Electromagnetic Wave Absorption Research Articles

Durable superhydrophobic cotton fabrics with electromagnetic wave absorption based on MoS2/RGO composites

Durable superhydrophobic cotton fabrics with electromagnetic wave absorption based on MoS2/RGO composites

Hierarchical Engineering on Built‐In Electric Field of Bimetallic Zeolitic Imidazolate Derivatives Towards Amplified Dielectric Loss

AbstractConstruction of built‐in electric field (BIEF) in nanohybrids has been demonstrated as an efficacious strategy to boost the dielectric loss by facilitating oriented transfer and transition of charges, thus optimizing the electromagnetic wave absorption property. However, the specific influence of BIEF on interface polarization needs to explore thoroughly and the BIEF strength should be further augmented. Herein, several dielectric systems incorporated Mott–Schottky heterojunctions and hollow structures are designed and constructed, where bimetallic zeolitic imidazolate framework are employed to derive Cu‐ZnO Mott–Schottky heterojunctions, and hierarchical structures and BIEF are further enriched by introducing hollow structure and reduced graphene oxide. The well‐established “double” BIEF verified by theoretical calculation and hollow engineering can regulate the conductivity, and enhance the polarization relaxation effectively. Especially, there always coexisted both enhanced charge separation and reversed charge distribution in this “double” BIEF, boosting the interface polarization. Attributing to the synergy of well‐matched impedance and amplified dielectric loss, the obtained hybrids exhibited superior absorption (reflection loss of −46.29 dB and an ultra‐wide effective absorption bandwidth of 7.6 GHz at only 1.6 mm). This work proves an innovative model for dissecting dielectric loss mechanisms and pioneers a novel strategy to explore advanced absorbers through enhancing BIEF.

Defect introduction and interfacial strategies for enhancing microwave absorption in carbon-based materials

Poor impedance matching and a single loss mechanism are typical challenges for carbon-based materials to become efficient microwave absorbers. To address these issues, defect introduction and interfacial strategies are effective methods for enhancing microwave absorption through the micro-mechanism of material interaction with microwaves. Additionally, forming a homogeneous composite material is crucial for achieving good impedance matching. In this study, we used a controlled solvent-thermal method to achieve self-assembled interfacial intercalation, yielding amorphous VOPO4/rGO nanohybrids, which show significantly enhanced microwave absorption properties. The abundant defects introduced by VOPO4 within the amorphous layered composites disrupt the charge distribution, contributing to polarization loss. The graphene nanosheets expose more VOPO4 structural units, facilitating increased conductivity and enriching the microwave absorption mechanism. As a result, the prepared VOPO4/rGO nanohybrids demonstrate outstanding microwave absorption, with the effective absorption bandwidth covering the entire Ku-band (11.6–18.0 GHz) at a thickness of 2.3 mm. This research provides an important reference for understanding the mechanisms that enhance the electromagnetic wave absorption of carbon-based materials.

Upcycling Spent Graphite from Li-ion Batteries into Cu/Expanded Graphite Composites as high-performance electromagnetic wave absorbers.

With the widespread adoption of lithium-ion batteries and modern electronic components in both daily life and industrial production, there is a growing focus on the high-value recycling of spent lithium-ion batteries and the development of absorbents with high electromagnetic wave absorption capabilities. Efficiently regenerating recycling graphite from spent batteries through low-cost methods and utilizing it to prepare high-performance electromagnetic wave absorbing materials holds significant importance in addressing both the utilization of waste graphite and electromagnetic pollution issues simultaneously. This work presents a method to transform spent graphite into expanded graphite with a three-dimensional conductive structure using an enhanced Hummer's treatment and thermal reduction process. Subsequently, Cu/EG composite materials were efficiently prepared through straightforward mechanical ball milling and calcination. The unique honeycomb-like porous structure of expanded graphite facilitates the reflection and scattering of electromagnetic waves, electron transfer, and defect polarization. Additionally, the incorporation of copper nanoparticles improves the conduction loss and enhances interface polarization, allowing for precise tuning of the composite material's absorption performance. The results demonstrate that Cu/EG composite materials exhibit excellent electromagnetic wave absorption performance. The Cu/EG(1:3) sample exhibits effective absorption in the C, X, and Ku bands, achieving a minimum reflection loss (RLmin) of -54 dB and a maximum effective absorption bandwidth (EABmax) of 5.28 GHz. This performance is attained with a thickness of just 2.2 mm and a filler content of only 15 wt.%.

