Effective Absorption Research Articles

Synthesis and high electromagnetic wave absorption performance of carbon-enriched porous SiOC ceramics

The carbon-enriched porous SiOC ceramics with enhanced electromagnetic wave (EMW) absorption properties were synthesized through the hydrothermal method followed by a polymer-derived ceramics (PDCs) process. As the annealing temperature rises from 1200 °C to 1500 ℃, SiC and SiO2 crystals are gradually separated from the porous amorphous SiOC matrix, and the degree of graphitization of free carbon increases. The porous SiOC ceramics annealed at 1400 °C exhibit the presence of SiC, SiO2, turbostratic graphite, and amorphous SiOC phases, which significantly impact the impedance matching and attenuation constant of the material. The minimum reflection loss (RLmin) value of the SiOC ceramics reaches −67.98dB with a matching thickness of 3.19mm and the effective absorption bandwidth (EAB) is 4.45GHz at 1.39mm. The carbon-enriched porous SiOC ceramics with strong absorption capacity and wide absorption bandwidth are primarily owing to appropriate impedance matching and multiple attenuation mechanisms, such as conduction loss, interfacial polarization, and defect-induced polarization, indicating that the SiOC ceramics exhibit significant potential as a high-performance EMW absorbing material.

Study on microwave absorbing properties of reduced graphene oxide@Co/Fe81.5Si3B9P3C1Cu1Ti1.5 amorphous nanocrystalline composite

Electromagnetic pollution problems and military stealth technology need to be solved, the development of new wave absorbing materials has been imminent. In this study, reduced graphene oxide@Co (rGO@Co) powder is obtained by alcoholthermal method, afterwards the different contents of rGO@Co powders are also compounded with Fe81.5Si3B9P3C1Cu1Ti1.5 nanocrystalline powder by high-energy ball milling, obtaining rGO@Co/Fe81.5Si3B9P3C1Cu1Ti1.5 nanocrystalline composite powder, and powder morphology, the nuclear layer structure, soft magnetic properties and corresponding absorbing properties of the materials are studied. The research results are that rGO coats Co and Fe-based nanocrystalline of double magnetic cores in the composite powder, which realizes the synergy of the two magnetic cores to enhance the magnetic loss, is also compatible with the dielectric loss of rGO, and also improves the impedance matching. The minimum reflection loss (RLmin) is −44.18 dB, and the maximum effective absorption bandwidth (EAB) is 5.03 GHz in the amorphous nanocrystalline alloy matrix. When the addition of rGO@Co powder is 1 wt%, the RLmin of composite powder is −52.41 dB (3 mm), which is increased by 18.6 %. The EAB is 6.07 GHz (2 mm), which is increased by 20.7 %.

Design and performance of 3D-Printed ABS@rGO/CF/CeO2 composites for microwave absorption and mechanical strength

Traditional microwave absorbing materials struggle to balance wideband absorption with mechanical properties, particularly in multifunctional applications. This study explores the effects of short carbon fibers (CF), cerium dioxide (CeO2), and reduced graphene oxide (rGO) on the electromagnetic and mechanical properties of 3D-printed composites. The ABS@CF/CeO2/rGO composite with a thickness of 2.2 mm exhibited exceptional microwave absorption, achieving an effective absorption bandwidth (EAB) of 6.6 GHz and a minimum reflection loss (RLmin) of −40.9 dB. The Whale Optimization Algorithm (WOA) was employed to design a load-bearing, microwave-absorbing superstructure, which significantly improved wideband absorption. Experimental results confirmed the superstructure’s isotropy and wide-angle absorption capabilities. The calculated electromagnetic parameters were applied to evaluate the radar cross-section (RCS) of large targets, demonstrating enhanced stealth performance for unmanned aerial vehicles (UAVs). Mechanical tests revealed that rGO improved interlayer bonding strength, while CF negatively impacted bending performance. The superstructure also showed excellent mechanical stability in load-bearing tests, underscoring its potential for practical engineering applications. This study offers insights into designing advanced composite materials with balanced electromagnetic and mechanical properties, guiding future multifunctional material development.

