Microwave Absorption Research Articles

Multi-material fused deposition modelling of structural–functional integrated absorber with multi-scale structure possessing tunable broadband microwave absorption

Designing and manufacturing advanced structural microwave absorbers is one of the most feasible methods to address the growing electromagnetic stealth and protection challenges in both military and civilian domains. To this end, under the application context of structural–functional integration, a series of nanocomposites with varying ratios were prepared using multi-walled carbon nanotubes (MWCNTs) and inexpensive thermoplastic polypropylene as raw materials. The dispersion of nanofillers, rheological properties, thermal properties, and mechanical properties were evaluated. The research found that the impedance matching factor of the electromagnetic wave absorbers plays a more critical role in determining the material’s absorption capacity compared to the loss factor. Simple structural layering by changing the composition and design can effectively increase the effective absorption bandwidth (EAB) of the absorbers, with microwave attenuation primarily arising from conductive loss, interfacial polarization, dipole polarization, and multiple reflections. Finally, a multi-scale quasi-honeycomb absorber was fabricated using multi-material 3D printing with a structured design. Both simulation and experimental results showed consistent trends, demonstrating low sensitivity to the incident azimuth angle. This research features simplicity, low cost, and strong design capability, providing a new strategy for the preparation of functionally graded materials with potential applications in electromagnetic wave absorption.

Multi-heterogeneous interfaces boost dielectric polarization in PBA-derived Co/MnO@NC ternary composites for electromagnetic wave absorption

The elaborate construction of multi-component composites has been deemed as a promising strategy to enhance dielectric polarization response capability in the preparation of highly efficient microwave absorbers. However, the rational design and integration of homogeneous composites with diverse components continues to pose a great challenge. Herein, we propose a straightforward self-assembly-carbonization strategy for fabricating Co/MnO@NC ternary composites derived from CoMn-Prussian Blue Analogous precursors, featuring enriched heterogeneous interfaces and balanced magneto-electric coupling synergy. The ternary composites effectively introduce diverse dissipation mechanisms, including interfacial polarization behavior originated from the constructed heterogeneous interfaces, dipole polarization relaxation triggered by atomic defects, and optimized magnetic loss ability from well-dispersed metallic Co species. Benefiting from these advantages, the Co/MnO@NC composites demonstrate superior electromagnetic wave absorption performances, with a minimum reflection loss value of −61.37 dB at the thickness of 3.5 mm and effective frequency absorption bandwidth of 6.32 GHz, covering the full Ku-band. Furthermore, power loss density and radar cross-section simulations validate that the Co/MnO@NC ternary composites possess exceptional microwave signal attenuation abilities, with a maximum radar cross-section reduction value of up to 27.98 dBm2 at 0°. Such outstanding absorption properties exceed those of most currently reported ternary composites and exhibit significant potential to replace conventional ferromagnetic-based absorbers. This work offers a straightforward strategy to fabricate ternary composites with excellent electromagnetic wave attenuation properties and sheds novel insights into the dissipation mechanisms.

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 6.24GHz (11.76-18.00GHz) at a thickness of only 2.34mm, covering 100% of the Ku band. The minimum reflection loss of -73.05dB can be demonstrated at a thickness of only 2.29mm, while at the same time showing an EAB of 5.96GHz 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.

Hierarchical porous molybdenum carbide synergic morphological engineering towards broad multi-band tunable microwave absorption

Hierarchical porous molybdenum carbide synergic morphological engineering towards broad multi-band tunable microwave absorption

Fabrication of MXene-encapsulated Co@C nanoparticles for efficient microwave absorption in the X-band

Two-dimensional MXene has structural advantages in electromagnetic wave scattering due to its layered structure, but MXene materials can lead to impedance mismatch problems due to their high dielectric constants, so it is still a challenge to design highly efficient wave-absorbing materials based on MXene with low reflection loss, thin thickness, and wide absorption frequency. In this study, composite wave-absorbing materials were fabricated from Co–Co PBA precursors and MXene using liquid nitrogen flash freezing and freeze-drying techniques. By treating MXene and the PBA precursor at a high temperature of 750 °C, a rich heterogeneous interface was formed between Co@C and MXene (CCM7), and the impedance matching was optimized to improve the reflection loss capability. The optimized sample has an effective absorption bandwidth of 4.1 GHz at 2.5 mm covering the entire X-band with a minimum reflection loss of −61.42 dB. It is also demonstrated that CCM7 is satisfactory for Radar Cross-Section of flat panels and unmanned aerial vehicles by CST calculations, and this work provides a fresh perspective on the use of effective MXene composites for microwave absorption.

