Dielectric Attenuation Research Articles

Spontaneous Orientation Polarization of Anisotropic Equivalent Dipoles Harnessed by Entropy Engineering for Ultra-Thin Electromagnetic Wave Absorber

HighlightsThe strengthening mechanism of spontaneous orientation polarization of anisotropic equivalent dipoles within high-entropy alloys (HEAs) is proposed for enhancing dielectric attenuation of HEAs.The source of carbon supporter is expanded to the biomass category, which can construct the shell-core heterointerfaces with HEAs by means of a reformative carbothermal shock method.The sample carbonized cellulose paper/HEAs-Mn2.15 achieves efficient electromagnetic wave absorption of -51.35 dB at an ultra-thin thickness of 1.03 mm.This work combines theoretical calculations and electromagnetic simulations to propose feasible strategies for the design and application of electromagnetic functional devices such as ultra-wideband bandpass filter.

Study of circumferential SH-wave interaction with a piezoelectric cylinder having pre-stressed viscoelastic imperfect coating

In this study, the circumferential interaction behaviour of the SH-wave with a piezoelectric cylinder coated with a viscoelastic material is investigated. The coating interface is imperfect and the viscoelastic material is subjected to pre-stress. By applying mathematical methods to the dynamical governing equations, expressions for displacement components and electric potential is obtained. Utilizing the set of boundary conditions, dispersion and damping equations are established for this model. The impacts of perfect & imperfect interfaces, piezoelectric & dielectric constants, initial stress, dissipation factor, attenuation coefficient and radial thickness ratio of materials on the phase and damped velocities of SH-wave are observed by numerical examples and graphical visuals.

Influence of particle size on the magnetic and microwave absorption properties of magnetite via mechano-mechanical methods for micro-nano-spheres

The demand for innovative electromagnetic wave absorbers stems from the pressing need to mitigate electromagnetic interference and pollution emanating from electronic devices and communication technologies, which pose risks to human health and disrupt the functionality of electronic equipment. This study investigates how particle size influences the magnetic and microwave absorption properties of magnetite micron-nano-spheres. Utilizing ball milling (BM) and mechanochemical alloying (MA), particle sizes were controlled by varying the milling times, resulting in a reduction of magnetite's average particle size from 3 µm to 43 nm. The research uncovers the unique effects of blending micron and nano-sized particles, a phenomenon previously undocumented. It was observed that saturation magnetization and coercivity increase with larger particle sizes due to the small size effect. The complex permittivity, dielectric loss and attenuation constant of the magnetite nanocomposites were influenced by the larger interface area and increased defects in smaller-sized nano-filler composites. Decreasing the magnetite particle size leads to a lower frequency shift and a broader bandwidth of the reflection loss (RL) peak in the fixed absorber, with maximum RL achieved for thinner absorber layers. Notably, the mixed micron-nano magnetite composite exhibits promising microwave absorption capabilities, achieving a maximum RL of −35.36 dB at 16.8 GHz with a 1 mm thickness, making it suitable for lightweight microwave absorption. Resonance frequencies corresponding to RL below −20 dB extend to 3.63 GHz, meeting the 99 % wave absorption requirement due to the high loss tangent of antiferromagnetic resonance and significant magnetic relaxation peak over the 8–18 GHz frequency range. This study underscores the significant impact of adjusting the particle size on microwave absorption properties, where decreasing the size broadens the absorption bandwidth, shifts the RL peak to lower frequencies and maximizes RL with thinner thicknesses. Increasing the nano-filler content enhances the absorption bandwidth and microwave absorber performance by augmenting the dielectric loss, attenuation constant and impedance matching. Overall, controlling the particle size proves effective in tailoring microwave absorption, highlighting the potential of magnetite composites as ultra-thin, lightweight materials capable of absorbing a wide range of microwave frequencies. These composites find applications in microwave absorption, stealth technology and managing electromagnetic interference, leveraging the magnetic properties of ferrites and exploiting super-exchange interactions in microparticles-sized materials. Moreover, they benefit from the amplified dielectric or/magnetic losses resulting from the characteristics of nanoparticle-sized materials, including high surface area, greater surface atoms and multiple reflections, resulting in exceptional microwave absorption performance exceeding 99 % across an exceptionally broad bandwidth.

