Electromagnetic Properties Research Articles

Effect of surface treatment of nickel-coated graphite on conductive rubber

Abstract In the blended conductive rubbers, good dispersion of conductive fillers and great interfacial bonding with the substrate are the keys to achieving excellent mechanical and electromagnetic shielding properties. It is found that compared with octyltriethoxysilane (A137), 3-methacryloxypropyl-trimethoxysilane (A174) and vinyltriethoxysilane (A151) with a double bond reduce the curing degree of the blends. The vinyl methyl silicone rubber/nickel-coated graphite (VMQ/NCG) composites modified by A137 shows poor tensile properties, while the composites modified by A174 shows inferior electrical properties. The presence of physical adsorption and chemical adsorption on the surface of NCG modified by A151, which effectively enhances the dispersibility of NCG and interfacial bonding strength with rubber, so that the material exhibits excellent comprehensive properties. When the content of A151 is 3% and modified by dry method, the tensile strength of VMQ/NCG composites can reach 1.6 MPa, the elongation at break can reach 162%, and the volume resistivity can reach 0.05 Ω·cm.

Polymetallic red mud direct materialization strategy towards zero waste emission: Electromagnetic wave absorption conversion and sodium solidification

Red mud is an industrial hazardous alkaline solid waste, whereas it is rich in polymetallic components showing a high comprehensive utilization value. Direct materialization of red mud towards zero waste emission is a more reasonable and environmentally friendly strategy. In this work, a novel materialization approach of red mud via converting the polymetallic constituents into functional ferrite material by phase reconstruction with MnO2 was proposed. The mineral phase reconstruction, microstructure evolution, reaction interface observation, electromagnetic property, and the materialization conversion mechanism were investigated. It was found that the complicated phases in red mud were transferred to simple forms including the magnetic ferrites (Ca/Na/Al/Ti-bearing Mn ferrite) and weakly magnetic silicates ((Na,Al,Ca)2SiO3) after phase reconstruction. The reconstructed red mud after sintering at 1200 ℃ for 120min in air atmosphere had satisfactory electromagnetic property. Magnetism study demonstrated the soft magnetic property with maximum saturation magnetization of 34.22emu/g and coercivity of only 7.0Oe. Compared with the original red mud, effective electromagnetic wave absorption with reflection loss (RL) values of the reconstructed red mud below -20 dB were satisfied across a wider frequency bandwidth of 5-18GHz, and the minimum RL value was lower as -32.4dB with a thinner veneer thickness of 15mm, highlighting its excellent electromagnetic wave absorption performance. Moreover, Na solidification behaviors indicated that Na was solidified in the sintered product, which can reduce the possible environmental hazards of red mud alkalinity. The novel materialization treatment with zero waste emission exhibits a favorable application prospect with a large red mud batching ratio about 50wt%.

Cobalt Ferrite@Barium titanate core-shell nanoparticles empowered triboelectric electromagnetic coupled nanogenerator for self-powered electronics

In pursuing sustainable energy solutions for wearable technology and Internet of Things (IoT) devices, achieving high power in self-powered electronics is a significant challenge. This study introduces a novel hybrid nanogenerator by integrating a triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG) to achieve both high voltage and high current outputs simultaneously. The cobalt ferrite barium titanate (CoFe2O4@ BaTiO3) core–shell nanoparticles (NPs) were chosen for their unique ability to enhance the system’s performance by combining triboelectric, piezoelectric, and electromagnetic properties. The BaTiO3 shell exhibited robust triboelectric and piezoelectric properties essential for TENG operation, while the CoFe2O4 core, influenced by the EMG’s magnetic field, induces additional static charges, significantly boosting overall energy conversion efficiency. The TENG and EMG in the combined system operate together in a contact-separation mode, where their in-phase output signals are seamlessly combined via a double bridge rectifier, resulting in a robust power output of 37.7 mW and a power density of 1.86 mW/cm2, with cycling stability of over 10,000 cycles. The uniquely designed TENG-EMG combined nanogenerator (C-TENG) exhibited striking adaptability, effectively operating across different low-to-high frequencies and load situations while constantly powering portable electronic devices. This innovative approach meets the high energy demands of modern self-powered electronics with exceptional efficiency, durability, and high-power density, positioning it as a versatile solution for wearable biomechanical energy harvesting.

