Core-shell structured mesoporous magnetic nanoparticles and their magnetorheological response

As a new magneto-responsive smart material, core-shell structured mesoporous Fe3O4@mSiO(2) nanoparticles were fabricated by a surfactant-based sol-gel approach using Fe3O4 nanoparticles, and then adopted as magnetorheological (MR) materials. The Fe3O4 particles were initially synthesized by a solvo-thermal process. Scanning electron microscopy and transmission electron microscopy were employed to observe the morphology of the as-synthesized mesoporous silica-coated Fe3O4 particles. Fourier transform infrared spectroscopy and Xray diffraction results showed that the mesoporous silica shell is successfully coated on the Fe3O4 nanoparticles. BET adsorption measurement also confirmed their mesopore formation. Rheological properties of the silica coated Fe3O4-based MR fluid dispersed in silicone oil were investigated, and a change in the slope of the yield stress as a function of magnetic field strength from 2.0 to 1.5 was observed, with improved dispersion stability.