Conjugated Matrix Nanocomposites with Nanodiamond Nanoadditives—Fundamentals and Forefronts

Nanodiamonds have been researched as sphere-shaped carbon nano-entities having countless surface/structural properties, facile fabrication and mammoth technological value. An important utilization of nanodiamonds has been observed as nano-reinforcing agents for nanocompositing purposes. Semiconducting polymers (conjugated polymers) having π electron delocalization have been documented for worthy electrochemical/optical/thermal/mechanical features, in addition to the electron transfer through their backbone. Doping of carbonaceous nanoparticles, like nanodiamonds, with conjugated polymers have been found to further improve the valuable physical characteristics in their final nanocomposite form. Correspondingly, this overview describes the impact of nanodiamond nano-reinforcement on the specialized aspects of polyaniline/nanodiamond, polypyrrole/nanodiamond and polythiophene/nanodiamond nanocomposites. According to literature reports, these groupings of conjugated polymer/nanodiamond hybrids revealed noteworthy microstructural, conductive, optical, electrochemical, microwave absorption, specific capacitance, photovoltaic and actuation characteristics. Subsequently, several significant applications of polymer/nanodiamond nanomaterials have been explored including the solar cells, supercapacitors and actuators.

Capping Agent–Induced ZIF-8-Based ZnO/Magnetic Carbon Nanocomposites for Enhanced Broadband Microwave Absorption

Capping Agent–Induced ZIF-8-Based ZnO/Magnetic Carbon Nanocomposites for Enhanced Broadband Microwave Absorption

Preparation of M-type barium ferrite submicron absorbing powder by one-step high-temperature ball milling and its particle structure regulation

This study investigates a simple and rapid process for directly preparing M-type barium ferrite using high-temperature ball milling. By adjusting the rotation speed of the high-temperature ball milling, the morphology and size of the powder can be altered to regulate its electromagnetic properties, aiming for an overall good absorbing effect. The powder’s morphology, agglomeration properties, elemental valence states, and electromagnetic parameters were characterized using SEM, BET, XPS, EDS, and VNA. The results show that as the milling speed increases, the particle size of the M-type barium ferrite decreases, transitioning from the typical hexagonal flake particles to spherical block particles, forming a porous loose structure with richer dielectric loss mechanisms and enhanced electromagnetic wave loss capacity. Electromagnetic loss performance analysis indicates that at a milling speed of 50 rpm, the powder achieves the best electromagnetic loss of −61.16 dB at a matching thickness of 8.77 mm and a microwave absorption bandwidth of 4.1 GHz.

A novel approach to obtain superior microwave absorption using Non-Conducting polymer jacket coated Multi-Layer Hexaferrite-TMDC nanocomposite film

This article represents the imposing electromagnetic interference (EMI) shielding behaviour of non-conducting polymer jacket-coated Co2Y-hexaferrite-MoS2 binary nanofillers incorporated PVDF multi-layer nanocomposite films. The presence of Co2Y-hexaferrite inside PVDF enhanced the magnetic permeability, whereas the incorporation of semiconducting transition metal dichalcogenide (TMDC), MoS2, inside the PVDF matrix improves the polarization effects of the nanocomposite films. The crystalline phases corresponding to Co2Y-hexaferrite, MoS2 nanoparticles and the multi-phase nanocomposite films have been justified using XRD analysis and Rietveld refinement study. FESEM micrographs confirm the hexagonal and cotton-ball structures of Co2Y-hexaferrite and MoS2 nanoparticles, respectively; in addition, the presence of Co2Y-MoS2 binary nanofillers inside the PVDF matrix has been confirmed. The stability of the nanocomposite films against electrical breakdown is clearly demonstrated by the minimum leakage current observed at 90 kV/m under J-E characteristics. The room temperature maximum magnetization of 33.32 emu/g of Co2Y-hexaferrite at an external magnetic field of 50,000 Oe helps in incurring magnetic losses and the corresponding improvement of shielding effectiveness due to absorption (SEA) of the nanocomposite films. This article demonstrates the modulation of SEA of the nanocomposite films depending on both the binary nanofillers loading percentage inside PVDF and the thickness of the nanocomposite films. Also, a unique mechanism corresponding to the coating of a non-conducting polymer jacket over a multi-layer structure has been opted herein to improve SEA in the frequency range of 12–18 GHz. This unique mechanism demonstrates that the maximum SEA for the non-conducting polymer jacket-coated multi-layer nanocomposite film is −51.23 dB at 14.03 GHz, and the corresponding total shielding effectiveness (SET) is −74.51 dB at 13.23 GHz, along with > 99.9999 % attenuation.

