Radar Absorbing Research Articles

An optically transparent flexible metasurface absorber with broadband radar absorption and low infrared emissivity

The rapid development of surveillance technology has driven the research of multispectral stealth. Demand for infrared and microwave radar compatible stealth is becoming increasingly urgent in military applications. Herein, a versatile metamaterial absorber is designed and fabricated to simultaneously achieve ultra-broadband radar scattering reduction, low infrared emission, and high optical transparency. The designed structure consists of an infrared stealth layer, radar absorption layers, and backing ground. The infrared stealth layer employs specifically indium tin oxide (ITO) square patches, while the radar absorption layers can be obtained by stacking different size ITO patterned films of the same structure with high surface resistances, realizing broadband microwave stealth performance in the 1.98–18.6 GHz frequency range with an incident angle of 45°. The broad radar stealth and low infrared emissivity of 0.283 are consistent with the simulations and calculations. Furthermore, the designed structure exhibits characteristics such as polarization insensitivity, wide incident angles, optical transparency, and flexibility, allowing for a wide range of applications in various environments.

A new approach to design multi section wideband transmissive absorber using thin resistive sheets and dielectric slabs

A new design and analytical procedure are presented that greatly enhance the absorption bandwidth and absorptivity level with few dielectric layers without using the metallic ground plane. The performance of the proposed structure is beyond what is possible with Salisbury screen or Jaumann absorber. The performance improvement is obtained using the resistive sheets coated on the surface of each lossless dielectric slab. Reflected waves inside each dielectric layer are eliminated and input reflection coefficient can easily be written with the aid of binomial expansion without any approximation. So we can apply Binomial design and considerable improvement at the absorption level and bandwidth is realized by the selection of the resistive sheets with the critical resistivity values. Alternatively, we observed that transmission is independent from frequency and layer number and it can be controlled only by the initial and final layer’s dielectric constants. Two cases are analyzed as air to air and air to dielectric. Absorptivity, transmittivity and reflectivity variations are presented versus frequency in 0–20 GHz band, in both cases. It is shown that choosing three layers backed with a final layer (εrb=20) structure in air to air case gives absorptivity greater than 90% in 5.45–14.55 GHz band where fractional bandwidth is 91% at 10 GHz design frequency. The design is performed at normal incidence and also wide angular stability at a reasonable level is presented. CST Microwave Studio and AWR simulation programs are also used to prove the correctness of the proposed method.

Superior EMI shielding effectiveness of light weight and stretchable X-type hexaferrite-poly(vinylidene fluoride) laminated nanocomposite materials

In the present report, X-type hexaferrite-poly(vinylidene fluoride) laminated nanocomposite films have been fabricated by the solution casting method. The coexistence of a large magnetic moment of these X-type hexaferrite nanoparticles and a large electric dipole moment of polar PVDF matrix in the nanocomposite state make them more suitable for a wide range of EMI shielding applications. The high EMI shielding effectiveness of −69.5 dB at 9.9 and 11.7 GHz and −84.8 dB at 12.5 GHz and −83.8 dB at 14.1 GHz by the nanocomposite films have been observed. The high attenuation (>99.999999%) and wide bandwidth offers a completely unique nanocomposite material for the fabrication of affluent Radar Absorbing Materials (RAMs) to perform against the pollution caused by the high frequency EM radiations. Herein, the article also proposes the fabrication of electromagnetic shielding jacket and its application in daily life to combat against EM pollution.

A Rational Design Procedure for Absorbers of Square-Loop-Shaped Resistive Frequency Selective Surface Placed on Glass/Epoxy Laminate

This study proposes a rational optimum design procedure for broadband radar absorbers composed of a square-loop-shaped resistive frequency selective surface (FSS) that are placed on an E-glass fabric/epoxy laminate and grounded by Cu foil covering the X-band (8–12 GHz). A rational optimum design procedure for the broadband absorbing performance was presented based on the analytical and numerical illustration. The effects of the surface resistance of the FSS and dielectric substrate on the design process and performance of the absorber are examined. The resistive FSS was fabricated using screen-printing technology with carbon-type ink as a demonstration. The demonstration samples were developed considering the sectional profile of the circuit lines composing the printed FSS. It revealed that the experimental reflection loss encompassing the frequency range over the entire X-band was repeatable and similar to the simulation result.

