Lightweight Microwave Absorption Materials Research Articles

Lightweight titanium dioxide/carbon nanotube composites prepared by atomic layer deposition for broad-band microwave absorption

The microwave absorbing material with appropriate impedance matching and excellent attenuation ability can be applied to resist electromagnetic radiation. In this work, carbon nanotubes were modified by titanium dioxide via the atomic layer deposition method, to prepare lightweight composites with high microwave absorption performance. The impedance matching and attenuation ability of titanium dioxide/carbon nanotube (TiO2/CNT) composites could be precisely controlled by adjusting the number of titanium dioxide deposition cycles. The relationship between the microstructure and microwave absorption performance of the composite was analyzed in detail. When the number of TiO2 deposition cycles was 100, the composite displayed outstanding microwave absorption performance, due to appropriate impedance matching and strong attenuation ability. The maximum effective absorption bandwidth of the composite reached 5.19 GHz (1.6 mm), which almost covered the Ku band. The microwave attenuation mechanism of the composite has also been investigated. This work provided a new idea for fabricating lightweight microwave absorption materials.

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.

Construction of Ni/C composites with double-shell hollow porous structure toward high-efficiency microwave absorption

Designing structure at the nanoscale of materials has been proved to be an effective way to control electromagnetic parameters and optimize microwave absorption performance. For constructing lightweight microwave absorption materials, abundant studies focus on the preparation of absorbent with hollow, porous or yolk-shell structure. However, it is still a challenge to integrate multiple structures on one material by simple method. In this work, we found that the addition of citric acid in the preparation process played an extremely important role in regulating the structure of Ni-MOF, and developed one-step approach to synthesis double-shell hollow porous Ni-MOF. After the carbonization process, the Ni/C composite was obtained. The controllable morphology of Ni-MOF endowed Ni/C composite adjustable absorbing properties. Under the assistance of citric acid, the Ni/C composite with yolk-shell, porous, as well as double-shell hollow porous structure was also synthesized. The optimal reflection loss was −56.18 dB, the broadest bandwidth was 6.1 GHz at 2.2 mm for double-shell hollow porous Ni/C composite. Particularly, strong reflection loss at C band, X band, and Ku band was realized by regulating the structure of Ni/C composite. This work revealed the mechanism of microstructures regulating the absorbing properties, which could be beneficial to the further development of MOFs derived absorbent.

Fe/Co decorated C@CNTs derived from bimetallic metal-organic-framework for microwave absorption with wide bandwidth

It’s a hurry to introduce a lightweight and high-efficiency microwave absorption material that is easy to synthesize, since the electromagnetic interference pollution is getting increasingly serious. Carbon-based microwave absorption material based on bimetallic metal-organic frameworks (MOFs) gets high conductivity and good magnetism at the same time, and thus can be regarded as an efficient microwave absorber with lightweight. Herein, we introduce an easy method to compose bimetallic carbon-based microwave absorbers based on ZIF-67. By changing the proportion of Fe3+ and Co2+, not only the magnetism of the material can be adjusted, the amount of carbon nanotubes (CNTs) and so as the dielectric property of the material can also be regulated. The method of introducing precursors at room temperature and then calcinating at an Ar atmosphere is simple to repeat and appropriate for mass production. When the dosage molar ratio of Co2+: Fe3+ is 3: 2, the minimum reflection loss (RLmin) can reach − 24.83 dB while the effective absorption bandwidth (EAB) can reach 5.14 GHz when the thickness is 1.7 mm, under a 30 wt% filling loading. We believe that this work can provide a reliable method to introduce carbon-based microwave absorption material based on bimetallic MOF materials.

Lightweight magnetic metal nanochain aerogels for realizing broadband and strong absorption of electromagnetic wave

Developing lightweight and efficient magnetic metal microwave absorption materials is crucial to broaden the application of metal-based materials in the field of electromagnetic wave (EMW) absorption. In this work, monometallic aerogels with three-dimensional (3D) network structure were successfully synthesized under the synergistic effect of the reduction of NaBH4 and the subsequent release of H2, and the microstructure and electromagnetic parameters were regulated by changing the molar ratio of metal salts to reductant NaBH4. Notably, Co aerogel (C-AG-0, Co2+∶NaBH4 =1:3) has a density of 0.16 g/cm3 and exhibits optimum EMW absorption properties. It has an effective absorption bandwidth (EAB) of 6.24 GHz (10.88–17.12 GHz) at a thickness of 1.7 mm, even beyond reported metal-based composites. The excellent absorption performance is owed to the highly porous 3D mesh stucture, which provides good impedance matching and conduction loss, as well as the interfacial polarization caused by a large specific surface area (SSA). This work provides an alternative choice for the facile preparation of lightweight magnetic metal EMW absorbents with highly efficient absorption.

