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The present work investigates the effect of process parameters on the microwave absorption performance of 3D printed continuous carbon fiber reinforced polylactic acid composites in the X‐band (8–12 GHz). The selection of process parameters in this work is based on an orthogonal experiment, explicitly focusing on the fiber orientation and printing temperature. The coupled effect between fiber orientation and printing temperature on the average absorptivity is further investigated by using response surface methodology (RSM), and the mechanism of these parameters on the microwave absorption performance is revealed, resulting in the optimal process parameters with a fiber orientation of 58.39° and a printing temperature of 230°C. The predicted average absorptivity is 0.525 and the mechanical properties of specimens corresponding to optimal parameters have been characterized. The experimental results demonstrate that the optimization of process parameters could lead to a significant improvement in the average absorptivity. Moreover, the microstructure observation shows that voids have the opposite effect on microwave absorption performance and mechanical properties. The above studies have specific guiding significance to the further application of 3D printed continuous fiber reinforced thermoplastic composites in structural absorbing materials. [ABSTRACT FROM AUTHOR]

The application of microwave heating technology can significantly enhance the water evaporation rate of emulsified asphalt mixtures post paving. To improve the microwave absorption and curing performance of these mixtures, SiC-Fe3O4 composite material (SF) was incorporated. This addition aims to enhance the microwave absorption efficiency and accelerate the curing process of emulsified asphalt mixtures under microwave heating. This study begins with an analysis of the microwave absorption principles pertinent to emulsified asphalt mixtures. Subsequently, the microwave heating temperature fields of ordinary emulsified asphalt mixture (EAM), SiC emulsified asphalt mixture (S-EAM), Fe3O4 emulsified asphalt mixture (F-EAM), and SiC-Fe3O4 emulsified asphalt mixture (SF-EAM) were simulated using COMSOL Multiphysics finite element software (COMSOL 6.2). The early strength variations in SF-EAM under different microwave heating durations were then examined through adhesion tests, leading to the proposal of a microwave heat curing process for SF-EAM. Finally, the wear resistance, water damage resistance, rutting resistance, and skid resistance of SF-EAM post-microwave curing were evaluated through wet wheel wear tests, wheel track deformation tests, and road friction coefficient tests. The results indicate that the optimal microwave heating time is 90 s, with the microwave absorption performance of the materials ranked as follows: EAM, S-EAM, F-EAM, and SF-EAM, from lowest to highest. The road performance of SF-EAM complies with specification requirements, and its wear resistance, water damage resistance, and rutting resistance are notably improved after microwave heating. [ABSTRACT FROM AUTHOR]

To address the challenges of slow curing speed and suboptimal microwave absorption during the paving of cold-mixed and cold-laid asphalt mixtures, this study introduces SiC-Fe3O4 composite material (SF) into emulsified asphalt mixtures to enhance microwave absorption and accelerate curing via microwave heating. Initially, based on the maximum density curve theory, an appropriate mineral aggregate gradation was designed, and the optimal ratio of emulsified asphalt mixture was determined through mixing tests, cohesion tests, wet wheel wear tests, and load wheel sand adhesion tests. Subsequently, the influence of SF content on the mixing performance of emulsified asphalt mixtures was analyzed through mixing and consistency tests. Finally, the microwave absorption performance of the mixture was evaluated by designing microwave heating tests under different conditions, using temperature indicators and quality indicators. The experimental results indicate that when SF content ranges from 0% to 4%, the mixing performance of the emulsified asphalt mixture meets specification requirements. The dosage of SF, SF composite ratio, and microwave power significantly impact microwave absorption performance, whereas environmental temperature has a relatively minor effect. The optimal mix ratio for the emulsified asphalt mixture is mineral aggregate:modified emulsified asphalt:water:cement = 100:12.8:6:1. The ideal SF dosage is 4%, with an optimal SiC to Fe3O4 composite ratio of 1:1, and a suitable microwave power range of 600–1000 W. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the continuous consumption of non-renewable resources, renewable biomass carbon material resources have attracted the researchers' attentions. In this paper, the easily available agaric was selected as the carbon source, to prepare biomass carbon materials by a high-temperature heat treatment. The effects of different heat treatment temperatures on the micromorphology and microwave absorption properties of materials were studied. Finally, the Structure performance relationship between micromorphology and absorption properties of materials was established. The conclusions can be summarized as follows: In agaric-derived biomass carbon materials, a large number of nanorods are intertwined, showing a jungle shape. The interior is rich in mesopores, which is due to the fact that the bound water and other trace elements contained in the material are removed by thermal evaporation during the carbonization process of high temperature heat treatment. The microwave absorption per-formance of the sample changes with the change of heat treatment temperature. When the heat treatment temperature is 700 °C and the thickness is 4.98 mm, the sample reaches the lowest reflection loss value of 41. 14 dB at the 11.33 GHz, and the effective absorption bandwidth is 0.75 GHz, which has the best electromagnetic wave absorption performance. [ABSTRACT FROM AUTHOR]

Considering the development of ultra-wideband detection technology, the effective attenuation performance of conventional electromagnetic absorbing materials prepared by component-morphology method is still affected by narrowband, which hinders its application. An effective strategy is to develop nanomagnetic metal absorbent that can effectively overcome skin effect through fine control based on nanotechnology. Mulberry-like Fe nanoparticles based on the self-assembly of spheroid blocks were synthesized in a simple chemical reduction process supplemented by a magnetic field. In view of synergistic loss of magnetic metal Fe, and unique physical properties of nanoparticles, the mulberry-like Fe nanoparticles exhibited attractive wave-absorbing properties. At a thickness of 3mm, the minimum reflection loss (RL) reaches −29.57dB, and the bandwidth less than −10dB reaches 8.38GHz, which covers the entire X-band, most of the C-band and part of the Ku-band. This will make it possible for electromagnetic protection and electromagnetic stealth. A possible growth mechanism was proposed to provide theoretical guidance for the subsequent preparation of nanomagnetic metal absorbent. [ABSTRACT FROM AUTHOR]

Synthesizing lightweight, thin–profile, and high–performance microwave absorbers has emerged as an urgent research topic. A promising strategy for carbon–based materials to achieve these attributes is to rationally construct heterostructures. Herein, 0.89–1.54 at.% nitrogen(N)–doped carbon onion nanotube chains (NCONCs) were produced by blending CONCs harvested from candle combustion with HH 4 Cl and subjecting them to heating at 300–400 °C for 3 h. The hinge–like NCONCs revealed numerous electron transport paths, facilitating the formation of multi–tiered conduction networks. The N–doping introduced C–N groups and interfaces into the CONCs, which yielded extensive dipole and interfacial polarization. Simultaneously, the 1.14 at.% N–doping endowed NCONC–400 with suitable conductivity, thereby ensuring excellent impedance matching. The resulting synergistic effect of impedance matching and electromagnetic wave attenuation was clearly observed. Specifically, NCONC–400 exhibited exceptional performance with a maximum effective absorption bandwidth of 4.71 GHz and a peak reflection loss of –35.47 dB at 1.4 mm. The radar cross–section reduction demonstrated by NCONC–400 composites reached 21.43 dB cm2. These impressive results prove the distinctive advantages of CONCs in tailoring performance and optimizing impedance matching, which are appealing for lightweight and efficient microwave absorbers. [ABSTRACT FROM AUTHOR]

