Dimorphic magnetorheological fluids: Exploiting partial substitution of microspheres by nanowires

G. T. Ngatu, N. M. Wereley, J. O. Karli, R. C. Bell

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94 Scopus citations


Magnetorheological (MR) fluids typically are suspensions of spherical micron-sized ferromagnetic particles suspended in a fluid medium. They are usually thought of as Bingham-plastic fluids characterized by an apparent yield stress and viscosity. Partial substitution of the micron-sized iron particles with rod-shaped nanowires constitutes a dimorphic MR fluid. In this study, we investigate the influence that nanowires have on the magnetorheological and sedimentation properties of MR fluids. A variety of conventional and dimorphic MR fluid samples were considered for this study with iron loading ranging from 50 to 80wt%. The nanowires used in this study have mean diameters of 230nm and a length distribution of 7.6 5.1νm, while the spherical particles have a mean diameter of 8 2νm. Flow curves were measured using a parallel disk rheometer and a sedimentation measuring instrument was constructed for quantifying sedimentation velocity. The Bingham yield strength and sedimentation velocity of the dimorphic MR fluids are then compared to those of conventional MR fluids incorporating spherical particles.

Original languageEnglish (US)
Article number045022
JournalSmart Materials and Structures
Issue number4
StatePublished - Aug 1 2008

All Science Journal Classification (ASJC) codes

  • Signal Processing
  • Civil and Structural Engineering
  • Atomic and Molecular Physics, and Optics
  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Electrical and Electronic Engineering


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