Preparation and electrorheological characteristics of uniform core/shell structural particles with different polar molecules shells

The core/shell structural dielectric particles are applied widely in the electrorheological (ER) fluids. In this work, we rationally designed and constructed two kinds of core/shell structured SiO2-based particles with TiO2 and hydroxyl titanium oxalate (TOC) as shell, respectively. The obtained core/shell structural SiO2/TiO2 and SiO2/TOC particles were well dispersed spherical nanoparticles with ideal morphology and a narrow size distribution. Under DC electric fields, the ER effect of the two kinds of core/shell particles dispersed in electrically insulating oil was examined and compared by steady shear flow and dynamic shear modes. It was found that the SiO2/TOC ER fluid showed a stronger ER effect compared to the SiO2/TiO2 ER fluid. The static yield stress of the SiO2/TOC ER fluid was up to 45 kPa at 5 kV/mm, which was twice of the SiO2/TiO2 ER fluid and 9 times of the SiO2 ER fluid. On the other hand, the zero field viscosity of the SiO2/TOC ER fluid was obviously lower than that of the SiO2/TiO2 ER fluid. Therefore, the ER efficiency of the SiO2/TOC ER fluid was much higher than that of SiO2/TiO2 ER fluid at the same electric field.