Microwave Absorption Properties Research Articles

Fixed-Point Atomic Regulation Engineered Low-Thickness Wideband Microwave Absorption.

Atomic doping is widely employed to fine-tune crystal structures, energy band structures, and the corresponding electrical properties. However, due to the difficulty in precisely regulating doping sites and concentrations, establishing a relationship between electricity properties and doping becomes a huge challenge. In this work, a modulation strategy on A-site cation dopant into spinel-phase metal sulfide Co9S8 lattice via Fe and Ni elements is developed to improve the microwave absorption (MA) properties. At the atomic scale, accurately controlling doped sites can introduce local lattice distortions and strain concentration. Tunned electron energy redistribution of the doped Co9S8 strengthens electron interactions, ultimately enhancing the high-frequency dielectric polarization (ɛ' from 10.5 to 12.5 at 12GHz). For the Fe-doped Co9S8, the effective absorption bandwidth (EAB) at 1.7mm increases by 5%, and the minimum reflection loss (RLmin) improves by 26% (EAB = 5.8GHz, RLmin = -46dB). The methodology of atomic-scale fixed-point doping presents a promising avenue for customizing the dielectric properties of nanomaterials, imparting invaluable insights for the design of cutting-edge high-performance microwave absorption materials.

Microwave-Assisted Synthesis of Few-Layer Ti3C2Tx Loaded with Ni0.5Co0.5Se2 Nanospheres for High-Performance Supercapacitors

Transition metal selenides have high theoretical capacities, making them attractive candidates for energy storage applications. Here, using the microwave-absorbing properties of the materials, we designed a simple and efficient microwave-assisted synthesis method to produce a composite made of nanospheres Ni0.5Co0.5Se2 (NCSe) and highly conductive, stable Ti3C2Tx MXene. The Ni0.5Co0.5Se2/Ti3C2Tx composites are characterized via scanning electron microscopy, X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. The findings indicate that 3D Ni0.5Co0.5Se2 bimetallic selenide nanospheres were uniformly loaded within the few-layer Ti3C2Tx MXene wrapper in a short period. The optimal NCSe/Ti3C2Tx−2 electrode can demonstrate a specific capacitance of 752.4 F g–1 at 1 A g–1. Furthermore, the asymmetric supercapacitor combined with activated carbon maintains a capacitance retention of 110% even after 5000 cycles. The method of directly growing active substances on few-layer Ti3C2Tx MXene will provide inspiration for the manufacture of high-pseudocapacitance supercapacitors.

Preparation and Microwave Absorption Properties of FeCoV/GO/Coupling Agent Composites in S Band

Preparation and Microwave Absorption Properties of FeCoV/GO/Coupling Agent Composites in S Band

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

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

Amorphous/Graphitic carbon phase engineering of Corrosion-Resistant Fe@C Core-Shell nanowires for optimized dipole polarization and enhanced microwave absorption

The study of designing and developing ferromagnetic nanocomposites with both microwave absorption (MA) and corrosion protection properties through microscopic heterogeneous interfacial engineering and crystal phase engineering remains challenging. In this study, Fe@C core–shell nanowires (FCNWs) are obtained by magnetic field-controlled in situ reduction method and annealing process to de-regulate the carbon shell thickness and carbon morphology. The enhancement of Fe-C heterogeneous relative interfacial effects and dielectric/magnetic response is revealed using density functional theory and simulated electromagnetic field distribution, and the modulation of the amorphous carbon/graphitic carbon ratio achieves the enhancement of dipole polarization in the low-frequency region. The FCNWs absorber had a minimum reflection loss (RLmin) of −47.6 dB at a thickness of 4.9 mm, and the maximum effective absorption bandwidth (EABmax) was achieved at 5.5 mm up to 4.0 GHz. In addition, the shielding effect of the graphitic carbon shell on the corrosion medium and the addition of additional electron conduction pathways allow the FCNWs absorber to obtain smaller corrosion currents and larger polarization resistances compared to Fe nanowires. Thus, modulation of atomic-scale heterogeneous interfaces and crystal phases has great potential in modulating the dielectric response.

