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As the integration technology for integrated circuit (IC) packaging continues to advance, the issue of electromagnetic interference in IC packaging becomes increasingly prominent. Magnetic materials, acknowledged for their superior electromagnetic absorption capabilities, play a pivotal role in mitigating electromagnetic interference problems. In this study, we employed a liquid-phase reduction method. We prepared three types of cobalt (Co) particles with distinct morphologies. Through variations in the synthesis process conditions, we were able to control the aspect ratio of protrusions on the surface of the Co particles. It was found that the sword-like Co particles exhibit superior electromagnetic wave absorption capabilities, showing a reflection loss value of up to −50.96 dB. Notably, when the coating thickness is only 1.6 mm, the effective absorption bandwidth is extended up to 7.6 GHz. The spatially expansive sword-like Co particles, with their unique structure featuring dipole polarization and interfacial polarization, demonstrated enhanced dielectric and magnetic loss capabilities, concurrently showcasing superior impedance-matching performance. [ABSTRACT FROM AUTHOR]

Highlights: The hierarchical porous structure is regulated by various species of PVP to achieve impedance matching. Interfacial engineering boosts conductivity and constructs a multiband (C, X, Ku) tunable electromagnetic wave absorber. Hierarchical porous molybdenum selenide/epoxy coating exhibits marine anticorrosion capability. Electromagnetic wave (EMW) absorbing materials have an irreplaceable position in the field of military stealth as well as in the field of electromagnetic pollution control. And in order to cope with the complex electromagnetic environment, the design of multifunctional and multiband high efficiency EMW absorbers remains a tremendous challenge. In this work, we designed a three-dimensional porous structure via the salt melt synthesis strategy to optimize the impedance matching of the absorber. Also, through interfacial engineering, a molybdenum carbide transition layer was introduced between the molybdenum selenide nanoparticles and the three-dimensional porous carbon matrix to improve the absorption behavior of the absorber. The analysis indicates that the number and components of the heterogeneous interfaces have a significant impact on the EMW absorption performance of the absorber due to mechanisms such as interfacial polarization and conduction loss introduced by interfacial engineering. Wherein, the prepared MoSe2/MoC/PNC composites showed excellent EMW absorption performance in C, X, and Ku bands, especially exhibiting a reflection loss of − 59.09 dB and an effective absorption bandwidth of 6.96 GHz at 1.9 mm. The coordination between structure and components endows the absorber with strong absorption, broad bandwidth, thin thickness, and multi-frequency absorption characteristics. Remarkably, it can effectively reinforce the marine anticorrosion property of the epoxy resin coating on Q235 steel substrate. This study contributes to a deeper understanding of the relationship between interfacial engineering and the performance of EMW absorbers, and provides a reference for the design of multifunctional, multiband EMW absorption materials. [ABSTRACT FROM AUTHOR]

Highlights: 3D cubic hollow core–shell NiCo2O4@C composites were synthesized. Oxygen vacancies were introduced into the prepared composites. Ultrabroad effective absorption bandwidth of 12.48 GHz was obtained. The absorption performance mechanism of NiCo2O4/C composites was investigated. Cobalt nickel bimetallic oxides (NiCo2O4) have received numerous attentions in terms of their controllable morphology, high temperature, corrosion resistance and strong electromagnetic wave (EMW) absorption capability. However, broadening the absorption bandwidth is still a huge challenge for NiCo2O4-based absorbers. Herein, the unique NiCo2O4@C core–shell microcubes with hollow structures were fabricated via a facile sacrificial template strategy. The concentration of oxygen vacancies and morphologies of the three-dimensional (3D) cubic hollow core–shell NiCo2O4@C framework were effectively optimized by adjusting the calcination temperature. The specially designed 3D framework structure facilitated the multiple reflections of incident electromagnetic waves and provided rich interfaces between multiple components, generating significant interfacial polarization losses. Dipole polarizations induced by oxygen vacancies could further enhance the attenuation ability for the incident EM waves. The optimized NiCo2O4@C hollow microcubes exhibit superior EMW absorption capability with minimum RL (RLmin) of −84.45 dB at 8.4 GHz for the thickness of 3.0 mm. Moreover, ultrabroad effective absorption bandwidth (EAB) as large as 12.48 GHz (5.52–18 GHz) is obtained. This work is believed to illuminate the path to synthesis of high-performance cobalt nickel bimetallic oxides for EMW absorbers with excellent EMW absorption capability, especially in broadening effective absorption bandwidth. [ABSTRACT FROM AUTHOR]

Highlights: 3D cubic hollow core–shell NiCo2O4@C composites were synthesized. Oxygen vacancies were introduced into the prepared composites. Ultrabroad effective absorption bandwidth of 12.48 GHz was obtained. The absorption performance mechanism of NiCo2O4/C composites was investigated. Cobalt nickel bimetallic oxides (NiCo2O4) have received numerous attentions in terms of their controllable morphology, high temperature, corrosion resistance and strong electromagnetic wave (EMW) absorption capability. However, broadening the absorption bandwidth is still a huge challenge for NiCo2O4-based absorbers. Herein, the unique NiCo2O4@C core–shell microcubes with hollow structures were fabricated via a facile sacrificial template strategy. The concentration of oxygen vacancies and morphologies of the three-dimensional (3D) cubic hollow core–shell NiCo2O4@C framework were effectively optimized by adjusting the calcination temperature. The specially designed 3D framework structure facilitated the multiple reflections of incident electromagnetic waves and provided rich interfaces between multiple components, generating significant interfacial polarization losses. Dipole polarizations induced by oxygen vacancies could further enhance the attenuation ability for the incident EM waves. The optimized NiCo2O4@C hollow microcubes exhibit superior EMW absorption capability with minimum RL (RLmin) of −84.45 dB at 8.4 GHz for the thickness of 3.0 mm. Moreover, ultrabroad effective absorption bandwidth (EAB) as large as 12.48 GHz (5.52–18 GHz) is obtained. This work is believed to illuminate the path to synthesis of high-performance cobalt nickel bimetallic oxides for EMW absorbers with excellent EMW absorption capability, especially in broadening effective absorption bandwidth. [ABSTRACT FROM AUTHOR]

Atomic‐level structural editing is a promising way for facile synthesis and accurately constructing dielectric/magnetic synergistic attenuated hetero‐units in electromagnetic wave absorbers (EWAs), but it is hard to realize. Herein, utilizing the rapid explosive volume expansion of the CoFe‐bimetallic energetic metallic triazole framework (CoFe@E‐MTF) during the heat treatment, the effective absorption bandwidth and the maximum absorption intensity of a series of atomic CoFe‐inserted hierarchical porous carbon (CoFe@HPC) EWAs can be modified under the diverse synthetic temperature. Under the filler loading of 15 wt%, the fully covered X and Ku bands at 3 and 2.5 mm for CoFe@HPC800 and the superb minimum reflection loss (RLmin) of −53.15 dB and specific reflection loss (SRL) of −101.24 dB mg−1 mm−1 for CoFe@HPC1000 are achieved. More importantly, the single‐atomic chemical bonding among Co─Fe on the nanopores is captured by extended X‐ray absorption fine structure, which reveals the formation mechanism of nanopore‐confined vortical dipoles and magnetic domains. This work heralds the infinite possibilities of atomic editing EWA in the future. [ABSTRACT FROM AUTHOR]

