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Titanium dioxide/multi-walled carbon nanotubes (TiO2/MWCNTs) are nanocomposites (NCs) prepared via click reaction of TiO2 nanoparticles (TiO2 NPs) with azide groups (TiO2–N3) on the surface and MWCNTs with alkynyl groups (MWCNTs–ALK) on the surface. The phase structure, graphitization degree, structure, elemental composition, the microstructure of TiO2/MWCNTs NCs were characterized by XRD, Raman, IR, XPS and SEM, and their electromagnetic (EM) parameters were determined by the vector network analyser. For TiO2/MWCNTs NCs with click reaction, the minimum reflection loss (RLmin) is up to −47.87 dB at 12.02 GHz, the matching thickness is 2.0 mm, and the bandwidth is lower than −10 dB in the range of 7.7–12.48 GHz. Compared with the physically mixed TiO2/MWCNTs composites, TiO2/MWCNTs NCs prepared by click reaction show more excellent EM absorption properties, which is mainly due to the binding of covalent bonds between the two kinds of materials that lead to the enhancement of interfacial effects, the improvement of impedance matching and the increase of electron migration. [ABSTRACT FROM AUTHOR]

Hierarchical core–shell architectures with multi-walled carbon nanotubes as core and MnO2 sheets shaped in an array mode as shell (MWCNTs@MnO2) were successfully synthesized via a simple wet chemical method. X-ray diffraction patterns and X-ray photoelectron spectroscopy analysis revealed that the composites were successfully prepared. Morphological characterizations were made by scanning electron microscopy and transmission electron microscopy. Vector network analyzer was employed to investigate the electromagnetic parameters of the composites. A possible attenuation mechanism was discussed, and the high-performance microwave absorption properties were attributed to the porous microstructure, polarization effect, dielectric loss and the synergistic action between MWCNTs and δ -MnO2. A minimum reflection loss (RL) of − 50.6 dB was achieved at a thickness of 1.4 mm, and an effective absorption bandwidth (RL < − 1 0 dB) covered 4.2 GHz (from 13.8 GHz to 18 GHz) at a thickness of 1.3 mm. Therefore, these results suggested that the MWCNTs@ δ -MnO2 composites can be an excellent candidate for microwave absorption materials. The cross-linked δ-MnO2 nanoflakes attached on the sidewalls of MWCNTs and the unique open porous 3D conductive structure of the nanocomposites contributed to the multiple reflections and scattering of microwaves in long propagation periods. Moreover, MWCNTs with high electrical conductivity can generate loss current and energy dissipation by electron migration and hop across the interfaces. [ABSTRACT FROM AUTHOR]

In this work, reduced graphene oxide/CeO2 nanocomposites (RGO/CeO2) with two different RGO contents were synthesized using a facile one-step hydrothermal method, and the microwave absorption properties of RGO/CeO2 were investigated for the first time. Morphology and structure analysis shows that the CeO2 nanoparticles are uniformly dispersed on the RGO sheets with average size of 15nm. The as-prepared RGO/CeO2 exhibits excellent microwave absorbability. An optimal reflection loss (RL) of 32dB is found at 17GHz with a coating layer thickness of 1.5mm. The product with a coating layer thickness of only 2.0mm shows a bandwidth of 4.3GHz, corresponding to RL at 10dB (90% of electromagnetic wave absorption). Compared with pristine RGO or pure CeO2 nanoparticles, the reported nanocomposites achieved both wider and stronger wave absorption in the frequency range of 2-18GHz. The enhanced microwave absorption properties are attributed to the conductive loss and dielectric loss mainly caused by the higher oxygen vacancy concentration of CeO2 in RGO/CeO2, which is demonstrated by X-ray photoelectron spectroscopy. Moreover, multiple interfacial polarizations occurring in the multi-interfaces between CeO2 and RGO sheets may be beneficial to microwave absorption. RGO/CeO2 could be used as an attractive candidate for the new type of microwave absorptive materials. CeO2 well-dispersed nanocrystals, anchored on the reduced graphene oxide hybrid composites, were synthesized by a facile hydrothermal method. Microwave absorption properties measurement shows that the introduction of reduced graphene oxide significantly enhances the microwave absorption intensity of CeO2 nanocomposites, and the bandwidth of reflection loss is also broadened. The concentration of oxygen vacancy defects plays a key role in the enhanced microwave absorption properties. [ABSTRACT FROM AUTHOR]

In this work, Ni-doped ZnO/Al composites were prepared by a facile chemical co-precipitation method. The morphology and structure of the as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), respectively. It was found that the flake-like Al powders were successfully coated by Ni-doped ZnO nanoparticles with slight aggregation and Ni was successfully doped into the crystal lattice of ZnO. Moreover, the effects of ZnO concentration and doped Ni concentration on the infrared emissivity of ZnO/Al composites at the waveband range of 8-14m were studied. The results showed that the ZnO/Al composites exhibited the lowest infrared emissivity of 0.34 with 50wt.% ZnO concentration. Meanwhile, the electromagnetic parameters and microwave absorbing properties of Ni-doped ZnO/Al composites in the frequency range of 2-18GHz were explored. Significantly, 12mol.% Ni-doped ZnO/Al composites presented the lowest infrared emissivity of 0.37 and the maximum reflection loss reached 32.5dB at 13.6GHz with a thickness of 4.5mm. The excellent microwave absorbing properties could be attributed to the good impedance match, crystal lattice defects and interfacial polarization. It was believed that the Ni-doped ZnO/Al composites could be used as potential infrared-microwave compatible stealth materials. Ni-doped ZnO/Al composites with infrared-microwave compatible stealth performance were prepared by a facile chemical co-precipitation method, which had the lowest infrared emissivity of 0.37 and the maximum reflection loss reached -32.5dB at 13.6GHz with a thickness of 4.5mm at 12mol.% doped Ni concentration. [ABSTRACT FROM AUTHOR]

