The rational integration of dielectric components is a promising approach to optimize the Maxwell–Wagner–Sillars effect (MWSE) for developing lightweight and highly efficient electromagnetic wave (EMW) absorbers. However, the controllable modulation of the dielectric polarization relaxation response remains a great challenge, and impedes the further improvement of the absorption properties. Herein, an inside-out Ostwald ripening and phase-evolution strategy is proposed for the preparation of uniform-sized hollow N-doped carbon microspheres with embedded Ni/Ni2P heterojunctions (Ni/Ni2P/CNs). The resulting Ni/Ni2P/CNs microspheres well-integrated the Ni/Ni2P heterojunctions with a hollow carbon skeleton to optimize the impedance matching and the MWSE, thus reinforcing the dielectric polarization relaxation response. Consequently, the fabricated Ni/Ni2P/CNs exhibited superior EMW-absorption performances with a minimum reflection loss of −72.2 dB at a thin matched thickness of 1.7 mm and the absorption bandwidth reached 5.8 GHz. Such remarkable performances exceed most of the previously reported absorbers with a hollow structure. The experimental results and simulation analysis demonstrated that the Ni/Ni2P/CNs microspheres possessed large interior voids, well-defined heterojunctions, and enlarged electron-redistribution regions, which are crucial contributions to optimize the MWSE and strengthen dielectric polarization. This study presents a novel avenue for the controllable design of MWSE-strengthened absorbers and provides a feasible method to reinforce dielectric polarization with balanced conduction loss and polarization loss.
MXenes are attracting great interest for their excellent electrical and mechanical properties . High dielectric constants have been achieved in polymer-based nanocomposites with MXenes as fillers, but these materials suffer from large dielectric losses. In this work, Ti 3 C 2 T x MXene/silicone rubber (SR) nanocomposites were prepared because of the low dielectric loss of SR. The effects of Ti 3 C 2 T x MXene nanosheets on the thermal stability, dielectric and mechanical performance of the nanocomposites were investigated. A dielectric constant of 6.2 accompanied by an extremely low dielectric loss of 0.001 at 10 3 Hz frequency was obtained in the nanocomposites when 1.2 wt% Ti 3 C 2 T x MXene was loaded. The enhanced dielectric properties are mainly attributed to the Maxwell-Wagner-Sillars effect and the microcapacitor model. Moreover, the thermal stability of the nanocomposites can reach 450 °C. Tensile strength of 430 kPa, elongation at break of 341% and reduced elastic module of 402 kPa were also obtained in the nanocomposite with 2 wt% Ti 3 C 2 T x MXene. This work provides a method for fabricating polymer-based nanocomposites with excellent dielectric properties under low filling content, which is crucial for modern electronic applications.
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