Minimum Reflection Loss Value Research Articles

Integrated design of multifunctional lightweight magnetic cellulose-based aerogel with 1D/2D/3D hierarchical network for efficient microwave absorption

Developing electromagnetic wave absorption materials that are both multifunctional and high-performance, while using rational dimensional design and component strategies, remains extremely challenging. Herein, multidimensional, gradient porous, electrically, and magnetically conductive carbon nanocellulose aerogels composed of nanocellulose and highly oriented Ni chains are prepared through freeze-drying and subsequent low-temperature annealing. Interestingly, the Ni/CNCA composite achieves exceptional microwave absorption with a minimum reflection loss (RLmin) value of −62.0 dB and a maximum effective absorption bandwidth (EAB) of 6 GHz, covering the entire Ku-band. The superior electromagnetic wave absorption stems from 1D/2D/3D double-supported interpenetrating network with satisfactory impedance matching, dielectric/magnetic losses, interface/dipole polarization, and multiple/reflection scattering. Furthermore, the Ni/CNCA exhibits a low density, excellent mechanical adaptability, hydrophobicity, and corrosion resistance. This work introduces innovative approaches for developing lightweight, multifunctional microwave absorbers for practical applications.

Electrospinning fabrication of hollow C@TiO2/Fe3C nanofibers composites for excellent wave absorption at a low filling content

In order to face the challenge of achieving high-efficiency and lightweight wave absorption materials, we prepared the poly-m-phenylene isophthalamide (PMIA)/TiO2/Fe3C (PTF) composites with hollow structure by coaxial electrospinning and carbonization process. PMIA as the carbon source provided a three-dimensional (3D) conductive network, using TiO2 and Fe3C to improve the impedance matching, reinforce the hollow structure, and increase the absorption mechanism of composites. Significantly, the minimum reflection loss (RLmin) value of optimal material is −58.1 dB at 14.88 GHz and the effective absorption bandwidth (EAB) of 6 GHz with the matching thickness of 2.3 mm, and the filling content is only 13 wt%. The excellent absorption property is maintained even after heating, immersing, and long-term use. This work provides the reference of hollow carbon nanofiber absorbers with excellent comprehensive properties and has more powerful practicability in a variety of environmental conditions.

Fe3O4@CNTs/PANI/PI fabric with magnetic–dielectric nanonetwork as a highly efficient microwave absorber

Since the matching between the complex permittivity and permeability plays a dominant role in the performance of microwave absorbing, magnetic-dielectric materials have been increasingly used for microwave absorption. In this paper, Fe3O4 nanoparticles anchored on carbon nanotubes (Fe3O4@CNTs) were fabricated via a self-assembled technique. The efficient microwave-absorbing fabric was synthesized by building polyaniline nanofibers (PANI NFs) and Fe3O4@CNTs magnetic–dielectric network on the surface of polyimide (PI) fabric. The results of SEM, FTIR, and XRD demonstrated the presence of Fe3O4@CNTs on the fabric surface. The decomposition temperature (Td) of the fabric was beyond 580.0 °C and the fabric exhibited strong hydrophobicity (water contact angle 125.0°). The Fe3O4@CNTs/PANI/PI fabric possessed a minimum reflection loss (RL) value of −62.61dB (>99.9% absorption) with a matching thickness of 1.58 mm. The excellent microwave absorption capacity is attributed to the well impendence match, dielectric and magnetic loss, and the scattering loss of the special cell structure.

“Dual-armor” strategy to prepare multifunctional carbonyl iron particle with corrosion resistance, self-healing and high microwave absorbing performances

As a common and high microwave absorbing material, the application fields of carbonyl iron particle (CIP) are limited because of its poor corrosion resistance when working in harsh environments such as ocean, rainforest, or other high-humidity, high-salt places. Therefore, it is necessary to design a multifunctional CIP with good corrosion resistance and self-healing properties for ensuring its stable microwave absorbing performance. Herein, a “dual-armor” strategy is proposed to prepare multifunctional CIP (Composite particle), which is assembled with CIP coated by polyaniline (PANI/CIP) and Fe-DSe-M. Fe-DSe-M is Fe3+ responsive microcapsule whose shell contains -Se-Se-bonds and is magnetically adsorbed on the surface of PANI/CIP. PANI/CIP and Fe-DSe-M jointly undertake the function of microwave absorbing, anti-corrosion and self-healing. It is worth to note that the microwave absorbing performance of CIP after multi-functionalization has been greatly improved, and the minimum reflection loss value after accelerated corrosion is only reduced by 5.46 dB, which is much lower than PANI/CIP. These excellent properties of functional Composite particle benefit from PANI protective layer, Fe3+ responsive self-healing Fe-DSe-M and their synergistic effect. Our work provides a new approach to fabricate multifunctional microwave absorbing particle, which has a potential application in the corrosive environment.

