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The global focus on electromagnetic interference and pollution is undeniable. To counter these challenges, high-performance microwave-absorbing materials (MAMs), typically composed of dielectric and magnetic components, offer effective solutions by ensuring favorable impedance matching. Leveraging these MAMs has proven beneficial across various sectors, including 5G technology, information security, energy harvesting, diminished radar cross-section, and advancements in military applications. We successfully synthesized composites of La 1.5 Sr 0.5 NiO 4 (LSNO) and SrFe 12 O 19 (SrM) composites through ball milling and heat treatment. With the escalation of SrM weight percentage in the composites, noticeable alteration in structural, morphological, and static magnetic characteristics was ensured. Moreover, the amalgamation of these components bolstered the EM properties, consequently yielding exceptional microwave absorption capabilities in the composites. The composites with 40, 60, and 80 wt% of SrM (named S4, S6, and S8) exhibited excellent microwave absorption performance with an absorption rate of over 99.9 % for a thin thickness. The S4 and S8 composites attained reflection loss (RL) values of −34.75 dB and −36.93 dB, with 2.0 and 1.6 mm thicknesses, respectively. Meanwhile, the S6 composite achieved an RL value of −44.24 dB with a thickness of 1.9 mm. These composites' outstanding microwave absorption performance can be attributed to their significant magnetic loss, remarkable dielectric loss, and synergistic effects. [ABSTRACT FROM AUTHOR]

In this study, the technology important Cu 0.5 Mn 0.5 Fe 2 O 4 and Cu 0.5 Mn 0.5 Fe 1.80 RE 0.2 O 4 (RE = La, Gd, Nd, and Dy) nanoferrites were synthesized via sonochemical method and characterized to overcome the electromagnetic pollution problems. Crystalline, morphological, electrical, magnetic, and microwave-absorbing parameter were identified by doping of RE (La, Gd, Nd, and Dy) in Cu 0.5 Mn 0.5 Fe 2 O 4 nanoferrites. The XRD analysis revealed a cubic spinel structure with a single-phase composition for Cu 0.5 Mn 0.5 Fe 2 O 4 nanoferrites whereas Cu 0.5 Mn 0.5 Fe 1.80 RE 0.2 O 4 (RE = La, Gd, Nd, and Dy) nanoferrites had a cubic structure with the presence of a secondary phase. SEM images confirmed the spherical shape of the particle and the grain size within the range of 19.25–28.19 nm, with elemental stoichiometry confirmed by EDS spectra. The dielectric constant and conductivity of Cu 0.5 Mn 0.5 Fe 1.80 RE 0.2 O 4 nanoferrites were low at higher frequencies, which lead good candidates for microwave-absorbing technologies. The substitution of RE decreases saturation magnetization (43.38–23.96 emu/g) and squareness ratio values of prepared nanoferrites were less than 0.5. The SE T values of the prepared nanoferrites were in the range of 32.31–41.81 dB. The minimal reflection loss (RL) values of Cu 0.5 Mn 0.5 Fe 2 O 4 and Cu 0.5 Mn 0.5 Fe 1.80 RE 0.2 O 4 nanoferrites were less than 10 dB and which indicated that the prepared nanoferrites possessed great potential for applications as microwave-absorbing materials. [Display omitted] • The dielectric properties of Cu 0.5 Mn 0.5 Fe 2 O 4 nanoferrites were enhanced by doping of RE (La, Gd, Nd, and Dy). • Magnetic behaviors of Cu 0.5 Mn 0.5 Fe 2 O 4 were tuned by doping of RE (La, Gd, Nd, and Dy) ions. • The SE T values for the LCMFO, GCMFO, NCMFO, and DCMFO nanoferrites are 41.81, 44.23, 49.24 and 54.92 dB, respectively. • RE (La, Gd, Nd, and Dy) doped nanoferrites showed good RL values (−23.62, −32.57, −39.729, and −45.520 dB) in the X-band frequency. [ABSTRACT FROM AUTHOR]

A multiferroic composite that comprises of a non‐ferromagnetic ferroelectric material with a high dielectric constant and a non‐ferroelectric ferromagnetic material with a high magnetostriction is of tremendous interest as microwave absorption material due to its applicability in tunable microwave phase shifters, resonators, filters, absorbers, etc. In the previous work, the solid solution of strontium titanate and sodium bismuth titanate (Sr0.5(Na0.5Bi0.5)0.5TiO3, SNBT50), which is observed to possess a very high dielectric constant at room temperature (Ferroelectrics, Vol 583, 252–263 [2021]), is successfully reported. Thus, in this work, a core–shell magnetoelectric composite is prepared by coating highly ferromagnetic and magnetostrictive cobalt ferrite onto a diamagnetic but strongly ferroelectric SNBT50 to enhance its magnetic properties and to investigate the modification in microwave absorption. Detailed characterization of electric and magnetic parameters in microwave frequency range (1–20 GHz) reports substantial enhancement in the magnetic permeabilities as well as the magnetic loss of the composite system, as opposed to bare SNBT50. This results in improved impedance matching in the system and enhanced microwave absorption, with a minimum reflection loss (RL) of −20.19 dB and an increased effective absorption bandwidth of 4.56 GHz at a mere 2.7 mm absorber length. Consequently, in this investigation, a promising pathway is established for the development of multiferroic composites with favorable magnetoelectric coupling at room temperature that possesses wide absorption bandwidth and suitable RL, making them highly suitable for use in multiferroic‐based microwave components. [ABSTRACT FROM AUTHOR]

In this study, a cement-based composite was prepared using reduced graphene oxide (RGO) as a raw material via an ethanol liquid-phase mixing pre-dispersion process. The microstructure of cement-based composites with varying RGO contents was discussed, and a systematic investigation was conducted into the electromagnetic wave absorption (EWA) performance of RGO-cement composites within the frequency range of 2–18 GHz. The results indicate that the RGO content significantly impacts its wave absorption performance. Notably, at an RGO content of 3.0 wt%, the wave absorption performance experiences substantial enhancement. For instance, the minimum reflection loss (RLmin) of −48.33 dB at 8.9 GHz with a coating thickness of 2.6 mm is achieved, while an effective absorption bandwidth (EAB) of 5.02 GHz is attained with a thickness of only 1.6 mm, covering nearly the entire Ku-band. The incorporation of high specific surface area RGO into cement materials results in abundant interface polarization losses and additional electromagnetic wave transmission paths, effectively boosting the EWA performance. Consequently, these materials exhibit significant potential for applications in the field of electromagnetic wave shielding. [ABSTRACT FROM AUTHOR]