The application of microwave heating technology can significantly enhance the water evaporation rate of emulsified asphalt mixtures post paving. To improve the microwave absorption and curing performance of these mixtures, SiC-Fe3O4 composite material (SF) was incorporated. This addition aims to enhance the microwave absorption efficiency and accelerate the curing process of emulsified asphalt mixtures under microwave heating. This study begins with an analysis of the microwave absorption principles pertinent to emulsified asphalt mixtures. Subsequently, the microwave heating temperature fields of ordinary emulsified asphalt mixture (EAM), SiC emulsified asphalt mixture (S-EAM), Fe3O4 emulsified asphalt mixture (F-EAM), and SiC-Fe3O4 emulsified asphalt mixture (SF-EAM) were simulated using COMSOL Multiphysics finite element software (COMSOL 6.2). The early strength variations in SF-EAM under different microwave heating durations were then examined through adhesion tests, leading to the proposal of a microwave heat curing process for SF-EAM. Finally, the wear resistance, water damage resistance, rutting resistance, and skid resistance of SF-EAM post-microwave curing were evaluated through wet wheel wear tests, wheel track deformation tests, and road friction coefficient tests. The results indicate that the optimal microwave heating time is 90 s, with the microwave absorption performance of the materials ranked as follows: EAM, S-EAM, F-EAM, and SF-EAM, from lowest to highest. The road performance of SF-EAM complies with specification requirements, and its wear resistance, water damage resistance, and rutting resistance are notably improved after microwave heating.

High-temperature electromagnetic wave (EMW) absorption materials are urgently needed for high thrust-to-weight ratio aero-engine. A novel EMW absorbing Si-C-N ceramic at elevated temperatures was fabricated by chemical vapor infiltration (CVI) Si 3 N 4 and SiC on 2D plain carbon fiber preform forming periodic framing and then oxidation to remove carbon fiber. The three-level gradient periodic microstructure was in-situ constructed in the Si-C-N ceramics to meet the impedance matching characteristics and effectively attenuate as much as EMWs. Compared with traditional EMW absorption materials, the Si-C-N ceramics with bidirectional periodic pore had a lower density of 1.2 g/cm3 and better frequency dispersion behavior which could obtain an effective absorption bandwidth (EAB) covering the whole X-band at 2.45 mm and the lowest reflection coefficient (RC min) of − 40 dB at 3.5 mm. The optimal Si-C-N ceramics (S2) show excellent EMW absorption performance over a wide temperature range. The Si-C-N ceramic had a promising applications at high temperatures. [ABSTRACT FROM AUTHOR]

Microwave technology is commonly used in many fields such as wireless communication and medical treatment, which are closely related to social development. However, electromagnetic pollution caused by microwaves is gradually increasing and the demand for high-performance microwave absorption materials is also increasing. Porous materials obtained by the pyrolysis of metal–organic frameworks (MOFs) at high temperatures exhibit good conductivity and magnetism, and the original skeleton structure of MOFs can be maintained; thus, MOF-derived materials can be considered viable candidates of microwave absorption materials. In this paper, Fe-CN@CoCN materials were prepared by pyrolyzing a ferrocene (Fc)-doped core–shell zeolite imidazole framework (Fc-ZIF-8@ZIF-67) at 700, 800, and 900 °C for 2 h in an Ar atmosphere. The obtained Fe-CN@CoCN-0.25-700 nanocomposite exhibited excellent microwave absorption (MA) performance with a minimum reflection loss (RLmin) of −42.27 dB at 5.68 GHz and an effective absorption bandwidth (EAB, RL < −10 dB) of 4.80 GHz at a thickness of 2.5 mm. The Fe-CN@CoCN-0.25-800 nanocomposite possessed optimized MA properties with an RLmin of −40.78 dB at 12.56 GHz and an EAB of 4.16 GHz at relatively low thickness of 2 mm. Fe-CN@CoCN nanocomposites are expected to be efficient materials for microwave absorption coatings. [ABSTRACT FROM AUTHOR]

Doping can introduce diverse interfaces and optimize impedance matching, making it a significant approach for enhancing the substrate's microwave absorption performance (MAP). Herein, a novel Ni-doped Ti 3 AlC 2 composite (x Ni-Ti 3 AlC 2 ; x = 0, 0.1, 0.2, 0.3) is successfully fabricated using pressureless sintering method. Partial replacement of Al atoms with doped Ni atoms leads to an improvement in permeability. Simultaneously, the substitution of Ni for Al and the formation of metal oxides (such as Al 2 O 3 , NiO, etc.) weaken the construction of conductive network, resulting in reduced conductivity and permittivity. The magnetic-dielectric synergistic effect significantly improves the impedance matching of Ti 3 AlC 2. Furthermore, the presence of multiphase interfaces and heightened defects results in an augmentation of both interfacial polarization and dipole polarization. Consequently, the 0.2Ni-Ti 3 AlC 2 demonstrates an outstanding MAP, with a minimum reflection loss (RL min) of -48.73 dB at 14.33 GHz and an effective absorption bandwidth (reflection loss < -10 dB) of 4.38 GHz (11.43-15.81 GHz) at a thickness of 1.72 mm, surpassing that of Ti 3 AlC 2. Moreover, the 0.1Ni-Ti 3 AlC 2 achieves a RL min of -65.07 dB, which is 4.24 times that of Ti 3 AlC 2. This study provides a valuable reference for assisting in the design and development of an absorber that capitalizes on magnetic-dielectric synergistic effect. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the Chinese Society of Rare Earths is the property of Editorial Department of Journal of the Chinese Society of Rare Earths and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To address the challenges of slow curing speed and suboptimal microwave absorption during the paving of cold-mixed and cold-laid asphalt mixtures, this study introduces SiC-Fe3O4 composite material (SF) into emulsified asphalt mixtures to enhance microwave absorption and accelerate curing via microwave heating. Initially, based on the maximum density curve theory, an appropriate mineral aggregate gradation was designed, and the optimal ratio of emulsified asphalt mixture was determined through mixing tests, cohesion tests, wet wheel wear tests, and load wheel sand adhesion tests. Subsequently, the influence of SF content on the mixing performance of emulsified asphalt mixtures was analyzed through mixing and consistency tests. Finally, the microwave absorption performance of the mixture was evaluated by designing microwave heating tests under different conditions, using temperature indicators and quality indicators. The experimental results indicate that when SF content ranges from 0% to 4%, the mixing performance of the emulsified asphalt mixture meets specification requirements. The dosage of SF, SF composite ratio, and microwave power significantly impact microwave absorption performance, whereas environmental temperature has a relatively minor effect. The optimal mix ratio for the emulsified asphalt mixture is mineral aggregate:modified emulsified asphalt:water:cement = 100:12.8:6:1. The ideal SF dosage is 4%, with an optimal SiC to Fe3O4 composite ratio of 1:1, and a suitable microwave power range of 600–1000 W.

