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.
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.
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.
Highlights
The microwave absorbing performance of alloy@C composites can be controlled through regulating ratio of metal ions.
Carbon-based alloy@C composites exhibit the potential stability of ...microwave absorption with almost the whole Ku band for the practical application.
Magnetic/dielectric@porous carbon composites, derived from metal–organic frameworks (MOFs) with adjustable composition ratio, have attracted wide attention due to their unique magnetoelectric properties. In addition, MOFs-derived porous carbon-based materials can meet the needs of lightweight feature. This paper reports a simple process for synthesizing stacked Co
x
Ni
y
@C nanosheets derived from Co
x
Ni
y
-MOFs nanosheets with multiple interfaces, which is good to the microwave response. The Co
x
Ni
y
@C with controllable composition can be obtained by adjusting the ratio of Co
2+
and Ni
2+
. It is supposed that the increased Co content is benefit to the dielectric and magnetic loss. Additionally, the bandwidth of CoNi@C nanosheets can take up almost the whole Ku band. Moreover, this composite has better environmental stability in air, which characteristic provides a sustainable potential for the practical application.
The development of infrared‐radar compatible materials/devices is challenging because the requirements of material properties between infrared and radar stealth are contradictory. Herein, a composite ...of poly(3, 4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) coated melamine foam is designed to integrate the advantages of the dual materials and the created heterogeneous interface between them. The as‐designed PEDOT:PSS@melamine composite shows excellent mechanical properties, outstanding thermal insulation, and improved thermal infrared stealth performance. The relevant superb radar stealth performance including the minimum reflection loss value of −57.57 dB, the optimum ultra‐wide bandwidth of 10.52 GHz, and the simulation of radar cross section reduction value of 17.68 dB m2, can be achieved. The optimal specific electromagnetic wave absorption performance can reach up as high as 3263.02 dB·cm3 g−1. The average electromagnetic interference shielding effectiveness value can be 30.80 dB. This study provides an approach for the design of high‐performance stealth materials with infrared‐radar compatibility.
A high‐performance infrared‐radar compatible stealth composite is fabricated. The actual radar cross‐section performance is rationally simulated via smart computer simulation technology.
In order to fulfill the ever-growing requirements for electromagnetic interference (EMI) shielding materials, achieving a high efficiency with great flexibility is still a big challenge. Herein, ...high-performance EMI shielding composite films with excellent mechanical properties were fabricated
via
a convenient evaporation method using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and silver nanowires (Ag NWs) as conductive fillers. By adding 1.38 wt% Ag NWs into the original polyvinyl alcohol/PEDOT: PSS (PVA/PEDOT:PSS) composite, the obtained film with a thickness of about 20 µm shows a remarkable EMI shielding performance (~33 dB) and a special EMI shielding efficiency of 16,800 dB cm
−1
at 10 GHz. Furthermore, PVA/PEDOT: PSS/Ag NWs films present excellent tensile strength (~62.39 MPa) and elongation at break (~29.3%). The good mechanism allows the films to apply in actual harsh environments. Overall, this study will draw attention to the new films for electromagnetic shielding application.
Carbon nanofibers were widely utilized to improve microwave absorption properties since they are a promising lightweight candidate. Adjustable conductive nanostructures of carbon nanofibers were ...synthesized by electrospinning technique. The conductive network is controlled by the polyvinyl pyrrolidone (PVP) content due to the special hygroscopicity of PVP. The increased adhesive contacts of nanofibers provide more transmission paths for electrons to reduce the effect of air dielectric. Satisfactorily, the carbon nanofibers that carbonized from the polyacrylonitrile (PAN) and PVP (the mass ratio is 6:4) show excellent microwave absorption performance. The minimum reflection loss (RL) value is -51.3 dB at 15.2 GHz and the maximum effective absorption frequency width (<-10 dB) is 5.1 GHz with the matching thickness of only 1.8 mm. Thereby, we believe that this research may offer an effective way to synthesize lightweight carbon nanofibers microwave absorbents.
Changing the metallic card clothing on a carding machine is costly when the spinning mills want to card different fibers from cotton to terylene or vice versa. This article proposes a newly developed ...cylinder card clothing compatible with cotton and terylene fibers by Nb alloying of AISI 1090 steel so that the spinning mills can change the type of fiber without changing the card clothing. Based on an idea developed from classical carding balance theory to study the adaptability of the cylinder card clothing for cotton and terylene fibers, the wall shear stress was used as the basis for compatibility analysis of carding behavior and bearing capacity with cotton and terylene fibers and as the focus of this study. Nb alloying of AISI 1090 steel showed good wear resistance in carding areas after heat treatment with high hardness above 840 Hv
and extremely fine grain grade of 13.5 class, which increased about 25% compared to conventional 80 WV. The testing results in the spinning mills, including one cotton and two terylene fibers, showed good performance with this newly developed card clothing. In conclusion, the card clothing made of Nb alloying of AISI 1090 steel can handle different fibers with acceptable carding performance.
The design of metallic card clothing, which is one of the most important devices in the textile industry, has always been based on operational experience. With the development of types of fibers and ...the requirements for the quality of yarns, those principles concluded by engineers seem to be losing their efficiency. Recent research found that airflow played an important role in the card process, which means airflow should be carefully studied. Computational fluid dynamics (CFD) simulation greatly helps in the analysis of airflow because the gauge between carding elements is too narrow to put in any measuring device. In the present study, with the help of CFD simulation, the air around different carding clothing with varied tooth depth was analyzed. It was concluded that the carding efficiency improvement in card clothing with lower tooth depth may be related to more concentrated air velocity at the tooth tips. This resulted in more probabilities that fibers would get through the cylinder surface at the teeth tips, so that the fibers could be caught by flat-top needles more efficiently. With this assumption, a new generation of card clothing called “double teeth” containing two teeth in a single section has been invented. The new configuration design of card clothing was then applied in several spinning mills on an industrial scale for experiments. The results showed about a 30% improvement in production at the same quality level as conventional card clothing, which implied the usefulness of the newly applied principles related to airflow. Despite the difficulty in the study of the complex carding process, the new airflow analysis method has shown an optional and worthwhile way of thinking that could make a difference in future research in the textile industry.
The electromagnetic simulation can be used to design the macroscopic absorbing structure of the microwave absorbing material. Research indicates that the macrostructure can adjust the impedance ...matching and electromagnetic properties of the materials, thereby improving the absorption performance. Among them, the honeycomb structure is often used in actual products due to its good absorption characteristics and mechanical properties. Therefore, in this work, the absorption performance of the carbon microsphere material was improved through the honeycomb structure design. The carbon microsphere material is firstly prepared by sintering phenolic resin, which has the advantages of convenient synthesis, high yield, and a narrow absorption bandwidth of 4.4 GHz. Then, through the high frequency structure simulator (HFSS) electromagnetic simulation, the honeycomb structure based on the carbon microspheres was macroscopically designed, achieving a larger 8.3 GHz absorption frequency bandwidth. This research completed the combination of electromagnetic simulation and honeycomb structure, improved the absorption bandwidth of carbon microspheres, and opened up a new way for the further improvement and practical application for traditional absorption materials.
PDF