Microwave-Absorbing Foams with Adjustable Absorption Frequency and Structural Coloration.

Microwave-absorbing materials with regulatable absorption frequency and optical camouflage hold great significance in intelligent electronic devices and advanced stealth technology. Herein, we present an innovative microwave-absorbing foam that can dynamically tune microwave absorption frequencies via a simple mechanical compression while in parallel enabling optical camouflage over broad spectral ranges by adjusting the structural colors. The vivid colors spanning different color categories generated from thin-film interference can be precisely regulated by adjusting the thickness of the conformal TiO2 coatings on Ni/melamine foam. Enhanced interfacial and defect-induced polarizations resulting from the introduction of TiO2 coating synergistically contribute to the dielectric attenuation performance. Consequently, such a foam exhibits exceptional microwave absorption capabilities, and the absorption frequency can be dynamically tuned from the S band to the Ku band by manipulating its compression ratio. Additionally, simulation calculations validate the adjustable electromagnetic wave loss behavior, offering valuable insights for the development of next-generation intelligent electromagnetic devices across diverse fields.

Phytic acid-assisted hybrid engineering of MOF-derived composites for tunable electromagnetic wave absorption

Hybrid engineering is gradually deemed as a powerful approach to solving the bottleneck problem of metal-organic framework (MOF) derived absorbers for practical application. Herein, a new type of semiconductor/carbon-based hybrid material was successfully prepared by phytic acid (PA) modification and carbonization of MOF/bacterial cellulose (BC) precursors, which remedied the drawbacks of structural instability, lethal byproducts and complicated steps reported previously. Specifically, the obtained Fe(PO3)2@C/phosphorus-doped carbon foam (Fe(PO3)2@C/PCF) had a 3D hybrid micro-nanostructure that integrated spatial microcurrent network, multi-level pores, heterogeneous interfaces and lattice defects, showing its unique advantages of low filler content (15 wt.%), moderate surface reflectivity, multi-band microwave absorption and radar stealth. The experimental analysis and CST simulation further revealed that PA dosage can precisely adjust the hybrid phase content, pore texture and electromagnetic parameters of the final product to achieve synergistic enhancement of multiple dielectric response, impedance matching and attenuation capacity. As a result, an effective bandwidth (EAB) of 6 GHz and a minimum reflection loss (RLmin) of −57.0 dB were obtained in the Ku- and C-bands, respectively. These encouraging results may advance the development of novel MOF-derived absorbents based on the hybridization principle.

Dielectric, conductivity properties, elastic moduli, and gamma-ray attenuation abilities: A wide-ranging investigation into Molybdenum added ferrite nanoparticles

The auto combustion technique was employed to synthesis magnesium nano ferrite (MgMoxFe2-xO4). The impact of Mo-doped on the crystal’s structural, morphological, and elastic properties were inspected by applying x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy techniques. Pursuant to the XRD analysis, all samples have a cubic structure with single-phase. The average crystallite size was identified to be in the nanometer range confirmed by SEM and TEM investigations. FTIR data was implemented to assign the force constants of the octahedral and tetrahedral sites. Elastic moduli including the Poisson ratio, Young’s modulus, bulk modulus, and rigidity modulus have been estimated. The division of elastic moduli for all synthesized concentrations was interpreted using binding forces between ions of the cubic lattice spinel. Over and above, the AC conductivity (σ AC) and dielectric properties and their frequency dependence were investigated for the nano ferrites samples as a function of dopant Mo content and temperature. Finally, the radiation shielding capacities of the proposed samples against gamma and fast neutron radiation have been assessed. The findings reveal that the higher the Mo content, the lower the value of the mass attenuation coefficient. There is no significant diversity between the obtained mass attenuation coefficients for the nano and the micro. Among the samples investigated in this study, the highest Mo concentration sample had the largest fast neutron removal cross-section.

