Excellent Electromagnetic Wave Absorption Research Articles

Preparation of coal gangue foam concrete modified by nanomaterials: Physical properties, pore structure, and electromagnetic properties

In this study, coal gangue foam concrete (CGFC) was modified with nanomaterials to optimize its electromagnetic wave (EWV) absorption performance. Single-factor test was carried out to explore the effects of nano-silica (NS) and nano-calcium carbonate (NC) on the physical characteristics, hydration products and microstructure of CGFC. The results showed that the compressive strength of CGFC was the optimal when NS and NC were mixed with 1.5 wt% each, in which case the volume water absorption also decreased to the lowest value of 20.61 %. Additionally, compared with the control group, the incorporation of NS significantly accelerated the cement hydration rate. Moreover, the synergistic effect after the addition of NC promoted the cement hydration to generate more ettringite and C-S-H gel, and partly reduced the average pore size of CGFC, thereby improving the pore structure. Finally, the attenuation constant of the composite material can reach 187.92, and the reflection loss can reach −35.6 dB, demonstrating its excellent electromagnetic wave absorption ability.

Synthesis of Mo2C/C nanoclusters attached on rGO nanosheets for high-Efficiency electromagnetic wave absorption

It is an effective strategy that constructing composites with a multi-dimensional structure synergistically enhance their electromagnetic (EM) wave absorbing performance. Herein, a high-efficiency EM wave absorber of Mo2C/C nanoclusters uniformly encapsulated in rGO nanosheets (Mo2C/C-rGO) was prepared by a combination of the directing freeze-dry and subsequently carbothermal reaction method. Mo2C/C was in-situ induced from spherical phosphomolybdic acid/polypyrrole (PMo12/PPy) to result in a unique cluster-like microstructure. Abundant heterogeneous interfaces endowed the Mo2C/C-rGO composites with excellent EM wave absorption performance at a low filling ratio of 5 wt%. The minimum reflection loss (RL) value was −49.3 dB at 1.38 mm and the maximum effective absorption bandwidth (EAB, RL<-10 dB) was 5.12 GHz at 1.60 mm. The excellent performance was owing to the lamellar structure and abundant heterogeneous interfaces in Mo2C/C-rGO, lengthening the transmission path of the incident wave, as well as resulting in high conduction loss and interfacial polarization loss. This universal strategy would be extended to other absorbers with multi-interface structures for lightweight and broadband EM wave absorption.

High-performance electromagnetic wave absorption in VS2@multi-walled carbon nanotube composites

In this work, composites comprising VS2 and multi-walled carbon nanotubes (MWCNTs) were prepared using a simple hydrothermal method. The MWCNTs were dispersed among the VS2 nanosheets, which produced dipole polarization and interfacial polarization, thus enhancing the dielectric loss. Meanwhile, the electrical conductivity of the composites gradually increased with the rising content of the MWCNTs, which improved the electromagnetic wave absorption performance. By adjusting the mass ratio of VS2 to MWCNTs to 5:1, a minimum reflection loss value (RL) of −24.7 dB was achieved with a thickness of only 1.3 mm at a frequency of 14.4 GHz. Besides, when the thickness was reduced to 1.2 mm, the effective absorption bandwidth extended to 3.75 GHz. The results suggest that impedance matching and the synergistic effect of multiple loss mechanisms contribute to the excellent electromagnetic wave absorption performance of the materials. Consequently, the VS2/MWCNTs composites exhibit simple synthesis, wide absorption bandwidth, thin thickness, and high absorption capacity, rendering them a promising material for practical microwave absorption applications.

