Wave Absorption Research Articles

Multifunctional hierarchical electronic skins: Unveiling self-repairing mechanisms and advancements in sensing and shielding performance

In light of advancements in electronic skins (E-skins), their application in extreme environments poses significant challenges. Inspired by real human skin, we have developed a hierarchical structured electronic skin that utilizes flexible carbon fiber fabric as a framework. Copper nanoflakes and embedded sensors function as the neural layer, while Ethylene Vinyl Acetate acts as the dermal layer, and Polytetrafluoroethylene is employed as the epidermal layer. The reported E-skin demonstrates outstanding flexibility, excellent heat resistance, robust mechanical properties (fracture strength of 1600 MPa, Young's modulus approximately 3.8 GPa), exceptional bending/compression strain performance, excellent hydrophobicity (water contact angle of 120°), effective electromagnetic shielding performance (approximately 45 dB total shielding effectiveness for X-band), and electromagnetic wave absorption capability. Additionally, this E-skin possesses self-healing properties, capable of restoring to its original hydrophobic state within 30 s under a 9V voltage through the Joule heating effect, complemented by corresponding theoretical and mathematical modeling. This E-skin introduces a novel, environmentally friendly, and operationally simple strategy for enhancing the extreme environment resistance and durability of flexible devices.

Construction of spherical heterogeneous interface on ZnFe2O4@C composite nanofibers for highly efficient microwave absorption

Enriching the electromagnetic wave loss mechanism and improving the impedance matching are the keys to improve the electromagnetic wave absorption performance of carbon fibers. In this study, beaded ZnFe2O4@C absorbing composite fibers (ZFCF) with synergistic effects of magnetic loss and dielectric loss was prepared by electrospinning and heat treatment. ZnFe2O4 magnetic particles effectively improve the impedance matching and increase the loss mechanism of carbon nanofibers. The optimal ZFCF composite has excellent absorption performance, with a minimum reflection loss of −53.6 dB at 2.64 mm and the widest effective absorption bandwidth of 4.32 GHz. The excellent absorption performance is attributed to significant magnetic losses from eddy currents and magnetic resonance generated by ZnFe2O4, and strong interfacial polarization from the numerous heterogeneous interfaces. Additionally, the one-dimensional carbon nanofibers create a conductive network and structural defects that enhance conductive loss and dipole polarization effects. Moreover, the RCS of ZFCF composite was significantly reduced by −32.85 dBm2. The combination of simulation technology and material design is of great significance for the study of electromagnetic wave absorption mechanism and the rational design of electromagnetic wave absorbing coatings.

A Semi-amorphous Ti-BDC-derived Ti/C nanocomposite for efficient electromagnetic wave absorption

Electromagnetic (EM) interference presents a crippling risk to both human health and the dependability of technological devices. Due to their diverse advantages, metal-organic framework (MOF) derivatives have received much attention in developing novel EM wave-absorbing materials. Nevertheless, achieving desirable EM wave absorption capabilities in magnetic carbon-based absorbers through deliberate adjustment of MOFs remains a difficult task. In this study, a novel nanoporous carbon material (TiO2/C) has been successfully synthesized by a semi-amorphous material (Ti-BDC), which has excellent EM wave absorption properties. In detail, the minimum reflection loss (RL) of −49.7 dB and broad effective absorbing bandwidth (EAB) of 4.16 GHz can be reached with an absorbent thickness of 2.2 mm. The improved performance is mostly due to the dipole polarization of the functional groups and the even distribution of the nanoparticles, which form a seamless network. This promotes the dissipation of polarization and dielectric energy at the interface. In addition, the TiO2 nanoparticles on the carbon material improve the impedance matching, further enhancing the material's absorption performance.

Joule heat induced ultrafine ZrO2/C composites for enhanced microwave absorption

Lightweight absorbers with effective broad absorption and high thermal stability are highly desirable in the field of electromagnetic wave absorption. In this work, we introduce a facile carbon thermal shock method to prepare ZrO2/C composites using UIO 66 (Zr) as the precursor. The instant heating and cooling process ensures the uniform deposition of nano-sized ZrO2 (ca. 5–15 nm) on graphene, exhibiting an ultrahigh interfacial number density of ca. 1015 m−2 that favors polarization loss. Due to the synergetic effect of dielectric loss and impedance matching, the prepared ZrO2/graphene composites show tunable wide-microwave absorption performance by adjusting the heat temperature, and possess a wide absorption band covering the entire X and Ku band. Notably, the ZrO2/graphene composites show high thermal stability up to 1000 °C, which presents great potential for microwave absorption applications.