Reinforcement of microwave absorption and thermal conductivity of polydimethylsiloxane achieved by metal-organic framework-derived carbon nanotube/boron nitride flake heterogeneous structure

Due to the rapid advancement of electronic devices towards miniaturization, high-integration, multi-functionality, high-power, and high-frequency, it is necessary to design thermal interface materials (TIMs) that possess exceptional thermal conductivity as well as good capabilities for absorbing electromagnetic waves. In this report, carbon nanotubes (CNTs) containing cobalt (Co) nanoparticles have been in-situ grown on the surfaces of boron nitride flakes (BNFs) using the Co nanoparticles as catalysts which formed by the high-temperature pyrolysis and reduction of zeolite-imidazolate skeleton. Then, a multifunctional heterogeneous structure of Co@CNT/BNFs has been developed with tunable microwave absorption (MA) property and high thermal conductivity, which can be applied to enhance the MA performance and thermal conductivity of polymers simultaneously. The minimum reflection loss can reach -46.6 dB and a broad absorption bandwidth of 5.92 GHz can be obtained when adjusting the content of Co@CNT/BNFs in the absorbers. Furthermore, the thermal conductivity of the polydimethylsiloxane measured using the transient hot-wire apparatus is 0.72 W/(m·K) when the content of Co@CNT/BNFs is 30 wt.%, exhibiting excellent heat dissipation performance in thermal management. This work is significant for investigating MA packaging and high thermally conductive TIMs for the electronic devices.

Synthesis and microwave absorption properties of AgVO3/Ag2CrO4 heterostructure in the K-band

Synthesis and microwave absorption properties of AgVO3/Ag2CrO4 heterostructure in the K-band

Electromagnetic radiation suppressor based on Co-Ti doped strontium lanthanum hexaferrite for Ku-Band applications

In this proposed work, we report Co-Ti doped Strontium-lanthanum M−type hexaferrites with general chemical formula, Sr0.85La0.15(CoTi)0.5Fe11O19 and Sr0.85La0.15(CoTi)0.75Fe10.5O19 prepared by citrate auto-combustion method. Complex permittivity, complex permeability and microwave absorptive properties of fabricated ferrite compositions were analysed in 12.4 to 18 GHz frequency range (Ku-Band). The XRD (X-ray diffraction) pattern of Co-Ti substituted compositions show single-phase M−type hexagonal ferrite indicating this co-substitution maintained the crystal phase structure. The grain diameter (average) decreased from 587 nm to 290 nm and 415 nm to 318 nm for ferrite samples with composition x = 0.50 and x = 0.75 respectively after 20 hours of ball-milling. The reflection loss (RL) exhibited the absorption bandwidth of more than 90 % (−10 dB) of value 2.41 GHz and 1.2 GHz for fabricated ferrites with chemical composition Sr0.85La0.15(CoTi)0.5Fe11O19 and Sr0.85La0.15(CoTi)0.75Fe10.5O19 respectively.. Both dielectric loss tangent and magnetic loss tangent contributed to enhance total loss tangent which represents microwave absorbing properties of the prepared ferrite samples. Reflection coefficient (S11) values for open circuit method also shows absorption bandwidth (−10 dB) of more than 90 % for these ferrites. Double layer electromagnetic absorber was simulated and observed improved reflection loss and absorption bandwidth. Therefore, these suggested ferrite samples have potential to be used as electromagnetic wave absorbing material of both single and double layer at higher frequency range.

Superparamagnetic nanocubes of Co and Cu co-doped Mn-based ferrites as microwave absorbing material

The requirement in resolving electromagnetic (EM) problems in stealth warhead technologies are excellent absorption ability, lightweight, and thin dimensions. In this direction, this study provides a straightforward hydrothermal one-pot method to synthesize superparamagnetic Mn-based ferrite co-doped with Co and Cu (MCCF), and the article presents its microwave absorption properties. Using cutting-edge techniques, the MCCF nanocomposite phase structure, morphological, superparamagnetic, and microwave absorption properties were measured and analyzed. MCCF-822 ferrite shows superparamagnetic properties simultaneously with a high Ms value 71.4 emu/g. Vector network analysis of MCCF-822 with 70 wt% loading demonstrates an effective absorption bandwidth (EAB) of 5.2 GHz with a maximum reflection loss (RLmax) of −19.2 dB at 2 mm thickness, and it spans almost 92.77 % frequency region (3.3–18 GHz range with RL < −10 dB) by varying thickness 1.7 mm–6 mm. At 60 wt% loading, it covers the whole X & Ku band with a thickness range from 2 to 9 mm with a good EAB of 4.3 GHz at 2.5 mm thickness with RLmax of −16 dB. The dual absorption bands are also present in MCCF-613, which increases the EAB with RLmax −52.99 dB at 9 mm, fulfilling the superparamagnetic properties. Thus, MCCF-822 is proposed as a cost-effective superior ferrite nanocomposite for microwave absorption applications.