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

Structural design, preparation and characterization of an effective microwave absorbent: rGO-NiCo2O4 nanochains

Reduced graphene oxide-nickel cobaltate nanochain (RGO-NiCo2O4 nanochains) is prepared via two-step pyrolysis process. Carbon nanotubes were grown on the surface of GO by a one-step pyrolysis process, and then NiCo2O4 nanochains were prepared by adsorption of metal ions onto carbon nanotubes grown in situ on graphene sheets, followed by a step pyrolysis process. The sizes of NiCo2O4 are in the range of 5–10 nm; and lengths of the nanochains are approximately 200 nm. When the doping ratio in paraffin is 10 wt%, the microwave-absorbing performance is as follows: the minimum reflection loss (RL) value is − 42.10 dB which is founded at the frequency of 16.64 GHz while the thickness is 1.6 mm. Effective absorption bandwidth (RL < −10 dB) reaches 4.88 GHz when the thickness is 1.8 mm. The excellent absorption properties result from the unique microstructure and synergism of RGO and NiCo2O4. Therefore, it is expected to be a kind of light-weight microwave absorption materials.

Nanowires/nanohelices hybrid carbon aerogels as the lightweight and hydrophobic microwave absorbers with excellent electrothermal properties

To extend the operational life of electronic equipment under a complex environment and introduce protection for human health against electromagnetic pollution, it is urgent to construct lightweight microwave absorption materials (MAMs) with hydrophobicity and electrothermal properties. Herein, we have fabricated creatively the nanowires/nanohelices hybrid carbon (CNWs/CNHs) aerogels via growing and carbonizing nanohelices in bacterial cellulose (BC) matrix, forming intertwined and interconnected conductive network. In addition, we investigated systematically the detailed structure and microwave absorption mechanism of the new type of CNWs/CNHs aerogels. Such novel structure was found to promote multiple relaxation and interface polarization due to the electromagnetic cross polarization, which in turn ameliorates remarkably the microwave absorption intensity and broadens the effective absorption bandwidth (EAB). The optimal CNWs/CNHs aerogels can show an excellent microwave absorption intensity of −56.90 dB at 13.76 GHz at a filling content of 5 wt%, and extend its maximum EAB to 6.32 GHz at a thickness of just 2.00 mm. At the same time, the CNWs/CNHs aerogels also have a superior self-cleaning function and a good electrothermal conversion performance. Therefore, the CNWs/CNHs aerogels may be adopted as the lightweight and hydrophobic MAMs with excellent electrothermal properties to satisfy the practical applications in complex low-temperature environment.

Microwave Absorption Performance of Carbon Black/Polylactic Acid Composite for Fused Filament Fabrication

To prepare lightweight, wideband, strong absorption and low-cost microwave absorbing materials, carbon black/polylactic acid (CB/PLA) composite filaments were prepared using a high-energy mixer and twin-screw extruder. Coaxial ring test pieces were printed by fused filament fabrication (FFF) technology with polylactic acid as the matrix and carbon black as the absorbent. The crystal texture and micromorphology of the composites were observed by XRD and SEM. The electromagnetic parameters were measured at 2–18 GHz using a vector network analyzer. The influence of CB content on the absorbing performance of the composites was studied, and the loss mechanism was explained. The results show that when the CB content (refers to PLA) is 25%, the composite has suitable impedance matching, conduction loss, and polarization loss, resulting in the best microwave absorption performance. The minimum reflection loss reached −45.47 dB at 13.68 GHz, and the corresponding effective absorption bandwidth was 5.36 GHz (10.72–16.08 GHz) with a matching thickness of 2.1 mm. At the same time, the density of the composite was only 1.19 g/cm3. This work sheds light on the development of lightweight and high-efficiency microwave absorption materials (MAMs) in a simple and low-cost manner.

Fe@Fe3C Core-Shell Nanoparticles Embedded in Polyvinyl Alcohol-Derived Porous Carbon toward Light and High-Performance Microwave Absorption

High-performance microwave absorbents play a key role in information technology field. In this work, excellent microwave absorption property was achieved via embedded Fe@Fe3C core–shell nanoparticles in polyvinyl alcohol-derived porous carbon matrix. The results indicate that the microwave absorption performance will be greatly enhanced due to the interface between the nanoparticles and matrix, as well as the core–shell and porous structure, increase the energy consumption capacity via dipole polarization, interface loss and the multiple reflection/scattering. The maximum reflection loss (RLmax) reaches −56.88 dB at 11.3 GHz with the thickness of 2.11 mm, and the effective absorption bandwidth (EAB, RL<−10 dB) can get up to 5.2 GHz (from 12.9 to 18 GHz) with the thickness of 1.64 mm. Moreover, due to the low density of the porous carbon matrix, the total weight of the absorbents can be greatly induced, which provides an efficient way for lightweight and high-performance microwave absorption materials design.

