Electromagnetic Wave Absorption Ability Research Articles

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.

Multifunctional design of hierarchical corrugated metamaterial absorber realized by carbon fiber stitching

Carbon fiber (CF) which has both mechanical and electromagnetic (EM) characteristics can achieve multiple functions by special designing, such as load bearing and EM wave absorption. In this work, based on the excellent mechanical properties of hierarchical corrugated sandwich structure (HCSS), a novel CF interlaminar reinforced hierarchical corrugated metamaterial absorber (HCMMA) is constructed. By stitching CF arrays onto the core member face of HCSS, the spoof surface plasmon polaritons (SSPPs) structure is constructed, endowing HCSS with EM wave absorption ability and enhancing its interlaminar mechanical properties. Simulation and experimental results show that the proposed structure achieves efficient absorption (average over 90 %) of 4 - 12 GHz EM wave with an incident angle of 0 - 60°, which realized by the dielectric loss of EM wave and local strong E-filed formed by SSPPs structure. In addition, the stitching of CF arrays effectively limit the local buckling-debonding deformation region of the core member face, which greatly improves its mechanical performances. Thereby the compressive strength and specific compressive strength of the proposed structure is increased by 32.7 % and 16.7 %, respectively. Based on the multifunctional design characteristics of CF, the proposed structure effectively expands the application of composite sandwich structures in the field of multifunctional design.

Porous CoZn@NC skeletons supported NiCo2S4 nanorods for efficient electromagnetic wave absorption

Bimetallic sulfides are promising in electromagnetic wave (EMW) absorption due to their moderate permittivity and high dielectric loss. However, the impedance mismatching and insufficient loss mechanism of bimetallic sulfides result in limited EMW absorption performance. Herein, bimetallic sulfide (NiCo2S4) nanorods were loaded onto nitrogen-doped carbon embedded with CoZn nanoparticles (CoZn@NC) derived from CoZn-based metal organic framework (CoZn-MOF) through simple hydrothermal and vulcanization processes. Importantly, during the vulcanization process, CoZn@NC undergoes structural reorganization and evolves into defect-rich porous nanosheets, which promotes dipole polarization and enhance EMW absorption ability. Additionally, the formed NiCo2S4 nanorods are tightly anchored on the porous CoZn@NC skeletons, forming a large number of heterostructures, and promoting interfacial polarization. In addition, the carbon nanotubes (CNTs) formed during the pyrolysis process of CoZn-MOF contribute to the conduction loss of the heterostructure and motivate dielectric loss. Therefore, CoZn@NC/NiCo2S4 heterostructures inherit excellent EMW absorption performance and obtain a reflection loss (RL) value of −32.53 dB at a matching thickness of 2.1 mm, while exhibiting an effective absorption bandwidth (EAB) of 4.1 GHz. Radar cross-sectional area (RCS) simulation shows that the potential of CoZn@NC/NiCo2S4 heterostructure in practical anti radar detection. This work puts up great potential for the development of advanced bimetallic sulfides-based EMW absorbers.

Regulating the electromagnetic balance of materials by electron transfer for enhanced electromagnetic wave absorption

The fact that single dielectric loss materials have disadvantages of excessive conductivities and impedance mismatches has given rise to a large effort to develop effective strategies to fabricate electromagnetic wave (EMW) absorbing materials comprised of components that bring about a balance between dielectric loss and magnetic loss. Moreover, little is known about the essential features that regulate EMW absorption propensities. This study focused on the development of a new EMW absorbing material and gaining information about factors that govern EMW absorption abilities. The materials at the center of the effort are light weight and porous cobalt sulfonated phthalocyanine-reduced graphene oxide (CoSPc-rGO) aerogels that were synthesized by using a simple hydrothermal method followed by freeze-drying. The properties of these materials that contribute to the electromagnetic balance between dielectric and magnetic loss were elucidated by first formulating a reasonable hypothesis about how the relative orientation of the components in CoSPc-rGO govern p-conjugation and electron transfer from rGO to CoSPc, which is proposed to be a key factor contributing to the regulation of the electromagnetic balance. Polarization relaxation process of materials was analyzed in detail using a variety of approaches including theoretical calculation, spectroscopic measurements, and experimental and simulation studies. The fabricated CoSPc-rGO aerogels that contain an ultra-low content of 4 % were found to exhibit an extraordinary microwave absorption performance associated with a strong reflection loss of -53.23 dB and a broad effective absorption bandwidth of 8.04 GHz. The results of this study should provide an effective guide for new designs of composite materials for EMW absorption.