The Distorted Octahedral and Magnetocrystalline Anisotropy of FeMnO<sub>3</sub> by Stoner-Wohlfarth Model

Among magnetic materials, ferrites have significant attention due to their potential application, such as magnetic recording, sensors, radar-absorbent materials, catalysts, and energy-storage devices. One of the ferrites family, FeMnO3, has been synthesized by solid-state reaction using Fe2O3 powder with an excess of 0.02% MnO2 powder in the stoichiometric composition. The structural and morphological properties have been performed using XRD and SEM at room temperature. The diffraction peaks in the pattern were indexed as FeMnO3 with a cubic (bixbite, Ia3) crystal structure. It showed no additional peaks due to impurities. The SEM image reveals the grains nucleate in a cube-like shape. Some of the particles also seem to agglomerate into larger particles. The magnetic characterization was carried out using VSM at room temperature. The magnetic hysteresis loop (M-H curves) notices the ferrimagnetic behavior. The results show remnant magnetization (Mr), coercive field (Hc), magnetic moment (µB), and anisotropy constant of FeMnO3 are 0.296 emu/g, 299 Oe, 0.046 emu/mol, and 0.1 when the external field is 70˚-80˚ from the easy axis, respectively.

Study of the radar absorption of metal-carbon nanocomposites (review)

Development of the technology for the synthesis of magnetic nanoparticles of metals and alloys has opened up the possibility of their use in the field of radar-absorbing materials (RAM). The results of studying the properties of nanocomposites, method for the synthesis of metal-carbon nanocomposites by pyrolysis using infrared heating are reviewed. The magnetic, electromagnetic, and radar-absorbing properties of the obtained nanocomposites depending on the synthesis temperature and metal concentration were studied. It is shown that the chosen metals, alloys (FeCo) and carbon material are effective for isolating magnetic nanoparticles when developing hybrid radar-absorbing composites. Moreover, methods for controlling the radar-absorbing properties of hybrid composites and the prospects for improving the impedance matching are considered. An analysis of the efficiency of absorption of electromagnetic radiation by FeCo/C nanocomposites synthesized by different methods is presented. The possibility of controlling the morphology and properties of metal-carbon nanocomposites using certain approaches to synthesis, varying the compositions of precursors, and the orientation of FeCo nanoparticles synthesized in the form of flakes in the composite has been revealed. The results of the study can be used to improve the technique of using FeCo/C nanocomposites obtained by pyrolysis of organometallic precursors based on polyacrylonitrile in the field of radar-absorbing materials.

Transparent broadband absorber based on a multilayer ITO conductive film.

Present study reports a novel visible-light transparent, microwave broadband absorbing metamaterial. The designed structure is implemented using three different sizes of indium tin oxide (ITO) conductive film patch arrays, which is capable of achieving a reflection coefficient ≤ -10 dB from 2.2 to 18 GHz in simulations. Moreover, a fractional bandwidth of about 156.4% and the absorber thickness of only 0.088 times the cutoff wavelength (the lowest absorption frequency) was achieved. Changing the angle of incidence ensures a good absorption effect with large angle stability, and the absorber has good transmission in the visible range. In accordance with the simulation, a sample with a size of 299 × 299 mm was fabricated, and its wave absorption performance was assessed. The experimental results and the various incidence angles in the simulation of the TE and TM modes correspond well, allowing for the realization of large angle broadband absorption at frequencies ranging from 2.2 to 18 GHz. Thus, it has been found that the structure has good optical transparency and broadband radar absorption capability, both of which will have a wide range of applications in the fields of multi-spectrum stealth and electromagnetic compatibility.