Microwave-absorbing materials (MAMs) represent a class of functional materials endowed with the capability to dissipate electromagnetic waves by converting them into thermal energy. Silicon carbide (SiC) is one of the most extensively used dielectric materials for achieving efficient microwave absorption. However, the single polarization behavior and poor electrical conductivity of SiC significantly constrain its application in microwave absorption. To address this limitation, various modification techniques, including the incorporation of ceramics, carbonaceous, magnetic, and polymeric materials, are employed in conjunction with SiC to enhance its microwave absorption properties. Geometrical variations, such as employing SiC with variable crystal structures, sizes, and shapes, along with structural alterations in the composite morphology, such as core-shell composites, have proven instrumental in achieving enhanced microwave absorption behavior. Additionally, mixing SiC with other materials contributes to improved performance. The preparation of SiC composites involving various filler particles, combined with structural modifications, facilitates the activation of various absorption mechanisms. These mechanisms encompass parallel plate capacitance, multiple scatterings, multiple reflections, interfacial polarization, defect-induced dipole polarization, and magnetic loss. This review article delves into various recently developed SiC-based composites, discussing their absorption mechanisms that yield significant microwave absorption behavior. Furthermore, this article also introduces the application of ranking techniques such as TOPSIS and VIKOR, based on microwave absorption properties, to evaluate and compare these composites. [ABSTRACT FROM AUTHOR]

The present study focuses on the use of waste materials to generate cost-effective microwave absorption composites. Rice husk (agricultural waste) and exhausted activated charcoal (water filter cartridge waste) were used as waste materials for microwave absorption. Both were blended in different proportions using a planetary ball mill to prepare samples. The XRF and particle size studies were carried out for element and particle size analysis, and for dielectric properties measurement, a vector network analyzer was used. The findings reveal the microwave absorption in the frequency range of 2 to 18 GHz by the blended composites. Sample RHC-11 with 20% exhausted activated charcoal showed a maximum reflection loss of − 38.3 dB at 12 GHz. For further improvement in microwave absorption, the dielectric characteristics of the composites were utilized to develop a layered metamaterial-based microwave absorber. The layered metamaterial is a unique and simple patch design that displays good microwave absorption > 90% and absorbs 99.34% of microwave energy at 16 GHz frequency. The developed metamaterial-based microwave absorber shows an absorption bandwidth of 6.60 GHz with a thickness of 2.3 mm. In addition, the proposed structure is independent of the oblique incidence angle and polarization angle. [ABSTRACT FROM AUTHOR]

Nickel substituted Sr–Co nano spinel ferrites with composition Sr 0.5-x Ni x Co 0.5 Fe 2 O 4 (0.0, 0.1, 0.2, and 0.3) were prepared with the help of a sol-gel auto combustion route. The prepared materials were sintered at 800 for four and a half hours. Analysis of XRD confirmed that the material is composed of a cubic spinel structure with a single phase, and its space group is Fd-3m. Rietveld refinement of X-ray diffraction data was done for all prepared compositions using FULLPROF software. As the composition under study contains more nickel than lattice constant, crystalline size, X-ray density, and bulk density decrease. The dielectric properties were observed about frequency. The dielectric properties revealed that dielectric loss, dielectric constant, and ac conductivity decrease with increasing the Ni2+ content. The activation energy (ΔE) was calculated from the slope of Arrhenius plots. The ΔE found in the range of 0.580–0.096 eV. The analysis of XPS was carried out to examine the elemental state of annealed samples. The prepared material is suitable for employment in applications involving high frequencies because the Ni-doped Sr–Co ferrites with the greatest Ni2+ concentration have the lowest dielectric loss, dielectric constant, and tangent loss value. [ABSTRACT FROM AUTHOR]

This study utilizes the strong complexation effect of polydopamine on metal ions and constructs multilayer carbon magnetic heterostructures on the surface of carbon fibers through the in situ reduction method, thereby obtaining a new type of multilayer carbon‐based composite absorbing material. The absorption properties at different layers were analyzed and compared through various characterization methods. Finally, the double‐layer structure demonstrated outstanding electromagnetic wave absorption characteristics, exhibiting a wide effective absorption bandwidth of 7.24 GHz and robust absorption of −44.48 dB, all within a mere thickness of 3.5 mm. Therefore, excellent market prospects for this material are anticipated. Highlights: A multilayer carbon magnetic heterostructure absorbing material was constructed on micrometer‐scale carbon fibers. The test results show that a wide effective absorbing bandwidth of 7.24 GHz and a minimum reflection loss of −44.48 dB are obtained when the composite thickness is 3.5 mm.The prepared multilayer absorbing composites can adapt to a variety of application scenarios and have excellent application prospects in the industry.The self‐polymerization of dopamine and complexation of metal ions were used to construct multilayer absorbing materials, and the dielectric loss and magnetic loss capacity of the carbon fibers improved. [ABSTRACT FROM AUTHOR]

Y-type hexaferrite ceramic materials of nominal composition Ba 2 Co 2 Cr x Y x Fe 12-2x O 22 (x = 0.00, 0.03, 0.06, 0.09, and 0.12) were synthesized by sol-gel auto combustion route. Y-type hexaferrites are technologically important ceramic materials for fabricating modern electronic devices and microwave absorbers due to their unique electrical and dielectric properties and reflection loss behavior. XRD classifies the single-phase formations with space group R 3 ‾ m. The crystallite size of the synthesized samples was calculated in (34–41) nm range. The specific absorption band in FTIR spectra approves the (Fe–O) stretching vibrations at wavenumbers 446 and 478 cm−1. The substitution of iron by Cr3+ and Y3+ increases DC resistivity from 1.03 × 1011 to 1.17 × 1012 Ω cm by limiting the electrons jumping between ferrous and ferric ions. The activation energy and drift mobility were also calculated among the substituting content of Cr3+-Y3+. The dielectric response in 1 MHz–6 GHz frequency was determined and the effect of substitution has been observed. The Maxwell-Wagner (MW) bilayer model is used to study dispersion in dielectric parameters with reference to applied frequency. The maximum values of dielectric losses were obtained at 6 GHz in the range of 0.37–0.60. The coercivity values confirms the soft magnetic nature of synthesized samples. The microwave absorption (MW) properties of synthesized materials were improved upon Cr3+-Y3+ substitution. Minimum reflection loss R Lmin = −66 dB (99.99% absorption of MW) at 1.46 GHz frequency and 1.96 mm thickness was obtained for x = 0.09 composition. All investigated samples are efficient materials for stealth technology, radar cross-reduction, EM interference shielding, and high-frequency applications. [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.)