Effects of degree of graphitization of C shells on microwave absorption of Fe-C core-shell nanoparticles with excellent comparability

In this study, Fe-C core-shell nanoparticles with identical metal core sizes and C shell thicknesses but varying degrees of graphitization of C shells were fabricated using metal-organic chemical vapor deposition and subsequent annealing. Due to the identical metal core, these nanoparticles exhibite a similar permeability, but significantly varying permittivity depending on how much C shells have been graphitized. It was discovered that proper graphitization of Fe-C nanoparticles annealed at 1350 °C can produce excellent microwave absorption (MA), decent dielectric loss tangent in high frequency region, and moderately strong dielectric loss and attenuation properties. Furthermore, the threshold value of 1/ω is discovered to be a crucial parameter in the theoretical analysis of nonlinear behavior of polarization loss, and thus MA performance of the nanoparticles. This research offers a useful method for creating metal-C nanoparticles with various levels of C shell graphitization. It also provides a clear answer to the crucial question of how the level of C shell graphitization affects the MA performance of metal-C nanoparticles. These results may serve as a reference for the development and mechanism analysis of highly effective metal-C based absorbers.

Effective dielectric attenuation for excellent microwave absorption with broadband response of carbon hollow microspheres derived from resin

Carbon hollow microspheres as microwave absorption materials (MAMs) are of great significance in the research focuses owing to their lightweight, good impedance matching, and modifiable dielectric properties. However, it is still a huge challenge to distinguish the contribution of dielectric attenuation between carbon intrinsic feature and hollow structure due to the lack of appropriate model materials. Then, the inadequate analysis of effective dielectric attenuation resulted in the construction of carbon hollow microspheres semiempirical and often lacked precise modification of microstructure. Herein, a series of carbon hollow microspheres with controllable graphitization and thickness of shell derived from phenolic resin coated on polystyrene microspheres that fully decomposed were synthesized, which is free of the impact of template residue. The carbon fragments ground from hollow microspheres exhibit the same broadband response as hollow microspheres, with effective bandwidth (RL ≤ –10 dB) of 7.6 GHz, while their electromagnetic wave loss mechanisms are distinct. The high dielectric loss of carbon fragments with the same intrinsic characteristics as carbon hollow microspheres is mainly caused by dipole polarization relaxation and enhancement of electrical conductivity ascribed to overlapping between carbon sheets. For the hollow structure, in addition to dipole polarization relaxation attributed to carbon intrinsic feature, the effective dielectric loss is also comprised of the interfacial polarization in advantage due to the effective heterogeneous interface between air and carbon shell. This work provides a simplified model to clarify the effect of carbon intrinsic feature and microstructure on the dielectric loss of carbon hollow microspheres.

Carbon nanotube modified hierarchical NiCo/porous nanocomposites with enhanced electromagnetic wave absorption

The rational modulating of the microstructure in magnetic carbon-based composites is crucial to optimize the electromagnetic wave (EMW) absorption performance. It is challenging for EMW absorbers to simultaneously achieve optimal minimum reflection loss (RLmin) and a broadband effective absorption bandwidth (EAB). In this paper, carbon nanotubes (CNTs)-modified NiCo/CNTs nanosheets were effectively prepared as a new EMW absorption material utilizing NiCo-containing metal-organic framework (MOF) as a sacrificial precursor. As expected, NiCo/CNTs-650 demonstrated both a broadband EAB of 7.04 GHz and the RLmin of − 58.14 dB at 15.9 GHz with a thickness of 2.0 mm. Furthermore, NiCo/CNTs-650 is capable of achieving 30.2 dB m2 RSC (radar cross section) reduction under an incident angle of 7° via CST, while NiCo/CNTs-70015 % achieved a reduction of 39.47 dB m2 at 0 °. These performances outperformed that other CNTs-decorated MOF-derived hierarchical composites previously described. NiCo/CNTs-650 combines the synergistic effects of magnetic loss provided by zero-dimensional (0D) NiCo alloy, dielectric attenuation realized by one-dimensional (1D) CNTs, and optimized impedance matching through two-dimensional (2D) nanosheets with abundant hierarchical interfaces. These studies provide a specialized route for the manufacture of mixed-dimensional hierarchical EMW absorbents with high performance.