Glucose derived carbon encapsulated boron nitride core-shell composites for efficient electromagnetic microwave absorption

Hexagonal boron nitride (h-BN) has the advantages of outstanding insulation, high thermal conductivity and excellent chemical stability, which promote the wide application of h-BN in thermal interface electronic packaging and other related fields. However, due to the poor dielectric loss ability of h-BN, which leads to its weak absorption capacity of electromagnetic waves (EMW), so it limits its practical application in related advantageous fields. In this paper, glucose-derived carbon-encapsulated BN core-shell composites (C@BN) were prepared by a simple hydrothermal reaction followed by high-temperature pyrolysis. The dielectric loss capacity of the C@BN was investigated by manipulating the concentration of glucose solution and pyrolysis temperature. Specifically, by adjusting the glucose derived carbon defect to induce polarization loss and impedance matching performance, so that more EMW entering the interior of the composite is absorbed and dissipated. The results show that C@BN obtained at 800 °C shows the best EMW absorption performance when the concentration of glucose solution is 3.6 wt%. The minimum reflection loss value (RLmin) is −43.5 dB and the maximum width effective absorption bandwidth (EABmax) of 6.72 GHz. Therefore, this study provides a reliable reference for the preparation of h-BN based EMW absorbing materials.

Electromagnetic wave absorbing biomass kelp derived porous carbon anchored by Fe3O4 nanocomposites

Increasingly serious electromagnetic pollution problems bring the threaten for national defense security and personal health, biomass carbon materials derived absorbers have arouse widespread interest due to their green, easy accessibility, structural diversity, rich functional groups. Herein, biomass kelp derived three-dimension (3D) porous carbon/Fe3O4 (KPC/Fe3O4) nanocomposites were successfully synthesized vis KOH activation as well as in-situ growth of Fe3O4 and following pyrolysis. Attributed to multiple transmission paths for electromagnetic wave from 3D porous structure, dielectric-magnetic synergistic effect, and numerous defects in the kelp-derived carbon with polarization loss caused by heteroatom doping and interfacial polarization, KPC/Fe3O4 nanocomposites possess outstanding impedance matching and extraordinary attenuation ability. In particular, the minimum reflection loss (RLmin) value of KPC/Fe3O4-0.1 nanocomposite reaches −75.02 dB at 10.5 GHz as well as the effective absorption bandwidth (EAB, RL < -10 dB) value achieves 4.83 GHz with a thickness of 2.85 mm. Unique structures and excellent EWA performance demonstrate that KPC/Fe3O4 nanocomposites can serve as potential absorbers for military and civilian fields.

Screw dislocation growth defects enhancing electromagnetic wave absorption performance of GdB6

In this study, a purity of up to 98.36 wt. % GdB6 with screw dislocation growth morphology were successfully fabricated using an in-situ reaction approach. The terraced-like structure of the GdB6 enhanced the interfacial polarization and multiple interface scattering of the electromagnetic waves. As a result, the as-obtained high purity GdB6 powder presented superior electromagnetic wave absorption performance. The minimum reflection loss value can be −49.24 dB at the frequency of 13.12 GHz with a thin matching thickness of 1.44 mm. In addition, the widest effective absorption bandwidth can be up to ∼4 GHz (14–18 GHz) with a thin matching thickness of 1.25 mm. The remarkable electromagnetic wave absorption performance of GdB6 ceramics could be attributed to conductance loss and polarization loss enhanced by the screw dislocation growth defects, as well as synergistic effects with magnetic loss. The as-obtained GdB6 with synergistic dielectric loss and magnetic loss is to be a novel single-phase with excellent electromagnetic wave absorbing material, which will pave the way on the investigation of rare earth hexaborides for the ultra-high temperature environment applications.