Multi-scale design of MWCNT/glass fiber/balsa wood composite multilayer stealth structure with wide broadband absorption and excellent mechanical properties

In unmanned aircraft applications, electromagnetic wave (EMW) absorbers suffer from defects in narrow absorption bands and poor mechanical properties. To solve the problems, a lightweight multilayer stealth structure with wide broadband absorption performance and excellent mechanical properties was designed and prepared by adjusting microscopically the number of multi-walled carbon nanotubes (MWCNT) and modulating macroscopically the thickness-matching relationship of the structure to promote the absorption of EMW synergistically. Under the MWCNT of 30 wt% and the depletion layer with the thickness of 0.2 mm, the effective absorption bandwidth (EAB) covers the entire Ku-band while maintaining a minimum reflection loss (RL) of −15 dB. Besides, the radar cross-sectional area attenuation is as high as 23.1 dBm2, as well as the mechanical properties of the radar absorbing structures (RAS) were improved significantly due to the reducing structural density from balsa wood and the enhancement effect of glass fiber mats (GFM). The study constructed balsa-based RAS with excellent EMW absorbing and mechanical properties from both micro-nano scale and macro-structure, providing a research route for designing high-performance and lightweight stealth structures.

Microstructure evolution and excellent electromagnetic wave absorption performance of SiBCN fibers

In this work, SiBCN fibers with excellent electromagnetic wave (EMW) absorption performance were fabricated using electrospinning technology, followed by curing, pyrolysis, and heat treatment. Microstructure evolution and EMW absorption performance of SiBCN fibers after heat treatment at 1200–1600 °C were investigated. After heat treatment at 1200 °C, the conductive turbostratic C was precipitated from amorphous SiBCN fibers, resulting in minimum reflection loss (RLmin) reaching −63 dB and efficient absorption bandwidth (EAB) reaching 5.2 GHz. While turbostratic C and nano-SiC grains were simultaneously precipitated from SiBCN fibers heat treated at 1400 °C, and the RLmin reached −67 dB. The excellent EMW absorption performance of SiBCN fibers was mainly attributed to the synergistic effect of conductive loss, dipole polarization, and interfacial polarization. This work can guide the fabrication of high-performance EMW-absorbing ceramic fibers.

A Semi-amorphous Ti-BDC-derived Ti/C nanocomposite for efficient electromagnetic wave absorption

Electromagnetic (EM) interference presents a crippling risk to both human health and the dependability of technological devices. Due to their diverse advantages, metal-organic framework (MOF) derivatives have received much attention in developing novel EM wave-absorbing materials. Nevertheless, achieving desirable EM wave absorption capabilities in magnetic carbon-based absorbers through deliberate adjustment of MOFs remains a difficult task. In this study, a novel nanoporous carbon material (TiO2/C) has been successfully synthesized by a semi-amorphous material (Ti-BDC), which has excellent EM wave absorption properties. In detail, the minimum reflection loss (RL) of −49.7 dB and broad effective absorbing bandwidth (EAB) of 4.16 GHz can be reached with an absorbent thickness of 2.2 mm. The improved performance is mostly due to the dipole polarization of the functional groups and the even distribution of the nanoparticles, which form a seamless network. This promotes the dissipation of polarization and dielectric energy at the interface. In addition, the TiO2 nanoparticles on the carbon material improve the impedance matching, further enhancing the material's absorption performance.

In Situ Exsolution-Prepared Solid-Solution-Type Sulfides with Intracrystal Polarization for Efficient and Selective Absorption of Low-Frequency Electromagnetic Wave.

The excellent dielectric properties and tunable structural design of metal sulfides have attracted considerable interest in realizing electromagnetic wave (EMW) absorption. However, compared with traditional monometallic and bimetallic sulfides that are extensively studied, the unique physical characteristics of solid-solution-type sulfides in response to EMW have not been revealed yet. Herein, a unique method for preparing high-purity solid-solution-type sulfides is proposed based on solid-phase in situ exsolution of different metal ions from hybrid precursors. Utilizing CoAl-LDH/MIL-88A composite as a precursor, Fe0.8Co0.2S single-phase nanoparticles are uniformly in situ formed on an amorphous substrate (denoted as CoAl), forming CoAl/Fe0.8Co0.2S heterostructure. Combing with density functional theory (DFT) calculations and wave absorption simulations, it is revealed that Fe0.8Co0.2S solid solution has stronger intracrystal polarization and electronic conductivity than traditional monometallic and bimetallic sulfides, which lead to higher dielectric properties in EM field. Therefore, CoAl/Fe0.8Co0.2S heterostructure exhibits significantly enhanced EMW absorption ability in the low-frequency region (2-6GHz) and can achieve frequency screening by selectively absorbing EMW of specific frequency. This work not only provides a unique method for preparing high-purity solid-solution-type sulfides but also fundamentally reveals the physical essence of their excellent EMW absorption performance.

