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A novel Al@reduced graphene oxide (Al@RGO) composite was designed and synthesized by a one-step hydrothermal method. We investigated the effect of the graphene on the microwave absorbing properties and infrared emissivity of composites. The crystal structure, microscopic morphology, infrared emissivity and electromagnetic parameters of the prepared samples were characterized by XRD, FESEM, TEM, XPS, dual band infrared emissometer and vector network analyzer. TEM and SEM show that the thin Al sheet is uniformly wrapped by RGO with a crumpled surface. Functionalized RGO and surface cation-modified Al sheets are tightly compounded through an electrostatic interaction. The oxygen content and defect from RGO as polarization center endows the material with enhanced molecular polarization and dipole polarization effect. The Al sheet is well coated with RGO, enhancing interface polarization and impedance matching. The minimum reflection loss (RL) of optimized Al@RGO composites is − 46.11 dB at 13.68 GHz under the coating thickness of only 2 mm. The bandwidth below − 10 dB can reach 4.88 GHz (11.52–16.4 GHz). Al sheet is a suitable base material for both microwave absorption and infrared stealth. The Al@RGO composites exhibit excellent infrared stealth ability, and their lowest infrared emissivity is 0.62. Thus, Al@RGO composites show potential application for both electromagnetic wave absorption and infrared stealth. [ABSTRACT FROM AUTHOR]

In this work, Al@MWCNTs (multi-walled carbon nanotubes) composites were prepared by a one-step hydrothermal method. The effects of the morphology and mass ratio of Al@MWCNTs on microwave absorption were studied. The Al@MWCNTs were also found to participate in infrared emissivity. A large number of MWCNTs were interconnected and interspersed between Al sheets, forming a conductive network. As the mass ratio of MWCNTs in the composite was increased, the microwave absorption performance became stronger, and the infrared emissivity remained excellent. When the mass ratio of MWCNTs:Al was 3:20, the minimum reflection loss of the composite at 10.88 GHz was − 39.24 dB, and the effective absorption bandwidth below − 10 dB were 3.04 GHz (9.2–12.24 GHz), the matching thickness was 2 mm, and the infrared emissivity was only 0.67. In this paper, Al powder, a composite material with low infrared emissivity, was creatively used to achieve the superior material bifunctional absorption of MWCNTs, providing a novel and effective way to design other excellent bifunctional materials in the future. [ABSTRACT FROM AUTHOR]

In this study microwave-assisted reduction (MrGO) and direct reduction of graphene oxide (rGO) by Ti powders were established, and the effect of the reaction conditions on the reduction were discussed. The results showed that GO can be effectively reduced by both methods, however, microwave assistance can greatly shorten the reduction time. The produced Ti ions from the reaction of Ti powder with GO were transferred to TiO 2 by hydrolysis and formed MrGO/TiO 2 and rGO/TiO 2 . They were used as adsorbents for the removal of methylene blue (MB). MrGO/TiO 2 showed a higher adsorption capacity ( q max , 845.6 mg/g) than rGO/TiO 2 ( q max , 467.6 mg/g). Investigation on the adsorption MB onto MrGO/TiO 2 was conducted and demonstrated that adsorption kinetics followed the pseudo second-order kinetics model and the adsorption isotherm was well described by the Langmuir isotherm model. The recycling of MrGO/TiO 2 was achieved by photocatalytic degradation of MB catalyzed by MrGO/TiO 2 itself. [ABSTRACT FROM AUTHOR]

Highlights: [•] Plasmonic Ag@AgBr was intercalated in the layered space of K4Nb6O17. [•] Ag@AgBr greatly increased visible light absorption for K4Nb6O17. [•] The plasmonic photocatalysts exhibited enhanced activity for the degradation of RhB. [ABSTRACT FROM AUTHOR]

Abstract: The effects of CaSiO3 addition on the sintering behavior and microwave dielectric properties of Al2O3 ceramics have been investigated. The addition of CaSiO3 into Al2O3 ceramics resulted in the emergence of Ca2Al2SiO7 and CaAl2Si2O8, which acting as liquid sintering aids can effectively lower the sintering temperature of Al2O3 ceramic. The Q × f value of Al2O3–CaSiO3 ceramics decreased with the CaSiO3 addition increasing because of the lower Q × f value of Ca2Al2SiO7 and CaAl2Si2O8. Compared with the pure CaSiO3 ceramic, the Al2O3–CaSiO3 ceramic with 20wt% CaSiO3 addition possessed good dielectric properties of ɛ r =9.36 and Q × f =13,678GHz at the similar sintering temperature. [Copyright &y& Elsevier]

The synthesis of diacetals from pentaerythritol with aldehydes and ketones is carried out under microwave irradiation in 80–98% yields with silica sulfate as catalyst. [ABSTRACT FROM AUTHOR]