Preparation and performance of a bamboo-based electromagnetic wave absorber by interfacial polymerization of graphene oxide/polyaniline

Excellent electromagnetic wave absorption ability and effective absorption bandwidth have been the development direction of electromagnetic wave absorbing materials. In this paper, a rational structural design is proposed. Graphene oxide (GO)/polyaniline (PANI) layer was formed on the surface of the natural material bamboo powder (BP) by an interfacial polymerization process. The combination of GO and PANI improves the impedance mismatch of the conductive polymer PANI. Enhanced dielectric storage and loss capability of the composite GO/PANI/BP. The addition of BP brings more electromagnetic wave loss channels to the composite GO/PANI/BP. This unique structure facilitates the construction of a three-dimensional electromagnetic wave-reflecting cavity, which improves the absorptive capacity of the composite by introducing effective multiple reflections. The conductivity of GO/PANI/BP was 1.78 (±0.06) S/cm. When filled to 30 wt%, a minimum reflection loss (RLmin) of −44 dB at 9.36 GHz and a thickness of 3 mm, and an effective absorption bandwidth (<-10 dB) of up to 5.36 GHz in the frequency range 12.64–18 GHz and at a thickness of 2 mm. Exhibits superior loss capability compared to most previous PANI-based electromagnetic wave absorbing materials. In addition, the design structure of this three-dimensional electromagnetic wave reflecting cavity can provide inspiration for the design of other electromagnetic wave absorbing materials and expands the candidate range of green and efficient electromagnetic wave absorbers.

Polyimide-based porous carbon and cobalt nanoparticle composites as high-performance electromagnetic wave absorbers.

This study successfully utilized a straightforward approach, choosing liquid-liquid phase separation to build a porous structure and synthesize composite absorbers based on polyimide-based porous carbon and cobalt nanoparticles (designated as PPC/Co-700 and PPC/Co-800). A fine porous structure was achieved as a result of the excellent heat resistance of polyimide resulting in an excellent electromagnetic wave absorption ability of PPC/Co composites. The results obtained clearly indicated that PPC/Co-700 and PPC/Co-800 exhibit a porous structure with coral-like pores, enhancing both impedance matching properties and microwave attenuation abilities. This improvement in impedance matching conditions and dissipation capability is attributed to the synergistic effect of dielectric loss induced by carbon and magnetic loss induced by Co nanoparticles. PPC/Co-700 showed the strongest absorption performance with a minimum reflection loss of -59.85 dB (30 wt% loading, thickness of 3.42 mm) and an effective absorption bandwidth (EABW, RL ≤ -10 dB) of 6.24 GHz (30 wt% loading, thickness of 2.78 mm). Therefore, this work provides a facile strategy for the development of a promising absorbing material with outstanding electromagnetic wave absorption performance.

Featuring heterogeneous composite of W-type hexagonal ferrite with 2D vanadium carbide MXene for wideband microwave absorption

In this study, W-type hexagonal ferrite BaCo1.2Zn0.8Fe16O27 (BCZF) was synthesized via solid-state sintering and V2CTx-MXene was chemically etched from its V2AlC MAX phase. Subsequently, BCZF and V2CTx composites were synthesized by hydrothermal integration of V2CTx on the surface of BCZF bonded by electrostatic forces at varying mass ratios. The extensive heterostructure interfacial morphology of two dimensional V2CTx and BCZF plays an explicit role in tuning the dielectric and magnetic loss characteristics of the synthesized composites. The dielectric-magnetic synergistic loss mechanism caused by interfacial polarization, strong multi-reflections, scattering between MXene multilayer structures, conduction loss, and magnetic resonance effectively optimized impedance matching to improve the attenuation ability of the synthesized composites. Remarkably, the BCZF@10%V2CTx composite achieved strong electromagnetic wave absorption ability with an effective absorption bandwidth (RL < −10 dB) of 8.0 GHz (10–18 GHz) which is superior to that of contemporary magnetic–dielectric hybrid composites. These results present a novel perspective on magnetic V2CTx-MXene composites for microwave absorption applications, and provide a basis for the design and development of high-performance cloaking materials.

