Enhanced Microwave Absorption Performance Research Articles

Optimizing microwave energy utilization & heating efficiency: Comparative analysis of susceptor materials for enhanced microwave absorption performance

Susceptors are vital components in microwave heating systems, ensuring efficient, selective, and uniform heating while improving both energy utilization and time effectiveness in various microwave processing applications. The present investigation underlines the microwave absorption performance of various silicon carbide (SiC) susceptors during microwave hybrid heating. The current study also explores methods, including theoretical analysis, simulations, and experiments, to identify most suitable SiC susceptor materials for efficient microwave heating (high microwave absorbing and energy utilization efficiency). Among all susceptor materials, porous nitride-bonded SiC exhibited combination of high properties including permittivity (9.64), loss tangent (0.268), reflection loss (−13.32 dB) and attenuation constant (21.12 Np/m) when microwave heating carried at 1.2 kW, 900 s. Porous nitride-bonded SiC susceptor emerged as optimal choice for most appropriate susceptor material on the basis of theoretical analysis (reflection loss, impedance, microwave attenuation constant, dielectric properties) as compared to other susceptors. The microwave absorption mechanism of various SiC susceptor materials have been established and summarized. The microwave heating behaviour of various SiC susceptors with different compositions were analysed using COMSOL simulations. A higher microwave utilization efficiency was observed by COMSOL simulation for the porous nitride-bonded SiC (95 %) susceptor than dense nitride-bonded SiC (78 %), dense SiC (69 %) and dense oxide-bonded SiC (58 %). The excellent microwave absorption capability of porous nitride-bonded SiC susceptor can be ascribed to synergistic efforts of various polarization mechanisms: dipole polarization, interfacial polarization, multiple reflections and scatterings, defect-induced dipole polarization and conductive loss.

Non-iridescent magnetite photonic crystal films and pigments with enhanced magnetic coupling effect

Non-iridescent structural color films and pigments with novel enhanced microwave absorption characteristics are successfully fabricated at room temperature for the first time. The quasi-uniform magnetite nanoparticles (CV = 0.10 ∼ 0.20) with high refractive index (n = 2.42) and broad light absorption provide evident low-angle-independent property for the structural color pigments. More importantly, a universal technical protocol is developed for preparation of photonic crystals with inorganic nanoparticles, i.e., through designing of the binding strength between nanoparticles and mediated molecules, the slurry modulus is increased to 105 Pa, which effectively drives the nanoparticles to rapidly assemble into closely packed ordered arrays by our-designed powerful assembly technique. Additionally, the structural color materials are subjected as photonic crystal pigments (∼20 wt%) embedding in a transparent polymer matrix to form color coatings. Remarkably, the photonic crystal pigments exhibit strong magnetic coupling effect and enhanced microwave absorption performance due to the regular arrangement, with superior reflection loss (RLmin) values of −14.97 dB (increase by 65.8 % compared with randomized magnetic nanoparticles), and the effective absorption bandwidth (EAB) of 2.15 GHz. This new kind of photonic crystal pigment, combining visual color and radar wave absorption, provides a novel idea for developing of multi-wave-band high-performance stealth materials.

Ti3C2Tx/PANI/CoNi as a ternary composite material unveiling excellent microwave absorption performance

Ti3C2Tx MXene material exhibits exceptional dielectric properties and a distinct layered structure, making it a noteworthy microwave absorbing material. However, its microwave absorption performance is limited due to poor impedance matching and a single loss mechanism. To address these issues, this work develops a solvothermal method to introduce the magnetic component CoNi alloy and generate organic polymer PANI through in-situ polymerization, resulting in the preparation of Ti3C2Tx/PANI/CoNi ternary composites that significantly improve impedance matching and microwave absorption performance. The microwave absorption properties of the binary and ternary composites are compared, and the superior performance of the ternary composites is emphasized. Among the ternary composites, M-P-CN 3:1:8 exhibited an excellent microwave absorption performance, demonstrating a minimum RL value of −55.48 dB and an effective absorption bandwidth of 5.1 GHz at a thickness of 2.0 mm. The synergistic effect of multiple loss mechanisms, multilayer structures, and multiple interfacial polarization methods further contribute to the enhanced microwave absorption performance of ternary composites. This study provides a straightforward method for synthesizing and designing multi-component composite absorbing materials based on MXene.