Integrating Sulfur Doping with a Multi-Heterointerface Fe7S8/NiS@C Composite for Wideband Microwave Absorption.

Heterointerface engineering is presently considered a valuable strategy for enhancing the microwave absorption (MA) properties of materials via compositional modification and structural design. In this study, a sulfur-doped multi-interfacial composite (Fe7S8/NiS@C) coated with NiFe-layered double hydroxides (LDHs) is successfully prepared using a hydrothermal method and post-high-temperature vulcanization. When assembled into twisted surfaces, the NiFe-LDH nanosheets exhibit porous morphologies, improving impedance matching, and microwave scattering. Sulfur doping in composites generates heterointerfaces, numerous sulfur vacancies, and lattice defects, which facilitate the polarization process to enhance MA. Owing to the controllable heterointerface design, the unique porous structure induced multiple heterointerfaces, numerous vacancies, and defects, endowing the Fe7S8/NiS@C composite with an enhanced MA capability. In particular, the minimum reflection loss (RLmin) value reached -58.1dB at 15.8GHz at a thickness of 2.1mm, and a broad effective absorption bandwidth (EAB) value of 7.3GHz is achieved at 2.5mm. Therefore, the Fe7S8/NiS@C composite exhibits remarkable potential as a high-efficiency MA material owing to the synergistic effects of the polarization processes, multiple scatterings, porous structures, and impedance matching.

The effects of phase interfaces in SmFeN/YSZ composite thermal barrier materials on electromagnetic wave-absorbing properties

Yttria-stabilized zirconia (YSZ) oxide ceramic powder is a thermal-barrier material used to fabricate thermal barrier coatings (TBC). In this study, to improve the electromagnetic wave (EMW) absorbing properties of TBCs, microwave-absorbing samarium iron nitrogen (SmFeN) particles were used to prepare SmFeN/yttria-stabilized zirconia (YSZ) composites. To study the effect of the SmFeN/YSZ interfaces on the EMW-absorbing properties of the SmFeN/YSZ composite, SmFeN/YSZ interfaces were built in different ways in composite materials having the same mass ratio of 1:1, for example, SmFeN and YSZ particles homogeneously mixed together, SmFeN/YSZ interfaces perpendicular and parallel to the EMW incident direction, and different interfaces between YSZ and SmFeN. Thus, the microwave absorbing performance of the samples, including the electromagnetic parameters, attenuation coefficient, eddy-loss current (C0), impedance matching, and minimum reflection loss (RLmin) values were examined and analyzed. The results demonstrate that interfaces perpendicular to the direction of the EMWs can increase the contact area and enhance the interfacial absorption effect. Further, when the wave-absorbing agent was placed in the middle of the composite, its wave-absorbing effect was the best among all the samples, yielding RLmin = −27.824 dB and effective absorption bandwidth (EAB) = 8.5453 GHz (effective absorption frequency range 7.9256–16.4709 GHz for a 7.2-mm-thick layer). Crucially, the frequency and bandwidth at which the best absorption occurred could be tuned by adjusting the thickness of the coating. This is because the interfaces in the samples resulted in polarization enhancement and anomalous dispersion, leading to large dielectric losses. Overall, the use of a coaxial measurement technique is highly efficient for EMW absorbing body design and process simulations.

Surface engineering strategy for MXene to tailor electromagnetic wave absorption performance

The emerging two-dimensional material, Ti3C2Tx MXene, has attracted significant attention in the realm of electromagnetic wave absorption owing to its exceptional inherent conductivity and distinctive microstructure. However, similar to other conductive materials, MXene encounters the challenge of impedance mismatch, thereby impeding the electromagnetic wave absorption capability in single-component MXene materials. In this study, a molten chlorine-salt method was employed to gain MXene samples with varying surface-chlorine/oxygen (Cl/O) ratios by surface engineering. Notably, among these samples, Cl/Ni-MX-6 exhibited an impressive minimum reflection loss value of −45.72 dB (1.6 mm) and an effective absorption bandwidth of 3.44 GHz (1.3 mm). This study revealed that increasing the etchant content enhances the delamination effect of MXene and leads to adjust Cl/O ratio. Importantly, the modulation of −Cl/O surface functional groups can limit the electronic conductivity, while the number and species of different kinds of surface dipoles will control the polarization effect, ultimately optimizing the electromagnetic wave absorption performance of pure MXene. These insights contribute to ongoing efforts aimed at enhancing the performance of MXene-based materials in the field of electromagnetic wave absorption as well as get a better understanding of the electromagnetic loss mechanism.