From the two decades, the utilisation of electronic equipment in aerospace applications drastically increased. High-intensity radiated fields highly influence the operation of electronic equipment. As per the survey, an economy flight is affected by a lightning strike for every 1000 hours of its journey. For the fabrication of the airplane structure, fibre-reinforced materials (FRP) were used, but there is a flaw in FRP's. FRP's having low conductance, which cannot flow the currents produced by the lightning strike, which causes delamination and embrittlement of the airplane structure. A different composite material was introduced as a lightning strike protection (LSP) layer to overcome the said problem. The electromagnetic protection is obtained in terms of reflection and absorption of the EM waves. Al6061 material is reinforced with SiC and flyash at different combinations and obtained good mechanical, absorption loss, and reflection loss properties. The maximum reflection loss of 32.61 dB and absorption loss of 32.60 dB was obtained. [ABSTRACT FROM AUTHOR]

In this research, the BaFe12O19/Co3O4 material was carried out using the mechanical alloying approach with variations in Co3O4 composition of (10, 15, 20) wt%. The characterizations were using XRD, SEM-EDX, and VNA. The results of XRD analysis show that increasing crystal diameter increases Co3O4 compositions. SEM analysis results show that BaFe12O19 particles tend to form larger with the addition of Co3O4 particles, causing agglomeration. EDX shows that the percentage of Co3O4 increases, and the number of Fe atoms decreases while the number of Co atoms increases, indicating that Co ions replace Fe ions. The results of VNA analysis showed that the addition of 10 % Co3O4 composition had optimum absorption compared to other samples with a reflection loss of −22.7dB at a frequency of 10.88 GHz with an absorption percentage of 99.46 %.

Low-cost and high-efficiency electromagnetic wave absorption materials had extremely broad application prospects in the realms of military and civilian domains. A series of Ni-based PCS-derived adsorbents made from precursor infiltration pyrolysis at different pyrolysis temperatures were investigated in this research. The results showed that after being pyrolyzed at 1200 °C, the Ni-based PCS-derived adsorbent possessed the lowest reflection loss value of −59.52 dB, while it reached a peak effective absorption bandwidth of 2.84 GHz with 1000 °C treatment, of which the calculated electromagnetic absorption efficiency was meanwhile the best. Besides, the simulation results showed that the adsorbent after being pyrolyzed at 1000 °C could minimize the radar cross section of the target, of which the strongest radar cross section reduction value was 21.34 dB·m2, significantly enhancing its stealth performance. Therefore, the Ni-based PCS-derived adsorbent possessed great electromagnetic wave absorption performances under conditions of high-temperature pyrolysis, which provided a reference for future electromagnetic wave absorption material design. [ABSTRACT FROM AUTHOR]

Double-negative performance has played a significant role in electronic applications owing to its both permeability and permittivity negative values. Microwave absorption material has a substantial role in electromagnetic shielding, radar absorption, stealth applications, etc. Herein, a novel double-negative metacomposite, SrFe 12 O 19 /rGO, was designed by a simple one-pot hydrothermal method, and the microwave absorption properties of the material were studied in the microwave region from 2 to 18 GHz using VNA analysis. The structural and morphological studies were analysed using XRD, FT-IR, and SEM instrumentation techniques and the magnetic property of the material was studied using VSM analysis. Both studies confirmed the hard magnetic nature of the material. The particle sizes of SrFe 12 O 19 and SrFe 12 O 19 /rGO measured from XRD are 55.60 nm and 41.55 nm, respectively. Hexagonal plate-like morphology were observed from FESEM images. The coercivity of SrFe 12 O 19 /rGO increased, and the magnetocrystalline anisotropy was changed due to the decrease in particle size. The magnetic saturation value decreases due to the presence of non-magnetic rGO. The resultant SrFe 12 O 19 /rGO metacomposite shows negative permittivity and permeability values. The minimum reflection loss values observed for pure and rGO-decorated strontium ferrites are −28.49 dB at 7.76 GHz and −23.78 at 11.04 GHz, respectively. In addition to experimental results, simulation studies were also performed to study the reflection loss with matching thickness using a quarter wavelength mechanism. The results show that this composite can be employed as a left-handed metamaterial that finds applications in absorption, antennas, sensors, wireless power transfer systems, etc. The left-handed metamaterial can shift the frequency region from a lower to a higher frequency region. The rGO decorated metacomposite is a promising material for microwave absorption at higher frequency regions. [ABSTRACT FROM AUTHOR]

Highly effective electromagnetic (EM) wave absorber materials with strong reflection loss (RL) and a wide absorption bandwidth (EBW) in gigahertz (GHz) frequencies are crucial for advanced wireless applications and portable electronics. Traditional microwave absorbers lack magnetic loss and struggle with impedance matching, while ferrites are stable, exhibit excellent magnetic and dielectric losses, and offer better impedance matching. However, achieving the desired EBW in ferrites remains a challenge, necessitating further composition design. In this study, impedance matching is successfully enhanced and EBW in Ni–Zn ferrite is broadened by successive doping with Mn and Co , without incorporation of any polymer filler. It is found that Ni0.4Co0.1Zn0.5Fe1.9Mn0.1O4 material exhibits exceptional EM wave absorption, with a maximum RL of −48.7 dB. It also featured a significant EBW of 10.8 GHz, maintaining a 90% absorption rate (RL < −10 dB) for a thickness of 4.5 mm. These outstanding properties result from substantial magnetic losses and favorable impedance matching. These findings represent a significant step forward in the development of microwave absorber materials, addressing EM wave pollution concerns within GHz frequencies, including the frequency band used in popular 5G technology. [ABSTRACT FROM AUTHOR]

To create materials that interact effectively with electromagnetic (EM) radiation, new nanosized substituted ferrites (NiZn)1−xMnxFe2O4 (x = 0, 0.5, and 1) anchored on the surface of multi-walled carbon nanotubes (CNTs) have been synthesized. The concentration of CNTs in the (NiZn)1−xMnxFe2O4/CNT system was from 0.05 to 0.07 vol. fractions. The dielectric and magnetic characteristics of both pristine (NiZn)1−xMnxFe2O4 ferrites and (NiZn)1−xMnxFe2O4/CNT composite systems were studied. The introduction of (NiZn)1−xMnxFe2O4/CNT composites into the amorphous epoxy matrix allows to tailor absorbing properties at the high-frequency by effectively shifting the maximum peak values of the absorption and reflection coefficient to a region of lower frequencies (20–30 GHz). The microwave adsorption properties of (NiZn)1−xMnxFe2O4/0.07CNT–ER (x = 0.5) systems showed that the maximum absorption bandwidth with reflection loss below −10 dB is about 11 GHz. [ABSTRACT FROM AUTHOR]