Metal‐Organic Framework Derived Multidimensional Carbon/Multifluorination Epoxy Nanocomposite with Electromagnetic Wave Absorption, Environmentally Adaptive, and Blue Energy Harvesting

Bimetallic metal−organic framework (MOF)‐derived multidimensional composites have garnered tremendous attention in electromagnetic wave absorption owing to their remarkable attenuation capacity. And the diversified application scenarios require microwaves absorption materials (MAMs) with robust environmentally adaptive, but efficiently integrating multifunctionality within single MAMs is extremely challenging. Herein, a multifunctional CoC@FeNiG‐F nanocomposite is fabricated by synergistic strategy of in situ growth, C–F···π interaction and microwave irradiation. The MAMs exhibit a strong reflection loss of −75.18 dB with 3.95 GHz effective absorption bandwidth benefited from magnetic–dielectric attenuation, impedance matching, and multiple‐reflection loss. Remarkably, it is first time to obtain the efficient MAMs accompanied with excellent mechanical (80.3 MPa), superamphiphobicity (153° and 151°), anticorrosion (45 d), and flame retardancy (V‐0 rating), which illustrate that the combination of CoC@FeNiG 3D‐skeleton and long‐chain perfluorinated epoxy remarkably improve robust multifunctionality and environmentally adaptive. In particular, the MAMs are assembled into liquid–solid triboelectric nanogenerator, and the output performance (19.7 V, 1.68 μA) and durability (10 000s) are obviously improved benefiting from the trap effect of carbonized MOF. Therefore, this work provides an efficient guideline for designing advanced MAMs with robust environmentally adaptive and sustainable energy harvesting performance in extreme environment application.

Facile fabrication of ultra-light N-doped-rGO/g-C3N4 for broadband microwave absorption

“Thin thickness”, “lightweight”, “wide absorption bandwidth” and “strong absorption” are the new standards of contemporary science and technology for microwave absorption(MA) material. In this study, N-doped-rGO/g-C3N4 MA material was prepared for the first time by simple heat treatment, which the N atoms were doped into rGO and g-C3N4 was dispersed on the surface of N-doped-rGO, and its density is only 0.035 g/cm3. The impedance matching of the N-doped-rGO/g-C3N4 composite was well adjusted by decreasing the dielectric constant and attenuation constant due to the g-C3N4 semiconductor property and the graphite-like structure. Moreover, the distribution of g-C3N4 among N-doped-rGO sheets can produce more polarization effect and relaxation effect by increasing the lamellar spacing. Furthermore, the polarization loss of N-doped-rGO/g-C3N4 could be increased successfully by doping N atoms and g-C3N4. Ultimately, the MA property of N-doped-rGO/g-C3N4 composite was optimized significantly, with a loading of 5 wt%, the N-doped-rGO/g-C3N4 composite exhibited the RLmin of −49.59 dB and the effective absorption bandwidth could reach 4.56 GHz when the thickness was only 1.6 mm. The “thin thickness”, “lightweight”, “wide absorption bandwidth” and “strong absorption” of MA material are actually achieved by the N-doped-rGO/g-C3N4.

