Search Results (131)

With the continuous advancement of electromagnetic protection technologies, the development of lightweight electromagnetic wave-absorbing materials with excellent absorption performance has become a critical challenge in the field. In this study, commercially available hollow glass microspheres (HGMs) were employed as templates, and Ni²⁺/Co²⁺ metal ions were used to catalyze the polymerization of dopamine (PDA), forming HGM@Ni_xCo_y/PDA precursors. Subsequent high-temperature pyrolysis yielded lightweight composite absorbing materials, denoted as HGM@Ni_xCo_y/C. This material integrates dielectric loss, conductive loss, magnetic loss, and resonance absorption mechanisms, exhibiting outstanding electromagnetic wave absorption properties. The absorption performance can be effectively tuned by adjusting the Ni-to-Co ratio, with the optimal performance observed at an atomic ratio of 2:3. At a filler loading of 20 wt.%, HGM@Ni₂Co₃/C achieved an effective absorption bandwidth (EAB) of 6.83 GHz (ranging from 10.53 to 17.36 GHz) and a minimum reflection loss (RL_min) of −27.26 dB. These results demonstrate that the synergistic combination of hollow glass bubbles and carbon-based magnetic components not only significantly reduces the material density and required filler content but also enhances overall absorption performance, highlighting its great potential in the development of lightweight and high-efficiency electromagnetic wave absorbers. Full article

There is great potential for the development of microwave-absorbing materials (MAMs) for structural regulation. Auxetic structures have excellent mechanical properties, which can be applied to multifunctional MAMs in various fields. Here, the microwave absorption performances of the auxetic structures were simulated using the High-Frequency Structure Simulator (HFSS), by regulating the structure, dielectric constant, layer number, and pore size. The simulation results show that increasing the dielectric constant, layer number, or decreasing pore size will lead to a decrease in the frequency of minimum reflection loss (RL_min). The main purpose of this study is to elucidate the influence of structure, dielectric constant, layer number, and pore size on the absorption performance of auxetic structures and obtain practical auxetic MAMs with a performance of RL_min < −30 dB and effective absorption bandwidth (EAB) > 3 GHz. Finally, practical auxetic MAMs between 8 and 18 GHz and MAMs optimized in dielectric constant were obtained, which were proven to have the advantages of lightweight characteristics, high absorption, and wide bandwidth. The four structures exhibit great RL_min values of −51.09, −55.52, −47.09, and −54.98 dB with wide EAB values of 3.25, 3, 4.75, and 4.5 GHz, demonstrating the strong electromagnetic wave absorption performance of auxetic structures. This work provides theoretical guidance for the study of auxetic structures in the field of microwave absorption and provides an effective approach for multi-disciplinary research on MAMs. Full article

Vanadium dioxide (VO₂) is a well-known phase-change material that exhibits a thermally driven insulator-to-metal transition (IMT) near 68 °C, leading to significant changes in its electrical and optical properties. This transition is governed by structural modifications in the VO₂ crystal lattice, enabling dynamic control over absorption, reflection, and transmission. Despite its promising tunability, VO₂-based optical absorbers face challenges such as a narrow IMT temperature window, intrinsic optical losses, and fabrication complexities associated with multilayer designs. In this work, we propose and numerically investigate a single-layer VO₂-based optical absorber for the visible spectrum using full-wave electromagnetic simulations. The proposed absorber achieves nearly 95% absorption at 25 °C (insulating phase), which drops below 5% at 80 °C (metallic phase), demonstrating exceptional optical tunability. This behavior is attributed to VO₂’s high refractive index in the insulating state, which enhances resonant light trapping. Unlike conventional multilayer absorbers, our single-layer VO₂ design eliminates structural complexity, simplifying fabrication and reducing material costs. These findings highlight the potential of VO₂-based crystalline materials for tunable and energy-efficient optical absorption, making them suitable for adaptive optics, smart windows, and optical switching applications. The numerical results presented in this study contribute to the ongoing development of crystal-based phase-transition materials for next-generation reconfigurable photonic and optoelectronic devices. Full article