Ferrites were among the earliest types of microwave absorbers due to their high magnetic dissipation and low cost. Ferrites, on the other hand, have some disadvantages, such as a low natural resonance frequency (fr), a lack of dielectric loss, and a high density. We effectively generated (SrMnCoFe 10 O 19 /MnCoFe 2 O 4)/SiO 2 samples with hollow microfiber morphologies and most of the effective parameters suggested to overcome these disadvantages and increase the microwave dissipation properties of ferrites. Hard and soft SrMnCoFe 10 O 19 /MnCoFe 2 O 4 hollow microfibers were obtained using sol-gel and electrospinning technology. After heat treatment at 1050 °C for 3 h, the binary ferrites are formed. (Hard ferrite/soft ferrite)/SiO 2 core-shell structures were fabricated by the Stober process, so their microwave absorption performance is greatly influenced by the hard/soft mass ratio and SiO 2 thickness of the sample. The fabricated fibers were characterized by x-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FESEM), FTIR spectroscopy, and vector network analyzer (VNA). The single-phase structure of all microfibers was determined by X-ray diffraction (XRD) analysis. The phase formation of the coated microfibers is also elaborated using Fourier transform infrared spectroscopy (FTIR) based on identified chemical bonds. According to the (FESEM) analysis results, the microfibers manufactured have a homogeneous core–shell structure. A vector network analyzer was used to investigate the samples' dielectric constants and microwave absorption properties between 12 and 18 GHz at room temperature. The results showed that when the mass ratio is hard/soft (8: 2) and the mass ratio of ferrite/SiO 2 (1:1), the maximum reflectance loss is −27 dB and the absorption bandwidth is 2 GHz. The magnetic saturation (Ms) was calculated at 43.44 emu/g and the calculated coercivity values (1163.07 Oe) confirm the hard ferrite/soft ferrite/SiO 2 core-shell structures. [Display omitted] [ABSTRACT FROM AUTHOR]

In this research, we developed a wideband electromagnetic wave absorber suitable for the X-band frequency by using a unique hybrid nanocomposite structure made of FeWO 4 embellished with Ag 3 PO 4 nanopowders. Simple chemical hydrothermal and microwave-aided hydrothermal procedures were used to successfully produce single-phase spherical-like FeWO4 and FeWO4@Ag3PO4 nanocomposite powders. Using XRD, FTIR, VSM, FESEM, and VNA methods, the phase constituents, morphological, magnetic, and electromagnetic properties of the produced nanocomposite materials were assessed. The resin-based nanocomposite absorber sample allows to obtain a maximum reflection loss of −21 dB with a matching thickness of 1.8 mm at the ferromagnetic resonance of 10.4 GHz with a 3.8 GHz effective absorption bandwidth, which is evaluated using the waveguide technique, when the filler loading percentage reaches 40 wt percent (S40). S40 had superior impedance matching capabilities, a wide effective absorption bandwidth, and a high absorption capacity when compared to other produced absorber samples. The best sample is prepared for free-space testing with the dimension of 200 × 200 mm and an optimum thickness of 1.8 mm, and the results demonstrate a good agreement between the waveguide and free-space technique results. This absorber sample's wideband absorption capacity was attained by adjusting the magneto-electric composition and enhancing the interfacial characteristics brought on by the core-shell construction. In this study, a design approach for efficient microwave absorbers based on a magneto-electric hybrid nanocomposite structure is presented, using waveguide and free-space experimental methods in two different ways. [ABSTRACT FROM AUTHOR]

In this study, the electromagnetic wave absorption properties of woven glass fiber reinforced epoxy composites with Sb2O3 and SnO2 nanoparticles doped mica pigments were investigated. Herein, we synthesized SnO2/mica, Sb2O3/mica, and Sb2O3:SnO2/mica pigments using the sol–gel method. Subsequently, mica pigments filled glass fiber/epoxy composite panels were fabricated with a vacuum assisted resin mold. The phase, crystal, and morphological examinations of particles confirm the deposition of SnO2 and Sb2O3 nanoparticles on the mica surfaces. The electromagnetic wave absorption properties of samples were measured using the S parameters and obtained dielectric data. Sb2O3:SnO2/mica particles display higher complex permittivity and dielectric loss values due to the strong interfacial polarization between conductive nano metal‐oxide shells and mica surfaces. According to the calculated reflection loss values, Sb2O3:SnO2/mica particles exhibit superior electromagnetic wave absorption performance with a minimum reflection loss of −25.62 dB for 2.4 mm thicknesses with effective bandwidth between 9.3 and 12.4 GHz. The S parameters of the prepared structural composites with the size of 30 cm × 30 cm × 3 mm was determined by the free‐space technique using the transmission line technique. According to the S12 parameters, filled glass fiber/epoxy composite containing 25 wt% Sb2O3:SnO2/mica show a minimum reflection loss of −20.426 dB at 8.2 GHz with effective bandwidth between 8.2 and 9.67 GHz. These results indicate that Sb2O3:SnO2/mica‐filled fiber/epoxy composite is an excellent candidate for the practical application of electromagnetic wave absorbers. [ABSTRACT FROM AUTHOR]

In contemporary civilization, the electromagnetic radiation from electronic devices and communication systems has become a substantial pollutant. High-performance electromagnetic absorbers have become a solution for absorbing unwanted electromagnetic waves. This research proposed a lightweight and flexible electromagnetic absorber produced from natural rubber filled with conductive carbon black (CCB) and Fe3O4. The effect of CCB, Fe3O4, and a combination of CCB and Fe3O4 as a hybrid filler on foam morpholog, electromagnetic reflectivity, tensile strength, and compression set properties were investigated. In addition, the effect of the alternating layered structure of CCB and Fe3O4 on electromagnetic absorption was investigated. The results indicated that the composite foam exhibited an interconnected network structure that enhanced the electromagnetic attenuation in the absorber. CCB increased the electromagnetic absorption of the foam, whereas Fe3O4 had less of an effect. The foam filled with the hybrid filler at the CCB/Fe3O4 ratio of 8/2 exhibited excellent electromagnetic absorption. The composite foam had a higher tensile modulus and higher strength compared to neat foam. The addition of CCB decreased the compression set; however, the compression set was improved by the incorporation of Fe3O4. Composite foams filled with hybrid filler can serve as highly efficient electromagnetic absorbing materials. [ABSTRACT FROM AUTHOR]

Multiple relaxation behaviors are promising for broad frequency band and strong electromagnetic wave (EMW) absorption based on polarization‐controlled electromagnetic (EM) attenuation. However, rational selection of materials and structure manipulation through tunable substitution or phase control are challenging toward optimization of EMW absorption. Herein, bi‐metallic organic frameworks (B‐MOFs) with various morphologies are employed as EMW absorbers. Remarkably, the polar units can be enhanced by introducing Ni‐metal nodes into the Cu‐coordinated MOFs, rendering the B‐MOFs with self‐polarized properties and consecutive multifrequency EMW absorption behaviors. The maximum reflection loss of acetylene black (ACET) filled NiCu‐MOFs can reach –40.54 dB together with a wide bandwidth (<‐10 dB) of 5.87 GHz at a thickness of 2.5 mm. As a counterpart of the Ni/Cu/C derivatives, significantly increased broad band absorption (6.93 GHz) and multifrequency absorbing and polarization characteristics are also maintained in bimetal coexisting carbonized architectures as prepared by calcination of CuNi‐MOFs. This work demonstrates that the performance of effective absorbing frequency band can be enhanced in multi‐metallic organic frameworks‐based architectures, and paves a novel avenue for developing broadband and strong EMW absorbers. [ABSTRACT FROM AUTHOR]

