Achieving Ultra-Wideband and Elevated Temperature Electromagnetic Wave Absorption via Constructing Lightweight Porous Rigid Structure

Fast, Low-Cost, and Lyophilization-Free Synthesis of Multifunctional Elastic Nanofiber Aerogels

Aerogels are regarded as ideal materials across a range of fields due to their exceptionally low densities and highly porous structures. However, their practical applications are significantly constrained by their inherent fragility, high production costs, and demanding conditions such as freeze-drying or supercritical drying. In this study, a novel, low-cost strategy is presented for the large-scale fabrication of hierarchically structured nanofiber aerogels (HENAs) using a lyophilization-free, dissolution-induced coordination (DIC) method. This approach enables fabrication within ≈4 h, which is 10 times faster than conventional lyophilization processes (usually require ≥48 h). Despite the absence of additional chemical crosslinking, the formation of stable coordination networks imparts the aerogels with excellent resilience (exhibiting only 3.9% deformation after 100 compression cycles). This strategy demonstrates fiber-type invariant universality, enabling the fabrication of HENAs with multifunctional properties, including noise absorption (noise reduction coefficient of 0.58), electromagnetic wave absorption (effective absorption bandwidth of 7.2 GHz), and oil adsorption (adsorbing capacity of 36.4 g g-1). The simplicity, rapidity, and cost-effectiveness of this synthesis approach provide a promising pathway for the large-scale production of multifunctional aerogels.

Optimized design, fabrication, and enhanced performance of honeycomb sandwich structure for excellent impact resistance and broadband microwave absorption

Lightweight microwave absorbing structures have wide applications in aerospace and military equipment. In general, honeycomb sandwich structure is regarded as an ideal choice. However, traditional honeycomb sandwich structure designs have limitations in improving absorption bandwidth, and their impact resistance remains unremarkable. Herein, a novel microwave absorbing honeycomb sandwich structure (MAHSS) has been thoroughly investigated through both theoretical and experimental validations. The MAHSS is crafted using a glass fiber (GF)/epoxy composite that is coated with reduced graphene oxide (RGO) for enhanced performance. The middle honeycomb layer of MAHSS is arranged transversely to add more interface. When the honeycomb core has 2 layers and a wall thickness of 2.4 mm in MAHSS, the maximum achievable bandwidth is 13.6 GHz, while the minimum reflection loss (RLmin) reaches -24.02 dB under TE mode. The mechanical properties of the MAHSS were evaluated by compression test and drop weight impact testing. The MAHSS exhibits excellent compression and impact resistance, accompanied by self-recovery performance post-unloading. It still did not penetrate under an impact energy of 150 J, absorbing up to 123 J of energy. This work provides theoretical guidance and technical support for designing and preparing structural and functional integration microwave absorption materials.

Ultra-Bandwidth Microwave Absorption and Low Angle Sensitivity in Dual-Network Aerogels with Dual-Scale Pores

Aerogels with porous structures offer an attractive approach to modulating electromagnetic parameters and enhancing electromagnetic wave (EMW) absorption performance. However, conventional aerogels are limited by their single-scale pore size and fixed orientation, which constrain their EMW absorption capabilities. This study introduces aerogels with dual-scale pores and dual-network structure constructed via constant-temperature freezing and secondary-infusion freezing method. Multiscale aerogels with both micrometer- and submillimeter-scale pores are constructed when the Ti3C2Tx MXene and thermoplastic polyurethane solution is frozen and dried at a specific temperature, leading to an ultra-wide effective absorption bandwidth (EAB) reaching 10.41 GHz in the vertical direction. Furthermore, to address the poor EMW absorption in the parallel direction, a secondary infusion freezing method is applied to form an aerogel with a dual-network structure, which forms reflective interfaces perpendicular to the incident EMW in various directions. This adjustment enhances the EAB in the parallel direction from 1.58 to 5.93 GHz, marking a 275.32% enhancement, while the EAB in the vertical incident direction reaches 8.08 GHz. This design strategy overcomes the limitations of structural scale and arrangement direction, enriching the attenuation mechanisms of the absorber, while effectively reducing sensitivity to the direction of incoming EMW, offering new insights for designing efficient EMW absorbers.