Metal-nitrilotriacetic acid chelate derived strategy to selectively produce porous Ni/C, CoNi/C and Co/C magnetic heterostructured nanorods for lightweight and strong microwave absorption

Because of tempting magnetic-dielectric synergies and interfacial effects, designing a simple and low-cost route for producing multidimensional carbon-based magnetic nanocomposites is very important for the development of microwave absorbers (MAs). In this paper, a facile and propagable Ni-nitrilotriacetic acid chelate (NAC) derived strategy was proposed to selectively fabricate zero-dimensional (0D)/one-dimensional (1D) porous Ni/C magnetic heterostructured nanorods (MHNRs) consisting of 1D carbon nanorod, lots of pores and 0D Ni nanoparticles via a combined hydrothermal and thermally treated methods. The porous Ni/C MHNRs displayed the progressively improved Ni and C crystallinity by controlling the temperature, which resulted in the tunable electromagnetic and microwave absorption properties (MAPs). Additionally, 0D/1D porous CoNi/C and Co/C MHNRs could be selectively produced through this strategy by adopting CoNi-NAC and Co-NAC as precursors. Benefiting from desirable interface and magnetic/dielectric synergies, the acquired 0D/1D porous Ni/C, CoNi/C and Co/C MHNRs presented excellent MAPs and certain corrosion resistance properties. In especial, Co/C MHNRs displayed a strong absorption capacity (−47.89 dB), an ultrawide effective absorption bandwidth (8.40 GHz) and small matching thicknesses (∼2 mm), which were a desirable candidate for MAs. Consequently, a facile, low-cost and propagable metal-NAC derived strategy was proposed to synthesize 0D/1D porous carbon-based MHNRs, which presented an alternative technique to develop lightweight efficient MAs.

Anion Doping as a “Trigger” to Modulate Defect‐Tailored Dielectric Coupling for Ultrathin Microwave Absorber

AbstractAnion doping engineering is recognized as a prospective strategy to adjust the electronic configuration and transport capacity of carbon‐based magnetoelectric hybrids and to optimize defects for the modulation of electromagnetic (EM) properties. This study effectively accomplishes an overwhelming enhancement in the dielectric coupling between conduction and polarization for the CuCo bimetallic/carbon system by employing in situ (N, O)/ex situ (S, Se) doping and defect modulation strategies. The well‐designed lattice distortions are facilitated by the large atomic radii (Se) intercalated carbon skeleton and the bimetallic CuCo, which activate the reinforcement of the dipole polarization in the high‐frequency region. Interestingly, an appropriate number of vacancies acts as “electron traps” to accelerate the local charge redistribution, endowing the system with extremely strong electronic interactions and interface‐induced polarization. It is remarkable that the ultra‐thin feature (1.8 mm) is able to achieve an extraordinary microwave attenuation (‒56.1 dB). Additionally, specific defect upgrading of anionic Se doping beneficially hinders the development of phonon transmission, conferring Cu2Se/CoSe2/NC‐Se aerogel outstanding infrared stealth capabilities along with inheriting the advantages of traditional carbon‐based hybrids (lightness, compressive/structural stability, and hydrophobicity/anti‐corrosive properties). This research offers distinctive perspectives on the advanced design of multifunctional absorbers in complex environments.

High-performance electromagnetic absorbing Ni/C composites derived from Ni-MOF materials: Effects of organic ligands and pyrolysis temperatures

Magnetic carbon-based materials derived from nickel organic framework (Ni-MOF) are considered to be a kind of electromagnetic wave (EMW) absorbing materials with great potential and application value. However, the precise design of Ni-MOF-derived magnetic carbon-based materials remains a huge challenge. In the present work, through the modulation of organic ligand and pyrolysis temperature, Ni/C composites with excellent electromagnetic absorption properties are obtained due to their improved multiple loss and optimized impedance matching. Specifically, the organic ligand and pyrolysis temperature affect the degree of graphitization of the carbon frame and the specific surface area of the Ni/C composites, thus changing the conductivity, magnetic properties and electromagnetic parameters. In particular, the sample Ni/C-2-500 using H2BPDC as the organic ligand and calcined at 500 °C gives an RLmin of –50.37 dB and an EAB of 6.0 GHz at a packing rate of 30 wt% and a thickness of 2.5 mm, which covers the entire Ku band. In addition, Ni/C-2-500 exhibits good thermal conductivity. Therefore, this study provides an idea for exploring MOF materials and their derivatives with tunable EMW absorbing properties and heat conduction advantages prepared by different organic ligands.