Homogenously and densely dispersing small-sized magnetic particles into hierarchically porous carbon matrices is essential yet challenging for high-performance carbon-based microwave absorbers with balanced impedance matching and strong attenuation ability. Herein, we propose a general and scalable strategy by direct pyrolysis of solid polyvinylpyrrolidone (PVP) dissolved with metal (i.e., Fe, Co, and Ni) nitrates to prepare carbonaceous-magnetic hybrid absorbers. Benefiting from coordination interactions of carbonyl group-rich PVP molecules toward metal ions and the thermal foaming effect of PVP, the optimized CoNi-based composite material possesses a honeycomb-like architecture built by ultrathin (<2 nm) carbon nanosheets embedded with a high-loading (>50 wt%) of ultrafine CoNi alloy nanocrystals (an average size of ∼20 nm). Such structural characteristics endow the absorber with an ultralow tap density of 87.0 mg cm−3 and excellent microwave absorption performance with a superior reflection loss of −51.4 dB at a thickness of 2.6 mm and an effective absorption bandwidth of 7.2 GHz (10.5−17.7 GHz). Moreover, this synthesis methodology is universally applicable and can easily be extended to prepare carbon honeycomb composite absorbers decorated with other magnetic nanocrystals. [ABSTRACT FROM AUTHOR]

Exposure to electromagnetic radiation from digital devices, especially in the radio frequency range, affects human health in buildings. Furthermore, various electronic devices might be vulnerable to electromagnetic pollution in the same manner. Therefore, the electromagnetic interference (EMI) shielding technique is one of the electromagnetic compatibility (EMC) engineering phenomena that prevents the detrimental effects by means of electromagnetic pollution, especially in building areas. This work investigates the EMI shielding effectiveness and electromagnetic absorbing activities of plaster mortars containing various waste metals with different ratios. Measurements have been carried out in the frequency range of 8.2–12 GHz. Results concluded that the reference material shows the lowest total shielding effectiveness. The plaster mortar sample containing 20% iron, 3% steel, and 3% chromium showed the maximum EMI shielding effectiveness with a range of 20–24 dB. Measurement results indicated that the absorption capability is the dominant component of the total shielding effectiveness, except for the reference sample. Furthermore, the apparent porosity of each sample was analyzed. The maximum apparent porosity was obtained by chromium chips waste added sample. It was obtained that the iron waste chips increased the apparent porosity of samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe 3 O 4 nanoparticles/RGO sandwich composites were successfully prepared via a facile route. • This simple and convenient synthesis strategy consists of blast drying and roasting. • The content of Fe 3 O 4 nanoparticles in RGO nanosheets can be widely regulated. • The Fe 3 O 4 /RGO sandwich composites exhibit excellent microwave absorption performance. • This facile route to fabricate sandwich structure offers a new idea for designing graphene-based composites. Component regulation and microstructure design are two effective strategies to adjust electromagnetic parameters and improve the microwave absorption performance of materials. In this study, a facile synthesis strategy consisting of ultrasonic dispersion, blast drying, and roasting is proposed to build a sandwich-like graphene-based absorbent, in which Fe 3 O 4 nanoparticles with adjustable content are sandwiched uniformly between reduced graphene oxide nanosheets. The sandwich structure can form multiple interfaces, prevent the aggregation of nanoparticles, facilitate interface polarization, and endow the material with multiple electromagnetic loss mechanisms, which is very beneficial for impedance matching and microwave attenuation. Notably, the effective absorption bandwidth achieves 5.7 GHz, and the minimum reflection loss value is −49.9 dB. In addition, the synthesis process is simple and suitable for large-scale production and possible industrial applications. Thus, this facile route to fabricate sandwich-like graphene-based absorbents provides new ideas and approaches for designing new graphene-based nanocomposites. [ABSTRACT FROM AUTHOR]

In this study, Ag-decorated Ni@Cu powders were prepared by electroless plating method with Ni@Cu powders as the raw material. The various characteristics of the composite powders, such as their phase composition and structure, were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The effects of different Ag content on the size distribution of the particles were also studied by a laser particle size analyzer. The network vector analyzer additionally measured the electromagnetic properties of Ag-decorated Ni@Cu powders/paraffin samples. The electromagnetic wave absorption properties of the samples with different thicknesses were studied. The results of XRD and SEM show that with the increase of Ag content, the Ag plating effect of Ni@Cu powders increases first and then decreases. The results of laser particle size analyzer show that with the increase of Ag content, the particle size and distribution of Ag-decorated Ni@Cu powders become larger and wider. Through the analysis of the microwave absorption performance of Ag-decorated Ni@Cu powders/paraffin sample, it can be concluded that in the frequency range of 8.2–12.4 GHz, when the thickness is 2.6 mm, the Ag-decorated Ni@Cu powders with a silver mass ratio of 25 wt.% have good electromagnetic wave absorption performance. The reflection loss is less than −10 dB in the whole frequency range, and the peak value reaches −55.36 dB at 9.92 GHz. In addition, the frequency selective surface coupled by circular element and square ring element improves the microwave absorption performance of the sample containing 15 wt.% Ag content with 2 mm thickness. The reflection loss is lower than −10 dB with the peak reflection loss of −36.73 dB at 10.98 GHz in the whole frequency range. The simulation results show that the loading frequency selective surface can reduce the silver content and make it have better microwave absorption performance and low cost. Herein, Ag decorated Ni@Cu powders were prepared using a chemical reduction method, and Ag decorated Ni@Cu powders with varying Ag content were investigated. The optimal microwave absorption performance can be reached by tailoring the weight ratio of Ag. After incorporating with frequency selective surface (FSS), the absorption performance of Ag decorated Ni@Cu with low silver content is significantly enhanced. So, Ag decorated Ni@Cu powders combining with FSS is an effective way to prepare promising microwave absorption materials. [ABSTRACT FROM AUTHOR]

