Electromagnetic Waves Research Articles

Hot-pressing-oriented graphene in Si3N4 composites for enhanced electromagnetic wave absorption in X and Ku bands

In this study, the oriented graphene within graphene/Si3N4 composites was successfully achieved by two-step hot-press sintering. Microstructure analysis revealed that the graphene sheets were well dispersed in the Si3N4 matrix and oriented perpendicular to the applied stress. The composites exhibited effective electromagnetic wave (EMW) absorption capabilities and good mechanical properties. The effective absorption bandwidth (EAB) was 9.63 GHz, nearly covering the entire X and Ku bands (8.2–18 GHz), and the minimum reflect loss (RL) was −24.23 dB when the graphene content reached 7 wt% at a thickness of 2.02 mm. Meanwhile, the oriented graphene/Si3N4 composites demonstrated a bending strength of 576.66 MPa and a fracture toughness of 8.40 MPa·m1/2. The EMW absorption in these composites should be primarily due to polarization relaxation loss and conductivity loss, and the toughening mechanism should involve the graphene pull-out, crack bridging, and crack deflection. The graphene/Si3N4 composites have a promising application in structurally integrated functional materials.

Driving voltage frequency and electrode material effects on electromagnetic radiation of the surface dielectric barrier discharge in the air

The electrical discharges are, among others, accompanied by the emission of electromagnetic waves of various frequencies. We studied this emission for the surface dielectric barrier discharge in the air. We used the discharge with one strip-driven electrode and a sinusoidal driving voltage of frequencies 5 and 10 kHz. From the spectra of emitted waves in the frequency band up to 3 GHz, we found that this type of discharge emits the radiation of frequencies below 500 MHz. In this frequency band, we focused on the effect of the driving voltage frequency and driven electrode material on the spectra of these waves. It was found that emitted radiation is distributed in several packages of frequencies, and an increase in the driving voltage frequency or voltage increases the power level of emitted radiation. Compared with the radiation spectrum of the discharge with an aluminium-driven electrode in the spectrum of the discharge with the copper-driven electrode, new peaks of various power levels and the shift of certain radiation frequencies to lower values appear. To understand the underlying mechanism of the discharge electromagnetic waves emission, we focused on the correlation between the electric component of emitted EMWs and the discharge electrical parameters as a function of time and discharge voltage.Graphical abstract

Broadband microwave absorption and antibiosis effect of Cu@C@Fe3O4 nanocomposites

Metal Cu nanoparticles have been recognized as the long-standing presence in the fields of antibacterial and low-induced bacterial resistance, however, the uncontrollable Cu ion concentration from Cu nanoparticle leads to the unstable release of copper ions, limiting their controllable antibacterial application. Based on stable release of copper ions from Cu@C nanocapsules, herein, we report a novel A/B/C structure Cu@C@Fe3O4 nanocomposite to present integrated functionalities of highly controllable antibiosis and electromagnetic wave (EMW) absorption to realize a bifunctional EMW absorption system. With stable concentration, the Cu@C@Fe3O4 nanocomposite can slowly release Cu ions to experience an efficient reactive oxygen species process to realize extreme stable antibiosis behavior and long-term antibacterial effect that is 100% bactericidal effect. With the sustained antibacterial conditions, the Cu@C@Fe3O4 with magnetic component simultaneously exhibits a good impedance matching to lead a broad microwave absorption with a bandwidth of 5.87GHz. Considering above two functions, the multifunctional Cu@C@Fe3O4 provides a pathway for multifunctional EMW absorption materials exploration in antibacterial and microwave absorption applications. This strategy also indicates the possibility to functionalize magnetic nanocapsules towards even broader applications.

In situ loading of ZnO on hierarchical porous carbon derived from banana-peel waste to enrich mechanism for microwave absorption

Biomass has received widespread attention due to its easy availability, low cost, and environmental friendliness as an electromagnetic wave absorber candidate. Inspired by the natural porosity of biomass, the three-dimensional (3D) porous carbon materials derived from banana peels were prepared via coordination and pyrolysis carbonization. A conductive network of biomass-zinc complexes was constructed by introducing Zn2+ to coordinate with organic polymers. Hierarchical porous carbon/ZnO composites with a 3D skeleton network were obtained, which demonstrated outstanding electromagnetic wave absorption performance with an effective absorption bandwidth (EAB) of 6.72GHz and the reflection loss (RL) of -44.18dB. The banana peel-derived porous carbon (BPC) embedded with ZnO particles brings about conductive loss and interface polarization, further enriching the microwave loss mechanisms. This work offers a fresh idea for creating a green, sustainable, and high-value functional carbon-based composite material.