Non-contact measurement method of liquid composition using microwave radar cross-section

This study aims to provide a non-contact detection of liquid composition inside containers using Microwave Radar Cross-section (RCS) measurement technology. Firstly, it analyzes the limitations of traditional near-infrared spectroscopy methods and proposes the necessity of introducing microwave detection methods. The research demonstrates through experiments a significant correlation between polar substances like total acid content and radar scattering capability, showing microwave radar’s effectiveness in reflecting the polarity characteristics of liquids. Furthermore, theoretical derivations and experimental validations illustrate that differences in electromagnetic properties of different liquid components lead to variations in echo loss, thereby impacting RCS levels. Experimental results indicate that microwave radar RCS measurement technology achieves an accuracy level of 2%, capable of distinguishing between different concentrations of ethanol, acetic acid, and other solutions. This study highlights the significant advantages of microwave radar RCS measurement technology in non-contact detection of liquid composition, providing new methods and a technological foundation for precise liquid component detection.

The preparation and modulation of 1D porous nanofibers loaded with Co@NC for efficient microwave absorption through electrospinning

1D nanofibers have been extensively applied in field of microwave absorption (MA) by virtue of large specific surface area, low percolation thresholds, and high aspect ratios. Through the modification of its physical properties and components, enhancement of MA capability is expected to be achieved. Herein, we modified the nanofibers by porous structure construction and dielectric/magnetic coupling, and further altered the chemical composition and microstructure of the absorbers through adjustment of annealing temperature and porogen addition, thus leading to effective modulation of electromagnetic properties. Specifically, we first prepared a polyacrylonitrile-based nanofiber by electrospinning. Subsequently, in situ growth of ZIF-67 and the construction of pore structure of the nanofibers were achieved simultaneously in aqueous solution. Ultimately, 1D (ZIF-67 derivatives)@(porous carbon nanofiber) were acquired by thermal field modulation. It suggests that, with the increase of annealing temperature, graphitization degree rises, enhancing conductive loss. Meanwhile, more divalent cobalt is reduced, leading to a rise in polarization loss and the effective modulation of magnetic properties. Besides, the rise in porogen addition is accompanied by a decrease in pore volume and an increase in pore size, enhancing electrical conductivity while increasing the number of defects, thus enhancing dielectric loss. Notably, when annealing temperature is 700 °C and porogen addition is 29 wt%, obtained material exhibits excellent reflection loss (−52.49 dB at 1.53 mm) and broad bandwidth (5.29 GHz at 1.62 mm). This approach offers a novel perspective for the preparation and modulation of electromagnetic properties of 1D nanofibers.

Enhancing microstructural properties of copper-based composite castings through microwave-assisted reinforcement with MWCNT

An emerging advancement in the field of metallic materials casting is the in-situ microwave casting of metallic materials. To achieve this, the microwave heating process is applied within the applicator cavity, working on the principles of hybrid microwave heating (MHH). This process involves melting the charge, pouring it into an in-situ container, and subsequently solidifying the melted charge. The electromagnetic and thermal properties of the charge influence the interactions between the microwave energy and the material, as well as the melting behavior induced by the microwaves. As for the solidification process, this is also controlled by a cooling condition within the applicator. The present study aims to outline an in-situ casting process for copper-based composite castings fabricated within a multimode cavity, utilizing 900 W at 2.45 GHz. The quality of the developed in-situ cast was assessed by analyzing its characteristics. A microstructural examination revealed that the composite castings exhibited a homogeneous and dense structure. Scanning electron microscopy (SEM) and Energy-dispersive spectroscopy (EDS) analysis was conducted across the casting. The XRD pattern confirmed the presence of major peaks of copper in the composite castings, along with the presence of oxide phases such as Cu64O. Also, the micro indentation hardness of the Cu + 1.5%MWCNT casts was found to be 1.23 times higher than that of microwave-processed pure copper.

