Synthesis of Silica-Coated Iron (Fe@SiO x ) Particles with High Stability and Fast Magnetic Responsiveness

Submicrometer-sized silica-coated Fe (Fe@SiO x ) particles offer a promising solution to the limitations of nanoscale Fe, such as instability, toxicity, and aggregation, while maintaining strong magnetic properties essential for energy and biomedical applications. In this study, a scalable gas-phase synthesis approach using spray pyrolysis followed by postheating under H 2 /Ar to produce nonaggregated submicrometer Fe@SiO x particles is presented. The postheating temperature and time were varied, and the associated particle formation mechanism was examined. The results underscore remarkable coupled effects of postheating parameters on both the core and shell components associated with the FeO to Fe reduction and SiO x migration. This interplay enables fine-tuning of the core–shell structure to achieve high saturation magnetization, rapid magnetic response, good dispersibility, and stability. The Fe@SiO x particles processed under optimized conditions demonstrate good potential for use in inductive electronics, environmental, and biomedical applications. This study offers a practical route to engineering robust Fe-based materials for multifunctional use in advanced technologies.