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Rational design on microstructure of magnetic material provides new opportunity to enhance the electromagnetic absorption performance. Herein, we demonstrate the successful preparation of spindle-cone of Fe/Fe2O3 and Fe3O4 samples with an average size of ∼1.2 μm, using a facile two-steps method. The well-defined spindle-cone shaped α-Fe2O3 was developed first by a solvothermal route and then reduced by H2 or NaBH4, respectively. The morphologies, phase compositions and magnetization of these as-prepared samples are analyzed by Field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and X-ray photoelectron spectrum (XPS) and vibrating sample magnetometer (VSM). Meanwhile, the electromagnetic (EM) absorption performance of Fe/Fe2O3 and Fe3O4 spindle-cones-paraffin composites with various filling ratios are also studied. The results reveal that Fe/Fe2O3 with a filling ratio of 50 wt% achieves the smallest reflection loss value of −26.2 dB at a thickness of 1.4 mm. At thinner thickness (1.0 mm), the bandwidth (RL

Based on the EM wave absorption principle, superior absorbers should have the characteristics of strong attenuation constant and suitable impedance matching. In this work, a novel hierarchical composite consisting of Fe-Co nanoparticles embedded in porous carbon decorated with graphene (Fe-Co/NPC/RGO) was synthesized by a simple hydrothermal route using a Co metal organic framework (MOF) followed by calcination process. The microstructure, composition, magnetic properties and microwave absorption performances of as-synthesized samples were characterized and discussed. Compared with Fe-Co/NPC, the Fe-Co/NPC/RGO composite possessed high attenuation constant, excellent impedance matching and synergistic effect, which resulted in significant improvement in its microwave absorption properties. The optimal reflection loss (RL) was −52.9 dB at 10.1 GHz for a thickness of 2.5 mm, and the corresponding absorption bandwidth (RL

Transition metal oxides/hydroxides materials attract much attention in the field of energy storage materials because of their high theoretical specific capacity and low cost. However, it is normally difficult to improve the capacitance of the electrode by simply increasing the mass loading or thickness of the electrode. To raise the utilizing efficiency of the active material, hierarchical integrated electrodes assembled by NiCo hydroxide nanowires arrays and reduced graphene oxide interlayers are well designed and synthesized. The surface morphology and inner structure of the hierarchical electrode are characterized by SEM. The electrochemical performances of the electrodes are evaluated by three-electrode and two-electrode system in 2 M KOH respectively. Assisted with two reduced graphene oxide interlayers, NiCo hydroxide nanowires arrays exhibit a specific capacity of 2.41 C cm−2 at 1 mA cm−2. Even at a high current density of 50 mA cm−2, nearly 47% of the capacity could still remain. The results show that, the multi-level nanowires arrays structure provides multi-dimensional transmission path for ions and electrons, and achieved higher specific capacities and rate properties.

Two-dimension (2D) nanomaterials with high specific area, low density and special electric behavior have attracted tremendous interest in the field of electromagnetic wave (EMW) absorption. Continuous and growing efforts have been committed to satisfy the demands of good impedance matching and strong attenuation capacity of 2D-based EMW absorption nanomaterials in past several years, and the ultimate aim of these materials is to develop potential candidates of high-performance absorption materials. In this review, we will summarize the latest progress (in the last four years) of 2D nanomaterials for EMW absorption, including graphene, MXenes, MoS2 nanosheets, layered double hydroxides (LDHs), graphite-like C3N4 (g-C3N4), and other representative transition metal dichalcogenides (TMDs). Moreover, the synthesis methods, structures, absorption mechanisms and performances of some excellent achievements will be presented. The aim of this review is to provide readers with a systematic overview of the relationship between 2D structures and absorption properties, and guide the future design of novel 2D electromagnetic wave absorption materials (EWAMs) by discussing the impedance matching and attenuation capacity of these recent advances. This review also intends to prompt fresh concepts for designing prominent high-performances EWAMs.

Efficient microwave absorption (MA) materials have drawn wide attention due to the harm for humans and electronic equipment from electromagnetic pollution. In this work, the porous hexagonal flaky Co@C core-shell composites were designed and fabricated via a facile process. The microstructure, composition, magnetic performance and MA performance of samples were characterized and discussed. The optimal reflection loss (RL) of sample loaded with Co@C core-shell composites could reach −53.8 dB (9.46 GHz) at the thickness of 2.2 mm, and the corresponding effective absorption bandwidth (EAB, RL

Complex metal oxide hollow structures are mostly prepared by hard template-based multistep procedures. It is still desirable yet challenging to develop new efficient strategies to fabricate high-quality complex metal oxide hollow structures. Herein, uniform multi-shelled NiO hollow spheres were synthesized; especially quintuple-shelled NiO hollow spheres were synthesized for the first time by a simple shell-by-shell self-assembly capable of controlling the shell numbers, which are achieved by controlling the heat treatment. The research makes a significant contribution to the synthetic methodology of multi-shelled hollow structures and opens up new opportunities for deeper understanding formation mechanism of the shell-by-shell self-assembly. The obtained quadruple/quintuple-shelled NiO hollow spheres show promising electrochemical performance in anodic lithium storage for Li-ion battery.

