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Binary alloys; Electromagnetic shielding; Ferromagnetism; II-VI semiconductors; Iron alloys; Magnetic properties; Magnetic semiconductors; Nanomagnetics; Precipitation (chemical); Saturation magnetization; Semiconducting zinc compounds; Synthesis (chemical); Wide band gap semiconductors; Zinc alloys; ZnO nanoparticles, Feni/ZnO nanoparticle composite; High microwave; In-situ precipitation; Microwave absorption; Optimum thickness; Precipitation synthesis; Property; Reflection loss; ZnO; ZnO nanoparticles, Microwaves
Abstract:
Novel synthetic methods and materials tuned for high-efficiency absorbers are increasingly being used for shielding environments from microwaves with frequencies of gigahertz range emitted from cell phones and radar systems. Here, an in situ precipitation route in the synthesis of nanocomposites consisting of magnetic alloy FeNi and semiconductor ZnO nanoparticles (NPs) with different FeNi/ZnO ratios (1:1, 1:2, and 2:1) is presented. The resulting nanocomposites were employed as electromagnetic wave absorbers in the microwave range, and their structural and magnetic properties were investigated. Scanning and transmission electron microscopic analyses of FeNi/ZnO NP composites (NPCs) revealed crystalline particulates with spherical and conical morphology. Saturation magnetization and coercivity significantly increased to 161 Oe and 90 emu/g after performing an annealing process, starting from 77 Oe and 26 emu/g for as-synthesized (FeNi)2/(ZnO)1 NPC. In this case, a high reflection loss of −37.3 dB at 11.8 GHz was obtained for the NPC with an optimum thickness of 1.6 mm. Our calculations indicate that the eddy current effect plays a crucial role in the electromagnetic loss of magnetic alloy/semiconductor NPCs. © 2021 Elsevier B.V.
