Entire X-band Research Articles

PEDOT:PSS-patched magnetic graphene films with tunable dielectric genes for electromagnetic interference shielding and infrared stealth

The intelligent era brings electronics closer to humans, but also produces a large scale of electromagnetic (EM) radiation simultaneously, which causes serious harm to health and high sophisticated equipment. Exploring the underlying response logic of EM materials is urgently needed to face the challenge of EM interference (EMI) and secondary EM pollution better. Herein, PEDOT:PSS-patched magnetic graphene films are fabricated by vacuum-assisted molecular patching engineering, with tunable EM wave response. Based on the observation of micro-nano structure, the dielectric genes are visually revealed, which offers a bran-new horizon for the optimization of EM properties. Impressively, the constructed films achieve double band shielding toward gigahertz wave and infrared radiation. The optimal EMI shielding efficiency exceeds 99 %, and covers the entire X-band. Meanwhile, the green shielding index rises from 0.3 to 0.6, indicating that it is a potential green EMI shielding materials. Furthermore, the periodic macroscopic interfaces and the inherent thermal anisotropy endow the films with thermal insulation and flexible infrared stealth functions in simulated thermal environments. This work refreshes the insight into multi-band shielding, providing a new idea to EM energy governance.

Macro-ordered porous carbon nanocomposites for efficient microwave absorption

Tunable and efficient porous carbon-based microwave absorbers are essential in electromagnetic compatibility and protection due to their pronounced dielectric losses and ultralow density. However, it is still challenging to achieve satisfactory impedance matching and attenuation ability owing to the difficulty of realizing custom-designed porous structures. Herein, we propose a material-structure collaborative approach which includes multi-scaling, component modulation and systematic investigation of macroscopic structures. Macro-ordered porous carbon nanocomposites (MOPCN) assembled with MWCNTs and chitosan (CHI) were fabricated via freeze casting and MWCNTs/CHI ratio regulation. By simply varying the freezing temperature gradient distribution from radial (R) to axial (A), radial-centrosymmetric and honeycomb-like pore arrays were realized respectively. Compared with the honeycomb-like pore array, the radial-centrosymmetric pore array imparts much stronger microwave attenuation capability due to enhanced phase contiguity and optimized spatial arrangement. Such configuration also enabled one to optimize impedance matching and absorption, alleviating the over-dependence of microwave absorption performance on material composition. Optimum absorption of up to −70.6 dB at 9.3 GHz and −72.9 dB at 8.8 GHz were achieved for the MOPCN-1/4-R and MOPCN-1/2-A composites, respectively, with effective absorption band covering the entire X-band at a low filler loading of 1 wt%. Overall, this study provides a further understanding of the structure-property relationship and paves the way for future exploration of plainified microwave absorbers based on optimized macropore structures while preserving low filler loading.

Slotted Substrate-Integrated Waveguide Leaky-Wave Antenna with Improved Backward Scanning Bandwidth and Constant Gain in X-band

An H-shaped slotted leaky-wave antenna (LWA) is proposed based on balanced composite right/left-handed (CRLH) transmission lines (TLs) to improve the backward scanning bandwidth and achieve constant gain. The proposed antenna consists of a substrate-integrated waveguide (SIW) unit cell array configured by an H-shaped slot cut in the top layer of the SIW and a patch embedded beneath the H-shaped slot. The proposed design improves the backward scanning bandwidth compared to planar SIW LWAs. The measured beam radiation is in the range from −79° to 80° over the frequency range of 7.6–12.5 GHz. Moreover, a constant gain of greater than 10 dB is achieved over the entire X-band frequency range.

A Broadband Filtering Circularly Polarized Folded Transmitarray Antenna Based on Metasurface

This letter presents a broadband filtering circularly polarized (CP) folded transmitarray antenna (FTA) with a linearly polarized (LP) feed antenna based on metasurface (MS). The whole antenna mainly consists of two MSs located on the top and bottom layers and an LP feed antenna. LP to CP wave (LP-CP) conversion and phase compensation are achieved across the entire X-band with the designed top MS. The top bandpass MS is also used as a spatial filter, utilizing its out-of-band suppression characteristics and high passband edge selectivity. A fabricated prototype was measured, and the results reveal that its maximum gain is 27.8 dBi at 10.2 GHz with an aperture efficiency of 40%. It also achieves a 3-dB gain bandwidth of 24.5% and a 3-dB axial-ratio (AR) bandwidth of 41.1%, which is in good agreement with the simulation results as well. The proposed broadband CPFTA achieves a bandpass filtering response while also retaining the advantages of low profile, high gain, and low cost, which illustrates great application potential in future wireless communication systems.