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.

In Situ Exsolution-Prepared Solid-Solution-Type Sulfides with Intracrystal Polarization for Efficient and Selective Absorption of Low-Frequency Electromagnetic Wave.

The excellent dielectric properties and tunable structural design of metal sulfides have attracted considerable interest in realizing electromagnetic wave (EMW) absorption. However, compared with traditional monometallic and bimetallic sulfides that are extensively studied, the unique physical characteristics of solid-solution-type sulfides in response to EMW have not been revealed yet. Herein, a unique method for preparing high-purity solid-solution-type sulfides is proposed based on solid-phase in situ exsolution of different metal ions from hybrid precursors. Utilizing CoAl-LDH/MIL-88A composite as a precursor, Fe0.8Co0.2S single-phase nanoparticles are uniformly in situ formed on an amorphous substrate (denoted as CoAl), forming CoAl/Fe0.8Co0.2S heterostructure. Combing with density functional theory (DFT) calculations and wave absorption simulations, it is revealed that Fe0.8Co0.2S solid solution has stronger intracrystal polarization and electronic conductivity than traditional monometallic and bimetallic sulfides, which lead to higher dielectric properties in EM field. Therefore, CoAl/Fe0.8Co0.2S heterostructure exhibits significantly enhanced EMW absorption ability in the low-frequency region (2-6GHz) and can achieve frequency screening by selectively absorbing EMW of specific frequency. This work not only provides a unique method for preparing high-purity solid-solution-type sulfides but also fundamentally reveals the physical essence of their excellent EMW absorption performance.

Hierarchical Magnetic Carbon Nanoflowers for Ultra-Efficient Electromagnetic Wave Absorption.

Porous carbon nanomaterials are widely applied in the electromagnetic wave absorption (EMWA) field. Among them, an emerging flower-like carbon nanomaterial, termed carbon nanoflowers (CNFs), has attracted tremendous research attention due to their unique hierarchical flower-like structure. However, the design of flower-like carbon nanomaterials with different magnetic cores for EMWA has rarely been reported. Herein, a general template method is proposed to achieve a set of high-quality magnetic CNFs, namely Co@Void@CNFs, CoNi@CNFs, and Ni@CNFs. The prepared magnetic CNFs have highly accessible surface area and internal space, rich heteroatom content, multi-scale pore system, and uniform and highly dispersed magnetic nanoparticles, as a result, deliver superior EMWA performance. Specifically, when the thickness is 2.6mm, the Co@Void@CNFs exhibit a maximum refection loss (RLmax) of -56.6dB and an effective absorption bandwidth (EAB) from 8.0 to 12.1GHz covering the whole X band. The CoNi@CNFs have an RLmax of up to -57.6dB and a wide EAB of 5.6GHz at just 1.9mm. For the Ni@CNFs, possess an ultra-broad EAB of 6.1GHz, covering the entire Ku band at 2.0mm. Overall, the hierarchical magnetic carbon nanoflowers proposed here offer new insights toward realizing multifunctional integrated carbon nanomaterials for EMWA.

Influence of MWCNTs addition on the electromagnetic absorption performance of polymer-based wave absorber

Influence of MWCNTs addition on the electromagnetic absorption performance of polymer-based wave absorber

Construction of Fe3C@N-doped graphene layers yolk-shelled nanoparticles on the graphene sheets for high-efficient electromagnetic wave absorption

Combining graphene with magnetic nanoparticles (NPs) can significantly improve electromagnetic wave (EMW) absorption properties compared to single counterparts. However, the magnetic NPs are easily oxidized upon exposure to air for a long time, resulting in their inferior stability. Herein, we designed and synthesized N-doped graphene-coated Fe3C yolk-shelled nanoparticles on the graphene sheets (Fe3C@NC/G). The diameter of the yolk is around 9.41 nm, while the thickness of the NC shell is about 3.0 nm. Due to the unique structure and small sized yolk-shelled NPs, the Fe3C@NC/G exhibits excellent EMW absorption property with a minimal reflection loss of −40.05 dB as the matching thickness is 2.1 mm, superior to most reported graphene-based materials. Experimental results and Density Functional Theory (DFT) calculation demonstrate that the special yolk-shelled nanostructure, abundant defects and the interfaces between Fe3C nanoparticles and N-doped graphene layer are responsible for the enhanced EMW absorption property of Fe3C@NC/G. This study provides an efficient way for development of high-performance EMW absrobers based on graphene and magnetic nanostructures.

