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When the thickness of the wave-absorbing material is low, there exists the problem of the narrow wave-absorbing frequency band, making it difficult to regulate the position of the wave-absorbing peak. In this study, FeNi@SrFe-MOF composite powders were synthesized using a hydrothermal method and a liquid-phase reduction method. The composite powder was spherical, with a particle size of about 50 μm–60 μm; the core layers of the powders were porous SrFe-MOF powders with permanent magnetization, and the outer layers were FeNi alloy nano-powder coatings with a particle size of 100 nm–120 nm, which took into account both the soft magnetization and the permanent magnetization properties of the composite powders. Additionally, a directional magnetic field was applied to the powder coating. By regulating the intensity and direction of the magnetic field, the electromagnetic parameters of the composite powder coating underwent sensitive changes, allowing for the precise regulation of the electromagnetic wave absorption performance of the composite powders. With the increase in magnetic field intensity, the ε′ value decreased significantly. The ε′ values were 8.56–7.35 for H453mT and 6.73–6.12 for H472mT. When no magnetic field was applied, the Snoke limit frequency of the μ′ value was 6.0 GHz. When the magnetic field intensity increased, the Snoke limit frequency of the μ′ value increased from 6.0 GHz, without the magnetic field, to 8.3 GHz; the Snoke limit of the composite powders was shattered. After the H453mT magnetic field regulation treatment, the powder coating exhibited good impedance matching characteristics with air. When the magnetic field intensity was 453mT and the thickness of the composite powders coating was 3.5 mm, the composite powders coating showed the strongest absorption peak when the R-value was −59 dB at 7.8 GHz, and the effective absorption bandwidth reached 3.2 GHz, exhibiting superb absorbent qualities. The wave absorption property of the coating can be sensitively changed by the magnetic field regulation treatment at the condition without changing the powder structure or coating structure, which provides a new strategy for the regulation of the wave absorption property and has broad application prospects. [ABSTRACT FROM AUTHOR]

Nano zero‐valent iron (nZVI) is an effective material for dye wastewater treatment, but excessive agglomeration and oxidation greatly limit its application. Herein, graphene (GR) supported FeNi bimetallic nanoparticles (FeNi@GR) are prepared by alloying and carrier supported dispersion for efficient removal of azo dyes from water. Not only can it effectively solve the problem of excessive agglomeration and oxidation of nZVI, but also the synergistic effect of bimetallic coordination formation and the excellent electron transfer ability of graphene are beneficial to enhance the reactivity of FeNi@GR. The optimal FeNi@GR is prepared by adjusting the content of GR and the removal of Congo red (CR) by FeNi@GR‐10% reached 625 mg g−1 within 150 min at pH = 7.0. Higher temperature and lower pH favor the removal of CR azo dye. The action mechanisms of FeNi@GR presumably involve the transfer of active hydrogen atoms and the transfer of electrons generated by Fe0 and Ni0. Besides, the saturation magnetization (Ms) of FeNi@GR is 68.15 emu g−1, which has excellent magnetic response performance. This work not only provides a simple and efficient method to stabilize nZVI, but also reveals that using FeNi@GR is a promising approach for the remediation of water pollution. [ABSTRACT FROM AUTHOR]