Self-Templating Engineering of Hollow N-Doped Carbon Microspheres Anchored with Ternary FeCoNi Alloys for Low-Frequency Microwave Absorption

Rational design and precision fabrication of magnetic-dielectric composites have significant application potential for microwave absorption in the low-frequency range of 2-8 GHz. However, the composition and structure engineering of these composites in regulating their magnetic-dielectric balance to achieve high-performance low-frequency microwave absorption remains challenging. Herein, a self-templating engineering strategy is proposed to fabricate hollow N-doped carbon microspheres anchored with ternary FeCoNi alloys. The high-temperature pyrolysis of FeCoNi alloy precursors creates core-shell FeCoNi alloy-graphitic carbon nano-units that are confined in carbon shells. Moreover, the anchored FeCoNi alloys play a critical role in maintaining hollow structural stability. In conjunction with the additional contribution of multiple heterogeneous interfaces, graphitization, and N doping to the regulation of electromagnetic parameters, hollow FeCoNi@NCMs exhibit a minimum reflection loss (RLmin) of -53.5 dB and an effective absorption bandwidth (EAB) of 2.48 GHz in the low-frequency range of 2-8 GHz. Furthermore, a filler loading of 20 wt% can also be used to achieve a broader EAB of 5.34 GHz with a matching thickness of 1.7 mm. In brief, this work opens up new avenues for the self-templating engineering of magnetic-dielectric composites for low-frequency microwave absorption.

Regulation of PPy Growth States by Employing Porous Organic Polymers to Obtain Excellent Microwave Absorption Performance

Regulating the different growth states of polypyrrole (PPy) is a key strategy for obtaining PPy composites with high electromagnetic wave (EMW) absorption properties. This work finds that the growth states of PPy is regulated by controlling the amount of pyrrole added during the preparation of composites, so as to regulate the development of conductive networks to obtain excellent EMW absorption performance. The POP/PPy-200 composite achieves an effective absorption bandwidth (EAB) of 6.24 GHz (11.76-18.00 GHz) at a thickness of only 2.34 mm, covering 100% of the Ku band. The minimum reflection loss of -73.05 dB can be demonstrated at a thickness of only 2.29 mm, while at the same time showing an EAB of 5.96 GHz to meet the requirements of "thin", "light", "wide", and "strong". Such excellent EMW absorption performance is attributed to the conductive loss caused by the regulation of the growth states of PPy and the polarization loss caused by the heterostructure. This work also addresses the key challenge that porous organic polymers (POPs) cannot be applied to EMW absorption due to poor conductivity and providing new insights into the candidates for EMW absorbing materials.

A Breathable Fibrous Membrane with Coaxially Heterogeneous Conductive Networks toward Personal Thermal Management and Electromagnetic Interference Shielding

The expeditious growth of wearable electronic devices has boomed the development of versatile smart textiles for personal health-related applications. In practice, integrated high-performance systems still face challenges of compromised breathability, high cost, and complicated manufacturing processes. Herein, a breathable fibrous membrane with dual-driven heating and electromagnetic interference (EMI) shielding performance is developed through a facile process of electrospinning followed by targeted conformal deposition. The approach constructs a robust hierarchically coaxial heterostructure consisting of elastic polymers as supportive "core" and dual-conductive components of polypyrrole and copper sulfide (CuS) nanosheets as continuous "sheath" at the fiber level. The CuS nanosheets with metal-like electrical conductivity demonstrate the promising potential to substitute the expensive conductive nano-materials with a complex fabricating process. The as-prepared fibrous membrane exhibits high electrical conductivity (70.38 S cm-1), exceptional active heating effects, including solar heating (saturation temperature of 69.7 °C at 1 sun) and Joule heating (75.2 °C at 2.9 V), and impressive EMI shielding performance (50.11 dB in the X-band), coupled with favorable air permeability (161.4 mm s-1 at 200 Pa) and efficient water vapor transmittance (118.9 g m-2 h). This work opens up a new avenue to fabricate versatile wearable devices for personal thermal management and health protection.

