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[Display omitted] • Fe–Si/SiO 2 soft ferromagnetic composites prepared via novel two-step method. • SiO 2 insulation coating thickness increased linearly with deposition duration. • SiO 2 insulation coating process had no influence on Fe–Si crystal structure. • SiO 2 insulation coating thickness predicted total core loss. • Quantitative equations relating electromagnetic properties to deposition duration. The industrial production of soft ferromagnetic composites demands a quantitative description of process parameters and magnetic performance. Here, Fe–Si/SiO 2 soft ferromagnetic composites were prepared via a two-step method combining chemical vapour deposition and hot-pressed sintering. Investigations of surface and section morphology, phase composition and crystal structure were undertaken to characterise the deposition duration-dependence of SiO 2 insulation coating thickness in Fe–Si/SiO 2 soft ferromagnetic composites. A vibrating sample magnetometer, a resistivity tester and a B–H analyser were used to study the magnetic behaviours of Fe–Si/SiO 2 soft ferromagnetic composites. Based on curves of deposition duration-dependence of SiO 2 insulation coating thickness and other theoretical models, quantitative relationships between deposition duration and magnetic performance were determined for Fe–Si/SiO 2 soft ferromagnetic composites. These results demonstrate that the coating and crystallisation of SiO 2 insulation coatings had no influence on the crystal structure of Fe–Si substrate particles and that SiO 2 insulation coating thickness increased linearly with deposition duration. Total core loss of Fe–Si/SiO 2 soft ferromagnetic composites was strongly predicted by SiO 2 insulation coating thickness. A quantitative equation relating magnetisation intensity to Fe–Si/SiO 2 soft ferromagnetic composite deposition duration was derived on the basis of experimental data and subsequent model selection. Additional quantitative equations relating electrical resistivity and eddy current loss to Fe–Si/SiO 2 soft ferromagnetic composite deposition duration were determined according to electromagnetic theory. These results establish a precise adjustment mechanism for magnetic behaviour in Fe–Si/SiO 2 soft ferromagnetic composites and promote the industrialisation of a new preparation process combining chemical vapour deposition and hot-pressed sintering. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gained FeSiCr-based SMCs with a CeO 2 ·SiO 2 composite layer by selective oxidation between substrate and CeO 2 insulation layer. • The CeO 2 insulation layer promotes selective oxidation of Si in substrate during sintering in water vapor environment. • CeO 2 ·SiO 2 composite insulation layer demonstrated a 22.9% reduction in core loss than using the CeO 2 insulating layer alone. • CeO 2 ·SiO 2 composite insulation layer mitigated core loss while maintaining high magnetic conductivity in FeSiCr-based SMCs. This study introduces an approach to fabricating soft magnetic composites (SMCs) that effectively address core loss while maintaining high magnetic conductivity. During the sintering process in a water vapor environment, the CeO 2 insulation layer facilitates the selective oxidation of Si while simultaneously impeding the outward diffusion of Fe and Cr. Consequently, a CeO 2 ·SiO 2 composite insulation layer forms within the FeSiCr-based SMCs. The FeSiCr-based SMCs with the CeO 2 ·SiO 2 composite insulation layer achieve a saturation magnetization of 153.1 emu/g, which is 10.9% lower than that of FeSi 3.7 Cr 4.5 compacts, and exhibits a deterioration rate lower than previously reported values. Moreover, the permeability of the FeSiCr-based SMCs remains highly stable, demonstrating outstanding insulation characteristics. The total core loss and core loss separation results further corroborate that incorporating a CeO 2 ·SiO 2 composite insulation layer leads to a more pronounced reduction in interparticle eddy current loss than using a CeO 2 insulating layer alone. This performance enhancement can be attributed to the selective oxidation of a rare metal oxide insulation layer on a ferromagnetic metal particle substrate, a technique applied to SMCs for the first time. These findings hold significant implications for the design of high-performance SMCs in miniaturized and lightweight electromagnetic devices. [ABSTRACT FROM AUTHOR]