The application of carbon matrix and magnetic composites as electromagnetic wave absorbing materials has attracted extensive attention. The Co-MOF/Graphite nanoflakes (GNs) derived microwave absorbing material supported by MOF structure was acquired via hydrothermal method and subsequent calcination treatment. The best reflection loss value of the sample obtained by pyrolysis at 600 °C is −43.62 dB at 15.84 GHz, simultaneously, the thickness is only 1.6 mm, and the effective absorption bandwidth (EAB) can reach 5.2 GHz (12.8–18 GHz). The Co-MOF/GNs derivatives possess a thinner absorbent thickness and a rather wide EAB value (mainly distributed in the X and Ku bands). Its absorbing bandwidth and thickness of absorbing agent are far superior to most MOF-derived absorbing materials. Its excellent electromagnetic wave absorption performance is chiefly attributed to multi-component dipole polarization, interface polarization from multiple interfaces, and multiple reflection and scattering effects of sandwich micro-structure with high porosity on electromagnetic waves. This paper provides a certain reference value for the design of lightweight and efficient radar absorbers suitable for X and KU bands, which can be applied to radar absorbing materials, multi-band and various applications. [ABSTRACT FROM AUTHOR]

The magnetic (Ni 1-x Zn x Fe 2 O 4 /FeNi 3 (x = 0.5 and 0.7))/dielectric (ZnO) composites were designed as microwave absorbers. The composite absorbers with uniform phase distribution were in-situ prepared by mixing the precursor solutions of Ni 1-x Zn x Fe 2 O 4 and ZnO in solution combustion method. To tune the dielectric and magnetic properties, the amount of crystallized ZnO phase varied in the range of 0–54 wt % as a function of fuel contents and composition (x). The composite containing amorphous ZnO phase showed high microwave absorption performance, including a minimum reflection loss of −40 dB and effective absorption bandwidth of 3.4, 4, 3.8, and 1.8 GHz in Ku, X, C2, and C1 bands at matching thicknesses of 2.2, 3, 4.2, and 6.5 mm, respectively. [ABSTRACT FROM AUTHOR]

Metal–organic framework (MOF)-derived composites have gained wide attention due to their specific structures and enhanced performance. In this work, we prepared carbon nanotubes with Fe nanoparticles connected to two-dimensional (2D) hierarchical carbon network composites via a low-pressure gas–solid reaction strategy. Specifically, the three-dimensional (3D) networks derived from ZIF-8 exploited the carbon nanotubes with the function of charge modulation. Meanwhile, we utilized the interconnected 2D nanostructures to optimize impedance matching and facilitate multiple scattering, ultimately improving the overall microwave absorption performance. Furthermore, based on the well-designed structures, the composites prepared at 800 °C (Fe-N-C@CNTs-800) achieved the best reflection loss (RL) of −58.5 dB, thereby obtaining superior microwave absorption performance. Overall, this study provides a good groundwork for further investigation into the modification and dimension design of novel hierarchical microwave absorbers. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Due to the frequent use of electronic equipment, electromagnetic radiation pollution has become a prominent problem. The use of microwave-absorbing materials can effectively solve this phenomenon. In this study, flaky Dy2-xCo17Tbx alloy powders were prepared by vacuum smelting, and the microwave absorption performance was investigated by changing the Tb doping amount and matching thickness. The results show that the magnetic loss and dielectric loss are improved to a certain extent with the doping of Tb, and the absorption peak value moves to the low-frequency region. At the same time, the saturation magnetization (Ms) decreases with the increase in Tb doping. When x = 0.2 and the matching thickness is 1.6 mm, the minimum reflection loss (RLmin) value is −40.9 dB at 10.08 GHz, and the effective absorption bandwidth (EAB) is 1.6 GHz (9.28~10.88 GHz). In general, Dy2-xCo17Tbx alloy powders have good microwave absorption performance in the X band. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electromagnetic absorbent materials have received significant attention, recently, due to the growing concern about microwave contamination caused by widespread electronic devices. So, a lot of work has been done to develop advanced absorbing materials with excellent performance. Here, B i 2 S 3 decorated L a C o O 3 nanocomposite has been fabricated via a solvothermal method. To study the microwave absorption properties, L a C o O 3 @ B i 2 S 3 nanocomposites with 5, 15, 25, 35 and 40 wt% loadings were prepared. With optimal microwave absorption performance, a 35 wt% sample has decent minimum reflection loss (RL mini) with qualified frequency bandwidth (RL > 10 dB) covering nearly the whole X-band. Enhancements in microwave absorption efficiency of 35 wt% sample are ascribed to the highest dielectric loss, highest magnetic loss, maximum attenuation constant, as well as optimal impedance matching value. Furthermore, the optimal sample is tested via two measurement techniques; waveguide and free-space methods. A Comparison has been drawn between the variation of reflection loss measured by both methods. The free-space approach proves a good alternative measurement technique with contact-free and non-destructive benefits. Our findings may be useful in the design and fabrication of L a C o O 3 @ B i 2 S 3 nanocomposites for efficient microwave absorbers. [ABSTRACT FROM AUTHOR]

The electromagnetic pollution problem, particularly at microwave frequencies, poses a threat to not only sensitive technological gadgets but also to the health of humans. Therefore, there is a great need for lightweight and highly effective microwave-absorbing materials (MAMs). Here, we fabricated a hierarchical flower-like MoSe 2 structure and a rod-like MnFe 2 O 4 @MnO 2 architecture via a solvothermal method. Single-layer and bilayer samples were fabricated to study the microwave absorption feature. In single-layer samples, the flower-like MoSe 2 structure has better microwave absorption properties than the rod-like MnFe 2 O 4 @MnO 2 architecture. And in bilayer absorbing samples, a sample with a flower-like MoSe 2 structure as the top layer shows high absorption performance. Moreover, in bilayer samples, changes were made to the thickness of both layers to find the best parameters. An optimal bilayer sample has been achieved with a flower-like dielectric MoSe 2 structure as a top layer having a 1 mm thickness and magnetic MnFe 2 O 4 @MnO 2 as a bottom layer also with a 1 mm thickness; indicating that a strong absorption can only be attained by balancing dielectric loss and magnetic loss. Moreover, the optimal sample shows decent absorption with an effective absorption bandwidth (EAB) of 5.4 GHz (14.7–9.3 GHz) with a 1 mm thickness of each layer. The simulated results of the optimal sample have also been compared with experimental results. These results suggest a different approach for developing MAMs in the future. [ABSTRACT FROM AUTHOR]