Construction of 2D/2D heterostructure with porous few layer g-C3N4 and NiCo2O4 nanosheets towards electromagnetic wave absorption

Developing high-performance materials with ultra-high reflection loss (RL ≤ -65 dB) for electromagnetic wave (EMW) absorption is pivotal to address electromagnetic pollution, but it is still challenging. Herein, a two-dimensional (2D)/2D PFL g-C3N4/NiCo2O4 heterostructure with porous few-layer g-C3N4 (PFL g-C3N4) and ultrathin NiCo2O4 nanosheets has been prepared by self-assembly, hydrothermal reaction, and calcination strategies. The 2D/2D heterostructure exhibits extraordinary EMW absorption property, achieving a reflection loss (RL) value of -68.59 dB and an effective absorption bandwidth (EAB) of 1.92 GHz at a matching thickness of 2.5 mm. As expected, the porous few layer g-C3N4 nanosheets provide rich interface which increases multiple reflection paths and enhances the conduction loss. The cooperative effects of magnetic loss, dielectric loss, and impedance matching contribute to the exceptional EMW absorption property of PFL g-C3N4/NiCo2O4 (2D/2D) heterostructure. The potential of PFL g-C3N4/NiCo2O4 in actual radar stealth is verified through radar scattering cross-section (RCS) simulation. This work paves the way for utilizing 2D/2D heterostructure as an ultra-efficient EMW absorbers.

Preparation of broad-bandwidth porous carbon electromagnetic wave absorption materials from agricultural waste corncob

Developing advanced electromagnetic wave-absorbing materials tend to focus on the characteristics of low cost, renewability, environmental friendliness, strong absorption, wide bandwidth, and lightweight. This paper described the preparation of porous carbon electromagnetic wave-absorbing materials with strong absorption, broad bandwidth and thin thickness by one-step charring of corncob, an agricultural waste. The corncob porous carbon (CPC) materials were prepared when the charring temperature was 600 °C, the charring time was 3 h and the activator ratio was 0.25:1. The obtained CPC exhibited porous microstructure with average pore size of approximately 1 μm. Its specific surface area was 713.971 m2·g−1, with pore volume of 0.289 mL·g−1 and high degree graphitization. CPC showed excellent electromagnetic wave absorption performance with minimum reflection loss (RL min) of −38.21 dB and effective absorption bandwidth (EAB) of 5.6 GHz at a relatively thin thickness of 2.0 mm. CPC was capable of absorbing 99.9 % of electromagnetic wave (EMW).

Microwave absorption properties of one-step formed CNTs/Fe3O4-carbonyl iron superflexible buckypaper by directional pressure filtration

In order to realize the integration of structure and function of microwave-absorbing materials, carbon nanotubes/magnetic nanoparticle buckypaper (CNT/MNP BP) self-supporting, ultra-flexible, ultra-thin and ultra-light composites were prepared by composing CNTs with MNPs through directional pressure filtration technology. The BP composite, with a bulk density of 0.62 g/cm3 and a thickness of 0.21 mm, can be uninterruptedly tightly wound around a 4 mm diameter glass rod many times without structural damage. The microwave-absorbing properties and magnetic properties of the CNT/MNP composites with different compositions and contents were systematically analyzed. The CNT-Fe3O4 Buckypaper with 33.3 wt% Fe3O4 content (CF33.3 %) has the best electromagnetic wave absorption capability, with a minimum reflection loss value of −52.01 dB and an effective absorption bandwidth of 4.08 GHz. The VSM test shows that the saturation magnetization strength of CF33.3 % is 38.4 emu/g. The excellent electromagnetic wave absorption performance is attributed to the polarization and conduction losses of CNTs, natural resonance, exchange resonance and eddy current losses of MNPs, and multiple scattering and reflection within the porous network structure of the composites. The CNTs and MNPs has good dispersion in the buckypaper, where CNTs construct a superflexible skeleton besides an excellent conductive network. The self-supporting superflexible CNT/MNP BP composites have a good application prospect in the field of wearable electronic devices in the future.