(Zn0.6Ni0.3Cr0.1)1.02(Fe2O4)0.98/biocarbon composite: A broad band and highly efficient electromagnetic wave absorber

The combination of carbon and magnetic materials have drawn extensive attention for microwave absorption. In this study, high-performance microwave absorbing materials are prepared by direct mechanical mixing (Zn0.6Ni0.3Cr0.1)1.02(Fe2O4)0.98 (ZnNiCrFeO) with leaf biocarbon. After mixing with biocarbon, the magnetic materials present decent micro-wave reflection loss. Especially, the minimum reflection loss value of −41.08 dB is achieved. The excellent conductivity of biocarbon, magnetic loss of ZnNiCrFeO, and interface polarization loss (between ZnNiCrFeO and biocarbon) jointly determined the electromagnetic absorbing performance. The appropriate impedance matching as well as the synergetic effect between the biocarbon and ZnNiCrFeO magnetic material are also considered. These achievements light the way to prepare low-cost microwave absorbents with excellent electromagnetic wave absorbing performances, utilizing the leaf as precursors.

Enhanced electromagnetic wave absorption of magnetite-spinach derived carbon composite

The high density, high cost, and environmental pollution hinder the application of iron-based electromagnetic wave-absorbing materials. Although bio-carbon is a green and lightweight dielectric wave-absorbing material, the wave-absorbing performance of bio-carbon is still limited. This work successfully combined magnetite Fe3O4 with porous carbon derived from spinach stem using hydrothermal and calcination methods. This process optimizes the matching of the dielectric constant and magnetoconductivity of the as prepared composite material, resulting in a significant improvement in electromagnetic microwave absorption capacity. XRD, SEM, TEM, XPS, VSM and EMW absorption network analyzer are used to detect and characterize the samples. The composite material shows a excellent minimum reflection loss value of −48.81 dB and an efficacious absorption bandwidth of 4.73 GHz at the optimal raw material ratio. The tests also show the porous structure of the sample with the coercivity and saturation magnetization of 29.36 Oe and 10.75 emu/g, respectively. The test results indicate that the excellent electromagnetic wave absorption is due to the synergistic effect of multiple reflection, Debye relaxation, and interfacial polarization. This Fe3O4-bio-carbon composite is cheap and simple to prepare, and it also has excellent wave absorption performance. Therefore, it shows great application potential in civilian and military electromagnetic wave absorption fields.

Cost-effective preparation and high performance of high-temperature electromagnetic wave absorbing materials based on graphene nanosheets

High cost and resistance to harsh working conditions are challenges faced by most microwave absorbers for wide applications. Here, a low-cost graphene-based high-temperature microwave absorbing material is prepared. When the ratio is adjusted appropriately, excellent absorbing performance can be achieved at room temperature: C-2 is the most efficient material with respect to microwave absorption: it has an effective absorption bandwidth as wide as 4.6 GHz, and the minimum reflection is −39.2 dB with a thickness of 1.5 mm. Using the permittivity and TG data of the composites at 800 °C attained, it is demonstrated that the decomposition temperature of composites can be increased from 450° to 820°. When the mass ratio of graphene nanosheets and water glass is 1:2, the composites have the best high-temperature microwave absorption performance: C-2 exhibited the microwave absorption ability with a minimum reflection loss value of approximately −29.6 dB at 16.4 GHz, a thickness of 1.5 mm even at 800 °C.

In Situ Loading of Ni3ZnC0.7 Nanoparticles with Carbon Nanotubes to 3D Melamine Sponge Derived Hollow Carbon Skeleton toward Superior Microwave Absorption and Thermal Resistance.