Study on the Active Wave Absorption Methods in Lattice Boltzmann Numerical Wave Tank

The active wave absorption method has been widely employed in numerical wave tanks. The wave absorption performance of active wave absorption methods is investigated within a numerical wave tank based on a lattice Boltzmann method. Specifically, two active wave absorption methods—the classical shallow water method and the extended range method—are compared. By analyzing the contributions of free and bound components in the harmonics of the reflected wave to the reflection coefficient, we found that the extended-range method is more effective than the shallow-water method in absorbing the reflection of the primary harmonic. Moreover, a wave absorption performance index is proposed to carry out rapid evaluation of active wave absorption method performance without resorting to numerical simulations. Our findings indicate that the performance index ratio of two active wave absorption methods closely mirrored their reflection coefficient ratio. Notably, the extended-range method significantly reduces the performance index in both shallow and deep waters, exhibiting superior active absorption performance within the lattice Boltzmann method-based numerical wave tank context compared to the shallow-water method.

Bridging dielectric-magnetic synergistic units with MOFs on fibers structure for high-efficient microwave absorption at low filler loading

Metal-organic framework (MOF) capable of magnetic-dielectric synergy loss mechanisms shine in the field of electromagnetic wave (EMW) absorption, whereas their high filler loading in the matrix remains a challenge and limit their practical application. Here, we mono-disperse bimetallic CoZn-MOF on conductive carbon nanofibers precursor via electrospinning technique and a following heat-treatment was employed to construct a Co–ZnO@NC carbon nanofiber (CNF) composites. The Co–ZnO particles with a size of 2 μm are evenly distributed within the carbon fibers, forming a unique structure resembling a “pearl necklace”. The introduction of one-dimension (1D) CNF can prolong the electron transport path and effectively reduces the percolation threshold of the composites. The composites are endowed with abundant heterogeneous interfaces, excellent magnetic-dielectric synergy and improved impedance matching, benefiting from which the obtained Co–ZnO@NC CNF composites demonstrate a maximum reflection loss (RLmin) of −54.5 dB at a thickness of 2.3 mm and an effective absorption bandwidth (EAB) of 8.12 GHz at a filler loading of merely 10 %. This study provides a feasible strategy for the design of MOF-derived absorbers with enhanced microwave absorption capacity at low filler loading.

Regulating integral alignment of magnetic MXene nanosheets in layered composites to achieve high-effective electromagnetic wave absorption

The integral structure design is equally crucial to the regulation of electromagnetic components in microwave absorbing materials. In this work, magnetic MXene/polyvinylidene fluoride composites with integral nacre-like structure were prepared by successive hot-pressing process to realize the layered arrangement of Ni anchored MXene (Ni@MXene). The order degree of Ni@MXene from random to orientation can be adjusted by gradually changing compression ratio. Interestingly, increasing the orientation degree of Ni@MXene effectively improves the dielectric constant, minimal reflection loss (RLmin) and effective absorption bandwidth (EAB) of the layered composites. This is attributed to the improved loss ability by increasing the contact areas between Ni@MXene and vertically incident electromagnetic waves, inducing multiple scattering/reflection effect, and the formation of localized conductive pathways. As a result, the layered composite with optimal layered structure delivers the best electromagnetic microwave absorption performance with a RLmin of −69.8 dB and an EAB of 4.77 GHz. Besides, increasing the orientation degree can also optimize the mechanical properties of the layered composites, with the maximum tensile strength and toughness of 32.6 MPa and 115.0 MJ m−3, respectively. Therefore, this work proves the adjustability of absorption performance by changing the distribution of absorbents, and integrates the structure and function for microwave absorption materials.

Preparation of nitrogen-doped reduced graphene oxide/zinc ferrite@nitrogen-doped carbon composite for broadband and highly efficient electromagnetic wave absorption

Traditionally reduced graphene oxide (RGO)-based electromagnetic wave (EMW) absorbing materials have poor absorption effectiveness due to impedance mismatch caused by skin effect. The introduction of structural defects and the design of heterogeneous interfaces play a crucial role in enhancing the polarization effect of EMW absorbers. In this study, nitrogen-doped reduced graphene oxide/zinc ferrite@nitrogen-doped carbon (NRGO/ZnFe2O4@NC) ternary composite with rich heterogeneous interfaces is constructed by combining solvothermal reaction, in-situ polymerization, annealing treatment with subsequent hydrothermal reaction. The research results have shown that the obtained NRGO/ZnFe2O4@NC ternary composite exhibits a unique core-shell structure and excellent EMW absorption performance. At a thickness of 2.61 mm, the maximum effective absorption bandwidth can reach 7.2 GHz, spanning the entire Ku-band and a portion of the X-band, and the minimum reflection loss is –61.1 dB, which is superior to most reported RGO-based EMW absorbers. The excellent EMW absorbing ability is mainly ascribed to the optimized impedance matching and the enhanced polarization loss caused by the abundant heterogeneous interfaces and structural defects derived from heteroatomic nitrogen doping. Furthermore, the radar cross section in the far field is simulated by a computer simulation technique. This study provides a novel way to prepare core-shell magnetic carbon composites as highly efficient and broadband EMW absorbers.