Ingeniously construction of industrial carbon fiber/nickel-iron layered double hydroxide heterostructure composite for high-efficient microwave absorption in aircraft

To enhance the survivability of military aircraft in electromagnetic warfare, carbon fiber/nickel-iron layered double hydroxide (CF/NiFe-LDH) composites with heterogeneous structure were constructed starting from the raw industrial carbon fiber (CF) by electrostatic self-assembly. By reasonably adjusting the mass ratio of CF and NiFe-LDH, the voids formed by LDH arrays stacked on the fiber surface are utilized to promote reflection and scattering of electromagnetic wave (EMW), optimizing impedance matching, as well as synergize dielectric-magnetic dual loss mechanism. Moreover, interfacial polarization effect induced by the abundant heterogeneous interfaces significantly enhance the ability of EMW dissipation. The optimized CF/NiFe-LDH heterostructure composite exhibits the minimum reflection loss (RLmin) value of −52.48 dB at mere 1.77 mm thickness and an expansive maximum effective bandwidth (EABmax) of 7.29 GHz at 2.14 mm. In addition, the computer simulation technology (CST) revealed that the radar scattering cross section (RCS) reduction of composites reaches up to 26.92 dBm2 at an incidence angle of 90°, demonstrating their excellent radar attenuation capability. Tremendously, the heterogeneous composites achieve an SRL1 value of 524.8, which is appreciably better than most of the EMW absorbing materials. The wondrous characteristics including lightweight, ultra-thin, high-efficient microwave absorbing ability of CF/NiFe-LDH heterostructure composites display potential application in fighter aircraft.

Strong and Tough Multilayer Heterogeneous Pyrocarbon Based Composites

AbstractThe integration of bio‐inspired hierarchical design into synthetic carbon materials holds promise for developing lightweight, high‐performance structural materials. Hierarchical and heterogeneous nanoscale units are crucial to load bearing and mechanical functionality yet receives limited attention for difficulties in accurate regulation. Herein, one kind of multilayered heterogeneous have proposed pyrocarbon based composite constructed through chemical vapor deposition method with nanoscale graphene orderliness regulation. Sequential construction from orientational graphene sheets to nondirective isotropic networks is achieved through controlling the size and morphology of pyrolysis intermediates with moderate oxidation, being expected to facilitate load transfer and structural stability through dynamically adjustment in heterogeneous interfacial sliding. The resulting multilayer heterogeneous phases exhibit impressive strengthening and toughening mechanisms dominated by microstructural multiscale coupling, which provides new solutions for developing structural composites for high‐temperature aerospace applications. Additionally, the multiple internal reflections arising from the abundant heterogeneous interfaces significantly improve the efficiency of electromagnetic microwave absorption. The multilayered heterogeneous interfaces achieved through orderliness manipulation offer novel insights into the assembly of mechanical functionality integration for wide‐temperature applications and high‐performance macroscopic carbon‐based composites.

Methodology for optimizing the radio absorption capacity and mechanical strength of composite structural materials

The possibility of impregnating high-strength fabrics under pressure with a modified binder is considered. The development of high-temperature composites that have not only high strength, but also microwave absorption properties is inextricably linked with new products being developed and the imposition of more stringent tactical and technical requirements on them. For the successful introduction of these composites into the field of mechanical engineering, one of the necessary conditions is the assessment of their stress-strain state at the design stage. This method allows producing the fabric for aircraft details with high strength. The purpose of the study is to evaluate the absorption of microwave waves and study the physical and mechanical characteristics of composites obtained by vacuum infusion.

Graphene/carbon nanotube aerogels with ultralow filling ratio through perfect cross-linking interface for efficient microwave absorption

