Ultrabroad Microwave Absorption Ability and Infrared Stealth Property of Nano-Micro CuS@rGO Lightweight Aerogels

Developing ultrabroad radar-infrared compatible stealth materials has turned into a research hotspot,which is still a problem to be solved.Herein,the copper sulfide wrapped by reduced graphene oxide to obtain three-dimensional(3D)porous network composite aerogels(CuS@rGO)were synthesized via thermal reduction ways(hydrothermal,ascorbic acid reduction)and freeze-drying strategy.It was discovered that the phase components(rGO and CuS phases)and micro/nano structure(microporous and nanosheet)were well-modified by modulating the additive amounts of CuS and changing the reduction ways,which resulted in the variation of the pore structure,defects,complex permittivity,microwave absorption,radar cross section(RCS)reduction value and infrared(IR)emissivity.Notably,the obtained CuS@rGO aerogels with a single dielectric loss type can achieve an ultrabroad bandwidth of 8.44 GHz at 2.8 mm with the low filler content of 6 wt%by a hydrothermal method.Besides,the composite aerogel via the ascorbic acid reduction realizes the minimum reflection loss(RL_(min))of−60.3 dB with the lower filler content of 2 wt%.The RCS reduction value can reach 53.3 dB m^(2),which effectively reduces the probability of the target being detected by the radar detector.Furthermore,the laminated porous architecture and multicomponent endowed composite aerogels with thermal insulation and IR stealth versatility.Thus,this work offers a facile method to design and develop porous rGO-based composite aerogel absorbers with radar-IR compatible stealth.

Research on Infrared Emissivity and Laser Reflectivity of Sn_(1−x)Er_(x)O_(2)Micro/Nanofibers Based on First-Principles

Sn_(1−x)Er_(x)O_(2)(x=0%,8%,16%,24%)micro/nanofibers were prepared by electrospinning combined with heat treatment using erbium nitrate,stannous chloride and polyvinylpyrrolidone(PVP)as raw materials.The target products were characterized by thermogravimetric analyzer,X-ray diffrotometer,fourier transform infrared spectrometer,scanning electron microscope,spectrophotometer and infrared emissivity tester,and the effects of Er^(3+)doping on its infrared and laser emissivity were studied.At the same time,the Sn_(1−x)Er_(x)O_(2)(x=0%,16%)doping models were constructed based on the first principles of density functional theory,and the related optoelectronic properties such as their energy band structure,density of states,reflectivity and dielectric constant were analyzed,and further explained the mechanism of Er^(3+)doping on SnO_(2)infrared emissivity and laser absorption from the point of electronic structure.The results showed that after calcination at 600℃,single rutile type SnO_(2)was formed,and the crystal structure was not changed by doping Er^(3+).The calcined products showed good fiber morphology,and the average fiber diameter was 402 nm.The infrared emissivity and resistivity of the samples both decreased first and then increased with the increase of Er^(3+)doping amount.When x=16%,the infrared emis-sivity of the sample was at least 0.71;and Er^(3+)doping can effectively reduce the reflectivity of SnO_(2)at 1.06μm and 1.55μm,when x=16%,its reflectivity at 1.06μm and 1.55μm are 50.5%and 40%,respectively,when x=24%,the reflectivity at 1.06μm and 1.55μm wavelengths are 47.3%and 42.1%,respectively.At the same time,the change of carrier concentration and electron transition before and after Er^(3+)doping were described by first-principle calculation,and the regulation mechanism of infrared emissivity and laser reflectivity was explained.This study provides a certain experimental and theoretical basis for the development of a single-type,light-weight and easily prepared infrared and laser compatible-stealth material.

Asymmetric electric field distribution enhanced hierarchical metamaterials for radar-infrared compatible camouflage

Metamaterials are widely used in electromagnetic radiation and camouflage for their flexible wavefront manipulation and polarization over a broad spectrum ranging from microwaves to optics.However,multispectral compatible camouflage faces significant challenges due to tremendous scale differences of unit cells and desired radiative properties in various spectral regimes.This study assembles a micron-scale infrared emitter,a millimeter-scale microwave absorber,and a metal reflector to propose a hierarchical metamaterial that reduces microwave scattering and reflects low-infrared waves.As a proof of concept,laser etching micro-manufactures an upper infrared shielding layer with a periodic metal pattern.At the same time,bottom square frustum metastructure composites are fabricated and optimized based on genetic algorithms.Under the normal incidence transverse electromagnetic wave with a 90°azimuth angle,the hierarchical strategy and infrared unit create an asymmetric electric field distribution of local near-field coupling,which is conducive to generating additional resonance for broadening the absorption bandwidth.Experiments verify the multispectral camouflage,which shows a high absorption efficiency of more than 90%,ranging from 3.6 to 6.2 and from 8.4 to 18 GHz with a total thickness of 4.05 mm(0.049λmax).Due to the non-reflection of surrounding thermal signals in the infrared 2-22μm region,low-infrared emissivity(0.29)metamaterials can adapt to various thermal backgrounds.This methodology can provide a novel route for fabricating multispectral camouflage devices.