Compressible and conductive multi-scale composite aerogel elastomers for electromagnetic wave absorption, energy harvesting, and piezoresistive sensing

With the rapid development of electronic technology, wearable electronic devices have been widely used in the lives of people. However, integrating multiple functions, such as flexible sensing and electromagnetic protection, into a single device remains challenging. Herein, silver nanowires and cobalt-nickel@carbon were assembled into a conductive and magnetic composite aerogel enhanced by aramid nanofibers and cellulose nanofibrils by freeze-drying. It exhibited an excellent electromagnetic wave absorption ability with an optimal minimum reflection loss of −51.6 dB. Then, polydimethylsiloxane (PDMS) was introduced in the subsequent vacuum-assisted impregnation process to obtain a compressible aerogel elastomer with excellent mechanical and electrical properties. It was not only used as a piezoresistive sensor for different application scenes (e.g., human behavior monitoring, pressure array identification, and parking location recognition) but also as a triboelectric nanogenerator for high-performance energy harvesting. Such a unique and multifunctional composite aerogel elastomer will open up new potential applications for electromagnetic protection, blue energy harvesting, and piezoresistive sensing.

Porous Structure Inherited from Pine Wood and Stacking Defects Synergistically Enhancing Electromagnetic Wave Absorption of SiC

AbstractThe traditional electromagnetic (EM) absorbing materials suffers from the poor performance and instability at high temperature, greatly hindering their wide application. Herein, pine wood‐derived SiC with porous structure and plentiful defect sites was synthesized by carbonization and subsequent chemical vapor infiltration process. The influence of drying pretreatment way (freeze drying vs thermostatic drying), carbonization temperature and Si powder/carbon ratio on structure and electromagnetic (EM) wave absorption performance were studied in detail. The optimized SiC with plentiful pore structure and numerous stacking faults showed superior EM wave absorption abilities with a minimum RL value of −42 dB and the effective bandwidth of 14.4 GHz (3.6–18 GHz). The synergistic effect between porous structure inherited from pine wood and stacking faults distinctly enhanced EM wave absorbing performance of SiC. This work demonstrate that rationally design of biomass‐derived SiC material is a promising way of developing high performance absorber.

The dielectric properties of polymer derived silicon oxycarbonitride film incorporated with TiO2 for electromagnetic wave absorption

The polysilazane preceramic precursor is applied as a coating on ceramic substrates and pyrolyzed at different temperatures to form a silicon oxycarbonitride ceramic film for its dielectric properties in the low-frequency range of 1–8 MHz. Additionally, the porous ceramic hollow matrix filled with the polysilazane preceramic precursor is pyrolyzed for dielectric measurement in the high-frequency range of 1–19 GHz. The results indicate that coating Al2O3 substrates with SiCNO reduces the absorption effect as the pyrolytic temperatures increase. Conversely, coating AlN substrates with SiCNO exhibits the opposite absorption effect. Incorporating titanium dioxide with SiCNO reduces the wave absorption effect within the temperature range of 700 °C–1100 °C. The loss tangent and electromagnetic wave loss of the porous ceramic hollow matrix filled with SiCNO are 4.06 × 10−2 and 4.41 × 10−2, respectively in the high-frequency range. These findings indicate the electromagnetic wave absorption ability of SiCNO composite.

A control strategy for microwave absorption performance on a two-dimensional scale

Two-dimensional (2D) zeolitic imidazolate frameworks (ZIFs) are promising materials for microwave absorption for their desirable features. However, there has been a lack of a corresponding relationship between the growth pattern of 2D ZIF materials at the micro-scale and the macroscopic microwave absorption performance. This work synthesized 2D ZIF-L and its derivatives via a precise structural regulation strategy. By changing the axial orientation of crystal growth, the synthesis of two-dimensional bladed and rod-shaped precursors with controllable thickness and varying shapes at the macro scale was controlled. The leaf-like structure of ZIF-L derivates with large surface area is beneficial for the exposure of reactive oxygen vacancies, increasing the relaxation loss. While the ultra-thin rod-shaped structure which can shorten the electron migration and jump paths to reduce the energy barrier is advantageous to conductive loss. As a result, the prepared L-7 exhibits superior electromagnetic wave absorption ability with the widest effective absorption bandwidth (EAB) of 5.53 GHz at a thickness of 1.80 mm. When the total thickness is 1.90 mm, R-7 can exhibit the minimum reflection loss (RLmin) value of about −60.40 dB. This study emphasizes the 2D scale regulation for obtaining new generation and environmentally friendly microwave absorbers. Metal-based materials derived from ZIF-L with extremely thin thicknesses and a large surface area have shown great potential in microwave absorbers.

