Electromagnetic Absorption Properties Research Articles

Electromagnetic wave absorption properties of red mud-blast furnace slag based geopolymers filled with various wave-absorption materials

In this work, red mud-blast furnace slag (RM-BFS) based geopolymers with excellent electromagnetic wave absorption property is synthesized through the incorporation of wave-absorption materials. The electromagnetic absorption property of geopolymer is characterized through the arched test, in which the reflection loss of specimens is tested by vector network analyzer (VNA). The microstructure and conductivity of geopolymers are characterized through scanning electron microscopy (SEM), concrete porous structure analyzer and conductivity tester. The crystalline phase and functional groups of geopolymers are characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Compared to Portland cement concrete (PCC), wave absorption band of the geopolymer is wider and the absorption peak in high frequency band is more intense. With the optimal addition of hollow glass microsphere (HGM), Fe2O3 and graphite particles, the absorption bandwidth with reflection loss less than −5 dB are 12.4, 7.7 and 8.1 GHz, and the maximum reflection loss are −9.4, −8.4 and −8.7 dB, respectively. This study might give a clue for preparation of geopolymers with high electromagnetic wave absorption properties.

FeCo@SiO2@polyaniline nanocomposite toward efficient electromagnetic wave absorption

A core-shell FeCo@SiO2@polyaniline nanocomposite was prepared via modified Stöber process and in-situ polymerization method. The synergistic effect of excellent impedance matching, significant attenuation system, conduction loss, dipole polarization, interface polarization as well as good magnetic loss make the FeCo@SiO2@ polyaniline nanocomposite exhibit good electromagnetic absorption properties. When the matching thickness is 1.8 mm, a minimum reflection loss of −31 dB is obtained at 9 GHz. The effective absorbing bandwidth is up to 7.25 GHz (10.75–18.0 GHz), almost covering the entire Ku-band and partial X-band, and the corresponding matching thickness is only 1.9 mm.

Study of magnetic, elastic and Ka-band absorption properties of Zn1−xCoxFe2O4 (0.00 ≤ x ≤ 1.00) spinel ferrites

Magnetic, elastic, electromagnetic, and microwave absorption properties of cobalt-substituted zinc spinel ferrites Zn1-xCoxFe2O4 (0.00 ≤ x ≤ 1.00, Δx = 0.25) fabricated via the sol–gel citrate route are analyzed. The hysteresis loops of constituent ferrites revealed the rapid rise in saturation magnetization and coercivity with the doping of cobalt ions. The FT-IR spectra exhibit two vibrational bands in the scope of 521–560 cm−1 and 397–404 cm−1. Complex permittivity (ɛr) and complex permeability (µr) are analyzed using a vector network analyzer in Ka-band. The absorption is maximized by tuning the thickness of the sample from 0.8 mm to 3.5 mm using the quarter wavelength model. Maximum absorption of 99.14 % at a matching frequency of 34.60 GHz and a matching thickness of 1 mm is obtained by the composition with × = 0.75. The prepared ferrite composition proves to be an efficient microwave-absorbing material at high frequencies ranging from 26.5 to 40 GHz.

Hollow porous magnetic/magnetic heterostructured CoFe/defective spinel microspheres template-free synthesis and effective modulation of microwave absorption performance

To create a spinel ferrite with excellent performance for electromagnetic (EM) wave absorption in the low frequency range of 4–6 GHz, compositions based on Co0.75Zn0.125Fe0.125Fe2O4 (CZF–1) and Co0.5Zn0.25Fe0.25Fe2O4 (CZF–2) with multiple elements substituted for A sites were synthesized by using solvothermal method. Hollow porous magnetic/magnetic heterostructure microspheres (HHMs) of CZF–A1 and CZF–A2 with multiple interfaces were prepared by hydrogen–thermal reduction of CZF–1 and CZF–2, and their unique structure and EM absorption properties were investigated in detail. The widest effective absorption bandwidth (EAB) of CZF–A1 and CZF–A2 was 4.1 GHz (13.6–17.7 GHz) and 3.7 GHz (8.0–11.7 GHz) for a corresponding thickness of 1.4 mm and 2.0 mm, respectively. In addition, the minimum reflection loss (R.Lmin) of CZF–A1 and CZF–A2 reached –49.1 dB (at fm = 13.4 GHz) and –45.0 dB (at fm = 4.2 GHz) at a thicknesses of 1.6 mm and 3.7 mm, respectively. More specifically, in the low frequency region of 4–6 GHz, CZF–A1 and CZF–A2 exhibited excellent EM wave absorption due to the effective regulation of their natural resonance frequency. The EM wave absorption frequency band of CZF–A1 and CZF–A2 samples was able to completely cover the 4–6 GHz frequency region for at coating thickness of CZF–A1 and CZF–A2 was only 3.5 mm and 3.3 mm respectively, and their R.Lmin reached –36.5 dB and –22.6 dB. Moreover, the absorption mechanisms of CZF–A1 and CZF–A2 including magnetic resonance, eddy current loss, interfacial polarization and dipole polarization were also investigated in detail. This research provides new insights and guidance for the development of spinel ferrite-based EM absorbers for high efficiency EM wave absorption in the low frequency (4–6 GHz) region.

