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 (RLmin) of − 60.3 dB with the lower filler content of 2 wt%. The RCS reduction value can reach 53.3 dB m2, 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.

Scheme 1. a) Schematic diagram of obtaining MXene nanoflakes by adopting a certain etching strategy. b) Schematic diagram of the potential EMA mechanism analysis of MXene structure. c) Schematic illustration of the multifunctional application of MXene composites.

In this paper, NiCo2S4 sulphide spinel nanoparticles are prepared using a modified solvothermal route, after which the obtained siegenite nanoparticles are tailored on graphite-like carbon nitride (g-C3N4) nanosheets. The morphology of tailored nanostructures is accomplished via an ion exchange process. Interestingly, the g-C3N4 stick structures are fabricated based on an innovative approach. Moreover, interfacial polarizations at heterojunction interfaces, and medium effects on microwave characteristics are examined, using polystyrene (PS) and polyvinylidene fluoride (PVDF) as polymeric matrices. The specimens are characterized via Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) analyses. The optical performance of nanostructures is studied by means of diffuse reflection spectroscopy (DRS) analysis, and is suggestive of a narrow band gap for NiCo2S4 and NiCo2S4/g-C3N4 nanostructures. Finally, the material’s microwave absorbing features are clarified using a vector network analyzer (VNA) instrument via a wave guide technique. The resulting significant microwave absorptions reveal that our g-C3N4/NiCo2S4/PVDF 40% nanocomposite exhibited seven notches of reflection loss (RL), more than 30 dB in its curve, at 1.75 mm in thickness, while its maximum RL was 59.39 dB at 13.07 GHz. Interestingly, this composite, in a mass fraction of 60%, illustrates an efficient bandwidth of 5.1 GHz (RL > 10 dB) at only 1 mm thickness. It is worth noting that the maximum RL of g-C3N4 stick structures/PVDF measures 74.53 dB at 14.86 GHz, with a broadband efficient bandwidth of 7.96 GHz (RL > 10 dB). More significantly, both g-C3N4/NiCo2S4/PVDF and NiCo2S4/PVDF demonstrated salient electromagnetic interference shielding effectiveness (SE) > 30 dB across both x- and ku-band frequencies.

In this study, a broadband, intense, novel, and promising microwave-absorbing nanocomposite was prepared using graphite-like carbon nitride (g-C 3 N 4 )/CuS suspended in poly(methyl methacrylate) (PMMA) medium. The g-C 3 N 4 nanosheets were synthesized by heating the urea as well as the CuS nanoparticles, and g-C 3 N 4 /CuS nanocomposites were prepared using a solvothermal method and then were separately molded by a PMMA solution to investigate their microwave-absorbing characteristics. The Fourier transform infrared and X-ray powder diffraction were used to characterize the g-C 3 N 4 , CuS, and CuS/g-C 3 N 4 nanostructures, which confirmed that the pure structure of the nanomaterials has been synthesized. The optical properties of the nanostructures were also investigated by diffuse reflection spectroscopy analysis. Accordingly, the Kubelka-Munk theory suggested significant narrow band gap for g-C 3 N 4 /CuS nanocomposite (0.27 eV), facilitating electron jumping and conductive loss. The morphology of the structures was examined using field emission scanning electron microscopy micrographs, illustrating that the uniform hexagonal structures of the CuS nanoplates have been formed and the CuS two-dimensional structures were uniformly distributed on the g-C 3 N 4 nanosheets. Finally, the microwave-absorbing properties of the CuS, g-C 3 N 4 , and g-C 3 N 4 /CuS were investigated by PMMA as a host. The microwaveabsorbing properties were evaluated using a vector network analyzer. The results illustrated that the maximum reflection loss of the g-C 3 N 4 /PMMA nanocomposite was −71.05 dB at 14.90 GHz with a thickness of 2.00 mm, demonstrating a 1.70 GHz bandwidth >30 dB, as well as g-C 3 N 4 /CuS/PMMA nanocomposite absorbed 7.30 GHz bandwidth of more than 10 dB with a thickness of 1.80 mm along the x-and ku-band frequency. The obtained results introduced the PMMA as a capable microwave-absorbing substrate. Besides, the g-C 3 N 4 /CuS/PMMA nanocomposite demonstrated metamaterial property and abundant attenuation constant.

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Aluminum‐doped strontium hexaferrite nanoparticle SrAl1.3Fe10.7O19 was prepared by sol–gel method and polyaniline (PANi) multiphase magnetic nanocomposite SrAl1.3Fe10.7O19/MWCNT/PANi was synthesized through a sonochemical method by in situ polymerization. The morphology, structure, and magnetic properties of the nanocomposites are investigated by field emission scanning electron microscopy, X‐ray powder diffraction, Fourier transform infrared spectroscopy, and vibrating sample magnetometer. The electromagnetic interference shielding efficiency was evaluated in the KU‐band (12.4–18 GHz). The reflection loss (RL) value showed that the composites have an excellent absorbing property in the KU‐band, minimum −24.93 dB at 16.40 GHz with a bandwidth of 2.81 GHz (shielding effectiveness up to 10 dB) at a matching thickness 6.5 mm. The RL value of the SrAl1.3Fe10.7O19/MWCNT nanocomposite was −15.92 dB at 15.84 GHz with a bandwidth of 1.66 GHz (with a shielding effectiveness up to 10 dB). These results disclose the remarkable microwave shielding ability of SrAl1.3Fe10.7O19/MWCNT/PANi in KU‐band due to the interactive effect of the three components. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45135.

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