The simple and low-cost construction of a 3D network structure is an ideal way to prepare high-performance electromagnetic wave (EMW) absorption materials. Herein, a series of carbon skeleton/carbon nanotubes/Ni3ZnC0.7 composites (CS/CNTs/Ni3ZnC0.7) are successfully prepared by in situ growth of Ni3ZnC0.7 and CNTs on 3D melamine sponge carbon. With the increase ofprecursor, Ni3ZnC0.7 nanoparticles nucleate and catalyze the generation of CNTs on the surface of the carbon skeleton. The minimum reflection loss (RL) value of the S60min composite (loading time of 60 min) reaches -86.6dB at 1.6mm and effective absorption bandwidth (EAB, RL≤-10dB) is up to 9.3GHz (8.7-18GHz). The 3D network sponge carbon with layered micro/nanostructure and hollow skeleton promotes multiple reflection and absorption mechanisms of incident EMW. The N-doping and defects can be equivalent to an electric dipole, providing dipole polarization to increase dielectric relaxation. The uniform Ni3ZnC0.7 nanoparticles and CNTs play a key role in dissipating electromagnetic energy, blocking heat transfer, and enhancing the mechanical properties of the skeleton. Fortunately, the composite displays a quite low thermal conductivity of 0.09075Wm·K-1 and good flexibility, which can provide insulation and quickly recover to its original state after being stressed.

In Situ Synthesis of an Epoxy Resin Microwave Absorption Coating with Anti-Ultraviolet Aging Effects

A nanoparticle-anchored three-dimensional microsphere flower-structured layered double hydroxide (LDH) material with Fe3O4 particles was successfully prepared using simple hydrothermal and hot solvent methods. Micro-nanostructured Fe3O4@LDHs (SLF) composites balance microwave absorption, corrosion protection, and UV aging resistance. The minimum reflection loss value of SLF is −35.75 dB at 14.16 GHz, when the absorber thickness is 8 mm, and the absorption bandwidth at this frequency is up to 2.56 GHz for RL values less than −10 dB, while the LL is only 1 GHz. The SLF /EP coating has not only excellent microwave absorption performance but also excellent corrosion and UV aging resistance performance. The coating still has some anti-corrosion effect after 10 d of immersion. This work is intended as a reference for the development of new coatings with excellent microwave absorption properties as well as corrosion and UV aging resistance for wind turbine tower barrels (seaside wind power generation equipment) surfaces.

Design and optimization of double-layer structure for improved electromagnetic wave absorbing characteristic of single-layer foam cement-based materials containing carbon black

Electromagnetic wave (EMW) absorbing properties are increasingly needed in cement-based materials; however, lightweight and broadband absorption properties are challenging to realize. This study aims to create lightweight, broadband, and highly efficient EMW-absorbing materials by investigating a foam cement-based material with single- and double-layer structures containing carbon black (CB). The results revealed that CB significantly affects the mechanical properties and electrical conductivity of foam cement-based materials. The compressive strength of the foam cement-based material containing 1.5 wt% CB with a density of 0.9 g cm−3 can reach 7.0 MPa and has satisfactory workability and conductivity. The dielectric properties of the foam cement-based material can be synergistically controlled by its density and CB content, and obtain favorable electric loss ability. For a single-layer structure, the optimal reflection loss (RL) value of a specimen with 10 mm-thick can reach −29.67 dB with an efficient bandwidth of 0.99 GHz. In contrast, the double-layer structure exhibited remarkable broadband characteristics. When the total thickness of double-layer structure is 10 mm, the optimal two specimens can achieve a minimum RL value of −28.62 and −25.52 dB with a maximum effective bandwidth of 1.49 and 1.87 GHz, respectively. This study proposes single- and double-layer foam cement-based structures with excellent impedance matching and loss attenuation ability, and constructs an effective design method for cement-based materials to achieve lightweight and broadband absorption. In addition, these cement-based materials can be regarded as a new generation of EMW-absorbing materials in the field of construction engineering.

Interface Engineering of Titanium Nitride Nanotube Composites for Excellent Microwave Absorption at Elevated Temperature

HighlightsThe boosted heterogeneous interfaces in titanium nitride (TiN) nanotube/polydimethylsiloxane (PDMS) composite contributed to strong polarization loss relaxation ability.The TiN nanotubes/PDMS composite possessed both good impedance matching behavior and strong dielectric loss ability in wide temperature spectrum.The TiN nanotubes/PDMS composite exhibited excellent EMWA performances (effective absorption bandwidth value of 3.23 GHz and minimum reflection loss value of − 44.15 dB) at the varied temperature from 298 to 573 K.