Broadband microwave absorption and antibiosis effect of Cu@C@Fe3O4 nanocomposites

Metal Cu nanoparticles have been recognized as the long-standing presence in the fields of antibacterial and low-induced bacterial resistance, however, the uncontrollable Cu ion concentration from Cu nanoparticle leads to the unstable release of copper ions, limiting their controllable antibacterial application. Based on stable release of copper ions from Cu@C nanocapsules, herein, we report a novel A/B/C structure Cu@C@Fe3O4 nanocomposite to present integrated functionalities of highly controllable antibiosis and electromagnetic wave (EMW) absorption to realize a bifunctional EMW absorption system. With stable concentration, the Cu@C@Fe3O4 nanocomposite can slowly release Cu ions to experience an efficient reactive oxygen species process to realize extreme stable antibiosis behavior and long-term antibacterial effect that is 100% bactericidal effect. With the sustained antibacterial conditions, the Cu@C@Fe3O4 with magnetic component simultaneously exhibits a good impedance matching to lead a broad microwave absorption with a bandwidth of 5.87GHz. Considering above two functions, the multifunctional Cu@C@Fe3O4 provides a pathway for multifunctional EMW absorption materials exploration in antibacterial and microwave absorption applications. This strategy also indicates the possibility to functionalize magnetic nanocapsules towards even broader applications.

Detecting Geothermal Phenomena at Sikidang Crater Area Based on Ground Penetrating Radar Method

Abstract Sikidang Crater (2000 masl) is one of the leading tourist sites in the Dieng area. However, not many people realise that Sikidang Crater is located in the Dieng Volcanic Complex where most of the volcanoes belong to the type A category. Sikidang Crater is one of the main geothermal manifestations occupied by mud pools, solfatara, fumaroles, and altered rocks. These manifestations have potential geological hazards such as toxic gases, base surge, and mud explosions. On the other hand, it has a high level of human activity that increases the risk of disasters. As an effort to prevent and mitigate disasters, it is necessary to know the subsurface geological conditions of the crater. This study aims to determine the subsurface geological conditions of the crater. This research uses the methods of detailed geological mapping, manifestation observation, and Ground Penetrating Radar (GPR) geophysical survey. The tool used is Akula Geoscanner 9000C running at 64.75 Hz frequency, capable of penetrating 50 meters deep, and has a vertical resolution of > 0.85 meters. Sikidang Crater is located at the southeastern foot of Mount Pangonan and it forms semicircular like a horseshoe. According to Van Zuidam, the crater is classified as a solfatara and fumarole field geomorphology unit. The lithology of this area is dominated by the eruption products of Mount Pangonan. In general, radargrams resulting from GPR surveys show various amplitudes of reflected electromagnetic waves. This is consistent when correlated with the variation in rock density of the research area. At some points, there is a decrease in electromagnetic wave velocity due to contrast in dielectric constant values, which is interpreted as geothermal fluid flow towards the surface. The potential level of geothermal fluid flow is classified into high, medium, low, and none based on the density of potential points seen in the radargram.

Flexible multifunctional magnetic-conductive Janus nanocomposite films towards highly-efficient electromagnetic interference shielding and thermal management

The rapid development of aerospace, intelligent wearable electronics and 5G communications puts forward higher demands for electromagnetic interference (EMI) shielding materials. Herein, the flexible multifunctional magnetic-conductive Janus nanocomposite films with magnetic cobalt carbide nanowires/bacterial cellulose (Co@C NW/BC) blends as the upper side, and conductive Ti3C2Tx MXene as the bottom side are obtained via the layer-by-layer (LBL) vacuum assisted filtration-hot pressing method. The two magnetic and conductive sides endow the Janus nanocomposite films with distinctly different performances in EMI shielding and thermal management. When the electromagnetic waves are incident from Co@C NW/BC side, the films exhibit a high EMI shielding effectiveness (EMI SE) of 49.8 dB with an enhanced microwave absorption (SEA) of 33.9 dB at the ultralow thickness of 43 μm. Meanwhile, the Ti3C2Tx side exhibits improved electrical heating performances with a surface temperature of 120 °C at 6 V voltage, increased photothermal conversion temperature of 77.8 °C upon 2.0 kW/m2 light intensity, as well as excellent thermal stealth properties with a low radiation temperature of 88.4 °C on the 240 °C hot stage. Moreover, the Janus nanocomposite films show a high tensile strength of 80.0 MPa. The resultant Janus nanocomposite films possess great application prospects in highly-efficient EMI shielding and thermal management.