Self-assembly core–shell hollow fly ash sphere-bridged Ti3C2Tx MXene 3D spherical/ lamellar composites with specific electromagnetic wave absorption performance

A new A/B spherical/lamellar electromagnetic wave absorption (EWA) model was established, in which A phase was a spherical material with low dielectric constant and B phase was a lamellar 2D material with high dielectric constant. Insulative fly ash cenospheres (FA) and conductive Ti3C2Tx flakes were selected as the A phase and the B phase which acted as the framework (as well as core) and the interface builder (as well as shell) respectively to construct the novel 3D connected structure system via simple self-assembly. FA, a cheap power plants solid waste, was used as an insulating bridge for Ti3C2Tx to help to adjust the conductivity, the electromagnetic parameters and the impedance matching. The synergistic effect of the special heterogeneous structures and the moderate composition of FA and Ti3C2Tx endowed the composites with controllable complex permittivity and excellent EWA performances. FA@T0.35 exhibited a RLmin of − 50.94 dB at 3.5 mm and its widest EAB was 4.25 GHz at 2.0 mm. FA@T0.40 reached a RLmin of − 45.13 dB with an EAB of 4.03 GHz at 2.0 mm. The widest EAB was 4.19 GHz at only 1.5 mm. The work offers a new guideline for designing a high-performance EWA material by using waste materials.

Construction of a Borophene-Based Hybrid Aerogel for Multifunctional Applications.

As a novel approach to pursue high-performance multifunctional materials, the structural design of cutting-edge two-dimensional (2D) materials has ignited substantial interests. Borophene, an emerging member in the realm of 2D materials, exhibits crucial attributes, including high theoretical carrier density, electrical conductivity, magnetism, and high aspect ratio, rendering it highly promising for diverse applications. Yet, the exploration of porous structural configurations of borophene remains untapped. Addressing this gap, our study focuses on the fabrication of a multifunctional borophene hybrid foam (CMB-foam). This hybridization leverages the exceptional multifunctionality of MXene alongside borophene within a three-dimensional porous framework, facilitating reflection and absorption of electromagnetic waves, thereby demonstrating remarkable electromagnetic interference (EMI) shielding capabilities. Moreover, this structural configuration exposes an enlarged surface area, thus shortening the transport pathway for electrolyte ions, leading to an excellent energy storage performance. Additionally, CMB-foam performs well in thermal management and thermal insulation. These findings underscore the potential of borophene-based materials in multifunctional applications and offer valuable insights into further performance explorations in this domain.

Biomimetic Multi-Interface Design of Raspberry-like Absorbent: Gd-doped FeNi3@Covalent Organic Framework Derivatives for Efficient Electromagnetic Attenuation.

Structural design and interface regulation are useful strategies for achieving strong electromagnetic wave absorption (EMWA) and broad effective absorption bandwidth (EAB). Herein, a monomer-mediated strategy is employed to control the growth of covalent organic framework (COF) wrapping flower-shaped Gd-doped FeNi3 (GFN), and a novel raspberry-like absorbent based on biomimetic design is fabricated by thermal catalysis. Further, a unique dielectric-magnetic synergistic system is constructed by utilizing the COF-derived nitrogen-doped porous carbon (NPC) as the shell and anisotropic GFN as the core. The electromagnetic parameters of the GFN@NPC composites can be tuned by adjusting the proportions of GFN and NPC. Off-axis electron holography results further clarify the interface polarization and microscale magnetic interactions affecting the EMW loss mechanism. As a result, the GFN@NPC samples exhibit broad EMWA performance. The EAB values of all GFN@NPC composites reach up to 6.0 GHz, with the GFN@NPC-2 sample showing a minimum reflection loss (RLmin) of -69.6 dB at 1.68 mm. In addition, GFN@NPC-2 achieves a maximum radar cross-section (RCS) reduction of 29.75 dB·m2. A multi-layer gradient structure is also constructed using metamaterial simulation to achieve an ultra-wide EAB of 12.24 GHz. Overall, this work provides a novel bio-inspired design strategy to develop high-performance EMWA materials.

