Enhanced Electroresponse of Alkaline Earth Metal-Doped Silica/Titania Spheres by Synergetic Effect of Dispersion Stability and Dielectric Property.
A series of alkaline earth metal-doped hollow SiO2/TiO2 spheres (EM-HST) are prepared as electrorheological (ER) materials via sonication-mediated etching method with various alkaline earth metal hydroxides as the etchant. The EM-HST spheres are assessed to determine how their hollow interior and metal-doping affects the ER activity. Both the dispersion stability and the dielectric properties of these materials are greatly enhanced by the proposed one-step etching method, which results in significant enhancement of ER activity. These improvements are attributed to increased particle mobility and interfacial polarization originating from the hollow nature of the EM-HST spheres and the effects of EM metal-doping. In particular, Ca-HST-based ER fluid exhibits ER performance which is 7.1-fold and 3.1-fold higher than those of nonhollow core/shell silica/titania (CS/ST) and undoped hollow silica/titania (HST)-based ER fluids, respectively. This study develops a versatile and simple approach to enhancing ER activity through synergetic effects arising from the combination of dispersion stability and the unique dielectric properties of hollow EM-HST spheres. In addition, the multigram scale production described in this experiment can be an excellent advantage for practical and commercial ER application.
School of Chemical and Biological Engineering, Seoul National University , 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea.
Chang-Min
CM
Yoon
School of Chemical and Biological Engineering, Seoul National University , 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea.
Seungae
S
Lee
School of Chemical and Biological Engineering, Seoul National University , 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea.
Oug Jae
OJ
Cheong
School of Chemical and Biological Engineering, Seoul National University , 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea.
Jyongsik
J
Jang
alkaline earth metal; electroresponsive; electrorheology; hollow; metal-doping; silica; titania