The use of a single-layer material for microwave applications continues to attract many researchers due to materials' homogeneity in an acceptable range of thickness. This study outlines the microwave electromagnetic characteristics and interpretation of results based on a single-layer material backed by a perfect conductor. Data from three different laboratory prepared thermoplastic natural rubber (TPNR)/yttrium iron garnet (Y3Fe5O12)/magnetite (Fe3O4) composites were presented. The microwave relative complex dielectric permittivity (εr*) and magnetic permeability (µr*) were measured using a microwave vector network analyser (MVNA) in the frequency range of 0.1846–10.0104 GHz. The specular material model backed by a perfect conductor was used to obtain the frequency-dependent reflection loss (RL) assuming a normal incident of electromagnetic (EM) wave. The real and imaginary components of εr* (εr′ and εr″) and µr* (µr′ and µr″) for the three samples show a similar trend of frequency dependent. TPNR/Y3Fe5O12 reflected the EM wave less when its thickness (t) equals a quarter of the propagating wavelength (λm/4) inside the material. Interestingly, in the presence of Fe3O4, multiple minimal reflections occur at smaller thicknesses (e.g. t = λm/32). For both cases, this is the condition where the reflected wave at the surface of the material is in a 180°-phase difference from the wave reflected earlier at the material-conductor interface. Destructive interference occurs when these two waves meet and is visualized as the dip on the reflection loss (RL) vs. frequency plot. The number of dips increases with thickness. The lowest frequency dip occurs at a lower frequency for a thicker material. For TPNR/Y3Fe5O12/Fe3O4 and TPNR/Fe3O4, as the material gets thicker, the high-frequency dips on the RL plot become smaller and the use of the material in microwave application is no longer practical due to the increase in its weight and a smaller reflection loss. [ABSTRACT FROM AUTHOR]

3D printed honeycomb structures constituted by neat polylactic acid (PLA) and conductive PLA (PLAc) with different cell sizes and thicknesses were manufactured through 3D printing technology based on material extrusion (MEX). These structures were arranged into bi‐layer honeycomb structures (BHS) for evaluation of the microwave absorbing properties at the X‐band (8.2–12.4 GHz) and Ku‐band (12.4–18 GHz) frequency ranges. The effects of cell size, sample thickness, layer thickness ratio and the nature of the top layer on the electromagnetic attenuation performance of BHS samples were investigated in terms of reflection loss (RL). The components geometric characteristics and the arrangement of the layers exerted great influence on the RL values and effective absorption bandwidth (EAB). Overall the bilayer structures with 5 mm total thickness presented the best EM response in terms of EAB and minimum RL, where the component with the larger cell size (7.7 mm), PLAc (1 mm) as the top layer and PLA (4 mm) as the bottom layer exhibited the best results with RL values of −41 dB and EAB of 9.5 GHz. The BHS system with 7.7 mm cell size was more efficient in Ku band frequency range, whereas that with 3.5 mm cell size gave better response in the X‐band frequency range. Therefore, RL values and EAB can be adjustable by modifying the building strategy of the printed parts, such as thickness of the sample, cell size and thickness distribution of the conductive and non‐conductive layers. The findings in this work show the importance of the building strategy to fabricate components with controllable BHS and improved properties for microwave absorption application. [ABSTRACT FROM AUTHOR]

TiO2 is a highly potential, photoactive and dye-sensitive photocatalyst but its optical properties are further enhanced in the presence of different types of dyes. Dye-modified TiO2 was prepared by the modified sol–gel method. The dyes are methyl orange (MO), potassium permanganate (KMnO4) and beetroot. Analysis was conducted to study the physical, linear and nonlinear optical properties. XRD result suggests that the prepared TiO2 is synthesized in the pure anatase phase. The bandgap is decreased in all the dye-modified TiO2 samples. The dielectric constant, interband transition strength, energy loss functions, Urbach energy, optical conductivity and electrical conductivity were determined. Further, the dispersion parameter of refractive index was discussed as per the single-oscillator model proposed by Wemple and DiDomenico. Moreover, the analyses of nonlinear dispersions like first-order and third-order optical susceptibilities, electrical susceptibilities, nonlinear refractive index and reflection loss were performed. To further investigate the electronic properties, the plasma energy, Penn gap and Fermi energy were also determined. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing 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.)

Fabric-based microwave absorbing materials are favored due to their excellent flexibility and lightweight. However, the complex preparation method and unsatisfactory absorbing properties limit its mass production and practical application. Herein, a graphene@MXene@Fe 3 O 4 wave-absorbing slurry was prepared and coated on pre-treated aramid non-woven fabric by screen printing, to obtain flexible and efficient wave-absorbing modified fabric. Based on the high dielectric loss capacity of graphene and MXene, the magnetic loss can be successfully managed by modifying the Fe 3 O 4 content of the slurry to modulate the impedance matching, reflection loss (RL), and effective absorption bandwidth (EAB). The graphene@MXene@Fe 3 O 4 modified fabric demonstrated impressive microwave absorbing properties after multi-component integration and interface optimization. Notably, under an ultra-thin thickness of 1.5 mm, the reflection loss (RL min) value of the modified fabric reaches −47.6 dB under the X band. This work also establishes the way for the development of flexible and ultra-thin microwave absorbers utilizing a straightforward approach, which has a wide range of applications in the field of flexible absorbing materials. [ABSTRACT FROM AUTHOR]

Microwave power absorption by a two‐layer system deposited on a metallic surface is studied in the experimental setup emulating the response to a radar signal. Layers containing hexaferrite and iron powder in a dried paint of thickness under 1 mm are used. The data is analyzed within a theoretical model derived for a bilayer system from the transmission line theory. A good agreement between experimental and theoretical results is found. The advantage of using a bilayer system over a single‐layer system is demonstrated. How the maximum microwave absorption (minimum reflection) can be achieved through the optimization of the filling factors and thicknesses of the two layers is shown. [ABSTRACT FROM AUTHOR]

Composite material La0.7Sr0.3MnO3/α-Fe2O3 was prepared by high-temperature calcination method and its structure, electromagnetic parameters, and electromagnetic wave absorption performance were studied. Further preliminary exploration was conducted on the electromagnetic wave absorption effect of this powder for fabric coatings. The results showed that the significant absorption performance of La0.7Sr0.3MnO3/α-Fe2O3 is achieved when the powder and paraffin are mixed in a mass ratio of 7:3, and they can absorb over 99.9% of incident electromagnetic waves at a thickness of 5.0 mm and 9.5 mm, respectively. The absorption performance is excellent. In addition, within the range of 1-18 GHz and 1.0-10 mm, the total effective absorption (≤-10 dB) bandwidth of the sample La0.7Sr0.3MnO3/α-Fe2O3 covers 91.8% of the test bandwidth, achieving effective absorption of radar multi frequency bands. The excellent absorption performance of composite materials is attributed to the La0.7Sr0.3MnO3/α-Fe2O3. The combined effect of dielectric loss and magnetic loss of La0.7Sr0.3MnO3/α-Fe2O3 achieves effective absorption of electromagnetic waves. The fabrics prepared by coating method and plain weave methods can also absorb more than 90% of incident electromagnetic waves at 5.84 GHz, providing new ideas for the design and research of composite absorbing material and absorbing fabrics. [ABSTRACT FROM AUTHOR]