Long-wave infrared (LWIR) broadband absorption is of great significance in science and technology. The electromagnetic field energy is absorbed by the metamaterials material, leading to the enhanced light absorption, from which the Metal–Dielectric–Metal (MDM) structure is designed. FDTD simulation calculation indicate that the bandwidth within which the absorber absorption ratio greater than 90% is 11.04 μm, and the average absorption rate (9.10~20.14 μm) is 93.6%, which can be accounted for by the impedance matching theory. Upon the matching of the impedance of the metamaterial absorber with the impedance of the incident light, the light reflection is reduced to a minimum, and increase the absorption ratio. Meanwhile, the good incidence angle unsensitivity due to the metasurface structural symmetry and the characteristics of the electromagnetic field distribution at different incidence angles. Due to the form regularity of the nanoring–nanowire metasurface structure, the light acts similar in different polarization directions, and the surface plasmon resonance plays a key role. Using FDTD electromagnetic field analysis to visualize the electric field and magnetic field strength distribution within the absorber, the electromagnetic field at the interface in the nanoring–nanowire metasurface structure, promote the surface plasmon resonance and interaction with damaged materials, and improve the light absorption efficiency. Moreover, the different microstructures and the electrical and optical properties of different top materials affect the light absorption. Meanwhile, adjusting the absorption layer thickness and periodic geometry parameters will also change the absorption spectrum. The absorber has high practical value in thermal electronic devices, infrared imaging, and thermal detection. Full article

This paper proposes a tri-band wide-angle polarization-insensitive absorber operating in the C-band and Ku-band, based on the design concept of metal–dielectric–metal. The absorber achieves absorption efficiencies of 99.05%, 99.3%, and 97.9% at 4.23 GHz, 7.403 GHz, and 14.813 GHz, respectively. The first two absorption frequencies are in the C-band, while the third absorption frequency is in the Ku-band, both of which are commonly used in satellite communication. The designed absorber consists of three differently sized regular hexagonal rings. To analyze the interaction mechanism between the electromagnetic wave and the absorber, we applied the theory of impedance matching and equivalent media to analyze the metamaterial properties of the absorber. In addition, the equivalent circuit model of the absorber has been analyzed. We then determined the existence of coupled electromagnetic resonances between the top and bottom surfaces by analyzing the distribution of the electric field, magnetic field, and surface currents on the absorber. By varying the polarization angle and incident angle of the incoming wave, we found that the absorber exhibits polarization insensitivity and wide-angle absorption characteristics. The TE and TM waves maintain more than 90% absorption efficiency up to incident angles of 50° and 60°, respectively. The absorber’s thickness is 1.07 mm, which is 0.0154 times the wavelength corresponding to the lowest resonant frequency ${(\lambda }_0)$, and the edge length of the subunit’s regular hexagon is 7.5 mm (0.108${\lambda }_0$), making the absorber sub-wavelength in scale while maintaining its compactness. The proposed absorber operates in the C-band and Ku-band, and can be applied in the field of satellite communications, achieving functions such as electromagnetic shielding and stealth. Full article

Absorption of electromagnetic waves in a broadband frequency range with polarization insensitivity and wide incidence angles is greatly needed in modern technological applications. Many methods using metamaterials have been suggested to address this requirement; they can be complex multilayer structures or use external electronic components. In this paper, we present a plasmonic metasurface structure that was simply fabricated using the standard printed circuit board technique but provided a high absorption above 90%, also covering a broadband frequency range from 12.30 to 14.80 GHz. This plasmonic metasurface consisted of structural unit cells composed of multiple split rings connected by a copper bar. Analysis, simulation, and measurement results showed that the metasurface also showed polarization-insensitive properties and maintained an absorption above 90% at incident angles up to 45 degrees. The suggested plasmonic metasurface is a fundamental design that can also be used to design the absorber in different frequency ranges and is able to adapt well to being fabricated at various scales. Full article

Borophene, as a novel two-dimensional (2D) material, has garnered significant interest due to its exceptional optoelectronic properties, including anisotropic plasmonic response high carrier mobility, etc. In this work, we theoretically propose a borophene-based anisotropic metamaterial perfect absorber using the finite-difference time-domain (FDTD) method. The research results show that the proposed metamaterial exhibits triple-band perfect electromagnetic absorption characteristics when the polarization direction of electromagnetic wave is along the zigzag direction of borophene, and the resonant absorption wavelengths can be adjusted by varying the carrier mobility of borophene. Furthermore, as an application of the proposed perfect absorber, we investigate the refractive sensing properties of the borophene-based metamaterial. When the carrier density of borophene is 4.0 × 10¹⁹ m⁻², the maximum refractive index sensitivity of the designed absorber is up to 867 nm/RIU, with a figure of merit of 11.71 RIU⁻¹, which has promising applications in the field of biochemical sensing and special environmental detection. Full article