Ultralight reduced graphene oxide/SiO2–C nanofibers composite aerogel decorated with Li0.35Zn0.3Fe2.35O4 nanoparticles with a three-dimensional bridging network for efficient electromagnetic wave absorption

Developing flexible, lightweight, and highly efficient electromagnetic wave (EMW) absorption materials was an effective strategy for mitigating the adverse health effects of microwaves. However, synthesizing flexible wave-absorbing aerogels via a novel method is challenging. In this study, a 3D porous reduced graphene oxide (RGO)/SiO2–C nanofibers (NFs)/Li0.35Zn0.3Fe2.35O4 (LZFO) flexible composite aerogel with a crosslinked structure was synthesized via electrospinning, freeze-drying, and in situ curing. To achieve this, electrospun SiO2 and polyacrylonitrile NFs, graphene oxide (GO), and LZFO nanoparticles were uniformly dispersed in an aqueous solution containing (Al(H3PO4)3) as a crosslinking agent and a crosslinked aerogel was formed by freeze-drying, pre-oxidation and carbonization. The obtained aerogels exhibited a good 3D porous structure. By introducing (Al(H3PO4)3) the cell binding force between the 0D, 1D and 2D materials was improved. Further, the introduction of SiO2 NFs reduced the brittleness of the C NFs and improved the flexibility of the aerogel. Under 60% strain, the stress reached 132 kPa, and a complete closed loop was formed. The RGO and C NFs conductive network coupled with the LZFO nanoparticles magnetic network form an ideal impedance matching. The minimum reflection loss (RLmin) of the RGO/SiO2–C NFs/LZFO-2 aerogel reached −55.2 dB (2.5 mm), and effective absorption bandwidth (EAB) was 5.5 GHz (2 mm) to cover the entire X-band. Moreover, by adjusting the matching thickness (2–4 mm), the RLmin was below −20 dB, and more than 99% of the EMW was absorbed. This study provides a new way to develop flexible absorbent materials for human protection.

The effects of lanthanum ions substitution on properties and effective absorption bandwidth (EAB) of zinc ferrite

A comprehensive study was conducted to examine the effect of lanthanum (La3+) ions substitution on zinc ferrite crystallography parameters, microstructure, and related physical properties. In this work, ZnLaxFe(2-x)O4 (0.01 ≤ x ≤ 0.04) compositional series were prepared by co-precipitation method. Rietveld refinement method combined with Raman spectra analysis reveal that all compositions are only crystallized into zinc ferrite (ZnFe2O4) after high-temperature treatment at 1000 °C for 5 h La3+ ions preferentially reside in BO6 sub-lattice, which corresponds to the expanding unit cell and octahedral volume of ZnFe2O4. The elongation of cation-anion bonds at the BO6 sub-lattice (∼0.02 Å) and the movement of oxygen toward the AO4 sub-lattice play an important role in weakening super-exchange interaction (SE) between sub-lattices and raising the frustration of magnetic structure as confirmed by the electron density (ED) mapping analysis. The particle size of the sample was decreased from ∼1400 nm for x = 0.01–∼600 nm for x = 0.04. These factors were found to cause the decrease of the magnetization values (Ms and Mr) and the increase of field coercivity due to the increase of La3+ ions substitution. The substitution of La3+ ions are found effective to improve the microwave absorbing (MA) ability of zinc ferrite. The trends of MA ability are related with the different spin-orbit coupling of La–Fe, impedance matching characteristic, natural magnetic resonance, and particle size distribution. The substitution of La3+ ions in the composition of x = 0.04 (ZnLa0.04Fe1, 96O4) affected the full coverage of the EAB across the entire X-band frequency range, making it an excellent microwave absorbing materials (MAMs) candidate.