In order to overcome the problems caused by electromagnetic pollution, the design and development of high-performance microwave absorbers is urgently required. In this work, a hierarchical ZnFe 2 O 4 @MnO 2 @RGO composite was successfully fabricated via a facile and rapid hydrothermal method. Its unique core-shell structure and synergistic effect between multiple components are beneficial for electromagnetic wave absorption. The morphology, elemental composition, microstructure and microwave absorption characteristics were systematically studied. With a filler loading of 20 wt%, the composite presents a minimum reflection loss (R Lmin) of −46.7 dB and an effective absorption bandwidth (EAB) as wide as 5.2 GHz at a thickness of 2.5 mm. The superior absorption ability profits from a special microstructure, good impedance matching, multiple attenuation features, interfacial polarization, and the synergistic effect of dielectric and magnetic loss. Consequently, this work lays a foundation for the design of high-performance electromagnetic wave absorbers with multicomponent heterogeneous structures. [ABSTRACT FROM AUTHOR]

VB‐Group transition metal disulfides (TMDs) are considered excellent materials for electromagnetic wave (EMW) absorption because of their good conductivity and abundant active sites located at their edges and substrates, as compared with VIB‐Group TMDs. Herein, for the first time, EMW absorbers based on VB‐Group NbS2 nanosheets by using a facile one‐step solvothermal method are successfully prepared. The minimum reflection loss (RLmin) can reach up to 43.85 dB with an effective absorption bandwidth of 6.48 GHz (11.52–18.00 GHz). The remarkable EMW absorption performance can also be reflected in the tunable frequency bands (C‐, X‐, and Ku‐bands), which is achieved by adjusting the contents of materials. Furthermore, the influence of the content of 2H‐phase and 1T‐phase in NbS2 on the EMW absorption performance is systematically investigated. The hierarchical hollow‐sphere structure of NbS2 promotes dielectric loss and the multiple reflection and absorption of EMW, and enhances the impedance matching and synergistic attenuation ability. This work demonstrates that the bottleneck of effective absorbing frequency band of single‐component dielectric EMW absorbing materials could be broken through, and paves a novel path towards developing broadband absorbing materials in EMW absorption. [ABSTRACT FROM AUTHOR]

[Display omitted] Absorbing materials can convert electromagnetic wave (EMW) energy into heat and other energy and dissipate it. Carbon materials can attenuate EMW by generating large conduction losses due to their high conductivity. The introduction of low dielectric materials can improve impedance matching caused by high conductivity. However, the density of materials compounded with carbon materials is too large, which affects the overall density of composite materials. Therefore, this problem is solved by matching melamine foam with ZIF-67. As an ultra-light material, the melamine foam-based carbon material can significantly reduce the density of composite materials, and its developed three-dimensional structure can cause multiple scattering of EMW. The large specific surface area and evenly distributed metal oxides obtained after annealing of ZIF-67 can provide ultra-low-density carbon materials and abundant interfacial polarization to further attenuate EMW. So far, the methods of self-growing materials on the surface of melamine foam have not been reported. We prepared a 500 nm Co 3 O 4 nanosheet/carbon foam (CF) composite material coated on the surface by a two-step method. The sample had a maximum reflection loss of −46.58 dB at 10.72 GHz, and an effective absorption bandwidth (EAB) of 5.4 GHz. This research provides a new idea for the growth of porous materials on the surface of melamine foam-based carbon materials. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) carbon-based materials have attracted growing attention in the field of electromagnetic wave absorption applications. However, their high conductivity results in high dielectric constant, leading to impedance mismatching, and this characteristic finally weakens their electromagnetic wave absorption performance. In this work, 3D carbon foam (3DCF) was successfully prepared by calcining the melamine foam as the carbon framework precursor under N 2 atmosphere. Subsequently, 1T-2H MoS 2 nanosheets were uniformly assembled on the surface of the 3DCF skeleton through a solvothermal process. The diameter of the 3DCF skeleton was about 1 μm and the thickness of the 1T-2H MoS 2 on the surface was about 150 nm. The 3D network brings in many advantages for microwave attenuation, including numerous conductive pathways, excellent impedance matching and multi-polarization processes. The composites exhibited a maximum reflection loss (RL max) of −45.88 dB at 10.2 GHz with the thickness of 2.2 mm, and the effective absorbing bandwidth (E AB) was as wide as 5.68 GHz, implying their superb microwave absorption behavior. This work is believed to offer a strategy for the design of efficient 3D electromagnetic wave absorbers with low density in the future. [ABSTRACT FROM AUTHOR]

Highlights: A facile one‐step hydrothermal method for producing gram‐scale 1T@2H-MoS2 by imbedding the guest molecules and ions was developed. The influence of different MoS2 phase for electromagnetic absorbing properties was explored by analyzing electromagnetic parameters of 1T/2H MoS2 and 2H MoS2 with 50%, 40%, 30%, 20%, 15%, and 10% filler loading. Taking the advantage of 1T/2H MoS2, the flexible CF@1T/2H MoS2 was also synthesized to mind the request of flexible portable microwave absorption electronic devices.Phase engineering is an important strategy to modulate the electronic structure of molybdenum disulfide (MoS2). MoS2-based composites are usually used for the electromagnetic wave (EMW) absorber, but the effect of different phases on the EMW absorbing performance, such as 1T and 2H phase, is still not studied. In this work, micro-1T/2H MoS2 is achieved via a facile one-step hydrothermal route, in which the 1T phase is induced by the intercalation of guest molecules and ions. The EMW absorption mechanism of single MoS2 is revealed by presenting a comparative study between 1T/2H MoS2 and 2H MoS2. As a result, 1T/2H MoS2 with the matrix loading of 15% exhibits excellent microwave absorption property than 2H MoS2. Furthermore, taking the advantage of 1T/2H MoS2, a flexible EMW absorbers that ultrathin 1T/2H MoS2 grown on the carbon fiber also performs outstanding performance only with the matrix loading of 5%. This work offers necessary reference to improve microwave absorption performance by phase engineering and design a new type of flexible electromagnetic wave absorption material to apply for the portable microwave absorption electronic devices. [ABSTRACT FROM AUTHOR]

The feasibility of beam-shaping of a Ku-Band horn as a transmitting (Tx) antenna by mounting two different versions of lenses which are kind of Fresnel Zone Plates (FZP) is studied. The designed and fabricated geometrical structures offer a simpler approach building Fresnel Zone Plates by using an electromagnetic wave absorber and diffractive optic material. The diffractive optic material, paraffin, forms a set of alternating open and opaque annular zones on a flat surface, based on the design principles of Fresnel Zone Plates. An electromagnetic wave absorber covers the top surface of the formed paraffin, but not including the grooves. Thereafter, the Fresnel Zone plates are suitably attached in front of the transmitter horn antenna, located in the far-field region of a receiving antenna. The half-power beam-widths for the horn antenna (unloaded) and with two types of lenses are investigated. The results indicate that Fresnel zone plate structures can play a role suppressing side lobes in H-plane so that the effective radiation is to be significantly concentrated. [ABSTRACT FROM AUTHOR]