Construction of iron oxide@C@Fe heterointerfaces by oxygen atmosphere heat treatment for enhanced microwave absorption performance

Carbon and iron-based materials are the two most extensively implemented microwave absorption materials. In this paper, carbon/iron-based wave absorption composite materials with tremendous dielectric and magnetic loss were successfully synthesized by carbonizing iron (Ⅲ) acetylacetonate (Fe(acc)3). The heterointerfaces were constructed by oxidation heat treatment to further regulate the dielectric loss and optimize the impedance matching of the composite, and improve the microwave absorption performance. Eventually, ultra-thin lightweight composite materials were prepared. When the thickness of the absorbing coating was only 1.01 mm, the minimum reflection loss (RLmin) value of the composite was −15.8 dB with 50 % filling. In addition, the effective absorption bandwidth (EAB) (RL ≤ -10 dB) was highly up to 8.8 GHz (9.2––18 GHz).

Enhanced microwave absorption performance of Fe3Al flakes by optimizing the carbon nanotube coatings.

Fe3Al is a good magnetic loss absorber for microwave absorption. However, due to the relatively high density and poor impedance matching ratio, the potential of Fe3Al cannot be fully released. Herein, a dielectric loss absorber of carbon nanotubes (CNTs) is coupled with Fe3Al to form Fe3Al/CNTs composite absorbers. CNTs are randomly tangled and coated on the surface of the Fe3Al flakes, forming a connecting conductive network. By carefully tuning the content of CNTs, the optimized Fe3Al/CNTs composite absorber with 1.5% of CNTs can combine both magnetic loss and dielectric loss mechanisms, thus achieving an impedance matching ratio close to 1 while keeping strong attenuation for enhanced microwave absorption. As a result, an effective absorption bandwidth (RL ≤ -10 dB) of 4.73 GHz at a thickness of 2 mm is achieved.

Constructing FeCoNiCrAl high entropy alloys with tunable nanograin size and crystal structure to boost polarization loss for enhanced microwave absorption performances

Constructing FeCoNiCrAl high entropy alloys with tunable nanograin size and crystal structure to boost polarization loss for enhanced microwave absorption performances

Core-shell Fe3Al@polypyrrole composites with tunable shell thickness and enhanced microwave absorption performance

Nowadays, core-shell structures have attracted considerable attention as microwave absorbers (MAs) due to the synergistic effect between dielectric and magnetic loss. Herein, core-shell Fe3Al@polypyrrole (Fe3Al@PPy) composites were successfully fabricated by the thermit reaction and chemical oxidation polymerization method with the assistance of ammonium persulfate and p-toluene sulfonic acid. Due to the regulation of the impedance matching by the electromagnetic coupling and core-shell structure, the Fe3Al@PPy composites showed enhanced electromagnetic wave (EMW) absorption performance compared with the pure Fe3Al. Furthermore, the thickness of the PPy shell increased from 0.23 µm to 1.50 µm as the addition of pyrrole (Py) increased from 0.25 mL to 1.0 mL. Meanwhile, the core-shell Fe3Al@PPy composites exhibited the optimal wave absorption performance when the PPy shell thickness was 0.80 µm, and the reflection loss (RL) could reach − 40.53 dB with the thickness of 2.0 mm at 13.3 GHz. This work provides a new idea for the design of large-scale electromagnetic (EM) coupled MAs with core-shell structures.

Space-Confined multiple interface in super-structured TiO2@PPy composite for enhanced electromagnetic wave absorption

Microwave absorption (MA) has become an important challenge with the development of electronic technology where fine structural design and interface modification of absorbing materials play a crucial role in optimizing their MA performance. In this study, hydrogenated hollow multi-shelled structure (HoMS) TiO2 (HH-T) was prepared using the sequential template method combined with hydrogenation treatment, followed by the synthesis of HH-T/PPy composite by in-situ polymerization. The HH-T/PPy composite possesses a uniform disordered interface and a uniform 3D conductive network. The HH-T/PPy composite exhibits an improved minimum reflection loss (RL) of −40.2 dB, and an effective absorption bandwidth (RL < -10 dB) of 5.02 GHz with a relatively thin matching thickness of 2.0 mm. The enhanced MA performance is mainly due to the excellent impedance characteristics, interface polarization, and conductive loss. This research offers new insights into the design and analysis of advanced microwave materials with superior performance.

Fabrication of the Fe-Doped Corona Schiff Base for Enhanced Microwave Absorption Performance.