Efficient Solar energy harvesting via thermally stable tungsten-based nanostructured solar thermophotovoltaic systems

Electromagnetic radiations are a key energy source, which, by deploying bandgap-engineered devices, are directed onto PV cells to maximize their utilization. In this regard, the Solar Thermophotovoltaic (STPV) systems are vital, consisting of an intermediate absorber-emitter assembly between sunlight and solar cells. A theoretical and computational demonstration of a highly thermally robust, angularly stable, polarization-insensitive, and compact tungsten-based broadband absorber and spectrally selective emitter in symmetric metal-insulator-metal (W-SiO2-W) configuration has been presented. The nanoscale absorber consists of four differently-sized cylinders forming a supercell, and the emitter is cylindrical. The absorber has been optimized over a range of operating temperatures and solar irradiances, manifesting a very high absorption for the visible region with an average of 98.09% for 400 – 800nm, exhibiting > 99% absorption for a BW of 225nm with a peak of 99.99% at 674nm. The emitter has been optimized with 99.72% emissivity at the desired spectral location. The absorber’s intermediate efficiency is 99.91% for 5000 suns at 800 °C, which is as high as 72.33% at a target temperature of 3200 °C. This study aims to match a higher bandgap of 1.5eV perovskite solar cells and realize higher efficiency than tandem solar cells. The solar cell efficiency is 42.39%, which results in solar-to-electricity efficiency of 42.38%, exceeding the Shockley-Queisser (SQ) limit. As a proof-of-concept using a simulation program SCAPS-1D, a perovskite solar cell is illuminated using a bandgap-matched photon, increasing its efficiency from 26.67% to 45.79%. Thus, the presented idea achieves cell efficiency beyond the SQ limit without employing complex tandem cells.

Cubical radiator for three‐dimensional flexible beam controller with multiple radiation beams and directions

AbstractA novel approach for generation of the multiple three‐directional and controllable beams from a cubical electromagnetic (EM) wave radiator is proposed in this paper. This cubical radiator is a multiple‐mode EM resonator, which is formed by a cubical metal cavity. Three resonant modes are excited in this cavity resonator by a feeding slot. Besides the feeding slot, a few additional slots are opened on the side wall(s) of the cavity to act as the EM wave radiation elements. Various combinations of radiation slots contribute to different beam directions, for example, side‐direction (single radiation slot), edge‐direction (two radiation slots), and vertex‐direction of the cavity (three radiation slots). More combinations of these slots are further studied in the cases of side + edge and edge + vertex to illustrate the diversity in the directions of the produced EM beams. To validate the predicted results, two prototypes are fabricated and measured to display their far‐field radiation patterns. The measured results agree well with the full‐wave simulated ones, thereby demonstrating the possibility of a large number of the flexible EM beams, as well as the capability of the controllable beam directions.

Multifunctional electromagnetic wave absorbing carbon fiber/Ti3C2TX MXene fabric with superior near-infrared laser dependent photothermal antibacterial behaviors

Developing multifunctional materials which could simultaneously possess anti-bacterial ability and electromagnetic (EM) absorption ability during medical care is quite essential since the EM waves radiation and antibiotic-resistant bacteria are threatening people’s health. In this work, the multifunctional carbon fiber/Ti3C2Tx MXene (CM) were synthesized through repeated dip-coating and following in-situ growth method. The as-fabricated CF/MXene displayed outstanding EM wave absorption and highly efficient photothermal converting ability. The minimum reflection loss (RL) of −57.07 dB and ultra-broad absorption of 7.74 GHz could be achieved for CM composites. By growth of CoNi-layered double hydroxides (LDHs) sheets onto MXene, the absorption bandwidth for carbon fiber/Ti3C2Tx MXene layered double hydroxides (CML) could be reach 5.44 GHz, which could cover the whole Ku band. The excellent photothermal effect endow the CM composites with excellent antibacterial performance. The antibacterials tests indicated that nearly 100 % bactericidal efficiency against E. acoil and S. aureus was obtained for the CM composite after exposure to near-infrared region (NIR) irradiation. This work provides a promising candidate to combat medical device-related infections and EM pollution.