Lightweight Dual-Functional Segregated Nanocomposite Foams for Integrated Infrared Stealth and Absorption-Dominant Electromagnetic Interference Shielding

Lightweight infrared stealth and absorption-dominant electromagnetic interference (EMI) shielding materials are highly desirable in areas of aerospace, weapons, military and wearable electronics. Herein, lightweight and high-efficiency dual-functional segregated nanocomposite foams with microcellular structures are developed for integrated infrared stealth and absorption-dominant EMI shielding via the efficient and scalable supercritical CO2 (SC-CO2) foaming combined with hydrogen bonding assembly and compression molding strategy. The obtained lightweight segregated nanocomposite foams exhibit superior infrared stealth performances benefitting from the synergistic effect of highly effective thermal insulation and low infrared emissivity, and outstanding absorption-dominant EMI shielding performances attributed to the synchronous construction of microcellular structures and segregated structures. Particularly, the segregated nanocomposite foams present a large radiation temperature reduction of 70.2 °C at the object temperature of 100 °C, and a significantly improved EM wave absorptivity/reflectivity (A/R) ratio of 2.15 at an ultralow Ti3C2Tx content of 1.7 vol%. Moreover, the segregated nanocomposite foams exhibit outstanding working reliability and stability upon dynamic compression cycles. The results demonstrate that the lightweight and high-efficiency dual-functional segregated nanocomposite foams have excellent potentials for infrared stealth and absorption-dominant EMI shielding applications in aerospace, weapons, military and wearable electronics.

Structural Engineering of Hierarchical Magnetic/Carbon Nanocomposites via In Situ Growth for High-Efficient Electromagnetic Wave Absorption

Materials exhibiting high-performance electromagnetic wave absorption have garnered considerable scientific and technological attention, yet encounter significant challenges. Developing new materials and innovative structural design concepts is crucial for expanding the application field of electromagnetic wave absorption. Particularly, hierarchical structure engineering has emerged as a promising approach to enhance the physical and chemical properties of materials, providing immense potential for creating versatile electromagnetic wave absorption materials. Herein, an exceptional multi-dimensional hierarchical structure was meticulously devised, unleashing the full microwave attenuation capabilities through in situ growth, self-reduction, and multi-heterogeneous interface integration. The hierarchical structure features a three-dimensional carbon framework, where magnetic nanoparticles grow in situ on the carbon skeleton, creating a necklace-like structure. Furthermore, magnetic nanosheets assemble within this framework. Enhanced impedance matching was achieved by precisely adjusting component proportions, and intelligent integration of diverse interfaces bolstered dielectric polarization. The obtain Fe3O4-Fe nanoparticles/carbon nanofibers/Al-Fe3O4-Fe nanosheets composites demonstrated outstanding performance with a minimum reflection loss (RLmin) value of - 59.3 dB and an effective absorption bandwidth (RL ≤  - 10 dB) extending up to 5.6 GHz at 2.2 mm. These notable accomplishments offer fresh insights into the precision design of high-efficient electromagnetic wave absorption materials.

Promoting Electromagnetic Wave Absorption Performance by Integrating MoS2@Gd2O3/MXene Multiple Hetero-Interfaces in Wood-Derived Carbon Aerogels

Multi-component composite materials with a magnetic-dielectric synergistic effect exhibit satisfactory electromagnetic wave absorption performance. However, the effective construction of the structure for these multi-component materials to fully exploit the advantages of each component remains a challenge. Inspired by natural biomass, this study utilizes wood as the raw material and successfully prepares high-performance MoS2@Gd2O3/Mxene loaded porous carbon aerogel (MGMCA) composite material through a one-pot hydrothermal method and carbonization treatment process. With a delicate structural design, the MGMCA is endowed with abundant heterogeneous interface structures, favorable impedance matching characteristics, and a magnetic-dielectric synergistic system, thus demonstrating multiple electromagnetic wave loss mechanisms. Benefiting from these advantages, the obtained MGMCA exhibits outstanding electromagnetic wave absorption performance, with a minimum reflection loss of -57.5 dB at an ultra-thin thickness of only 1.9 mm. This research proposes a reliable strategy for the design of multi-component composite materials, providing valuable insight for the design of biomass-based materials as electromagnetic wave absorbers.

