Efficient Microwave Absorption Research Articles

Design of BCNO@PPy composites for efficient microwave absorption and thermal management

Currently, multifunctional microwave-absorbing materials, especially those with thermal conductivity and microwave absorption functions, have excellent application prospects in electronic packaging. In this study, we first used a sacrificial template method to prepare BCNO using biomass carbon as a template. Then, we used an in-situ synthesis method to grow polypyrrole (PPy) on the surface of BCNO to prepare BCNO@PPy with a core-shell structure. The BCNO@PPy composite exhibits a minimum reflection loss (RLmin) of −52.6 dB at a thickness of only 1.94 mm and an effective absorption bandwidth (EAB) of 5.3 GHz (12.7–18 GHz). The excellent microwave absorption can be attributed to the synergistic effect of polarization loss, conductive loss, and partial magnetic loss in the BCNO@PPy (BPPy) composites, and the multi-wall reflection effect of the core-shell structure, as well as the excellent impedance matching of the composites. Notably, BPPy-3 (polypyrrole content of 28.5 wt%) showed a good thermal conductivity enhancement effect on the epoxy resin (EP) when the content of BPPy-3 was 30 wt%. BPPy-3/EP has a thermal conductivity of 1.82 W(m·K)−1, which is 619.5 % higher than that of pure EP. The good thermal conductivity of the composites is attributed to the excellent compatibility of PPy and epoxy resin, as well as the low interfacial thermal resistance between BCNO and PPy. Therefore, this work can provide a reference for the design of materials with both thermal conductivity and microwave absorption functions.

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.

Multi-functional phase for precision sampling resistors for HVDC voltage transformer and efficient microwave absorption

Precision resistor performance has a direct impact on the detection accuracy of DC voltage transformers since it is a crucial component for signal sampling in high-voltage DC (HVDC) voltage transformers. The accuracy of the resistance is directly related to the performance of the slurry, which is sintered to produce the resistance. In this article, two different kinds of conductive fillers carbon-based and metal-based were created using the hydrothermal technique and high-temperature carbonization, and the matching resistance slurry and thick film resistors were made by compounding glass powder and organic carriers. The findings demonstrate the resistance slurry prepared using copper nanopowder as a conductive filler can achieve lower square resistance values and can be adjusted within the range of 124 Ω/□ -1503 Ω/□ by changing the solid content, and the square resistance is less affected by temperature. It can be used as a precision resistor for preparing high-voltage DC voltage transformers. Furthermore, the prepared functional phase materials also exhibit satisfying microwave absorption performance. Typically, the copper nanopowder exhibits the RLmin of -23.77dB and the EABmax of 4.64GHz at 1.8mm. This work provides a reference for the application of functional phases in electronic slurry and microwave absorption fields.

Zn-MOF-derived hierarchical carbon nanorods superstructures with tunable microwave absorption properties

Nanometer/micron scale multilevel superstructure has the potential to be a good microwave absorbing (MWA) materials owning to its large specific surface area and good electrical conductivity, but assemble 1D rod/wire-like into a three-dimensional (3D) hierarchical superstructure with a large controllable radius of curvature spherical tissue, is still a challenge. Here we demonstrate a self-templated strategy through pyrolysis the modulator (urea) modified Zn-MOF 74 to obtain the spherical superstructure of carbon nanorods (SSC). The dielectric constant of SSC absorbers regulated by the amount of urea added. A moderate amount of urea will endow the material a high specific surface area and defect-induced mesopore, thus the excellent MWA properties. The prepared SSC-U2 has a good MWA performance that the minimum reflection loss (RL, min) can reach -54 dB only when the thickness is 2.1 mm. This work designs a new strategy to prepare the 3D hierarchical superstructure carbon by using MOFs and offers insight into the relationship between morphology, surface area and dielectric constant of absorber, promoting rational design of highly efficient microwave absorber.

Incorporating Loss Factor Modular Design for Full Ku-Band Microwave Attenuation in Double-Layered Graphene Aerogels.