• Composite was prepared by coordinate combination to improve the agglomeration phenomenon. • The impedance matching of composites was optimized by constructing mesoporous structures and regularized surface structures. • The absorption mechanism of the composite was explained by analyzing electromagnetic parameters and microscopic morphology. • The reflection loss and effective absorption bandwidth of the composites are −48.5 dB and 4.52 GHz, respectively. Biomass carbon has been widely studied as an electromagnetic wave-absorbing material in recent years due to its wide range of material sources, natural porous structure, and other advantages. Herein, a series of magnetic lignin-based carbon composites have been prepared as electromagnetic wave absorbers using carboxylation lignin as an organic ligand and Fe, Co as a metal ion. The bimetallic to coordinate combination with carboxylation lignin improved the agglomeration phenomenon, optimized mesoporous structure, and the pore distribution of the material compared to monometallic. This lignin-based FeCo@C had an abundant interfacial, mesoporous structure, dielectric, and magnetic loss capability. When the ratio of Fe and Co was 1:1, the reflection loss value of −48.5 dB at 12.3 GHz, and the effective absorption bandwidth achieved 4.52 GHz with a thickness of 2.5 mm. In short, this work provided a new direction for the preparation of renewable and high-performance lignin-based electromagnetic wave absorber materials. [ABSTRACT FROM AUTHOR]

Associated with the unique structure and superior properties of zeolitic imidazolate frameworks (ZIFs) of Co-based metal-organic frameworks (MOFs), we synthesized the MWCNTs@carbonaceous CoO composites of a 3D interconnected network using multi-walled carbon nanotubes (MWCNTs) as decoration through the wet chemical and pyrolysis method. Due to the mutual coordination between proper magnetic loss and strong dielectric loss together with perfect impedance match, the MWCNTs@carbonaceous CoO composites exhibit the maximal reflection loss (RL) value of −50.2 dB with 1.84 mm thickness at 14.3 GHz, absorbing bandwidth (RL ≤ −10 dB) of 13.2 GHz (4.8–18 GHz) with respect to 1.0–4.0 mm thickness range. More importantly, the content of composites added to paraffin matrix is merely 10 wt%. In addition, the synergistic effect between CoO NPs and MWCNTs is also beneficial to the highly efficient electromagnetic (EM) wave absorption of the composites. Therefore, the obtained CoO NPs/MOF-derived composites with lightweight and thin performance can be an attractive candidate of the EM wave absorptive materials. Unlabelled Image • MWCNTs@carbonaceous CoO composite is prepared via wet chemical and pyrolysis method. • The composite can reach −50.2 dB at 14.3 GHz with the thickness of 1.84 mm. • The composite exhibits a bandwidth of 13.2 GHz at RL ≤ −10 dB in the range of 1.0–4.0 mm. • The composite shows a good performance of impedance match. [ABSTRACT FROM AUTHOR]

Abstract The dielectric-dielectric composite (SRGA) for electromagnetic absorber was fabricated via integrating Ag(I)-Schiff base coordination compounds (SSBCC) with three-dimensional reduced graphene aerogel (3D-rGA) powders. SRGA showed excellent electromagnetic wave absorption properties in terms of reflection loss, absorption band width and absorber thickness. Specially, when the mass ratio of SSBC to 3D-rGA powders was 1:3 (SRGA-25), the maximum value of reflection loss at 2 mm was up to −63.82 dB and the effective frequency bandwidth of 6.28 GHz (10.16–16.44 GHz) at 2.5 mm can be obtained. The mechanism investigation of electromagnetic wave absorption for SRGA showed that the enhanced electromagnetic wave absorption was ascribed to enhanced polarization loss derived from good 3D-conductive-network units of 3D-rGA, abundant interfaces caused by the media heterostructure due to the introduction of SSBCC and the good impedance matching condition. And 3D-rGA based materials might be put into practical application only in powder state due to the very low strength of the buck state. Therefore, the investigation on SRGA in our contribution is considered to be an actual performance evaluation of the materials based on three-dimensional graphene for microwave attenuation. This work also provided a method for fabricating excellent graphene-based electromagnetic wave absorbers by simply mixing a suitable dielectric lossy material, e.g. SSBCC. Graphical abstract Image 1 Highlights • The preparation method of SRGA through mixing components is simple. • 3D-rGA powers overcome the limitation of low strength of graphene aerogel. • Schiff base enhances dielectric properties and makes SRGA good impedance matching. • The max RL at 2 mm is up to −63.82 dB and the effective bandwidth reaches 6.28 GHz. [ABSTRACT FROM AUTHOR]

In this study, a novel electromagnetic (EM) wave absorbing composite sandwich structure and its application process are proposed. The composite sandwich can be applied to the outer part of structures as a final surface treatment through a secondary bonding process, and this covers all the surface components that illuminate the incident EM waves. This process improves the structural material properties of the original components and their durability against the environment in contrast to EM wave absorbing paint or patch. With the help of EM wave absorbing characteristics and continuous impedance of the composite sandwich structures, the EM signals from reflection, diffraction, and scatter decrease effectively. The outer skin of the composite sandwich includes a resistive periodic patterned sheet prepared using printed electronics, and a low-dielectric foam is adopted as the core material. This composite is designed based on the equivalent circuit theory and is subsequently fabricated. The EM characteristics are tested after application on an aircraft skin structure through a secondary bonding process. The measurement of reflection loss and image processing of the reflected signal show that this composite and application process decrease the EM wave reflections from the original structure significantly. [ABSTRACT FROM AUTHOR]

Abstract In the present study, an electromagnetic (EM) wave absorber was fabricated with a multi-walled carbon nanotube (MWNT)-incorporated cement composite and the absorbing capability of the absorber was assessed. To disperse MWNTs in a cement matrix, composites were fabricated under a low flow condition of the fresh mixture, and silica fume (SF) was added to explore the influence of SF addition on MWNT distribution. The electrical conductivity of the composite was evaluated to examine the MWNT distribution and the complex permittivity was determined to study the EM characteristics of the composite. The conductivity results demonstrated that SF addition of 10 wt% led to the greatest enhancement. Meanwhile, the absorber was designed on the basis of complex permittivity at a frequency point of 9.4 GHz, and SF0-M1.0 type (no SF addition and MWNT content of 1.0 wt%) and SF10-M0.6 type (SF content of 10 wt% and MWNT content of 0.6 wt%) were employed. The experimental assessment of the absorbing capability demonstrated that the −10 dB bandwidths of SF0-M1.0 and SF10-M0.6 type absorbers were 2.5 GHz and 3.2 GHz, respectively. In addition, the absorbing capability derived from the experimental work was compared and validated by means of computational simulation work. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile method to prepare Co@CNs with core-shell porous structure by heat treatment of Z@P nanocomposites. • The RL min of Co@CN-60 is −59.08 dB at 17.66 GHz with a thickness of only 1.7 mm. • The effective absorption bandwidth is broadened ranging from 15.19 to 9.41 GHz (5.78 GHz) when the thickness is 2.3 mm. • The porous core-shell structure of Co@CN-60 not only consume the EMW, but also improve the impedance matching. N-doped porous core-shell nanocomposite is considered to be a competent candidate for the absorbing of electromagnetic wave (EMW). In this work, polydopamine (PDA) wrapped ZIF-67 (Z@P) precursors with the core-shell structure were obtained through ZIF-67 triggered dopamine self-polymerization. After high-temperature pyrolysis treatment, the N-doped graphitized carbon layers wrapped cobalt (Co@CNs) absorber with porous structure was obtained, which exhibited high efficiency and adjustable EMW absorbing properties. The minimum reflection loss (RL min) of Co@CN-60 approached −59.08 dB at 17.7 GHz with a thickness of 1.7 mm. The effective absorption bandwidth (EAB) reached 5.8 GHz with a corresponding thickness of 2.3 mm. Besides, the RL min of Co@CN-90 reaches −44.07 dB at 14.5 GHz (thickness 2.0 mm), and the EAB is 5.9 GHz. Therefore, the porous core-shell Co@CNs nanocomposite is expected to be a promising EMW absorption material. [ABSTRACT FROM AUTHOR]

