Biochar has attracted increasing attention as a carbon-negative material, including asphalt applications. On the one hand, its impact on the mechanical performance limits its application and might reduce pavement durability. On the other hand, biochar's microwave-absorbing properties can be used to enable crack healing. In this study, mineral aggregates in an asphalt concrete mixture were partially replaced with biochar at substitution levels of 0%, 2%, 4% and 8% by mass of aggregates. The microwave-induced heating behaviour, fracture resistance and healing performance under repeated damage-healing cycles were systematically investigated. Surface temperature measurements revealed that biochar enhanced microwave energy conversion into heat, although heating rates decreased slightly after repeated damage-healing cycles. Healing efficiency depended on biochar, binder, and air void content, which are closely interlinked. Mixtures containing 2% and 4% biochar by aggregate mass exhibited the highest healing ratios, whereas excessive biochar substitution (8%) resulted in a low and progressively declining healing performance. Notably, the reduction in heating rate under repeated treatment cycles did not affect healing efficiency. These results demonstrate that moderate biochar incorporation into asphalt can enhance microwave-induced healing without compromising cracking resistance, supporting its use in preventive maintenance strategies for asphalt pavements.

Microwave absorption and mechanical properties of integrated glass-carbon hybrid composites: Co-design of weaving mode and frequency-selective surface for X-band applications

Biomass-derived carbon-based composites, renowned for their extensive sources, low cost, low density, and unique pore structure, have garnered increasing attention as electromagnetic wave (EMW) absorbers. In this work, tangerine peel featuring a natural honeycomb porous structure was selected as the precursor to construct honeycomb porous carbon/Fe/Fe4N triphasic composites (Fe/Fe4N/PC) via facile freeze-drying and nitridation procedures. Specifically, the nitridation process under an NH3 atmosphere facilitates the in situ formation of Fe4N magnetic nanoparticles through the reaction between Fe and N species. The synergistic integration of the honeycomb porous structure, Fe/Fe4N magnetic particles, and biomass-derived carbon enriches the electromagnetic loss mechanisms, encompassing conduction loss, dipole polarization, magnetic loss, and multiple reflections. Consequently, the Fe/Fe4N/PC composites exhibit exceptional EMW absorption performance: the minimum reflection loss (RLm i n) reaches -55.93dB at a thickness of 2.6mm, and the maximum effective absorption bandwidth (EAB) achieves 5.41GHz at 1.7mm. Additionally, radar cross section (RCS) simulation results demonstrate that the Fe/Fe4N/PC composite prominently reduces the RCS signal by 42.6dB·m2 at 16°, confirming its superior practical stealth potential. This study provides insightful guidance for the design and eco-friendly fabrication of honeycomb porous structured absorbers, offering a strategy for developing high-performance and sustainable EMW absorbers.

ABSTRACT In this study, (Fe2O3/Y3Fe5O1 2)/MoS2 composites were successfully fabricated using an ultrasonic composite method. By precisely controlling the mass ratios of the constituent components, heterogeneous interfaces were engineered, and the complex dielectric constant was optimized, resulting in enhanced microwave absorption properties of the material. Experimental findings revealed that the YFMo-3 sample achieved a minimum reflection loss (RLmin) of −49.74 dB at 9.76 GHz, corresponding to an electromagnetic wave absorption efficiency of 99.998%. The sample YFMo-2 exhibits a minimum reflection loss (RLmin) of -47.18 dB at the 10.4 GHz frequency band, with an effective absorption bandwidth of 4.03 GHz – covering nearly the entire X-band – and all these performance metrics are achieved at an ultra-thin matching thickness of 3.0 mm. Comparative analyses demonstrated that the microwave absorption performance of YFMo-2 significantly surpassed that of the single-phase Y3Fe5O1 2/MoS2 composite with an equivalent ratio YMo-2. Analysis suggests that this advantage may stem from Fe2O3， increasing both the variety and quantity of heterogeneous interfaces within the composite material, thereby inducing more interface polarization phenomena. The present work offers a novel approach for optimizing yttrium iron garnet-based microwave absorbing materials and holds promise for advancing their practical applications in military-civilian integrated domains, such as electromagnetic stealth technology and electromagnetic compatibility of electronic devices.