Functional Tailoring of Multi-Dimensional Pure MXene Nanostructures for Significantly Accelerated Electromagnetic Wave Absorption.

Transition metal carbide (Ti3 C2 Tx MXene), with a large specific surface area and abundant surface functional groups, is a promising candidate in the family of electromagnetic wave (EMW) absorption. However, the high conductivity of MXene limits its EMW absorption ability, so it remains a challenge to obtain outstanding EMW attenuation ability in pure MXene. Herein, by integrating HF etching, KOH shearing, and high-temperature molten salt strategies, layered MXene (L-MXene), network-like MXene nanoribbons (N-MXene NRs), porous MXene monolayer (P-MXene ML), and porous MXene layer (P-MXene L) are rationally constructed with favorable microstructures and surface states for EMW absorption. HF, KOH, and KCl/LiCl are used to functionalize MXene to tune its microstructure and surface state (F- , OH- , and Cl- terminals), thereby improving the EMW absorption capacity of MXene-based nanostructures. Impressively, with the unique structure, proper electrical conductivity, large specific surface area, and abundant porous defects, MXene-based nanostructures achieve good impedance matching, dipole polarization, and conduction loss, thus inheriting excellent EMW absorption performance. Consequently, L-MXene, N-MXene NRs, P-MXene ML, and P-MXene L enable a reflection loss (RL ) value of -43.14, -63.01, -60.45, and -56.50dB with a matching thickness of 0.95, 1.51, 3.83, and 4.65mm, respectively.

N-S co-doping lignin-based carbon magnetic nanoparticles as high performance supercapacitor and electromagnetic wave absorber

Recently, multifunctional lignin-based materials are gaining more and more attention due to their great potential for low-cost and sustainability. In this work, to obtain both an excellent supercapacitor electrode and an outstanding electromagnetic wave (EMW) absorber, a series of multifunctional nitrogen-sulphur (N-S) co-doped lignin-based carbon magnetic nanoparticles (LCMNPs) had been successfully prepared through Mannich reaction at different carbonization temperature. As compared with the directly carbonized lignin carbon (LC), LCMNPs had more nano-size structure and higher specific surface area. Meanwhile, with the increase of carbonization temperature, the graphitization of the LCMNPs could also be effectively improved. Therefore, LCMNPs-800 displayed the best performance advantages. For the electric double layer capacitor (EDLC), the optimal specific capacitance of LCMNPs-800 reached 154.2 F/g, and the capacitance retention after 5000 cycles was as high as 98.14 %. When the power density was 2204.76 W/kg, the energy density achieved 33.81 Wh/kg. In addition, N-S co-doped LCMNPs also exhibited strong electromagnetic wave absorption (EMWA) ability, whose the minimum reflection loss (RL) value of LCMNPs-800 was realized −46.61 dB at 6.01 GHz with an thickness of 4.0 mm, and the effective absorption bandwidth (EAB) was up to 2.11 GHz ranging from 5.10 to 7.21 GHz, which could cover the C-band. Overall, this green and sustainable approach is a promising strategy for the preparation of high-performance multifunctional lignin-based materials.

Heterogeneous interface engineering of high-density MOFs-derived Co nanoparticles anchored on N-doped RGO toward wide-frequency electromagnetic wave absorption