Review of: "The electromagnetic nature of nanoparticles in magnetic materials, the molecules and atoms that make them have electromagnetic properties"

Review of: "The electromagnetic nature of nanoparticles in magnetic materials, the molecules and atoms that make them have electromagnetic properties"

Spheres of maximum electromagnetic chirality

The search for objects that yield maximum electromagnetic chirality in their emitted wave field has gathered significant attention in recent years. However, achieving such maximum chirality is challenging, as it typically requires complex chiral metamaterials. Here, we demonstrate that chiral spheres can yield maximum chirality in their emitted wave field. Specifically, we analytically find the spectral trajectories at which chiral spheres become optically transparent to a given helicity of the incident field, while for its opposite helicity, they behave as dual objects, i.e., on scattering, they preserve helicity. Since chiral spheres behave as dual objects at the first Kerker condition of zero backscattering, we significantly simplify this condition in terms of a Riccati-Bessel function. Our analytical findings suggest the creation of spherical building blocks for designing metasurfaces or metamaterials with maximum electromagnetic chirality properties. Published by the American Physical Society 2024

High-order direct modulation terahertz communications with a wideband time-coding metachip modulator.

Terahertz communication technology based on on-off keying (OOK) direct modulation is vital for sixth-generation communication systems, especially in short-distance and high-rate applications. However, low-order OOK modulation often leads to suboptimal anti-interference capabilities and a heightened demodulation threshold. Here, we propose a high-order direct modulation terahertz communication framework using a wideband time-coding metachip modulator. The modulator leverages the electromagnetic resonance properties within the metaunit structure, with control enabled by gallium arsenide Schottky diodes. By manipulating the timing of voltage pulses applied to these diodes, the equivalent electromagnetic resonance distributions can be precisely regulated in the time domain. This enables independent and accurate control over the amplitude and phase of terahertz harmonics. Leveraging this technique, three high-order modulation schemes-quadrature phase-shift keying, 16-phase-shift keying, and 16-quadrature amplitude modulation- are achieved in a direct modulation and direct detection system, demonstrating the real-time image transmission. The proposed method offers an important way to develop integrated and low-complexity terahertz wireless communication systems.

Characterization of Properties of 325-MHz Half-Wave Superconducting Resonators at Low Microwave Field Amplitudes

A prototype of the 325-MHz niobium half-wave coaxial resonator (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta = 0.21$$\\end{document}) is developed, built, and tested at low microwave field amplitudes. Electromagnetic properties of the prototype in the superconducting state are investigated in the continuous wave regime and the damping regime using a highly stable radio-frequency (RF) generator and power detectors. The experimental data on the resonator’s response in the superconducting state are used to calculate its most important characteristics—the intrinsic Q value and the accelerating field. The experimentally measured Q value of the prototype is \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{Q}_{0}} = (3.5 \\pm 0.1) \ imes {{10}^{8}}$$\\end{document} at input powers of up to +20 dBm.

CHARACTERIZATION SUBSOLIDUS SYSTEM STRUCTURE CaO - Al2O3 - CoO – NiO

The paper presents the results of calculations characterizing the elements of the subsolidus structure of the CaO– Al2O3 – CoO – NiO system, which is promising for the production of modified aluminous cements and heterophase materials with a complex of unique properties. Insufficient information about the structure of the four-component phase diagram of a certain multicomponent system makes it difficult to obtain such materials. To predict the phase composition of materials, theoretical studies of the structure of the system were carried out. An analysis of the features of the coexistence of heterophase combinations was carried out, taking into account geometric-topological and statistical characteristics. The technological risks of predicting the phase composition of materials that arise in certain concentration regions of the system under study are shown. Calculations were carried out over the entire temperature range, both up to the melting point of the ternary oxide compound Ca3CoAl4O10 at 1439 K, and in a higher temperature region. Using known methods, the characteristics of eutectics in some sections of the system under study, which is of interest for the technological design of materials, were calculated. The results of calculations of the characteristics of eutectics show that among the analyzed tetrahedra, the minimum eutectic temperature (1367 K) is observed between the oxides of cobalt, nickel, calcium-cobalt aluminate and calcium monoaluminate, which can be realized for the synthesis of heterophase materials with a high content of Ca3CoAl4O10. Such materials have practical application in various industries: lime production; lime binders; corundum abrasives and refractories; high temperature catalysts; ceramics with special electromagnetic properties.