Layer-transferred gallium arsenide heterojunction bipolar transistor on insulator substrate

We report a first demonstration of GaAs HBT-OI fabricated using epitaxy growth, wafer bonding and layer transfer technique. Excellent bonding yield was found on the 200 mm GaAs HBT-OI wafer with wafer bowing of less than 90 µm. A dc gain of 20, and cutoff frequency (fT) of 6.5 GHz was measured for a device with emitter finger of 6 × 18 µm2. Its ideality factors for collector and base were 1.19 and 1.44, respectively. These results showed that the method of GaAs HBT-OI fabrication can be used for future integration of III-V on a common Si platform with low RF power dielectric attenuation.

Three-dimensional melamine sponge hollow carbon/Ni3ZnC0.7/carbon nanotubes with tunable high-performance microwave absorption performance

Constructing three-dimensional microstructure with special morphology is an important method to improve the flexibility, low density and high performance of absorbing materials. Herein, Ni3ZnC0.7/carbon nanotubes/melamine sponge hollow carbon (NZC/CNTs/SHC) composites were prepared by vacuum filtrating precursor containing NiZn ions and CNTs followed with calcining under N2 flow. The loading of NZC/CNTs can be tuned by controlling the filtrating time of 0.5, 1 and 2 h. The Ni3ZnC0.7 and CNTs were uniformly dispersed on the surface of melamine sponge carbon skeleton and the carbon shows hollow structure. The 2-NZC/CNTs/SHC composite (filtrating time of 2 h) exhibited a minimum reflection loss (RL) value of − 114.5 dB (1.3 mm) and an effective absorption bandwidth (EAB, RL<−10 dB) of 12.5 GHz at a matching thickness of 1.9 mm. The outstanding wave-absorbing properties of NZC/CNTs/SHC composites can be attributed to their unique hollow structure, which results in multiple reflections and scattering, interface/dipole polarization, improved dielectric and magnetic attenuation capability.

Multiscale structure and interface engineering of Fe/Fe3C in situ encapsulated in nitrogen-doped carbon for stable and efficient multi-band electromagnetic wave absorption

Most reported electromagnetic wave absorption (EWA) materials show significant effective absorption in a certain frequency range, but their performances deteriorate dramatically as the frequency changes. As the range of working frequencies for electronic devices is gradually widening, it is of great interest to explore frequency-insensitive EWA materials that can achieve efficient absorption in every waveband by simply changing the absorption thickness. To this end, a multi-scale absorber (Fe/Fe3C@NC) is rationally synthesized by chemical foaming and in-situ growth strategy. By controlling the growth of carbon nanotubes, the Fe/Fe3C@NC-2 exhibits a well-constructed 3D multi-scale architecture. Thanks to dipole polarization, interface polarization and magnetic-dielectric energy conversion, the Fe/Fe3C@NC-2 overcomes the frequency dispersion behavior and keeps a stable dielectric attenuation capability across the entire frequency range. Consequently, it delivers a superb full-band absorption of -50.1, -59.83, -55.87 and -51.91 dB in the S, C, X and Ku bands, respectively. The maximum radar cross-sectional reduction reaches 35.44 dB m−2 when the incident θ is 20°, testifying its impressive performance. Surprisingly, this EWA material also shows a remarkable resistance to oxidation and corrosion derived from the tightly coated carbon layers. This work provides new insight into the design of multi-band and stable EWA materials for practical application.

High-Entropy Enhanced Microwave Attenuation in Titanate Perovskites.

High-entropy oxides (HEOs), which incorporate multiple-principal cations into single-phase crystals and interact with diverse metal ions, extend the border for available compositions and unprecedented properties. Herein, a high-entropy-stabilized (Ca0.2 Sr0.2 Ba0.2 La0.2 Pb0.2 )TiO3 perovskite is reported, and the effective absorption bandwidth (90% absorption) improves almost two times than that of BaTiO3 . The results demonstrate that the regulation of entropy configuration can yield significant grain boundaries, oxygen defects, and an ultradense distorted lattice. These characteristics give rise to strong interfacial and defect-induced polarizations, thus synergistically contributing to the dielectric attenuation performance. Moreover, the large strains derived from the strong lattice distortions in the high-entropy perovskite offer varied transport for electron carriers. The high-entropy-enhanced positive/negative charges accumulation around grain boundaries and strain-concentrated location, quantitatively validated by electron holography, results in unusual dielectric polarization loss. This study opens up an effective avenue for designing strong microwave absorption materials to satisfy the increasingly demanding requirements of advanced and integrated electronics. This work also offers a paradigm for improving other interesting properties for HEOs through entropy engineering.