Multifunctional electromagnetic wave absorbing carbon fiber/Ti3C2TX MXene fabric with superior near-infrared laser dependent photothermal antibacterial behaviors

Developing multifunctional materials which could simultaneously possess anti-bacterial ability and electromagnetic (EM) absorption ability during medical care is quite essential since the EM waves radiation and antibiotic-resistant bacteria are threatening people’s health. In this work, the multifunctional carbon fiber/Ti3C2Tx MXene (CM) were synthesized through repeated dip-coating and following in-situ growth method. The as-fabricated CF/MXene displayed outstanding EM wave absorption and highly efficient photothermal converting ability. The minimum reflection loss (RL) of −57.07 dB and ultra-broad absorption of 7.74 GHz could be achieved for CM composites. By growth of CoNi-layered double hydroxides (LDHs) sheets onto MXene, the absorption bandwidth for carbon fiber/Ti3C2Tx MXene layered double hydroxides (CML) could be reach 5.44 GHz, which could cover the whole Ku band. The excellent photothermal effect endow the CM composites with excellent antibacterial performance. The antibacterials tests indicated that nearly 100 % bactericidal efficiency against E. acoil and S. aureus was obtained for the CM composite after exposure to near-infrared region (NIR) irradiation. This work provides a promising candidate to combat medical device-related infections and EM pollution.

MOFs-Derived Strategy and Ternary Alloys Regulation in Flower-Like Magnetic-Carbon Microspheres with Broadband Electromagnetic Wave Absorption

HighlightsMetal–organic frameworks-derived CoNiM@C (M = Cu, Zn, Fe, Mn) microspheres were successfully fabricated with custom-built magnetic alloy-carbon heterogeneous interfaces.Flower-like CoNiMn@C microspheres achieve broadband electromagnetic wave absorption with effective absorption bandwidth of 5.8 GHz at only 2.0 mm thickness.Visual interface charge distribution and hierarchical magnetic coupling were observed to elucidate the electromagnetic energy absorption mechanism.

Exploring the Microstructural Effect of FeCo Alloy on Carbon Microsphere Deposition and Enhanced Electromagnetic Wave Absorption.

The rational design of magnetic carbon composites, encompassing both their composition and microstructure, holds significant potential for achieving exceptional electromagnetic wave-absorbing materials (EAMs). In this study, FeCo@CM composites were efficiently fabricated through an advanced microwave plasma-assisted reduction chemical vapor deposition (MPARCVD) technique, offering high efficiency, low cost, and energy-saving benefits. By depositing graphitized carbon microspheres, the dielectric properties were significantly enhanced, resulting in improved electromagnetic wave absorption performances through optimized impedance matching and a synergistic effect with magnetic loss. A systematic investigation revealed that the laminar-stacked structure of FeCo exhibited superior properties compared to its spherical counterpart, supplying a higher number of exposed edges and enhanced catalytic activity, which facilitated the deposition of uniform and low-defect graphitized carbon microspheres. Consequently, the dielectric loss performance of the FeCo@CM composites was dramatically improved due to increased electrical conductivity and the formation of abundant heterogeneous interfaces. At a 40 wt% filling amount and a frequency of 7.84 GHz, the FeCo@CM composites achieved a minimum reflection loss value of -58.2 dB with an effective absorption bandwidth (fE) of 5.13 GHz. This study presents an effective strategy for developing high-performance EAMs.

Fe3O4 Nanoparticles Embedded into Pyridinic-N-Rich Carbon Nanohoneycomb with Strong dx2-Pz Orbital Hybridization for High-Performance Electromagnetic Wave Absorption.

