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Magnetorheology of Single-walled Carbon Nanotube Dispersions in Mineral Oil

Department of Materials Science and Engineering, University of North Texas P.O. Box 305310, Denton, TX 76207, USA

Jeffrey Bahr

Carbon Nanotechnologies Inc., 16200 Park Row, Houston, TX 77084, USA

Nandika Anne D'Souza

Department of Materials Science and Engineering, University of North Texas P.O. Box 305310, Denton, TX 76207, USA, ndsouza{at}unt.edu

The magnetorheological properties of single-walled carbon nanotube (SWNT)/mineral oil (MO) dispersions are studied using a parallel plate rheometer. Nanotubes of 1.24, 2.5, and 6.41 vol% are dispersed in mineral oil. Strain sweeps, frequency sweeps, magnetosweeps, and steady shear tests are conducted under various magnetic fields. Storage modulus G^', loss modulus G ^'', complex viscosity *, and dynamic yield stress _y increase with increase in magnetic field, which is partially attributed to the increasing degree of the alignment of nanotubes in a stronger magnetic field. The alignment of nanotubes is significantly restricted at a high nanotube concentration of 6.41 vol% due to the formation of a flocculated system. Increase in magnetic field increases the elastic properties of the dispersion, decreases the viscoelastic response, and delays the non-Newtonian behavior and transition from solid to liquid state. _y, G^', and G^'' of SWNT/mo dispersions scale with magnetic flux density by a power law similar to magnetorheological fluids (MRFs). The shear thinning behavior of SWNT/mo dispersions follows the Ostwald-de Waele or power law. SWNT/mo of 2.5 vol% shows the largest percent increase in G^', G^'', * among the three concentrations of dispersions during magnetosweeps.

Key Words: magnetorheology • carbon nanotubes • SWNT • MR.

This version was published on October 1, 2008

Journal of Intelligent Material Systems and Structures, Vol. 19, No. 10, 1143-1152 (2008)
DOI: 10.1177/1045389X07083611


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