Key Words:Electrorheological fluids;Dielectric spectroscopy - Electric fields - Low-k dielectric - Nanofluidics - Nanospheres - Permittivity - Polarization - Rheology - Silica - Titanium compounds;Critical factors - Disperse particles - Electric field force - Electrorheological behavior - Frequency ranges - Polarizabilities - Polarized particles - Structural evolution
Abstract:Monodisperse SiO<inf>2</inf>/TiO<inf>2</inf>yolk-shell nanospheres (YSNSs) with different SiO<inf>2</inf>core sizes were fabricated and adopted as dispersing materials for electrorheological (ER) fluids to investigate the influence of the gradual structural change of disperse particles on ER properties. The results showed that the ER performance of the YSNS-based ER fluid prominently enhanced with the decrease of SiO<inf>2</inf>core size, which was attributed to the enhancement of electric field force between YSNSs. Combined with the analysis of dielectric spectroscopy, it was found that the increase of permittivity at low frequency (10<sup>-2</sup>-10<sup>0</sup>Hz) was due to the increase of polarized charges caused by secondary polarization (P<inf>sp</inf>). Moreover, the number of P<inf>sp</inf>closely related to the distributing change of polarized particles in ER fluid was a critical factor to assess the ER performance. Additionally, a parameter K (the absolute value of the slope of permittivity curves at 0.01 Hz) could be utilized to characterize the efficiency of structural evolution of polarized particles in ER fluid. Compared with the ER performance, it could be concluded that the value of ΔΕ<inf>(100Hz-100kHz)</inf>′ just demonstrated the initial intensity of the interface polarization in the ER fluid as the electric field was applied, which ignored the distributing evolution of polarized disperse particles in ER fluid. The polarizability ΔΕ<inf>(0.01Hz-100kHz)</inf>′ obtained in the frequency range of 10<sup>-2</sup>-10<sup>5</sup>Hz should be more suitable for analyzing the system of ER fluid. The relationships between polarizability of disperse particles, parameter K and ER properties were discussed in detail.<br/> © The Royal Society of Chemistry 2016.
Volume:12
Issue:2
Translation or Not:no