The fabrication of absorption-dominant electromagnetic interference (EMI) shielding materials is a pressing priority to prevent secondary electromagnetic pollution in miniaturized electronic devices and communication systems. Meeting this goal has remained a tough challenge to keep pace with the rapid evolution of electronics due to the complex compositional and structural design and narrow operating bands. This work articulates a sound and simple strategy to precisely modulate the electrical conductivity of reduced graphene oxide (rGO), as the building block in lightweight double-layered rGO-film/rGO-aerogel/polyvinyl-alcohol (PVA) composites, for efficient microwave absorption over the entire Ku-band frequency range. These constructs reasonably comprised a porous absorption structure built from parallel rGO sheets aligned and prepared via freeze casting followed by freeze drying. The electrical conductivity and impedance of this layer were tuned by varying the annealing temperature from 400 to 800 °C, thereby adjusting the degree of reduction and the absorption characteristic. This layer was backed by a highly conductive rGO film reduced at a high temperature of 1000 °C, with a reflectivity of 97.5%. The incorporation of this film ensured high EMI shielding effectiveness of the double-layered structure through the absorption-reflection-reabsorption mechanism, consistent with the predicted values based on calculated loss factors and the input impedance of the structure. Accordingly, at an average EMI shielding effectiveness of 57.59 dB, the reflection shielding effectiveness (SER) and reflectivity (R) of the assembled composites were optimized to be as low as 0.22 dB and 0.049, respectively. This equates to approximately 99.999% shielding (SET) and ∼95% absorptivity (A) of the incident wave. This study opens new avenues for the development of lightweight (with a density as low as 15 mg/cm3) absorption-dominant EMI shielding composite materials with promising EMI shielding efficiency and potential applications in modern electronics.

Tunable microstructure and microwave absorption properties of the SmCo5/Sm2Co17 binary-phase magnetic absorbent prepared via a reduction diffusion method

Magnetic materials with highly efficient microwave absorption properties, crucial for dealing with the advanced wireless communications and radar detections, have been garnering significant attentions. Rare-earth transition-metal compounds were researched as the potential candidates but still suffer from the disadvantages of complex powder metallurgy process and low serving frequencies. In this work, the novel magnetic composites consisting of SmCo5 and Sm2Co17 are developed by a reduction diffusion method. The micromorphology and the binary phase ratios of the SmCo5/Sm2Co17 could be easily modulated by simply altering the reactant concentrations. Consequently, an optimum reflection loss of − 50.2 dB and broad absorption bandwidth of 4.95 GHz at a thickness of only 2.0 mm are achieved. The improved microwave absorption properties of the SmCo5/Sm2Co17 binary-phase magnetic absorbents can be attributed to their adjustable magnetic phases and the distinctive flaky particle shape, which greatly enhance microwave absorption capabilities. This work demonstrated a feasible reduction diffusion method and proposed a new strategy of designing binary-phase magnetic materials to achieve high microwave absorption properties.

Construction of multi-interface PDA-NiCo2S4 nanomaterials for synergistic design of efficient microwave absorption and anti-corrosion effects

The modern and complex environment requires microwave absorbing materials (MAMs) that can cope with environmental changes. In particular, the high humidity, high salt spray and high temperature of the marine environment conditions have been the toughest. Consequently, the development of integrated materials with both microwave absorption (MA) and corrosion resistance has emerged as a top priority. In this work, spherical NiCo2S4 (NCS) particles with stable size were prepared by a simple solvothermal method. Furthermore, the self-polymerization of dopamine (PDA) on the surface of NCS was achieved by exploiting the film-forming ease of dopamine. A series of PDA-NCS particles with different interfaces were fabricated by tuning the ratio of NCS and dopamine. The integrated magneto-electric drive synergy enhances the impedance matching. Multiple heterogeneous interfaces enhance the depletion efficiency of electromagnetic waves (EMWs) within the material. The samples designed have achieved an effective absorption bandwidth (EAB) value of 6.26 GHz and a maximum reflection loss value of −22 dB at a low thickness of 1.7 mm. Meanwhile, due to the electrochemical protection reaction of anode of metal and the passivation effect of barrier by PDA. The prepared coatings maintained favorable corrosion resistance in 240 h of continuous salt spray environment. Moreover, after the 240 h salt spray experiment, the sample realized the EAB value of 4.77 GHz at a thickness of 1.7 mm. This work breaks new ground for the development of absorbing and anti-corrosion integrated materials.