To prepare lightweight, wideband, strong absorption and low-cost microwave absorbing materials, carbon black/polylactic acid (CB/PLA) composite filaments were prepared using a high-energy mixer and twin-screw extruder. Coaxial ring test pieces were printed by fused filament fabrication (FFF) technology with polylactic acid as the matrix and carbon black as the absorbent. The crystal texture and micromorphology of the composites were observed by XRD and SEM. The electromagnetic parameters were measured at 2–18 GHz using a vector network analyzer. The influence of CB content on the absorbing performance of the composites was studied, and the loss mechanism was explained. The results show that when the CB content (refers to PLA) is 25%, the composite has suitable impedance matching, conduction loss, and polarization loss, resulting in the best microwave absorption performance. The minimum reflection loss reached −45.47 dB at 13.68 GHz, and the corresponding effective absorption bandwidth was 5.36 GHz (10.72–16.08 GHz) with a matching thickness of 2.1 mm. At the same time, the density of the composite was only 1.19 g/cm3. This work sheds light on the development of lightweight and high-efficiency microwave absorption materials (MAMs) in a simple and low-cost manner. [ABSTRACT FROM AUTHOR]

Developing high-performance microwave-absorbing microscale materials is still a challenge for practical anti-electromagnetic interference applications. Herein, a facile strategy for constructing carbon nanotubes (CNTs)/FeSiAl flake composites through in situ growth of CNTs on FeSiAl microscale flakes is developed. The Fe nanoparticles on the oxide surfaces of the FeSiAl flakes serve as catalyst for CNTs. The amount and size of CNTs is adjusted by the reaction temperature and time. Thanks to the optimal interface between CNTs and FeSiAl, the flake morphology of the FeSiAl alloy and the porous structure of dielectric CNTs, proper impedance match, improved microwave absorptivity, increased attenuation ability and enhanced loss capability result in good microwave-absorbing behavior, demonstrating an effective absorption bandwidth of 3.52 GHz (12–15.52 GHz) with 1.7 mm, and minimal reflection loss of −47.32 dB at 9.12 GHz and 2.4 mm. This work provides an effective method for designing and preparing high-performance microscale microwave absorbents. [ABSTRACT FROM AUTHOR]

Fe–based metallic microwires possess unique microstructure and size effects, exhibiting favorable mechanical, electrical, and magnetic properties, thus distinguishing them as a possible agents for use as microwave absorbing materials. In this paper, the absorbing properties of Ni–doped Fe–based metallic microwires optimized by orthogonal experiments were investigated, and based on the optimal parameters, the influencing mechanism of the Ni doping amount on the absorbing properties was further analyzed. It was noted that at the frequency f = 8.36 GHz, the maximum reflection loss RL and electromagnetic wave absorption efficiency Aeff can reach −54.89 dB and 99.999%, respectively. Moreover, the Ni doping amount could result in the improved wave-absorbing properties of composites, obtain the corresponding optimal parameters, and even change the position of the maximum absorption peak, which are all of great significance for practical engineering applications. [ABSTRACT FROM AUTHOR]

• Two-dimensional multilayer MnFe 2 O 4 /MXene composites using a hydrothermal method to enhance electromagnetic wave absorption. • By reducing the particle size, we were able to increase the electromagnetic wave absorption capability of MnFe 2 O 4. The pure MnFe 2 O 4 material achieved a minimum reflection loss (RL min) value of −40.5 dB at a thickness of 2.85 mm when the hydrothermal temperature was set at 110 °C. • To further enhance the dielectric loss of MnFe 2 O 4 , we introduced high-surface-area MXene into the composite. The optimal RL min value of the MnFe 2 O 4 /MXene composites reached −49.5 dB at a thickness of 3.55 mm, surpassing the performance of individual MnFe 2 O 4 and MXene materials. • The coupling effect between MnFe 2 O 4 and MXene, which promotes coupling mechanisms, interface polarization, and impedance matching. The study of building materials with electromagnetic wave absorbing properties to minimize electromagnetic wave interference and enhance communication and efficiency while ensuring a cleaner, healthier, and sustainable future has gained significant attention. The traditional MnFe 2 O 4 material, known for its strong magnetic loss, has been widely used in the field of absorbing electromagnetic waves. However, its lower dielectric loss has hindered further development in this area.In this study, we aimed to design two-dimensional multilayer MnFe 2 O 4 /MXene composites using a hydrothermal method to enhance electromagnetic wave absorption. By reducing the particle size, we were able to increase the electromagnetic wave absorption capability of MnFe 2 O 4. The pure MnFe 2 O 4 material achieved a minimum reflection loss (RL min) value of -40.5 dB at a thickness of 2.85 mm when the hydrothermal temperature was set at 110 °C.To further enhance the dielectric loss of MnFe 2 O 4 , we introduced high-surface-area MXene into the composite. The optimal RL min value of the MnFe 2 O 4 /MXene composites reached -49.5 dB at a thickness of 3.55 mm, surpassing the performance of individual MnFe 2 O 4 and MXene materials. This enhanced attenuation of electromagnetic wave absorption can be attributed to the coupling effect between MnFe 2 O 4 and MXene, which promotes coupling mechanisms, interface polarization, and impedance matching. [Display omitted] [ABSTRACT FROM AUTHOR]

Metamaterials, typically consisting of sub-wavelength metal-atom arrays and a dielectric layer matrix such as glass fiber reinforced epoxy resin (FR-4), have been widely used in the field of stealth equipment due to their good electromagnetic parameter designability and strong absorption for electromagnetic waves at specific frequencies. In offensive and defensive confrontations, laser weapons pose a serious threat to the survival of stealth equipment. However, the interaction mechanism between the metamaterials and laser and the effect of laser ablation on microwave absorption performance are still unclear. In this work, we firstly irradiated the double arc-shaped Cu-atom array/FR-4 matrix metamaterials by using a high-energy continuous-wave laser and studied the interaction and response mechanism between them. The high temperature caused by laser irradiation leads to the melting of the metal atoms and the pyrolysis of the resin matrix. By simulating and testing the reflection loss of the metamaterials before and after irradiation, we found that the resin pyrolysis products strongly affect the impedance matching characteristics and reduce the microwave absorption properties significantly in extreme cases. Our findings help deeply understand the interaction between the metamaterials and the laser and will show guidance in the applications involving laser-metamaterial interactions.