Impact mechanisms of aggregation state regulation strategies on the microwave absorption properties of flexible polyaniline

In the field of electromagnetic (EM) wave absorption, intrinsic conductive polymers with conjugated long-chain structures, such as polyaniline (PANI) and polypyrrole (PPy), have gained widespread use due to their remarkable electrical conductivity and loss ability. However, current research in this area is limited to macroscopic descriptions of the absorption properties of these materials and the contribution of various components to the absorption effect. There has been insufficient exploration of the impact mechanisms of polymer aggregation states on the material's absorption performance and mechanism. To address this, a series of flexible PANI sponge absorbers with different molecular weights and aggregation states were prepared. By carefully controlling the crystallinity and other aggregation characteristics of PANI through the adjustment of its preparation conditions, we were able to influence its electrical conductivity and electromagnetic parameters, thereby achieving control over the material's absorption properties. The resulting PANI sponge absorbers exhibited an effective absorption bandwidth (EAB) that covered the entire X-band at a thickness of 3.2 mm. This study comprehensively explores the absorption mechanisms of conductive polymer absorbers, starting from the microstructure of PANI, and providing a more complete theoretical support for the research and promotion of polymer absorbers.

Sandwich structure electromagnetic interference shielding composites based on Fe3O4 nanoparticles/PANI/laser-induced graphene with near-zero electromagnetic waves transmission

High-performance electromagnetic interference (EMI) shielding materials with flexible and lightweight characteristics are still a hot research direction, which will be highly promising in many application fields. In this work, laser-induced graphene (LIG) as the top and bottom layer, and binary composites of co-precipitated Fe3O4 NPs and in-situ chemical polymerized PANI (FePA) functioned as the intermediate layer is assembled to prepare a sandwich structure shielding material (FePA/LIG composite). 3D porous LIG with excellent conductivity is conducive to promote reflection and multiple reflections of incident electromagnetic waves (EMWs), while the transmitted EMWs will be further absorbed and attenuated via FePA composite due to its high impedance matching and microwave absorption (MA) properties. Near-zero EMWs transmission can be achieved and the average EMI shielding effectiveness (SE) of FePA/LIG composite (with thickness less than 2 mm) over the entire X-band and Ku-band is 50 dB and 63 dB, respectively. The admirable EMI shielding performance and flexibility of FePA/LIG composite endows enormous potential in portable electronic devices.

Construction of sandwich-structured Cu-Ni wood-based composites for electromagnetic interference shielding

Constructing a controllable electromagnetic gradient toward advanced electromagnetic interference shielding composites has become a development trend. A sandwich-structured Cu-Ni wood composite (CNWC) was successfully fabricated via a simple electroless Cu-Ni procedure. The obtained results showed that the Cu-Ni wood composite material exhibited excellent electromagnetic shielding effectiveness (EMSE) (average value 57.4 dB) in the entire X-band (from 8.2 to 12.4 GHz) in case of low thickness (0.4 mm) and low density (0.87 g/cm3). Herein, the wood-based composites possessed maximum saturation magnetization which was up to 7.7 emu/g and the conductivity increased to 1930 S/cm. The dielectric loss and magnetic loss are important ways of electromagnetic wave attenuation in Cu-Ni-based electromagnetic shielding materials, and are the key to the absorption of most electromagnetic waves by composites. The electromagnetic gradient sandwich-structure can realize multi-dielectric interface loss and multiple reflection loss. When the electromagnetic wave enters the porous structure inside the wood, the electromagnetic wave generates internal scattering and multiple reflections in the hole. The synergistic effect of dielectric loss and magnetic loss to improve the loss ability of electromagnetic wave.

A distinct structure of TiC for electromagnetic interference shielding and thermal stability of SiTiOC ceramic nanocomposites

Materials capable of thermal stability electromagnetic interference (EMI) shielding have practical significance in the fields of aerospace. In this paper, a brand-new polymer-derived SiTiOC ceramic nanocomposites with tubular carbon was designed. The titanium atoms were uniformly introduced into the polysiloxane backbone by the transesterification between tetrabutyl titanate and silanol prepolymer, leading to excellent thermal stability properties. By controlling the pyrolysis temperature, a distinct structure of TiC was formed between the amorphous SiTiOC matrix and free carbon phase for enhanced electromagnetic interference shielding performance. More conductive paths were established, and the TiC structure initiated interfacial polarization and space charge polarization, contributing to the improvement of the dielectric loss and relaxation phenomena. Simultaneously, a total electromagnetic interference shielding efficiency of 27.85 dB at the entire X-band was reported for SiTiOC ceramic nanocomposites. A maximum SET of 38.59 dB was examined at around 12 GHz, suggesting that over 99.99% of the electromagnetic waves were shielded. The SiTiOC ceramic nanocomposites exhibited outstanding prospects in thermal stability electromagnetic interference shielding application in a severe environment.