The development of novel nanomaterials with superior reflection loss (RL), thin thickness, wide bandwidth, and low density has recently received significant attention in an effort to increase their effectiveness in electromagnetic (EM) microwave absorption while maintaining an easy manufacturing process. Naturally, using conventional materials with magnetic or dielectric loss makes it difficult to achieve the last criterion and limitations the thickness of the absorber and mass production. In this work, microwave nanocomposites samples were prepared on epoxy resin with different percentages of the nanoparticles of aluminum oxide (epoxy/Al2O3) with surfaces treated by amino propyl and silane. The surface treatment was carried out to improve the adhesion, morphology, and EM properties of the samples to enhance the microwave absorption and the Shielding Effectiveness (SE). Therefore, the treated sample can be considered as potential candidate for high frequency EM absorption applications. Then, the study is followed by structural, morphological, thermal, and electrical characterization of the prepared samples in order to enhance the performances of the latters. The EM absorption and the shielding effectiveness were done in the X band frequency (8 GHz-12 GHz). The obtained results confirmed that the nanocomposites treated samples exhibit higher EM absorption performance and better electrical characteristics. Overall, these results put forward the role played by the addition of the nanoparticles films as high-performance materials in electronic devices and EM applications. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs)-derived microwave absorbers with tunable components and microstructures show great potential in microwave absorption. Herein, we report a facile thermal reduction approach for synthesizing CoNi alloy/reduced graphene oxide (CoNi/rGO) composites from bimetallic CoNi-MOFs. By tuning the ratio of graphene oxide (GO) in the precursors, the resulting CoNi/rGO-2 composite demonstrates optimal microwave absorption performance with a minimum reflection loss (RLmin) of −66.2 dB at 7.6 GHz in the C band. Moreover, the CoNi/rGO-2 with 50 wt% filler loading achieves a maximum effective absorption bandwidth (EAB) of 6.8 GHz (10.6–17.4 GHz) at a thickness of 2.5 mm, almost spanning the entire Ku band and a portion of the X band. The outstanding performance of CoNi/rGO-2 is ascribed to the high magnetic loss from the CoNi alloy and the incorporation of rGO, which induces interfacial polarization to enhance the dielectric loss and improve the impedance matching of composite. These favorable findings highlight the considerable potential and superiority of the CoNi/rGO-2 composite as an electromagnetic wave absorption material. This work sets forth a viable strategy for designing high-efficiency alloy/rGO absorbers. [ABSTRACT FROM AUTHOR]

Internationally, the relentless toll of breast cancer on women's lives persists, emphasizing the critical need for advancements in early detection methods. This paper delves into the promising domain of microwave imaging technology, where antennas play a pivotal role. It explores the performance of a single Antipodal Vivaldi Antenna (AVA) positioned at various angles around a breast phantom, with the paramount goal of revolutionizing breast cancer detection by meticulously comparing the antenna's Reflection loss, Gain, and H-field characteristics at 0°, 30°, and 60° angles. Considering the antenna's intended use in bioapplications, the paper also evaluates its Specific Absorption Rate (SAR) performance. Simulations are conducted using the designed antenna and a breast phantom model featuring four layers of tissue, and the results are scrutinized against established safety standards for bio applications [ABSTRACT FROM AUTHOR]

The microwave absorption performance of high-entropy alloys (HEAs) can be improved by reducing the reflection coefficient of electromagnetic waves and broadening the absorption frequency band. The present work prepared flaky irregular-shaped Al1.5Co4Fe2Cr and Al1.5Co4Fe2Cr@rGO alloy powders by mechanical alloying (MA) at different rotational speeds. It was found that the addition of trace amounts of reduced graphene oxide (rGO) had a favorable effect on the impedance matching, reflection loss (RL), and effective absorbing bandwidth (EAB) of the Al1.5Co4Fe2Cr@rGO HEA composite powders. The EAB of the alloy powders prepared at 300 rpm increased from 2.58 GHz to 4.62 GHz with the additive, and the RL increased by 2.56 dB. The results showed that the presence of rGO modified the complex dielectric constant of HEA powders, thereby enhancing their dielectric loss capability. Additionally, the presence of lamellar rGO intensified the interfacial reflections within the absorber, facilitating the dissipation of electromagnetic waves. The effect of the ball milling speed on the defect concentration of the alloy powders also affected its wave absorption performance. The samples prepared at 350 rpm had the best wave absorption performance, with an RL of −16.23 and −17.28 dB for a thickness of 1.6 mm and EAB of 5.77 GHz and 5.43 GHz, respectively. [ABSTRACT FROM AUTHOR]

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Implementation of stealth features on advanced airborne platforms (aircrafts, unmanned air vehicles, missiles, etc.) has become a compulsion for each country, for denial/delay detection of these objects from enemy radars, during tactical missions. Apart from the shaping of the airframe, implementation of microwave-absorbing materials (MAMs) on identified locations of airborne vehicles is the only viable solution to reduce their radar cross-section (RCS) and eventually attain stealth capabilities. Numerous dielectric and magnetic class materials have been developed over the last few decades to fulfil the requirement for RCS reduction against various radars operating in different frequency ranges. In this review, a detailed representation of almost the entire range of materials used as MAMs has been provided along with their possible microwave (MW) loss mechanism to fill the gap that existed for a systematic insight on MAMs till now. The current limitations and future aspects are also discussed for the development of future stealth materials. [ABSTRACT FROM AUTHOR]

Oxygen vacancy engineering is one of the most effective strategies for tuning the microstructural properties of oxide nanomaterials. However, the connection between oxygen vacancies and electromagnetic (EM) wave absorption capacities is unclear. Herein, oxygen vacancy-boosted microwave absorption is realized over Gd-doped Ni 0.5 Co 0.5 Fe 2 O 4 (NCFO) nanoceramics. All magnetic properties are studied with the influence of induced lattice strain. Except for Ni 0.5 Co 0.5 Gd 0.075 Fe 1.925 O 4 (NCFOG3), which has an elevated saturation magnetization (M s) of 63 emu/g, the M s decreases with increasing Gd content. In addition, remnant magnetization (M r), coercivity (H c), and anisotropic constant (K) increased until Ni 0.5 Co 0.5 Gd 0.050 Fe 1.95 O 4 (NCFOG2) and then declined. The EM wave parameters: dielectric permittivity (ϵ'), magnetic permeability (μ'), dielectric loss (ϵ''), and magnetic loss (μ'') are systematically examined and found in the ranges of 2.07–3.5, 1.73–4.7, (4 × 10-2) – (2.2 × 10-1) and 0.18–0.35 respectively. Our finding shows that a small amount of Gd favors the high oxygen vacancy concentration, an appropriate lattice defect, and high magnetic and dielectric losses. The possible mechanism for EM wave absorption revealed the largely localized electrons and dipole centers created by the numerous oxygen vacancies causing the multiple reflection and scattering, which enhanced conductive loss, defect, and dipole polarizations. The maximum reflection loss (RL) -28.37 dB is observed at 17.80 GHz of a 2 mm thick sample for NCFOG3. This research reveals a distinct link between oxygen vacancy defects and EM wave dissipation capability, providing important information for developing better EM wave absorbents. [Display omitted] [ABSTRACT FROM AUTHOR]