Preparation of nitrogen-doped reduced graphene oxide/zinc ferrite@nitrogen-doped carbon composite for broadband and highly efficient electromagnetic wave absorption

Traditionally reduced graphene oxide (RGO)-based electromagnetic wave (EMW) absorbing materials have poor absorption effectiveness due to impedance mismatch caused by skin effect. The introduction of structural defects and the design of heterogeneous interfaces play a crucial role in enhancing the polarization effect of EMW absorbers. In this study, nitrogen-doped reduced graphene oxide/zinc ferrite@nitrogen-doped carbon (NRGO/ZnFe2O4@NC) ternary composite with rich heterogeneous interfaces is constructed by combining solvothermal reaction, in-situ polymerization, annealing treatment with subsequent hydrothermal reaction. The research results have shown that the obtained NRGO/ZnFe2O4@NC ternary composite exhibits a unique core-shell structure and excellent EMW absorption performance. At a thickness of 2.61 mm, the maximum effective absorption bandwidth can reach 7.2 GHz, spanning the entire Ku-band and a portion of the X-band, and the minimum reflection loss is –61.1 dB, which is superior to most reported RGO-based EMW absorbers. The excellent EMW absorbing ability is mainly ascribed to the optimized impedance matching and the enhanced polarization loss caused by the abundant heterogeneous interfaces and structural defects derived from heteroatomic nitrogen doping. Furthermore, the radar cross section in the far field is simulated by a computer simulation technique. This study provides a novel way to prepare core-shell magnetic carbon composites as highly efficient and broadband EMW absorbers.

Novel carbonitriding process of high-entropy alloys using mechanochemical process for obtaining excellent high-frequency electromagnetic properties

Achieving excellent electromagnetic-wave absorption (EMA) performances and outstanding multifunctional physicochemical properties in complicated application environments is a great challenge for high-entropy alloys (HEAs) absorber. To accomplish this goal, a novel mechanochemical carbonitriding technique is designed. Carbonitriding FeCoNiCu HEAs with flake-like morphology is successfully prepared by a mechanochemical method using the cyano-compound (melamine, C3H6N6) and metal powders as raw materials. Through the investigation of phase structure, magnetic properties, corrosion resistance, oxidation resistance and EMA performances of the samples, it can be found that the carbonitriding process optimizes the high-frequency electromagnetic matching of HEAs, and realizes excellent EMA performances. With the introduction of melamine, S003 (FeCoNiCuM0.03) sample has a reflection loss of −55.8 dB with an effective absorption bandwidth (EAB) of 3.82 GHz, and S006 (FeCoNiCuM0.06) sample achieves a strong absorption of −61.8 dB. In addition, the carbonitriding FeCoNiCu HEAs exhibit excellent corrosion resistance and mechanical hardness. This work not only demonstrates the potential of carbonitriding HEAs for EMA applications, but also provides a new concept for optimizing the electromagnetic impedance matching of HEAs.

Plentiful heterogeneous interfaces coupling in hydrangea-like NiMn-LDH decorated MXene hybrids for enhancing electromagnetic wave absorption

Exploring high-performance electromagnetic wave (EMW) absorption materials holds extraordinary potential for new-generation wireless communication and integrated electronics. Herein, a series of heterogeneous hydrangea-like NiMn-layered double hydroxide (NiMn-LDH)/MXene (denoted as NMM) hybrids were successfully synthesized by facile hydrothermal method and followed electrostatic self-assembly strategy. The EMW absorption performance of NMM hybrids could be flexibly tuned by regulating the ratios of NiMn-LDH to MXene. Benefiting from the synergy of unique structural design and various EMW attenuation mechanisms, the resultant NMM hybrids realize excellent EMW absorption performance. The NMM3 hybrid (the ratio of NiMn-LDH to MXene is 1:1) achieves an optimal reflection loss of −47.7 dB at 13.29 GHz with a thickness of 1.68 mm and a broad effective absorption bandwidth of 4.4 GHz (13.6–18.0 GHz) at a tiny thickness of 1.43 mm. Moreover, the radar cross section simulation is used to intuitively reveal the effectiveness of NMM hybrids as high-performance EMW absorption materials in actual application. This work provides an innovative perspective on the controllable design of highly efficient EMW absorption materials with remarkably practical application value.

