Fabrication of Fe–B/epoxy composite film via LbL-assisted composite plating using silica-coated Fe–B particles

Research on electromagnetic wave absorption materials that can be used at high frequencies above the GHz band has been attracting attention. For this application, in our development of soft magnetic Fe–B particles embedded in epoxy resin composite films, this study aims to improve the particle content and dispersion of Fe–B particles within epoxy films. To prevent oxidation and to enhance the dispersion of Fe–B particles, they were coated with silica using the liquid-phase hydrolysis method. The submicron-sized silica-coated Fe–B particles are expected to exhibit lower eddy current losses. Importantly, the silica coating prevented the oxidation of Fe–B particles, thereby suppressing magnetic properties degradation. Fe–B/epoxy composite films were fabricated using silica-coated Fe–B particles via the layer-by-layer assisted composite plating method. The composite film produced with an Fe–B particle concentration of 10 g/l achieved a particle content of 90.1 wt. % and exhibited a real part of complex permeability (μ′) of 1.5 at 1 GHz.