Carbon-based microwave-absorbing materials with a low cost, simple preparation process, and excellent microwave absorption performance have important application value. In this paper, biomass-based carbon fibers were prepared using cotton fiber, hemp fiber, and bamboo fiber as carbon sources. Then, the precise loading of NiFe2O4 nanoparticles on biomass-based carbon fibers with the loading amount in a wide range was successfully realized through a sustainable and low-cost route. The effects of the composition and structure of NiFe2O4/biomass-based carbon fibers on electromagnetic parameters and electromagnetic absorption properties were systematically studied. The results show that the impedance matching is optimized, and the microwave absorption performance is improved after loading NiFe2O4 nanoparticles on biomass-based carbon fibers. In particular, when the weight percentage of NiFe2O4 nanoparticles in NiFe2O4/carbonized cotton fibers is 42.3%, the effective bandwidth of NiFe2O4/carbonized cotton fibers can reach 6.5 GHz with a minimum reflection loss of −45.3 dB. The enhancement of microwave absorption performance is mainly attributed to the appropriate electromagnetic parameters with the ε' ranging from 9.2 to 4.8, and the balance of impedance matching and electromagnetic loss. Given the simple synthesis method, low cost, high output, and excellent microwave absorption performance, the NiFe2O4/biomass-based carbon fibers have broad application prospects as an economic and broadband microwave absorbent. [ABSTRACT FROM AUTHOR]

Graphene-based microwave-absorbing materials (MAMs), especially graphene aerogels (GAs), have attracted tremendous attention because of their excellent characteristics. Three-dimensional (3D) GA materials exhibit a complex porous network structure, which is conducive for enhancing the loss capacity because of multiple reflections and scatterings. Compared to the typical two-dimensional graphene-based absorbing materials, GA materials with a special 3D network and an internal porous structure can solve the phenomenon of graphene sheet layer agglomeration and impedance mismatch, achieving better electromagnetic absorption characteristics. Combining the magnetic materials with GA can realize an ultrawide-band electromagnetic response and improve the microwave absorption (MA) performances of the 3D GA composites. Herein, we summarize the theories of MA and the recent progresses in magnetic GA materials. On this basis, we propose the perspectives and challenges of magnetic GA MAMs and discuss the multifunctional absorbing materials. [ABSTRACT FROM AUTHOR]

In this study, green cellulose nanofibers-based composites were successfully prepared for efficient wide-band electromagnetic absorber to realize functional and high-value diversified utilization of cellulose nanofibers. Specifically, by the introduction of reduced graphene oxide (RGO) and flower-like copper sulfide (CuS) into CNFs used as raw material, CNFs/RGO/CuS porous composite microwave absorber were obtained. The CNFs/RGO/CuS porous composite exhibited excellent microwave absorption performance due to its unique three-dimensional porous flower-like structure and heterogeneous interface, which provided excellent impedance matching and attenuation capabilities. The fabricated CNFs/RGO/CuS composite exhibited a minimum reflection loss (RLmin) of − 49.71 dB at 11.52 GHz and a maximum absorption bandwidth of 5.30 GHz (from 10.40 GHz to 15.70 GHz) at only 2.50 mm. In addition, the scanning electron microscope (SEM) results showed that the CNFs/RGO/CuS composite had a porous microstructure. And the Brunauer–Emmett–Teller (BET) specific surface area of the CNFs/RGO/CuS composite was 326.46 m2/g. Potential absorption mechanisms were proposed considering the interfacial polarization, impedance matching, and dielectric losses caused by the synergistic effects among CNFs, RGO, and CuS. This work proposed a new strategy to biomass-based functional materials, and used the natural polymer CNFs, compounded with reduced graphene oxide and copper sulfide, to achieve efficient microwave absorbing materials. In this paper, CNFs, GO and CuS were mixed and reacted. Graphene oxide sheets were reduced by the reducing agent VC to produce CNFs/RGO/CuS composite. The CNFs/RGO/CuS composite with the continuous structure with layers and pores formed a new absorbing channel, which enabled better transmission and multiple reflections of incident electromagnetic waves. The special micro-nanostructure and the smaller proportion of CNFs/RGO/CuS porous composite achieved a good impedance matching effect, thus improving its microwave absorption performance. [ABSTRACT FROM AUTHOR]

SiC fiber reinforced ceramic matrix composites (SiC f -CMCs) have been widely used as structural-functional materials at high temperatures. However, their mechanical and electromagnetic wave (EMW) absorbing properties will deteriorate due to high-temperature oxidation. Therefore, unique sandwich structure, consisting of inner Si 3 N 4 impedance layer, middle porous SiOC loss layer and dense oxidation-resistant Si 3 N 4 layer, was proposed to enhance multiple material properties in oxidation environment. Herein, SiC f /Si 3 N 4 –SiOC–Si 3 N 4 composites was fabricated by alternating chemical vapor infiltration (CVI) and polymer infiltration pyrolysis (PIP) methods. For these composites, SiC fiber is used as both reinforcing phase and electromagnetic (EM) absorber. CVI Si 3 N 4 matrix was distributed in inner and outer layer of the SiC f /Si 3 N 4 –SiOC–Si 3 N 4 composites. While inner Si 3 N 4 layer between BN interphase and SiOC matrix forms nano-heterogeneous interphase to consume EM energy and enhance mechanical properties of composites, outer dense and oxidation-resistant CVI Si 3 N 4 coating serves to maintain properties. PIP SiOC matrix exhibits porous structure that can effectively deflect cracks and achieve multiple scattering of EMW. SiC f /Si 3 N 4 –SiOC–Si 3 N 4 composites with sandwich structure demonstrated excellent EMW absorbing properties and mechanical performance in high-temperature oxidation environments. [ABSTRACT FROM AUTHOR]

High entropy spinel ferrite (HEF) nanoparticles were synthesized by solution combustion method as high-performance microwave absorbers. The structural, microstructural, magnetic and microwave absorption properties of (MnNiCuZn)1−xCoxFe2O4 powders (x = 0.05, 0.1, 0.2, and 0.3) were studied as a function of Co contents by modern characterization methods including X-ray diffractometry, Raman spectroscopy, electron microscopy, vibrating sample magnetometry, and vector network analyzer. The as-combusted powders were single phase with the space group of Fd3¯m. The cation distributions showed that the fraction of Fe3+ cations in (A) sites decreased with the substitution of Co cations. The (MnNiCuZn)0.7Co0.3Fe2O4 nanoparticles (~30–70 nm) were dispersed on the graphene sheets. The coercivity increased from 94 to 225 Oe with the Co contents, while the saturation magnetization slightly changed in the range of 67–71 emu/g. The saturation magnetization and coercivity of the (MnNiCuZn)0.7Co0.3Fe2O4/graphene composite powders were lower than those of (MnNiCuZn)0.7Co0.3Fe2O4 powders due to their smaller particle size. The (MnNiCuZn)0.7Co0.3Fe2O4/paraffin composite sample at the mass fraction of 70 wt.% showed the maximum reflection loss of −27 dB at the matching thickness of 5.3 mm in Ku band. The interfacial relaxation and ferromagnetic resonance were determined as main dielectric and magnetic loss mechanisms, respectively. By compositing the (MnNiCuZn)0.7Co0.3Fe2O4 powders with graphene, the maximum reflection loss of −16 dB at the matching thickness of 4.5 mm in Ku band was obtained at the lower mass fraction of 30 wt.% because of the higher dielectric loss of graphene.

