Two Birds with One Stone: Broadband Electromagnetic Wave Absorption and Anticorrosion Performance in 2-18 GHz for Prussian Blue Analog Derivatives Aimed for Practical Applications.

Nowadays, the exploration of electromagnetic (EM) wave absorbers with anticorrosion to improve the survivability and environmental adaptability of military targets in the harsh environments is becoming an attractive and unavoidable challenge. Herein, through modulation of the metal composition in the precursors, the core@shell structure Prussian blue analog-derived NiCo@C, CoFe@C, NiFe@C, and NiCoFe@C are obtained with excellent EM wave absorption performance. As for NiCoFe@C, ascribed to the coupling effect of the dual magnetic alloy, a minimum reflection loss (RL) of -47.6 dB and an effective absorption bandwidthof 5.83 GHz are realized, which cover the whole Ku-band. Meanwhile, four absorbers display the lower corrosion current density (10-4 -10-6 A cm-2 ) and larger polarization resistance (104 -106  Ω) under acid, neutral, and alkaline corrosion conditions over uninterrupted 30 days. Furthermore, due to the spatial barrier effect and the passivation effect of the graphitic carbon shell , the continuous salt spray test has little effect on RL performance and inconspicuously changes the surface morphologies of coating, demonstrating its excellent bifunctional performance. This work lays the foundation for the development of metal-organic frameworks-derived materials with both anticorrosion and EM wave absorption performance.

Simulation and Design of a Prism-Type Ultra-Broadband Microwave Absorber Based on Magnetic Powder/Silica Gel Composites.

Materials that absorb electromagnetic waves over an ultra-wide frequency band have great potential for military and civilian applications. In this study, a square-frustum-type metamaterial structure was designed and prepared using CI/silica gel composites and flake-shaped FeNi/silica gel composites as the filling substrate. The structural parameters of the square frustum were simulated and optimized using CST Studio Suite. The results show that the optimal performance was achieved when the base consisted of 50 vol.% CI/silica gel composites and 25 vol.% FeNi/silica gel composites with a cross-pattern distribution, the square frustum consisted of 50 vol.% CI/silica gel composites, and the total thickness, base thickness, base-edge length, and top-edge lengths were 5, 1.8, 2.5, and 1.5 mm, respectively. This arrangement can effectively absorb frequencies between 1.8 and 40 GHz, realizing ultra-broadband absorption. The excellent absorption performance of the absorber is attributed to multiple quarter-wavelength resonances and edge diffraction effects.

Dumbbell-Like Fe3O4@N-Doped Carbon@2H/1T-MoS2 with Tailored Magnetic and Dielectric Loss for Efficient Microwave Absorbing.

Ferroferric oxide (Fe3O4)/C composites have received much attention as a result of converting electromagnetic waves to heat for harvesting efficient electromagnetic wave (EMW) absorbing performance. However, the practical EMW absorbing of these absorbers is still greatly hindered by the unmatched impedance properties and limited EMW absorbing ability. Tuning the morphologies at nanoscale and assembling the nanoarchitecture construction are essential to address this issue. Herein, dumbbell-like Fe3O4@N-doped carbon (NC)@2H/1T-MoS2 yolk-shell nanostructures are rationally designed and fabricated via a facile etching and wet chemical synthesis strategy. By manipulating the etching time toward the magnetic Fe3O4 component, the dielectric and magnetic loss of absorbers could be well-tuned, thus achieving the optimized impedance characteristics. As a result, the maximum refection losses (RLmaxs) of Fe3O4@NC-9h and Fe3O4@NC-15h are -19.8 dB@7.9 GHz and -39.5 dB@8.3 GHz, respectively. Moreover, the MoS2 nanosheets with a mixed 2H/1T phase anchored on Fe3O4@NC-15h (Fe3O4@NC-15h@MoS2) further boost the RLmax to -68.9 dB@5.8 GHz with an effective absorbing bandwidth of ∼5.25 GHz. The tailored synergistic effect between dielectric and magnetic loss and the introduced interfacial polarization (Fe3O4@NC/MoS2) are discussed to explain the drastically enhanced microwave absorbing ability. This work opens up new possibilities for effective manipulation of electromagnetic wave attenuation performance in magnetic-dielectric-type nanostructures.

Ultrathin MoS2 Nanosheets Encapsulated in Hollow Carbon Spheres: A Case of a Dielectric Absorber with Optimized Impedance for Efficient Microwave Absorption.

A dielectric loss-type electromagnetic wave (EMW) absorber, especially over a broad frequency range, is important yet challenging. As the most typical dielectric attenuation absorber, carbon-based nanostructures were highly pursued and studied. However, their poor impedance-matching issues still exist. Here, to further optimize dielectric properties and enhance reflection loss, ultrathin MoS2 nanosheets encapsulated in hollow carbon spheres (MoS2@HCS) were prepared via a facile template method. The diameter and shell thickness of the as-prepared HCSs were ∼250 and ∼20 nm. The encapsulated MoS2 nanosheets presented high dispersity and crystallinity. Compared to a pure HCS or MoS2 absorber, MoS2@HCS exhibited an optimized impedance characteristic, which can be attributed to the synergistic effects between HCSs (ensuring rapid electron transmission and compensating the low conductivity of MoS2) and MoS2 nanosheets (exposing sufficient numbers of active sites for polarizations and multi-reflection). Consequently, the MoS2@HCS was endowed with -65 dB EMW attenuation ability under 2 mm and the effective attenuation bandwidth under -20 dB was ∼3.3 GHz over the K-band under 1.2 mm and ∼3.4 GHz over the Ka-band under merely 0.7 mm. These results suggested that the MoS2@HCS is a promising dielectric absorber for practical applications. Meanwhile, this work introduces a facile and versatile strategy, which could in principle be extended to other transition metal sulfide@HCS for designing novel EMW absorbers.

A skin-inspired tactile sensor for smart prosthetics.

Recent achievements in the field of electronic skin have provided promising technology for prosthetic systems. However, the development of a bionic tactile-perception system that exhibits integrated stimuli sensing and neuron-like information-processing functionalities in a low-pressure regime remains a challenge. Here, we demonstrate a tactile sensor for smart prosthetics based on giant magneto-impedance (GMI) material embedded with an air gap. The sensor exhibits a high sensitivity of 120 newton-1 (or 4.4 kilopascal-1) and a very low detection limit of 10 micronewtons (or 0.3 pascals). The integration of the tactile sensor with an inductance-capacitance (LC) oscillation circuit enabled direct transduction of force stimuli into digital-frequency signals. The frequency increased with the force stimuli, consistent with the relationship between stimuli and human responses. The minimum loading of 50 micronewtons (or 1.25 pascals), which is less than the sensing threshold value of human skin, was also encoded into the frequency, similar to the pulse waveform of humans. The proposed tactile sensor not only showed desirable sensitivity and low detection limit but also exhibited transduction of digital-frequency signals like human stimuli responses. These features of the GMI-based tactile sensor show potential for its applications in smart prosthetics, especially prosthetic limbs that can functionally replace natural limbs.