Highly Porous Yet Transparent Mechanically Flexible Aerogels Realizing Solar-Thermal Regulatory Cooling

The demand for highly porous yet transparent aerogels with mechanical flexibility and solar-thermal dual-regulation for energy-saving windows is significant but challenging. Herein, a delaminated aerogel film (DAF) is fabricated through filtration-induced delaminated gelation and ambient drying. The delaminated gelation process involves the assembly of fluorinated cellulose nanofiber (FCNF) at the solid-liquid interface between the filter and the filtrate during filtration, resulting in the formation of lamellar FCNF hydrogels with strong intra-plane and weak interlayer hydrogen bonding. By exchanging the solvents from water to hexane, the hydrogen bonding in the FCNF hydrogel is further enhanced, enabling the formation of the DAF with intra-layer mesopores upon ambient drying. The resulting aerogel film is lightweight and ultra-flexible, which possesses desirable properties of high visible-light transmittance (91.0%), low thermal conductivity (33 mW m-1 K-1), and high atmospheric-window emissivity (90.1%). Furthermore, the DAF exhibits reduced surface energy and exceptional hydrophobicity due to the presence of fluorine-containing groups, enhancing its durability and UV resistance. Consequently, the DAF has demonstrated its potential as solar-thermal regulatory cooling window materials capable of simultaneously providing indoor lighting, thermal insulation, and daytime radiative cooling under direct sunlight. Significantly, the enclosed space protected by the DAF exhibits a temperature reduction of 2.6 °C compared to that shielded by conventional architectural glass.

Advanced Science and Technology of Polymer Matrix Nanomaterials

The advanced science and technology of polymer matrix nanomaterials are rapidly developing fields that focus on the synthesis, characterization, and application of nanomaterials in polymer matrices [...].

Commonly Neglected Ester Groups Enhanced Microwave Absorption

Oxygen-containing functional groups have high potential to excite polarization loss. The nature and mechanism of the polarization loss brought on by oxygen-containing functional groups, however, remain unclear. In this study, metal-organic framework precursors are in situ pyrolyzed to produce ultrathin carbon nanosheets (UCS) that are abundant in oxygen functional groups. By altering the pyrolysis temperature, the type and concentration of functional groups are altered to produce good microwave absorption capabilities. It is demonstrated that the main processes of electromagnetic loss are polarization caused by "field effects and induced effects" brought on by strongly polar ester functional groups. Moreover, links between various oxygen functional groups and structural flaws are established, and their respective contributions to polarization are sharply separated. The sample with the highest ester group content ultimately achieves an effective absorption bandwidth of 6.47 GHz at a pyrolysis temperature of 800°C. This research fills a theoretical hole in the frequently overlooked polarization mechanism in the microwave band by defining the key polarization parameters in chaotic multiple dipole systems and, in particular, redefining the significance of ester groups.

Special Issue: Advanced Science and Technology of Polymer Matrix Nanomaterials

Polymer matrix nanomaterials have revolutionized materials science due to their unique properties resulting from the incorporation of nanoscale fillers into polymer matrices [...].

Construction of Self-Assembly Based Tunable Absorber: Lightweight, Hydrophobic and Self-Cleaning Properties

Although multifunctional aerogels are expected to be used in applications such as portable electronic devices, it is still a great challenge to confer multifunctionality to aerogels while maintaining their inherent microstructure. Herein, a simple method is proposed to prepare multifunctional NiCo/C aerogels with excellent electromagnetic wave absorption properties, superhydrophobicity, and self-cleaning by water-induced NiCo-MOF self-assembly. Specifically, the impedance matching of the three-dimensional (3D) structure and the interfacial polarization provided by CoNi/C as well as the defect-induced dipole polarization are the primary contributors to the broadband absorption. As a result, the prepared NiCo/C aerogels have a broadband width of 6.22 GHz at 1.9 mm. Due to the presence of hydrophobic functional groups, CoNi/C aerogels improve the stability in humid environments and obtain hydrophobicity with large contact angles > 140°. This multifunctional aerogel has promising applications in electromagnetic wave absorption, resistance to water or humid environments.