A novel magnetoelastic biosensor consisting of carbon quantum dots/nitrocellulose membranes and NiFe2O4/ polylactic acid based on 3D printing for α2-macroglobulin detection

α2-macroglobulin (α2-M) have crucial clinical significance as a potent biomarker for diabetes nephropathy (DN). There is an increasing demand for rapid detection of α2-M. Herein, a magnetoelastic (ME) biosensor with a layered composite structure is developed for α2-M detection. Based on 3D printing, the basal layer of the biosensor is prepared as a grid structure fabricated by polylactic acid (PLA) doped with NiFe2O4. The conductivity of the biosensor was improved significantly due to the addition of multi-walled carbon nanotubes (MWCNTs). The biological site for capturing α2-M antigen was provided by the carbon quantum dots (CDs) coupled with anti-α-2M (anti-α2-M@CDs) in the nitrocellulose filter (NC) membrane. Meanwhile, the distribution of antibodies on the biosensor surface can be observed more directly due to the fluorescence characteristics of CDs. The biosensor in this work can realize multi-pattern recognition of fluorescent signal and electromagnetic signal. The results show that the limit of detection (LOD) was 0.506 ng/mL in the linear range from 10 ng/mL to 100 μg/mL and the linear equation of fitting curve is: y = 0.21 x - 0.15. The ME biosensors with a simple preparation method have advantages of high sensitivity, good stability and low LOD, showing the great potential for α2-M detection.

Enhanced tunable cavity development for axion dark matter searches using a piezoelectric motor in combination with gears

Most search experiments sensitive to quantum chromodynamics (QCD) axion dark matter benefit from microwave cavities, as electromagnetic resonators, that enhance the detectable axion signal power and thus the experimental sensitivity drastically. As the possible axion mass spans multiple orders of magnitude, microwave cavities must be tunable and it is desirable for the cavity to have a tunable frequency range that is as wide as possible. Since the tunable frequency range generally increases as the dimension of the conductor tuning rod increases for a given cylindrical conductor cavity system, we developed a cavity system with a large dimensional tuning rod in order to increase this. We, for the first time, employed not only a piezoelectric motor, but also gears to drive a large and accordingly heavy tuning rod, where such a combination to increase driving power can be adopted for extreme environments as is the case for axion dark matter experiments: cryogenic, high-magnetic-field, and high vacuum. Thanks to such higher power derived from the piezoelectric motor and gear combination, we realized a wideband tunable cavity whose frequency range is about 42% of the central resonant frequency of the cavity, without sacrificing the experimental sensitivity too much.

Bridging dielectric-magnetic synergistic units with MOFs on fibers structure for high-efficient microwave absorption at low filler loading

Metal-organic framework (MOF) capable of magnetic-dielectric synergy loss mechanisms shine in the field of electromagnetic wave (EMW) absorption, whereas their high filler loading in the matrix remains a challenge and limit their practical application. Here, we mono-disperse bimetallic CoZn-MOF on conductive carbon nanofibers precursor via electrospinning technique and a following heat-treatment was employed to construct a Co–ZnO@NC carbon nanofiber (CNF) composites. The Co–ZnO particles with a size of 2 μm are evenly distributed within the carbon fibers, forming a unique structure resembling a “pearl necklace”. The introduction of one-dimension (1D) CNF can prolong the electron transport path and effectively reduces the percolation threshold of the composites. The composites are endowed with abundant heterogeneous interfaces, excellent magnetic-dielectric synergy and improved impedance matching, benefiting from which the obtained Co–ZnO@NC CNF composites demonstrate a maximum reflection loss (RLmin) of −54.5 dB at a thickness of 2.3 mm and an effective absorption bandwidth (EAB) of 8.12 GHz at a filler loading of merely 10 %. This study provides a feasible strategy for the design of MOF-derived absorbers with enhanced microwave absorption capacity at low filler loading.

