Formation of Magnetic Fe_xO_y/Silica Core-Shell Particles in a One-Step Flame Aerosol Process

Abstract

In this study, iron silicon oxide particles were generated in a onestep flame assisted spray pyrolysis (FASP) process using H 2 /air or H 2 /O 2 diffusion flames. A colloidal precursor solution was used, which contained dissolved iron nitrate and stably suspended silica nanoparticles. H 2 /air flames resulted in magnetic Fe x O y /silica core-shell particles. There was a correlation between particle size and particle structure; particles larger than 500 nm had the coreshell structure, but smaller particles had non-core-shell structures. H 2 /O 2 flames only resulted in nanoparticles that had non-coreshell structures. The core-shell particles had a iron oxide core that was hermetically enclosed in a uniform silica shell with a typical thickness of approximately 100 nm; they were superparamagnetic with a room-temperature saturation magnetization greater than 24 emu/g. Temperature history of the particles may be used to explain the correlation between flame type and particle structure. The correlation between particle size and structure may be due to size-dependent thermodynamic stability of the structures, or kinetics of heat and mass transfer. The results from this study suggest that micrometer sized iron oxide silica core-shell magnetic particles could be generated from a one-step flame aerosol process, but Fe x O y /silica nanoparticles (<100 nm) with the coreshell structure cannot be generated in a one-step flame aerosol process.

Double-faced γ-Fe2O3||SiO2 nanohybrids: flame synthesis, in situ selective modification and highly interfacial activity

“…The phase diagram also suggests that the melting point of the respective substances has a dominant role in describing the formation process of phase segregated Fe 2 O 3 -SiO 2 nanocomposites. To investigate the structure of the corresponding intermediate species, the sample quickly deposited on a tiny ceramic substrate in ame was used for TEM observation because this thermophoretic technique 40,41 could keep the morphology structure due to immediate cooling of the sample in an extremely short time. Fig.…”

Gas phase condensation of superparamagnetic iron oxide–silica nanoparticles – control of the intraparticle phase distribution

“…15 Flame spray pyrolysis is utilized by a variety of groups to produce iron oxide-silica powders with varying particle sizes (nm-µm). [16][17][18][19][20] Zachariah et al extensively studied the morphology and formation of iron oxide NPs and iron oxide-silica nanocomposites produced in a flame spray reactor. They first reported the gas phase synthesis of superparamagnetic iron oxide-silica NPs 20 and published in situ studies on their formation.…”

Aerosol Science and Technology: History and Reviews

“…Nevertheless, the capacity of flame spray aerosol reactors (Figure 5), in particular, to form new materials, nanothin hermetically layered particles (Teleki et al, 2008;Phillips et al, 2009;Guo et al, 2010), and even highly porous (98%) nanostructured semiconducting micropatterns on electronic circuitry (Tricoli et al, 2008) creates the opportunity to make products with new properties and functionalities. These products include catalysts (Strobel et al, 2006b), sensors , transparent but radiopaque dental prosthetics (Schulz et al, 2005), phosphor particles (Camenzind et al, 2005;Purwanto et al, 2008) and films (Kubrin et al, 2010), lithium-ion battery materials Ernst et al, 2007), nutritional supplements (Rohner et al, 2007) with rigorous physiological evaluation (Hilty et al, 2010), anti-fogging films made by in situ grown silica nanowires (Tricoli et al, 2009), and even highly durable sorbents for CO 2 sequestration (Lu et al, 2009).…”