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Urgent demands to reduce the harmful electromagnetic radiation and improve weapons survivability made it necessary to develop high-efficiency microwave absorption materials, especially those operating in frequency range of 2–12 GHz. In this work, Fe 3 O 4 /Ag composites were synthesized by one-step hydrothermal method. Microwave absorbing performance can be flexibly tuned by varying Fe 3 O 4 /Ag molar ratio from 2:1, 3:1, to 4:1. An increase in Fe 3 O 4 /Ag molar ratio would lead to an enhanced permeability over the frequency region of 4–12 GHz. Meanwhile, real part of permittivity remains almost unchanged whereas the imaginary part drastically decreases, making impedance matching and attenuation capacity increase dramatically. In this way, splendid microwave absorption performance with broad absorption bandwidth within a range of 4.88–9.76 GHz and minimum reflection loss of −63.2 dB could be achieved at composite thickness of 3.6 mm. [ABSTRACT FROM AUTHOR]

To gain broad microwave absorption bandwidth over 2–18 GHz, hard/soft magnetic composites Ba(Zr–Ni) 0.6 Fe 10 · 8 O 19 /Fe 3 O 4 have been synthesized in this work. The results show that the raising heat treatment temperature would cause more Fe 3 O 4 particles attach to Ba(Zr–Ni) 0.6 Fe 10 · 8 O 19 particles, increasing the number of interfaces between Ba(Zr–Ni) 0.6 Fe 10 · 8 O 19 and Fe 3 O 4 to enhance the hard/soft exchange coupling effect. Finally, the sample heat treated at 400 °C possesses the widest magnetic loss range (μ″>0.2) of 12.4 GHz, which contributes to a broad effective absorbing bandwidth of 6.68 GHz at 1.9 mm. The performance is superior than most of the state-of-the-art microwave absorbers. [ABSTRACT FROM AUTHOR]

In this study, to effectively broaden the absorption bandwidth of M-type barium ferrite (BaM) in frequency range 2–18 GHz, Zr4+-Ni2+ ions gradient-substituted BaM samples were synthesized via secondary heating the mixtures of homogeneous-substituted Ba(ZrNi) 0.6 Fe 10.8 O 19 and Ba(ZrNi) 0.7 Fe 10.6 O 19. Effects of primary and secondary heat treatment on electromagnetic (EM) parameters of gradient-substituted BaM were investigated in detail. Permittivity values of samples are mainly controlled by primary heat treatment, enhancing with increasing temperature, whereas magnetic loss range is enlarged by improving primary and secondary heat treatment. As a result, the frequency range with μ" value > 0.3 reaches to 6.84 GHz for the sample "1400–1200 °C". Enhanced dielectric and magnetic losses contribute high attenuation constant over wide frequency range, finally resulting in broad absorption bandwidth of 6.24 GHz at matching thickness of 2.8 mm. The bandwidth improved by 21% and 44% compared to that of original Ba(ZrNi) 0.6 Fe 10.8 O 19 and Ba(ZrNi) 0.7 Fe 10.6 O 19 , respectively. This study sheds new light on the preparation of broadband absorbing materials. [ABSTRACT FROM AUTHOR]

• A novel Ni 1-x Co x micro chains that synthesized through a magnetic field-assisted reduction method. • The particle size in the Ni 1-x Co x micro chains could be modified by changing the composition. • Significantly enhanced electromagnetic wave absorption performance was obtained by establishing the chain structure. Transition metal magnetic alloys have garnered extensive interests in electromagnetic wave absorption due to the remarkable magnetic loss capacity and unique magnetism-frequency characteristics. Herein, we report a novel magnetic absorbent of Ni 1-x Co x micro chains that synthesized through a magnetic field-assisted reduction method. The precipitated Ni 1-x Co x particles could be connected and aligned during the magnetic reduction process. Due to the modified electronic structure of the Co active site by Ni, the particle size in the Ni 1-x Co x micro chains noticeably increases with increased x. Meanwhile, the complex dielectric constants exhibit a decreasing trend, which contributes to the improved impedance matching and higher resonance frequencies. The connected Ni 1-x Co x micro/nano particles not only benefit to the conductive loss, but also strengthened the polarization loss on the contacted interfaces among the particles. As a result, significantly enhanced electromagnetic wave absorption performance was obtained with the minimum reflection loss of −21.0 dB and the effective absorption bandwidth of 3.92 GHz at a thickness of only 1.35 mm. Overall, this work has demonstrated the strategy of designing aligned bimetallic absorbent, possessing great potentials in improving their microwave absorption properties. [ABSTRACT FROM AUTHOR]