ZIF-67 derived Co@carbon nanotubes anchored on carbon fiber for efficient microwave absorption and mechanical enhancement

Rational design of multifunctional and high-performance electromagnetic wave (EMW) absorbers is highly desirable but still remains a challenge. Herein, the 3D heterostructural Co@carbon nanotubes/carbon fiber (Co@CNTs/CF) hybrids derived from ZIF-67/CF were successfully fabricated via the in-situ synthesis of ZIF-67 on CF and subsequent catalytic chemical vapour deposition. Intriguingly, the as-obtained composites acquire adjustable EMW absorption and favorable mechanical properties simultaneously. Specifically, taking advantage of adequate conductive paths, plentiful heterogeneous interfaces, suitable defect vacancies, appropriate magnetic loss, as well as optimized impedance matching, Co@CNTs/CF delivers a brilliant EMW absorption intensity of −45.11 dB at only 1.15 mm together with a broad effective absorption bandwidth (EAB) of 4.0 GHz (1.23 mm), and an unexpected minimal reflection loss up to −65.63 dB (3.84 GHz) coupled with an EAB of 3.6 GHz at merely 1.09 mm, respectively. In addition, the tunable EAB can be achieved in 2.6–18 GHz, covering 96 % of the test frequency by changing the absorber thickness from 0.93 to 5.0 mm (29 wt%). Moreover, the maximum radar cross section reduction can reach 48.8 dBm2. The uniform layer of CNTs with moderate crystallinity also enables Co@CNTs/CF to improve the tensile strength and Weibull modulus compared to unsized CF. This study paves a novel avenue for developing multifunctional materials based on CF through an efficient, controllable and low-cost approach.

Rational design of size-controlled spongy porous carbon microspheres with wide-frequency microwave absorption properties

Porous carbon materials have garnered significant attention due to their effective microwave absorption properties. However, the design and preparation of precisely size-controlled porous carbon materials is still a great challenge. Spongy porous carbon microspheres (SPCMs) with adjustable size and uniform particles were successfully synthesized for large-scale production. This synthesis method employed affordable polymethyl methacrylate (PMMA) microspheres as sacrificial templates and phenolic resin oligomers as carbon sources. In addition to size considerations, different carbonization temperatures exert substantial influence on the complex dielectric constant and microwave absorption characteristics. SPCMs samples, characterized by a size of 5 μm and carbonization temperature of 700 °C, exhibited exceptional microwave absorption performance, despite a loading of only 10 wt%. The minimum reflection loss (RLmin) for the matched 2.6 mm thick sample reached −68.2 dB at 15.0 GHz, and the effective absorption bandwidth (EAB) for the matched 2.9 mm thick sample spanned 7.5 GHz. The outstanding microwave absorption capabilities of SPCMs can be attributed to their continuous porous structure, well-suited impedance matching, appropriate conductivity, and abundant interfacial polarization. This work serves as a crucial guide for the development of highly efficient microwave absorbers characterized by thin profiles, lightweight composition, strong absorption characteristics, and a wide EAB.

Tailoring of electromagnetic properties of arc-produced carbon-coated FeNi alloy nanocapsules for highly efficient microwave absorption

Due to the growing harm of electromagnetic radiation, it is extremely urgent to develop high-efficiency microwave absorbers with tunable electromagnetic properties. Herein, a simple strategy for synthesizing hetero-atoms (sulfur) doped carbon-coated FeNi alloy nanocapsules (FeNi@C(Sx) NCs) by DC arc-discharge plasma was demonstrated. The hetero-interface between the FeNi alloy core and the graphitic shell induce interfacial polarization was found. Meantime, many defects produced by substitutional sulfur atoms in the graphitic shell facilitated dipole polarization and conduction loss. Besides, the multiple magnetic resonance produced by FeNi magnetic alloys worked together to optimize impedance matching. The excellent microwave absorption performance was attributed to the core-shell structure, dipole and interface polarizations, as well as favorable impedance matching. Importantly, the first-principles calculation was applied to prove the charge transfer and polarization process. The minimum reflection loss (RL) can reach up to −50.3 dB at a thickness of 1.6 mm.

3D Honeycomb Fe/MXene Derived from Prussian Blue Microcubes with a Tunable Structure for Efficient Low-Frequency and Flexible Electromagnetic Absorbers.