A corolla-shaped Schiff base polymer was synthesized from terephthalaldehyde (TPAD), glutaraldehyde (GA), and p-phenylenediamine (PPD) by block copolymerization, and Schiff base iron complexes were formed by doping with FeCl3. The microscopic morphology, crystal structure, and elemental valence state were characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Comparing the change of conductivity before and after Fe3+ doping, it was found that the conductivity did not break away from the category of insulator, and the doped sample is a paramagnetic material. Morphological changes were observed by adjusting the ratio of GA to TPAD, and it was found that the corolla-like structure was most complete when the ratio of GA to TPAD was 2:1, and its Schiff base iron complex absorbed waves better. At a thickness of 3 mm, the absorption effect can reach below -10 dB at 12.44-15.16 GHz, and the maximum absorption value is -45.07 dB at a thickness of 3.8 mm; it is an organic absorbing agent with excellent impedance matching and absorbing properties.

Dual Resonance Behavior and Enhanced Microwave Absorption Performance of Fe3O4@C@MoS2 Composites with Shape Magnetic Anisotropy.

Ternary hierarchical Fe3O4@C@MoS2 composites and binary hierarchical Fe3O4@C composites were successfully fabricated by a modified mixed solvothermal method, a self-oxidation polymerization method, and a hydrothermal process. Their magnetic properties and microwave absorption performance were investigated. Dual resonance behavior was observed in the Fe3O4@C@MoS2 composites. One of the resonances was attributed to natural resonance with a resonance frequency of 2.58 GHz, which was much higher than that for Fe3O4 bulk (1.5 GHz). The other originated from the superparamagnetic/ferromagnetic relaxation with a resonance frequency of 12.45 GHz. The minimum reflection loss (RLmin) reached -64.30 dB with a matched thickness of 2.24 mm at 11.64 GHz, and the maximum effective absorption bandwidth (EABmax) covered 6.39 GHz with a matched thickness of 1.89 mm. In addition, the maximum Radar cross section (RCS) reduction value reached 31.90 dB m2 at a scattering angle of 0°. Electron holography analysis confirmed a dense magnetic absorption network in the Fe3O4@C@MoS2 composites. The boost in microwave absorption performance was caused by the synergistic effects of magnetic and dielectric properties owing to the ternary hierarchical structure, shape magnetic anisotropy, and incorporation of 1T/2H MoS2. Besides, the binary hierarchical Fe3O4@C composites also exhibited good absorbing performance caused by natural resonance, with an RLmin of -52.90 dB at 5.80 mm, an EABmax of 5.98 GHz at 3.38 mm, and a relatively high RCS reduction value of 13.04 dB m2 at θ = 20°. This work paves the way for designing multicomponent hierarchical absorbers with broadband and intensive microwave absorption.

Facile synthesis of FeNi nanoparticle-loaded carbon nanocomposite fibers for enhanced microwave absorption performance

The advantages of Fe, Ni metals and one-dimensional (1D) carbon materials are combined in this study using a simple method to prepare FeNi/C nanofibers for electromagnetic microwave (EM) absorption. The prepared FeNi/C nanofibers exhibit excellent EM absorption performance under dielectric/magnetic synergistic effect. At a frequency of 13.3 GHz, the minimum reflection loss (RLmin) reaches -57.15 dB, and effective absorption bandwidth (EAB) is as high as 4.0 GHz (12.5–16.5 GHz), with a thickness and filling rate of only 1.6 mm and 30 wt.%, respectively. Analysis shows that the EM absorption performance of FeNi/C nanofibers far exceeds that of single-component nanofibers and pure carbon fibers, and the excellent EM absorption performance is due to its unique microstructure and excellent electromagnetic properties. The FeNi alloy loaded on carbon nanofibers forms rich heterogeneous interfaces, and the three-dimensional (3D) conductive network composed of 1D carbon fibers increases the migration path of electrons. In addition, FeNi alloy, as an impedance regulation factor, strengthens the dielectricity of the carbon matrix while providing multidimensional magnetism, achieving impedance matching. This work is thought to contribute to the promotion of emerging absorbers by providing a novel strategy for the development of new 1D magnetic carbon-based high-performance EM absorbing materials.

Realizing optimized interfacial polarization and impedance matching with CNT-confined Co nanoparticles in hollow carbon microspheres for enhanced microwave absorption

The hollow porous structure with exceptional interfacial effect and customizable internal environment shows significant potential for application as electromagnetic shielding and absorption materials. However, designing hollow porous electromagnetic absorbers with both desirable impedance matching and high loss capability remains a challenge. Herein, 3D hollow porous electromagnetic microspheres were constructed by assembling 0D Co magnetic nanoparticles, 1D carbon nanotubes, and 2D carbon nanosheets. Due to the sufficient sites for Co2+ riveting, the high loading of magnetic carbon nanotubes (CoNC) and porous carbon spheres formed high-density interfaces, enhancing the interfacial polarization. Furthermore, high-density CoNC were grown in situ on the hollow porous carbon (HPC) microsphere, forming a highly dispersed 3D magnetic network that inhibited the aggregation of magnetic nanoparticles and enhanced magnetic coupling. Therefore, the as-prepared CoNC/HPC microspheres exhibited excellent microwave absorption (MA) performance, with a minimum reflection loss of -33.2 dB and an effective bandwidth of 5.5 GHz at a thickness of only 1.8 mm. The interfacial polarization mechanism for enhanced MA performance was demonstrated by electron holography and density functional theory calculations. Magnetic holography and micromagnetic simulations also revealed magnetic confinement and coupling mechanism. This work provides a new approach for designing electromagnetic absorbers with optimized impedance matching and loss capability.