Fe2O3-decorated multiwall carbon nanotube composites for boosted microwave absorption

Developing microwave absorption (MA) materials with a strong absorption ability over a wide bandwidth through a simple and environmentally friendly approach remains a tremendous challenge. Herein, we propose to use an Fe3+–tannic acid framework to assist the dispersion of multi-walled carbon nanotubes (MWCNTs) and successfully prepare MWCNTs/porous carbon/α-Fe2O3 composites through freeze-drying and subsequent heat treatment. The dielectric properties and MA performance can be regulated by the heat treatment temperature, which leads to tunable crystalline structure, composition, and graphitization degree of MWCNTs. Consequently, the MWCNTs/porous carbon/α-Fe2O3 composite heat-treated at 300 °C exhibits a high reflection loss (RL) of −58.9 dB and an effective absorption bandwidth (5.28 GHz) with a matched thickness of 2.26 mm at a filler proportion of only 5 wt%, and the related frequency bandwidth with RL below -10 dB reaches 14.3 GHz at a thickness of 2–5 mm. In conclusion,the balance between conduction and polarization loss endows the composite with excellent impedance matching and boosting MA performance. This study offers a guideline for fabricating excellent MA materials through a simple, environmentally friendly method.

Multi-shell bowl-like carbon microspheres for lightweight and broadband microwave absorption

Carbon materials have made significant progress in the field of microwave absorption (MA), but achieving wide effective absorption bandwidth (EAB) at low filler content still remains a great challenge. In this work, we design multi-shell bowl-like mesoporous carbon microspheres (MBMCs) by a facile hard template method for efficient MA. It is demonstrated that the spacing between inner and outer shell and second shell thickness play a vital role on the configuration of carbon microspheres. By controlling the second addition of silica template, the microstructure of carbon microsphere evolves from spherical to bowl shape geometry. Expanded shell spacing is beneficial for forming bowl-like microsphere. The dielectric loss and MA properties are highly associated with the configuration of MBMCs. Well-proportioned MBMCs with appropriate shell spacing present wide EAB of 7.3 GHz under a low filling ratio of 12 wt.%. This work paves a new way to broaden EAB and lower filling content of carbon materials via asymmetric multilayer microstructure design.

Fabrication of core–shell nickel ferrite@polypyrrole composite for broadband and efficient electromagnetic wave absorption

Herein, nickel ferrite@polypyrrole (NiFe2O4@PPy) composite was prepared by a simple two-step route of solvothermal synthesis and in-situ oxidation polymerization reaction. The results of micromorphology analysis showed that the obtained NiFe2O4@PPy composite had a unique core–shell structure, good magnetic performance and electrical conductivity. Furthermore, the as-prepared magnetic/conductive NiFe2O4@PPy composite exhibited notably enhanced electromagnetic wave (EMW) absorption performance than pure NiFe2O4 and PPy. When the filling ratio was 17.5 wt% and the matching thickness was 2.24 mm, the optimal minimum reflection loss (RLmin) of −56.25 dB and a broad effective absorption bandwidth (EAB) of 5.2 GHz were achieved for NiFe2O4@PPy composite. With slightly increasing the matching thickness to 2.6 mm, the maximum EAB of 7.12 GHz could be reached. Additionally, the probable EMW absorption mechanism was elucidated. Therefore, this work could provide a valuable reference for the preparation of magnetic ferrite/conductive polymer composites as broadband and high-efficiency EMW absorbers.

