Highlights
The eco-friendly shaddock peel-derived carbon aerogels were prepared by a freeze-drying method.
Multiple functions such as thermal insulation, compression resistance and microwave ...absorption can be integrated into one material-carbon aerogel.
Novel computer simulation technology strategy was selected to simulate significant radar cross-sectional reduction values under real far field condition.
.
Eco-friendly electromagnetic wave absorbing materials with excellent thermal infrared stealth property, heat-insulating ability and compression resistance are highly attractive in practical applications. Meeting the aforesaid requirements simultaneously is a formidable challenge. Herein, ultra-light carbon aerogels were fabricated via fresh shaddock peel by facile freeze-drying method and calcination process, forming porous network architecture. With the heating platform temperature of 70 °C, the upper surface temperatures of the as-prepared carbon aerogel present a slow upward trend. The color of the sample surface in thermal infrared images is similar to that of the surroundings. With the maximum compressive stress of 2.435 kPa, the carbon aerogels can provide favorable endurance. The shaddock peel-based carbon aerogels possess the minimum reflection loss value (
RL
min
) of − 29.50 dB in X band. Meanwhile, the effective absorption bandwidth covers 5.80 GHz at a relatively thin thickness of only 1.7 mm. With the detection theta of 0°, the maximum radar cross-sectional (RCS) reduction values of 16.28 dB m
2
can be achieved. Theoretical simulations of RCS have aroused extensive interest owing to their ingenious design and time-saving feature. This work paves the way for preparing multi-functional microwave absorbers derived from biomass raw materials under the guidance of RCS simulations.
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It is still a formidable challenge to ameliorate the low-frequency electromagnetic property of conventional microwave-absorbing materials, which may be conquered by the coexistence of both strong ...dielectric and magnetic loss ability in low-frequency range and the perfect balance between complex permittivity and permeability with the help of structural design. Herein, by virtue of appropriate composition and structure of Co3HCOO6·dimethylformamide parallelepipeds, one-dimensional spongelike metallic Co can be directly synthesized for the first time with strong magnetic loss in the low-frequency range. Furthermore, attenuation ability and impedance matching condition have been improved through the construction of interfacial structures between inner cobalt and surface carbon. With the structure of carbon changed from fragments to vertically aligned nanoflakes and eventually to a thick layer with extra fragments, the dielectric loss would be continuously strengthened, while the magnetic loss maintains well, followed by a remarkable decline. A perfect balance between dielectric and magnetic loss has been achieved by sample S-Co/C-0.3 with minimum reflection loss value around −20 dB and effective absorption frequency range about 3.84 GHz in the C band. Excellent microwave absorption performance can also be realized in X and Ku bands. In addition, as-prepared Co and Co/C composites can also be potentially applied in electromagnetic shielding. The findings may pave the way for the manufacture of metal-based metal–organic framework derivatives and the design of lightweight low-frequency electromagnetic materials.
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IJS, KILJ, NUK, PNG, UL, UM
Highlights
A flexible and lightweight microwave absorber was prepared by a vacuum filtration method.
The remarkable microwave absorbency makes the absorber paper attractive in wireless wearable ...electronics field.
Developing a flexible, lightweight and effective electromagnetic (EM) absorber remains challenging despite being on increasing demand as more wearable devices and portable electronics are commercialized. Herein, we report a flexible and lightweight hybrid paper by a facile vacuum-filtration-induced self-assembly process, in which cotton-derived carbon fibers serve as flexible skeletons, compactly surrounded by other microwave-attenuating components (reduced graphene oxide and Fe
3
O
4
@C nanowires). Owing to its unique architecture and synergy of the three components, the as-prepared hybrid paper exhibits flexible and lightweight features as well as superb microwave absorption performance. Maximum absorption intensity with reflection loss as low as − 63 dB can be achieved, and its broadest frequency absorption bandwidth of 5.8 GHz almost covers the entire Ku band. Such a hybrid paper is promising to cope with ever-increasing EM interference. The work also paves the way to develop low-cost and flexible EM wave absorber from biomass through a facile method.
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ABO
3
perovskites, owning unique properties, have great research prospect in electromagnetic wave absorption field. Normally, doping can significantly regulate the dielectric loss, whereas the ...magnetic loss can be ignored. In this work, the crystal structure and electromagnetic properties can be regulated systematically by the K, Fe co-doping for LaCoO
3
perovskites (LKCFO) under the condition of fixed F content. In addition, the obtained samples show the obvious interfacial polarization effect on accounting to the small size effect, which is conducive to the effective microwave absorption. By analyzing the evolution of the positron annihilation lifetime and the first-principles calculation of the oxygen density of states for the series of LKCFO perovskites, it is found that the charge transport characteristics will be controlled by the point defect generated by allelic doping. The point defect content decreases and then increases as the doping level rises. The prepared perovskite exhibits the lowest defect density and the largest dielectric loss capability, which indicates that the lower point defects promote electron migration and thus enhance the dielectric loss; thus, the electromagnetic wave absorption bandwidth up to 6.2 GHz is reached. In contrast, both insufficient and excessive K doping are detrimental to the enhancement of microwave absorption. Especially, the practical application value was investigated using Computer Simulation Technology (CST) simulations. The LKCFO-2 exhibits the smallest RCS value (below −10 dBm
2
) at almost −90°–90° with a thickness of 2 mm, providing an effective method for study excellent microwave absorption and scattering property.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A symmetrical Fe2O3/BaCO3 hexagonal cone structure having a height of 10 um and an edge length of -4um is reported, obtained using a common solvothermal process and a mirror growth process. Focused ...ion beam and high-resolution transmission electron microscopy techniques revealed that α-Fe2O3 was the single crystal feature present. Ba ions contributed to the formation of symmetrical structures exhibited in the final composites. Subsequently, porous magnetic symmetric hexagonal cone structures were used to study the observed intense electromagnetic wave interference. Electromagnetic absorption performance studies at 2-18 GHz indicated stronger attenuation electromagnetic wave ability as compared to other shapes such as spindles, spheres, cubes, and rods. The maximum absorption frequency bandwidth was at 7.2 GHz with a coating thickness d = 1.5 mm. Special structures and the absence of BaCO3 likely played a vital role in the excellent electromagnetic absorption properties described in this research.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Dielectric materials are eternal jewels in the view of research due to their strong dissipation ability, low density and higher stability compared to those of magnetic materials. Regarding the ...significance of permittivity to characterize the dielectric properties of dielectrics, an in-depth and systematical investigation of dielectric polarization process has become quite necessary. Updated and critical surveys of the key factors determining permittivity, dielectric polarization in single-component system, dielectric polarization in multi-component system and related polarization relaxation are all highlighted. In addition, the challenges for dielectric polarization and polarization relaxation, the prospects for further exploration in electromagnetic wave absorption are also discussed. In short, this review provides a brief but systematic introduction to dielectric polarization and related polarization relaxation in electromagnetic wave absorption, which motivates further study of dielectric absorbers in microwave absorption field.
