Ni_0.5Zn_0.5Fe₂O₄ nanofibers with an average diameter of 133.56 ± 12.73 nm were fabricated by electrospinning and calcination. According to our thermogravimetric—differential thermal analysis and X-ray diffraction results, the calcination temperature was 650 °C. The microstructure, crystal structure, and chemical composition of the nanofibers were observed using field-emission scanning electron, X-ray diffraction, and energy-dispersive X-ray spectroscopy. Commercial particle samples and samples containing 10 wt% and 20 wt% nanofibers were fabricated, and the electromagnetic properties were analyzed with a vector network analyzer and a 7.00 mm coaxial waveguide. Regardless of the nanofiber content, Ni_0.5Zn_0.5Fe₂O₄ was dominantly affected by the magnetic loss mechanism. Calculation of the return loss based on the transmission line theory confirmed that the electromagnetic wave return loss was improved up to −59.66 dB at 2.75 GHz as the nanofiber content increased. The absorber of mixed compositions with Ni_0.5Zn_0.5Fe₂O₄ nanofibers showed better microwave absorption performance. It will be able to enhance the performance of commercial electromagnetic wave absorbers of various types such as paints and panels.

The term electromagnetic pulse (EMP) generally refers to high-power electromagnetic waves and can be classified into EMPs caused by nuclear weapons, non-nuclear EMPs, and EMPs caused by natural phenomena. EMPs can cause catastrophic damage to any electronic device consisting of electromagnetic components, including communications devices and transportation. In this study, the shielding effectiveness of paint was evaluated depending on the type and content of carbon material and binder. To analyze the compatibility and dispersibility improvement of the raw materials used in paint manufacturing, experiments were conducted in two stages, using 27 mixtures. The shielding effectiveness was evaluated for the optimal mixture developed through mixture experiments. The results of this study confirmed that the developed EMP shielding paint can improve the shielding effectiveness of concrete by 25–40 dB. Additionally, the adhesion strength and moisture resistance evaluation of the EMP shielding paint were evaluated. The average adhesive strength of the EMP shielding paint was 1.26 MPa. In moisture-resistance testing at a temperature of 50 ± 3 °C and a relative humidity of 95% or higher for more than 120 h, no cracks or peeling were observed on the painted surface.