Structural, Optical, and Electromagnetic Microwave Absorption Properties of Bael Leaves: A Simple Approach to Investigate Microwave Absorption Properties with 3D Printed PLA Tubes

Structural, Optical, and Electromagnetic Microwave Absorption Properties of Bael Leaves: A Simple Approach to Investigate Microwave Absorption Properties with 3D Printed PLA Tubes

Synthesis of nitrogen-doped graphene-based binary composite aerogels for ultralightweight and broadband electromagnetic absorption

The development of ultralightweight and broadband electromagnetic wave (EMW) absorbing materials remains a big challenge. In this work, porous magnesium ferrite microspheres decorated nitrogen-doped reduced graphene oxide (NRGO/MgFe2O4) composite aerogels were prepared by a two-step route of solvothermal synthesis and hydrothermal self-assembly. Results of microscopic morphology characterization showed that NRGO/MgFe2O4 composite aerogels had a unique hierarchical porous structure. Moreover, the influence of additive amounts of graphene oxide on the electromagnetic parameters and EMW absorption properties of NRGO/MgFe2O4 composite aerogels was explored. Remarkably, the attained binary composite aerogel with the content of NRGO of 70.21 wt% exhibited the best EMW absorption performance. The minimum reflection loss reached up to −55.7 dB, and the corresponding effective absorption bandwidth was as large as 5.36 GHz at a thin matching thickness of 1.98 mm. Furthermore, when the matching thickness was slightly increased to 2.29 mm, the widest effective absorption bandwidth was enlarged to 7.1 GHz, covering the entire Ku-band. The magnetodielectric synergy and unique hierarchical porous structure in NRGO/MgFe2O4 composite aerogels not only improved the impedance matching, but also greatly enhanced the EMW absorption capacity. It was believed that the results of this work could be helpful for the preparation of graphene-based magnetic composites as broadband and efficient EMW absorbers.

Ag–Ni–Fe–P multielemental nanoparticles in situ grown on reduced graphene oxide with excellent electromagnetic absorption properties

Ag–Ni–Fe–P multielemental nanoparticles in situ grown on reduced graphene oxide with excellent electromagnetic absorption properties

Preparation and characterization of a composite ceramic coating containing absorber LaFe12O19 by plasma spraying

A ceramic coating with both heat-resistant and electromagnetic (EM) wave absorption performances is prepared by the atmospheric plasma spraying (APS) method. The spraying powder is a composite material mainly containing LaFeO3 and La(Mg/Fe)Al11O19 without EM absorption ability. During APS procedure, a new phase of LaFe12O19 is fabricated by the chemical reaction between Fe2O3 and LaFeO3 at extremely high temperatures. The ceramic coating exhibits larger saturation magnetization (Ms) and higher EM absorption performance than that of the unsprayed sample. The coating Ms is 31 emu/g, and the optimal reflection loss is −39.30 dB at 3.5–5.2 GHz with 4.5 mm thickness. The ceramic coating with both heat-resistant and EM absorption properties is a potential application prospect material in the military industry.