Environmentally friendly a multifunctional cellulose-based carbon foam for superior electromagnetic wave absorption performance

Ingenious microstructure and suitable multicomponent are still challenging for designing lightweight, low-cost, and resource-renewable microwave absorption materials. Herein, environmentally friendly cellulose-based three-dimensional (3D) porous carbon foams were successfully prepared by freeze-drying and carbonization process. The pyrolysis process under gradient temperature could give rise to tunable electromagnetic (EM) parameters. The minimum reflection loss of carbon nanotubes/cellulose foam under 700°C is −55.4 dB (2.11 mm) at 9.27 GHz benefiting from the construction of double nano-interfaces so-called unique “1D-1D” combination, which can improve interface polarization and impedance matching. Furthermore, such carbon foam exhibits good thermal insulation and hydrophobicity, guaranteeing the stable and durable EM wave absorption application in the field of resist deformation, water or humid environments, and high-temperature attacks.

Simultaneously enhancing mechanical and microwave absorption properties of Cf/SiC composites via SiC nanowires additions

Cf/SiC composite is an excellent structural and functional material, silicon carbide nanowires (SiCnws) are not only a toughening material but also a great application in the field of microwave absorption. In this study, SiCnws are grown on the surface of carbon fiber (Cf) by polymer impregnation and pyrolysis, and the SiC matrix was prepared by chemical vapor osmosis method. The SiCnws are introduced to enhance the mechanical and microwave absorption properties simultaneously. After 3 impregnations, the flexural strength of the composite was 107.35 ± 10 MPa. When the thickness is 1.86 mm, the minimum reflection loss value is −41.08 dB, and the effective absorption bandwidth (RL ≤ −10 dB) is 3.86 GHz. Furthermore, the microwave absorption mechanism of the material is discussed. This work provides a new method to prepare lightweight, stable and high-performance microwave absorption materials, and these materials are expected to be used in high temperature environments.

MXene@C heterogeneous nanocomposites with the 2D-0D structure for ultra-light and broadband electromagnetic wave absorption

0D-2D Polydopamine (PDA)-derived carbon nanoparticles @ MXene composites (PCM) with high microwave absorption properties were prepared by in-situ self-polymerization combined with vacuum pyrolysis. As the “nano clothing” of MXene, the moderate accumulation of PDA-derived carbon nanoparticles makes enough interface contact with MXene nanosheets, which not only improves the impedance matching of MXene reasonably but also optimizes the dielectric loss. Based on the multi-dimension structure and multi-component synergistic effect, when the filling amount of the composite is only 7.5 wt% and the thickness is 2.8 mm, the best reflection loss at 10 GHz is −46.92 dB and the maximum effective absorption bandwidth is 7.01 GHz. This work provides a synthesis strategy of crystal/amorphous heterointerface and offers a new way for the preparation of lightweight, broadband, and efficient microwave absorption materials, showing great application potential.

Dielectric enhancement effect in biomorphic porous carbon-based iron@iron carbide ‘meta-powder’ for light-weight microwave absorption material design

Dielectric enhancement effect in biomorphic porous carbon-based iron@iron carbide ‘meta-powder’ for light-weight microwave absorption material design

High-performance microwave absorption enabled by Co3O4 modified VB-group laminated VS2 with frequency modulation from S-band to Ku-band

High performance microwave absorption (MA) materials especially those with tunable frequency are highly desirable for telecommunication industries and military camouflage in the information era. Herein, we constructed hierarchical heterostructures based on VB-group laminated vanadium disulfide (VS 2 ) nanosheets embedded with cobalt tetroxide (Co 3 O 4 ) nanoparticles. The highly dispersed Co 3 O 4 nanoparticles generate strong electromagnetic coupling networks that could enhance the loss properties of MA materials. Moreover, the interconnected VS 2 layered network results in dipolar/interfacial polarization, multiple reflection and scattering favorable for the enhanced MA performance. Impressively, the maximum reflection loss of the VS 2 /Co 3 O 4 hybrids containing 10% Co 3 O 4 can reach 57.96 dB at a thin thickness of 1.57 mm, and the bandwidth with an RL value less than -10 dB is as large as 3.5 GHz. The effective MA band could be adjusted in a range of 15.1 GHz (2.9-18 GHz) from S to Ku bands by the increase in thickness from 1.2 mm to 5.5 mm. The results show that the synergistic effect of multiple loss mechanisms and good impedance matching could be the reasons for strong MA capability in nearly all frequency bands, and thus, the high-performance and lightweight MA materials could be developed by the VS 2 /Co 3 O 4 hybrids.