One-dimensional (1D) microwave absorbers have attracted wide attention in the field of microwave absorption (MA) because of the significant anisotropy and great dielectric attenuation of 1D architecture. In this work, the novel 1D flower-like yolk-shell Fe3O4@SiO2@NiO (FSN) nanochains have been fabricated through a modified Stober and a simple hydrothermal method. The unique 1D flower-like yolk-shell architectures have large surfaces, multiple interfaces and void spaces. Benefitting from these advantages, the FSN nanochains showed excellent MA properties. Compared with the sample loaded with 10 wt% 1D flower-like yolk-shell FSN nanochains, the sample loaded with 30 wt% showed strong MA performance with a minimum reflection loss (RL) value of −54.28 dB (12.9 GHz) and an effective absorption bandwidth of 4.0 GHz (11.05–15.05 GHz) at the thickness of 2.54 mm. The 1D flower-like yolk-shell FSN nanochains with strong absorption, broad absorption bandwidth and thin layers, provided a new method for fabricating 1D MA materials and will become the promising candidates in the practical MA fields.

The development of new absorbing materials that meet the requirements of “thin, light, wide and strong” become a challenge for efficient electromagnetic wave absorbing materials, it is also attracting more and more people to develop in this direction. In this work, the mutual stacking process of nanosheets was achieved through a simple solvothermal reaction. After annealing, a flower-like ZnCo2O4 material was obtained. ZnCo2O4 has excellent electromagnetic wave absorption performance due to the special structure of the nanometer plates stacked on each other. Especially, ZnCo2O4-350 has a minimum RL value of −43.61 dB in the matching thickness of 2.4 mm, while the effective absorption bandwidth was 7.12 GHz covering from 10.88 to 18.0 GHz in 2.8 mm. The excellent absorption performance of electromagnetic wave is related to the conductivity loss, multiple reflection and scattering caused by the special morphology. The research may provide new ideas for the development and design of new electromagnetic wave absorbing materials.

Core-shell structured γ -Fe 2 O 3 @C nanorod-carbon sphere composites have been synthesized via a facile hydrothermal method employing FeCl 3 ·6H 2 O as the iron source and d -glucose as the carbon source. The core–shell structured γ -Fe 2 O 3 @C nanorods possess a uniform size with ∼500–800 nm in length, the carbon shell's thickness is ∼3–10 nm, and the γ -Fe 2 O 3 core is homogeneously coated by amorphous carbon layer. The measured electromagnetic (EM) parameters show that its maximum reflection loss (RL) can reach −8.11 dB at 3.92 GHz. This is mainly attributed to the multiple-interfacial polarization among the core–shell structured γ -Fe 2 O 3 @C nanorod-carbon sphere composites. The core–shell structured γ -Fe 2 O 3 @C nanorod-carbon sphere composites can be a promising candidate for lightweight microwave materials.

Yolk-shell magnetic Fe3O4/P(MAA-MBAA)-PPy/Au/void/TiO2 microspheres have been prepared as visible light active photocatalyst. In this structure, the Fe3O4/P(MAA-MBAA)-PPy core-shell support provides magnetic properties for the catalyst and a large number of binding sites for the Au nanoparticles. In addition, coupling TiO2 with Au nanoparticles can extend the range of absorbable sunlight and enhance electron hole separation. The test of degrading rhodamine B (RhB) under simulated visible light was used to verify the photocatalytic activity of the photocatalyst. The results showed that the photocatalyst exhibited favorable catalytic properties within 90 min in the case of using 4 mg itself. The improved performances were ascribed to the unique yolk-shell structure, which on the one hand greatly improves the light utilization, on the other hand favors full contact of the dye because of the porous appearance of the outer shell. Furthermore, the existence of magnetic core was beneficial to the recycling of the photocatalyst. And the recycling results demonstrated that the catalyst efficiency was maintained at 70.2% even after six recycling experiments. This work not only displays a new material for the degradation of organic dyes, but also provides a new approach for the synthesis of yolk-shell structure photocatalysts.