CPT-Odd effects on the electromagnetic properties of charged leptons in the Standard Model Extension

Abstract The impact of the CPT-Odd electroweak gauge sector of the Standard Model Extension on the magnetic dipole moment of charged leptons is studied. This gauge sector is characterized by the (k1)µ and (k2)µ Lorentz coefficients, which have positive mass dimension because they are associated with a UY (1)-invariant and with an SUL(2)-invariant dimension-three operators, respectively. They belong to the category of relevant interactions, which have strong effects on low-energy observables. We present a comprehensive study on the impact of this sector on the magnetic dipole moment of charged leptons, up to second order in these Lorentz coefficients, both at the tree and one-loop levels. We find that the first-order contributions in the Lorentz coefficients at the tree and one-loop levels depend on energy, while second-order ones at the tree-level do not. As for second-order one-loop effects, there are both energy-dependent and energy-independent contributions, but we have focused only on those of the latter type. We find that the tree-level contributions are suppressed with respect to the one-loop ones by at least a factor of (m2l /m2Z). We find that the contribution to the dipole associated with the electron is by far the dominant one, as it can be up to fourteen orders of magnitude greater than that of the muon and up to sixteen orders greater than that of the tau. The Lorentz coefficient (kAF )µ of the Carroll-Field-Jackiw’s QED is given by a linear combination of the (k1)µ and (k2)µ vectors. Assuming thatcollinear, we obtain an upper bound of|k12|,|k22| ≫ |k2AF| and taking (kAF)µ = 0, which implies that (|||−(3.49 × 10-4)(k2)0me + k2 | k1)µ and (k2)µ are.

Ultrathin Ti3C2Tx MXene/Cellulose nanofiber composite film for enhanced mechanics & EMI shielding via freeze-thaw intercalation

Developing high-performance and cost-effective microwave-absorbing materials for large-scale production is crucial in addressing the current electromagnetic pollution problem. This has become a focus of scientific research. This study proposes a cost-effective freeze-thaw method to enable large-scale production of MXene-based flexible films. This method streamlines the preparation process and produces ultrathin flexible MXene/CNF composite films with a multidimensional layered structure. The multidimensional layered structure provides additional scattering and reflecting paths for electromagnetic waves, increasing the interaction time between electromagnetic waves and the material. Additionally, the redistributed interfacial charge enhances the dielectric loss and electromagnetic shielding performance for the shielding material, thereby improving microwave absorption efficiency. Owing to these advantages, the MXene/CNF composite films prepared using the freeze-thaw method exhibit excellent electromagnetic shielding and mechanical properties. The conductivity of the composite film can reach 165.9 S cm−1 with a shielding effectiveness of 54.7 dB, and a high efficiency of 99.74 %. According to the simulations using a finite element method (FEM), the arrangement and rotation angles of all CNF layers significantly affect the electromagnetic shielding effectiveness of the MXenen/CNF composite films.

Superradiance scattering of electromagnetic and gravitational fields and thin accretion disk around non-commutating Kerr black hole

We consider the non-commutative (NC) Kerr black hole where the mass of the central object is smeared over a region of linear size b\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{b}$$\\end{document}, b is the strength of the NC character of spacetime. For the spacetime under consideration, we calculate the amplification factor for electromagnetic and gravitational fields and study various properties of a thin accretion disk. The expression for the amplification factor is obtained with the help of the asymptotic matching technique. The amplification factor is then plotted against frequency for various values of the spin a and the NC parameter b. Though the amplification factor increases with a but decreases with b, the cut-off frequency up to which we have amplification increases with a and b. We then study the effect of the spin and the NC nature of spacetime on the energy flux, temperature distribution, emission spectrum, energy conversion efficiency, and the radius of the innermost stable circular orbit of a thin accretion disk around the black hole with the help of the steady-state Novikov–Thorne model. Our study reveals that these quantities increase with the spin and the NC parameter. We also find that the disk around the NC Kerr black is hotter and more luminous than that around the Kerr black hole and the NC Schwarzschild black hole. We can conclusively infer from our investigation that the NC nature of spacetime has a significant impact on the superradiance phenomenon as well as on various properties of thin accretion disks.