Interface constitutes a significant volume fraction in nanocomposites, and it requires the ability to tune and tailor interfaces to tap the full potential of nanocomposites. However, the development and optimization of nanocomposites is currently restricted by the limited exploration and utilization of interfaces at different length scales. In this research, we have designed and introduced a relatively large-scale vertical interphase into carbon nanocomposites, in which the dielectric response and dispersion features in microwave frequency range are successfully adjusted. A remarkable relaxation process has been observed in vertical-interphase nanocomposites, showing sensitivity to both filler loading and the discrepancy in polarization ability across the interphase. Together with our analyses on dielectric spectra and the relaxation process, it is suggested that the intrinsic effect of vertical interphase lies in its ability to constrain and localize heterogeneous charges under external fields. Following this logic, systematic research is presented in this article affording to realize tunable frequency-dependent dielectric functionality by means of vertical interphase engineering. Overall, this study provides a novel method to utilize interfacial effects rationally. The research approach demonstrated here has great potential in developing microwave dielectric nanocomposites and devices with targeted or unique performance such as tunable broadband absorbers. Image 1 [ABSTRACT FROM AUTHOR]

• Ca-alginate/nano-Fe 3 O 4 composite capsules encapsulating sunflower oil were synthesized. • Capsules within asphalt mixtures could release encapsulated oil after the action of microwave. • Oil release rate increased with the increase of microwave irradiation time and nano-Fe 3 O 4 content. • The asphalt mixtures with Ca-alginate/nano-Fe 3 O 4 capsules showed superior healing level. The responsive calcium alginate/nano-Fe 3 O 4 (CA@Fe 3 O 4) capsules can actively release the inner rejuvenator via the stimulation of microwave, thus being a prospective preventive maintenance method for effectively enhancing the self-healing level of asphalt concrete. In view of this, this paper investigated the self-healing property of asphalt mixture containing CA@Fe 3 O 4 composite capsules under the action of microwave. The CA@Fe 3 O 4 capsules encapsulating asphalt rejuvenator were fabricated based on reaction principle of ion exchange. Several tests were conducted to characterize the morphological structure, thermal stability, mechanical resistance and relative healing agent content of the capsules. Meanwhile, the spatial distribution and rejuvenator release from the capsules in asphalt mixtures after mixing and compaction process were also explored. Besides, the surface temperature distribution and self-healing capacity of asphalt concrete beams without and with capsules were investigated after microwave action. Meanwhile, the rejuvenator release ratios of capsules within mixture beams were also quantificationally analyzed. The experimental results indicated that the CA@2%Fe 3 O 4 capsules showed multi-cavity structure with healing agent stored inside. Meanwhile, the mechanical resistance and thermal stability of the capsules all were up to the manufacturing requirements of asphalt mixtures in laboratory. The asphalt mixtures with CA@2%Fe 3 O 4 capsules showed superior healing level under the action of microwave due to the combined effect of thermal induction and rejuvenator healing. In short, the CA@2%Fe 3 O 4 capsules can obviously enhance the self-healing capacity of asphalt mixture compared with normal CA capsules. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biomass-based N-doped carbon aerogels were designed for microwave absorption (MA). • Superior absorption (-68.8 dB) outperforms other biomass-derived carbon absorbers. • Impedance matching and high attenuation with appropriate dielectric properties. • Synergistic effect of hierarchically optimized structures and inherent N-doping. • Fully taps the potential of microstructure regulation for MA optimization. Remarkable features of lightweight and 3D conductive network make carbon aerogels a competitive candidate for advanced microwave absorption (MA) materials. However, little is known about the specific correlation between multiscale structural parameters and their MA properties, setting obstacles for fully tapping the potential of microstructure regulation. Herein, utilizing sustainable biomass as the precursor, chitosan-derived N-doped carbon aerogels (CCA) with finely-tailored hierarchical structure were fabricated via regulating the freeze casting and annealing processes. Carbonization temperature mainly controlled nanoscale structural features such as defects and nanocrystals which had a significant impact on conductive and polarization losses. As for micron/macro-scale structures, the pore size and 3D conductive network configuration contributed to interfacial polarization and conductive losses, which were regulated by freezing process and precursor concentration. The synergistic effect derived from the hierarchical optimized structure and inherent N-doping was responsible for a remarkable reflection loss of − 68.8 dB, and an effective absorption band covering the whole X-band at 5.1 mm. Such MA performance significantly outperforms other biomass-derived carbon absorbers that usually incorporate magnetic components. The multi-scale structural control implemented in this work is essential to fully exploit the potential of chitosan-derived carbon aerogels across different length scales and design high-performance microwave absorbers. [ABSTRACT FROM AUTHOR]