W-type Sr-hexaferrites, Sr 0.75 Ca 0.25 Zn 2- x Co x Fe 16 O 27 (0.0 ≤ x ≤ 2.0), were synthesized, and their magnetic and electromagnetic (EM) wave absorption properties were investigated. As x increased from 0.0 to 2.0, the saturation magnetization value increased and reached a maximum at x = 1.25, followed by a decrease, while the magnetic anisotropic field (H ani) decreased and showed a minimum at x = 1.0, then increased again. The variation in H ani could be controlled by adjusting the value of x , which also changed the ferromagnetic resonance (FMR) frequency and enabled control over the frequency band of EM wave absorption. It is demonstrated that the EM wave absorption is primarily controlled by imaginary part of permeability (μ") induced by FMR. Composite of the W-type hexaferrite-epoxy (10 wt%) with x = 0.75–2.0 showed a broad-band EM wave absorption in the 1–18 GHz range, while the composites with x = 0–0.4 showed it in the 26.5–40 GHz. The x = 1.25 sample satisfied RL < − 10 dB in the 7–17 GHz range with a thickness of 2.1 mm, while x = 0.3 sample satisfied RL < − 10 dB in the 27–39 GHz with a thickness of 0.8 mm. Sr 0.75 Ca 0.25 Zn 2- x Co x W is a very promising material for tunable wideband EM wave absorbers in 1–40 GHz range. • H ani of Sr 0.75 Ca 0.25 Zn 2- x Co x W could be controlled by Co-doping level x , which also changed the FMR frequency. • EM wave absorption is primarily controlled by μ" induced by FMR. • Sr 0.75 Ca 0.25 Zn 2- x Co x W-epoxy composites exhibited tunable and broad-band EM wave absorption within 1–40 GHz range. [ABSTRACT FROM AUTHOR]

Two-dimensional nanomaterial MXene Ti 3 C 2 T x with excellent electrical conductivity has received extensive attention in the electromagnetic wave (EMW) absorption field. However, the excessively high permittivity of Ti 3 C 2 T x is not conducive to impedance matching and the absorption of EMW. Considering the low permittivity and mesoporous structure of MOF, in this work, Co/La-MOF were in situ growth on the surfaces of Ti 3 C 2 T x by a facile co-solvothermal method. The obtained Co/La-MOF anchored on Ti 3 C 2 T x (Co/La-MOF/Ti 3 C 2 T x) composite exhibits low density with excellent EMW absorption performance. Co/La-MOF/Ti 3 C 2 T x -2 (Co2+/La3+ mass ratio of 16:3) shows the minimum reflection loss of − 44.15 dB at 4.00 GHz with the effective absorption bandwidth of 3.67 GHz in the frequency range of 14.03–17.70 GHz under 1.3 mm. In addition, the electromagnetic absorption mechanism of Co/La-MOF/Ti 3 C 2 T x was also investigated. It provides an effective strategy for the preparation of a novel absorber with high EMW absorbing performance. • Two-dimensional Ti 3 C 2 T x MXene and Co/La-MOF with porous structure were synthesized by in-situ growth method. • Co/La-MOF/Ti 3 C 2 T x exhibits an excellent electromagnetic absorption performance. • The RL min of Co/La-MOF/Ti 3 C 2 T x is − 44.15 dB at 4.00 GHz under 4.5 mm, the EAB is 3.67 GHz under 1.3 mm. • EMW absorption performance of samples can be regulated by adjusting the Co2+/La3+ mass ratio. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI)-coated Y 3 Fe 5 O 12 (YIG)/CoFe 2 O 4 (CFO) hybrid composites were synthesized via sol-gel and oxidative polymerization methods to achieve advanced microwave absorption properties. The structural, morphological, magnetic, and microwave absorption characteristics of the resulting samples were analyzed by performing X-ray diffraction (XRD), scanning electron microscopy (SEM), vibration sample magnetometer (VSM), and vector network analyzer (VNA). XRD results revealed that CFO and YIG have cubic crystal structures with Fd3m and Ia3d space symmetry, respectively, with an average crystallite size of 35.3 nm and 42.9 nm. The Ferro/ferrimagnetic signals were detected from the ferrite samples' room temperature magnetic hysteresis loops. The incorporation of PANI and YIG into the composites resulted in a decrease in their magnetic saturation (M s) and coercive field (Hc) values. VNA measurements demonstrated that nearly all samples achieved 90% absorption (≤−10 dB) of incident electromagnetic waves throughout the X -band frequency range. The minimum reflection loss (RL min) value reaches − 47.34 dB at 8.14 GHz, with an effective bandwidth of 4.00 GHz, covering the entire X -band and beyond. These impressive absorption characteristics suggest that the manufactured composites possess potential as viable candidates for defense applications conducted at X -band frequency. [Display omitted] • PANI/[YIG x /CFO 1−x ] hybrid composites were synthesized by in-situ polymerization of aniline followed by the sol-gel route. • All manufactured samples, except PYC06, absorb 90% of incident EMW through X-band frequency. • The RL min value is found as − 47.34 dB at 8.14 GHz with effective bandwidth of 4.00 GHz (entire X-band) for PYC02 sample [ABSTRACT FROM AUTHOR]

Recently, with the pursuit of high-efficiency electromagnetic wave absorption (EMWA) and electrochemical energy storage (EES) materials, multifunctional lignin-based composites have attracted significant interest due to their low cost, vast availability, and sustainability. In this work, lignin-based carbon nanofibers (LCNFs) was first prepared by electrospinning, pre-oxidation and carbonization processes. Then, different content of magnetic Fe 3 O 4 nanoparticles were deposited on the surface of LCNFs via the facile hydrothermal way to produce a series of bifunctional wolfsbane-like LCNFs/Fe 3 O 4 composites. Among them, the synthesized optimal sample (using 12 mmol of FeCl 3 ·6H 2 O named as LCNFs/Fe 3 O 4 –2) displayed excellent EMWA ability. When the minimum reflection loss (RL) value achieved −44.98 dB at 6.01 GHz with an thickness of 1.5 mm, and the effective absorption bandwidth (EAB) was up to 4.19 GHz ranging from 5.10 to 7.21 GHz. For supercapacitor electrode, the highest specific capacitance of LCNFs/Fe 3 O 4 –2 reached 538.7 F/g at the current density of 1 A/g, and the capacitance retention remained at 80.3 %. Moreover, an electric double layer capacitor of LCNFs/Fe 3 O 4 –2//LCNFs/Fe 3 O 4 –2 also showed a remarkable power density of 7755.29 W/kg, outstanding energy density of 36.62 Wh/kg and high cycle stability (96.89 % after 5000 cycles). In short, the construction of this multifunctional lignin-based composites has potential applications in electromagnetic wave (EMW) absorbers and supercapacitor electrodes. [Display omitted] • Bifunctional wolfsbane-like composites were prepared as electromagnetic wave absorbers and supercapacitor electrodes. • Increasing magnetic Fe 3 O 4 nanoparticles contents in the composites optimized the properties of EMWA and EES. • The optimal sample exhibited the minimum RL value of -44.98 dB at 6.01 GHz with an thickness of 1.5 mm. • In three-electrode, the best sample displayed high specific capacitance of 538.7 F/g at the current density of 1 A/g. • In two-electrode, an outstanding energy density of 36.62 Wh/kg at the power density of 7755.29 W/kg was achieved. [ABSTRACT FROM AUTHOR]