The unique layered structure and high conductivity of MXene materials make them highly promising for microwave absorption. However, the finite loss mechanism and severe agglomeration present challenging obstacles for ideal microwave absorbers, which could be effectively improved by constructing a three-dimensional (3D) porous structure. This study reports a 3D honeycomb MXene using a straightforward template method. The 3D MXene framework offers ample cavities to anchor the Prussian blue microcubes and their derivatives including Fe microboxes and Fe clusters by a simple annealing process. Based on the superiority of the 3D honeycomb architecture and magnetic-dielectric synergistic effects, the Fe/MXene absorbers demonstrate outstanding microwave absorption capabilities with the optimum reflection loss value of -40.3 dB at 2.00 mm in the low-frequency range from 4.2 to 5.6 GHz. The absorber also manifests superior radar wave attenuation by finite element analysis and exhibits great potential to be a flexible and thermal insulation material in a wide range of temperatures. This work proposes a useful reference for the design of 3D MXene-based porous architectures, and the synergistic magnetic-dielectric strategy further expands the potential of MXene-based absorbers, enabling them to be used as flexible and highly efficient microwave absorbers.

Multifunctional MnFe2O4/TiO2/Ti3C2Tx composites based on in-situ grown TiO2 for efficient microwave absorption, high hydrophobicity, and heat dissipation properties

Despite the fact that the 2D structure Ti3C2Tx with abundant defects and functional groups contributes to the high microwave absorption (MA) performance, it is difficulty to improve the strength and bandwidth by pursuing higher conductivity or loading more groups due to the limitation of intrinsic properties. Therefore, it is important to ingeniously design efficient Ti3C2Tx based MA composites assembling the features of abundant surface groups, good dispersibility, multiple composition, and precise structure. Inspired by the fact that Ti3C2Tx contains thermodynamically metastable marginal Ti atoms, TiO2 nanoparticles can be grown in-situ on Ti3C2Tx nanosheets uniformly and increase the spacing of Ti3C2Tx layers, and then MnFe2O4 nanoparticles are introduced into the layers of Ti3C2Tx by electrostatic self-assembly method for optimized impedance matching. This designed hierarchical MnFe2O4/TiO2/Ti3C2Tx composites shows excellent MA performance, and the minimum reflection loss (RLmin) reaches −46.91 dB with a thickness of 2.5 mm at frequency of 10.4 GHz. The high MA performance mainly comes from the enhanced interfacial polarization induced by edges location and interface region among TiO2, MnFe2O4, and Ti3C2Tx. In addition, the conduction loss existed in the interior untreated Ti3C2Tx, the dielectric loss generated by multiple composition, the multiple scattering from improved large surface specific area all contribute to the excellent MA performance. Meanwhile, the simple preparation process and good stability storage at room temperature under air atmosphere of the MnFe2O4/TiO2/Ti3C2Tx composites promote its exploration on practical use, and the lab-gown cloth coated with MnFe2O4/TiO2/Ti3C2Tx composites shows better electromagnetic shielding properties, hydrophobicity, and heat transfer ability than pure fabric, showing the potential for practical application.

Magnetic-dielectric synergistic construction of Ni-doped Ti3AlC2 achieving efficient microwave absorption

Doping can introduce diverse interfaces and optimize impedance matching, making it a significant approach for enhancing the substrate's microwave absorption performance (MAP). Herein, a novel Ni-doped Ti3AlC2 composite (xNi-Ti3AlC2; x = 0, 0.1, 0.2, 0.3) is successfully fabricated using pressureless sintering method. Partial replacement of Al atoms with doped Ni atoms leads to an improvement in permeability. Simultaneously, the substitution of Ni for Al and the formation of metal oxides (such as Al2O3, NiO, etc.) weaken the construction of conductive network, resulting in reduced conductivity and permittivity. The magnetic-dielectric synergistic effect significantly improves the impedance matching of Ti3AlC2. Furthermore, the presence of multiphase interfaces and heightened defects results in an augmentation of both interfacial polarization and dipole polarization. Consequently, the 0.2Ni-Ti3AlC2 demonstrates an outstanding MAP, with a minimum reflection loss (RLmin) of -48.73 dB at 14.33 GHz and an effective absorption bandwidth (reflection loss < -10 dB) of 4.38 GHz (11.43-15.81 GHz) at a thickness of 1.72 mm, surpassing that of Ti3AlC2. Moreover, the 0.1Ni-Ti3AlC2 achieves a RLmin of -65.07 dB, which is 4.24 times that of Ti3AlC2. This study provides a valuable reference for assisting in the design and development of an absorber that capitalizes on magnetic-dielectric synergistic effect.

