic wave absorption (EMWA) mechanism could be ascribed to the nano-laminated structure and appropriate electrical conductivity, which facilitated good impedance matching, remarkable conduction loss, and interfacial polarization, along with the reflection and scattering of electromagnetic waves at multiple interfaces. The GdB2C2, with excellent EMWA performance as well as remarkable ultra-high-temperature thermal stability, could be a promising candidate for the application of EMWA materials in extreme ultra-high temperatures.

Plentiful heterogeneous interfaces coupling in hydrangea-like NiMn-LDH decorated MXene hybrids for enhancing electromagnetic wave absorption

Exploring high-performance electromagnetic wave (EMW) absorption materials holds extraordinary potential for new-generation wireless communication and integrated electronics. Herein, a series of heterogeneous hydrangea-like NiMn-layered double hydroxide (NiMn-LDH)/MXene (denoted as NMM) hybrids were successfully synthesized by facile hydrothermal method and followed electrostatic self-assembly strategy. The EMW absorption performance of NMM hybrids could be flexibly tuned by regulating the ratios of NiMn-LDH to MXene. Benefiting from the synergy of unique structural design and various EMW attenuation mechanisms, the resultant NMM hybrids realize excellent EMW absorption performance. The NMM3 hybrid (the ratio of NiMn-LDH to MXene is 1:1) achieves an optimal reflection loss of –47.7 dB at 13.29 GHz with a thickness of 1.68 mm and a broad effective absorption bandwidth of 4.4 GHz (13.6-18.0 GHz) at a tiny thickness of 1.43 mm. Moreover, the radar cross section simulation is used to intuitively reveal the effectiveness of NMM hybrids as high-performance EMW absorption materials in actual application. This work provides an innovative perspective on the controllable design of highly efficient EMW absorption materials with remarkably practical application value.

Surfactant-induced morphology engineering in chitosan-derived carbon aerogels realizing high-efficiency absorption of electromagnetic wave

Despite the significant research advances in dielectric loss-type absorbents, developing high-efficiency electromagnetic wave (EMW) absorbents dominated by the conduction loss are still challenging due to the imbalance between impedance matching and conduction loss. In this study, for the first time, high-efficiency EMW absorption governed by the conduction loss in chitosan-derived carbon aerogels was realized through surfactant-assisted morphology modification. Electrostatic interaction and hydrogen bonding between chitosan and surfactants were ingeniously applied to induce tightly-stacked nanosheets to transform into three-dimensional (3D) interwork structure and loosely-stacked porous nanosheets, respectively, and thus the moderately enhanced conductivity converted the original EMW-transparent carbon to EMW-absorbing carbon. Benefiting from the favorable balance of impedance matching and conduction loss, the carbon aerogels with 3D interwork structure showed a broad effective absorption bandwidth (EAB) of 7.2 GHz (2.8 mm) and minimum reflection loss (RLmin) of −42.6 dB; and moreover, an ultra-wide EAB of 7.84 GHz at 2.9 mm occurred in the samples with loosen and wrinkled nanosheet structure, both outperforming most of reported carbon-based composite aerogels. This work provides a new insight for the morphology regulation and performance optimization of carbonaceous EMW absorbents.

Integrating Sulfur Doping with a Multi-Heterointerface Fe7S8/NiS@C Composite for Wideband Microwave Absorption.

Heterointerface engineering is presently considered a valuable strategy for enhancing the microwave absorption (MA) properties of materials via compositional modification and structural design. In this study, a sulfur-doped multi-interfacial composite (Fe7S8/NiS@C) coated with NiFe-layered double hydroxides (LDHs) is successfully prepared using a hydrothermal method and post-high-temperature vulcanization. When assembled into twisted surfaces, the NiFe-LDH nanosheets exhibit porous morphologies, improving impedance matching, and microwave scattering. Sulfur doping in composites generates heterointerfaces, numerous sulfur vacancies, and lattice defects, which facilitate the polarization process to enhance MA. Owing to the controllable heterointerface design, the unique porous structure induced multiple heterointerfaces, numerous vacancies, and defects, endowing the Fe7S8/NiS@C composite with an enhanced MA capability. In particular, the minimum reflection loss (RLmin) value reached -58.1dB at 15.8GHz at a thickness of 2.1mm, and a broad effective absorption bandwidth (EAB) value of 7.3GHz is achieved at 2.5mm. Therefore, the Fe7S8/NiS@C composite exhibits remarkable potential as a high-efficiency MA material owing to the synergistic effects of the polarization processes, multiple scatterings, porous structures, and impedance matching.

Biomimetic artificial nacre-like microfiber of Co/C modified cellulose nanofiber/Ti3C2Tx MXene with efficient microwave absorption

Although considerable efforts have been made in the fabrication of MXene-based composites for microwave absorption (MA), there is a great challenge to assemble MXene into regularly arranged microfibers prepared by wet-spinning technique for application in the field of MA due to insufficient interlayer interactions between Ti3C2Tx flakes. Heterogeneous interface design by optimizing material components to construct ingenious microstructure is crucial for efficient microwave absorbers. Herein, artificial nacre-like supramolecular microfibers of Co/C modified cellulose nanofiber/Ti3C2Tx MXene (Co/C/CNF/Ti3C2Tx) with plenty of heterogeneous interfaces were prepared by a simple wet-spinning technology through a self-assembly process induced by hydrogen bonding interactions between CNF and Ti3C2Tx. The artificial nacre-like microfibers with layered structure possess abundant heterogeneous interfaces, which facilitate multiple reflections/scattering of electromagnetic waves (EMW) between these interfaces, and at the same time promote interfacial and dipole polarization. The introduction of magnetic Co/C nanoparticles not only offer additional magnetic loss ability and improved impedance matching, but also enhance conductivity loss and polarization loss. Benefiting from these advantages, Co/C/CNF/Ti3C2Tx (1:1:1) fiber exhibits superior MA performance with a minimum reflection loss (RLmin) of up to −62.32 dB (>99.9999 % energy absorption) and a broad effective absorption bandwidth (EAB) of 5.86 GHz. The work provides a promising method for the preparation of biomimetic artificial nacre-like MXene-based microfibers with efficient MA performance, which is expected to be applied in the field of flexible wearable electromagnetic protection.