Lightweight composite from graphene-coated hollow glass microspheres for microwave absorption

In developing the effective and lightweight materials for microwave absorption, graphene holds a bright promise because of its excellent electrical properties and low density, but it suffers from poor impedance matching; while the hollow glass microspheres on the other hand have extremely low density and are dielectric. Their synergistic combination could achieve a perfect impedance matching and thus create a novel lightweight absorption composite. The metamaterial structure absorber can efficiently absorb electromagnetic waves over a wide frequency range. This study employs a hydrothermal method to deposit graphene onto the surfaces of hollow glass microspheres, followed by the design of a metamaterial absorber. Upon coating with graphene flakes, the composite material effectively dissipates electromagnetic wave energy through mechanisms such as interfacial polarization, dielectric loss, and the multiple scattering effects of hollow glass microspheres and graphene flakes. The composite exhibits an effective absorption bandwidth up to 4.02 GHz under a graphene flakes mass fraction of 30 %. More importantly, the incorporation of the metamaterial absorber design further significantly enhances the absorption bandwidth to 7.7 GHz. This material demonstrates significant advantages in terms of lightweight and broadband absorption performance, providing new insights for the research of high-performance lightweight and wideband absorbing materials in the future. However, further investigation is required to examine its long-term stability and performance in complex environments.

One-step pyrolysis derived Fe and heteroatom co-doped biochar composites for efficient microwave absorption

Electromagnetic (EM) pollution frequently disrupts the regular operation of sophisticated electrical devices, necessitating the urgent development of lightweight EM wave absorbers that possess powerful absorption capability. Herein, we report a simple method for the preparation of Fe and heteroatom co-doped biochar composites (FeX-BC, where X = N, S) by directly carbonizing the precursors of anhydrous FeCl3, cherry kernel powder, and heteroatom dopants (melamine or Na2S2O3·5H2O). By adding different amounts of dopants during the synthesis of the precursors, it is possible to adjust the heteroatom content of the FeX-BC samples with precision. It is worth mentioning that the FeN0.1-BC composite delivers the best EM wave absorption performance with an effective absorption bandwidth of 4.8 GHz and a minimal reflection loss of −63.2 dB. Furthermore, the significant attenuation of EM wave can be attributed to the synergistic interplay of magnetic loss, dielectric loss and the enhanced impedance matching. This study introduces a simple methodology for the fabrication of EM wave absorbers, a significant contribution to the synthesis, advancement, and functional applications of biomass-derived materials.

In-situ study on the differential evolution of He bubbles in the multilayer oxide of Fe9Cr1.5W0.4Si F/M steel corroded in lead-bismuth eutectic

The combined effects of corrosion and irradiation on nuclear components have been an important but not yet fully revealed topic. Here, the irradiation behavior of the oxide scale formed on F/M steel after lead-bismuth corrosion was in-situ investigated during He+ irradiation. The results showed that the oxide scale included a Fe3O4 outer oxide layer, a nanograin Fe(FexCr2-x)O4 spinel inner oxide layer, and an internal oxide layer. He bubbles formed in Fe3O4, Fe-Cr spinel and F/M steel were polygon, irregular elongated pores and small spheres, respectively. These differences were attributed to variations in defect generation, migration, and corrosion-induced crystal defects in different oxides. Numerous corrosion-induced nanograin boundaries and vacancies in Fe-Cr spinel exhibited more effective absorption of irradiation-induced defects. Moreover, rhombic perfect dislocation loops were detected in Fe3O4 at the late stage of irradiation, their relative positional relationship with He bubbles indicated a potential interaction between bubbles and loops.

One-step fabrication of a novel fiber-based absorber for flexible, tunable and boosted microwave absorption