Self-assembly Ti3C2Tx MXene/ZnCo2O4@ZnO heterostructure with Schottky junction for regulating BIEF to enhance microwave absorption

Currently, heterogenous interface engineering on absorbers is shown to boost the electromagnetic wave absorption (EMA) performance effectively. However, challenges remain in investigating the mechanisms by studying heterojunctions between heterogeneous interfaces. Herein, a self-assembly Ti3C2Tx MXene/ZnCo2O4@ZnO (MZCZ) heterostructure with abundant Schottky heterogenous interfaces generating a controllable built-interface electric field (BIEF) effect is fabricated to achieve exceptional EMA ability. The formative BIEF between the unbalanced distribution charges promotes charge separation and migration, increasing polarization loss. Fortunately, the obtained MZCZ1 exhibits the reflection loss (RL) value of −69.78 dB under the ultralow thickness of 1.501 mm and the optimal minimum RL (RLmin) value of −74.41 dB, respectively. The excellent performance can be ascribed to the multiple polarization loss, conduction loss, natural resonance, and exchange resonance characteristics. Moreover, by the Computer Simulation Technology (CST) software, the designed circular cone and circular truncated cone periodicity structure with the MZCZ1 absorber both exhibit a super-wide effective absorption bandwidth (EAB) covering the whole C, X, and Ku band. This study can pioneer a novel approach to developing functional EMA materials and provide a valuable direction for further study of EMA mechanisms at heterogeneous interfaces.

Fabrication of hexagonal platelets of Fe3O4/Fe2O3/C modified with polyacrylamide for excellent electromagnetic wave absorption

In order to improve the weak dielectric loss capability and poor impedance matching of Fe3O4, the hexagonal plates of Fe3O4/Fe2O3/C nanocomposites were rationally constructed in this paper by utilizing electrostatic attraction and cross-linking, using polyacrylamide (PAM) as templating agent and viscosity modifier. The stacked hexagonal plates constructed a conductive network and utilized the structural properties of Fe3O4 to promote the transfer and jump of free electrons, which effectively improved the conduction loss. The heterogeneous interface was effectively constructed due to the presence of Fe2O3 and trace carbon, while the transfer and leap of free electrons promoted the generation of interfacial polarization, resulting in magnetoelectric coupling and effective improvement of polarization loss. The results show that the effective absorption broadband reaches 4.08 GHz when the matching thickness of the composite is 2 mm. A minimum reflection loss of −43.79 dB is realized at a matching thickness of 1 mm. The PAM modification proved to be an effective means to modulate the morphology and composition of the materials.

Structural modification of mesoporous lanthanum oxide into 3D coral-like and nano needle-like structure for effective broadband microwave absorbing materials☆

Structural modification of three dimensional (3D) materials for the application of dielectric loss-based microwave absorbing materials (MAMs) usually relies on intricate synthesis process and can pose challenges in terms of scalability and mass production for practical application. In this work, we reported a successful attempt in modifying the 3D structure of mesoporous lanthanum oxide (La2O3) for effective broadband MAMs candidate via simple co-precipitation process. The inclusion of cetyl-trimethylammonium bromide (CTAB) and hydrothermal aging treatment result in a significant transformation of La2O3 particles from their original polygonal form to a 3D coral-like and nano needle-like structure. The utilization of CTAB and hydrothermal aging results in the increase of surface area and a two-fold increase in pore volume of the resulting La2O3. Due to its unique 3D structure, the 3D coral-like and nano needle-like La2O3 materials possess a broadband electromagnetic (EM) wave absorption characteristic with the effective absorption bandwidth (EAB) covering the C-band frequency range. Specifically, in the La2O3 C-H sample (with CTAB – with hydrothermal), it exhibits strong EM wave absorption with a reflection loss (RL) value of –33.07 dB which equals to 99.95% EM wave absorption at a thickness of only 1.50 mm. The detailed analysis of EM wave absorption properties reveals that the improvement of La2O3 materials to attenuate EM wave energy arises from the dielectric loss phenomenon, the enhanced interfacial polarization, multiple reflections mechanism, and conduction loss mechanism induced by the 3D structural formation of the La2O3 structure. This work proposes a novel and efficient approach in synthesizing and modifying 3D materials for effective broadband EM wave absorption.