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. [ABSTRACT FROM AUTHOR]

Fe3O4/reduced graphene oxide (RGO) composite powders were prepared by solution combustion synthesis method. The effects of fuel type; glycine and urea; on the structure, microstructure, magnetic, and microwave absorption properties were characterized by modern methods. A mixture of α-Fe2O3 and Fe3O4 phases was obtained by the urea fuel, while the glycine fuel led to the pure Fe3O4 phase. The scanning and transmission electron microscopy showed the Fe3O4 nanoparticles were distributed on the ultrathin RGO sheets. With the addition of RGO, the saturation magnetization increased up to 84 emu/g due to the higher amounts of the magnetite phase. The Fe3O4/RGO composite powders synthesized by the urea fuel showed a reflection loss (RL) of −28 dB with effective bandwidth of 1.4 GHz in the C1 band at the matching thickness of 3.7 mm. However, the pristine Fe3O4 powders prepared by the glycine fuel had higher absorption properties, including higher RL of −33 dB and broader bandwidth of 3 GHz in the Ku band at the matching thickness of 1.2 mm. In addition to the higher magnetic and dielectric losses, the higher microwave absorption performance was attributed to the better impedance matching property caused by the porous microstructure.

• MnFe-C core–shell nanoparticles were prepared with tunable Mn/Fe ratios. • The magnetic and microwave absorption of MnFe-C nanoparticles were well controlled. • Optimal reflection and effective absorption bandwidth values are −35.2 dB and 5.0 GHz, respectively. Metal-C nanoparticles with MnFe nanocores and their microwave absorption performances with design Mn/Fe ratios have been rarely reported in previous studies. In this work, MnFe-C core–shell nanoparticles with tunable Mn/Fe ratios were prepared by a one-step metal organic chemical vapor deposition method. It was found that the magnetic properties and microwave absorption performances of the nanoparticles could be well tunable by designing Mn/Fe ratios in their nanocores. These results suggest that the as-synthesized MnFe-C core–shell nanoparticles have great potential for microwave absorption applications. [ABSTRACT FROM AUTHOR]

In this work, CoFe 2 O 4 powders were combined with various amounts of MXene (Ti 3 C 2 T x) through the solution combustion method for microwave absorption applications. Despite the absence of MXene reflections in X-ray diffraction patterns, the MXene sheets were observed in electron microscopy images. The CoFe 2 O 4 nanoparticles were uniformly dispersed on the MXene nanosheets. The specific surface area increased from 57 to 83 m2 g−1 by adding 20 wt% MXene. The saturation magnetization and coercivity decreased from 44 to 35 emu g−1 and from 834 to 775 Oe, respectively. By adding the MXene, the minimum reflection loss and effective absorption bandwidth increased up to −38 dB and 5.6 GHz at a matching thickness of 1.8 mm, respectively, which was attributed to the enhancement of impedance matching by the decrease of permittivity. • CoFe 2 O 4 /Ti 3 C 2 T x composite powders were prepared by solution combustion synthesis method. • The saturation magnetization of the CoFe 2 O 4 -20 wt %Ti 3 C 2 T x compiste was similar to the pristine CoFe 2 O 4 powders. • By adding the MXene, the microwave absorption performance enhanced by improving the impedance matching. [ABSTRACT FROM AUTHOR]

Metal–organic framework (MOF)-derived composites have gained wide attention due to their specific structures and enhanced performance. In this work, we prepared carbon nanotubes with Fe nanoparticles connected to two-dimensional (2D) hierarchical carbon network composites via a low-pressure gas–solid reaction strategy. Specifically, the three-dimensional (3D) networks derived from ZIF-8 exploited the carbon nanotubes with the function of charge modulation. Meanwhile, we utilized the interconnected 2D nanostructures to optimize impedance matching and facilitate multiple scattering, ultimately improving the overall microwave absorption performance. Furthermore, based on the well-designed structures, the composites prepared at 800 °C (Fe-N-C@CNTs-800) achieved the best reflection loss (RL) of −58.5 dB, thereby obtaining superior microwave absorption performance. Overall, this study provides a good groundwork for further investigation into the modification and dimension design of novel hierarchical microwave absorbers.

Fe 3-x Zn x O 4 (x = 0.1, 0.2, and 0.3) powders were synthesized by facile combustion method using metal nitrates as oxidants and glycine as fuel. The structural, microstructural, magnetic, and microwave absorption properties are characterized as a function of Zn2+ substitution. With the increase of Zn2+ contents, some hematite (α-Fe 2 O 3) phases appeared together with the magnetite (Fe 3 O 4) phase. The transmission and scanning electron microscopy observations showed that the particle size was decreased from 120 to 70 nm, while the amount and size of pores increased with adding Zn2+ cations. The as-synthesized Fe 2.9 Zn 0.1 O 4 powders had the highest saturation magnetization of 92 emu/g, which decreased to 72 emu/g for the Fe 2.7 Zn 0.3 O 4 sample. The Fe 2.8 Zn 0.2 O 4 sample exhibited an intense reflection loss of −53 dB in the K u band at the matching thickness of 2 mm. Despite the reduction of reflection loss, the effective bandwidth increased up to 5.5 GHz with the Zn content, which is attributed to the better impedance matching and higher contribution of magnetic and dielectric loss mechanisms. [ABSTRACT FROM AUTHOR]

The rapid development of electronic information technology has promoted the use of a large number of high-frequency electronic equipment, which has led to increasingly serious electromagnetic interference (EMI) problems caused by disordered radiation. At present, for the 2–18 GHz microwave frequency band, it is still a huge challenge to develop high-efficiency absorbing materials with ultra-wide absorption band (>7 GHz) under thin thickness (<3 mm). Here, we propose a new strategy to achieve lightweight and high-efficiency microwave absorption by constructing hierarchical special structures. The melamine foam template was coated with a carbon/nickel/cobalt organic precursor by a hydrothermal process using a water/ethanol mixed solvent, and then annealed in an inert atmosphere at a high temperature to obtain a bimetallic nanoarray composed of nickel/cobalt embedded three-dimensional carbon foam (BNA/3dCF). This new type of absorbing material completely retains the structure of the melamine foam template, greatly enhances the conduction ability of micro-currents, and provides a large number of scattering sites for electromagnetic wave conduction. Interestingly, the protection of the carbon layer effectively avoids the oxidation of the bimetallic nanoarray, so that the BNA/3dCF retains the good dielectric properties of the carbon foam and has excellent magnetic properties, and improves the impedance matching and magnetic loss capabilities. With matching thicknesses of 2.2 mm and 3.9 mm, BNA/3dCF can respectively obtain an ultra-wideband microwave absorption of 7.16 GHz and a minimum reflection loss of −57.84 dB. We believe that through the macro/meso/micro multi-scale precise control of the absorbing material, it is an effective solution to enhance its absorbing performance. [Display omitted] • Realize the precise control of the structure on multiple scales. • The bimetallic nanoarray structure was completely preserved. • BNA/3dCF is light enough to be easily held up by a four-leaf clover. • BNA/3dCF-2 achieved an effective bandwidth of 7.16 GHz at 2.2 mm. [ABSTRACT FROM AUTHOR]