Enhanced electromagnetic wave absorption in YAG-modified SiC foam

Electromagnetic technology applications are escalating, leading to increased human exposure to electromagnetic radiation. In addressing the challenges posed by this radiation, electromagnetic wave absorbing materials stand out due to their distinguished properties. This study focused on developing porous fibrous SiC three-dimensional (3D) foams. These were synthesized by freeze-drying SiC nanofiber dispersions followed by high-temperature sintering. Measurements demonstrated that the resulting SiC foams possess a relatively low density, approximating 0.1 g cm−3. Upon microscopic analysis, it became evident that the foam's porous structure is predominantly made up of SiC fibers intermixed with yttrium aluminum garnet granules. These tailored SiC foams delivered outstanding electromagnetic wave absorption characteristics, recording a minimum reflection loss value of −63 dB. Furthermore, an expansive effective absorption bandwidth of 6.9 GHz (spanning from 9.3 to 16.2 GHz) was noted for a sample thickness of 3.15 mm. Several factors contribute to this high absorption efficacy, including multiple reflections and both interface and dipole polarizations. It is also worth noting that the SiC foam displayed commendable oxidation resistance when exposed to elevated temperatures. Cumulatively, these findings underscore the promising potential of porous fibrous SiC 3D foams in electromagnetic wave absorption applications, especially in extreme conditions.

Simultaneous manipulation of constituent and structure toward MOFs-derived hollow Co3O4/Co/NC@MXene microspheres via pyrolysis strategy for high-performance microwave absorption

The development of microwave absorbing materials with high performance is one of the effective strategies to solve the increasingly serious electromagnetic pollution problem, and has received the attention of researchers. Herein, the structure and composition manipulation of Ti3C2Tx MXene and MOFs derivatives are investigated. It is found that the TiO2 produced by oxidation of Ti3C2Tx MXene, as a low dielectric material, can effectively solve the impedance mismatch caused by the high conductivity of Ti3C2Tx MXene. Additionally, MOFs derivatives with excellent dielectric-magnetic properties are often obtained by high temperature pyrolysis, which also aids in the oxidation of Ti3C2Tx MXene. Here, we successfully synthesized ZIF-67 nanoparticles on the surface of a three-dimensional spherical skeleton supported by Ti3C2TX MXene nanosheets through template method and electrostatic self-assembly, and obtained Co3O4/Co/NC@MXene microspheres with an obvious hollow structure after one-step pyrolysis. This magnetic carbon heterostructure could effectively optimize the impedance matching and achieve efficient microwave absorption. The HCCM-800 sample had a minimum reflection loss value of −71.60 dB with thickness of 2.25 mm and a maximum effective absorption bandwidth achieved 5.14 GHz at 1.85 mm. Meanwhile, the radar cross section (RCS) simulation revealed that the HCCM-800 sample’s RCS reduction value could reach 20.2 dBm2 at 0° incidence angle. It is believed that this research will pave the way for further vigorous development in the field of microwave absorption.

High-performance electromagnetic wave absorbers based on hierarchically porous (Zn1/2Ni1/2)Co2O4 spinel clusters

The development of lightweight electromagnetic wave absorbers with strong absorption performance, and broad absorption bands has garnered significant attention toward electromagnetic protection. In this study, 3D hierarchically porous (Zn1/2Ni1/2)Co2O4 spinel clusters were synthesized via a straightforward hydrothermal reaction followed by calcination. Notably, the (Zn1/2Ni1/2)Co2O4 spinel calcined at 500 ℃, the hierarchically porous (Zn1/2Ni1/2)Co2O4 spinel clusters achieved the minimum reflection loss value and effective absorption band of −66.6 dB and 6.45 GHz at a matching thickness of 2.47 mm and 2.35 mm, respectively. These outcomes were due to the synergistic effects induced by dielectric loss, magnetic loss, and the unique hierarchical porous structure of the prepared spinel. Our findings will promote the development of electromagnetic protection technologies and inspire the design and fabrication of high-performance electromagnetic wave absorbing materials.