Given tunable hybridization structures in solid solutions, fascinating electromagnetic (EM) properties can be achieved for regulating EM wave (EMW) absorption. Herein, a novel metal–organic cooperative interactions method is proposed to manipulate the vacancy, interstitial, substitutional, and heterointerface structures in molybdenum disulfide (MoS2) solid solution simultaneously, thence meeting the synergistic polarization loss on various point and face sites. Assisted by the coordination between Cu2+ and polydopamine (PDA), the effect of Cu modification on MoS2 is highly improved, which further lead to polarization loss on S vacancy, interstitial Cu, substitutional N, and heterointerface between carbon and MoS2. Contributing to the synergetic effect among multiple polarizations, the Cu/C@MoS2 solid solution exhibit ultrahigh EMW absorption performance, of which EMA with twice PDA delivers the effective absorption bandwidth of 7.12 GHz and minimum reflection loss of −48.22 dB (2.5 mm). The energy attenuation of Cu/C@MoS2 improved almost 266.7% and 222.2% than C@MoS2 and Cu@MoS2, respectively. Finally, this work reveals the structural dependency of solid solution materials of EMW absorption and establishes an entirely new polarization loss model.
Demand for electromagnetic wave (EMW) absorbers continues to increase with technological advances in wearable electronics and military applications. In this study, a new strategy to overcome the drawbacks of current absorbers by employing the co‐contribution of functional polymer frameworks and liquids with strong EMW absorption properties is proposed. Strongly polar water, dimethyl sulfoxide/water mixtures, and highly conductive 1‐ethyl‐3‐methylimidazolium ethyl sulfate ([EMI][ES]) are immobilized in dielectrically inert polymer networks to form different classes of gels (hydrogels, organogels, and ionogels). These gels demonstrate a high correlation between their dielectric properties and polarity/ionic conductivity/non‐covalent interaction of immobilized liquids. Thus, the EMW absorption performances of the gels can be precisely tuned over a wide range due to the diversity and stability of the liquids. The prepared hydrogels show good shielding performance (shielding efficiency > 20 dB) due to the high dielectric constants, while organogels with moderate attenuation ability and impedance matching achieve full‐wave absorption in X‐band (8.2–12.4 GHz) at 2.5 ± 0.5 mm. The ionogels also offer a wide effective absorption bandwidth (10.79–16.38 GHz at 2.2 mm) via prominent ionic conduction loss. In short, this work provides a conceptually novel platform to develop high‐efficient, customizable, and low‐cost functional absorbers.
We present a numerical study of nanosecond pulsed dielectric barrier discharge (DBD) actuator operating in quiescent air at atmospheric condition. Our study concentrates on plasma discharge induced fluid dynamics and on exploration of parametric space of interest for voltage pulse in an attempt to shed some light into elucidation of the mechanisms whereby the generated shock wave propagates through and affects the external flow. Specifically, a one-dimensional, self-similar, local ionization kinetic model recently developed to predict key parameters of nanosecond pulsed plasma discharge is coupled with the compressible Navier-Stokes equations possibly for the first time. Within the considered range of parameters of the plasma model which is justified for the modeling of surface nanosecond pulsed discharge at atmospheric pressure, our coupled method is able to provide satisfactory prediction of the shock structure generated by the actuator for comparison with experiment, not only in the qualitative shock wave shape but also in quantitative shock front displacement. We provide a comprehensive analysis of the gas heating, shock wave initiation and evolution processes. For example, the characteristic time of the rapid localized heating responsible for shock wave generation, which is yet to be quantified experimentally, is found to be ∼350 ns. We conduct a parametric investigation by varying the peak voltage from 10 kV to 50 kV and rise time from 5 ns to 150 ns. The pressure wave whose behavior is found to be dominated by input voltage amplitude, introduces highly transient, localized disturbance to the quiescent air. In addition, the vortex induced by the shock passage is relatively weak. The interplay of the induced flows by a few successive plasma discharges operating at continuous mode does not appear to be significant, especially at low voltage amplitude.
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