Utilizing high-efficiency electrostatic assembly and a scalable freeze-drying technique followed by carbonization, we have developed a series of unique, lightweight, hierarchically porous 1D+2D aerogels containing carbon nanotubes (CNTs) and reduced graphene oxide (rGO). By manipulating the interaction between CNTs and graphene oxide perjurer in cellulose nanofiber (CNF), CNTs can uniformly distribute along the graphene cell walls via an exceptional cross-linking interface in the resultant rGO/CNT aerogels. This arrangement enables abundant heterogeneous interfaces, endowing the aerogels with high conductivity and polarization loss capacity. Moreover, the 1D+2D microstructure of CNT/rGO and the hierarchical pore architecture of the aerogels facilitate multiple scattering, further enhancing their loss capacity toward electromagnetic wave absorption (EMW). Coupled with the optimized impedance matching derived from the adjustable dielectric properties, the aerogels exhibit outstanding EMW absorption with a filling ratio of merely 2 wt%. Specifically, a minimum reflection loss (RLmin) of −49.61 dB and an effective absorption bandwidth (EAB) of 4.16 GHz are achieved. With a filling ratio of 3 wt%, the RLmin reaches −77.51 dB, accompanied by an EAB of 3.84 GHz, surpassing the reported carbon or graphene-based aerogel EMW absorbers. In this work, the ultra-low filling ratio resulting from high conductivity confers a practical design for fabricating lightweight carbon-based aerogels suitable for high-efficiency EMW absorption, manifesting multiple applications in electromagnetic compatibility and aerospace contexts.

Three-dimensional n-MoSe2/GOx (n= 1T, 1T' and 2H) microsphere: Phase-modulation strategy and microwave absorbing mechanism

MoSe2 was identified as a potential microwave absorber, whereas its practical application was predominantly affected by the ambiguous electromagnetic wave attenuation mechanism and dielectric properties. Here, we developed a novel phase assembly-modulating strategy to prepare n-MoSe2/GOx (n = 1T, 1T' and 2H) composites, wherein phase modulation of MoSe2 exerted a gainful effect on microwave absorption properties. The unique 1T′-MoSe2 phase was first explored in microwave absorption and composited with GOx to afford advanced conductivity loss and dielectric loss. The introduction of additional interface (2H/1T or 2H/1T') and abundant unsaturated defects promote multiple polarization, the semiconductor-metal mixed phase brought in a certain magnetic loss, optimizes the electron transfer ability and adjusts the impedance matching. Consequently, 1T′-MoSe2/GOx provides the minimum reflection loss (RLmin) of −52.08 dB and the effective absorption bandwidth (EAB, RL < -10 dB) of 5.3 GHz at 10 % filler content, which is approximately 9 times that of 2H–MoSe2/GOx and nearly 5 times that of 1T-MoSe2/GOx. This paper specifically explains the reasons for the phase modulation-induced magnetic losses and provides an effective phase modulation paradigm for developing advanced transition metal disulfide (such as MoS2, WS2 and WSe2) microwave absorbers.

Synergistic effects of nitrogen/oxygen co-doping in 3D mesoporous carbon nanospheres for enhanced microwave absorption

Mesoporous carbon nanospheres have attracted significant attention in the microwave absorption (MA) field due to the broad benefits provided by their mesoporous structure. This study presents a facile hard template strategy to construct distinctive 3D N/O co-doped mesoporous carbon nanospheres (NOCS). The high surface area, abundant mesopores, and high nitrogen (N) doping levels, with proper defects on the surface provide multiple sites to absorb electromagnetic waves (EMW). Mesoporous carbon nanospheres achieve significant reflection loss (RL) of −48.19 dB and extensive effective absorption bandwidth (EAB) up to 5.52 GHz. Moreover, computer simulation technology (CST) demonstrated that all simulated Radar cross-section (RCS) values were below 20 dB m2. Thus, this work holds significant promise for effective microwave absorbers using mesoporous carbon nanospheres.

Facile process for cost-effective layer-by-layer rGO/SiO2 structure for high microwave absorption

This study introduces a cost-effective and eco-efficient method for fabricating an advanced microwave absorber using a layer-by-layer rGO and SiO2 structure. The rGO/SiO2 composite, synthesized via modified Hummer's and Stöber methods, demonstrates remarkable microwave absorption properties. The resultant porous structure, characterized by an SBET of 294.89 m2/g, enables multiple reflections and scatterings of electromagnetic waves. At a sample thickness of 3.8 mm, the material achieves a reflection loss (RL) of −47.43 dB at 12.56 GHz and an effective absorption bandwidth (EAB) of 11.04 GHz. For a 6 mm thick sample, an exceptionally high EAB of 12.72 GHz is observed, maintaining a high RL of −42.32 dB. These results demonstrate that the rGO/SiO2 material is a promising candidate for applications in electromagnetic wave absorption, offering a simple, scalable solution for mitigating electromagnetic pollution and enhancing military stealth technologies.

Multifunctional microwave absorption materials: construction strategies and functional applications.

