Limited Electron-Dominated Electrorheological Response with TiO₂ Buffer Layer

We report porous carbon sphere electrorheological (ER) nanoparticles coated with a titanium dioxide layer (HCs@TiO₂). Utilizing the buffering effect of amorphous TiO₂, the HCs@TiO₂ ER fluid (ERF) shows a yield stress that exceeds that of previous carbon-based ER nanomaterials. The mechanisms of the high ER response are elucidated through the analysis of the dielectric properties, demonstrating that the amorphous TiO₂ shell not only restricts the electron-dominated motion but also significantly improves the interfacial polarization. Furthermore, the HCs@TiO₂ ERF exhibits superior sedimentation stability and low current density, which is attributed to the formation of a hydrogen bond network. The rheological behavior of HCs@TiO₂ ERF is analyzed using the Bingham and Cho-Choi-Jhon model, where the dynamic yield stress as a function of electric field strength is fitted using a generalized yield stress equation. These analyses indicate that local electrostatic accumulation between the hybrid shells benefits the ER response.