The perovskite manganese oxide, La 0.7 Sr 0.3 Mn 1+ x O 3 (x = −0.4, −0.2, 0, 0.2, 0.4, 0.6, 0.8, 1.0), was synthesized using the solid-state reaction method. A single-phase perovskite structure was obtained at the stoichiometric composition (x = 0). However, with an increase in Mn excess (x > 0), secondary phases of Mn 2 O 3 and Mn 3 O 4 formed and increased, while La 2 O 3 and Sr-rich phases emerged when Mn is deficient (x < 0). The electrical conductivity, permittivity, and permeability of the samples showed significant variations with x , as both charge transport and magnetism originate from the presence of Mn. Complex permittivity (ε', ε") and permeability (μ', μ") spectra were utilized to calculate RL maps based on a transmission line theory. For samples with x ≥ 0, which exhibited relatively high values of ε' and ε", there was no significant absorption of electromagnetic (EM) waves within the measured frequency range (0.1 ≤ f ≤ 18 GHz) due to high EM wave reflection. Conversely, the Mn-deficient samples (x = −0.2, −0.4) demonstrated excellent EM wave absorption properties in the GHz range. This can be attributed to their favorable impedance matching characteristics, resulting from significantly reduced ε' and ε" values in the Mn-deficient samples. Notably, the sample with x = −0.2 exhibited the most outstanding EM wave absorption characteristics, with an RL value of −56 dB at a frequency of 2.33 GHz and a thickness of 7.59 mm. Additionally, it achieved an RL value of −50 dB at 9.8 GHz and 2.90 mm thickness. [ABSTRACT FROM AUTHOR]

Electromagnetic devices have hazardous effects to the environment in the form of pollution. Materials having higher reflection loss and good absorption properties can overcome this pollution. This study synthesizes the Ba 2 Zn 2-x Mg x Fe 28 O 46 (x = 0.0, 0.1, 0.2, 0.3, and 0.4) using sol-gel method. The higher value of reflection loss of prepared samples was successfully achieved which can be used for absorption applications. X-ray diffraction patterns show a x-type hexagonal phase with crystallite's size ranged from 18 to 43 nm. All the vibrational bands shifted by changing the substitution in all compositions. Six distinct peaks in Raman spectra are located at positions 62, 174, 332, 408, 525, and 673 because of the molecules' phonon vibrations. The peaks were found in the XPS spectrum mode range of 1350-1 eV. All substitutions had a high dielectric constant, dielectric loss, and tan loss at low frequencies, but this value decreased as the frequency increased. The Cole-Cole plots and complex impedance spectroscopy revealed that grain boundary contributed for most dielectric responses. For these materials, cole-cole plots showed a complete semicircle, demonstrating the grain boundary resistance within the samples. Mg substituted Zn-X ferrite with RL of −69.3, and −62.0 dB are found to have excellent microwave absorption properties. The prepared samples could be used for absorption and super-capacitor applications. [ABSTRACT FROM AUTHOR]

In conjunction with the enhancement of societal living standards and the rapid development of information technology, an extensive variety of high-capacity electronic devices are being introduced to the market. The heightened demands result in the generation of electromagnetic wave radiation, which poses a potential risk to human well-being. Barium hexaferrite (BHF) is one of the radar-absorbing materials (RAMs) that can absorb electromagnetic waves because it has a high anisotropic field. However, its drawbacks are narrow absorption and less stability. Molybdenum disulfide (MoS2), is the best candidate for the reinforcement of BHF. The study investigated the impact of increasing the thiourea, temperature, hydrothermal holding time, and sample thickness on reflection loss. This study used a two-step molten salt and hydrothermal synthesis to make a BaFe12O19@MoS2 core-cell composite. Two-step molten salt and hydrothermal synthesis methods created single-phase BaFe12O19@MoS2 core-cell composites that worked well. The results showed that adding MoS2 to BHF changed BHF’s magnetic properties from hard to soft. Increasing the hydrothermal temperature up to 220°C effectively reduced the reflection loss of BaFe12O19@MoS2. On a 2 mm thick sample containing 100 mmol thiourea, the study achieved an electromagnetic wave absorption of 99.97 % with a reflection loss of –35.41 dB (17.37 GHz). The results of this research can be applied to protect electronic devices vulnerable to signal interference from satellite radar systems at frequencies of 12–18 GHz [ABSTRACT FROM AUTHOR]

As contemporary aerospace and radar-detecting technologies evolve, hypersonic vehicle components must avoid electromagnetic wave (EMW) detection in extremely harsh environments. In this study, lightweight porous SiC/Si 3 N 4 composite nanowires (SiC/Si 3 N 4 NWs), exhibiting excellent performance of broadband electromagnetic wave absorption (EWA), were successfully prepared via a facile electrostatic spinning and heat treatment in nitrogen atmosphere using phenol-formaldehyde resin (PR) and silica solution as precursors. The nanowire (NW) was composed of carbon-rich SiC and Si 3 N 4 nanograins, and its microstructure and phase composition were regulated by carbon thermal reduction temperature. The EWA performance of the nanowires obtained through carbothermal reduction at 1300 °C, 1400 °C，and 1500 °C was investigated. The nanowires with 15 wt% obtained at 1500 °C were added to a paraffin matrix and the effective absorption bandwidth (EAB) was observed to cover almost the entire C, X, and Ku bands (4.2–18 GHz). Moreover, for a coating thickness of only 2.1 mm, the EAB was as high as 7.12 GHz (10.88–18 GHz), covering the entire Ku-band and achieving a minimum value of reflection loss (RL min) of - 48 dB at 6.5 GHz. The 3D network structure of SiC/Si 3 N 4 NWs with large specific surface areas and numerous mesopores extended the electromagnetic wave (EMW attenuation route and effectively improved the EWA performance through interfacial synergy between the carbon-rich SiC and Si 3 N 4 nanograins). The strong absorption and wide EAB of the porous SiC/Si 3 N 4 NWs rendered them highly suitable lightweight EMW absorbers in harsh, high-temperature environments. [ABSTRACT FROM AUTHOR]