Recently, multifunctional lignin-based materials are gaining more and more attention due to their great potential for low-cost and sustainability. In this work, to obtain both an excellent supercapacitor electrode and an outstanding electromagnetic wave (EMW) absorber, a series of multifunctional nitrogen-sulphur (N-S) co-doped lignin-based carbon magnetic nanoparticles (LCMNPs) had been successfully prepared through Mannich reaction at different carbonization temperature. As compared with the directly carbonized lignin carbon (LC), LCMNPs had more nano-size structure and higher specific surface area. Meanwhile, with the increase of carbonization temperature, the graphitization of the LCMNPs could also be effectively improved. Therefore, LCMNPs-800 displayed the best performance advantages. For the electric double layer capacitor (EDLC), the optimal specific capacitance of LCMNPs-800 reached 154.2 F/g, and the capacitance retention after 5000 cycles was as high as 98.14 %. When the power density was 2204.76 W/kg, the energy density achieved 33.81 Wh/kg. In addition, N-S co-doped LCMNPs also exhibited strong electromagnetic wave absorption (EMWA) ability, whose the minimum reflection loss (RL) value of LCMNPs-800 was realized −46.61 dB at 6.01 GHz with an thickness of 4.0 mm, and the effective absorption bandwidth (EAB) was up to 2.11 GHz ranging from 5.10 to 7.21 GHz, which could cover the C-band. Overall, this green and sustainable approach is a promising strategy for the preparation of high-performance multifunctional lignin-based materials. [Display omitted] • Multifunction N-S co-doped LCMNPs were prepared as supercapacitor electrode and electromagnetic wave absorber. • Increasing the carbonization temperature was an effective strategy for preparing multifunction N-S co-doped LCMNPs. • LCMNPs-800 could display high specific capacitance of 474.8 F/g at a current density of 0.5 A/g. • LCMNPs-800 could exhibit excellent cycling stability of 98.14 % after 5000 cycles. • The minimum RL reach −46.61 dB at 6.01 GHz with an EAB of 2.11 GHz at a thickness of 4.0 mm. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, the periodic structure-based absorber operating at dual-band or more for applying to new electromagnetic wave measurement facility that does not contain a conventional pyramidal absorber is presented. To achieve the objective, the absorber structure takes the format of two-layer periodic surfaces. Based on the logical design principles, the parametric study results to obtain the desired performance and the final experimental result are addressed. The measured result shows a broadband reflectivity characteristic from 0.60 to 3.27 GHz on the basis of below −10 dB. As a result, the absorber shows the performance supporting CDMA, WCDMA, and WLAN bands in the electromagnetic wave measurement facility. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:478-481, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT We propose an electrically frequency tunable absorber (EFTA) with varactor diodes, which can provide good absorption properties even in much higher frequency bands than conventional EFTAs. In general, conventional EFTAs cannot guarantee high absorption rate beyond a certain frequency limited by high capacitance of commercial varactor diodes. In this letter, however, we suggest a simple but fairly effective way to overcome the high frequency limit by intentionally inserting parasitic capacitance introduced from multiple slits. The parasitic capacitance connected to the varactor diodes in series can decrease overall capacitance to an optimum value. Consequently, we not only can maintain good absorption rate in a very high frequency region, but also freely select a target absorption frequency band by modifying the number of slits. Experiments for normal and oblique incidence have been carried out to validate the proposed method. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:145-148, 2017 [ABSTRACT FROM AUTHOR]

The electromagnetic wave absorption properties of single- and double-layer silver nanoparticle/carbon nanotube (Ag/CNT) nanocomposites were evaluated. The reflection loss (R.L.) of the samples was calculated based on the measured complex permittivity and permeability. The double-layer composites constructed from CNT 30 wt.% and Ag/CNT 30 wt.% with total thickness of 3.3 mm showed a minimum R.L. of ∼−52.9 dB (over 99.999% absorption) at 6.3 GHz. The bandwidth of reflection loss less than −10 dB was observed at 3 regions, with wideness of 3.5, 0.8, and 1.5 GHz. Thin absorber with large R.L. and wide response bandwidth at low and high frequency regions can be obtained with double-layer composites. The capability to modulate the absorption and bandwidth of these samples to suit various applications in different frequency bands indicates that these nanocomposites could be an excellent electromagnetic wave absorber. [ABSTRACT FROM AUTHOR]

The electromagnetic wave absorption properties of double-layer barium titanate/carbon nanotube (BTO/CNT) nanocomposites were evaluated. The BTO/CNT nanomaterials were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. The reflection loss ( R.L. ) of the samples was calculated based on the measured complex permittivity and permeability. The minimum R.L. of single-layer BTO/CNT 30 wt% nanocomposites sample with a thickness of 1.1 mm reached ~−30.3 dB (over 99.9% absorption) at 13.8 GHz, and the bandwidth of the reflection loss less than −10 dB (over 90% absorption) was 1.5 GHz. The double-layer composites consist of BTO/CNT 30 wt% (absorption layer) with thickness of 1.0 mm and BTO 30 wt% (matching layer) with thickness of 0.3 mm showed a minimum R.L. of ~−63.7 dB (over 99.9999% absorption) at 13.7 GHz, and the bandwidth of the reflection loss less than −10 dB was 1.7 GHz. Wider response bandwidth, >1.7 GHz also can be achieved with different designs of double-layer absorbers. The R.L. significantly improved and wider response bandwidth can be obtained with double-layer composites. The capability to modulate the absorption and bandwidth of these samples to suit various applications in different frequency bands indicates that these nanocomposites could be an excellent electromagnetic wave absorber. [ABSTRACT FROM AUTHOR]

A wideband switchable frequency selective surfaces (FSS) absorber/reflector for C-band (4–8 GHz) application of smart stealth system is presented. This switchable FSS has novel properties that combine wideband absorption and switchable performance over the entire operational band. Nested treble split-rings are used to accomplish wideband and switchable performance of normal incidence. The split-rings are coupled together to create broadband resonance based on effect of superimposed resonance. By switching connected state of above split using PIN diodes in the outmost ring, we are able to control the working state of FSS. In OFF state, the switchable FSS works as a wideband absorber. The −9 dB bandwidth is 3.2 GHz (4.1–7.3 GHz). In ON state, the switchable FSS has fine reflective property. The average reflectivity is −2.8 dB in the operational band. The switchable FSS is computed by full-wave numerical simulation. The samples are fabricated and tested to verify the proposed concept. The experimental result is found to be consistent with computed result. [ABSTRACT FROM AUTHOR]

• (PEA) 2 PbBr 4 /CNTs with an ultra-wide absorption bandwidth (5.12 GHz). • Polarization loss in conductive network construction. • The first study of 2D perovskite as microwave absorber. • Expand the application field of 2D perovskite. Two-dimensional (2D) hybrid halide perovskites have shown great potential for application in the field of electromagnetic wave (EMW) absorption thanks to their inherent high-equilibrium electron hole and electron mobility as well as enhanced water-resistance and photo-stability. However, research on the application in EMW absorption has never been reported. Here, we first design the (PEA) 2 PbBr 4 /CNTs wave-absorption system. By adjusting the component ratio, the 2D perovskite-based composite shows an excellent wave absorbing performance. The maximum effective absorption bandwidth reaches 5.12 GHz at 1.74 mm (12.28–17.40 GHz) and a minimum reflection loss of −56.88 dB at 1.90 mm, respectively, as the component mass ratio is 12:1. This outstanding performance is attributed to the combined action of multiple loss mechanisms and provide a great potential of 2D perovskite for application in EMW absorption. [ABSTRACT FROM AUTHOR]