Synergistic enhancement of microwave absorption, corrosion resistance, and mechanical properties in carbon fiber reinforced polymer-based high entropy nitride coatings via texture engineering

Wave absorption and mechanical properties of SiCf-SiO2f/SiC based on a Jaumann structure

Modulated magnetic and wideband tunable microwave absorption properties of multiferroic nanocomposite (BiFeO3)0.5(ZnO)0.5 in the matrix of multiwalled carbon nanotube (MWCNT)

Magnetic porous carbon foams, with low density, strong attenuation, and improved impedance matching, have been introduced as effective microwave absorbers to combat electromagnetic interference. In this study, morphology regulation of CoMn-MOF derived composites anchored on carbon foam were prepared by in situ growth and high-temperature pyrolysis. The pyrolysis temperature significantly influences the structural and chemical properties of the magnetic carbon foams. At a matching thickness of 1.45 mm, the material yielded a wide absorption bandwidth of 4.46 GHz, along with a minimum reflection loss of -51.54 dB at 1.55 mm. The excellent microwave absorption properties were contributed to the conductive loss, dipole polarization, interfacial polarization, natural resonance, exchange resonance, and impedance matching. The prepared magnetic porous carbon foams also integrate thermal insulation property. This work established a promising design strategy for advanced microwave absorbers that combine low density with high absorption efficiency, broadband absorption capabilities, and thermal insulation properties.

Preparation and electromagnetic microwave absorption properties of La(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3 high entropy perovskite powder

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Numerical characterization of the microwave absorbing properties of multilayer lattice structures containing heterogeneous Lattice core

Directionally pressurized filtrated nitrogen-doped CNTs/RGO/carbon hollow sphere/CoNi sandwich buckypaper with superflexible, high-strength mechanical, and excellent microwave-absorbing properties

ABSTRACT The escalating growth in telecommunication technology has led to a surge in electromagnetic pollution due to the increase in electronic devices. This not only impacts the performance of electronic gadgets but also poses risks to human health. To counteract electromagnetic pollution, researchers have extensively investigated microwave absorbers. As communication technologies predominantly operate in the microwave region, demand for efficient microwave‐absorbing materials is rising. Traditional metal‐based microwave absorber materials face limitations in terms of cost, density, corrosiveness, and rigidity, prompting attention to polymer‐based composites, among which polyurethane (PU) composites stand out for their exceptional properties, making them a favorable candidate for microwave absorption applications. This study explores the microwave absorption performance in the X‐band frequency (8.2–12.4 GHz) of PU nanocomposites containing graphene nanoplatelets (GNP) as a conductive filler and magnetite as a magnetic filler. Various loading percentages of GNP and magnetite were incorporated into both rigid polyurethane (RPU) and flexible polyurethane (FPU) matrices. The optimized composition of 2.5% GNP and 2.5% magnetite (1:1 ratio) exhibited superior microwave absorption properties, achieving a minimum reflection loss of −39.2 dB with an effective absorption bandwidth of 1.22 GHz in RPU, and −26.5 dB with an EAB of 1.52 GHz in FPU. These results highlight that the synergistic combination of conductive and magnetic fillers within PU matrices provides an efficient pathway for designing lightweight, cost‐effective, and high‐performance microwave absorbers.

Wheat straw, an abundant but underutilized agricultural residue, offers promise as a sustainable raw material for the development of eco-friendly microwave absorbers. In this study, wheat straw-based composites were fabricated and systematically investigated for their dielectric characteristics using the transmission line method. To enhance microwave absorption efficiency, multi-walled carbon nanotubes (MWCNTs) were incorporated at 2%, 4% and 6% loading levels, leading to significant improvements in both dielectric permittivity and loss. The electromagnetic absorption characteristics of all samples were evaluated through a combination of experimental methods and numerical simulations in CST Microwave Studio, using the measured dielectric parameters for model accuracy. The results demonstrate that MWCNT-modified wheat straw composites exhibit markedly higher absorption efficiency and broader effective bandwidth compared to unmodified counterparts with almost covering 95% of both X- and Ku-bands giving a minimum Reflection loss (RL) of −22.081 dB and −75.061 dB, respectively. These findings highlight the potential of MWCNT-enriched wheat straw composites as high-performance, environmentally sustainable microwave absorbers suitable for advanced electromagnetic interference (EMI) shielding applications in both X-band and Ku-band.