Thermally insulated C/SiC/SiBCN composite ceramic aerogel with enhanced electromagnetic wave absorption performance

Thermal insulation and electromagnetic wave (EMW) absorption integrated materials with lightweight are highly desirable in hypersonic vehicles and military application, as they provide both aerodynamic heat resistance and EMW stealth capability. Herein, a C/SiC/SiBCN ceramic composite aerogel was developed using a novel strategy combining in situ chemical vapor deposition of SiC nanofibers with the polymer-derived ceramic (PDC) aerogel method. The microstructure, phase composition, thermal insulation, mechanical properties and EMW absorption performances of the composite aerogel were thoroughly investigated. The resulting C/SiC/SiBCN composite aerogel with three impregnation-pyrolysis cycles demonstrates improved mechanical properties, with the compressive strength increasing from 0.21 MPa to 0.48 MPa compared to pure SiBCN aerogel. Additionally, the composite aerogel shows a low thermal conductivity of 0.049 W/mK and a low density of 0.116 g/cm3. Moreover, the C/SiC/SiBCN composite aerogel exhibits outstanding EMW absorption properties, achieving a minimum reflection loss of -45.7 dB and an effective bandwidth of 5.3 GHz. Owing to the integration of EMW absorption and thermal insulation properties, the C/SiC/SiBCN composite aerogel offers promising potential for developing integrated microwave absorption and thermal insulation materials for high-speed vehicles.

MOFs-derived copper selenides nanoparticles implanted in carbon matrix for broadband electromagnetic wave absorption

Selenide-based functional composites materials demonstrated tunable dielectric properties and heterogeneous interface design, which has been widely studied in electromagnetic (EM) wave absorption field. Herein, Metal-organic frameworks (MOFs) derived carbon coating copper selenide (Cu2-XSe@C) composites were successfully fabricated by using the Cu-MOFs as precursor. After reacting with the gaseous Se in the selenization annealing process, the metal host was converted into the Cu2-XSe nanoparticles, where embodied in the carbon matrix transformed from the organic linker. Based on the tunning dielectric property and building heterogeneous interface, MOFs-derived Cu2-XSe@C composites displayed outstanding EM wave absorption performance. Though the conduction loss, interfacial and dipole polarization behaviors, the minimum reflection loss (RLmin) value of Cu2-XSe@C-600 composites reached to −74.3 dB at 11.7 GHz when the thickness is 2.0 mm. The efficient absorption bandwidth (EAB) can be regulated via controlling the applied thickness. When the thickness is 2.3 mm, above-mentioned Cu2-XSe@C-600 got the broadest absorption performance with the EAB of 5.5 GHz from the 7.7–13.2 GHz, covering the whole X-band. Therefore, MOFs-derived selenide-based composites shed a new design strategy for constructing broadband EM wave absorption, especially in radar stealth applications.

Construction of 2D/2D heterostructure with porous few layer g-C3N4 and NiCo2O4 nanosheets towards electromagnetic wave absorption

Developing high-performance materials with ultra-high reflection loss (RL ≤ -65 dB) for electromagnetic wave (EMW) absorption is pivotal to address electromagnetic pollution, but it is still challenging. Herein, a two-dimensional (2D)/2D PFL g-C3N4/NiCo2O4 heterostructure with porous few-layer g-C3N4 (PFL g-C3N4) and ultrathin NiCo2O4 nanosheets has been prepared by self-assembly, hydrothermal reaction, and calcination strategies. The 2D/2D heterostructure exhibits extraordinary EMW absorption property, achieving a reflection loss (RL) value of -68.59 dB and an effective absorption bandwidth (EAB) of 1.92 GHz at a matching thickness of 2.5 mm. As expected, the porous few layer g-C3N4 nanosheets provide rich interface which increases multiple reflection paths and enhances the conduction loss. The cooperative effects of magnetic loss, dielectric loss, and impedance matching contribute to the exceptional EMW absorption property of PFL g-C3N4/NiCo2O4 (2D/2D) heterostructure. The potential of PFL g-C3N4/NiCo2O4 in actual radar stealth is verified through radar scattering cross-section (RCS) simulation. This work paves the way for utilizing 2D/2D heterostructure as an ultra-efficient EMW absorbers.