Facing increasing electromagnetic (EM) wave pollution and interference issues, developing synergy EM wave absorption materials with rich heterogeneous interfaces is s an effective way to solve the above problems. In this work, two-dimensional (2D) cobalt-based metal-organic frameworks (Co-MOFs) nanosheets arrays are firstly growth on the 2D graphene oxide (GO) sheets. After undergoing the pyrolytic treatment in the N2 atmosphere, high-density MOFs-derived 0D Co nanoparticles (NPs) uniformly anchored on the Nitrogen-doped reduced graphene oxide (N-RGO), constructing 0D/2D magnetic-dielectric Co@N-RGO composites. By tuning the size of magnetic Co NPs by controlling the content of Co-MOFs nanosheets, the EM parameters and impedance match of Co@N-RGO sheets can be regulated to tune the EM wave absorption ability. Benefited from the synergy loss and high-density heterogeneous interfaces, obtained Co@N-RGO sheets exhibit excellent EM wave absorption intensity and tuning absorption frequency. The effective absorption bandwidth of the Co@N-RGO sheets ups to 6.0 GHz at 1.9 mm thickness, covering the entire Ku band (12–18 GHz). It can be concluded that constructing magnetic-dielectric system and high-density heterogeneous interfaces provides a new guide to obtain wide-frequency EM wave absorption materials.

Porous Fe/FeO/Fe2O3 nanorod/RGO composites with high-efficiency electromagnetic wave absorption property

Electromagnetic wave absorbers composed of reduced graphene oxide (RGO) and magnetic nanoparticles integrates dielectric and magnetic loss features, which is extremely desirable for enhancing electromagnetic wave absorption ability. Here, porous Fe/FeO/Fe2O3 nanorods/RGO composites (FFORGO) are synthesized via anchoring FeO(OH) nanorods on graphene oxide (GO) through dopamine polymerization followed by thermal reduction treatment. The porous Fe/FeO/Fe2O3 nanorods are anchored on RGO, and crosslinked structure formed in FFORGO composites when the GO addition is higher than 5 mg‧ml−1. The abundant active sites (e.g., functional groups, dangling bonds, and lattice defects), the numerous heterointerfaces (among Fe, FeO, Fe2O3 and RGO) and crosslinked structure trigger multiple dipole polarization, interface polarization and enhanced conductive loss. The EM wave absorption property is optimized by tuning the GO addition. FORGO4 with filler loading of 30 wt% achieves the maximal reflection loss of −24.1 dB at a thickness of 1.9 mm and the effective bandwidth below −10 dB of 3.01 GHz with a thickness of 2.2 mm, owing to the proper ratio of Fe/FeO/Fe2O3 nanorods/RGO and synergistic effect between dielectric loss (dipole polarization, interface polarization, conductive loss) and magnetic loss (eddy current loss and exchange resonance). With the filler loading of 35 wt%, the maximal reflection loss of FFORGO4 is −50.7 dB at a thickness of 1.7 mm and the effective bandwidth reaches to 3.74 GHz at a thickness of 1.8 mm.

Controlled-etching assisted fabrication of yolk–shell Co/C nanocubes with dual loss mechanisms to improve electromagnetic wave absorption abilities

Rational design and fabrication of yolk–shell structure is evolving as an effective approach to improve electromagnetic wave absorption performance by enhancing the impedance matching, multiple reflections and scatterings, as well as promoting interfacial polarizations. However, due to the complexity of synthesis, it is still challenging to develop an absorber with yolk–shell structures intergrating two types of losses (dielectric and magnetic loss) simultaneously in the yolk and shell. Herein, novel yolk–shell Co/C nanocubes were successfully constructed via a controlled-etching with tannic acid followed by direct pyrolysis, in which the magnetic component Co and dielectric component C were uniformly distributed in the yolk as well as the shell. It was found that the pyrolysis temperature can adjust the graphitization degree of carbon and the crystallinity of metal Co, which effectively regulated the electromagnetic properties of the YS-Co/C nanocubes. The reflection loss was − 57.34 dB by increasing the pyrolysis temperature to 700 ℃ under a frequency of 11.76 GHz. The corresponding effective absorption bandwidth was 5.6 GHz (9.52–15.12 GHz) at a thickness of only 2.5 mm. The findings obtained from this study lay a solid foundation for novel design of yolk–shell absorbers applied in EMW absorption.