Core-shell FeCo@carbon nanocages encapsulated in biomass-derived carbon aerogel: Architecture design and interface engineering of lightweight, anti-corrosion and superior microwave absorption

The development of multifunctional microwave absorbing materials for practical applications in complex environments is a challenging research hotspot. Herein, the core-shell structure FeCo@C nanocages were successfully anchored on the surface of biomass-derived carbon (BDC) from pleurotus eryngii (PE) via freeze-drying and electrostatic self-assembly process, achieving lightweight, anti-corrosive, and excellent absorption properties. The superior versatility benefits from the large specific surface area, high conductivity, three-dimensional cross-linked networks, and appropriate impedance matching characteristics. The as-prepared aerogel realizes a minimum reflection loss (RL_min) of -69.5 dB with a corresponding effective absorption bandwidth (EAB) of 8.6 GHz at 2.9 mm. Simultaneously, the computer simulation technique (CST) further proves that the multifunctional material can dissipate microwave energy in actual applications. More importantly, the special heterostructure of aerogel endows excellent resistance to acid, alkali, salt medium, allowing potential applications of the microwave absorbing materials under complex environmental conditions.

Transformation from Electromagnetic Inflection to Absorption of Silicone Rubber and Accordion-Shaped Ti3C2MXene Composites by Highly Electric Conductive Multi-Walled Carbon Nanotubes

Electromagnetic (EM) pollution becomes more penetrating in daily life and work due to more convenience provided by multi-electrical devices, as does secondary pollution caused by electromagnetic reflection. EM wave absorption material with less reflection is a good solution to absorb unavoidable EM radiation or reduce it from the source. Filled with two-dimensional Ti₃SiC₂MXenes, silicone rubber (SR)composite demonstrated a good electromagnetic shielding effectiveness of 20 dB in the X band by melt-mixing processes for good conductivity of more than 10^-3 S/cm and displayed dielectric properties and a low magnetic permeability; however, the reflection loss was only -4 dB. By the combination of one-dimensional highly electric conductive multi-walled carbon nanotubes (HEMWCNTs) and MXenes, the composites achieved the transformation from electromagnetic inflection to an excellent absorbing performance to reach a minimum reflection loss of -30.19 dB due to electric conductivity of above 10^-4 S/cm, a higher dielectric constant, and more loss in both dielectric and magnetic properties. Ni-added multi-walled carbon nanotubes were not able to achieve the transformation. The as-prepared SR/HEMWCNT/MXene composites have potential application prospects in protective layers, which can be used for electromagnetic wave absorption, electromagnetic interference suppression of devices, and stealth of the equipment.

The In Situ Preparation of Ni-Zn Ferrite Intercalated Expanded Graphite via Thermal Treatment for Improved Radar Attenuation Property

The composites of expanded graphite (EG) and magnetic particles have good electromagnetic wave attenuation properties in the centimeter band, which is valuable in the field of radar wave interference. In this paper, a novel preparation method of Ni-Zn ferrite intercalated EG (NZF/EG) is provided in order to promote the insertion of Ni-Zn ferrite particles (NZF) into the interlayers of EG. The NZF/EG composite is in situ prepared via thermal treatment of Ni-Zn ferrite precursor intercalated graphite (NZFP/GICs) at 900 °C, where NZFP/GICs is obtained through chemical coprecipitation. The morphology and phase characterization demonstrate the successful cation intercalation and NZF generation in the interlayers of EG. Furthermore, the molecular dynamics simulation shows that the magnetic particles in the EG layers tend to disperse on the EG layers rather than aggregate into larger clusters under the synergy of van der Waals forces, repulsive force, and dragging force. The radar wave attenuation mechanism and performance of NZF/EG with different NZF ratios are analyzed and discussed in the range of 2-18 GHz. The NZF/EG with the NZF ratio at 0.5 shows the best radar wave attenuation ability due to the fact that the dielectric property of the graphite layers is well retained while the area of the heterogeneous interface is increased. Therefore, the as-prepared NZF/EG composites have potential application value in attenuating radar centimeter waves.