The increasingly intricate electromagnetic environment necessitates higher anti-electromagnetic interference capabilities for electronic devices, thereby demanding a flexible absorbing material that can adapt to multiple forms, is lightweight, and exhibits excellent electromagnetic wave (EMW) absorption properties. In this study, we have developed a novel flexible absorbing material (FAM) based on glass-coated amorphous magnetic fibers (SFs) and Dallenbach-like absorbing structures through wet forming technology. By combining high-performance absorbing fiber with textile structures, the FAM demonstrates EMW absorption performance along with lightweight flexibility and shape adaptability. This paper explores the influence of process parameters in wet forming technology on FAM formation; as well as examines the construction of broadband absorbers through structural optimization. A single-layer FAM with a thickness of 1.7 mm (SFs length 8 mm, content 3 g/m2) achieves an impressive reflection loss (RL) value of −60.1 dB at 11.6 GHz. Furthermore, optimized multi-layer FAM attains effective absorption bandwidth (EAB: RL ≤ −5 dB) across a wide range from 3–14 GHz. This work presents a new approach for developing ’lightweight, thin, wide, and strong’ absorbing materials based on fiber and textile structures which holds significant implications for civilian electromagnetic interference protection as well as military electromagnetic stealth technology.

A comprehensive DFT Study of the electronic structure and optical properties of Iodine-based halide double perovskites for photovoltaic applications

This study aims to explore the electronic structure, thermodynamic, mechanical stability, and optical response of Iodine-based ordered vacancy double halide perovskite compounds through the application of density functional theory. The two compounds Cs2ZrI6 and Rb2ZrI6 exhibit thermodynamic stability, with displaying particularly notable. Moreover, analysis of the calculated coefficients of elastic stiffness confirms the mechanical stability of all materials under ambient pressure conditions. By using the Density Functional Theory with Spin-Orbit Coupling (SOC), it was observed that Cs2TeI6 and Rb2TeI6 possess an indirect band gap located between the X and L high-symmetry points, this show that Cs2TeI6, Rb2ZrI6, Cs2HfI6, and Rb2HfI6 are identified as direct semiconductor compounds. Moreover, the band gap values of X2YI6 (where X = Cs, Rb, and Y = Te, Zr, and Hf) exhibit an increasing trend as we progress along the alkali and transition metal elements in the periodic table, ranging from 1.422 eV for Cs2TeI6 to 2.465 eV for Rb2TeI6. Besides, the optical behavior of the visible light show that X2YI6 compounds have a high absorption of about 70%, reflectance of 30%, and a low transmittance. Thanks to their advantageous bandgap, enduring stabilities, and effective absorption of visible light, Cs2TeI6 and Rb2TeI6 hold significant promise for a wide range of electronic and optoelectronic applications, particularly in photovoltaics.

High-performance cobalt-embedded SiC nanofiber fabric for microwave dissipation

The incorporation of magnetic ingredients is critical for ceramic-based microwave absorbers with high efficiency. However, this task is becoming challenging due to the dispersion and oxidation issues. In this study, metal-organic framework (MOF) ZIF-67 was employed as the precursor of magnetic compounds and combined with a polymer solution to fabricate SiC textiles using the electrospinning technique. The microstructure analysis confirmed the successful introduction of MOF particles within the SiC nanofibers. Further examination of chemical compositions and magnetic properties revealed the encapsulation of magnetic compounds in hybrid SiC textiles. Since the applied fabrication approach ensures a superior dispersion and protection of metal compounds in a ceramic matrix, the microwave absorption of SiC fabric with both dielectric loss and magnetic loss exhibits a high reflection loss of -59.4 dB and a wide effective absorption band of 5.70 GHz. The current fabrication strategy for fabricating microwave absorbers with dual loss mechanisms advances the development of ceramic-based microwave absorption materials.

Thickness-controlled HsGDY/N-doped double-shell hollow carbon tubes for broadband high-performance microwave absorption