Polysiloxane encapsulating strategy to enhance the high-temperature electromagnetic wave absorption performance of carbon-rich SiOC ceramics

Carbon-enriched polysiloxane-derived SiOC (C-SiOC) ceramics are promising electromagnetic wave absorption (EMA) materials. However, oxidation and impedance mismatch severely deteriorate their EMA performance at high temperatures. In this study, we used polysiloxane (PSO) to encapsulate the crosslinked precursor of C-SiOC ceramics. After pyrolysis, PSO-derived SiOC-encapsulated C-SiOC (here named PSO-C-SiOC) ceramics were obtained. The PSO-C-SiOC ceramics exhibit an improved oxidation resistance compared with C-SiOC ceramics and basically retain their original dielectric and EMA properties after exposure to air at high temperatures. Moreover, the ceramics can maintain excellent EMA properties at elevated temperatures with good impedance matching. The remarkable high-temperature EMA properties of PSO-C-SiOC ceramics in air are attributed to the protective outer-layer of PSO-derived SiOC ceramic, which enhances oxidation resistance and simultaneously controls the impedance matching. These findings underscore the potential of PSO-C-SiOC ceramics as high-temperature EMA materials.

One-step pyrolysis derived Fe and heteroatom co-doped biochar composites for efficient microwave absorption

Electromagnetic (EM) pollution frequently disrupts the regular operation of sophisticated electrical devices, necessitating the urgent development of lightweight EM wave absorbers that possess powerful absorption capability. Herein, we report a simple method for the preparation of Fe and heteroatom co-doped biochar composites (FeX-BC, where X = N, S) by directly carbonizing the precursors of anhydrous FeCl3, cherry kernel powder, and heteroatom dopants (melamine or Na2S2O3·5H2O). By adding different amounts of dopants during the synthesis of the precursors, it is possible to adjust the heteroatom content of the FeX-BC samples with precision. It is worth mentioning that the FeN0.1-BC composite delivers the best EM wave absorption performance with an effective absorption bandwidth of 4.8 GHz and a minimal reflection loss of −63.2 dB. Furthermore, the significant attenuation of EM wave can be attributed to the synergistic interplay of magnetic loss, dielectric loss and the enhanced impedance matching. This study introduces a simple methodology for the fabrication of EM wave absorbers, a significant contribution to the synthesis, advancement, and functional applications of biomass-derived materials.

Hollow hydrangea-like Mo2C/MoO2/C composites with tunable phase compositions as highly efficient microwave absorbers

With the advancement of modern electronic communication technology, the development of efficient absorbing materials has attracted great interest. Here, hollow hydrangea-like Mo2C/MoO2/C composites are synthesized by soft template method. By adjusting the pyrolysis temperature, Mo2C/MoO2/C composites with different Mo2C and MoO2 contents and degrees of graphitization can be selectively synthesized. The Mo2C/MoO2/C-800 composite with the 30 wt% filler content exhibits a minimum reflection loss of −62.9 dB at 1.6 mm and achieves a maximum absorption bandwidth of 6.2 GHz at 1.9 mm. The interaction between the dielectric properties of each component and the unique 3D hydrangea-like structure promotes microwave absorption and dissipation. Besides, CST simulation further demonstrates the effectiveness of electromagnetic wave dissipation in practical applications. The excellent properties of the hydrangea-like Mo2C/MoO2/C composites indicate their promising applications in electromagnetic wave absorbers.

Synthesis and high electromagnetic wave absorption performance of carbon-enriched porous SiOC ceramics

The carbon-enriched porous SiOC ceramics with enhanced electromagnetic wave (EMW) absorption properties were synthesized through the hydrothermal method followed by a polymer-derived ceramics (PDCs) process. As the annealing temperature rises from 1200 °C to 1500 ℃, SiC and SiO2 crystals are gradually separated from the porous amorphous SiOC matrix, and the degree of graphitization of free carbon increases. The porous SiOC ceramics annealed at 1400 °C exhibit the presence of SiC, SiO2, turbostratic graphite, and amorphous SiOC phases, which significantly impact the impedance matching and attenuation constant of the material. The minimum reflection loss (RLmin) value of the SiOC ceramics reaches −67.98dB with a matching thickness of 3.19mm and the effective absorption bandwidth (EAB) is 4.45GHz at 1.39mm. The carbon-enriched porous SiOC ceramics with strong absorption capacity and wide absorption bandwidth are primarily owing to appropriate impedance matching and multiple attenuation mechanisms, such as conduction loss, interfacial polarization, and defect-induced polarization, indicating that the SiOC ceramics exhibit significant potential as a high-performance EMW absorbing material.