Flexible microwave absorbing composites based on polydimethylsiloxane filled with hybrid carbonaceous materials: Statistical analysis of the synergistic effect

AbstractThe effect of the combination of carbon nanotubes (CNT) and graphene nanoplatelets (GNP) on the electromagnetic absorbing properties of polydimethylsiloxane (PDMS) composites was investigated. Samples were prepared by a low‐cost and scalable simple one‐step blending approach. The number of experiments and sample compositions were optimized by design of experiments (DOE) technique, namely, Axial Simplex Centroid. The samples were analyzed concerning rheology, electric conductivity and electromagnetic properties, such as absorptivity (reflection loss – RL). CNT was revealed to be more efficient than GNP in structuring the conductive network of filler particles. On the other hand, the hybrid filler composite with a 1:1 ratio (CNT/GNP = 0.67%:0.67%) presented the highest electric conductivity (3.53 × 10−3 S m−1) and the best overall electromagnetic results, with measured RL reaching −25 dB and effective absorption bandwidth frequency of 4.6 GHz, with sample 2 mm thick. The best calculated RL value for this sample was observed with 2.5 mm with RL value corresponding to −46.8 dB. The special cubic polynomial model was successfully adjusted to the experimental data and statistically proved the synergistic effect of the hybrid on the electromagnetic properties of PDMS composites. Finally, PDMS/CNT/GNP composites were successfully prepared by a simple, fast and inexpensive method.

Nickel Slag/Laterite Soil and Nickel Slag/Iron Sand Nanocomposites: Structural, Optical, and Electromagnetic Absorption Properties.

Efforts to produce microwave absorber materials that are inexpensive and environmentally friendly have become a means of greening the environment. The breakthrough can be focused on industrial waste and natural materials for functional purposes and how to enhance their performance. We successfully synthesized nickel slag/laterite soil (NS/LS) and nickel slag/iron sand (NS/IS) nanocomposites using a simple mechanical alloying technique, and the electromagnetic (EM) wave absorption capacities of the nanocomposites were measured using a vector network analyzer. The structural properties of the nanocomposites were analyzed by X-ray diffraction spectroscopy, where the results of the analysis showed that NS/IS has the largest crystallite size (15.69 nm) and the highest EM wave absorption performance. The optical properties of the nanocomposites were determined from their Fourier transform infrared spectra using the Kramers-Kronig relation. As determined through a quantitative analysis of the optical properties, the distance between the longitudinal and transversal optical phonon wavenumber positions (Δ(LO - TO) = 65 cm-1) is inversely proportional to the reflection loss. The surface morphologies of the nanocomposites were analyzed by scanning electron microscopy, and the particle diameters were observed by binary image and Gaussian distribution analyses. The nanocomposite surface exhibits a graded-like morphology, which indicates multiple reflections of the EM radiation, consequently reducing the EM interference. The best nanocomposite for an attenuated EM wave achieved a reflection loss of -39.14 dB at 5-8 GHz. A low penetration depth has implications for the electrical charge tuning of the storage and composite magnets. Finally, the EM absorption properties of NS/IS and NS/LS indicate a 2-mm-thick environmentally friendly nanocomposite for EM absorption.

Titanium boride fibers prepared by chloride-assisted carbothermic method for high-performance electromagnetic wave absorption

The TiB2 fibers were prepared by a chloride-assisted carbothermic method accompanied with the vapor-liquid-solid (VLS) mechanism. The influences of TiO2, B2O3, C12H22O11, and calcination temperature on the yield of TiB2 fibers were investigated. In addition, the effects of TiB2 fibers content on the electromagnetic (EM) parameters and microwave absorption (MA) properties of TiB2 fibers/paraffin composite was studied in detail. The TiB2 fibers/paraffin composite showed excellent microwave absorption performance, with an optimized reflection loss (RL) of −46.63 dB at 14 GHz and a thickness of 1.5 mm. Moreover, it exhibited a broad effective absorption bandwidth (EAB) (RL < −10 dB) of 3.9 GHz, ranging from 12 to 15.9 GHz. TiB2 fibers exhibit promising potential as materials for high-temperature applications in the field of MA.

Enhanced electromagnetic microwave absorption properties of SiCN(Fe) ceramics produced by additive manufacturing via in-situ reaction of ferrocene

SiCN(Fe) ceramics with excellent electromagnetic wave (EMW) absorption performance were successfully prepared from a preceramic polymer doped with ferrocene. Additive manufacturing (Digital Light Processing), providing enhanced structural design ability, was employed to fabricate samples with complex architectures. During pyrolysis, ferrocene catalyzed the in-situ formation of a large amount of turbostratic carbon, graphite and SiC nanosized phases, which formed carrier channels in the electromagnetic field and increased the conductivity loss. Meanwhile, it also increased the dipole polarization, interface polarization and the dielectric properties of the material, which finally enhanced the EMW absorption capacity of SiCN(Fe) ceramics. When containing 0.5 wt% ferrocene, the material showed good performance with EAB 4.57 GHz at 1.30 mm, and RLmin −61.34 dB at 2.22 mm. The RLmin of 3D-SiCN-0.5 ceramics was −6 dB, and the RL of the X-band was lower than −4 dB at 2 mm.