The widespread adoption of wireless communication technology, especially with the introduction of artificial intelligence and the Internet of Things, has greatly improved our quality of life. However, this progress has led to increased electromagnetic (EM) interference and pollution issues. The development of advanced microwave absorbing materials (MAMs) is one of the most feasible solutions to solve these problems, and has therefore received widespread attention. However, MAMs still face many limitations in practical applications and are not yet widely used. This paper presents a comprehensive review of the current status and future prospects of MAMs, and identifies the various challenges from practical application scenarios. Furthermore, strategies and principles for the construction of multifunctional MAMs are discussed in order to address the possible problems that are faced. This article also presents the potential applications of MAMs in other fields including environmental science, energy conversion, and medicine. Finally, an analysis of the potential outcomes and future challenges of multifunctional MAMs are presented.

The effect of conduction loss on microwave absorption performance of Fe-doped NiCo2O4 spinel oxide

Strong absorption and large bandwidth are two contributors to material’s electromagnetic wave absorbing performance. While spinel ferrite materials have garnered extensive attention in the realm of microwave absorption, their relatively low conductivity remains a practical challenge.In this work, NiCo2-xFexO4 (x = 0, 0.04, 0.06 and 0.08) precursor was prepared by hydrothermal and after-sintered method. It was found that Fe doping exhibit excellent EM absorption properties. Specially, when the Fe content is 0.08, the maximum reflection loss −48.90 dB at 15.40 GHz and the maximum effective bandwidth 4.20 GHz are achieved. More importantly, the absorption frequency can be broadened from Ku to C band even to S band with proper adjusting Fe content. Doping with Fe enhances conduction loss and make a significant contribution to dielectric loss, as a result, the impedance matching degree of the Fe-NiCo2O4 composite is influenced by the synergistic effect of its dielectric and magnetic properties. This work provides a simple way for enhancing the microwave absorption capabilities of ferrite materials and provides insight into understanding conduction loss in microwave absorption.

Multi-scale structural design of multilayer magnetic composite materials for ultra-wideband microwave absorption

Broadband microwave absorbing (MA) materials have important applications in reducing electromagnetic radiation pollution and realizing low scattering characteristics. However, current MA materials with single-layer structure generally cannot meet this requirement due to the difficulty in achieving good impedance matching. Here, we design a multilayer-structured MA material, which consists of a wave transmitting layer, a carbon-magnetic material composite absorbing layer, a strong magnetic absorbing layer and a reflector layer. Hollow Co/CoFe@C composite particles prepared using CoCoPBA as templates are used as fillers to design carbon-magnetic material composite absorbing layer. The Co/CoFe bimagnetic phases enhance permeability while the hollow structure optimizes permittivity, which endows this absorbing layer with strong microwave absorption ability with a reflection loss of −47.18 dB. The introduction of a strong magnetic absorbing layer that combines FeSiAl with high permeability and SmFeB with high coercivity further significantly improves the overall impedance matching of the material. Benefitting from the multi-scale structural design, the obtained multilayer MA material achieves strong microwave absorption in both low and high frequency ranges, and the effective absorption bandwidth reaches 12.85 GHz, far superior to the traditional single-layer MA material.

Microwave absorption performance of La1.5Sr0.5NiO4/SrFe12O19 composites with thin matching thickness

The global focus on electromagnetic interference and pollution is undeniable. To counter these challenges, high-performance microwave-absorbing materials (MAMs), typically composed of dielectric and magnetic components, offer effective solutions by ensuring favorable impedance matching. Leveraging these MAMs has proven beneficial across various sectors, including 5G technology, information security, energy harvesting, diminished radar cross-section, and advancements in military applications. We successfully synthesized composites of La1.5Sr0.5NiO4 (LSNO) and SrFe12O19 (SrM) composites through ball milling and heat treatment. With the escalation of SrM weight percentage in the composites, noticeable alteration in structural, morphological, and static magnetic characteristics was ensured.Moreover, the amalgamation of these components bolstered the EM properties, consequently yielding exceptional microwave absorption capabilities in the composites. The composites with 40, 60, and 80 wt% of SrM (named S4, S6, and S8) exhibited excellent microwave absorption performance with an absorption rate of over 99.9 % for a thin thickness. The S4 and S8 composites attained reflection loss (RL) values of −34.75 dB and −36.93 dB, with 2.0 and 1.6 mm thicknesses, respectively. Meanwhile, the S6 composite achieved an RL value of −44.24 dB with a thickness of 1.9 mm. These composites' outstanding microwave absorption performance can be attributed to their significant magnetic loss, remarkable dielectric loss, and synergistic effects.