•Key factors determining permittivity are discussed.•Dielectric polarizations in single-component system are discussed.•Dielectric polarizations in multi-component system are discussed.•Related polarization relaxations are also highlighted.•The prospects for further exploration in electromagnetic wave absorption are proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Potassium-ion batteries (PIBs) have been considered as promising alternatives to lithium-ion batteries due to potassium's high natural abundance of 2.09 wt% (
vs.
0.0017 wt% for Li) and K/K
+
having ...a low redox potential of −2.93 V (
vs.
−2.71 V for Na/Na
+
). However, PIB electrodes still suffer huge challenges due to the large K-ion radius and slow reaction dynamics. Herein, we report a high-capacity Sb@CSN composite anode with Sb nanoparticles uniformly encapsulated by a carbon sphere network (CSN) for PIBs. First-principles computations and electrochemical characterization confirm a reversible sequential phase transformation of KSb
2
, KSb, K
5
Sb
4
, and K
3
Sb during the potassiation/depotassiation process. In a concentrated 4 M KTFSI/EC + DEC electrolyte, the Sb@CSN anode delivers a high reversible capacity of 551 mA h g
−1
at 100 mA g
−1
after 100 cycles with an extremely slow capacity decay of only 0.06% per cycle from the 10th to 100th cycle; when at a high current density of 200 mA g
−1
, the Sb@CSN anode still maintains a capacity of 504 mA h g
−1
after 220 cycles. The Sb@CSN anodes demonstrate one of the best electrochemical performances for all K-ion battery anodes reported to date. The exceptional performance of Sb@CSN should be attributed to the efficient encapsulation of small Sb nanoparticles in the conductive carbon network as well as the formation of a robust KF-rich SEI layer on the Sb@CSN anode in the concentrated 4 M KTFSI/EC + DEC electrolyte.
As electromagnetic absorbers with wide absorption bandwidth are highly pursued in the cutting-edge electronic and telecommunication industries, the traditional dielectric or magnetic bulky absorbers ...remain concerns of extending the effective absorption bandwidth. In this work, a dual-principle strategy has been proposed to make a better understanding of the impact of utilizing conductive absorption fillers coupled with implementing artificial structures design on the absorption performance. In the comparison based on the microscopic studies, the carbon nanotubes (CNTs)-based absorbers are confined to narrow operating bandwidth and relatively fixed response frequency range, which can not fulfill the ever-growing demands in the application. With subsequent macroscopic structure design based on the CNTs-based dielectric fillers, the artificial patterns show much more broadened absorption bandwidth, covering the majority of C-band, the whole X-band, and Ku-band, due to the tailored electromagnetic parameters and more reflections and scatterings. The results suggest that the combination of developing microscopic powder/bulky absorbers and macroscopic configuration design will fundamentally extend the effective operating bandwidth of microwave.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Highlights
The reduced graphene oxide (rGO) decorated silver nanowire (Ag NW) films were prepared by spray-coating method.
A highly efficient conductive network was constructed by Ag NW and rGO, ...achieving superior electromagnetic interference shielding effectiveness of 33.62 dB with a high transmittance of 81.9%.
The top rGO layer enables the hybrid film with reliable durability, chemical and thermal stabilities.
Silver nanowire (Ag NW) has been considered as the promising building block for the fabrication of transparent electromagnetic interference (EMI) shielding films. However, the practical application of Ag NW-based EMI shielding films has been restricted due to the unsatisfactory stability of Ag NW. Herein, we proposed a reduced graphene oxide (rGO) decorated Ag NW film, which realizes a seamless integration of optical transparency, highly efficient EMI shielding, reliable durability and stability. The Ag NW constructs a highly transparent and conductive network, and the rGO provides additional conductive path, showing a superior EMI shielding effectiveness (SE) of 33.62 dB at transmittance of 81.9%. In addition, the top rGO layer enables the hybrid film with reliable durability and chemical stability, which can maintain 96% and 90% EMI SE after 1000 times bending cycles at radius of 2 mm and exposure in air for 80 days. Furthermore, the rGO/Ag NW films also possess fast thermal response and heating stability, making them highly applicable in wearable devices. The synergy of Ag NW and rGO grants the hybrid EMI shielding film multiple desired functions and meanwhile overcomes the shortcomings of Ag NW. This work provides a reference for preparing multifunctional integrated transparent EMI shielding film.
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