Synergistic impact of nickel ferrite and titanium dioxide composites for improving microwave absorption in X-band

The present study focuses on the synthesis of composites with varying loading percentages of nickel ferrite and titanium dioxide using a mechanical alloy method. The developed composites underwent a comprehensive evaluation of various parameters, which yielded valuable insights. Among the developed composites, nickel ferrite and titanium composite with 50:50 wt% (NT-C) have emerged as a potential candidate for microwave absorbing material. Notably, NT-C exhibits excellent electromagnetic characteristics, with a minimum reflection loss (RL) of –33.34 dB at 9.6 GHz and −27.98 dB at 11.06 GHz, both achieved with a pallet thickness of 2.2 mm. The exceptional microwave absorption properties of this developed composite are a result of the synergistic interplay between impedance matching and strong electromagnetic energy attenuation capabilities. This finding, resulting from the synergistic incorporation of nickel ferrite and titanium dioxide phases, offers an effective pathway for developing a material capable of exceptional electromagnetic capabilities.

Superior microwave absorption properties of anisotropic Y2Fe16‒xCoxSi/paraffin composites by orientation tuning

Y2Fe16-xCoxSi/paraffin composites were prepared by three different orientation methods. The effect of these orientation methods and the magnetocrystalline anisotropy of Y2Fe16‒xCoxSi alloys on the electromagnetic parameters and the microwave absorption properties were investigated. The results demonstrated that orientation tuning improved the electromagnetic parameters and microwave absorption properties. Anisotropy in dielectric properties and magnetic properties of Y2Fe16-xCoxSi/paraffin composites were achieved by tuning the orientation of Y2Fe16-xCoxSi powders. The planar and conical anisotropic materials had superior microwave absorption properties than uniaxial anisotropic materials for the same orientation method. The Y2Fe16‒xCoxSi/paraffin composite had an effective absorption bandwidth of 8.4 GHz (9.6–18 GHz) and a reflection loss of ‒59.6 dB which can almost cover the X–Ku bands and exceed the performance of many reported absorbing materials, showing its great prospects for microwave absorption in the X–Ku bands.

High easy-plane anisotropy Y-Co intermetallic nanoparticles for boosting gigahertz magnetic loss ability

Soft magnetic materials with ferromagnetic loss abilities have been proven effective in solving gigahertz electromagnetic problems. However, it remains a challenge to synergistically improve their loss capacities and working frequencies due to the Snoek limit. Here, we proposed Y-Co nanoparticles with optimized magnetic anisotropy to break this limit and boost microwave absorption properties. As a result, the soft magnetic phases have manipulated the ferromagnetic loss ability, resulting in the improvement of the easy-plane anisotropy, thus increasing the resonance frequency. A loss peak at 6.2 GHz with a loss capacity (μ") of 0.74 can be found in soft magnetic phase-rich nanoparticles with easy-plane anisotropy, which is higher than that of hard magnetic phase-rich with easy-axis anisotropy (0.76, 4.3 GHz) and Co phase (0.4, 3.95 GHz) nanoparticles. The minimum reflection loss of it can reach −26.4 dB (6.85 GHz) with a broad effective absorption bandwidth of 4.35 GHz (5.85 ∼ 10.20 GHz). The present study provides intrinsic insight into the relationship between easy-plane anisotropy and magnetic loss ability, inspiring the design of high-frequency electromagnetic compatibility materials.

In Situ Synthesis of an Epoxy Resin Microwave Absorption Coating with Anti-Ultraviolet Aging Effects

A nanoparticle-anchored three-dimensional microsphere flower-structured layered double hydroxide (LDH) material with Fe3O4 particles was successfully prepared using simple hydrothermal and hot solvent methods. Micro-nanostructured Fe3O4@LDHs (SLF) composites balance microwave absorption, corrosion protection, and UV aging resistance. The minimum reflection loss value of SLF is −35.75 dB at 14.16 GHz, when the absorber thickness is 8 mm, and the absorption bandwidth at this frequency is up to 2.56 GHz for RL values less than −10 dB, while the LL is only 1 GHz. The SLF /EP coating has not only excellent microwave absorption performance but also excellent corrosion and UV aging resistance performance. The coating still has some anti-corrosion effect after 10 d of immersion. This work is intended as a reference for the development of new coatings with excellent microwave absorption properties as well as corrosion and UV aging resistance for wind turbine tower barrels (seaside wind power generation equipment) surfaces.