Barium titanate/carbon nanotube (BTO/CNT) hybrid nanocomposites were fabricated by sol–gel method. The BTO/CNT hybrid nanomaterials were characterized using X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, Raman and X-ray photoelectron spectroscopy. The BTO/CNT hybrid nanomaterials were then loaded in paraffin wax with different weight percentage, and pressed into toroidal shape with thickness of 1.0 mm to evaluate their complex permittivity and complex permeability using vector network analyzer. The reflection loss of the samples was calculated according to their measured complex permittivity and permeability. The minimum reflection loss of the BTO/CNT 60 wt.% hybrid nanocomposites sample with a thickness of 1.0 mm reached 29.6 dB (over 99.9% absorption) at 13.6 GHz, and also exhibited a wide response bandwidth where the frequency bandwidth of the reflection loss of less than −10 dB (over 90% absorption) was from 12.1 to 13.8 GHz. The BTO/CNT 60 wt.% hybrid nanocomposites with thickness of 1.1 mm showed a minimum reflection loss of ∼−56.5 dB (over 99.999% absorption) at 13.2 GHz and was the best absorber when compared with the other samples of different thickness. The reflection loss peak shifted to lower frequency and wider response bandwidth can be obtained as the thickness of the samples increased. The capability to modulate the absorption band of these samples to suit various applications in different frequency bands simply by manipulating their weight percentage and thickness indicates that these hybrid nanocomposites could be a promising electromagnetic wave absorber. [ABSTRACT FROM AUTHOR]

Hierarchical structural design has been proved to be a new strategy for fabricating high-performance microwave absorbers, so some researchers use low–dimensional components to construct continuous networks for better performance. In this work, the novel hierarchical carbon fibers@ZIF–67@MoS 2 film with tunable and efficient electromagnetic wave (EMW) absorption performance was obtained by the electrostatic spinning of ZIF–67 in the interior of carbon fibers and subsequent hydrothermal of MoS 2. By the synergistic effects from the ZIF–67 particles increasing the magnetic loss and MoS 2 at the outer layer improving the impendence matching, the absorption property of CPZM–1 could be summarized as follow: the optimal reflection loss(RL) was −72.7 dB with a thickness of 2.6 mm at 10.0 GHz and the corresponding effective absorption bandwidth (EAB) of 9.8 GHz covered whole X and Ku band. Moreover, by adjusting the load of ZIF–67, CPZM–5 achieved the maximum EAB of 12.5 GHz. [ABSTRACT FROM AUTHOR]

Abstract: Sm2O3/α-Fe/Sm2Fe17N x composites were prepared in situ by hydrogenation–disproportionation–oxygen-desorption–recombination and nitrogen process, and their electromagnetic wave absorption properties were measured in the frequency range of 0.5–18GHz. The result showed that saturation magnetization and coercivity of as-prepared powder with 25.3wt% Sm2O3, 64.4wt% α-Fe and 10.3wt% Sm2Fe17N3 were 134.57emu/g and 654.5G, respectively. The dielectric constant of composites was low over the frequency range of 0.5–18GHz, and their resonance frequencies were at a high frequency range. The resin composite of Sm2O3/α-Fe/Sm2Fe17N3 exhibited effective electromagnetic wave absorption (RL≤20dB) in a frequency range 3–9GHz, for absorber thickness ranging from 3 to 8mm, respectively. A minimum reflection loss of −53dB from the samples was observed at 7GHz with an absorber thickness of 3.59mm. [Copyright &y& Elsevier]

This article shows some results related to the optimum design of a multilayered electromagnetic absorber, in the frequency range between 0.85 GHz and 5.4 GHz, which belongs to wireless communications. For this design, the Unified Particle Swarm Optimization (UPSO) metaheuristic was used. The results agree with those previously obtained using the standard Particle Swarm Optimization (PSO) algorithm and the deterministic method of interval analysis, which were previously reported. An important reduction on computation time was achieved, although a limited results reproducibility persists. [ABSTRACT FROM AUTHOR]

Abstract: SmN/α-Fe/Sm2Fe17N3 composites were prepared in situ by heating of Sm2Fe17N3 powders, and their electromagnetic wave absorption properties were measured in the frequency range of 0.5–18GHz. The result shows that saturation magnetization and coercivity of as-heated powder with 23.7wt% SmN, 58.5wt% α-Fe and 17.8wt% Sm2Fe17N3 are 130.82emu/g and 750Oe, respectively. The dielectric constant of composites was low over the frequency range of 0.5–18GHz, and their resonance frequencies were at a high frequency range. The effective electromagnetic wave absorption (RL<−20dB) of the compact sample with thickness of 0.7–3.2mm prepared with the SmN/α-Fe/Sm2Fe17N3 and resin was obtained in a frequency range of 5.5–16GHz. A minimum reflection loss of −33dB of the samples was observed at 5.5GHz with an absorber thickness of 3.2mm. [Copyright &y& Elsevier]

Abstract: The frequency dependences of the relative complex permeability , the relative complex permittivity and the absorption characteristics for composite electromagnetic wave absorbers made of polystyrene resin and sendust particles or permalloy particles were investigated in the frequency range from 1 to 40GHz. The size of sendust particles was varied between approximately 5 and 20μm and the particle size dependence of was observed. The value of was shown to be controlled by adjusting the particle size of sendust, and an electromagnetic wave absorber with a flexible design was proposed. A metal-backed single-layer absorber made of sendust particles or permalloy particles absorbed more than 99% of electromagnetic wave power at frequencies above 20GHz. In addition, a composite made of 5μm particles exhibited a return loss of less than −20dB in the frequency range of not only several GHz but also above 30GHz. [Copyright &y& Elsevier]

Abstract: Extraction of rare earth elements from the Nd–Fe–B magnet scraps through the chlorination with NH4Cl was performed to study the effective process for reusing metal iron as well as rare earths. The Nd2Fe14B primary phase was selectively converted to NdCl3 in ca. 90% yield, together with α-Fe and Fe–B solid residues by chlorinating at 573K for 3h. The resin compacts prepared from the resultant solid residues mainly composed of the α-Fe phase provided the good electromagnetic wave absorption properties. [Copyright &y& Elsevier]

A new double-sided electromagnetic wave absorber allowing transmission is proposed. In the conventional permeable wave absorber, a resistive film is attached to a lossless dielectric layer. However, this is not nonreflective for an incident wave on the resistive film side. In the present paper, a basic structure is considered in which there is no reflection on both sides of the absorber. A simple structure made of two resistive films inserted between three dielectric layers is proposed. The nonreflection condition of the present wave absorber is derived by means of the equivalent circuit, and the reflection and transmission characteristics are derived for given permittivities of the dielectric layers. It is found that the bandwidth of the reflection coefficient does not significantly depend on the permittivity of the inner layer and that the permittivity of the outer layers is increased and that of the inner layer is decreased in order to make the transmission coefficient smaller. The wave absorber is fabricated and measured for confirmation of the validity of the theory. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(6): 1–8, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20369 [ABSTRACT FROM AUTHOR]