MOF-derived multicore-shell Fe3O4@Fe@C composite: An ultrastrong electromagnetic wave absorber

Excessive artificial electromagnetic radiation poses significant health risks and disrupts military equipment. To address this, high-performance microwave absorption materials are urgently required. While ferromagnetic materials have excellent absorption but suffer from high density, limited bandwidth, and perishable properties. Carbon materials, especially metal-organic frameworks (MOFs), offer promise due to low density, chemical stability, and high conductivity. In this study, we synthesized a novel multicore-shell Fe3O4@Fe@C composite via solvothermal and in-situ pyrolysis methods. This composite integrated Zn-MOF-derived porous carbon with core-shell Fe3O4@Fe@C, enabling multiple electromagnetic wave routes, strong interfacial polarization, and magnetic-dielectric synergy. It exhibited exceptional electromagnetic wave absorption, with a −59.1 dB reflection loss at 13.36 GHz and a 5.36 GHz effective absorption bandwidth. Our innovative MOF-core-shell approach holds great promise for highly efficient microwave absorbers to mitigate artificial electromagnetic radiation's adverse effects on health and military equipment.

Design and synthesis of core–shell porous magnetic nanospindle@poly(3,4-ethylenedioxythiophene)/MXene composite for efficient microwave absorption

Design and synthesis of core–shell porous magnetic nanospindle@poly(3,4-ethylenedioxythiophene)/MXene composite for efficient microwave absorption

Bimetallic nanocubes embedded in biomass-derived porous carbon to construct magnetic/carbon dual-mechanism layered structures for efficient microwave absorption

Biomass-derived porous carbon materials have great potential for the development of lightweight and efficient broadband microwave absorbers. In this study, we reported the successful immobilization of Co3O4/CoFe2O4 nanocubes on porous carbon derived from ginkgo biloba shells by activated carbonization and electrostatic self-assembly processes. The optimal reflection loss value of the prepared BPC@Co3O4/CoFe2O4 reaches −68.5 dB when the filling load is 10 wt%, and the effective absorption bandwidth is 6.2 GHz with a matching thickness of 2 mm. The excellent microwave absorption (MA) performance is attributed to the rational three-dimensional structural design, the modulation of magnetic/carbon components, the optimized impedance matching, and the coordinated action of multiple mechanisms. It was further demonstrated by high-frequency structural simulation that the composite can effectively dissipate microwave energy in practical applications. Therefore, the results indicate a favorable potential of the synthesis and application of semiconductor/magnetic component/biomass-derived carbon microwave absorbing materials.

Encapsulated prussian blue analogs derived nanocubes with tunable yolk-shell structure enabling highly efficient microwave absorption

Pyrolytic Prussian blue analogs (PBAs) have attracted much attention in the field of microwave absorption (MA) because of their outstanding magnetic-carbon synergism effect. However, pure PBAs are prone to collapse and aggregate during pyrolysis, resulting in impedance mismatch that weaken the MA performance. Herein, the amorphous carbon layer with adjustable dielectric constant as the encapsulated layer, together with pyrolytic PBAs enables remarkable optimized performance via forming the classic yolk-shell structure. Specifically, the amorphous carbon obtained by quantitatively carbonizing phenolic resin, can not only avoid the collapse of pyrolytic PBAs but also optimize electromagnetic parameters to achieve optimum impedance matching by varying thickness. The NiFe alloys/graphite carbon core derived from pyrolytic NiFe–PBAs also enhance synergistic attenuation in the YS-NiFe/GC@C absorbers. According to experimental results, all YS-NiFe/GC@C absorbers exhibit impressive MA properties. When the thickness of the amorphous carbon shell is 50 nm, the minimum reflection loss value is as low as −56.3 dB and the maximum effective absorption bandwidth reaches 5.64 GHz, indicating that optimizing impedance matching via hierarchical and quantitative design can maximize the MA capability. The result is then verified by simulation calculations. Therefore, this promising work provides guidance for the sophisticated construction of tunable PBA-based MA materials.

Novel preparation of FeCo alloy/graphene foam composites for efficient microwave absorption

Five groups of FeCo alloy/graphene foam (FeCo/GF) composites with different GF contents (1%, 2%, 3%, 4%, and 5% of the mass of the FeCo alloy) were prepared in this work. The results show that the morphology, saturation magnetization, and electromagnetic parameters of the composites were greatly affected by the GF amount. The reticular porous structure of GF significantly increases the multiple scattering events and loss paths of electromagnetic waves and provides an excellent electric loss. Being a typical soft magnetic material, FeCo exhibits a high saturation magnetization and an excellent magnetic loss. The FeCo/GF composite has excellent microwave absorption properties, which are attributed to its superior dielectric loss, conductive loss, natural resonance, and exchange resonance loss mechanisms. In particular, when the content of GF is 3% of the mass of FeCo alloy, it exhibits the best effective absorption bandwidth. With a matching thickness of only 1.85 mm, this composite achieves a maximum effective absorption bandwidth of 7.2 GHz (10.8–18 GHz). Additionally, when the content of GF is 4% of the mass of FeCo alloy, the sample exhibits the lowest reflection loss, which reaches −61.68 dB at a frequency of 3.44 GHz.

Synthesis of nitrogen-doped reduced graphene oxide/magnesium ferrite/polyaniline composite aerogel as a lightweight, broadband and efficient microwave absorber

The fabrication of graphene-based microwave absorbing materials with low density, small filling ratio, broad bandwidth and strong absorption remains a huge challenge. In this work, nitrogen-doped reduced graphene oxide/magnesium ferrite/polyaniline (NRGO/MgFe2O4/PANI) composite aerogel was synthesized by a three-step method of solvothermal reaction, in situ chemical oxidation polymerization and hydrothermal self-assembly. The results showed that the obtained aerogels had a unique three-dimensional (3D) porous network structure and low bulk density (11.1–13.0 mg cm−3). It was worth noting that in the NRGO/MgFe2O4/PANI ternary composite aerogel, MgFe2O4 coated with a thin PANI layer was anchored on the surface of NRGO sheets. Furthermore, the NRGO/MgFe2O4/PANI ternary composite aerogel showed much better microwave absorbing capacity compared with pure NRGO aerogel and NRGO/MgFe2O4 binary composite aerogel. When the filling ratio was as low as 11.5 wt.%, the obtained ternary composite aerogel exhibited the maximum effective absorption bandwidth of 7.0 GHz at a matching thickness of 2.1 mm, and the minimum reflection loss of -42.9 dB at a thickness of 3.57 mm. Additionally, the probable microwave dissipation mechanism was also elucidated. It was believed that this study would pave the way for the construction of 3D graphene-based composites as lightweight, broadband and efficient microwave absorbents.

Pomegranate-like ATO/SiO2 microspheres for efficient microwave absorption in wide temperature spectrum

High-performance microwave-absorbing materials (MAMs) should meet both impedance matching and attenuation performance. Commonly, it is hard to maintain excellent microwave absorption (MA) performance at an elevated temperature because the reliance on impedance matching and dielectric loss about temperature mutually restricts. In this work, the pomegranate-like antimony-doped tin dioxide (ATO)/ silica dioxide (SiO2) spheres were fabricated via a simple spray drying process. When the spheres were used as functional units and dispersed in the matrix, the corresponding composites exhibit an outstanding anti-reflection effect on microwaves. Moreover, the unique pomegranate-like structure of the ATO/SiO2 spheres provides both the effective local eddy current and abundant heterogeneous interface, which therefore contribute harvest enhanced dielectric relaxation and improved absorption performance when compared with that of the corresponding ATO/SiO2 composition. As a result, the maximum reflection loss of the ATO/SiO2 spheres composites can reach –47.8 dB at 9.7 GHz with a thickness of 1.8 mm, while the reflection loss could reach –47.3 dB at 573 K and the effective absorption bandwidth is 2.4 GHz. This work reveals the importance of local eddy current loss in optimizing the electromagnetic wave (EMW) absorption performance and impedance matching, providing novel guidance on designing advanced high-temperature MAMs.