Optimal design of multilayer radar absorbing materials: a simulation-optimization approach

Multilayer radar absorbing materials with light weight, strong absorption, and wide absorption bandwidth are urgently demanded with the increase of electromagnetic pollution. However, the current design methods with only simulation operation or optimization strategy are not comprehensive. Here, a simulation-optimization approach including electromagnetic simulation and numerical calculation is proposed based on the interaction between different software, in which the homogeneous medium substitution method is presented to simplify the complicated structures. Besides, return loss and impedance matching of different layer structures are investigated. From the simulated results, it can be found that the structures with better impedance matching have superior absorbing performance. The optimal method shows the advantages of fast and efficient, which has tremendous potential for various applications, such as military stealth and electromagnetic wave elimination.

Ultra-wideband flexible radar-infrared bi-stealth absorber based on a patterned graphene.

In this work, an ultra-wideband flexible radar absorber with low infrared emissivity for a radar-infrared bi-stealth application utilizing multilayer patterned graphene is proposed. The proposed absorber consists of three layers of graphene films with different patterns, flexible substrates, lightweight foam, and a ground layer. The flexible graphene films, rather than the conventional lumped resistors, are adopted as omnidirectional resistors to achieve dual polarization and flexibility. On the top of the absorber, an infrared shielding layer (IRSL) consists of patterned Indium tin oxide (ITO) separated by a thin foam layer. Due to the low-pass characteristics and the high filling ratio of the top ITO layer, the infrared emissivity of the whole structure is reduced effectively while the radar absorption property is slightly affected. As a result, the 90% absorption band is from 1.96 GHz to 20.72 GHz (fractional bandwidth 165.4%), with a low infrared emissivity of about 0.35. Besides, a miniaturized unit is achieved with the period of 0.079 λl at the lowest absorption frequency, and the oblique angle incidence response is up to 45° for TE mode and 60° for TM mode. A plane and a bending prototype are fabricated and measured, respectively. The screen-printing technology is adopted to print the graphene resistive films, and the measurement results agree well with the simulation.

Exploring the role of Mn2+ in the structure, magnetic properties, and radar absorption performance of MnxFe3-xO4-DEA/MWCNT nanocomposites.

Iron oxide/carbon-based nanocomposites are known as an ideal combination of magnetic-conductive materials that were recently developed in radar absorption application; one example is the Fe3O4/multiwalled carbon nanotubes (MWCNTs). In this study, we try to boost their radar absorption ability by Mn-ion doping. Mn is an appropriate Fe substitute that is predicted to alter the magnetic properties and enhance the conductivity, which are crucial to developing their radar absorption properties. Diethylamine (DEA) is also used as a capping agent to improve the size and shape of the nanocomposite. In this study, a MnxFe3-xO4-DEA/MWCNT nanocomposite is successfully prepared by the coprecipitation method using a variation of x = 0, 0.25, 0.5, 0.75, and 1. We found that the sample's magnetic saturation (Ms) decreases, while the reflection loss (RL) increases with increasing the molar fraction of Mn. The enhancement of the radar wave absorption in the sample is dominated by dielectric losses due to the increase of electrical conductivity and interfacial polarization with the addition of Mn in the nanocomposites. We believe that our finding could shed light on the role of doping elements to develop the radar absorption properties, and further pave the way for the real implementation of iron oxides/graphene-based nanocomposite as radar-absorbing materials (RAMs).

Data Analysis of Polyethylene Base RAM for Small Vehicle’s low Signature’s Applications

The signature of radar target is an important aspect in military war. The demands for low signature targets have been increased to achieve the ‘critical mission successes’ in defence. Worldwide scientists and engineers are incessant working on it. This paper presents the data analysis of radar absorbing material (RAM) suitable for attaining of low signature applications for small air vehicles such as sUAV, μUAV, drones, hexcopter, spy birds etc. In this paper, the polyethylene (PE) and their composites characteristics and data analysis are presented, for applications in small air vehicles to attain the lower value of their target signatures. This is achieved in terms of EM measurement parameters of RAM material such as reflection loss, transmission loss, absorption loss, shielding effectiveness (SE), radar cross section (RCS) etc. The obtained values of reflection loss are – 29.49 dB, - 36.91 dB and – 23.94 dB; then, the transmission loss are – 133.18 dB, - 128.70 dB and – 0.19 dB for PE, polyethylene terephthalate (PET) and PET + conductive paint (PETCP) respectively for materials by waveguide measurement (WGM) method. The SE range are – 0.009 dB to – 0.19 dB, - 0.005 dB to - 0.29 dB, and - 0.022 dB to – 1.91 dB in WGM; then, - 9.44E-07 dB to – 1.13E-06 dB, - 9.57E-07 dB to – 1.01 E-06 dB and – 9. 31 E-07 dB to – 1.08E-06 dB in OATS experiments for PE, PET and PETCP respectively for the materials are obtained. The lowest value of RCS in OATS method are 1.63E-08 , 6.46E-08 and 5.63E-08 for PE, PET and PETCP respectively for material are obtained. The contact angle & material thickness (t) are 78.50 & 0.08 mm; 66.18 & 0.09 mm and 93.45 & 0.12 mm for PE, PET and PETCP respectively, are proposed in this paper. There is good agreement between the material controlling parameters design and the tabular analysis presented in this paper. This materials are used as RAM in small aircrafts, sUAV, μUAV, drones, hexcopter, spy birds, ships etc, to attain their low signature value, low RCS, stealth and shielding applications in X – band of 8 to 12 GHz frequency range.

Enhanced magnetic properties in Sm3+ substituted SrFe12O19

M- Type hexaferrite captivates researchers and industrialists for its diverse usage and applications in different fields such as permanent magnets, storage devices, recording media, radar absorbing materials and many more. In this work, Sm3+ substituted Strontium hexaferrite, Sr1-xSmxFe12O19 (x = 0, 0.05) is synthesized by using ethylene glycol aided sol–gel auto combustion technique. X-Ray Diffraction Technique is employed for the understanding of various structural features. Phase purity of the prepared samples is authenticated by performing Rietveld refinement method. All the studied samples crystallizes in hexagonal magneto-plumbite phase with P63/mmc space group. Crystallite sizes are determined using Scherer equation. Field Emission Scanning Electron Microscopy is used for morphological analysis. Average particle size decreases with Sm3+ substitution in comparison with parent one. Both field and temperature dependent magnetization measurements are accomplished for magnetic properties analysis. Hysteresis curves show Coercivity (Hc) value increases more than two times and saturation magnetization (MS) decreases slightly as compared to parent sample which clearly indicates that the sample can be used as hard ferrites. M−T measurements are carried out with the application of 500 Oe field. Both the sample show transition around 500 °C temperature. Substituted sample also shows a prominent Hopkinson peak in comparison with parent sample.

High-performance microwave absorption by optimizing hydrothermal synthesis of BaFe12O19@MnO2 core-shell composites.

Stealth technology advances in radar-absorbing materials (RAMs) continue to grow rapidly. Barium hexaferrite is the best candidate for RAMs applications. Manganese dioxide (MnO2) is a transition metal with high dielectric loss and can be used as a booster for changing polarization and reducing reflection loss. The advantages of BaFe12O19 and MnO2 can be combined in a core-shell BaFe12O19@MnO2 composite to improve the material's performance. MnO2 composition, temperature, hydrothermal holding time, and sample thickness all have an impact on the core-shell structure. In this study, a core-shell BaFe12O19@MnO2 composite is synthesized in two stages: molten salt synthesis to produce BaFe12O19 as the core and hydrothermal synthesis to synthesize MnO2 as the shell. In the hydrothermal synthesis, BaFe12O19 and KMnO4 were mixed in deionized water using different mass ratios of BaFe12O19 to KMnO4 (1 : 0.25, 1 : 0.5, 1 : 0.75, and 1 : 1). The main goal of the analysis was to figure out how well the hydrothermal synthesis method worked at different temperatures (140 °C, 160 °C, and 180 °C) and holding times (9 h, 12 h, and 15 h). The composite material was subjected to characterization using a vector network analyzer, specifically at thicknesses of 1.5 mm, 2 mm, 2.5 mm, and 3 mm. The hydrothermal temperature and composition ratio of BaFe12O19 : MnO2 are the most influential parameters in reducing reflection loss. Accurate control of the parameters makes a BaFe12O19@MnO2 core-shell composite structure with a lot of sheets. The structure is capable of absorbing 99.99% of electromagnetic waves up to a sample thickness of 1.5 mm. The novelty of this study is its ability to achieve maximal absorptions on a sample with minimal thickness through precise parametric control. This characteristic makes it highly suitable for practical applications, such as performing as an anti-radar coating material. BaFe12O19@MnO2 demonstrates performance as a reliable electromagnetic wave absorber material with simple fabrication, producing absorption at C and X band frequencies.

Polarization-Insensitive Absorptive/Transmissive Reconfigurable Frequency Selective Surface With Embedded Biasing

In this letter, a polarization-insensitive absorptive/transmissive reconfigurable frequency selective surface (RFSS) using p-i-n diodes is presented. The RFSS structure incorporates two periodically arranged metallic patterns on both sides of an FR4 dielectric substrate, where the p-i-n diodes are aligned symmetrically on the bottom surface. Depending upon the diode biasing conditions, the geometry behaves as a radar absorber and a bandpass filter under different working states. The simulated response exhibits a near-unity absorption response (having absorptivity of 93.51%) at 6.93 GHz during <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> state of the diode, whereas the incident electromagnetic wave gets transmitted through the structure at 5.62 GHz during <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> state. An embedded biasing circuitry has also been developed comprising metallic vias and inductors, such that the geometry displays polarization-insensitive and angularly stable responses for both states. The structure has been analyzed with the help of circuit modeling and other parametric variations to explain the switching methodology. A prototype has been fabricated and measured using the parallel-plate waveguide technique, which results in a good agreement with the simulated responses. Such RFSSs can be marked as a potential element for various radome applications.

The performance of radar absorption of Mn&lt;sub&gt;x&lt;/sub&gt;Fe&lt;sub&gt;3–x&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;/rGO nanocomposites prepared from iron sand beach and coconut shell waste

&lt;abstract&gt; &lt;p&gt;In this work, the Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; nanoparticles from natural iron sand were doped with Mn and combined with reduced-graphene oxide (rGO) to obtain Mn&lt;sub&gt;x&lt;/sub&gt;Fe&lt;sub&gt;3–x&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;/rGO nanocomposites with mole fraction variations of the Mn of 0.25, 0.5, and 0.75. The crystalline phase of the synthesized Mn&lt;sub&gt;x&lt;/sub&gt;Fe&lt;sub&gt;3–x&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;/rGO nanocomposites formed an amorphous phase. The presence of rGO was observed through EDX results. The magnetical properties of Mn&lt;sub&gt;x&lt;/sub&gt;Fe&lt;sub&gt;3–x&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;/rGO nanocomposites were shown by decreasing the Br, H&lt;sub&gt;c&lt;/sub&gt;J, H&lt;sub&gt;max&lt;/sub&gt; along with increasing of Mn doping. Interestingly, increasing rGO and Mn composition made the absorption bandwidth of the Mn&lt;sub&gt;x&lt;/sub&gt;Fe&lt;sub&gt;3–x&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;/rGO nanocomposites wider, so that the radar absorption also increased marking by the greater reflection loss that reached −11.95 dB. The increase in the radar absorption performance of Mn&lt;sub&gt;x&lt;/sub&gt;Fe&lt;sub&gt;3–x&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;/rGO nanocomposites came from the efficient complementarity between dielectric loss and magnetic loss and interfacial polarization between Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; doped Mn and rGO.&lt;/p&gt; &lt;/abstract&gt;

Enhanced microwave absorption performance of large-sized monolayer two-dimensional Ti&lt;sub&gt;3&lt;/sub&gt;C&lt;sub&gt;2&lt;/sub&gt;T&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; based on loaded Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; nanoparticles

With the rapid development of electronic equipment, electromagnetic interference and electromagnetic radiation pollution have become serious problems, because excessive electromagnetic interference will not only affect normal operation of electronic equipment but also do great harm to human health. In general, an ideal material for microwave absorption with the characteristics of high reflection loss (RL) intensity, wide effective absorption band (EAB), thin thickness, and lightweight could effectively consume electromagnetic wave (EMW) energy. Therefore, it is crucial to search for such an ideal microwave absorption material to deal with the electromagnetic radiation pollution. Two-dimensional (2D) carbon/nitride MXene has received more and more attention in recent years, because excellent electrical conductivity and rich surface-functional groups in MXene show positive effects on electromagnetic wave absorption. However, as a non-magnetic material with only dielectric loss, MXene exhibits obvious impedance mismatch, which greatly limits its practical applications. Combining MXene with magnetic materials becomes a hotspot for the exploration of ideal microwave absorption materials. As a typical ferrite, Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; shows excellent soft magnetic properties such as high saturation magnetization, high chemical stability, and simple preparation. In this paper, the 2D Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;@Ti&lt;sub&gt;3&lt;/sub&gt;C&lt;sub&gt;2&lt;/sub&gt;T&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; composite is successfully prepared by hydrothermal method and simple electrostatic adsorption process. The Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; nanoparticles are uniformly anchored on the surface of large-sized monolayer Ti&lt;sub&gt;3&lt;/sub&gt;C&lt;sub&gt;2&lt;/sub&gt;T&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;, which effectively reduces the stacking of MXene. By regulating the proportion of magnetic materials, the microwave absorption performance of 2D Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;@Ti&lt;sub&gt;3&lt;/sub&gt;C&lt;sub&gt;2&lt;/sub&gt;T&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; composite is investigated. With the content of Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; nanoparticles in the 2D Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;@Ti&lt;sub&gt;3&lt;/sub&gt;C&lt;sub&gt;2&lt;/sub&gt;T&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; composite increasing from 4 mg to 8 mg, the microwave absorption performance is enhanced obviously. This is caused by the abundant Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;/Ti&lt;sub&gt;3&lt;/sub&gt;C&lt;sub&gt;2&lt;/sub&gt;T&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; interface, scattering channels, point defect, charge density difference in 2D Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;@Ti&lt;sub&gt;3&lt;/sub&gt;C&lt;sub&gt;2&lt;/sub&gt;T&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; composite, and the optimized impedance matching. The minimum reflection loss (RL&lt;sub&gt;min&lt;/sub&gt;) of 2D Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;@Ti&lt;sub&gt;3&lt;/sub&gt;C&lt;sub&gt;2&lt;/sub&gt;T&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; composite reaches –69.31 dB at a frequency of 16.19 GHz, and the effective absorption band (EAB) achieves 3.39 GHz. With the content of Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; nanoparticles further increasing to 10 mg, the microwave absorption performance shows a decreasing trend. Excessive Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; nanoparticles in the 2D Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;@Ti&lt;sub&gt;3&lt;/sub&gt;C&lt;sub&gt;2&lt;/sub&gt;T&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; composite lead to the decrease of electrical conductivity and thus the impedance dis-matching and dielectric loss decreasing, which leads the microwave absorption performance to decrease. Radar scattering cross section (RCS) is a physical quantity that evaluates the intensity of the scattered echo energy in the intercepted electromagnetic wave energy. The results of the RCS simulation can be applied to real objects which have been widely utilized in radar wave stealth. Its multi-angle simulation results can be used as an important basis for evaluating the stealth capability of microwave-absorbing material. The RCS simulations show that the average RCS value of 2D Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;@Ti&lt;sub&gt;3&lt;/sub&gt;C&lt;sub&gt;2&lt;/sub&gt;T&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; composite is over –47.92 dBm&lt;sup&gt;2&lt;/sup&gt; at an incidence angle of 25°, demonstrating its excellent radar wave absorption performance. This study provides new ideas for improving and practically using two-dimensional and magnetic materials in the microwave absorption field and gives a new path to the subsequent development of microwave-absorbing composites.

Designing Thinner Broadband Multilayer Radar Absorbing Material Through Novel Formulation of Cost Function

Designing Thinner Broadband Multilayer Radar Absorbing Material Through Novel Formulation of Cost Function

The effect of Mg-Al substitution, particle size reduction, and thickness of BaFe12-2xMgxAlxO19 samples on increasing electromagnetic wave absorption

The synthesis of microwave-absorbing materials through a combined destruction process using mechanical alloying and ultrasonic vibration is significant due to its practical, waste-free scalability. Barium hexaferrite is the best candidate for synthesizing radar absorber materials through a combined destruction process. The substitution of Mg-Al on barium hexaferrite and decreasing particle size can increase the absorption of electromagnetic waves. Mixing stoichiometric precursors Sigma Aldrich 99 % BaCO 3 , Fe 2 O 3 , Al 2 O 3 , and MgO through wet milling for 20 h, followed by sintering at 1200 °C for 2 h to grow crystal embryos. Mechanical alloying was used to create the single-phase BaFe 12-2x Mg x Al x O 19 (x = 0; 0.3; 0.5; 0.7). re-milling for 20 h and ultrasonic vibration for 2 h reduced the particle size of the Mg-Al reinforced barium hexaferrite crystalline material. The increase in Mg-Al substitution in barium hexaferrite does not change the hexagonal structure but increases the density and absorption of electromagnetic waves. Mg-Al substitution at x = 0.3 resulted in uniform average particle size of 211.8 nm with a narrow particle size distribution, resulting in the lowest reflection loss of −17.62 dB at 8.2 GHz. This research increases the absorption ability of BaFe 11.4 Mg 0.3 Al 0.3 O 19 electromagnetic waves up to 98 %.

Bionic structures for optimizing the design of stealth materials.

Traditional microwave absorbing materials (MAMs) have exposed more and more problems in multi-spectrum detection and a harsh service environment, which hinder their further application. Bionic materials and structures have attracted more and more attention from researchers in the field of stealth materials due to their excellent properties, such as high strength and high conductivity, along with easy access to scale adjustability and structural design. By introducing the concept of bionics into their structural design and material design, we can obtain highly efficient stealth materials with multiple properties. In addition, the concept of multispectral stealth is furthered by comparing the difference in the principle and methods of achievement between radar stealth and infrared stealth. This paper fundamentally summarizes the research status of bionic structure design ideas in stealth materials, analyzing the structure-activity relationship between the structural size effect and electromagnetic characteristics from low order to high order. Then, the design ideas and universal strategies of typical bionic structures are summarised and an idea for the integrated design of radar absorption compatible with infrared stealth is put forward. This will provide profound insights for the application of biomimetic stealth materials and the future development of intelligent-response and dynamically adjustable materials.

Radar Absorbing Properties of Barium Hexaferrite Accompanying with Cu Powders in Polymer Composite Coatings

Radar, which is an electronic and electromagnetic system that works with the use of radio waves to detect and locate objects, has led to the need for radar absorber materials for some military applications, especially for defence and security. In this study, barium hexaferrite and copper powders were used to investigate a radar absorbing composite material. Barium hexaferrite powders were synthesized by Sol-Gel method. Barium hexaferrite and copper powders were added to a polyurethane resin at different loading levels to interpolate the radar absorption property. Metal substrates were covered with these polymeric composite materials. Characterization tests such as X-Ray Diffraction, Scanning Electron Microscopy (SEM) and scratch test were performed. For evaluating the radar absorbing properties of reinforced composites, a Network Analyzer was used. It was concluded that use of barium hexaferrite and copper powders improved absorbing activity of the coatings. Increasing the amount of barium hexaferrite and copper powders in the coatings, increased the radar absorption performance. Besides, very good synergistic effects were obtained in between barium hexaferrite and Cu powders. The reason for this is thought to be their own individual magnetic properties and electrical that work in the radar absorption mechanism.