Enhancement of Microwave Absorption Properties of Hexaferrite/Epoxy Composites on the Addition of Non-magnetic Oxides

The effect of non-magnetic oxides such as Al2O3, TiO2 and ZnO on the microwave absorption properties of magnetoplumbite barium hexaferrite (BaFe11.8Co0.2O19) is analyzed. Barium hexaferrite nanoparticles are synthesized through the sol-gel auto-combustion method. BaFe11.8Co0.2O19-Al2O3, BaFe11.8Co0.2O19-TiO2 and BaFe11.8Co0.2O19-ZnO composites are synthesized in a 1:1 ratio through mechanical mixing and heat treatment. The epoxy composites are fabricated with 50% loading of BaFe11.8Co0.2O19-Al2O3, BaFe11.8Co0.2O19-TiO2 and BaFe11.8Co0.2O19-ZnO in epoxy matrix followed by room temperature curing. The powder XRD analyses showed homogeneous distribution of BaFe11.8Co0.2O19 and Al2O3 in BaFe11.8Co0.2O19-Al2O3 composite while TiO2 and ZnO phases dominate in BaFe11.8Co0.2O19-TiO2 and BaFe11.8Co0.2O19-ZnO composites, respectively. Scanning electron microscopy shows the evenly distributed BaFe11.8Co0.2O19 and Al2O3 in BaFe11.8Co0.2O19-Al2O3 composites. The electromagnetic characterization calculated from experimental permittivity and permeability shows reflection loss RL ≤ -10 dB (≥ 90% absorption) for a very small thickness of 0.5 mm over the entire X-band (8-12 GHz) for BaFe11.8Co0.2O19-Al2O3 composites. BaFe11.8Co0.2O19-TiO2 and BaFe11.8Co0.2O19-ZnO show RL < - 8 dB with a thickness of 2.5 mm over the frequency range 8–9.7 GHz and RL < - 8 dB with a thickness of 3.6 mm over 8.7-11.1 GHz, respectively. Further, when compared with BaFe11.8Co0.2O19 alone (RL < -7 dB at 3.2 mm in 8-11 GHz), the BaFe11.8Co0.2O19-Al2O3 composite is superior both in terms of the thickness of the coating as well as the percentage absorption in the X-band.

PANI-coated YIG/CFO hybrid composites as advanced electromagnetic wave absorber through X-band

Polyaniline (PANI)-coated Y3Fe5O12(YIG)/CoFe2O4(CFO) hybrid composites were synthesized via sol-gel and oxidative polymerization methods to achieve advanced microwave absorption properties. The structural, morphological, magnetic, and microwave absorption characteristics of the resulting samples were analyzed by performing X-ray diffraction (XRD), scanning electron microscopy (SEM), vibration sample magnetometer (VSM), and vector network analyzer (VNA). XRD results revealed that CFO and YIG have cubic crystal structures with Fd3m and Ia3d space symmetry, respectively, with an average crystallite size of 35.3 nm and 42.9 nm. The Ferro/ferrimagnetic signals were detected from the ferrite samples' room temperature magnetic hysteresis loops. The incorporation of PANI and YIG into the composites resulted in a decrease in their magnetic saturation (Ms) and coercive field (Hc) values. VNA measurements demonstrated that nearly all samples achieved 90% absorption (≤−10 dB) of incident electromagnetic waves throughout the X-band frequency range. The minimum reflection loss (RLmin) value reaches − 47.34 dB at 8.14 GHz, with an effective bandwidth of 4.00 GHz, covering the entire X-band and beyond. These impressive absorption characteristics suggest that the manufactured composites possess potential as viable candidates for defense applications conducted at X-band frequency.