• The Fe/Co oxide@α-Fe core–shell composites were prepared. • The phase, morphology and electromagnetic parameters were effectively manipulated via the shell design. • The minimum reflection loss of −51.3 dB and effective absorption bandwidth of 5.31 GHz were obtained at only 2.1 mm. • The corrosion current density was significantly suppressed from 50.12 μA⋅cm−2 to 0.99 μA⋅cm−2 by introducing the functional Fe/Co oxide layer. Soft magnetic alloys have garnered formidable interests as microwave absorbents for the potent magnetic losses. But the application is hindered by the simplex attenuation behavior and the susceptibility to marine corrosion. In this work, the multiphasic oxide shells were designed and introduced onto the metallic α-Fe micro particles. On one hand, the multiple phases provided sufficient heterogeneous interfaces that boosted efficient polarization losses, led to a significant enhancement in the energy dissipation capacity. On the other hand, the dielectric/magnetic composites benefit the improved impedance matching condition and broadened absorption bandwidth was obtained. The result displays impressive microwave absorption performance with minimum reflection loss (RL min) of −51.3 dB in the C band, and effective absorption bandwidth (EAB) of 5.31 GHz. Importantly, the multiphasic oxides layers greatly contribute to the corrosion inhibitions for the metallic particles, where the corrosion current density (I corr) was sharply decreased from 50.12 μA⋅cm−2 for the pure α-Fe metal to 0.99 μA⋅cm−2 for the Fe/Co oxide@α-Fe core–shell composites. Therefore, this work demonstrates a feasible and productive way to modify the traditional metallic absorbents towards both high absorbing property and excellent environmental stability. [ABSTRACT FROM AUTHOR]

Soft magnetic microwave absorbents have merits of sufficient magnetic loss and unique magnetism-frequency response characteristics, yet are limited by the low natural resonance frequencies and simplex loss mechanism. Introducing second phase has been proven to be efficient in evoking structure, magnetism and conductivity changes, but the effects on the microwave absorption is still unbeknown. In this work, the Co 0.72 Fe 0.28 alloy magnetic absorbents with dispersedly distributed NdCo 5 /LaCo 5 nano precipitates were prepared. By fine-tuning the doping ratios of the rare earth (RE) of Nd/La, the coercivity and conductivity show an upward trend with enhanced magnetic and dielectric losses on 2–18 GHz. On one hand, the high magneto-crystalline anisotropic RECo 5 phases uplifted the holistic resonance frequency ranges and enhanced the C/X/Ku band attenuations. On the other hand, the as-spawn vacancies, heterogeneous interfaces and dislocations boosted the conductive/polarization losses of the individual magnetic alloys. As a result, the high-frequency performance was significantly improved when ensuring the impressive low-frequency loss. A remarkable minimum reflection loss (RL min) of −76 dB was achieved in the S band, and the effective absorption bandwidth (EAB) of 7.34 GHz was obtained at only 1.7 mm, covering most of the X/Ku bands. The performance sets it apart as the highest among the reported RE-transitional alloy absorbents so far. Overall, this work provides a feasible way and novel strategy for improving the microwave absorption properties for the traditional metal alloys and their compounds. [Display omitted] [ABSTRACT FROM AUTHOR]

Magnetic materials with highly efficient microwave absorption properties, crucial for dealing with the advanced wireless communications and radar detections, have been garnering significant attentions. Rare-earth transition-metal compounds were researched as the potential candidates but still suffer from the disadvantages of complex powder metallurgy process and low serving frequencies. In this work, the novel magnetic composites consisting of SmCo 5 and Sm 2 Co 17 are developed by a reduction diffusion method. The micromorphology and the binary phase ratios of the SmCo 5 /Sm 2 Co 17 could be easily modulated by simply altering the reactant concentrations. Consequently, an optimum reflection loss of − 50.2 dB and broad absorption bandwidth of 4.95 GHz at a thickness of only 2.0 mm are achieved. The improved microwave absorption properties of the SmCo 5 /Sm 2 Co 17 binary-phase magnetic absorbents can be attributed to their adjustable magnetic phases and the distinctive flaky particle shape, which greatly enhance microwave absorption capabilities. This work demonstrated a feasible reduction diffusion method and proposed a new strategy of designing binary-phase magnetic materials to achieve high microwave absorption properties. • A novel binary-phase Sm-Co composite were first reported by diffusion-reduction method. • Modified flaky microstructures and tunable microwave absorption properties were achieved. • High frequency magnetic loss was enhanced by inducing shape anisotropy. • Minimum RL of − 50.2 dB and EAB of 4.95 GHz were obtained at only 2.0 mm. [ABSTRACT FROM AUTHOR]

In generally, microwave absorption and shielding are a pair of conjugate properties, which merely achieves in the same system of electro-magnetic materials. In this work, Prussian blue analogues (PBA) derived hollow CoNi@C frames embedding with reduced graphene oxide (rGO) are successfully synthesized through a facile self-assembly method. In addition to considerable dielectric loss originating from high conductivity components of C@rGO, magnetic loss is also impressive due to the dynamic magnetic coupling interaction among the closely spaced magnetic units of CoNi. Finally, the CoNi@C@rGO composite with an extremely low loading ratio of 30 wt% reveals a strong reflection loss of − 48 dB and a broad absorption bandwidth of 6.24 GHz concurrently at a thin thickness of 1.6 mm. The launch field is obviously suppressed by covering the CoNi@C@rGO coating and RCS is below − 10 dBm2 within the entire detection angles (−90°