Wenpeng Jia, Ming Zhou, Xiangjun Zhang and Yu Tian* Pages 49 - 55 ( 7 )
Background: As a kind of intelligent materials, electrorheological (ER) fluids have been researched increasingly deeply and widely. Dynamic viscoelastic property is an innate and important property of EF fluids, which can be controlled by external electric field strength (E). However, viscoelasticity of zeolite-based ER fluids has not been researched deeply in small strain under enhanced E.Methods: This work is focused on the dynamic viscoelasticity under enhanced E with small oscillation amplitude. In this work, zeolite-based ER fluids were prepared with five mass fractions, and their dynamic viscoelastic properties were measured by a commercial rheometer under small amplitude oscillation in E sweep mode. Results: Two singular points including the inflected point and the crossover point under different angular frequencies were observed for the first time in various concentrations of ER fluids when chains or clusters formed with E increasing. The inflected E increased with mass fraction of ER fluid increasing, while loss tangent (tanθ) decreased slightly. The crossover E decreased with mass fraction of ER fluid increasing, while tanθ increased. Conclusion: In this work, ER fluids in five mass fractions showed concentration-dependent inflection of tanθ, in which inflected E increased and inflected tanθ decreased slightly with the concentration increasing. The inflection was ascribed to similar elastic properties and viscous force under applied electric field in different angular frequencies here. Besides, the crossover of tanθ showed frequencyindependent and concentration-dependent properties which were explained by a viscoelastic model.
Concentration, crossover point, dynamic viscoelasticity, ER fluids, incremental electric field, inflected point, loss tangent.
State Key Laboratory of Tribology, Tsinghua University, Beijing, Institute of Mechanical Manufacturing Technology, CAEP, Mianyang, State Key Laboratory of Tribology, Tsinghua University, Beijing, State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing