High-performance Microwave Absorption Materials Research Articles

Fixed-Point Atomic Regulation Engineered Low-Thickness Wideband Microwave Absorption.

Atomic doping is widely employed to fine-tune crystal structures, energy band structures, and the corresponding electrical properties. However, due to the difficulty in precisely regulating doping sites and concentrations, establishing a relationship between electricity properties and doping becomes a huge challenge. In this work, a modulation strategy on A-site cation dopant into spinel-phase metal sulfide Co9S8 lattice via Fe and Ni elements is developed to improve the microwave absorption (MA) properties. At the atomic scale, accurately controlling doped sites can introduce local lattice distortions and strain concentration. Tunned electron energy redistribution of the doped Co9S8 strengthens electron interactions, ultimately enhancing the high-frequency dielectric polarization (ɛ' from 10.5 to 12.5 at 12GHz). For the Fe-doped Co9S8, the effective absorption bandwidth (EAB) at 1.7mm increases by 5%, and the minimum reflection loss (RLmin) improves by 26% (EAB = 5.8GHz, RLmin = -46dB). The methodology of atomic-scale fixed-point doping presents a promising avenue for customizing the dielectric properties of nanomaterials, imparting invaluable insights for the design of cutting-edge high-performance microwave absorption materials.

Efficient Synthesis of Fe3O4/PPy Double-Carbonized Core-Shell-like Composites for Broadband Electromagnetic Wave Absorption.

Ever-increasing electromagnetic pollution largely affects human health, sensitive electronic equipment, and even military security, but current strategies used for developing functional attenuation materials cannot be achieved in a facile and cost-effective way. Here, a unique core-shell-like composite was successfully synthesized by a simple chemical approach and a rapid microwave-assisted carbonization process. The obtained composites show exceptional electromagnetic wave absorption (EMWA) properties, including a wide effective absorption band (EAB) of 4.64 GHz and a minimum reflection loss (RLmin) of -26 dB at 1.6 mm. The excellent performance can be attributed to the synergistic effects of conductive loss, dielectric loss, magnetic loss, and multiple reflection loss within the graphene-based core-shell-like composite. This work demonstrates a convenient, rapid, eco-friendly, and cost-effective method for synthesizing high-performance microwave absorption materials (MAMs).

Multi-dimensional nano-microstructures design of MOF-derived CoSe2@N–C composites toward excellent microwave absorption

Nano-microstructures design enabled the controlled tuning of electromagnetic parameters to obtain high-performance microwave absorption materials (MAM). Herein, Metal-Organic Frameworks-derived (MOFs-derived) CoSe2@Nitrogen-doped Carbon (CoSe2@N–C) materials with controllable nano-microstructures also exhibit tunable morphologies from dodecahedra-, cube-, fusiform-to sheet-like by adjusting the solvent and the molar ratio of cobalt/ligand. The organic frameworks are maintained by pyrolysis selenization, forming a unique CoSe2@N–C three-dimensional conduction network that broadens electron transport and electromagnetic wave multiple reflection routes, enhances conduction loss capability, and optimizes impedance matching. The confinement of ligand-derived carbon can avoid the agglomeration of CoSe2, forming rich heterogeneous interfaces within CoSe2@N–C, enhancing interfacial polarization loss. Symmetric models are developed to reveal the importance of destructive interference on the microwave absorption property. In addition, dipole polarization of defects and doped-nitrogen further encourages the enhancement of the microwave absorption properties of CoSe2@N–C. The CoSe2@N–C-d exhibits the best microwave absorption properties with a minimum reflection loss (RLmin) of −42.31 dB at 15.62 GHz in a thickness of 1.5 mm, and an effective absorption bandwidth of 4.25 GHz. The excellent absorption performance of CoSe2@N–C paves the way for the design and synthesis of high-performance absorbers.

MXene Hollow Spheres Supported by a C-Co Exoskeleton Grow MWCNTs for Efficient Microwave Absorption.

High-performance microwave absorption (MA) materials must be studied immediately since electromagnetic pollution has become a problem that cannot be disregarded. A straightforward composite material, comprising hollow MXene spheres loaded with C-Co frameworks, was prepared to develop multiwalled carbon nanotubes (MWCNTs). A high impedance and suitable morphology were guaranteed by the C-Co exoskeleton, the attenuation ability was provided by the MWCNTs endoskeleton, and the material performance was greatly enhanced by the layered core-shell structure. When the thickness was only 2.04mm, the effective absorption bandwidth was 5.67GHz, and the minimum reflection loss (RLmin) was - 70.70dB. At a thickness of 1.861mm, the sample calcined at 700°C had a RLmin of - 63.25dB. All samples performed well with a reduced filler ratio of 15wt%. This paper provides a method for making lightweight core-shell composite MA materials with magnetoelectric synergy.

Preparation of Metal–Organic-Framework-Derived Fe-CN@CoCN Nanocomposites and Their Microwave Absorption Performance

Microwave technology is commonly used in many fields such as wireless communication and medical treatment, which are closely related to social development. However, electromagnetic pollution caused by microwaves is gradually increasing and the demand for high-performance microwave absorption materials is also increasing. Porous materials obtained by the pyrolysis of metal–organic frameworks (MOFs) at high temperatures exhibit good conductivity and magnetism, and the original skeleton structure of MOFs can be maintained; thus, MOF-derived materials can be considered viable candidates of microwave absorption materials. In this paper, Fe-CN@CoCN materials were prepared by pyrolyzing a ferrocene (Fc)-doped core–shell zeolite imidazole framework (Fc-ZIF-8@ZIF-67) at 700, 800, and 900 °C for 2 h in an Ar atmosphere. The obtained Fe-CN@CoCN-0.25-700 nanocomposite exhibited excellent microwave absorption (MA) performance with a minimum reflection loss (RLmin) of −42.27 dB at 5.68 GHz and an effective absorption bandwidth (EAB, RL < −10 dB) of 4.80 GHz at a thickness of 2.5 mm. The Fe-CN@CoCN-0.25-800 nanocomposite possessed optimized MA properties with an RLmin of −40.78 dB at 12.56 GHz and an EAB of 4.16 GHz at relatively low thickness of 2 mm. Fe-CN@CoCN nanocomposites are expected to be efficient materials for microwave absorption coatings.

Constructing gradient reflection and scattering porous framework in composite aerogels for enhanced microwave absorption

Developing high-performance microwave absorption (MA) materials becomes an urgent concern in the field of electromagnetic protection. Constructing porous framework is an efficient approach to MA owing to the abilities of adjusting impedance matching and providing more reflection and scattering paths for electromagnetic waves. Herein, a cellulose nanofibril (CNF)/honeycomb-like carbon-shell encapsulated FeCoNi@C/carbon nanotube (CNT) composite aerogel was fabricated via a facile freeze-drying method. The super-lightweight composites showed a distinctive gradient structure for reflection and scattering inside aerogel pores, micrometer small pores, and nano-fillers on the pore walls. The composite aerogel showed an ideal minimum reflection loss (RLmin) of −43.6 dB and remarkable adjustable effective absorption bandwidth (EAB) of 12.18 GHz due to good impedance matching, unique gradient porous structure, and synergies of multiple loss mechanisms. Therefore, this work will provide a viable strategy to improve the MA capability of absorbers by taking full advantage of constructing gradient reflection and scattering porous structure.

Designing high-performance microwave absorption materials through co-doping strategy: Experimental and theoretical insights

The essence of designing ideal absorption materials is to control the electromagnetic parameters. In this work, doping strategy was adopted to regulate electromagnetic parameters. According to the experimental results and density functional theory calculations, the introduction of Co can make the charge redistribute, distortion increase, bonds length decrease, and bonds energy enhance, which can lead to the reducing of dielectric storage and raising of dielectric loss. Meanwhile, the superfine long nanowires of Co-doped MnO2 can bring abundant surface and interfaces, which improve the polarization relaxations. These changes result in the enhancement of attenuation and improvement of impedance matching feature at the same time. Therefore, the Co-doped MnO2 exhibits excellent microwave absorption performance, the minimal reflection loss is -51.03 dB and effective absorbing bandwidth can reach 7.04 GHz. This work offers an effective approach for the design of high-performance microwave absorption materials, which has been validated through experimental and theoretical evidence.

Controllable fabrication of CoNi bimetallic alloy for high-performance electromagnetic wave absorption.

With the coming era of artificial intelligence (AI) dominated by high-tech electronics, developing high-performance microwave absorption materials (MAMs) is imperative to solve the problem of increasing electromagnetic inference and pollution. Herein, a metal-organic framework (MOF)-derived CoNi bimetallic alloy (CoNi/C) with an irregular rod-like structure is prepared by a thermal reduction method. Introducing the CoNi alloy facilitates the balance between conduction loss and polarization loss and forms good impedance matching, leading to excellent microwave absorption performance. Interestingly, the optimization of absorption performance can be further achieved by controllably modulating the molar ratio of Co and Ni (Co2+/Ni2+). As expected, the obtained CoNi/C delivers excellent microwave absorption performance with a minimum reflection loss (RLmin) of -50.80 dB at 10.40 GHz and an effective absorption bandwidth (EAB) of 3.28 GHz (8.91-12.19 GHz) with a filler loading of 50 wt% at 2.0 mm. In addition, the CoNi/C can reach a maximum EAB of 4.77 GHz (12.99-17.76 GHz) at a low thickness of 1.5 mm, spanning nearly the entire Ku band. The CoNi3/C also exhibits an impressive RLmin of -44.84 dB at 3.28 GHz in the S band. This work offers a novel strategy to modulate the magnetic/electric properties of MOF-derived MAMs.

Kapok derived microtubular FeCo/CMT with high specific surface area for broadband microwave absorption

Since biomass-derived carbon materials possess the advantages of peculiar morphology and low density. They have received significant attention on microwave absorption materials. We synthesize a one-dimensional hollow FeCo/carbon microtubule (FeCo/CMT) derived from homogeneous kapok fiber using a feasible solvothermal method and calcination process. The graphitization degree and magnetic properties of FeCo/CMT could be controlled by manipulating the calcination temperature. The FeCo/CMT composite with the calcination temperature of 600 °C demonstrated exceptional microwave absorption performance, characterized by strong absorption (−50.6 dB), broadband absorption (12.4–18.0 GHz), thin thickness (2.5 mm), and low loading (10 wt%). The hollow structure, interfacial polarization, and the synergistic effect between FeCo and CMT collectively account for the microwave absorption mechanisms. Considering its outstanding comprehensive characteristics and performance, the biomass-derived hollow FeCo/CMT shows great potential for widespread application as a high-performance microwave absorption material.

Electrostatically self-assembled Fe3O4@SiO2/MXene 3D interlayered structure improves Ku-band microwave absorption efficiency of epoxy-based nanocomposites

It is challenging to develop lightweight and efficient frequency-selective microwave absorption materials due to the trade-off between impedance matching and microwave attenuation ability. This study proposes a multiple heterointerfaces engineering strategy via electrostatically assembling to construct Fe3O4@SiO2/MXene 3D interlayer structure, which fully exerted the synergistic effect of dielectric-magnetic components. The 3D interlayer heterostructure achieves good impedance matching due to electromagnetic coupling and extended microwave propagation path. Simultaneously, massive charge transfer and redistribution at multiple heterointerfaces embedded in this structure boost the polarization relaxation and dielectric loss ability. Consequently, the prepared nanocomposites exhibit remarkable Ku-band microwave absorption efficiency (−60.9 dB at a thickness of 1.0 mm), and have demonstrated valid practicality via Tesla wireless transmission shielding experiments. This study opens exciting possibilities for progress in the structural design, facile preparation and practical application of high-performance Ku-band microwave absorption materials.

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.

High-Performance Microwave Absorption Materials: Theory, Fabrication, and Functionalization

High-Performance Microwave Absorption Materials: Theory, Fabrication, and Functionalization

Ultrafine Vacancy-Rich Nb2O5 Semiconductors Confined in Carbon Nanosheets Boost Dielectric Polarization for High-Attenuation Microwave Absorption

The integration of nano-semiconductors into electromagnetic wave absorption materials is a highly desirable strategy for intensifying dielectric polarization loss; achieving high-attenuation microwave absorption and realizing in-depth comprehension of dielectric loss mechanisms remain challenges. Herein, ultrafine oxygen vacancy-rich Nb2O5 semiconductors are confined in carbon nanosheets (ov-Nb2O5/CNS) to boost dielectric polarization and achieve high attenuation. The polarization relaxation, electromagnetic response, and impedance matching of the ov-Nb2O5/CNS are significantly facilitated by the Nb2O5 semiconductors with rich oxygen vacancies, which consequently realizes an extremely high attenuation performance of − 80.8 dB (> 99.999999% wave absorption) at 2.76 mm. As a dielectric polarization center, abundant Nb2O5–carbon heterointerfaces can intensify interfacial polarization loss to strengthen dielectric polarization, and the presence of oxygen vacancies endows Nb2O5 semiconductors with abundant charge separation sites to reinforce electric dipole polarization. Moreover, the three-dimensional reconstruction of the absorber using microcomputer tomography technology provides insight into the intensification of the unique lamellar morphology regarding multiple reflection and scattering dissipation characteristics. Additionally, ov-Nb2O5/CNS demonstrates excellent application potential by curing into a microwave-absorbing, machinable, and heat-dissipating plate. This work provides insight into the dielectric polarization loss mechanisms of nano-semiconductor/carbon composites and inspires the design of high-performance microwave absorption materials.

Multidimensional nanomaterials synergistic polyimide nanofiber/MXene/NiFe2O4 hybrid aerogel for high-performance microwave absorption

Microwave absorption materials are urgently demanded to control the increasing electromagnetic radiation pollution, but it remains a great challenge to achieve high-performance absorption through ingenious structure design and reasonable multicomponent strategy. Herein, a three-dimensional (3D) hybrid aerogel constructed from multidimensional nanomaterials was fabricated via freeze-drying method followed by heating treatment process. Therein, 2D Ti3C2Tx MXene nanosheets and 0D NiFe2O4 nanoparticles act as the electrical-magnetic skeleton of aerogel, while 1D polyimide nanofibers and polydimethylsiloxane as internal supporting parts and external crosslinker, respectively. The macroscopic interconnected porous structure coupled with the microscopic multiphase heterointerfaces are beneficial to forming the perfect impedance matching and superior dielectric/magnetic synergistic loss effects. Thus, the microwave absorption performance of this hybrid aerogel achieves thin thickness (1.5 mm), light weight (∼9.6 mg/cm3), wide effective absorption bandwidth (−6.24 GHz), and strong absorption (minimum reflection loss of −64.87 dB, 99.99996% microwave absorption) features. Besides, this aerogel also exhibits exceptional structural robustness and mechanical properties, as well as good hydrophobicity and thermal insulation characteristics, which ensure its stable and durable microwave absorption application in complex environments. This study effectively integrates multidimensional nanomaterials into a host–guest aerogel system, providing a valuable strategy for constructing high-performance microwave absorption materials.

Gradient Hierarchical Hollow Heterostructures of Ti3C2Tx@rGO@MoS2 for Efficient Microwave Absorption.

Heterostructure engineering has emerged as a promising approach for creating high-performance microwave absorption materials in various applications such as advanced communications, portable devices, and military fields. However, achieving strong electromagnetic wave attenuation, good impedance matching, and low density in a single heterostructure remains a significant challenge. Herein, a unique structural design strategy that employs a hollow structure coupled with gradient hierarchical heterostructures to achieve high-performance microwave absorption is proposed. MoS2 nanosheets are uniformly grown onto the double-layered Ti3C2Tx MXene@rGO hollow microspheres through self-assembly and sacrificial template techniques. Notably, the gradient hierarchical heterostructures, comprising a MoS2 impedance matching layer, a reduced graphene oxide (rGO) lossy layer, and a Ti3C2Tx MXene reflective layer, have demonstrated significant improvements in impedance matching and attenuation capabilities. Additionally, the incorporation of a hollow structure can further improve microwave absorption while reducing the overall composite density. The distinctive gradient hollow heterostructures enable Ti3C2Tx@rGO@MoS2 hollow microspheres with exceptional microwave absorption properties. The reflection loss value reaches as strong as -54.2 dB at a thin thickness of 1.8 mm, and the effective absorption bandwidth covers the whole Ku-band, up to 6.04 GHz. This work provides an exquisite perspective on heterostructure engineering design for developing next-generation microwave absorbers.

Enhancing broadband and intense microwave absorption properties of flaky FeSiCr powder by coating SiO2

Flaky FeSiCr@SiO2 composites with broadband and intense absorption were successfully synthesized by modified Stöber method. The phase, microstructure and morphology of flaky FeSiCr@SiO2 composites were investigated by XRD, FT-IR, SEM and TEM, confirming the successful preparation of SiO2 coating. The thermal behavior of flaky FeSiCr@SiO2 composites was analyzed by TGA/DSC. The results showed that the oxidation resistance of the coated FeSiCr powder was promoted. The electromagnetic wave absorption properties of samples with different contents of tetraethyl orthosilicate (TEOS) were systematically investigated. The sample synthetized with 10 ml TEOS possesses the optimal absorption performance, which is attributed to the synergistic effect of magnetic loss and dielectric loss. The minimum reflection loss is −65.3 dB at 4.4 GHz. And the maximum effective absorption bandwidth is 6.0 GHz with only a 1.5 mm thickness. In particular, by controlling the thickness of the absorber, the effective absorption bandwidth can reach 13.3 GHz (2.9–16.2 GHz), covering the entire C and X bands. Thus, the flaky FeSiCr@SiO2 composites can be used as high-performance microwave absorption materials.

Hierarchical and Porous Structures of Carbon Nanotubes-Anchored MOF Derivatives Bridged by Carbon Nanocoils as Lightweight and Broadband Microwave Absorbers.

High-performance microwave absorption (MA) materials have attracted more and more attention because they can effectively prevent microwave radiation and interference from electronic devices. Herein, a new type of MA composite is constructed by introducing carbon nanotubes (CNTs)-anchored metal-organic framework derivatives (MOFDs) into a conductive carbonnanocoil (CNC) network, denoted as CNC/CNT-MOFD. The CNC/MOFD shows a wide effective absorption band of 6.7GHz under a filling ratio of only 9% in wax-matrix. This is attributed to the hierarchical and porous structures of MOFD bridged by the uniformly dispersed conductive CNC network and the cross-polarization induced by the 3D spiral CNCs. Besides, the as-grown 1D CNTs improve space utilization, porosity, and polarization loss of the composites, resulting in the increase of imaginary permittivity, which further realizes impedance matching and energy attenuation. The Ni nanoparticles in layers of MOFD and at the tips of CNTs generate magnetic loss, promoting the low-frequency absorption ability. Resultantly, RCS values of the optimized composite in all tested theta (θ) ranges are less than -25dB m2 at 9.5GHz, effectively reducing the probability of the target detected by the radar.

Facile synthesis of 2D MoS2/reduced graphene oxide hybrids with excellent microwave absorption

High-performance microwave absorption materials with tunable electromagnetic properties have long been the goal of researchers. It is still a challenge to achieve broad band absorption and lightweight performance by simply optimizing the chemical composition of absorbers. Molybdenum disulfide (MoS2) belongs to the two-dimensional transition metal disulfide with a layered structure similar to graphene. In this work, two-dimensional MoS2/reduced graphene oxide (MS/RGO) hybrids have been constructed through a convenient self-assembled hydrothermal method, in which MoS2 ultrathin nanosheets in-situ grow uniformly on the surface of RGO, constructing a unique hierarchical microstructure. Electromagnetic parameter measurements display that the dielectric behaviors of MS/RGO composites are optimized via changing the content of RGO, and meanwhile the superior microwave absorption properties are achieved with the filler-loading ratio of only 20 wt%. The widest effective absorption bandwidths (RL<−10 dB) of 5.68 GHz (12.32–18 GHz) and 6.32 GHz (11.20–17.52 GHz) are observed at a thickness of 2.0 mm for MS/RGO-10 and MS/RGO-15, respectively. When the thickness is raised to 5.0 mm, the reflection loss value of MS/RGO-10 composites reaches the minimum value of − 39.8 dB at 4.96 GHz. The improved performance can be explained by the strong interfacial polarization loss due to abundant heterogeneous interfaces, defect dipole polarization, conduction loss, and multiple reflections and scattering. The results indicate that the light-weight MS/RGO composite is considered as a promising candidate for high-performance microwave absorbers with an adequate absorption bandwidth.

Morphology engineering of defective graphene for microwave absorption

Graphene with abundant defects has been considered as the most lightweight electromagnetic functional materials. Although important, the dominant electromagnetic response of defective graphene with diverse morphologies is rarely the focus of existing research. Herein, the defective graphene with two-dimensional planar structure (2D-ps) and three-dimensional continuous network (3D-cn) morphologies were dexterously designed with 2D mixing and 3D filled systems of polymeric matrix. A comparison between the topologies of defective graphene-based nanofillers and the microwave attenuation behaviors was examined. Defective graphene with 3D-cn morphology can achieve ultralow filling content and broadband absorption, which is attributed to the presence of numerous pore structures that promote impedance matching, induce continuous conduction loss and provide multiple reflection and scattering sites for electromagnetic wave attenuation. Comparatively, by virtue of the increased filling content of 2D-ps, the dielectric losses primarily originate from the dielectric genes, including aggregation-induced-charge transport, abundant defect and dipole polarization, resulting in good microwave absorption at low thickness and low frequency. Therefore, this work provides a pioneering insight into morphology engineering of defective graphene microwave absorbers, and it will guide future exploration of customizing high-performance microwave absorption materials based on graphene-based low-dimensional building blocks.

Rational design of hollow microspheres@Ba0.5Sr0.5Fe12O19/PANI for lightweight high-performance microwave absorption materials

Rational design of hollow microspheres@Ba0.5Sr0.5Fe12O19/PANI for lightweight high-performance microwave absorption materials