Carbon-based magnetic nanocomposites as promising lightweight electromagnetic wave (EMW) absorbents are expected to address critical issues caused by electromagnetic pollution. Herein, Fe3O4 nanoparticles embedded into a 3D N-rich porous carbon nanohoneycomb (Fe3O4@NC) were developed via the pyrolysis of an in-situ-polymerized compound of m-phenylenediamine initiated by FeCl2 in the presence of NaCl crystals as templates. Results demonstrate that Fe3O4@NC features highly dispersed Fe3O4 nanoparticles into an ultrahigh specific pyridinic-N doping carbon matrix, resulting in excellent impedance matching characteristics and electromagnetic wave absorbing capability with the biggest effective absorption bandwidth (EAB) of up to 7.1 GHz and the minimum reflective loss (RLmin) of up to -65.5 dB in the thin thickness of 2.5 and 2.3 mm, respectively, which also outperforms the majority of carbon-based absorbers reported. Meanwhile, its high absorption performance is further demonstrated by an ethylene propylene diene monomer wave absorbing patch filled with 8.0 wt % Fe3O4@NC, which can completely shield a 5G signal in a mobile phone. In addition, theory calculation reveals that there is a strongest dx2-Pz orbital hybridization interaction between Fe3O4 clusters and pyridinic-N dopants in the carbon network, compared with other kinds of N dopants, which can not only generate more dipoles of carbon networks but also increase net magnetic moments of Fe3O4, thereby leading to a coupling effect of efficient dielectric and magnetic losses. This work provides new insights into the precise design and synthesis of carbon-based magnetic composites with specific interface interactions and morphological effects for high-efficiency EMW absorption materials.

Perfect active absorption of water waves in a channel by a dipole source

This study investigates the potential use of an active device to efficiently absorb water waves propagating in a channel. The active device comprises a dipole source consisting of two sources in quasi-opposition of phase. We explore the feasibility of this approach to achieve perfect absorption of guided waves through interference phenomena. To accomplish this, we establish the law governing the waves emitted by the dipole source to optimize the absorption of specific incident waves. The validity of this law is demonstrated through numerical simulations and laboratory experiments, encompassing both the harmonic and transient regimes of the experimental set-up.

In situ loading of ZnO on hierarchical porous carbon derived from banana-peel waste to enrich mechanism for microwave absorption

Biomass has received widespread attention due to its easy availability, low cost, and environmental friendliness as an electromagnetic wave absorber candidate. Inspired by the natural porosity of biomass, the three-dimensional (3D) porous carbon materials derived from banana peels were prepared via coordination and pyrolysis carbonization. A conductive network of biomass-zinc complexes was constructed by introducing Zn2+ to coordinate with organic polymers. Hierarchical porous carbon/ZnO composites with a 3D skeleton network were obtained, which demonstrated outstanding electromagnetic wave absorption performance with an effective absorption bandwidth (EAB) of 6.72 GHz and the reflection loss (RL) of −44.18 dB. The banana peel-derived porous carbon (BPC) embedded with ZnO particles brings about conductive loss and interface polarization, further enriching the microwave loss mechanisms. This work offers a fresh idea for creating a green, sustainable, and high-value functional carbon-based composite material.

Absorption-dominant electromagnetic interference shielding material using MXene-coated polyvinylidene fluoride foam

MXene (Ti3C2Tx), known for its exceptional electrical conductivity, unique two-dimensional structure, extensive surface functionality, and hydrophilicity, has emerged as a leading candidate for electromagnetic interference (EMI) shielding applications. Despite these excellent characteristics, EMI shielding materials based on MXene mostly utilize the reflection mechanism, which may cause secondary interferences. This study introduces an approach to utilize MXene as absorption-dominant EMI shielding materials. By engineering a porous layer of polyvinylidene fluoride (PVDF) atop MXene nanoflakes, we achieved a synergistic enhancement in EMI shielding effectiveness (SE) and absorptivity. The PVDF foam serves as an effective impedance matching layer, substantially enhancing the absorption of electromagnetic waves into the shielding material. Incorporating electrically conductive MXene nanoflakes to form a thin film creates a robust conductive network, fully leveraging its inherent performance. This network efficiently dissipates EM waves, thereby significantly enhancing the EMI SE. The shielding performance of this composite was thoroughly evaluated across both the X-band (8.2 GHz–12.4 GHz) and the Ka-band (26.5 GHz–40 GHz) frequencies. It demonstrated high EMI SE, attributed to mechanisms predominantly based on absorption. Specifically, it achieved an EMI SE of approximately 63.3 dB with high absorptivity (0.74) in the X-band and approximately 73.3 dB with high absorptivity (0.85) in the Ka-band. These findings underscore its potential as a route to develop absorption-dominant EMI shielding materials.