High-Entropy Spinel Ferrites with Broadband Wave Absorption Synthesized by Simple Solid-Phase Reaction

In this work, high-entropy (HE) spinel ferrites of (FeCoNiCrM)_xO_y (M = Zn, Cu, and Mn) (named as HEO-Zn, HEO-Cu, and HEO-Mn, respectively) were synthesized by a simple solid-phase reaction. The as-prepared ferrite powders possess a uniform distribution of chemical components and homogeneous three-dimensional (3D) porous structures, which have a pore size ranging from tens to hundreds of nanometers. All three HE spinel ferrites exhibited ultrahigh structural thermostability at high temperatures even up to 800 °C. What is more, these spinel ferrites showed considerable minimum reflection loss (RL_min) and significantly enhanced effective absorption bandwidth (EAB). The RL_min and EAB values of HEO-Zn and HEO-Mn are about -27.8 dB at 15.7 GHz, 6.8 GHz, and -25.5 dB at 12.9 GHz, 6.9 GHz, with the matched thickness of 8.6 and 9.8 mm, respectively. Especially, the RL_min of HEO-Cu is -27.3 dB at 13.3 GHz with a matched thickness of 9.1 mm, and the EAB reaches about 7.5 GHz (10.5-18.0 GHz), which covers almost the whole X-band range. The superior absorbing properties are mainly attributed to the dielectric energy loss involving interface polarization and dipolar polarization, the magnetic energy loss referring to eddy current and natural resonance loss, and the specific functions of 3D porous structure, indicating a potential application prospect of the HE spinel ferrites as EM absorbing materials.

Absorption-Dominant mmWave EMI Shielding Films with Ultralow Reflection using Ferromagnetic Resonance Frequency Tunable M-Type Ferrites

Although there is a high demand for absorption-dominant electromagnetic interference (EMI) shielding materials for 5G millimeter-wave (mmWave) frequencies, most current shielding materials are based on reflection-dominant conductive materials. While there are few absorption-dominant shielding materials proposed with magnetic materials, their working frequencies are usually limited to under 30 GHz. In this study, a novel multi-band absorption-dominant EMI shielding film with M-type strontium ferrites and a conductive grid is proposed. This film shows ultralow EMI reflection of less than 5% in multiple mmWave frequency bands with sub-millimeter thicknesses, while shielding more than 99.9% of EMI. The ultralow reflection frequency bands are controllable by tuning the ferromagnetic resonance frequency of M-type strontium ferrites and composite layer geometries. Two examples of shielding films with ultralow reflection frequencies, one for 39 and 52 GHz 5G telecommunication bands and the other for 60 and 77 GHz autonomous radar bands, are presented. The remarkably low reflectance and thinness of the proposed films provide an important advancement toward the commercialization of EMI shielding materials for 5G mmWave applications.

Fabrication of an Ultralight Ni-MOF-rGO Aerogel with Both Dielectric and Magnetic Performances for Enhanced Microwave Absorption: Microspheres with Hollow Structure Grow onto the GO Nanosheets

An ultralight Ni-MOF-rGO aerogel which possess the merits of not only broad bandwidth and strong absorption but also lightweight and thin matching thickness is fabricated through a hydrothermal treatment, freeze-drying, and annealing procedure. The Ni@C microspheres are dispersed randomly and evenly on the graphene oxide (GO) nanosheets, which can be proved through SEM and TEM results. The electromagnetic parameters of the composite can be adjusted by changing the mass ratio of the MOF and GO to endow the material with both good impedance matching and superior electromagnetic wave absorption performances. Consequently, the resulting composite shows outstanding microwave absorption performance, which achieves strong absorption (-51.19 dB) and broad effective absorption bandwidth (6.32 GHz) with a thickness of 1.9 mm while the filling content is only 2 wt %. In addition, the multiple loss mechanisms of the Ni-MOF-rGO aerogel are illustrated, including conduction loss, dipolar polarization, interfacial polarization, magnetic resonance, and eddy current loss. In a word, the extraordinary microwave absorption performance is ascribed to the synergistic effects of the unique multiple layered structure of GO and the hollow core-shell structure of the Ni@C microsphere. This work demonstrates that the ultralight aerogel with excellent electromagnetic wave absorption performance is a promising strategy for microwave absorption application.