Investigating Concrete Properties Using Dielectric Constant from Ground Penetrating Radar Scans

Determining the material properties and existing capacity of concrete infrastructure using nondestructive techniques is challenging due to evolving design requirements, unknown as-built conditions, and ongoing maintenance and deterioration. Concrete’s material properties, including density, porosity, and compressive strength, are usually determined by mechanical testing, but being able to measure these properties noninvasively could aid engineers in maintaining and designing concrete infrastructure. Research into nondestructive methods for determining material properties of concrete has shown relationships between mechanical properties and ground penetrating radar (GPR) properties such as dielectric constant, attenuation, and instantaneous amplitude. We investigated direct relationships between dielectric constant and the density, porosity, and compressive strength of 23 mature concrete samples with varying mix designs using a commercial 1 GHz GPR. In normal-weight concrete, weak trends were seen between a dielectric for compressive strength (R2=0.76) and one for density (R2=0.64), whereas no significant trend was found with porosity (R2=0.52). The GPR unit used provides acceptable data but has limited resolution for analyses and utility. The dielectrics showed distinct clustering by mix type—particularly the inclusion of materials such as blast furnace slag. While demonstrating that the dielectric constant is a candidate for rapid concrete comparisons, there is also a demonstrated need for further investigation of the complex relationships between mechanical and electromagnetic properties in concrete.

MOF-derived CoNC@rGO/amine-rich@rGO/fluorinated-epoxy nanocomposites with EMI shielding, mechanical robustness, superamphiphobicity and long-term anticorrosion properties

Along with the rapid development of electronic devices and communication systems, electromagnetic (EM) radiation pollution has become an increasingly serious problem. However, it is greatly challenging to achieve absorption-dominated electromagnetic interference (EMI) shielding and robust multifunctional simultaneously. In this work, we synthesize zeolitic imidazolate framework (ZIF67)-derived CoNC@reduced graphene oxide (rGO) and amine-rich surface rGO (NH2@rGO), and subsequently fabricate NH2-CoNC@rGO-fluorinated epoxy (FEP) nanocomposites by the microwave irradiation strategy, and this is the first time to obtain composite combining excellent EMI shielding, mechanical robustness, superamphiphobicity and long-term anticorrosion properties. Wherein, 3-(perfluoro-n-octyl) propenoxide (PFOP) provides the perfluorinated long chains, which improves both mechanical properties via internal antiplasticization effect, and the dispersity and loading of nanofiller via CF⋯HN/π interactions; 4,4′-hexafluoroisopropylidenediphenol diglycidyl ether (FAEP) increases the compatibility and mechanical robustness; NH2@rGO provides the good interfacial bonding, dielectric attenuation and anode protection; CoNC@rGO endows suitable magnetic and dipolar relaxation loss, micro/nanostructures and cathodic protection. Remarkably, the optimized nanocomposite exhibits satisfied tensile and impact strength (64.4 MPa, 33.7 kJ/m2), EMI shielding properties (56 dB), thermal conductivity (1.13 W·m−1·K−1), superhydrophobicity (154°) and superoleophobicity (151°), self-cleaning, good chemical and mechanical robustness, Joule heating capacity and long-term anticorrosion (30 d). Furthermore, the microwave irradiation effect, multiple EMI shielding and anti-corrosion mechanism have been discussed in detail. This study provides an efficient guideline for designing multicomponent and multidimensional epoxy nanocomposite with EMI shielding and robust multifunctional property in aerospace, underwater equipment, electronic devices and precision construction protection.