Versatile graphene-alumina nanofibers for microwave absorption and EMI shielding

Carbon-based hybrid nanostructures have shown to be promising candidates as cost-efficient and effective fillers for electromagnetic interference shielding and RF absorption. In this work, hybrids of graphene-augmented inorganic (alumina) nanofibers (GAIN) have been incorporated in epoxy resin to fabricate a multilayer structure with tunable absorption. Highly aligned graphene augmented alumina nanofibers of 10 ± 2 nm in diameter were produced with the help of a hot wall one-step catalyst-free chemical vapor deposition method at 1000 °C. Effective medium approximation has been used to calculate the intrinsic dielectric properties of GAIN nanofibers. The highest loss tangent of 0.4 has been achieved in a 5 mm thick composite containing 1 vol% of randomly oriented nanofibers. Furthermore, aligned graphene augmented nanofibers were embedded in an epoxy resin matrix to examine the effect of fiber alignment on the dielectric properties of the composite. Based on the obtained dielectric data, a superposed three-layer structure has been fabricated, offering an absorption of >90% in the entire X-band and an absorption peak of −25 dB at ∼11 GHz. Several multilayer designs based on finite element method coupled with Monte Carlo simulations have been proposed to tune the absorption characteristics. This work demonstrates the potential of the hybrid nanofibers with a dual loss function for versatile design options in the area of RF absorption.

Dual template induced assembly of 2D nanosheets to 3D porous Mo2C/NiFe-NC networkers for electromagnetic wave absorption

Developing high-performance materials with ultrathin matching thickness for electromagnetic wave absorption (EMW) is essential for the commercialization of electromagnetic devices, but it is still formidably challenging. In this work, Mo2C/NiFe-NC networker with small Mo2C grains, NiFe alloy coated by graphitized carbon (NiFe-NC), and N-doped carbon matrix are constructed by free-drying and dual template strategy. With the assistance of hard template (salt, NaCl)) and soft template (urea), the ultrathin 2D layered carbon nanosheets produced by pyrolysis are assembled into a 3D hierarchical porous network. The designed Mo2C/NiFe-NC networker exhibits a hierarchical porous structure, 3D network skeleton, heterogeneous interface, abundant heteroatom doping, and magnetic NiFe alloy, which inherits good dielectric loss (dipole polarization, interfacial polarization, and conduction loss), magnetic loss (natural resonance and exchange resonance) and considerable impedance matching characteristics. Impressively, the well-designed Mo2C/NiFe-NC networker enables a reflection loss (RL) value of −51.56 dB at an ultrathin matching thickness of 1.4 mm. Furthermore, the effective absorption bandwidth (EAB, RL ≤ −10 dB) is up to 3.7 GHz. Importantly, the EAB in the matching thickness range of 1–5 mm is as high as 14.6 GHz, covering the entire C-band, X-band, and Ku-band. This work may open a key avenue for high-performance EMW absorption materials via a dual template assistance strategy.

Machine Learning Empowered Magnetic Substrate Coupled Broadband and Miniaturized Frequency Selective Surface

This works offers a polarization-insensitive, wide angular stable, and wideband electromagnetic interference shielding structure using an integration of frequency selective surface (FSS) with magnetic substrates. The equivalent circuit model (ECM) together with the analytical model is derived to figure out the physics of the shielding structure. The overall inductance of the shielding structure is increased using a magnetic ferrite sheet and magnetic silicon rubber sheet as substrates. Further, four different deep neural network configurations are investigated with inverse modeling to predict the shielding structure parameters within a fraction of seconds. The mse between expected and predicted output is only 2.92 × <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10^{-8}$</tex-math></inline-formula> . The entire X-band is shielded with a minimum 10-dB shielding effectiveness (SE) and with SE of 56 dB at resonance. The FSS unit cell size is only 0.21 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> × 0.21 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> . Furthermore, the proposed shielding structure shows stable transmission performance up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$75^{\circ}$</tex-math></inline-formula> angle of incidence for both perpendicular and parallel polarization. Finally, a prototype is fabricated and measured using nondestructive free space measurement. Good agreement among the simulated, ECM, analytical model, and measured results demonstrate the efficacy of the proposed technique for building an effective shielding structure.