3D Printed Integrated Gradient-Conductive MXene/CNT/Polyimide Aerogel Frames for Electromagnetic Interference Shielding with Ultra-Low Reflection

Construction of advanced electromagnetic interference (EMI) shielding materials with miniaturized, programmable structure and low reflection are promising but challenging. Herein, an integrated transition-metal carbides/carbon nanotube/polyimide (gradient-conductive MXene/CNT/PI, GCMCP) aerogel frame with hierarchical porous structure and gradient-conductivity has been constructed to achieve EMI shielding with ultra-low reflection. The gradient-conductive structures are obtained by continuous 3D printing of MXene/CNT/poly (amic acid) inks with different CNT contents, where the slightly conductive top layer serves as EM absorption layer and the highly conductive bottom layer as reflection layer. In addition, the hierarchical porous structure could extend the EM dissipation path and dissipate EM by multiple reflections. Consequently, the GCMCP aerogel frames exhibit an excellent average EMI shielding efficiency (68.2 dB) and low reflection (R = 0.23). Furthermore, the GCMCP aerogel frames with miniaturized and programmable structures can be used as EMI shielding gaskets and effectively block wireless power transmission, which shows a prosperous application prospect in defense industry and aerospace.

Core-Shell Structured SiO2@NiFe LDH Composite for Broadband Electromagnetic Wave Absorption

In this work, a novel core-shell structure material, NiFe layered double hydroxide (NiFe LDH) loaded on SiO2 microspheres (SiO2@NiFe LDH), was synthesized by a one-step hydrothermal method, and the spontaneous electrostatic self-assembly process. The morphology, structure, and microwave absorption properties of SiO2@NiFe LDH nanocomposites with different NiFe element ratios were systematically investigated. The results show that the sample of SiO2@NiFe LDH-3 nanocomposite has excellent microwave absorption properties. It exhibits broadband effective absorption bandwidth (RL < −10 dB) of 8.24 GHz (from 9.76 GHz to 18.0 GHz) and the reflection loss is −53.78 dB at the matched thickness of 6.95 mm. It is expected that this SiO2@NiFe-LDH core-shell structural material can be used as a promising non-precious, metal-based material microwave absorber to eliminate electromagnetic wave contamination.

In Situ Synthesis of C-N@NiFe2O4@MXene/Ni Nanocomposites for Efficient Electromagnetic Wave Absorption at an Ultralow Thickness Level

Recently, the development of composite materials composed of magnetic materials and MXene has attracted significant attention. However, the thickness and microwave absorption performance of the composite is still barely satisfactory. In this work, the C-N@NiFe₂O₄@MXene/Ni nanocomposites were successfully synthesized in situ by hydrothermal and calcination methods. Benefiting from the introduction of the carbon-nitrogen(C-N) network structure, the overall dielectric properties are improved effectively, consequently reducing the thickness of the composite while maintaining excellent absorption performance. As a result, the minimum reflection loss of C-N@NiFe₂O₄@MXene/Ni can reach -50.51 dB at 17.3 GHz at an ultralow thickness of 1.5 mm, with an effective absorption bandwidth of 4.95 GHz (13.02-18 GHz). This research provides a novel strategy for materials to maintain good absorption performance at an ultralow thickness level.

The Influence of Textile Substrates on the Performance of Textronic RFID Transponders

Recent advances in the development of innovative textronic products are often related to the implementation of radio-frequency identification (RFID) technology. Such devices contain components of wireless telecommunications systems, in which radiofrequency circuits should be designed taking into account not only the frequency band or destined application, but also the dielectric properties of the materials. As is known from the theory of RFID systems, the dielectric permittivity and loss angle of the substrates significantly affect the performance of RFID transponders. Therefore, the knowledge on the variability of these parameters is highly important in the context of developing new solutions in textronic devices with the RFID interface. According to the plan of studies, at the beginning, the comprehensive characterization and determination of the dielectric parameters of various types of textile substrates were carried out. On this basis, the influence of fabrics on the performance of textronic RFID (RFIDtex) tags was characterized with numerical calculations. As the RFIDtex transponders proposed by the authors in the patent PL231291 have an outstanding design in which the antenna and the chip are located on physically separated substrates and are galvanically isolated, the special means had to be implemented when creating a numerical model. On the other hand, the great advantage of the developed construction was confirmed. Since the impedance at the chip's terminals is primarily determined by the coupling system, the selected fabrics have relatively low impact on the efficiency of the RFIDtex transponder. Such an effect is impossible to achieve with classical designs of passive or semi-passive transponders. The correctness of the simulations was verified on the exemplary demonstrators, in threshold and rotation measurements performed at the laboratory stand.