Microwave absorption enhancement via graphene sheet-guided preparation of flake-like titanium carbide

With the development of electromagnetic technology, there is an urgent need for further research on highly efficient and lightweight microwave absorption materials. Transition metal carbides have drawn tremendous attention due to their strong microwave dissipation ability and perfect stability in extreme environments. However, owing to carburization under high temperatures, synthesizing metal carbides with specified morphology is still a challenge. Here, titanium carbide (TiC) with a flake-like structure was prepared through a carbothermic reduction method guided by two-dimensional graphene sheets. The prepared flake-like TiC sheets show excellent microwave absorption properties in 1–40 GHz compared with TiC spherical particles. A minimum reflection loss (RL) of −57.0 dB at 11.8 and 3.2 GHz effective absorption bandwidth (RL &amp;lt; −10 dB) was achieved. Meanwhile, an optimal RL of −57 dB is also achieved at 35.8 GHz together with an even broader absorption bandwidth from 34.2 to 40 GHz (5.8 GHz in total). This excellent microwave absorption performance is attributed to the flake-like morphology, which dramatically enhances the multiple polarization loss. The method of utilizing graphene sheets as a guide to fabricate flake-like TiC not only illuminates a new strategy for fabricating transition metal carbides with specified morphology but also provides an attractive candidate for microwave absorption applications.

General biotemplating of hierarchically ultra-vesicular microspheres for superior microwave absorption

The vesicular structure has elicited increasing interest in the field of lightweight microwave absorption (MA) materials. However, few methods exist to integrate both micro- and nanoscale vesicles within one nanoarchitecture. Herein, the high-yield and green biotemplate method is developed for the general synthesis of hierarchically ultra-vesicular microspheres (HUVMs), consisting of a hollow configuration and numerous multi-sized bubbles inside. HUVMs of metal oxides (SnO2, Co3O4, Fe2O3, and Mn2O3), their combinations, and magnetic metals (Co and CoNi) have been successfully prepared. Their synergistic multi-sized vesicles simultaneously enhance dielectric loss capacity by space charge polarization and satisfy impedance matching by large cavities, proved by electron holography. Eventually, both the SnO2 and Co HUVMs demonstrate first-rank MA performance covering almost the whole bandwidth from 2 to 18 GHz with ultrahigh absorption intensity beyond –40.0 dB. These achievements provide a new avenue for precise manipulation of ultra-porous structure and foreshadow an important direction of lightweight absorbents.

MOF-derived porous hollow Ni/C composites with optimized impedance matching as lightweight microwave absorption materials

MOF-derived porous hollow Ni/C composites with optimized impedance matching as lightweight microwave absorption materials

Light-weight 1D heteroatoms-doped Fe3C@C nanofibers for microwave absorption with a thinner matching thickness

Emergency situation of electromagnetic microwave pollution generated by daily electronic devices urgently requires light-weight and efficient microwave absorption materials with thin thickness and low filling ratio. Herein, the heteroatoms-doped Fe3C@C nanofibers are fabricated from a mixture solution of Iron (III) 2, 4-pentanedionate (Fe(acac)3) and nitrogen-containing polymer poly (phthalazinone ether nitrile ketone) (PPENK) by electrospinning and the following thermal treatment. The morphologies and compositions of nanofibers can be controlled by annealing temperature. The 1-Dimensional (1D) heteroatoms-doped Fe3C@C nanofibers display outstanding microwave absorption performance. When the filling ratio is 30 wt% in paraffin for nanofibers heat-treated in 700 ℃, the optimal reflection loss value is − 35.5 dB at 8.3 GHz with a thickness of 2.8 mm. Additionally, the maximal efficient absorption bandwidth reaches as wide as 4.9 GHz ranging from 13.1 to 18.0 GHz with a rather thin thickness of 1.6 mm. The Fe3C@C nanofibers have adjustable electromagnetic parameters and thus, balance impedance matching and microwave attenuation performance at the same time. This work investigates the relationship between microwave absorption performance and the chemical states of nitrogen atoms, revealing a facile strategy to prepare a multi-interface microwave absorber and presenting a candidate application for microwave absorption materials with low matching thickness.

Lightweight and robust cobalt ferrite/carbon nanotubes/waterborne polyurethane hybrid aerogels for efficient microwave absorption and thermal insulation

Lightweight and efficient microwave absorption materials with excellent heat-insulating ability and mechanical property are highly attractive in real applications, but the effective integration of these functions into one material by a simple approach remains an enormous challenge.