We adopted a green, economical and simple method in which konjac glucomannan (KGM) was used as a carrier to support CNTs to construct a three-dimensional structure filled with epoxy resin to improve the absorbing performance of epoxy resin. Through the reflection of the internal multi-level pore structure and the dielectric loss effect of CNTs, the dissipation and absorption of electromagnetic waves are realized. This KGM derived CNTs foam exhibits high specific microwave absorption performance with a minimum absorption of −25.2 dB at 11.3 GHz and a qualified bandwidth of around 2.89 GHz (RL⩽ −10 dB), which is achieved by KDCF5/Epoxy with the coating layer thickness of 1.8 mm. We provide a novel and cost-effective method to achieve excellent absorbing performance under thin thickness and low load. The CNTs foam also has a lower density (6.5 mg/cm3) and can improve the absorbing properties of the epoxy while maintaining its various advantages, thereby expanding the application range of the epoxy resin. [ABSTRACT FROM AUTHOR]

The derivatives of metal‐organic frameworks (MOFs) in which various metal and/or metal oxides are uniformly distributed in porous carbon materials have attracted considerable attention owing to their special characteristics such as large specific surface area, adjustable pore structure, highly ordered pores, and uniform metal sites. Presently, the electromagnetic absorption property of MOF derivatives is primarily enhanced by changing their metal ions, and it is still a challenge to improve the loss ability of MOF‐derived absorbers by modifying the organic ligands of MOFs. In this work, rhombic Nd2O2S/C nanocomposites with excellent microwave absorption (MA) performance are synthesized via in‐situ pyrolysis of (Nd[TDA][CH3COO][H2O])n (H2TDA: 2,5‐thiophenedioic acid). The influence of pyrolysis temperature on the MA performance of the composites is examined. The Nd2O2S/C‐800 composite exhibits a minimum reflection loss of –52.3 dB at 2.56 mm thickness, which is ascribed to the synergistic effect of multiple loss mechanisms, including polarization, conduction loss, and so forth. Overall, this paper provides a useful method to synthesize high‐performance MA materials by utilizing MOFs with rare‐earth ions connected by sulfur‐containing organic ligand. [ABSTRACT FROM AUTHOR]

Structural design and composition control are crucial in determining the EM wave attenuation of an absorber; however, the balancing of the EM parameters has always been a formidable challenge. Here, we successfully designed a 3D hierarchical Co/carbon nanosheets (CNS)/rGO magnetic-dielectric composite with controllable composition and microstructure as a high-efficiency absorber by using a three-step route. Benefiting from the synergetic effect and heterogeneous interfaces, the hierarchical Co/CNS/rGO composite displayed strong microwave attenuation and broad absorption frequency band. Furthermore, the nanocomposite with porous structure promoted multiple reflection and scattering, thereby improving the attenuation capacity. The hierarchical Co/CNS/rGO composite exhibited strong microwave absorption capabilities when the filler loading was 20 wt%. Specifically, the maximum reflection loss (RL) was up to −65.5 dB at 12.4 GHz with a matched thickness of 2.5 mm and the corresponding absorption bandwidth was 8 GHz. Such excellent results not only serve as an inspiration for the enhancement of interfacial polarization of an absorber, but they also provide a novel avenue to synthesize high-efficiency microwave absorber with controllable structural design and composition regulation. [Display omitted] [ABSTRACT FROM AUTHOR]

To prepare lightweight, wideband, strong absorption and low-cost microwave absorbing materials, carbon black/polylactic acid (CB/PLA) composite filaments were prepared using a high-energy mixer and twin-screw extruder. Coaxial ring test pieces were printed by fused filament fabrication (FFF) technology with polylactic acid as the matrix and carbon black as the absorbent. The crystal texture and micromorphology of the composites were observed by XRD and SEM. The electromagnetic parameters were measured at 2–18 GHz using a vector network analyzer. The influence of CB content on the absorbing performance of the composites was studied, and the loss mechanism was explained. The results show that when the CB content (refers to PLA) is 25%, the composite has suitable impedance matching, conduction loss, and polarization loss, resulting in the best microwave absorption performance. The minimum reflection loss reached −45.47 dB at 13.68 GHz, and the corresponding effective absorption bandwidth was 5.36 GHz (10.72–16.08 GHz) with a matching thickness of 2.1 mm. At the same time, the density of the composite was only 1.19 g/cm3. This work sheds light on the development of lightweight and high-efficiency microwave absorption materials (MAMs) in a simple and low-cost manner.

Fe–based metallic microwires possess unique microstructure and size effects, exhibiting favorable mechanical, electrical, and magnetic properties, thus distinguishing them as a possible agents for use as microwave absorbing materials. In this paper, the absorbing properties of Ni–doped Fe–based metallic microwires optimized by orthogonal experiments were investigated, and based on the optimal parameters, the influencing mechanism of the Ni doping amount on the absorbing properties was further analyzed. It was noted that at the frequency f = 8.36 GHz, the maximum reflection loss RL and electromagnetic wave absorption efficiency Aeff can reach −54.89 dB and 99.999%, respectively. Moreover, the Ni doping amount could result in the improved wave-absorbing properties of composites, obtain the corresponding optimal parameters, and even change the position of the maximum absorption peak, which are all of great significance for practical engineering applications.

Carbon-based microwave-absorbing materials with a low cost, simple preparation process, and excellent microwave absorption performance have important application value. In this paper, biomass-based carbon fibers were prepared using cotton fiber, hemp fiber, and bamboo fiber as carbon sources. Then, the precise loading of NiFe2O4 nanoparticles on biomass-based carbon fibers with the loading amount in a wide range was successfully realized through a sustainable and low-cost route. The effects of the composition and structure of NiFe2O4/biomass-based carbon fibers on electromagnetic parameters and electromagnetic absorption properties were systematically studied. The results show that the impedance matching is optimized, and the microwave absorption performance is improved after loading NiFe2O4 nanoparticles on biomass-based carbon fibers. In particular, when the weight percentage of NiFe2O4 nanoparticles in NiFe2O4/carbonized cotton fibers is 42.3%, the effective bandwidth of NiFe2O4/carbonized cotton fibers can reach 6.5 GHz with a minimum reflection loss of −45.3 dB. The enhancement of microwave absorption performance is mainly attributed to the appropriate electromagnetic parameters with the ε’ ranging from 9.2 to 4.8, and the balance of impedance matching and electromagnetic loss. Given the simple synthesis method, low cost, high output, and excellent microwave absorption performance, the NiFe2O4/biomass-based carbon fibers have broad application prospects as an economic and broadband microwave absorbent.