The integration, miniaturization, and high frequency of microwave vacuum electronics put forward higher requirements for heat-conducting and wave-absorbing integrated materials. However, these materials must balance the dispersion and isolation of wave-absorbing components to optimize absorption while maintaining the continuity of thermal conductivity pathways with low defect rates and minimal interfaces. This presents a significant challenge in achieving both high thermal conductivity and efficient wave absorption simultaneously. Here, AlN/FeNi microwave-attenuating ceramics were synthesized via non–pressure sintering in a nitrogen atmosphere. The influence of FeNi content (0–20 wt%) on the density, phase composition, microstructure, microwave-absorption properties and thermal conductivity of the composites was investigated. AlN/FeNi composites consist primarily of an AlN phase with FeNi_0.0578, Fe, AlYO₃, and Al₅Y₃O₁₂ as secondary phases, and the microstructure is uniform and dense. As the FeNi content rises from 0 to 20 wt%, the density of the composites sintered at 1800 °C × 2 h increases from 3.3 to 3.7 g/cm³. Their X-band (2–18 GHz) dielectric constant goes up from 6.5 to 8.5, the dielectric loss factor rises from 0.1 to 0.9, and thermal conductivity diminishes from 130 to 123 W/m·K. Upon reaching an FeNi content of 20 wt%, the composite achieves a minimum reflection loss of −39.1 dB at 9.5 GHz, with over 90% absorption across an effective absorption bandwidth covering 2.5 GHz. It exhibits excellent impedance matching, electromagnetic wave-attenuation properties, a relative density of 98.6%, and a thermal conductivity of 123 W m⁻¹ K⁻¹. The prepared AlN/FeNi composites, with integrated outstanding microwave-absorption capabilities and thermal conductivity, holds great promise for applications in 5G communications, aerospace, and artificial intelligence. Full article

Recently, electromagnetic wave (EMW)-absorbing materials have obtained increasing attention for both military and civil applications. This study adopted the powder sintering method and the concept of recycled wastes in fabricating functional ceramic foam (CF). Firstly, a ceramic green body composed of pulverized granite residues, waste glass, and a foaming agent was sintered. The influence of the sintering temperature and SiC addition on CF was investigated, and then surface graphitization post-treatment of CF was performed as well. The truly enhanced compressive strength and EMW-absorbing property of surface graphitization ceramic foam (SG-CF) with a homogeneous porous structure was realized in the present work, which is promising as a candidate in EMW absorption systems. Full article

The development of functional building materials that can absorb electromagnetic radiation is important for preventing and controlling electromagnetic pollution in urban areas. In this study, cement-based electromagnetic wave (EMW)-absorbing materials were created using graphite tailings (GTs) as a conductive admixture and steel fiber (SF) as an EMW absorber, which resulted in materials with a wide effective bandwidth and high reflection loss (RL). In particular, a GT–cement matrix with excellent mechanical and electrical properties was obtained. This study explored the influence mechanism of the SF content on the mechanical, electrical, and EMW-absorption properties of cement-based materials under the synergistic effect of GTs and SF. Findings demonstrate that the combination of GTs and SF notably improved the electrical and EMW-absorption characteristics of the cement-based materials. Optimal EMW-absorption properties were observed for a combination of 30% GTs and 6% SF. A developed cement-based EMW-absorbing material with a thickness of 20 mm displayed a minimum RL of −25.78 dB in the frequency range of 0.1–5 GHz, with an effective bandwidth of 0.953 GHz. Thus, the cement-based composite materials developed in this study have excellent EMW-absorption performance, which provides an effective strategy for preventing and controlling electromagnetic pollution in urban spaces. Full article

Currently, oxidation of SiC_f/SiC composites in harsh environments such as high temperatures has become a key challenge for their application in high-temperature structural wave-absorbing materials. In this study, borosilicate glass (BSZ) coatings were prepared using the thermal nitrogen–oxygen process. The evolution of mechanical and coating microwave dielectric properties of the composites with and without BSZ coatings after oxidation at 1100 °C, 1200 °C, 1300 °C and 1400 °C was investigated. The results showed that the mechanical strength of the BSZ-coated SiC_f/SiC specimens remains virtually unchanged, with a remarkable strength retention rate of 94%. The exceptional oxidation resistance of these coatings can be attributed to the formation of self-healing oxides and the reinforcing “pinning” effect of ZrSiO₄. With an increase in oxidation temperature, the dielectric properties of the oxidized coatings are determined by the intrinsic properties of the generators and the porosity. Overall, these features highlight the potential of borosilicate coatings in the field of electromagnetic wave-absorbing composites, and the current work establishes a correlation between the oxidized microscopic properties of the coatings and the dielectric properties. Full article