Broadband absorber with dispersive metamaterials

Abstract A broadband absorber that utilizes a dispersive metamaterial and covers the entire microwave X-band (8–12 GHz) is proposed in the present study. An ideal absorber attached to the surface of a perfect electric conductor requires the permittivity of the absorbing layer to be anomalously dispersive in the targeted broad frequency band. We show that anomalous dispersion of the permittivity for the X-band can be fitted to a two-pole Lorentz oscillator model and realized with the use of a double-layered, square-loop metamaterial. We explain the connection between the two-pole oscillator model and the double-layered, square-loop metamaterial using an equivalent circuit model and present explicit design rules for the metamaterial. We fabricate a 4-mm-thick metamaterial absorber with flexible silicon rubber, a resistor element, and conductive wire using carbon and silver conductive ink. Our metamaterial absorber achieves a reflectance of less than −20 dB over the entire X-band region.

Embedding magnetic 3D carbon skeleton in SiCN ceramics for high-performance electromagnetic shielding

The electromagnetic (EM) characteristics of SiCN-based composite ceramics were adjusted by embedding magnetic 3D carbon skeleton (3D-CS) into SiCN ceramics through electroplating and polymer derivation. The distribution uniformity of carbon conductive networks and magnetic particles in composite ceramics were effectively improved profiting from the scheme adopted in this work. In addition, Ni distributed on CS catalyzed the in-situ formation of carbon nanowires (CNWs) in the matrix, and also coordinated the magnetic properties of the ceramics by reacting with Si to form Ni2Si. Benefiting from the embedding of conductive CS and dual role of Ni, the electromagnetic wave (EMW) absorption rate of composite ceramics was improved, and the electromagnetic shielding (EMS) performance was significantly enhanced. When the electroplating time was fixed at 50 min, the EMS value (SETotal) of the composite ceramics in the entire X-band was greater than 55 dB, indicating that more than 99.999% of EMWs are shielded. Beyond that, composite ceramics have excellent solvent (PH = 1 and PH = 14) resistance performance and are powerful candidates for EMS materials in harsh environments.

Multifunctional carbon nanotubes-based hybrid aerogels with high-efficiency electromagnetic wave absorption at elevated temperature

In the complex engineering applications of electromagnetic (EM) wave-absorbing materials, it is insufficient for these materials to exhibit only efficient EM wave attenuation ability. EM wave-absorbing materials featuring numerous multifunctional properties are increasingly attractive for next-generation wireless communication and smart devices. Herein, we constructed a lightweight and robust multifunctional hybrid aerogel consisting of carbon nanotubes/aramid nanofibers/polyimide with low shrinkage and high porosity. The hybrid aerogels exhibit excellent EM wave attenuation, with an effective absorption bandwidth covering the entire X-band from 25 °C to 400 °C. The conductive loss capacity of the hybrid aerogel is enhanced under thermal drive, which results in an enhanced ability to attenuate EM waves, as evidenced by the fact that the best-fit thickness drops from 5.3 to 3.6 mm with increasing temperature. In addition, the hybrid aerogels are capable to efficiently absorb sound waves, with an average absorption coefficient as high as 0.86 at 1–6.3 kHz, and they exhibit superior thermal insulation properties, with a thermal conductivity as low as 41 ± 2 mW/mK. They are thus suitable for applications in the anti-icing and infrared stealth fields. The prepared multifunctional aerogels have considerable potential for EM protection, noise reduction, and thermal insulation in harsh thermal environments.

Preparation and properties of Ti3SiC2 preform reinforced SiC ceramic matrix composites

Ti3SiC2 preform reinforced SiC ceramic matrix composites (Ti3SiC2/SiC) were successfully fabricated through a novel near-net-shape process strategy combining molten salt synthesis with subsequent polymer infiltration and pyrolysis (PIP) for the first time. The effects of temperature and molten salt ratio on the phase composition, pore structure, and flexural strength of Ti3SiC2 preform were investigated in detail. The morphology and microstructure evolution of the composites during the PIP process were observed by SEM and TEM. The mechanical properties, electromagnetic interference shielding effectiveness (EMI SE) and thermal conductivity of Ti3SiC2/SiC were significantly improved compared to PDC-SiC, which benefits from the connected network skeleton of Ti3SiC2 preform. The flexural strength and fracture toughness of Ti3SiC2/SiC are 198.7 MPa and 4.5 MPa∙m1/2. The EMI SE remains above 30 dB covering the entire X-band and its average value is 46.92 dB. The thermal conductivity is 6–7 W/(m·k) (25–1000 °C).

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.