The core-shell structure H-MnO 2 @PANI own excellent impedance matching characteristics (Figure b), and exist abundant interfaces that can produce strong interface polarization and enhance the loss of electromagnetic waves (Figure a), the minimum reflection loss is −52.06 dB (Figure b). The PANI bridge connects MnO 2 as a whole (Figure c), resulting in conductance loss dissipates electromagnetic waves and increases the effective absorption bandwidth to 4.56 GHz (Figure d). • The multi-interface structure MnO 2 @PANI is prepared by a mild self-template method. The surface modification enhanced the affinity of MnO 2 to AN, which made it possible to obtain the core-shell structure of MnO 2 @PANI successfully. • A series of MnO 2 -based products with multi-interface structure are obtained by simple self-template oxidation-etching strategy. The multi-interface structure is conducive to enhance the attenuation loss of polarization effect on electromagnetic wave. • RL min of H-MnO 2 @PANI is −52.06 dB at 8.48 GHz, and it has a broadband absorption of 4.56 GHz. Its excellent microwave absorption performance is attributed to the synergistic effect of conductivity loss, interface polarization and multiple reflection loss. Nowadays, high-frequency electromagnetic pollution makes the lightweight and high-efficiency absorption materials become the research hotspot. In this paper, the hollow structure MnO 2 @PANI microsphere composite was reasonably synthesized by self-template strategy and in-situ polymerization. Coating conductive polyaniline (PANI) on the modified surfaces of MnO 2 microsphere not only can improve the impedance matching and microwave absorption ability, but also solve the drawback of low loss intensity as well as narrow absorption band of pure MnO 2. The conductive polymer PANI conductance loss, MnO 2 -PANI multiple interfacial polarization and multiple reflection loss synergy endows hollow MnO 2 @PANI microsphere excellent microwave absorption performance. The RL min of hollow MnO 2 @PANI microsphere is −52.06 dB at 8.48 GHz and has a wide absorption of 4.56 GHz. Those positive results show that the pure dielectric MnO 2 @PANI microsphere material with a multi-interface hollow core-shell structure prepared from a template is a lightweight and efficient absorbent. [ABSTRACT FROM AUTHOR]

Three Ni/C composites with different morphologies were prepared by changing nickel salt using a hydrothermal method and high-temperature pyrolysis. Results show that material defects, nitrogen doping, heterointerface, conductive network, and magnetic effect optimize impedance matching, resulting in the synergistic effect of conductivity loss, polarization loss, multiple scattering, and magnetic loss. The reflection loss of the sample prepared using nickel nitrate is − 44.2 dB at 11.84 GHz and 2.4 mm thickness, and the effective absorption bandwidth is 5.2 GHz. In addition, radar cross section simulation demonstrates the excellent performance of the material in practical applications. Thus, the sample prepared using nickel nitrate is a candidate material for radar stealth and electromagnetic wave absorption. [Display omitted] • Preparation of Ni/C composites with different morphology by controlling nickel source. • The synergistic effect of dielectric loss and magnetic loss optimizes impedance matching. • The RL min achieved − 44.2 dB and EABmax was 5.84 GHz. • The RCS contribution of Ni/C composites in far field is simulated by CST. [ABSTRACT FROM AUTHOR]

Sheet aluminum powder was used as the substrate and aniline as the polymer monomer, to design novel Al/PANI composites via in-situ polymerization, which exhibited high electromagnetic wave absorption properties and low infrared emissivity. These unique bifunctional composite were systematically characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, IR-2 dual-band emission rate measuring instrument and vector network analyzer. The calculated results showed that the maximum reflection loss value of Al/PANI composite reached −46.09 dB at 14.56 GHz with a film thickness of only 1.0 mm. Meanwhile, the infrared emission rate of the composite was 0.55. The excellent electromagnetic absorption performance may be ascribed to its superior conductivity and unique structure. The merits of as-synthesized composites with high-performance microwave absorbing properties and low infrared emissivity indicate the potential use of Al/PANI composites in the applicable stealth fields. • Al/PANI composites have both microwave absorption performance and low infrared emissivity ability. • Al/PANI composites were prepared by a facile in-situ polymerization method. • The microwave absorption performance and infrared emissivity of the composites can be adjusted by the amount of polyaniline. • The minimum reflection loss of Al/PANI composite achieve −46.09 dB at 14.56 GHz. • The lowest infrared emissivity of Al/PANI composite can reach up to 0.55. [ABSTRACT FROM AUTHOR]