The application of magnetic nanocrystalline powders as radar absorption materials is increasingly attracting R&D interest. Severe agglomeration and mass production, however, are critical issues for practical application of magnetic nanoparticles. In the present study, iron nanowires with varying amounts of nickel addition (0, 1, 10, 30, and 50 wt%) were synthesized via direct reduction of iron salts with the aid of strong NdFeB magnets. The yield rate of these Ni-added iron nanowires (NiFe NWs) exceeded 1 g/min, making them suitable and was feasible for mass production. The characteristics of the so-obtained NiFe NWs were confirmed using field emission scanning electron microscopy, X-ray diffraction, and high-resolution transmission electron microscopy. Composite resins with NiFe NWs additions (3, 5, and 10 wt%) were prepared and examined using the coaxial line method to reveal their microwave absorption characteristics. Experimental results showed that composite resins with 10 wt% NiFe NWs additions possessed superior microwave absorbing properties, with the Ni1Fe99 NWs-added product exhibiting the best performance. When produced with a thickness of 1.7 mm, the reflection loss of the composites reached −39.28 dB at 12.53 GHz. Additionally, the efficient maximum absorption bandwidth was 3.33 GHz, ranging from 14.27 to 17.60 GHz.

The electromagnetic wave absorption capabilities of an absorber depend on its dielectric and magnetic components, which determine its interfacial polarization, conductivity loss, magnetic loss, and other such mechanisms. In this study, a comprehensive review of the electromagnetic wave and material interaction was conducted. Moreover, for a better understanding of the trends and evolutionary developments in the study of the electromagnetic wave absorber, 23300 documents dated between 1990 and 2020 were examined, which were obtained from Scopus using the keywords of “electromagnetic wave absorption” and “microwave absorption”. The data search in Scopus was conducted using the related keywords in the search bar for titles and abstracts. These results demonstrate that the majority of research regarding electromagnetic wave absorbers was conducted in China, which was followed by the United States. The number of published documents regarding the electromagnetic wave absorption field significantly increased between 1990 and 2020; these documents were mostly published as journal articles. With respect to the journal activity, the most productive journal was the “Journal of Alloys and Compounds”, with a total of 592 articles. In addition, graphene and titanium dioxide were determined to be the materials that were most studied in the field of electromagnetic wave absorption.

In the present work, regularities of changes in the frequency dependence of microwave shielding properties of fabricated 2D and 3D metastructures with periodic lattices based on glass microspheres coated with GNPs, GNPs-NiFe, MoS2 and a mixture of MoS2 + 20 % GNP were established. The influence of the size of carbon-based globular structures, the type of globule coating and the type of polymer matrix on the value and balance between the indices of electromagnetic radiation reflection, absorption and transmission in the frequency range of 25-37 GHz is considered. Glass balls with a diameter of 600 µm and 1.8 mm were used as a glass core. It was established that the increase in the size of glass microspheres leads to an increase in the shielding efficiency, and a large amount of GNP or GNPs-NiFe in the 3D structure contributes to the effective attenuation of electromagnetic radiation by increasing the reflection and absorption of microwaves. The presence of NiFe magnetic component on the glass microspheres leads to an increase in the absorption coefficient A, while the reflection coefficient R decreases compared to composites based on glass microspheres covered only with GNPs. [ABSTRACT FROM AUTHOR]

Microwave absorbers that are lightweight and have good stability and high efficiency have attracted much attention for their applications in many contemporary fields. In this work, a 3D porous (Ni@NO-C)n/NO-C composite absorber was prepared using a wet chemistry method with Ni chains and melamine as precursors, in which NO-C (N,O-doped carbon)-encapsulated Ni particles are homogenously dispersed in the 3D porous networks of NO-C in the form of (Ni@NO-C)n chains. The special microstructure of the as-prepared material is proven to be beneficial for the improvement of its microwave absorption performance. The as-synthesized (Ni@NO-C)n/NO-C composite absorber exhibited an effective absorption bandwidth of 4.1 GHz and an extremely large reflection loss of −72.3 dB. The excellent microwave-absorbing performances can be ascribed to the cooperative consequences of dielectric loss and magnetic loss, along with the balance between attenuation capability and impedance matching. [ABSTRACT FROM AUTHOR]

Polycrystalline Cr3+ substituted Ba 4 Zn 2 Fe 36-x Cr x O 60 (Zn 2 U) U-type hexaferrite compositions Ba 4 Zn 2 Fe 36-x Cr x O 60 (x = 0.0, 0.5, 1.0, 1.5, and 2.0) were fabricated using the sol-gel self-ignition technique. U-type hexaferrite structure was achieved by sintering the powdered samples for 6 h at 1200 °C in a muffle furnace. The phase identification and structural parameters of Zn 2 U hexaferrites were evaluated by X-ray diffraction peaks of the powdered samples. Lattice parameters (a,c) and unit cell volume decreased upon Cr3+ substitution. The crystallite size was measured between 61 and 57 nm. FTIR spectra revealed the existence of specific absorption (Fe–O) bands at wavenumbers 419 and 539 cm−1. These bands further verify the formation of U-type hexaferrite. SEM micrographs showed the platelet-like morphology of the grains with proper hexagonal structure. X-ray photoelectron spectroscopy (XPS) results confirmed the existence of all metal ions with their corresponding electronic states. The dielectric response of the fabricated Zn 2 U U-type hexaferrite pellets was investigated at room temperature through a vector network analyzer with a wide frequency band from 1 MHz to 6 GHz. Dielectric constant (εʹ) was increased for the compositions x = 1.0 and 1.5 while dielectric loss (εʺ), tangent loss (tanδ), and ac conductivity (Ϭ ac) were reduced upon Cr3+ substitution. Single semicircles in the impedance Cole-Cole plots revealed that grain boundaries play a vital role in the conduction process of prepared U-type hexaferrites. Microwave absorption (MW) was improved with Cr3+ substitution. The minimum reflection loss (R L) of −53dB (99.99% MW absorption) at frequency 1.3 GHz was obtained for composition x = 0.5. The dielectric analysis (low losses and high Q-values) of the prepared hexaferrites predicts their appropriate use in high-frequency device applications. [ABSTRACT FROM AUTHOR]