Interfacial modulation of SiC/TiC hybrid nanofibers for fabricating flexible ceramic electromagnetic wave absorbers

Titanium Carbide (TiC), characterized by its hardness, conductivity and thermal stability, can serve as a suitable additive phase for SiC nanofibers. TiC phase can improve the flexibility and electromagnetic wave absorption property of SiC nanofibers without sacrificing its high-temperature thermal stability. Herein, flexible SiC/TiC hybrid nanofibers with different Ti contents were fabricated by electrospinning and precursor infiltration pyrolysis. The introduction of Ti can not only generate conductive TiC phase, but also act as a catalyst to regulate the growth of SiC grains, so as to adjust the flexibility and electromagnetic properties of the hybrid nanofibers. At the optimal Ti precursor content of 4 wt%, the SiC/TiC-4 hybrid nanofibers exhibit a broad effective absorption bandwidth of 4.5 GHz with the thickness of 1.6 mm. The flexible SiC/TiC hybrid nanofibers This work can provide a reference for the design of flexible ceramic nanofiber absorbers and is expected to enable practical application in high temperature conditions.

Ultralight Three-Layer Gradient-Structured MXene/ Reduced Graphene Oxide Composite Aerogels with Broadband Microwave Absorption and Dynamic Infrared Camouflage.

Infrared and radar detectors posed substantial challenges to weapon equipment and personnel due to their continuous surveillance and reconnaissance capabilities. Traditional single-band stealth devices are insufficient for dual-band detection in both infrared and microwave bands. To overcome this limitation, a gradient-structured MXene/reduced graphene oxide (rGO) composite aerogel (GMXrGA) is fabricated through a two-step bidirectional freeze casting process, followed by freeze-drying and thermal annealing. GMXrGAexhibits a distinct three-layered structure, with each layer playing a crucial role in microwave absorption. This deliberate design amplifies both the efficiency of microwave absorption and the material's effectiveness in dynamic infrared camouflage. GMXrGA displays an ultralow density of 5.2 mg∙cm-3 and demonstrates exceptional resistance to compression, enduring 200 cycles at a maximum strain of 80%. Moreover, it shows superior microwave absorption performance, with a minimum reflection loss (RLmin) of -60.1dB at a broad effective absorption bandwidth (EAB) of 14.1GHz (3.9-18.0GHz). Additionally, the aerogel exhibits low thermal conductivity (≈26 mW∙m-1∙K-1) and displays dynamic infrared camouflage capabilities within the temperature range of 50-120°C, achieving rapid concealment within 30 s. Consequently, they hold great potential for diverse applications, including intelligent buildings, wearable electronics, and weapon equipment.

Reversible Switching Between Microwave Absorption and EMI Shielding of VO2 Composite Foam.

Developing lightweight composite with reversible switching between microwave (MW) absorption and electromagnetic interference (EMI) shielding is promising yet remains highly challenging due to the completely inconsistent attenuation mechanism for electromagnetic (EM) radiation. Here, a lightweight vanadium dioxide/expanded polymer microsphere composites foam (VO2/EPM) is designed and fabricated with porous structures and 3D VO2 interconnection, which possesses reversible switching function between MW absorption and EMI shielding under thermal stimulation. The VO2/EPM exhibits MW absorption with a broad effective absorption bandwidth of 3.25GHz at room temperature (25 °C), while provides EMI shielding of 23.1dB at moderately high temperature (100 °C). This reversible switching performance relies on the porous structure and tunability of electrical conductivity, complex permittivity, and impedance matching, which are substantially induced by the convertible crystal structure and electronic structure of VO2. Finite element simulation is employed to qualitatively investigate the change in interaction between EM waves and VO2/EPM before and after the phase transition. Moreover, the application of VO2/EPM is demonstrated with a reversible switching function in controlling wireless transmission on/off, showcasing its excellent cycling stability. This kind of smart material with a reversible switching function shows great potential in next-generation electronic devices.

Multifunctional carbon aerogels loaded with pea-pod-like carbon nanotubes for outstanding electromagnetic wave absorption performance

Although ordered porous carbon materials (PCMs) have shown promising potential in the field of electromagnetic wave absorption (EWA), creating multifunctional PCMs with outstanding microwave absorption performance remains a significant challenge. Herein, ordered porous carbon aerogels loaded with pea-pod-like nitrogen-doped carbon nanotubes (CNTs) were fabricated via orientation freeze-drying followed by high-temperature pyrolysis. The optimized aerogel exhibits extraordinary EWA performance with a broad effective absorption bandwidth of 7.68 GHz and exceptionally strong absorption of −91.58 dB at a low filling ratio of only 3 wt%, which is the largest absorption strength among all known aerogels to date. The exceptional EWA performance is attributed to the synergistic effect of abundant loss mechanisms resulting from a unique pod-like structure in ordered porous carbon aerogel, where nitrogen-doped CNTs encapsulate magnetic alloy nanoparticles. Optimized aerogel exhibits superior compressive elasticity, thermal insulation, and light weight, laying the groundwork for designing practical next-generation EWA materials.