Studies on the effects of material properties structure and electrode morphology in the electrorheological response
Katsikopoulos, Panagiotis Vassiliou
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/22439
Description
Title
Studies on the effects of material properties structure and electrode morphology in the electrorheological response
Author(s)
Katsikopoulos, Panagiotis Vassiliou
Issue Date
1996
Doctoral Committee Chair(s)
Zukoski, Charles F.
Department of Study
Chemical and Biomolecular Engineering
Discipline
Chemical and Biomolecular Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Physical
Chemistry, Polymer
Engineering, Chemical
Language
eng
Abstract
"The electrorheological (ER) phenomenon refers to the orders of magnitude increases in the apparent viscosity and/or the development of a yield stress in suspensions of polarizable particles in a low permittivity continuous phase upon the application of large electric fields (O(1kV/mm)). In this dissertation the effects of finite conductivities were studied. Particles with conducting cores covered with an insulating layer show large yield stresses at low electric fields ($$10$\sp{-7}$ S/cm) is attributed to the existence of interfaces that control the local electric field experienced by the particles. The observed behavior cannot be explained within the framework of the existing theories. To describe the experimental results we modeled the ER fluid as a two layer dielectric. One layer has the dielectric and conducting properties of bulk polyaniline while the other is assumed to be an ""interface"". Such a model is successful in representing qualitatively the observed behavior. Another effect demonstrating the importance of interfaces is displayed in water activated ER fluids with very low water contents. While these fluids under DC conditions behave as weak ER fluids, at low AC frequencies ($<$50Hz) the particles perform an oscillatory motion following the changing polarity of the electric field and no electrode spanning structure is observed. Nevertheless, an increase in the shear stress over that of the unelectrified suspension is measured. A simple model based on convective momentum transfer due to the particle motion succeeds in representing the dependence of the excess stress on the electric field strength, shear rate and electric field frequency. Alterations in the structure result in a weak dependence on the steady state and dynamic behavior of ER fluids."
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
