Abstract
ZnFe2O4 particles initially synthesized through a simple solvothermal method were coated using polyindole (PIn) to prepare an actively controllable core-shell typed hybrid material under both electric and magnetic fields. An advantage of this process is not needing to add the stabilizers or surfactants commonly used for uniform coating when synthesizing core or shell-structured particles. The synthesized ZnFe2O4/PIn particles have a lower density than conventional magnetic particles and have suitable properties as electrorheological (ER) particles. The expected spherical shape of the particles was proven using both scanning electron microscopy and transmission electron microscopy. The chemical characterization was performed using Fourier-transform infrared spectroscopy and X-ray diffraction analysis. To analyze the rheological properties, a ZnFe2O4/PIn based suspension was prepared, and dynamic rheological measurements were performed for different electric field strengths using a rotary rheometer. Both dynamic and elastic yield stresses of the ER fluid had a slope of 1.5, corresponding to the conductivity model. Excellent ER effect was confirmed through rheological analysis, and the prepared ER fluid had a reversible and immediate response to repeated electric fields.
Highlights
IntroductionElectrorheological (ER) and magnetorheological (MR) fluids are actively controllable systems that respond to external electric and magnetic fields, respectively
Suspension under an Electric Field.Smart materials whose properties can be tuned by various external stimuli have received widespread interest in many engineering fields [1].Among these, electrorheological (ER) and magnetorheological (MR) fluids are actively controllable systems that respond to external electric and magnetic fields, respectively.ER fluids are systems in which electrically polarizable particles are homogeneously suspended in an in-active carrier medium
In contrast to the ER fluid, MR fluid is a suspension in which soft-magnetic particles are randomly dispersed in a matrix liquid; this enables the fluid physical structure to be changed in a reversible nature as described above, with the presence of an external magnetic field [9,10]
Summary
Electrorheological (ER) and magnetorheological (MR) fluids are actively controllable systems that respond to external electric and magnetic fields, respectively. By coating a conductive polymer on magnetic particles used as MR materials, electro-magnetorheological (EMR) particles, which are dual-responsive materials that respond in both magnetic and electric fields, can be synthesized. A conductive PIn polymer was coated on the surface of magnetic ZnFe2 O4 particles for the synthesis of a dual-responsive EMR fluid. While its fabrication and dual performance of the EMR fluid has been reported recently [21], in this work, we put our emphasis on its more detailed dynamic ER response under an applied E along with its dielectric behavior
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