Hierarchically porous N-doped dual-carbon coupled Co5.47N composite with tunable electromagnetic shielding and absorption properties

Electromagnetic interference (EMI) and pollution issues are becoming increasingly prominent. It is of great scientific significance and practical value to develop lightweight, efficient and tunable electromagnetic wave (EMW) attenuating materials. Herein, a three-dimensional (3D) hierarchical porous N-doped dual-carbon (glucose-derived carbon and reduced graphene oxide (rGO)) coupled Co5.47N (Co5.47N@HNCF) composite was reasonably designed and prepared via simple and low-cost methods, which exhibited excellent electromagnetic attenuation properties. By appropriately adjusting the filling amount of Co5.47N@HNCF, tunable EMI shielding and EMW absorption properties could be achieved. At high filling amount (40 wt%), the highly conductive Co5.47N@HNCF composite had excellent EMI shielding effectiveness (EMI SE) in X-band (8.2–12.4 GHz), with a maximum total electromagnetic shielding effectiveness (SET) of 81.6 dB (average EMI SE of 76.8 dB) and a thickness of 2 mm. Particularly, when the thickness is only 0.8 mm, the SET could reach 32 dB. While at low filling amount (15 wt%), Co5.47N@HNCF composite with suitable impedance matching showed remarkable EMW absorption performance, exhibiting high values of reflection loss (RL) of −45.86 dB in 2–18 GHz. The high-performance EMW attenuation in Co5.47N@HNCF could be ascribed to the construction of stable 3D conductive dual-carbon frameworks and Co5.47N nanoparticles with abundant N vacancies. The dielectric and magnetic components of the system acted synergistically, possessing abundant heterogeneous interfaces and defects, which could induce various loss modes such as multiple reflections/scattering, conductive loss, magnetic loss and polarization loss to synergistically dissipate EMW. Therefore, this study endeavors to give an effective strategy for the preparation of low-cost, lightweight, and highly efficient tunable EMW attenuation materials.

Non-uniform electron density estimation based on electromagnetic wave attenuation in plasma

Abstract The surface of a high-speed vehicle reentering the atmosphere is surrounded by plasma sheath. Due to the influence of the inhomogeneous flow field around the vehicle, understanding the electromagnetic properties of the plasma sheath can be challenging. Obtaining the electron density of the plasma sheath is crucial for understanding and achieving plasma stealth of vehicles. In this work, the relationship between electromagnetic wave attenuation and electron density is deduced theoretically. The attenuation distribution along the propagation path is found to be proportional to the integral of the plasma electron density. This result is used to predict the electron density profile. Furthermore, the average electron density is obtained using a back-propagation neural network algorithm. Finally, the spatial distribution of the electron density can be determined from the average electron density and the normalized derivative of attenuation with respect to the propagation depth. Compared to traditional probe measurement methods, the proposed approach not only improves efficiency but also preserves the integrity of the plasma environment.

Enhanced Electromagnetic Wave Absorption in W-Type Ba-Hexaferrites: Role of Composition and Grain Growth

W-type Ba-hexaferrite, BaZn2−xCoxFe16O27, was synthesized via both conventional solid-state (x = 0.4, 0.5, 0.6, 0.75, 1.0, 1.25, 1.5) and molten-salt methods (x = 0.75, 1.0, 1.25). The structure, electromagnetic (EM) properties, and EM wave absorption characteristics were examined across a frequency range of 0.1–18 GHz, focusing on the influence of varying x. As x increased from 0.4 to 0.75, the magnetic anisotropy field (Hani) decreased, reaching its minimum at x = 0.75, before rising again as x continued to increase up to 1.5. Hani was found to be proportional to the ferromagnetic resonance (FMR) frequency, allowing for the tuning of the EM wave absorption frequency range. W-type hexaferrite–epoxy composites (10 wt%) with x values between 0.6 and 1.5 exhibited outstanding wideband EM wave absorption, with a maximum absorption (RLmin < −50 dB) and a wide absorption bandwidth where RL < −10 dB extended beyond 10 GHz (Δfwb > 10 GHz). The x = 1.25 sample with a thickness of 2.37 mm achieved RLmin = −69 dB at 7.8 GHz, while the x = 1.0 sample with a thickness of 2.33 mm delivered Δfwb = 12.5 GHz (5.1–17.6 GHz). Samples synthesized via the molten-salt method showed larger plate-like grain growth compared to those produced by the solid-state method, with permeability spectra shifting to lower frequencies, consequently lowering the EM wave absorption band.