Shape-Controlled Syntheses of Magnetite Microparticles and Their Magnetorheology

Abstract

Magnetic microspheres in a concentrated suspension can be self-assembled to form chain structures under a magnetic field, resulting in an enhanced viscosity and elasticity of the suspension (i.e., the magnetorheological (MR) effect). Recently, interest has been raised about the relationship between nonspherical particles, such as octahedral particles and the MR effect. However, experimental studies have not made much progress toward clarifying this issue due to the difficulty associated with synthesizing microparticles with well-defined shapes and sizes. Here, we presented a method for the shape-controlled synthesis of magnetite (Fe3O4) microparticles and investigated the MR effects of two suspensions prepared from the two shape-controlled samples of Fe3O4 microparticles. Our method, which was based on the polyol method, enabled the preparation of spherical and octahedral Fe3O4 microparticles with similar sizes and magnetic properties, through a reduction of α-FeOOH in a mixed solvent of ethylene glycol (a polyol) and water. The water played an important role in both the phase transition (α-FeOOH to Fe3O4) and the shape control. No substantial difference in the MR effect was observed between an octahedral-particle-based suspension and a spherical-particle-based one. Therefore, in this study, the shape of the microparticles did not strongly influence the MR effect, i.e., the properties of the chain structures.

Direct observation of potential phase at joining interface between p-MgO and n-MgFe2O4

“…Magnetite (Fe 3 O 4 ) spherical particles with the diameter of ca. 1 µm were obtained by dissolving iron oxyhydroxide in a solvent (ethylene glycol and 9 wt% H 2 O) and hydrothermally treating it at 200 °C for 24 h in an autoclave, as described in our previously published work 33 . An Fe 2 O 3 spherical powder with a particle size of 1 μm was then obtained by heat-treating (800 °C, 3 h).…”

Physicochemical Transformation Effect on the Relaxivity Enhancement of Iron Oxide Nanoparticles in Nuclear Medicine and MRI Imaging

“…The synthesis method can affect the size and structure of the crystal. Consequently, the structural features of IONPs are too significant since the MRI contrast enhancement effect of IONPs is attributed in large part to their structural features [30].…”

Review of the Applications of Biomedical Compositions Containing Hydroxyapatite and Collagen Modified by Bioactive Components

“…Along with the currently observed development of nanotechnology, the appearance of various magnetic colloidal particles with a nanometric size has been denoted [ 171 ]. A great interest in this research topic directly translates into the wide application of such particles in biomedicine, e.g., in cancer treatment, drug delivery, or diagnostics [ 172 , 173 ]. Particular attention is directed toward the iron oxide that is widely applied in systems of controlled drug release [ 174 ].…”