Exceeding natural resonance frequency limit and enhanced microwave absorption performance of Fe3O4 nanorods coated with SiO2 layer

Fe3O4@SiO2 composites with different morphologies (hollow nanorods, porous nanorods, and flower-like nanoparticles) were constructed using different preparation methods. Considerably enhancement of resonance frequency and permeability beyond Snoek’s limitation were observed in the Fe3O4@SiO2 composites with shape anisotropy and porous core-shell nanostructure. The resonance frequency of porous Fe3O4@SiO2 nanorods enhanced to 4.21 GHz, which is much higher than the natural resonance frequency of 1.2 GHz for Fe3O4 bulk. The minimum reflection loss (RLmin) of Fe3O4@SiO2 porous nanorods reached -59.49 dB at 8.89 GHz, and its effective bandwidth (RL < -10 dB) covered 4.52 GHz at a thickness of 3.18 mm. In addition, the radar scattering cross section (RCS) reduction value reached more than 48 dBm2 after removing the background. Our study provides insight into the relationship between anisotropy, core-shell structure, morphology of nanoparticles and corresponding microwave performance, and provides a reference scheme for the fabrication of high-performance lightweight microwave absorbing materials.

Machine Learning‐Directed Fast and High‐Throughput Acquisition of High‐Efficiency Microwave Absorbents From Infinite Design Space

AbstractIntrinsic composition properties and extrinsic micro‐/nano‐structural effects constitute the infinite design space of microwave absorption (MA) materials wherein the high‐efficiency performance is expected to advance stealth and anti‐interference technologies. However, restricted to the black box of physical mechanisms, discovering those materials too often relies on the traditional trial‐and‐error methods, falling into the time‐consuming loop between material modification and performance measurement. Herein, an unprecedented machine learning‐based forecasting system (MLFS) is constructed to directly predict the process conditions of carbonyl iron/ferrosoferric oxide hybrids with enhanced MA performance. The high‐throughput screening and inverse projection based on pattern recognition recommend a series of excellent MA materials with the highest performance correlation coefficient up to 0.9844. After manual selection from this set, the enhancement of maximum absorption efficiency and bandwidth of the optimal hybrid reach 207% and 360% in comparison with the original database. The standardized MLFS procedure immensely shortens the research cycle to a few weeks compared to several months of the manual orthogonal experiment. This is believed to be an expressway for accelerating the discovery of high‐performance MA materials and their industrialization.

Enhanced microwave absorption performance of FeSiBCCr flake amorphous powder from ball milling

Enhanced microwave absorption performance of FeSiBCCr flake amorphous powder from ball milling

Constructing La-doped CoFe2O4/CNTs hybrids with urchin structure for enhanced microwave absorption performance

Constructing La-doped CoFe2O4/CNTs hybrids with urchin structure for enhanced microwave absorption performance

Exchange-coupled Core/shell Structure CoFe2O4@NiFe2O4/CNFs Composites with Enhanced Microwave Absorption Performance

One strategy to solve the electromagnetic pollution is proposed to fabricate electromagnetic wave absorption materials. The CoFe2O4@NiFe2O4/CNFs composites with magnetic exchange-coupled core/shell structure were synthesized by a facial solvothermal method. The CoFe2O4@NiFe2O4 particles with core/shell structure was anchored on surface of carbon nanofibers. Compared with CoFe2O4 /CNFs whose the minimum reflection loss is −39.17 dB at 15.45 GHz and the effective absorbing band is 3.32 GHz at 1.5 mm, the composite exhibits excellent microwave absorption performance that the minimum reflection loss at 12.32 GHz reaches −51.46 dB when the mass ratio of CoFe2O4 to NiFe2O4 is 3:1 and the thickness is 1.80 mm and the effective absorbing bandwidth reaches 3.85 GHz at 1.5 mm. The results indicate that the exchange coupling effect could enhance the electromagnetic wave absorption. Also, the content of NiFe2O4 could influence the properties if its content is too heavy, the exchange coupling effect will decrease and the impedance will be mismatched. Therefore, CoFe2O4@NiFe2O4/CNFs particles can be used as thin layer materials with strong absorption of low frequency microwave. The study provides a novel way to improve electromagnetic wave absorption properties based on exchange-coupled core/shell structure and the composition control.