Mechanical properties and electromagnetic wave absorption characteristics of solid waste low-carbon cementitious materials

A low-carbon multi-functional cement substitute material has been developed to reduce electromagnetic pollution in building spaces and protect human health. The solid waste electromagnetic absorption cementitious material (SWEACM) is produced by combining steel slag (SS), blast furnace slag (BFS), and phosphogypsum (PG). In this study, the properties of SWEACM were analyzed, including flow, electromagnetic wave absorption, strength, and environmental properties. Additionally, the hydration and electromagnetic wave absorption mechanisms were examined. The results indicate that SS, BFS, and PG content significantly affect the strength and electromagnetic wave absorption properties of SWEACM. S-6 exhibits the best overall performance (SS: BFS: PG = 3:6:1), with the highest strength (28 days compressive strength = 33.5 MPa) and fluidity (19.1 cm). Furthermore, it has excellent electromagnetic absorption performance (RLmin = −45.4 dB), with an adequate absorption bandwidth of up to 10 GHz in the 2–18 GHz range. The excellent electromagnetic wave absorption capability of SWEACM is mainly due to the resonance, polarization relaxation loss, and conduction loss of the magnetic and conductive components in the material. The results show that SWEACM can be used as a multi-functional construction engineering material for electromagnetic protection, combining high levels of high electromagnetic wave absorption, strength performance, and environmental benefits.

A Novel Nano-Laminated GdB2C2 with Excellent Electromagnetic Wave Absorption Performance and Ultra-High-Temperature Thermostability.

A novel nano-laminated GdB2C2 material was successfully synthesized using GdH2, B4C, and C via an in situ solid-state reaction approach for the first time. The formation process of GdB2C2 was revealed based on the microstructure and phase evolution investigation. Purity of 96.4 wt.% GdB2C2 was obtained at a low temperature of 1500 °C, while a nearly fully pure GdB2C2 could be obtained at a temperature over 1700 °C. The as-obtained GdB2C2 presented excellent thermal stability at a high temperature of 2100 °C in Ar atmosphere due to the stable framework formed by the high-covalence four-member and eight-member B-C rings in GdB2C2. The GdB2C2 material synthesized at 1500 °C demonstrated a remarkably low minimum reflection loss (RLmin) of -47.01 dB (3.44 mm) and a broad effective absorption bandwidth (EAB) of 1.76 GHz. The possible electromagnetic wave absorption (EMWA) mechanism could be ascribed to the nano-laminated structure and appropriate electrical conductivity, which facilitated good impedance matching, remarkable conduction loss, and interfacial polarization, along with the reflection and scattering of electromagnetic waves at multiple interfaces. The GdB2C2, with excellent EMWA performance as well as remarkable ultra-high-temperature thermal stability, could be a promising candidate for the application of EMWA materials in extreme ultra-high temperatures.

Constructing Built-In Electric Fields with Semiconductor Junctions and Schottky Junctions Based on Mo–MXene/Mo–Metal Sulfides for Electromagnetic Response

HighlightsMo–MXene/Mo–metal sulfides with semiconductor junctions and Mott–Schottky junctions are designed.Built-in electric field are constructed in semiconductor–semiconductor–metal heterostructure, enhancing dielectric polarization and impedance matching.Density functional theory calculations and Radar cross-section simulations confirmed the excellent electromagnetic wave absorption ability of heterostructures.

Biomimetic Leaf-Vein Aerogel for Electromagnetic Wave Absorption and Thermal Superinsulation.