In order to create an electromagnetic wave absorber that does not depend on the frequency dispersions of the material parameters, this paper proposes an absorber based on the concept of the microwave integrated circuit. Detailed studies of the matching characteristics are attempted by theory and experiment. Microchip resistors serving as basic circuit elements are placed on a substrate and an electromagnetic wave absorber is developed in which the inductance and capacitance are realized in the microwave sense. A spatial experiment is conducted for this absorber. It is found possible to achieve a broadband matching characteristic over a relative bandwidth of 55% by making use of the dual peak characteristics for a matching center frequency of 3.5 GHz and a reflection coefficient of -20 dB. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 89(12): 26–33, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20257 [ABSTRACT FROM AUTHOR]

Abstract: Elements such as B, Li and Na were doped to barium titanate, BaTiO3 in order to control dielectric dispersion. Addition of 3mol% Li2O lowered the dispersion at frequency of 0.53MHz, while addition of 3mol% B2O3 or Na2O did not affect dispersion frequency. BaTiO3 doped with 0.3mol% Li2O showed dielectric dispersion at around 2.5GHz. An electromagnetic (EM) wave absorber using the doped BaTiO3 plate was tried to produce for millimeter frequency range. A matching layer of 0.5mm thick ceramic plate with relative permittivity 21 was attached to it to suppress reflection of incident EM wave due to the discontinuity at the boundary between the BaTiO3 and air. The obtained EM wave absorber had reflectivity of −45dB at 31GHz and −25dB at 95GHz, respectively. [Copyright &y& Elsevier]

When the measurement wavelength becomes longer, it becomes difficult to maintain a sufficient measurement space in the spatial standing wave method used for reflection coefficient measurement of electromagnetic wave absorbers. To date, a reflection coefficient measurement method using a spherical wave within a rather narrow space has been proposed. However, no theoretical verification has been carried out. In this paper, the spatial standing wave is analyzed by the physical optics approximation (PO) and the FDTD method when the distance between the transmitting antenna and the measuring material is set in the Fresnel region. The analytical results are compared with the experimental results. When a conductive plate is utilized as measuring material, the spatial standing wave distributions analyzed by PO and FDTD method, the measured distributions correlate well in terms of their tendencies. From experiments carried out with several types of electromagnetic wave absorbers at 600 to 2000 MHz, it is found that the reflection coefficient of the material can be determined by the spatial standing wave at about 1 to 2.5 wavelengths in front of the material. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(8): 40–49, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10081 [ABSTRACT FROM AUTHOR]

Ferrite electromagnetic wave absorbers are widely used for electromagnetic half reflectionless rooms for EMC measurement and anechoic chambers. If gaps exist between the ferrite tiles, the return loss characteristics are substantially degraded in the low-frequency region between 30 and 200 MHz. In this article, the effects of the gap in ferrite tiles on the return loss characteristics are studied for grid-type ferrite absorbers and planar ferrite absorbers. From the numerical simulations, it is found that the degradation of the characteristics due to the gaps is smaller in the grid-type ferrite absorbers than in the planar ferrite absorbers at low frequencies. This finding is also confirmed by model experiments. Further, filling of the gaps with ferrite powder is studied as a means of reducing the degradation of the characteristics by the gaps. © 2000 Scripta Technica, Electron Comm Jpn Pt 2, 83(2): 52–60, 2000 [ABSTRACT FROM AUTHOR]

The purpose of this study is to prepare a resistive lossy material using conducting polymers for electromagnetic wave absorbers. This paper presents a conductive paste largely composed of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) with a polyurethane binder. The various secondary compounds are added in small amounts to an aqueous blended solution in order to enhance the electrical and mechanical properties of the conductive thin film. The synthesized conductive paste is characterized through electrical, chemical, and morphological analyses. The electrical conductivity of the thin film is measured using a four-point probe and surface profiler. The chemical and morphological changes are studied in various experiments using a Raman microscope, X-ray photoelectron spectroscopy, a scanning electron microscope, and an atomic force microscope. In order to verify the applicability of the synthesized conductive paste, which is composed of 70 wt% PEDOT:PSS, 30 wt% polyurethane, and secondary additives (DMAE 0.4 wt%, A-187 0.5 wt%, DMSO 7 wt%, Dynol 604 0.1 wt%, PUR 40 2.5 wt%), the Salisbury screen absorber is fabricated and evaluated in the X-band. According to the results, the absorber resonates at 9.7 GHz, the reflection loss is −38.6 dB, and the 90% absorption bandwidth is 3.4 GHz (8.2 to 11.6 GHz). Through this experiment, the applicability of the PEDOT:PSS-based conductive paste is sufficiently verified and it is found that excellent radar-absorbing performance can be realized. [ABSTRACT FROM AUTHOR]

• BN nanosheets decorated N-doped CNFs are formed to improve their impedance match. • RL of the hybrid with 10 wt% is −58.41 dB at 1.6 mm and EAB is 5.76 GHz at 1.75 mm. • Enhance property is due to the 1D structure, abundant interface and many defects. [Display omitted] Carbon nanofibers are widely used for electromagnetic wave (EMW) absorption. However, it is still worthy attention for rationally optimizing their permittivity. Herein, a satisfactory EMW absorber of few-layer BN nanosheets decorated N-doped carbon nanofibers (BNNS-CNFs) was successfully prepared by electrospinning-assisted synthetic technology. The permittivity of CNFs can be adjusted by introducing of BNNS and N-doped in carbon matrix. As a EMW absorber, BNNS-CNFs/paraffin hybrid with a low filling ratio of 10 wt% shows excellent absorption performances. The minimum reflection loss (RL) is about −58.41 dB at a thickness of 1.6 mm and the widest absorption bandwidth (RL<−10 dB) of 5.76 GHz can be obtained at 1.75 mm. The significant enhancement of EMW absorption performance is mainly attributed to the improvement of impedance match and multiple polarizations after introduction of BNNS and more defects by N-doped. Thus, BNNS-CNFs with lightweight and wide-band at low load content would be utilized as a high-efficiency EMW absorber. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to demonstrate the electromagnetic wave absorption characteristics of powder-type magnetic wood by changing the mixing ratios for the Mn-Zn ferrite and Ni-Zn ferrite powder. The results show that the matching frequency of the electromagnetic wave absorption characteristics can be controlled by changing the mixing ratios of the magnetic materials and the thickness of the board. We obtained electromagnetic wave absorption of close to 20 dB over the 2.5 GHz–6.2 GHz frequency range. The powder-type magnetic wood boards used in these experiments satisfy JIS standards for wood surface materials in terms of bending strength and deflection. The results from our studies can be used to design indoor powder-type magnetic wood wave absorbers for a specified absorption frequency. [ABSTRACT FROM AUTHOR]

Abstract: Substituted barium hexaferrite BaMg0.25Mn0.25Co0.5Ti1.0Fe10O19 was prepared in powder configuration by solid state reaction. The ferrite powders were mixed with polyvinylcloride (PVC) plasticizer to fabricate a microwave absorbing composite. X-ray diffraction (XRD), scanning electron microscope (SEM), vibrating sample magnetometer (VSM), and vector network analyzer were employed to characterize phase identification coupled with size and morphology of powder and microwave absorption properties of synthesized composites. It was found that the maximum reflection loss of −40dB was appeared at frequency range of 12–18GHz. In the present work, new cation substitutions in iron sites in the crystal lattice of barium ferrite, which can easily tune the bandwidth of the reflection loss, were used. To the best of our knowledge, this is the first study which displays the wideband absorber by employing single layer hexaferrite backed on the surface of copper. [Copyright &y& Elsevier]