Magnetic Composite Rapidly Treats Staphylococcus aureus-Infected Osteomyelitis through Microwave Strengthened Thermal Effects and Reactive Oxygen Species.

It is difficult to effectively treat bacterial osteomyelitis using photothermal therapy or photodynamic therapy due to poor penetration of light. Here, a microwave (MW)-excited magnetic composite of molybdenum disulfide (MoS2 ) / iron oxide (Fe3 O4 ) is reported for the treatment of bacteria-infected osteomyelitis. In in vitro and in vivo experiments, MoS2 /Fe3 O4 is shown to effectively eradicate bacteria-infected mouse tibia osteomyelitis, due to MW thermal enhancement and reactive oxygen species (ROS) (1 O2 and ·O2 - ) production under MW radiation. In addition, the mechanism of MW heat generation is proposed by MW network vector analysis. By the density functional theory and finite element method, the ROS generation mechanism is proposed. The synergy or conductive network between dielectric MoS2 and magnetic Fe3 O4 can reach both enhancement of the dielectric and magnetic attenuation capability. In addition, abundant interfaces are generated to enhance the attenuation of electromagnetic waves by MoS2 and Fe3 O4, introducing multiple reflections and interfacial polarization. Therefore, MoS2 /Fe3 O4 has excellent MW absorption ability based on the synergy or conductive network between MoS2 and magnetic Fe3 O4 as well as multiple dielectric reflections and interfacial polarization.

Effect of Graphene/Spherical Graphite Ratio on the Properties of PLA/TPU Composites.

Wave-absorbing materials are developing in the direction of “light weight, wide frequency band, thin layer and high strength”, and it is difficult to achieve the synergy between wave-absorbing performance and mechanical properties when graphene absorbent is compounded with a single resin matrix. In this paper, based on the preparation of a new composite absorbing wire with a graphene (GR)/spherical graphite (SG) double absorbent and polylactic acid (PLA)/thermoplastic polyurethane (TPU) double matrix, we proposed a new method to prepare samples for testing the electromagnetic parameters and tensile strength by fused deposition modeling (FDM). Furthermore, the effect of SG/GR ratio on the microwave absorbing properties and mechanical properties of PLA/TPU composites was specifically studied. It was found that when the ratio of SG/GR was small (0:5, 1:4), the dielectric loss (interfacial polarization loss, dipole polarization loss, conductivity loss) and attenuation ability of the composites were stronger, and the impedance matching was better. When the SG/GR ratio was large (5:0, 4:1), the composites had high strength and toughness. When the ratio of SG/GR was moderate (2:3, 3:2), it could retain the absorbing and mechanical properties of the absorbing materials. On the one hand, the SG and PLA/TPU matrix formed an “island structure”, which improves the dispersion of GR; on the other hand, the GR and PLA/TPU matrix formed a “core-shell structure”, which promotes polarization and multiple scattering.

Bionic Scarfskin-Inspired Hierarchy Configuration toward Tunable Microwave-Absorbing Performance.

Maintaining the dynamical microwave synchronization between a target and its background is the key to electromagnetical invisibility in real environment. Herein, we introduce an archetypical paradigm for ultraelastic films of graphene-functionalized ionic gel with tunable microwave-absorbing behaviors. Inspired by the local structural changes during the wing-spreading process of vespertilionids, the experimental and finite element simulations have revealed that proper shape changing of 3D wrinkled structure containing ridge walls with moderate impedance is the effective way to minimize reflected wave and promote energy attenuation. An optimal RL value of -43.6 dB and valid regulatory amplitude of 41.5 dB, covering a microwave-absorbing to shielding state, could be reached with only 0.2% weight fraction of the active ingredient RGO filler. The significant regulatory performance is attributed to the competitive effect between intrinsic dielectric attenuation of silicon nitride modified reduced graphene oxide (RGO-SiN), multiscattering of a 3D wrinkled structure, and evolution of the oriented RGO-SiN.