Transparent thiourea treated silica suspension through refractive index matching method and its electrorheology

Silica nanoparticles treated with thiourea were adopted as the solid dispersed phase of an eletrorheological (ER) fluid that underwent orders of magnitude changes in its rheological properties upon the application of an electric field. To fabricate a transparent ER fluid, medium oils with three different refractive indices (RI) were prepared by mixing halocarbon oil and silicone oil, in which the amount of oils needed was estimated based on the Lorentz–Lorentz equation. Thiourea-modified silica nanoparticles dispersed in the oil mixture with the same RI as these particles exhibited the transparency of an ER fluid as well as typical ER characteristics, based on flow curve and dielectric spectra.