With the increasing demand for effective electromagnetic wave (EMW) absorbers due to the proliferation of electronic devices and 5G communication systems, traditional wave-absorbing materials can no longer meet the current requirements. Thus, this research introduces a three-dimensional (3D) composite material consisting of PMMA@Mxene@Co₃O₄ microspheres, prepared through in situ self-assembly and hydrothermal growth. The strong electrical conductivity of Mxene, combined with the magnetic loss of Co₃O₄, ensures enhanced dielectric–magnetic synergy, leading to excellent EMW absorption. The study investigates the influence of varying Co₃O₄ content on the electromagnetic properties of the composite. Experimental results show that the optimal sample, with a thickness of 2.5 mm, achieves a minimum reflection loss (RL_min) of −52.88 dB at 6.88 GHz and an effective absorption bandwidth (EAB) of 5.28 GHz. This work highlights the potential of 3D PMMA@Mxene@Co₃O₄ composites as high-performance microwave absorbers, providing a promising solution to EMW pollution. The findings offer valuable insights into material design strategies, demonstrate a promising pathway for developing lightweight, high-performance EMW absorbing materials by optimizing impedance matching and utilizing advanced microstructure design techniques. Full article

With the increasing adoption of composite materials in aircraft construction, traditional anti-icing technologies face significant challenges due to the low thermal conductivity and heat resistance of composite resins. These limitations have spurred the development of lightweight, efficient, durable, and cost-effective integrated anti-icing technologies as a critical area of research. This paper begins with an overview of advancements in electrothermal anti-icing and de-icing technologies for aircraft. It then explores the configurations and applications of functional-structural integration technology for anti-icing and de-icing, emphasizing pivotal technologies and current challenges in this field. Finally, the study forecasts the development trends in the multifunctional integration of thermal conductivity/insulation, anti-icing, and electromagnetic wave transparency/wave-absorbing properties. These advancements are driven by the evolution of composite materialization in aircraft and the progression of multi-electrical/all-electrical technologies. The objective is to provide a comprehensive guide for technological development in anti-icing, aiding researchers and relevant departments to further enhance the application of anti-icing technology in composite material aircraft. Full article

In this paper, a kind of metastructure–photonic crystal (MPC) with multi-frequency asymmetric absorption–transmission properties is proposed. It is composed of various dielectric layers arranged in a periodically tilting pattern. When electromagnetic waves (EMWs) enter from the opposite direction, MPC shows an obvious asymmetry. EMWs are absorbed at 13.71 GHz, 14.37 GHz, and 17.10 GHz in forward incidence, with maximum absorptions of 0.919, 0.917, and 0.956, respectively. In the case of backward incidence, transmission above 0.877 is achieved. Additionally, the MPC is utilized for refractive index (RI) sensing, allowing for wide RI range detection. The refractive index unit is denoted as RIU. The RI detection range is 1.4~3.0, with the corresponding absorption peak variation range being 17.054~17.194 GHz, and a sensitivity of 86 MHz/RIU. By adjusting the number of MPC cycles and tilt angle, the sensing performance and operating frequency band can be tailored to meet various operational requirements. This MPC-based RI sensor is simple to fabricate and has the potential to be used in the development of high-performance and compact sensing devices. Full article

Electronic equipment brings great convenience to daily life but also causes a lot of electromagnetic radiation pollution. Therefore, there is an urgent demand for electromagnetic wave-absorbing materials with a low thickness, wide bandwidth, and strong absorption. This work obtained a high-performance electromagnetic wave absorption system by adding conductive carbon spheres (CSs) to the CH₃NH₃PbI₃ (MAPbI₃) absorber. In this system, MAPbI₃, with strong dipole and relaxation polarization, acts dominant to the wave absorber. The carbon spheres provide a free electron transport channel between MAPbI₃ lattices and constructs interfacial polarization loss in MAPbI₃/CS. By regulating the content of CSs, we speculate that this increased effective absorption bandwidth and reflection loss intensity are attributed to the conductive channel of the carbon sphere and the interfacial polarization. As a result, when the mass ratio of the carbon sphere is 7.7%, the reflection loss intensity of MAPbI₃/CS reaches −54 dB at 12 GHz, the corresponding effective absorption bandwidth is 4 GHz (10.24–14.24 GHz), and the absorber thickness is 2.96 mm. This work proves that enhancing conduction loss and interfacial polarization loss is an effective strategy for regulating the properties of dielectric loss-type absorbing materials. It also indicates that organic-inorganic hybrid perovskites have great potential in the field of electromagnetic wave absorption. Full article