In-Plane heterogeneous Structure-Boosted interfacial polarization in graphene for wide-band and wide-temperature microwave absorption

Theoretically, the strong permittivity dispersion characteristic of materials is essential for achieving broadband electromagnetic wave (EMW) absorption, which can be realized via amplified interfacial polarization effects between a dielectric phase and a lossy phase, such as by increasing the accumulated charge density in their interface area. Herein, we propose a novel strategy to boost interfacial polarization based on heterogeneous structure design in in-plane graphene (Gr) since the in-plane conductivity of Gr is significantly higher than its out-of-plane conductivity. To this end, Gr is grown on Si3N4 nanowires skeleton using chemical vapor deposition (CVD). Subsequently, Gr is controllably etched by Ni nanoparticles, and then, open graphite nanosteps are formed, which help construct in-plane heterogeneous interfaces between Gr and a dielectric phase. Such interfaces also help improve the impedance matching performance by disrupting the long-range conductive network of CVD-grown Gr. Notably, an effective absorption bandwidth of 8.48 GHz is achieved with a thickness of 2.85 mm, which is significantly wider than the EAB (5 GHz) of the out-of-plane heterogeneous structure. In addition, the in-plane heterogeneous structure also endows the EMW absorption material with excellent high-temperature insensitivity, realizing full-frequency absorption in the X-band in the 298–873 K range. This strategy to boost interfacial polarization via novel in-plane heterogeneous structure construction in Gr provides an alternative approach to explore the potential of Gr-based hybrids with planified structures to achieve wide-band and wide-temperature EMW absorption.

A combined strategy to constructure MoX2 (X=Se and S)-based core@shell structure flower-like multicomponent nanocomposites for boosted conduction loss, polarization loss and microwave absorption capacities

Interfacial effects or/and magnetic/dielectric synergy can be utilized effective strategies to improve electromagnetic wave (EMW) attenuation. Herein, using CoNi nanospheres as precursor, core@shell CoNi@C nanospheres could be efficiently fabricated via a facile polymerization and subsequent thermal treatment. And core@shell CoNi/NiSe2/Co9Se8@C@MoSe2 and CoNi2S4/Co9S8@C@MoS2 flower-like multicomponent nanocomposites (MCNCs) were fabricated via hydrothermal reaction amongst the obtained CoNi@C, Mo and Se/S sources. The generated carbon acting as protective layer was verified to greatly restrain the selenization of CoNi nanospheres during the formation of MoSe2 nanosheets, generating CoNi/NiSe2/Co9Se8@C@MoSe2. And the complete sulfidation of CoNi alloys led to the formation of CoNi2S4/Co9S8@C@MoS2. Because of their boosted impedance matching, conductive and polarization loss abilities, the acquired flower-like MoX2 (X=Se and S)-based MCNCs displayed greatly improved EMW absorption characteristics (EMWACs) compared with their precursors. Especially, the extraordinary synergistic effect generated into the magnetic/dielectric MCNCs contributed to outstanding EMWACs of CoNi/NiSe2/Co9Se8@C@MoSe2 flower-like MCNCs. Accordingly, our findings provided a combined strategy to simultaneously make the most of magnetic/dielectric synergistic and interfacial effects for boosted conduction loss, polarization loss and EMWACs.

The Peculiar Precursor of a Gamma-Ray Burst from a Binary Merger Involving a Magnetar

The milestone discovery of GW170817-GRB 170817A-AT 2017gfo has shown that gravitational waves (GWs) could be produced during the merger of a neutron star–neutron star/black hole and that in electromagnetic (EM) waves, a gamma-ray burst (GRB) and a kilonova (KN) are generated in sequence after the merger. Observationally, however, EM properties before the merger phase are still unclear. Here we report a peculiar precursor in a KN-associated long-duration GRB 211211A, providing evidence of the EM before the merger. This precursor lasts ∼0.2 s, and the waiting time between the precursor and the main burst is ∼1 s, comparable to that between GW170817 and GRB 170817A. The spectrum of the precursor could be well fit with a nonthermal cutoff power-law model instead of a blackbody. In particular, a ∼22 Hz quasiperiodic oscillation candidate (∼3σ) is detected in the precursor. These temporal and spectral properties indicate that this precursor is probably produced by a catastrophic flare accompanied with magnetoelastic or crustal oscillations of a magnetar in a binary compact merger. The strong magnetic field of the magnetar can also account for the prolonged duration of GRB 211211A. However, it poses a challenge to reconcile the rather short lifetime of a magnetar with the rather long spiraling time of a binary neutron star system only by the GW radiation before the merger.

Nonlinear spatial evolution of degenerate quartets of water waves

In this manuscript we investigate the Benjamin-Feir (or modulation) instability for the spatial evolution of water waves from the perspective of the discrete, spatial Zakharov equation, which captures cubically nonlinear and resonant wave interactions in deep water without restrictions on spectral bandwidth. Spatial evolution, with measurements at discrete locations, is pertinent for laboratory hydrodynamic experiments, such as in wave flumes, which rely on time-series measurements at fixed gauges installed along the facility. This setting is likewise appropriate for experiments in electromagnetic and plasma waves. Through a reformulation of the problem for a degenerate quartet, we bring to bear techniques of phase-plane analysis which elucidate the full dynamics without recourse to linear stability analysis. In particular we find hitherto unexplored breather solutions and discuss the optimal transfer of energy from carrier to sidebands. We show that the maximal energy transfer consistently occurs for smaller side-band separation than the fastest linear growth rate. Finally, we discuss the observability of such discrete solutions in light of numerical simulations.

Multicomponent nonlinear fractional Schrödinger equation: On the study of optical wave propagation in the fiber optics

In this article, we investigate the soliton wave dynamics of the fractional three-component coupled nonlinear Schrödinger equation. This equation is considered as a fundamental tool for describing the behavior of optical pulses in optical fibers. There is increasing interest in studying these equations as they can be used to explain a wide range of complex physical phenomena in various scientific and engineering fields, including nonlinear fiber optics, electromagnetic field waves, and signal processing through optical fibers. In order to obtain the required solutions, the first step is to apply the complex wave transformations with β-fractional derivative to obtain the nonlinear ordinary differential equations of the governing model. Furthermore, by applying the novel integration methods known as generalized Arnous method and multivariate generalized exponential rational integral function approach, different type of soliton solutions are extracted. Different sets and values of the physical parameters are used to study the optical soliton solutions of the studied system. Based on a comparative analysis of our results with existing techniques, this study concludes that our proposed solutions are novel. The results described in this work are able to enhance the nonlinear dynamical behavior of a given system and confirm the effectiveness of the methods used. Furthermore, the different graphs are sketched to visualize the solutions behavior with various parametric values. It is anticipated that obtained solutions will be significant in the study of wave propagation and other related fields.

Nonlinear spatial evolution of degenerate quartets of water waves

In this manuscript we investigate the Benjamin-Feir (or modulation) instability for the spatial evolution of water waves from the perspective of the discrete, spatial Zakharov equation, which captures cubically nonlinear and resonant wave interactions in deep water without restrictions on spectral bandwidth. Spatial evolution, with measurements at discrete locations, is pertinent for laboratory hydrodynamic experiments, such as in wave flumes, which rely on time-series measurements at fixed gauges installed along the facility. This setting is likewise appropriate for experiments in electromagnetic and plasma waves. Through a reformulation of the problem for a degenerate quartet, we bring to bear techniques of phase-plane analysis which elucidate the full dynamics without recourse to linear stability analysis. In particular we find hitherto unexplored breather solutions and discuss the optimal transfer of energy from carrier to sidebands. We show that the maximal energy transfer consistently occurs for smaller side-band separation than the fastest linear growth rate. Finally, we discuss the observability of such discrete solutions in light of numerical simulations.

Development of CuS/C composite for microwave absorption using lignin biopolymer

In recent decades, electronic devices have become a crucial component of everyday life and an increasingly important aspect of national security. However, despite their convenience, the emission of electromagnetic (EM) radiation from these devices has created a pollution issue that demands urgent attention. In this study, the properties and performance of CuS/C composites as EM wave-absorbing materials were examined. The main technique employed involved modifying the surface structure and properties of a lignin biopolymer via a fiber laser to derive porous carbon as a microwave absorber in the X-band range. Flower-like CuS microspheres were integrated into the porous carbon to improve the electrical conductivity and promote internal reflections. In addition, multilayer microwave absorbers were developed using CuS/C/epoxy composites with varying weight percentages, which were fabricated through refluxing and annealing techniques. The return losses of the absorbers in single- and multi-layer modes were optimized by modified local particle swarm optimization (MLPSO). The minimum average return loss improved to −15 dB (96.8%) by optimization in the 4-layer mode with a thickness of 1.8 mm. The optimum absorption peak in the 3-layer structure was −54.52 dB at a frequency of 8.83 GHz. The shielding effectiveness assessments indicated that the CuS/C/epoxy composite significantly improved the shielding capabilities of porous C and CuS, resulting in an increase of the shielding effectiveness threshold (SET) from less than 2 dB in lignin to more than 10 dB in CuS/C/epoxy.