Recent research progress and prospect of graphene-based microwave absorbing materials

With the increasing use of electronic devices, electromagnetic wave pollution has become a hot topic of concern and discussion, and microwave absorption materials play an important role in civil and defense military fields. Therefore, the development of electromagnetic wave absorption materials with low density, thin thickness, wide effective bandwidth, and strong wave absorption performance has become the focus and goal of researchers. Graphene shows a unique two-dimensional structure, lightweight, large specific surface area, high electrical conductivity, and high thermal conductivity, which make it a promising electromagnetic wave-absorbing material. However, pure graphene material cannot meet the needs of practical applications due to bad impedance matching. Therefore, graphene is usually combined with other materials (such as carbon materials, magnetic metal, polymer, ferrite, and ceramic) to improve its wave absorption properties. In this review, we summarize recent research progress of different types of graphene-based microwave absorbing materials. In addition, the challenges and prospects for improving the microwave absorption properties of graphene-based composites are presented, which will be useful for those working in related fields.

Fast, non-carbonized, ambient-drying PVA/CNF@GO foam: Towards super-broadband microwave absorption and structural strength enhancement in aramid honeycomb

Lightweight structural/microwave absorption (MA) integrated materials with broadband MA are urgently needed in the aerospace field. In this study, crosslinked PVA/CNF backbone-supported RGO foams were successfully filled into aramid honeycomb structures with significant broadband MA performance and structural enhancement properties through a synergistic strategy of chemical crosslinking, environmental drying and chemical vapor reduction. Flexible tuning of the electromagnetic parameters of the PVA/CNF@GO foam can be achieved by adjusting the number of GO parts. The 30 mm thickness of the PVA/CNF@14GO foam achieves a broadband effective absorption of 13.25 GHz, covering almost all C, X and Ku bands. Microstructural characterization and electromagnetic parameter tests proved that the uniform distribution of RGO was achieved with crosslinked PVA/CNF as the backbone, which resulted in less Debye relaxation and the construction of uniform conductive pathways. Therefore, the PVA/CNF@14GO-filled honeycomb not only enables the composite honeycomb to achieve broadband MA performance, but also achieves a compressive strength of 5.52 MPa, which is an improvement of 262.86 % with respect to that of the pure honeycomb. The obvious overlap of the CST power loss distribution and the electric field distribution region shows that the conductive loss and the 1/4 wavelength interference are the main paths for energy dissipation in the composite of the PVA/CNF@GO-filled honeycomb. The honeycomb-filled PVA/CNF@GO lightweight foams obtained in this chapter have good broadband microwave absorption properties and higher structural strength, which provide important design strategies and practical references for the development of high-performance MA-filled honeycomb structures.

Microwave Absorption Properties of Flaky Carbonyl Iron @ Fe3O4 Produced by Plasma-Assisted Ball Milling

Microwave Absorption Properties of Flaky Carbonyl Iron @ Fe3O4 Produced by Plasma-Assisted Ball Milling

EVA copolymer loaded with PAni/CNT/GNP hybrids: A flexible and lightweight material with high microwave absorption

AbstractMicrowave‐absorbing materials are widely used for electromagnetic interference shielding and stealth technology. However, most existing materials are heavy, rigid, and expensive, limiting their practical applications. Therefore, there is a need to develop new materials that are flexible, lightweight, and cost effective. This study aimed to synthesize and characterize a novel ternary composite material based on polyaniline (PAni), carbon nanotubes (CNTs), and graphene nanoplatelets (GNPs) in an ethylene‐vinyl acetate (EVA) copolymer matrix. PAni‐based ternary composites were prepared by in situ polymerization of aniline in toluene dispersion of CNT/GNP hybrids and EVA. The microwave absorption properties were evaluated using a vector network analyzer in the frequency range of 8.2–18 GHz. The presence of as little as 0.8 wt% of CNT/GNP hybrid with appropriate mass ratio increased the conductivity by more than four orders of magnitude compared to the EVA@PAni blend. The minimum reflection loss corresponded to −40.55 dB at 16.31 GHz for the system containing CNT/GNP = 0.3:0.7, whereas those with CNT/GNP = 0.0:1.0 and 0.7:0.3 presented the widest effective absorption bandwidths (RL &lt; −10 dB), covering almost the entire Ku‐band. Due to the excellent flexibility, low weight, and high microwave absorption performance, these composites are potential candidates for microwave absorption applications.