Magnetic fly ash@carbon microspheres for high-performance electromagnetic wave absorption

Magnetic fly ash (MFA) solid waste used as electromagnetic wave (EMW) absorbers has attracted considerable attention, due to its easy recovery, stable physicochemical property, and magnetic property. However, the single loss mechanism and narrow absorption frequency band of magnetic absorption materials, limit the improvement of absorption performance. In this study, MFA@carbon (MFA@C) microspheres with tunable microstructure are directly synthesized, by adjusting the heart treatment temperature of chemical vapor deposition process. The optimization of the absorption properties is realized, and the absorption mechanism of the MFA@C microspheres is analyzed and discussed. In addition, the optimal reaction temperature of the MFA@C microspheres is 700 °C. When the thickness is 2.9 mm, the reflection loss of the MFA@C microspheres is up to −49.6 dB, and the effective absorption bandwidth is 4.6 GHz. The results show that the excellent EMW absorption ability of the MFA@C microspheres is attributed to the synergistic absorption of carbon and MFA. The unique cluster structure of MFA@C microspheres enhances the multiple reflections and promotes the interfacial polarization.

Morphology modulated defects engineering from MnO2 supported on carbon foam toward excellent electromagnetic wave absorption

Defect engineering exerts a crucial impact on polarization loss and thereby enhances electromagnetic (EM) wave absorption ability. The EM loss mechanism beneath of morphology conversion is usually vaguely considered as the synergism of multiple mechanisms. Morphology induced defects and its dominated polarization loss mechanisms are little focus on. In this work, MnO2/Carbon foam (MCF) composites with tunable morphology were prepared via facile hydrothermal and annealing process. Morphological conversion of MnO2 and its induced defects were achieved by KMnO4 concentration, which contributes to the reduction of conductive loss, optimization of impedance matching, increase of polarization loss and multiple scattering. Therefore, the minimum reflection loss of MCF composite harvests −65.18 dB at 3.19 mm and the broad effective absorption bandwidth covers the entire X band. Despite multiple dissipation mechanisms, the excellent performance is dominated by morphology modulated defects in MCF composites. Besides, the optimal MCF composite displays a high compressive strength of 14.647 MPa. According to the results of computer simulation technology, the MCF composite can attenuate EM energy in the actual condition. This work is expected to offer an inspired understanding of morphology modulated defects toward high-performance of EM wave absorption materials.

Preparation and electromagnetic wave absorption properties of PDC–SiC/Si3N4 composites using selective laser sintering and infiltration technology

Polymer-derived silicon carbide/silicon nitride (PDC–SiC/Si3N4) composites were prepared by additive manufacturing and infiltration technology. The composite green bodies were prepared using selective laser sintering (SLS) three-dimensional (3D) printing technology. Carbon-rich PDC–SiC was generated via precursor infiltration and pyrolysis (PIP) to increase the dielectric constant and enhance the electromagnetic wave (EMW) attenuation ability of the composites. Low-dielectric materials, including Al2O3, TiO2, and AlPO4, were introduced by sol infiltration to improve the impedance-matching characteristics of the composites. The results showed that the EMW absorption ability of the PDC–SiC/Si3N4 composites enhanced after two and four PIP cycles, whereas it degraded with further increasing the PIP cycle number. Among all the samples, the PDC–SiC/Si3N4 composite after four PIP cycles displayed an excellent EMW absorption ability with the minimal reflection loss of −46.79 dB, whereas its effective absorption bandwidth was narrow. Comparing to the sample without infiltration, the effective absorption bandwidth of the samples after the infiltration treatment with TiO2 or Al(H2PO4)3 sol increased from 1.44 GHz to 4.08 GHz and 3.52 GHz, respectively. These results demonstrate that the PIP process and infiltration with TiO2 or Al(H2PO4)3 sol resulted in a 3D-printed PDC–SiC/Si3N4 ceramic that is a promising EMW absorption material suitable for high-temperature environments.

3D flower-like (MoS2/Fe3O4)@rGO nanocomposites with remarkable EMW absorption property

Electromagnetic pollution affects people's health and interferes with the normal operation of large equipment. Herein, a flower-like (MoS2/Fe3O4)@rGO nanocomposite with significant EMW absorption property were synthesized via hydrothermal and chemical precipitation methods. The reasonable combination of magnetic Fe3O4 with rGO and MoS2 optimizes the composite’s electromagnetic parameters and improve the impedance matching. Consequently, the flower-like (MoS2/Fe3O4)@rGO composite has a minimum reflection loss of up to −64.05 dB at 1.83 mm and an effective absorption bandwidth of 7.34 GHz at 2.5 mm. It is believed that the good electromagnetic wave absorption ability of the material originates from the synergistic effect of various loss mechanisms among the different components of MoS2, Fe3O4 and RGO, as well as the magnetic loss induced by Fe3O4.