Controllable synthesis and enhanced microwave absorbing properties of Fe3O4/NiFe2O4/Ni heterostructure porous rods

Abstract We developed a coordinated self-assembly/precipitate transfer/sintering method that allows the controllable synthesis of Fe 3 O 4 /NiFe 2 O 4 /Ni heterostructure porous rods (HPRs). A series of characterizations confirms that changing [Ni 2+ ] can effectively control the crystal size, internal strain, composition, textural characteristics, and properties of HPRs. Molar percentages of Ni and NiFe 2 O 4 in HPRs increase with [Ni 2+ ] in various Boltzmann function modes. Saturation magnetization M s and coercivity H c show U-shaped change trends because of crystal size, composition, and interface magnetic coupling. High magnetic loss is maintained after decorating NiFe 2 O 4 and Ni on the surface of Fe 3 O 4 PRs. Controlling the NiFe 2 O 4 interface layers and Ni content can improve impedance matching and dielectric losses, thereby leading to lighter weight, stronger absorption, and broader absorption band of Fe 3 O 4 /NiFe 2 O 4 /Ni HPRs than Fe 3 O 4 PRs. An optimum EM wave absorbing property was exhibited by Fe 3 O 4 /NiFe 2 O 4 /Ni HPRs formed at [Ni 2+ ] = 0.05 M. The maximum reflection loss ( R L ) reaches −58.4 dB at 13.68 GHz, which corresponds to a 2.1 mm matching thickness. The absorbing bandwidth ( R L  ≤ −20 dB) reaches 14.4 GHz with the sample thickness at 1.6–2.4 and 2.8–10.0 mm. These excellent properties verify that Fe 3 O 4 /NiFe 2 O 4 /Ni HPRs are promising candidates for new and effective absorptive materials.