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Proceedings Paper

Magnetorheological fluids exploiting nanometer-sized particles
Author(s): Shaju John; Jin-Hyeong Yoo; Norman M. Wereley; Radhakumar Radhakrishnan; T. S. Sudarshan
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Paper Abstract

Magnetorheological(MR) fluids are suspensions of magnetic particles in a carrier fluid. The rheological properties of MR fluids undergo changes on application of magnetic field. MR fluids made using nanometer sized soft magnetic iron particles were studied for their benefits vis-a-vis flow characteristics and settling properties. Three kinds of MR fluids were synthesized using the microwave process (1) 30 micrometers sized iron particles (2) 26.5 nm sized iron particle (3) a mixture of micron and nanometer sized iron particles . The fluids were suspensions of micron, nanometer as well as a mixture of nanometer and micron sized powders. Standard static and dynamic yield stress measurements were performed using a parallel disc oscillatory rheometer. The flow properties of these fluids were then characterized using the Bingham-Plastic, Eyring-Plastic and the Herschel-Buckley models. This paper investigates the rheological properties of these fluids and assesses their advantages and disadvantages. The pure micron powder yielded an MR fluid with highest yield stress, but had the most rapid settling. The nano sized powders overcame the problem of settling because of the predominance of thermodynamic forces at that scale, but they yielded a considerably lower yield stresses. A hybrid combination of micron and nano sized powders was an effective compromise to exploit the high yield stress provided by the micron powders and the self dispersing properties of the nano sized powders. We characterized these mixtures using existing rheological models. A key conclusion is that it may be possible to synthesize MR fluids with significant yield stress, while mitigating settling through the use of nanoscale powders.

Paper Details

Date Published: 11 July 2002
PDF: 12 pages
Proc. SPIE 4699, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics, (11 July 2002); doi: 10.1117/12.475004
Show Author Affiliations
Shaju John, Univ. of Maryland/College Park (United States)
Jin-Hyeong Yoo, Univ. of Maryland/College Park (United States)
Norman M. Wereley, Univ. of Maryland/College Park (United States)
Radhakumar Radhakrishnan, Materials Modification Inc. (United States)
T. S. Sudarshan, Materials Modification Inc. (United States)

Published in SPIE Proceedings Vol. 4699:
Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics
Christopher S. Lynch, Editor(s)

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