Low material density and high microwave-absorption performance of hollow strontium ferrite nanofibers prepared via coaxial electrospinning

Hollow strontium ferrite (SrFe12O19: SrM) nanofibers have been successfully synthesized by coaxial electrospinning with the advantages of low material density and high microwave absorption performance. SrM precursors were used for coaxial electrospinning and annealing at different temperatures (600 °C, 650 °C, 700 °C, and 750 °C). A variety of characterization methods-XRD, TG, SEM, TEM, EDS, VSM and VNA-are used to analyze their particle size, morphology, magnetic response and absorption performance. The outer and inner diameters of hollow nanofibers annealed at 750 °C are 28 and 16 nm, respectively. The hollow structure is clearly visible, and as per calculation results, the material density is nearly 48.5% lower than that of solid fibers with the same diameter. The magnetism properties improve with increasing nanoparticle sizes for the single-domain particles. The saturation magnetization and the coercivity of the hollow nanofibers at 750 °C are 57.8 A m2 kg−1 and 333.9 kA m−1, respectively. When the thickness of the absorber coating was 3.4 mm, the electromagnetic radiation reflection loss reached −12.69 dB at 11.68 GHz. The calculated reflection loss of the hollow sample is better than that of solid fibers; the maximum ratio of structure reduction is 14.5%. Further, the mechanism of SrM formation and the mechanism of the improvement of the microwave absorption properties are discussed.