Electromagnetic protection in extreme environments requires materials with excellent thermal insulation capability and mechanical property to withstand severe temperature fluctuations and complex external stresses. Achieving strong electromagnetic wave absorption (EMA) while sustaining these exceptional properties remains a significant challenge. Herein, a facile approach is demonstrated to fabricate a biomimetic leaf-vein MXene/CNTs/PI (MCP) aerogel with parallel venations through bidirectional freeze-casting method. Due to its multi-arch lamellar structure and parallel venations within the aerogel layers, the ultralight MCP aerogel (16.9 mg·cm-3) achieves a minimum reflection loss (RLmin) of -75.8dB and a maximum effective absorption bandwidth (EABmax) of 7.14GHz with an absorber content of only 2.4wt%, which also exhibits superelasticity and structural stability over a wide temperature range from -196 to 400°C. Moreover, this unique structure facilitates rapid heat dissipation within the layers, while significantly impeding heat transfer between adjacent layers, achieving an ultralow thermal conductivity of 15.3 mW·m-1·K-1 for thermal superinsulation. The combination of excellent EMA performance, robust structural stability, and thermal superinsulation provides a potential design scheme under extreme conditions, especially in aerospace applications.

Poorly-/well-dispersed Fe3O4: Abnormal influence on electromagnetic wave absorption behavior of high-mechanical performance polyurea

In this work, novel core–shell Fe3O4 nanoparticles were prepared by self- assembly technology using phytate-melamine aggregates (PM) or phytate-melamine-Fe3+ aggregates (PM-Fe) as building block. A polyurea (PUA) matrix was filled with magnetic nanoparticle. The influence of Fe3O4, Fe3O4@PM or Fe3O4@PM-Fe content and dispersion on the mechanical and electromagnetic wave (EMW) absorption properties of PUA composite were investigated. Good dispersion of modified Fe3O4 in PUA matrix was obtained. Loading well-dispersed Fe3O4 significantly enhanced the mechanical properties of their PUA nanocomposite under quasi-static tensile, nanoindentation, and dynamic compression tests. Excellent EMW absorption performance of PUA/Fe3O4@PM nanocomposite was desired. Although well-dispersed Fe3O4@PM could effectively enhance the mechanical properties, nonetheless it surprisingly plays a negative role in the EMW absorption performance. The Fe3O4@PM with high dispersion and interfacial compatibility in the PUA matrix was detrimental to EMW absorption performance, which contradicts the well accepted EMW absorption mechanisms. A novel mechanism and model were suggested, along with a fresh understanding of the role of Fe3O4 in the EMW absorption of PUA composite. Furthermore, the Fe3O4@PM-Fe, obtained by constructing a conductive network on the surface of Fe3O4@PM, was used to investigate this assumption. The radar cross section simulation also demonstrated the superior EMW attenuation capability of PUA nanocomposites in the service condition. This work is beneficial to the development of EMW absorber, not limited to Fe3O4 magnetic nanoparticles.

Regulating microstructure and composition by carbonizing in-situ grown metal-organic frameworks on cotton fabrics for boosting electromagnetic wave absorption

High-temperature carbonized metal-organic frameworks (MOFs) derivatives have demonstrated their superiority for promising electromagnetic wave (EMW) absorbers, but they still suffer from limited EMW absorption capacity and narrow bandwidth. Considering the advantage of microstructure and chemical composition regulation for the design of EMW absorber, hierarchical heterostructured MoS2/CoS2-Co3O4@cabonized cotton fabric (CF) (MCC@CCF) is prepared by growing ZIF-67 MOFs onto CF surface, chemical etching, and carbonization. Aside from the dual loss mechanism of magnetic-dielectric multicomponent carbonized MOFs, chemical etching and carbonization process can effectively introduce abundant micro-gap structure that can result in better impedance matching and stronger absorption capacity via internal reflection, doped heteroatoms (Mo, N, S) to supply additional dipolar polarization loss, and numerous heterointerfaces among MoS2, CoS2, Co3O4, and CCF that produce promoted conduction loss and interfacial polarization loss. Thus, a minimal reflection loss of −52.87 dB and a broadest effective absorption bandwidth of 6.88 GHz were achieved via tunning the sample thickness and filler loading, showing excellent EMW absorption performances. This research is of great value for guiding the research on MOFs derivatives based EMW absorbing materials.

