Nanostructuring silica-iron core-shell particles in a one-step aerosol process.

Silica-coated iron (Fe@SiO2) particles have attracted considerable interest as a potential powder core material due to their distinctive advantages, including higher magnetic saturation and enhanced electrical resistance. In this study, the submicron-sized core-shell Fe@SiO2 particles were successfully synthesized in a single step via an aerosol process using a spray pyrolysis method assisted by a swirler connector for the first time. Changing the reducing agent concentration (supplied H2) and tuning the number of core (Fe) particles were investigated to achieve the desired Fe@SiO2 particles. The results indicated that an excessive number of cores led to the appearance of FeO crystals due to insufficient reduction. Conversely, an insufficient number of cores resulted in a thicker SiO2 shell, which hindered the penetration of the supplied H2 gas. Furthermore, the produced Fe@SiO2 particles exhibited soft-ferromagnetic characteristics with an excellent magnetic saturation value of 2.04 T, which is close to the standard theoretical value of 2.15 T. This work contributes new insights into the production of core-shell Fe@SiO2 particles, expanding their applicability to advanced soft-magnetic materials.

Controlling the Magnetic Responsiveness of Cellulose Nanofiber Particles Embedded with Iron Oxide Nanoparticles.

2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofiber (TOCN) particles, an innovative biobased material derived from wood biomass, have garnered significant interest, particularly in the biomedical field, for their distinctive properties as biocompatible particle adsorbents. However, their microscopic size complicates their separation in liquid media, thereby impeding their application in various domains. In this study, superparamagnetic magnetite nanoparticles (NPs), specifically iron oxide Fe3O4 NPs with an average size of 15 nm, were used to enhance the collection efficiency of TOCN-Fe3O4 composite particles synthesized through spray drying. These composite particles exhibited a remarkable ζ-potential (approximately -50 mV), indicating their high stability in water, as well as impressive magnetization properties (up to 47 emu/g), and rapid magnetic responsiveness within 60 s in water (3 wt % Fe3O4 to TOCN, 1 T magnet). Furthermore, the influence of Fe3O4 NP concentrations on the measurement of the speed of magnetic separation was quantitatively discussed. Additionally, the binding affinity of the synthesized particles for proteins was assessed on a streptavidin-biotin binding system, offering crucial insights into their binding capabilities with specific proteins and underscoring their significant potential as functionalized biomedical materials.

Controllable Synthesis of Porous and Hollow Nanostructured Catalyst Particles and Their Soot Oxidation.

The introduction of macroporous structures into three-way catalysts (TWCs) through polymer template-assisted spray drying has attracted attention because of its enhanced gas diffusion and catalytic performance. However, the surface charge effect of polymeric template components has not been investigated to control the structure of the TWC particles during synthesis. Thus, this study investigated the effect of template surface charges on the self-assembly behavior of TWC nanoparticles (NPs) during drying. The self-assembly of TWC NPs and polymer particles with different charges produced a hollow structure, whereas using the same charges generated a porous one. Consequently, the mechanism of particle self-assembly during drying and final structure particle formation is proposed in this study. Here, porous TWC particles demonstrated a faster oxidation of soot particles than that of hollow-structured particles. This occurred as a result of the larger contact area between the catalyst surface and the solid reactant. Our findings propose a fundamental self-assembly mechanism for the formation of different TWC structures, thereby enhancing soot oxidation performance using macroporous structures.

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.