Ferrite doped sucrose-derived porous carbon composites inspired by Pharaoh's Serpent for broadband electromagnetic wave absorption

This paper presents a straightforward and intriguing approach for designing wide bandwidth, lightweight, and tunable electromagnetic wave (EMW) absorbing materials. Drawing inspiration from the "Pharaoh's Snake", biomass carbon source and sucrose were used to fabricate Fe/Fe3O4@porous carbon (PC) composite materials through combustion experiments. Subsequently, high-temperature calcination was applied to enhance the microwave absorbing properties of the materials. The as-prepared composites demonstrate an impressive 6.62 GHz effective bandwidth and an excellent absorption ability of −51.54 dB at a matched thickness of 2.2 mm. Moreover, by tuning the content of magnetic particles and controlling the thickness of the composite material, comprehensive coverage across C, X, and Ku bands can be achieved. The outstanding performance suggests that the synthesized Fe/Fe3O4@PC porous materials hold significant potential for applications in electromagnetic wave absorption. It opens up a novel, straightforward, and cost-effective approach to acquiring broadband absorbing materials.

Microwave pyrolysis of waste biomass and synthesis of micro-mesoporous activated carbons: The role of textural properties for CO2 and textile dye adsorption

Hierarchical porous activated carbons (ACs) were efficiently synthesized in less than 2 min using microwaves and phosphoric acid (H3PO4), exhibiting excellent potential as adsorbent for carbon dioxide (CO2) and Methylene Blue (MB). The method emphasizes the development of selective physicochemical and textural properties crucial for CO2 post-combustion capture and textile dye removal from water, using agricultural waste as carbon precursor to address the environmental and economic challenges associated with the preparation of ACs. Dielectric properties confirmed H3PO4 increased the microwave absorption properties of the biomass. Employing a single-step method, the resulting ACs exhibited large specific surface areas exceeding 1000 m2g−1, achieved in less than 2 min and relatively low energies (2.4 GJ ton-1). Sample 0.4H4 displayed a surface area of 1145 m2g−1 and a significant ultra-micropore (<0.7 nm) content, demonstrating a CO2 uptake of 4.1 and 2.8 mmolg−1 at 0 and 25 °C, with high CO2/N2 selectivity (>38). The sample exhibited rapid CO2 uptake in 5 min and efficient regeneration after 20 adsorption–desorption cycles. Sample 0.3H3 developed large mesoporosity and a high surface area of 1217 m2g−1 with less than 3 min of treatment. The maximum dye removal was 281 mgg−1 and adsorption mechanisms involved diffusion into the mesoporous matrix, electrostatic interactions, H-bonding between AC and MB acid groups, and π–π interactions. The experimental data best fitted the Freundlich model. The results confirmed that microwaves have the potential to convert waste to micro-mesoporous ACs that can be used for a wide range of applications with significant processing time reductions and superior product qualities compared to conventional technologies.

CoN nanorods anchored on N-doped reduced graphene oxides for high-efficient microwave absorption performance

Nowadays, to solve the related electromagnetic radiation and pollution issues, it is urgent to exploit and design high-efficient microwave absorption materials, which owns the advantages of broad bandwidth, lightweight, thin matching thickness, and strong absorbing capacity. In this work, by anchoring CoN nanorods on the N-doped graphene nanosheets, a high-performance CoN/N-rGO hybrids microwave absorption absorber was fabricated with a two-step hydrothermal-nitridation method. Impressively, compared with the pure CoN nanorods, CoN/N-rGO hybrids present boosting microwave absorption properties which can be modulated by component of graphene. The strongest reflection loss (RL) value of CoN/N-rGO (40) hybrids absorber can reach -67.3dB at 12.4GHz with a thin matching thickness of 1.97mm and the effective absorption bandwidth (RL ≤ -10 dB) of 5GHz (10.4~15.4GHz) can be gained at only 1.79mm. This enhancement of microwave absorption is mainly attributed to the polarization, interface interaction, synergistic effect and optimal impedance matching between N-rGO nanosheets and CoN nanorods. This work provides not only a deep insight into adjusting the microwave absorption property of CoN/N-rGO hybrids, but a new route to design high-efficient nitride-based absorbers.