Synergistic enhancement of magnetic and microwave absorption properties in Ba substituted DyFeO3 perovskite

Dual-functional core–shell composites: Integrated microwave absorption and thermal management properties

Abstract The development of radar-absorbing coatings with excellent microwave absorption properties and high temperature resistance is significant. MoSi 2 is considered to be highly promising for microwave absorption applications due to its superior high-temperature performance and high conductivity. In this study, MoSi 2 /cordierite composite microwave absorbing coatings were prepared using plasma spraying technology. The effects of coating composition on phase composition and distribution, microstructure, and electromagnetic parameters were investigated. The results indicate that as the MoSi 2 content increases in the MoSi 2 /cordierite composite microwave absorbing coating, the shape of the absorber transitions from spherical to lamellar, increasing the dielectric constant of the coating. Among these, the coating with 25 wt% MoSi 2 exhibits the best microwave absorption performance due to its excellent impedance matching properties and electromagnetic wave attenuation characteristics. Its effective absorption bandwidth (EAB) reaches 1.6 GHz (d=1.2 mm), and the minimum reflection loss (RL min ) achieves -22 dB (d=1.6 mm).

ABSTRACT To address the poor microwave absorption performance of single‐component materials, rGO/Fe 3 O 4 /PPy and rGO/Fe 3 O 4 /PEDOT ternary nanocomposites with dual electromagnetic loss mechanisms were prepared via microemulsion polymerization, resulting in significantly enhanced microwave absorption properties. Analysis of their structural morphology and microwave absorption performance reveals that, in addition to dipole polarization induced by internal defects within the composites, conduction loss arising from conductivity differences between components, and interfacial polarization effects among multiple constituents, the granular morphology of PEDOT facilitates more effective integration with rGO and Fe 3 O 4 compared to the film‐like structure of PPy. This enhanced integration increases the number of microscopic interfaces within the rGO/Fe 3 O 4 /PEDOT ternary nanocomposite and augments its internal conductive network, thereby intensifying both conduction loss and interfacial polarization effects. Consequently, the rGO/Fe 3 O 4 /PEDOT composite exhibits the highest internal relaxation loss, the greatest dielectric loss value, and optimal microwave absorption performance. Its minimum reflection loss reaches ‐83.16 dB at a matching thickness of 3.4 mm and a frequency of 7.20 GHz, with an effective absorption bandwidth (reflection loss below ‐10 dB) of 4.58 GHz (ranging from 5.12 to 9.70 GHz).

ABSTRACT To enhance the electromagnetic stealth functionality of carbon fiber (CF)‐based thermoplastic composites, surface modification serves as a commonly employed approach. However, maintaining the structural integrity of modified layers under harsh processing conditions remains challenging, often compromising the functional reliability of the final composites. This work presents a heterogeneous architecture in which NiCo alloy nanoparticles are encapsulated within aramid nanofilm (ANF) and firmly attached to the CF surface. This configuration improves the interfacial adhesion between CF and polyamide 6 (PA6), while also counteracting the mechanical weakening caused by fiber damage during high‐temperature reduction. Furthermore, this architecture enhances the composite's impedance matching and electromagnetic wave attenuation capacity. The resultant ANF@NiCo‐CF/PA6 material demonstrated outstanding microwave absorption characteristics, attaining a minimum reflection loss of −60.73 dB and an effective absorption bandwidth of 4.9 GHz at only 1.5 mm in thickness. This modification strategy demonstrates excellent structural stability under composite processing conditions, offering a novel pathway for developing CF‐reinforced thermoplastic stealth composites with superior interfacial and functional properties.

This study evaluates the thermal behavior, dielectric properties, and metal volatilization potential of municipal solid waste incineration (MSWI) fly ash (FA) and air pollution control (APC) residues under microwave heating. Thermogravimetric analysis (TGA), combined with mass spectrometry (MS), and dielectric property measurements were employed to examine decomposition mechanisms and microwave absorption properties. TGA–MS revealed multi-step decomposition patterns, with early mass loss attributed to hydrated salts, followed by carbonate and sulfate breakdown. Zinc was released at both intermediate and high temperatures, depending on the sample composition. Dielectric measurements showed limited microwave responsiveness of raw ashes at low temperatures, with significant increase at high temperatures, particularly in sulfide- and Fe-rich samples. Microwave treatment with carbon-based additives improved heating rates and metal volatilization. Graphite provided the fastest heating due to high conductivity, while biochar achieved superior volatilization of Pb, Cd, Sb, and Zn owing to its reactive and porous structure. Blast furnace sludge (BFS) was less effective compared to other additives, although higher content partially enhanced heating and metal release. Despite high volatilization ratios of the most volatile metals, residues in some cases showed elevated Mg and Zn concentrations due to overall mass loss and retention in refractory phases.