With the increasing deterioration of the electromagnetic environment, it is important to develop new and efficient electromagnetic wave-absorbing materials. In this work, bilayer hollow HsGDY/NC nanotubes with controllable thickness are constructed by introducing high conductivity polydopamine (PDA) and hydrogen-substituted graphdiyne (HsGDY) followed by the etching and carbonization. Subsequently, the effects of the composition, coating order, and structural characteristics of nanotubes on the electromagnetic parameters are thoroughly investigated, thereby analyzing the microwave absorption mechanism. The impedance matching of HsGDY/NC is optimized by changing the thickness of NC layer, while utilizing unique multi-heterogeneous interfaces and hierarchical conductive structures that enhance the interface polarization and conductive loss. As a result, HsGDY@NC-3 displays the optimal absorbing performance with an effective absorption bandwidth (EAB) of 7.8 GHz (10.1–17.9 GHz) and a minimum reflection loss (RLmin) of −47.18 dB at the filler content of only 11 %. This work broadens the application scopes of HsGDY and provides a novel insight into the design of lightweight, high-efficiency, and wide-frequency microwave absorbers, which is expected to be a potentially effective microwave-absorbing material.

Effect of Sound Absorption on Noise Reduction in the Automotive Industry

Industrial noise is one of the most common physical factors that cause annoyance and damage to workers' health in the long term. Precautions should be taken to reduce noise and to improve acoustic performance in industrial working environments. This paper aims to analyze the acoustic performance of the automotive industry contributes to the global outcomes of sustainability and develop strategies for improving the quality of the working environment through improvement scenarios. For this purpose, the automotive industry in Türkiye was examined as a case study. In-situ acoustic measurements were made in the seat manufacturing unit of an automotive factory, and the current situation was transferred to the simulation program. The effects of acoustic improvements on A-weighted sound pressure level and reverberation time at mid-frequencies (500, 1000, 2000 Hz) were investigated through three scenarios. In the investigations, noise distributions were carried out through noise mapping. The A-weighted sound pressure levels in the automotive industry were reduced by approximately 15 dB. As a result of the study, suggestions for noise control precautions and their effects on the automotive industry seat manufacturing unit are presented.

Effect of Structure and Wearing Modes on the Protective Performance of Industrial Safety Helmet.

This study aims to explore the effects of helmet structure designs and wearing modes on the protective performance of safety helmets under the impact of falling objects. Four helmet types (no helmet, V-shaped, dome-shaped, and motorcycle helmets) and five wearing modes (left and right tilt by 5 deg, backward tilt by 15 deg, 0 deg without chin strap, 0 deg with chin strap) were included in this study. The axial impact of a concrete block under various impact velocities was simulated. The results indicate that the energy absorption and shock mitigation effects of the foam cushion are superior to those of the suspension system in traditional industrial safety helmets. The structure of the top of V-shaped helmets is designed to withstand greater impact. Regarding the wearing mode, the helmet strap's deflection angle increases stress in the brain tissue and skull, heightens intracranial pressure, and causes pressure diffusion toward the forehead.

Flexible composites of Ni-Fe fiber/NBR for effective electromagnetic wave absorption

Flexible composites of Ni-Fe fiber/NBR for effective electromagnetic wave absorption

Technological and Mechanical Studies on Additively Manufactured Cellular Structures Made of the Ultrafuse 316L Composite Filament

Regular cellular materials produced using additive manufacturing (AM) techniques represent a significant development trend in modern engineering materials. Depending on the applied elementary unit cell of topology, it is possible to define the course of the structure deformation process in order to obtain the highest possible energy absorption effectiveness. This feature makes regular cellular structural materials particularly attractive for a number of industrial branches. This paper presents the results of technological trials and the results of experimental studies on the mechanical properties of regular cellular structures made using 3D printing technology under compression test loading conditions. The material used for their production was the Ultrafuse 316L filament and the fused filament fabrication (FFF) technique. The proposed material is a polymer-metal composite with a manufacturing process similar to metal injection moulding (MIM). The adopted research methodology included a feasibility study aimed at achieving material homogeneity and compression tests of the developed and manufactured regular cellular structures under quasi-static loading conditions. Several structural topologies were analysed. Experimental results indicated that regular cellular structures made from 316L steel exhibit high mechanical strength and extensive plastic deformation capabilities. The utilized in this work manufacturing technology used combines the advantages of 3D printing process with the potential of powder metallurgy. The proposed technique of structure manufacturing process is much cheaper than other based on melting metallic powders.