Synthesis of Submicron-Sized Spherical Silica-Coated Iron Nickel Particles with Adjustable Shell Thickness via Swirler Connector-Assisted Spray Pyrolysis

Silica-coated iron nickel (FeNi@SiO2) particles have attracted significant attention because of their potential applications in electronic devices. In this work, submicron-sized spherical FeNi@SiO2 particles with precisely controllable shell thickness were successfully synthesized for the first time using a swirler connector-assisted spray pyrolysis system, comprising a preheater, specific connector, and main heater. The results indicated that the thickness of the SiO2 shell can be tuned from 3 to 23 nm by adjusting the parameter conditions (i.e., preheater temperature, SiO2 supplied amount). Furthermore, our fabrication method consistently yielded a high coating ratio of more than 94%, indicating an excellent quality of the synthesized particles. Especially, to gain an in-depth understanding of the particle formation process of the FeNi@SiO2 particles, a plausible mechanism was also investigated. These findings highlight the importance of controlling the preheater and SiO2 supplied amount to obtain FeNi@SiO2 particles with desirable morphology and high coating quality

One-Step Aerosol Synthesis of SiO₂‑Coated FeNi Particles by Using Swirler Connector-Assisted Spray Pyrolysis

Silica-coated soft magnetic particles are essential for some powder magnetic cores consisting of primary (coarse particles) and secondary (fine particles) soft magnetic particles in the advancement of electric devices. Herein, we report the first investigation on the direct synthesis of submicron-sized silica-coated FeNi (FeNi@SiO2) particles as the secondary particle using a connector-assisted spray pyrolysis route. Provided by computational fluid dynamics calculation in applying different connector types, i.e., T-shaped and swirler, we found that the mixing performance between FeNi and HMDSO vapor in the swirler connector played an important role in resulting heterogeneous nucleation, which is crucial for obtaining the higher coating ratio (CR) and fewer undesired nanoparticles than that of the T-shaped connector. The as-prepared submicron-sized FeNi@SiO2 particles (353 nm) with the highest CR (95.9%) demonstrated a remarkable DC bias characteristic (Isat) and eddy current loss values on a powder magnetic core, promising the practical application in manufacturing soft magnetic components