Two-dimensional multilayer MnFe2O4/MXene composites with excellent electromagnetic wave absorption effect

The study of building materials with electromagnetic wave absorbing properties to minimize electromagnetic wave interference and enhance communication and efficiency while ensuring a cleaner, healthier, and sustainable future has gained significant attention. The traditional MnFe2O4 material, known for its strong magnetic loss, has been widely used in the field of absorbing electromagnetic waves. However, its lower dielectric loss has hindered further development in this area.In this study, we aimed to design two-dimensional multilayer MnFe2O4/MXene composites using a hydrothermal method to enhance electromagnetic wave absorption. By reducing the particle size, we were able to increase the electromagnetic wave absorption capability of MnFe2O4. The pure MnFe2O4 material achieved a minimum reflection loss (RLmin) value of -40.5 dB at a thickness of 2.85 mm when the hydrothermal temperature was set at 110 °C.To further enhance the dielectric loss of MnFe2O4, we introduced high-surface-area MXene into the composite. The optimal RLmin value of the MnFe2O4/MXene composites reached -49.5 dB at a thickness of 3.55 mm, surpassing the performance of individual MnFe2O4 and MXene materials. This enhanced attenuation of electromagnetic wave absorption can be attributed to the coupling effect between MnFe2O4 and MXene, which promotes coupling mechanisms, interface polarization, and impedance matching.

The hollow cubic octahedral structure of Fe3O4 with excellent electromagnetic wave absorption capacity

The unique nanostructure combined with high dielectric and magnetic losses is essential for electromagnetic wave (EMW) attenuation in microwave-absorbing materials (MAM). In this paper, using cubic octahedral Cu2O as a template, we synthesized hollow cubic octahedral Fe(OH)3 at first. After annealing at 450 °C, the hollow cubic octahedral structure Fe3O4 could be obtained. When the filling ratio was 40 %, the minimum reflection loss (RLmin) reached -66.08 dB, and the maximum effective absorption bandwidth (EAB) was 5.38 GHz at a thickness of 1.84 mm, exhibiting improved EMW properties compared with previous works. The hollow cubic octahedral structure of Fe3O4 enhances EMW absorption characteristics, which is attributed to abundant dipole polarization, interface polarization, and good conduction loss. These results indicate that Fe3O4 with the hollow cubic octahedral structure can be used as potential candidates for efficient and broadband EMW absorbers.

Cauliflower-like Sb2S3@graphene oxide composite with excellent electromagnetic wave absorption capacity

In this paper, a cauliflower-like Sb2S3@graphene oxide (C-Sb2S3@GO) composite was successfully synthesized using hydrothermal and calcination methods. When the calcination temperature was 550 °C, the filling ratio was 30%, the dosage of PVP was 1.6 g, the maximum effective absorption bandwidth (EAB) was 6.24 GHz at a thickness of 1.65 mm, and the minimum reflection loss (RLmin) reached -61.01 dB (2.15 mm). The experimental results exhibit excellent electromagnetic wave (EMW) properties. The cauliflower-like structure has more microscopic and nanolevel features, which are conducive to multiple reflections and scattering of EMWs. In addition, the combination of C-Sb2S3 with GO imparts rich dipole polarization and interface polarization. These results indicate that the C-Sb2S3@GO composite can be used as a potential candidate for use in efficient and broadband EMW absorbers.

Rice straw-inspired tunable multi-hollow channel parallel carbon fibers for enhanced electromagnetic wave absorption

The pure carbon materials are constrained in practical applications due to their inability to meet the requirements of broadband and strong absorption. To address this challenge, inspired by the parallel connection structure of hollow straw, this study successfully fabricated a multi-hollow channel parallel carbon fibers (MHCFs) structure by electrospinning and carbonization template methods. Compared with the traditional non-porous carbon fibers (CFs) structure (MHCFs-0), MHCFs-0.2 exhibit more excellent electromagnetic wave (EMW) absorption performance. It exhibits an impressive 5.59 GHz effective absorption bandwidth (EAB) at 1.8 mm. The reflection loss (RL) of MHCFs-1 reaches −52.64 dB. This remarkable enhancement in performance can be attributed to the channel structure, which can effectively introduce air, optimize impedance matching, and greatly promote polarization effects (including interface polarization and dipole polarization). It is worth noting that the integration of computer simulation technology (CST) with material structure design in this study opens up new ideas for the preparation of absorbing materials and the design of micro-nano structures, holding significant practical implications.