A study on microwave absorption properties of polyaniline/nitrile rubber/graphene/Fe3O4 composites with a thickness of 0.7 mm and high flexibility

AbstractThe genotoxic effect of microwave radiation on humans is one of the leading causes of some diseases like cancer. Despite many reported materials for microwave absorption, there is still a demand for a super‐thin and flexible microwave absorber. In the present work, we synthesized Fe3O4/graphene/polyaniline/nitrile butadiene rubber composites with a thickness of 0.7 mm using a melt mixing method. Then, we comprehensively studied the electromagnetic and microwave absorption properties of the composites from 8 to 12 GHz. The composite with 38 wt% Fe3O4 and 6 wt% graphene exhibited the highest microwave absorption of more than 8 dB in the entire range of 8–12 GHz, with a minimum reflection loss of −14 dB at 10.3 GHz. By increasing the weight content of Fe3O4 and graphene, the imaginary part of dielectric permeability and magnetic permeability initially went up and then declined, resulting in poor impedance matching. Hence, we precisely controlled the weight content of the fillers to reach the highest impedance matching and attenuation constant. Consequently, this work opened up a unique way for developing super‐thin, lightweight, flexible microwave‐absorbing materials.

Multidimensional nano-graphite constructed TiB2–SiC–B4C composite ceramics with the integration of mechanical and electromagnetic properties

The goal of this study is to create structure-functional integrated ceramic matrix composites with high structural strength and electromagnetic absorbing properties. The multidimensional nano-graphite (1-Dimensional rod-like nano-graphite, 0-Dimensional dispersive nano-graphite, and 2-Dimensional lamellar nano-graphite) were employed to construct TiB2–SiC–B4C composites via high-energy ball milling, vacuum filtration, and reactive SPS sintering. The microstructure of multidimensional nano-graphite was investigated using XRD and HRTEM and determined to be a crystal-amorphous coexisting. Furthermore, solid solution reaction and interfacial evolution are confirmed as the primary influence on the microstructure of TiB2–SiC–B4C composite. A significant improvement occurs on the flexural strength (647.6 MPa) and bending toughness (5.1 MPa m1/2). Meanwhile, the multi-dimensional nano-graphite gives the TiB2–SiC–B4C composite the loss ability of electromagnetic waves, and the matching thickness of the 10 vol% sample is 2.4 mm and the absorption range is 10.4–11.3 GHz.

Optimization of Ti with modified SiC ceramics for electromagnetic absorption properties

Optimization of Ti with modified SiC ceramics for electromagnetic absorption properties

A simple method for preparing flaky FeSiAl for low-frequency electromagnetic wave absorber

The effect of morphology and size on electromagnetic wave (EMW) absorption performance has been a relentlessly explored issue. By grinding the spherical FeSiAl alloy powder in a planetary ball mill, a flaky FeSiAl alloy with higher saturation magnetization, dielectric constant, magnetic permeability, and better impedance matching at low frequency was prepared. The phase composition, morphology, and static magnetism of FeSiAl alloys with different morphologies were studied through X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The electromagnetic parameters and absorption properties of the two kinds of powders were studied using a vector network analyzer (VNA). The results show that the crystallinity, dielectric constant, and magnetic permeability of the flaky FeSiAl powder increase compared with the spherical one. The absorption performance in the low-frequency band was remarkably improved after grinding. When the matching thickness is 6.5 mm, the reflection loss at 1 GHz reaches −16.89 dB for the flaky FeSiAl. The excellent EMW absorption performance of flaky FeSiAl alloy powder at low-frequency is mainly due to the large magnetic permeability and magnetic loss which is derived from the magnetocrystalline anisotropy brought about by lamellar morphology and appropriate impedance matching as well. This work provides a new idea for the preparation of low-frequency absorbing materials expected to be used in the L-band wave absorption field.

Tunable Electromagnetic and Microwave Absorption Properties of Magnetic FeNi3 Alloys.

Magnetic materials have a very broad application prospect in the field of microwave absorption, among which soft magnetic materials become the focus of magnetic materials research because of their high saturation magnetization and low coercivity. FeNi3 alloy has been widely used in soft magnetic materials because of its excellent ferromagnetism and electrical conductivity. In this work, FeNi3 alloy was prepared by the liquid reduction method. The effect of the filling ratio of FeNi3 alloy on the electromagnetic properties of absorbing materials was studied. It is found that the impedance matching ability of FeNi3 alloy is better when the filling ratio is 70 wt% than that of other samples with different filling ratios (30-60 wt%), showing better microwave absorption characteristics. When the matching thickness is 2.35 mm, the minimum reflection loss (RL) of FeNi3 alloy with a 70 wt% filling ratio reaches -40.33 dB, and the effective absorption bandwidth is 5.5 GHz. When the matching thickness is between 2 and 3 mm, the effective absorption bandwidth ranges from 7.21 GHz to 17.81 GHz, almost covering the whole X and Ku bands (8-18 GHz). The results show that FeNi3 alloy has adjustable electromagnetic properties and microwave absorption properties with different filling ratios, which is conducive to selecting excellent microwave absorption materials.

Constructing FeCo@C core-shell structure with strong polarization behavior towards excellent microwave absorption performance

In this study, the electromagnetic wave absorption properties of derivatives of metal-organic frameworks (Prussian blue analogues) were investigated. Here, we use the co-precipitation method to combine metal ions (Mn2+, Ni2+, Co2+) with potassium ferricyanide to obtain cubic precursors. Subsequently, a series of carbon-coated bimetallic alloy absorbers with a core-shell structure were obtained by pyrolysis in a vacuum thermal environment. Moreover, the effect of temperature on the structure and electromagnetic absorption properties of FeCo@C was further explored. FeCo@C-600 achieves an effective bandwidth of 5.63 GHz at a thickness of 1.8 mm, and the minimum reflection loss is as high as −66.69 dB. Its best microwave absorption performance comes from the polarization sites provided by the abundant heterogeneous planes and defects, enabling it to obtain enhanced polarization loss. The final results show that the method of optimizing performance by enriching polarization methods can provide a new idea for obtaining high-efficiency absorbing materials with thin thickness and wide frequency coverage.

High-entropy Pt18Ni26Fe15Co14Cu27 nanocrystalline crystals in situ grown on reduced graphene oxide with excellent electromagnetic absorption properties

The high entropy alloy is a powerful material due to its high hardness, strength, magnetic performance, corrosion resistance, and temperature stability. Moreover, when combined with reduced graphene oxide (rGO), it formed a novel material for electromagnetic (EM) absorption. In this work, monodisperse high entropy alloy nanocrystals combined with rGO to create a new type of high entropy alloy/rGO EM absorption material. A colloidal synthesis strategy was used to prepare high entropy Pt18Ni26Fe15Co14Cu27 nanocrystals with a small size of around 3.3 nm. These nanocrystals then in situ grew uniformly on the surface of rGO to form Pt18Ni26Fe15Co14Cu27/rGO nanocomposite, which were then characterized and tested for EM absorption performance. Compared to the pure high entropy Pt18Ni26Fe15Co14Cu27 nanocrystals, the composite exhibited an improved EM absorption performance with a minimum reflection loss of −41.8 dB at 4.9 GHz and efficient EM wave absorption up to a bandwidth of 2.5 GHz in the 9.4–11.9 GHz band. This novel high entropy alloy/rGO composite has great potential to be used as an excellent material for EM wave absorption.

Influence of Magnetic Wood on Mechanical and Electromagnetic Wave-Absorbing Properties of Polymer Composites

The application of wireless electronic devices is increasing nowadays; hence, there is a necessity for electromagnetic wave-absorbing material, which is mechanically stable. Polymer composites with magnetic wood as filler material were fabricated by hand lay-up methods of 6 mm thickness. For the proposed immersion duration, magnetic wood was developed by in situ chemical co-precipitation methods. The microwave absorbing phenomenon is evaluated based on the complex permeability, complex permittivity, dielectric tangent, and magnetic tangent losses. The experimentation was done by vector network analyzer in the frequency range of 8.2–12.4 GHz by X-band and Through-reflect-line (TRL) calibration. It was observed that the reflection losses increase as the immersion time increases from −8.70 dB to −9.30 dB at the frequency range of 10.2 GHz. A similar trend is also followed for the mechanical properties like tensile strength, bending strength, and impact strength with respect to the immersion time. The results revealed that the best mechanical and electromagnetic absorption properties are obtained for the specimens with immersion time of 72 hours. Validation is done for the electromagnetic wave-absorbing properties and mechanical properties by regression analysis, and the experimental data are in close agreement with the regression data.