Core-Shell Structured Silica-Coated Iron Nanowires Composites for Enhanced Electromagnetic Wave Absorption Properties.

In this study, we successfully prepared core-shell heterostructured nanocomposites (Fe NWs@SiO2), with ferromagnetic nanowires (Fe NWs) as the core and silica (SiO2) as the shell. The composites exhibited enhanced electromagnetic wave absorption and oxidation resistance and were synthesized using a simple liquid-phase hydrolysis reaction. We tested and analyzed the microwave absorption properties of Fe NWs@SiO2 composites with varied filling rates (mass fractions of 10 wt%, 30 wt%, and 50 wt% after mixing with paraffin). The results showed that the sample filled with 50 wt% had the best comprehensive performance. At the matching thickness of 7.25 mm, the minimum reflection loss (RLmin) could reach -54.88 dB at 13.52 GHz and the effective absorption bandwidth (EAB, RL < -10 dB) could reach 2.88 GHz in the range of 8.96-17.12 GHz. Enhanced microwave absorption performance of the core-shell structured Fe NWs@SiO2 composites could be attributed to the magnetic loss of the composite, the core-shell heterogeneous interface polarization effect, and the small-scale effect induced by the one-dimensional structure. Theoretically, this research provided Fe NWs@SiO2 composites with highly absorbent and antioxidant core-shell structures for future practical applications.

Structural engineering of double shells decoration for preparing a high-efficiency electromagnetic wave absorber

As 5G technology advances, so does the prevalence of harmful electromagnetic waves, and as a result, researchers have been progressively interested in developing materials that can absorb microwaves. So, it's become desirable to fabricate unique microwave absorbent materials (MAMs) to mitigate the negative effects of electromagnetic radiation and offer protection to biological beings and electronic data. Herein, we fabricated a novel HoFeO3@WSe2@SiO2 composite via the co-precipitation method. The microwave absorption properties of the HoFeO3,WSe2, SiO2 and HoFeO3@WSe2@SiO2 (with 25, 35 and 45 wt% loading) were examined in the X-band frequency range. 35 wt% filler loading shows reasonable reflection loss values with the broadest effective absorption bandwidth (EAB). The optimum impedance matching is responsible for the enhanced microwave absorption performance of the HoFeO3@WSe2@SiO2 with 35 wt% filler loading. In addition, the best sample is measured using both waveguide and free-space techniques and the results have been compared. The free-space method has been demonstrated to be an effective alternative testing strategy due to its contact-free and non-destructive features. Furthermore, the technique described in this study to design innovative HoFeO3@WSe2@SiO2 microwave absorbers can offer significant assistance with a wider absorption band. In this context, HoFeO3@WSe2@SiO2 is expected to be used as a highly efficient microwave absorbent.

Attapulgite coated polycrystalline iron fibers composites with light weight feature and enhanced microwave absorption properties

In this study, attapulgite coated polycrystalline iron fibers (ATP/IF) composites were prepared by layer-by-layer electrostatic self-assembly technology and aligned ATP/IF composite were prepared by shear-force. The complex permittivity decreases from 35 to 20 and permeability decreases from 1.3 to 1.15 at 2.6 GHz for ATP/IF-1 composite. Anisotropy electromagnetic properties were achieved by aligned ATP/IF composites. The microwave absorption properties show that broader bandwidth and better absorption efficiency were obtained by ATP/IF composite (the minimum RL values decrease to −35 dB, the absorption bandwidths with RL below −5 dB is 8.8 GHz at thickness of 1.8 mm for ATP/IF-4 composite), and the microwave absorption performance was further enhanced by aligned ATP/IF-1-A composite (the bandwidth increases to 7.5 GHz at thickness of 1.2 mm). Double-layer ATP/IF composite was designed and the microwave absorption performance show that broader bandwidth and better efficiency can obtained by adjusting the impedance matching characteristics and the absorption characteristics of ATP/IF composite. When d1 = 1.5 mm, d2 = 0.5 mm, the absorption bandwidth is 7.0 GHz from 7.0 to 14 GHz and the minimum RL value reach about - 30 dB, showing higher absorption efficiency and wider bandwidth compared to single-layer aligned ATP/IF composite. Lightweight absorbers with enhanced microwave absorption performance were obtained under a lower content of 40 wt% due to the ATP coating on the surface of IF and alignment of ATP/IF composites.