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-di...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.展开更多
The synthesis of wide bandwidth,thin thickness,and high performance microwave absorbing materials has become a hot topic of current research.Metal-organic frameworks with heterojunctions and porous structures are cons...The synthesis of wide bandwidth,thin thickness,and high performance microwave absorbing materials has become a hot topic of current research.Metal-organic frameworks with heterojunctions and porous structures are considered as suitable candidates to meet these characteristics.Herein,heterogeneous CoFe@N-doped porous carbon polyhedron composites were successfully synthesized via Fe^(2+)to replace Co in zeolite imidazole frame-67.The dielectric properties of composites were enhanced by the replacement of Fe^(2+),and the synergistic effect of dielectric loss and magnetic loss was realized.The petal-like lamellar structure increases the travel of electromagnetic(EM)waves,and the formation of porous structures improves impedance matching.Specifically,a reflection loss of−67.30 dB was obtained at a thickness of 2.88 mm,and an ultrabroad wide effective absorption bandwidth of 8.40 GHz was obtained,covering most of the X-band(8–12 GHz)and the whole Ku-band(12–18 GHz).The radar cross section(RCS)reduction value can reach 29.4 dB·m^(2),which means that the radar detector has a smaller probability of detecting targets.This work describes the unique advantages of metal ion replacement metal-organic frameworks derived materials in structural design,impedance matching,and performance adjustment,and provides a new reference for the field of electromagnetic wave absorption.展开更多
Flexible pressure sensors have attracted great attention due to their potential in the wearable devices market and in particular in human-machine interactive interfaces.Pressure sensors with high sensitivity,wide meas...Flexible pressure sensors have attracted great attention due to their potential in the wearable devices market and in particular in human-machine interactive interfaces.Pressure sensors with high sensitivity,wide measurement range,and low-cost are now highly desired for such practical applications.In the present investigation,an ultrasensitive pressure sensor with wide measurement range has been successfully fabricated.Carbon nanotubes(CNTs)(uniformly sprayed on the surface of paper)comprise the sensitivity material,while lithographed interdigital electrodes comprise the substrate.Due to the synergistic effects of CNT’s high specific surface area,paper’s porous structure,interdigital electrodes’efficient contact with CNT,our pressure sensor realizes a wide measurement range from 0 to 140 kPa and exhibits excellent stability through 15,000 cycles of testing.For the paper-based CNT film/interdigitated structure(PCI)pressure sensor,the connection area between the sensitive material and interdigital electrodes dominates in the lowpressure region,while internal change within the sensitive materials plays the leading role in the high-pressure region.Additionally,the PCI pressure sensor not only displays a high sensitivity of 2.72 kPa–1(up to 35 kPa)but also can detect low pressures,such as that exerted by a resting mung bean(about 8 Pa).When attached to the surface of a human body,the pressure sensor can monitor physiological signals,such as wrist movement,pulse beats,or movement of throat muscles.Furthermore,the pressure sensor array can identify the spatial pressure distribution,with promising applications in humanmachine interactive interfaces.展开更多
The spatiotemporal characteristics of electromagnetic pulses with ultrabroad spectral bandwidth in the far field are analyzed by using classical scalar diffraction theory. The effects of the ratio of the frequency wid...The spatiotemporal characteristics of electromagnetic pulses with ultrabroad spectral bandwidth in the far field are analyzed by using classical scalar diffraction theory. The effects of the ratio of the frequency width to the central frequency on the diffraction spatial distribution are discussed. It is concluded that the diffraction spatial distribution of the pulsed radiation gets narrower than a monochromatic wave when the frequency width of the pulse is comparable to or larger than its central frequency.展开更多
基金financial support from the National Nature Science Foundation of China(No.51971111).
文摘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.
基金supported by the National Natural Science Foundation of China(No.52102036)the Sichuan Science and Technology Program(No.2021JDRC0099).
文摘The synthesis of wide bandwidth,thin thickness,and high performance microwave absorbing materials has become a hot topic of current research.Metal-organic frameworks with heterojunctions and porous structures are considered as suitable candidates to meet these characteristics.Herein,heterogeneous CoFe@N-doped porous carbon polyhedron composites were successfully synthesized via Fe^(2+)to replace Co in zeolite imidazole frame-67.The dielectric properties of composites were enhanced by the replacement of Fe^(2+),and the synergistic effect of dielectric loss and magnetic loss was realized.The petal-like lamellar structure increases the travel of electromagnetic(EM)waves,and the formation of porous structures improves impedance matching.Specifically,a reflection loss of−67.30 dB was obtained at a thickness of 2.88 mm,and an ultrabroad wide effective absorption bandwidth of 8.40 GHz was obtained,covering most of the X-band(8–12 GHz)and the whole Ku-band(12–18 GHz).The radar cross section(RCS)reduction value can reach 29.4 dB·m^(2),which means that the radar detector has a smaller probability of detecting targets.This work describes the unique advantages of metal ion replacement metal-organic frameworks derived materials in structural design,impedance matching,and performance adjustment,and provides a new reference for the field of electromagnetic wave absorption.
基金the funding support from the National Natural Science Foundation of China (51605449, 51675493 and 51705476)Shanxi “1331 Project” Key Subject Construction (1331KSC)
文摘Flexible pressure sensors have attracted great attention due to their potential in the wearable devices market and in particular in human-machine interactive interfaces.Pressure sensors with high sensitivity,wide measurement range,and low-cost are now highly desired for such practical applications.In the present investigation,an ultrasensitive pressure sensor with wide measurement range has been successfully fabricated.Carbon nanotubes(CNTs)(uniformly sprayed on the surface of paper)comprise the sensitivity material,while lithographed interdigital electrodes comprise the substrate.Due to the synergistic effects of CNT’s high specific surface area,paper’s porous structure,interdigital electrodes’efficient contact with CNT,our pressure sensor realizes a wide measurement range from 0 to 140 kPa and exhibits excellent stability through 15,000 cycles of testing.For the paper-based CNT film/interdigitated structure(PCI)pressure sensor,the connection area between the sensitive material and interdigital electrodes dominates in the lowpressure region,while internal change within the sensitive materials plays the leading role in the high-pressure region.Additionally,the PCI pressure sensor not only displays a high sensitivity of 2.72 kPa–1(up to 35 kPa)but also can detect low pressures,such as that exerted by a resting mung bean(about 8 Pa).When attached to the surface of a human body,the pressure sensor can monitor physiological signals,such as wrist movement,pulse beats,or movement of throat muscles.Furthermore,the pressure sensor array can identify the spatial pressure distribution,with promising applications in humanmachine interactive interfaces.
基金the National NaturalScience Foundation of China (Grant No. 39890390) and the State Key Basic Research and Development Program (Grant No. G1998010102).
文摘The spatiotemporal characteristics of electromagnetic pulses with ultrabroad spectral bandwidth in the far field are analyzed by using classical scalar diffraction theory. The effects of the ratio of the frequency width to the central frequency on the diffraction spatial distribution are discussed. It is concluded that the diffraction spatial distribution of the pulsed radiation gets narrower than a monochromatic wave when the frequency width of the pulse is comparable to or larger than its central frequency.