Significantly Enhanced Electromagnetic Wave Absorption Performances and Corresponding Mechanism of LaMn1-xFexO3 Perovskites

Improving the performance of LaMnO3 perovskite is essential to make it an efficient and ultra-light electromagnetic wave (EMW) absorbing material. In this work, LaMn1-xFexO3 powders (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized by controlling the doping of Fe3+ ions at the B-site using the citric acid-assisted sol-gel method. The effects of Fe3+ ions doping content on crystal structures, magnetic properties and EMW absorption performances were investigated. The obtained LMFO-4 sample exhibited a minimal reflection loss of -54.99 dB at 13.68 GHz, with an adequate absorption bandwidth (RL < -10 dB) spanning 4.56 GHz (11.6∼16.16 GHz) at a matching layer thickness of 2.0 mm. The exceptional EMW absorption performances could be attributed to the Jahn-Teller effect, the double-exchange interactions and the magnetic interactions of Mn and Fe ions. Furthermore, the Computer Simulation Technology (CST) simulations demonstrated that the Radar Cross Section (RCS) value of LMFO-4 was lower than -25.10 dBm2 across angles ranging from -90° to 90° with a thickness of 2.0 mm, indicating the remarkable radar wave attenuation ability. These insights provided valuable guidance for advancing perovskite-based materials tailored for efficient and ultra-light electromagnetic wave absorption applications.

Preparation of broad-bandwidth porous carbon electromagnetic wave absorption materials from agricultural waste corncob

Developing advanced electromagnetic wave-absorbing materials tend to focus on the characteristics of low cost, renewability, environmental friendliness, strong absorption, wide bandwidth, and lightweight. This paper described the preparation of porous carbon electromagnetic wave-absorbing materials with strong absorption, broad bandwidth and thin thickness by one-step charring of corncob, an agricultural waste. The corncob porous carbon (CPC) materials were prepared when the charring temperature was 600 °C, the charring time was 3 h and the activator ratio was 0.25:1. The obtained CPC exhibited porous microstructure with average pore size of approximately 1 μm. Its specific surface area was 713.971 m2·g−1, with pore volume of 0.289 mL·g−1 and high degree graphitization. CPC showed excellent electromagnetic wave absorption performance with minimum reflection loss (RL min) of −38.21 dB and effective absorption bandwidth (EAB) of 5.6 GHz at a relatively thin thickness of 2.0 mm. CPC was capable of absorbing 99.9 % of electromagnetic wave (EMW).

Microwave absorption properties of one-step formed CNTs/Fe3O4-carbonyl iron superflexible buckypaper by directional pressure filtration

In order to realize the integration of structure and function of microwave-absorbing materials, carbon nanotubes/magnetic nanoparticle buckypaper (CNT/MNP BP) self-supporting, ultra-flexible, ultra-thin and ultra-light composites were prepared by composing CNTs with MNPs through directional pressure filtration technology. The BP composite, with a bulk density of 0.62 g/cm3 and a thickness of 0.21 mm, can be uninterruptedly tightly wound around a 4 mm diameter glass rod many times without structural damage. The microwave-absorbing properties and magnetic properties of the CNT/MNP composites with different compositions and contents were systematically analyzed. The CNT-Fe3O4 Buckypaper with 33.3 wt% Fe3O4 content (CF33.3 %) has the best electromagnetic wave absorption capability, with a minimum reflection loss value of −52.01 dB and an effective absorption bandwidth of 4.08 GHz. The VSM test shows that the saturation magnetization strength of CF33.3 % is 38.4 emu/g. The excellent electromagnetic wave absorption performance is attributed to the polarization and conduction losses of CNTs, natural resonance, exchange resonance and eddy current losses of MNPs, and multiple scattering and reflection within the porous network structure of the composites. The CNTs and MNPs has good dispersion in the buckypaper, where CNTs construct a superflexible skeleton besides an excellent conductive network. The self-supporting superflexible CNT/MNP BP composites have a good application prospect in the field of wearable electronic devices in the future.