A novel microwave absorbing material with Ti3C2MXene nanosheets.

The microwave dielectric behavior of sandwich-like Ti3C2 MXene nanosheets with efficient microwave absorption was investigated by a combination of experiments and simulations. The obvious frequency dispersion effect and the double-peaked feature of dielectric spectra in Ti3C2 MXene nanosheets could be observed over the frequency range of 2–18 GHz, giving rise to superior microwave attenuation capability. Furthermore, a revised Drude-Lorentz model was proposed to explain the peaked feature of permittivity, and simulated results were demonstrated to agree well with the experimental measurements. It was concluded that the hopping migration between Ti3C2 MXene nanosheets with longer relaxation time than “micro-dipole” relaxation within nanosheets makes a superior contribution to overall absorbing performance.

Ni-modification of Ti3C2MXene enables enhanced microwave absorption ability.

Two dimensional materials have been widely identified as promising microwave absorbers, owing to their large surface area and abundant interfaces. Here, a novel laminated and magnetic composite derived from Mxene was designed and successfully synthesized via facile hydrothermal oxidization of nickel ion intercalated Ti 3 C 2 . Highly disordered carbon sheets were obtained by low temperature hydrothermal oxidization, and the in-situ produced TiO 2 and NiO nanoparticles embedded closely between them. This layered hybrid exhibits excellent microwave absorbing performance with an effective absorbing bandwidth as high as 11.1 GHz (6.9–18 GHz) and 9 GHz (9–18 GHz) when the thickness is 3 and 2 mm, respectively. Besides the high dielectric loss, magnetic loss and ohmic loss of the composite, the amorphous nature of obtained carbon sheets and multi-reflections between them are believed to play a decisive role in achieving such superior microwave absorbing performance.

Multi-functional carbon fiber (CF) based composites have great potential as new-type microwave absorption materials (MAMs). However, it was still a huge challenge to integrate antioxidation and MA properties into CF based composites. Herein, the SiOC ceramics coating modified carbon fibers (SiOC/ CFs) were prepared by a polymer precursor pyrolysis method. The X-ray photoelectron spectroscopy (XPS) revealed that the SiOC coating was composed of SiOC, SiO 2 , and amorphous carbon phases. The SiOC ceramics as dual-functional coating not only heightened the oxidation temperature from 415 C to 890 C, but also highly improved the microwave absorbing ability from À12.60 dB to À47.50 dB. The enhanced MA performance could be attributed to multiple reflections in the cross-linked structure, various polarization relaxation processes, and the favorable impedance matching effect. The SiOC ceramics coating as a semiconductor could suppress the skin effect originating from the cross-linked CF network, thus leading to a favorable impedance matching behavior. Fig. 1 (a) The schematic representation of the preparation route of SiOC/CFs. The SEM images of (b) PAN fibers, (c) PAN-derived CFs, and SiOC/ CFs at different magnification of (d) Â1.5k and (e) Â5.0k.30686 | RSC Adv., 2019,9,[30685][30686][30687][30688][30689][30690][30691][30692] This journal is Fig. 4 The three-dimensional microwave RL curves of (a) SiOC/CFs composites and (b) CFs in the frequency range of 2-18 GHz, (c) the optimal RL values at different layer thicknesses, and (d) the comparison of MA performance of Si-based CFs composites.This journal is

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Lithium-sulfur (Li-S) batteries have attracted more and more attention because they represent one of the most promising candidates to satisfy emerging energy storage demands. The biggest challenge regarding the application of the Li-S battery is to suppress the polysulfide shuttle while maintaining a high sulfur loading mass. Here, a dual polysulfide confinement strategy is designed by confinement of sulfur in polydopamine-coated MXene nanosheets (denoted as S@Mxe@PDA) that performs as a high-performance cathode for Li-S cells owing to their inherently high underlying metallic conductivity and chemical bonding and strong chemical adsorption to lithium polysulfides (LPs). This dual LPs confinement strategy is supported by the results of density functional theory calculations. It is demonstrated that the S@Mxe@PDA cathode exhibits outstanding electrochemical properties, including high reversible capacity (1044 mAh g after 150 cycles at 0.2 C), superior rate capability (624 mAh g at 6 C) and excellent cycling stability (556 mAh g after 330 cycles at 0.5 C with 4.4 mg cm sulfur loading). This work offers a facile and effective method for boosting Li-S batteries into practical applications.

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