Electromagnetic radiation interference (EMI) or pollution is increased significantly in proportion to the expansion of electronic and communication industries, which lead to the disturbance of the functioning of electronic gadgets and medical equipments, in addition to the human health damage. The Microwave absorbing (MA) composite comprised of polyvinyl alcohol (PVA), polyaniline (PANI), carbon nanotube (MWCNT) and iron oxide (Fe3O4) has been developed with various proportions, denoted as PVA/PANI/MWCNT/Fe3O4 (1%, 3%, 5%). Fe3O4 was prepared using a hydrothermal method, and PVA/PANI/MWCNT/Fe3O4 (1%, 3%, 5%) nanocomposites was made by solvent casting techniques. The PVA composite films were also subjected to a range of analyses including IR, TGA, DTA, DTG, SEM, TEM, dielectric measurements and EMI shielding effectiveness (EMI SE), to describe their characteristics. The results of various studies indicate that the PVA/PANI/MWCNT/Fe3O4 (1%, 3%, 5%) composites possess enhanced thermal and dielectric characteristics, for instance the PVA/PANI/MWCNT/5% Fe3O4 blend nanocomposites possess 10% initial decomposition at 220°C and dielectric constant of 3.2 × 107 at 1 MHz. The total EMI SE value for the synthetic PVA/PANI/MWCNT/Fe3O4 was found at 9.2 and 10 GHz is 48 and 54 dB, respectively, exhibiting synergistic properties of the composites toward EMI shielding. The microwave absorption spectra indicate two absorption peaks in the region around 8 to 12 GHz, with the absorption reflection loss (RL) value of −20 dB at 10 GHz for the PVA/PANI/MWCNT/5% Fe3O4 nanocomposites. [ABSTRACT FROM AUTHOR]

The combination of two dielectric-magnetic components in the same composite has been shown to significantly improve the effectiveness of electromagnetic (EM) shielding and microwave absorption (MWA) because they have both a combination of high dielectric and magnetic losses and good impedance matching. The novel Bi1/2(Na0.8K0.2)1/2TiO3/Fe3O4 (BNKT/Fe3O4) composite has been successfully synthesized by a two-step method with wide effective absorption bandwidth (EAB = 16 GHz) in the high-frequency (2-18 GHz). It was evident that the MWA efficiency of the BNKT/Fe3O4 composite has been significantly improved compared with pure Bi1/2(Na0.8K0.2)1/2TiO3 or Fe3O4 materials. In addition, the BNKT/Fe3O4 composite could achieve reflection loss (RL = -39.41 dB, ~99.99% at 10.16 GHz) with a sample thickness optimal (d = 4.7 mm). This work shows that the novel BNKT/Fe3O4 composite has excellent MWA properties, all contributing to a potential candidate in the electromagnetic wave absorption and shielding fields. [ABSTRACT FROM AUTHOR]

Aiming at the evaluation of the shielding effectiveness (SE) of materials against high-intensity electromagnetic pulse (EMP), the shielding mechanism in the frequency domain is investigated, and the factors that determine SE such as conductivity, thickness of material, and test frequency are analyzed. The attenuated waves of solid and perforated plate materials irradiated by EMP are simulated in CST. The results show that the two materials exhibit low-pass and high-pass filtering characteristics, respectively, which lead to a big difference in the transmitted waves (rise time and pulse width). Based on this, a time domain SE test method using coaxial flange is proposed which can obtain the incident and the transmitted and reflected waves, and the time domain SE of graphenes with different thicknesses (80, 100, 200, and 300 μm) are measured. The characteristics of the reflected and transmitted waves are analyzed in detail, and the change regulations comply with the theoretical shielding model well. The peak value SE and energy density SE, respectively, are calculated. Furthermore, the frequency domain SE can be obtained through the Fourier transform, so the method has a wide application in material SE performance evaluation against high-intensity EMP. [ABSTRACT FROM AUTHOR]

La-Sr co-doped Ba1−x(La0.5Sr0.5)xCo2Fe16O27 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0, respectively) hexaferrites were prepared by the solid-state method. W-type hexaferrite single phase structure with space group P63/mmc was obtained when the doping amount was x < 0.4 and an M-type hexaferrite and a spinel phase with smaller grains gradually replaced the W phase as the primary phases when x ≥ 0.6. The maximum Ms is 76.2 emu/g and the minimum Hc is 60 Oe at x = 0.4, as obtained by VSM analysis. The magnetoelectric properties of the samples were tested at 1–18 GHz with a vector network analyzer and the reflection loss was calculated based on transmission line theory. It was found that the introduction of an appropriate amount of La-Sr provides a large number of porosity defects while increasing the grain size, which can effectively improve the reflection of electromagnetic waves inside the material and dissipate more energy. At the same time, co-doping also makes the resonance frequency of the samples shift to lower frequency, resulting in tunable absorption properties in the C, X and Ku bands. When x = 0.2, the minimum reflection loss is −40.61 dB at 1.5 mm thickness, with the effective absorption bandwidth of 5.76 GHz in the X band; when x = 0.4, the minimum reflection loss is −37.45 dB at 2.5 mm, with the bandwidth of 4.97 GHz in the C band; when x = 0.6, the material has good absorption in both the X and Ku bands with the thickness less than 2 mm. The simple preparation method and good performance make La-Sr co-doped Co2W ferrite a promising microwave absorbing material. [ABSTRACT FROM AUTHOR]

A series of erbium-substituted Z-type hexaferrites with composition Ba 3 Co 2 Er x Fe 24-x O 41 (0.00≤ x ≤ 0.12, Δx = 0.03) was synthesized via the sol-gel auto combustion technique and sintered at 1200 °C for 5:30 h. XRD analysis confirmed the single phase crystals throughout the samples. Incorporating erbium ions into a Z-type hexagonal lattice showed improved structural parameters. The lattice parameters (a, c) exhibited an increasing trend with the rare earth (Erbium) substitution in the range of 5.884–5.891 nm and 52.561–52.770 nm. Scherrer's equation was used to find crystallite size in 28–30 nm range. Absorption bands of ferrite phase were confirmed by Fourier Transform Infrared Spectroscopy. Dielectric characteristics of synthesized materials were studied through Epsilometer R60 VNA over a frequency 1 MHz to 6 GHz range. Variations in dielectric parameters were observed by substituting erbium ion into a Z-type hexaferrite lattice. The magnitude of the dielectric constant, AC conductivity, tangent loss, and dielectric loss increases at higher frequencies. While, dielectric constant, AC conductivity, loss factor, and tangent loss decrease with Erbium substitution. The high value of Q-factor ∼10232 at 0.87 GHz was observed. The cole-cole plots in impedance analysis confirmed the character of grains and grain boundaries in the conduction mechanism. Minimum reflection loss (RL) was −67 dB for the sample x = 0.06 at 0.2 GHz. At 1.28 GHz frequency, RL = −46 dB was observed for sample x = 0.03. The morphological study (SEM) revealed the hexagonal platelet-type grains with an average grain size of 2.48–2.73 μm. Minimum reflection loss, small crystallite size <50 nm, and high-quality factor suggested that these materials are suitable candidates for microwave absorbers, resonant circuits, multi-layer chip inductors, and high-frequency devices. [ABSTRACT FROM AUTHOR]