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TECHNICAL PAPERS

Carbon Nanotube–Magnetite Composites, With Applications to Developing Unique Magnetorheological Fluids

[+] Author and Article Information
Stephen Samouhos1

 Hatsopoulos Microfluids Laboratory, MIT, Department of Mechanical Engineering, 77 Massachusetts Avenue, Cambridge, MA 02139stratos@mit.edu

Gareth McKinley

 Hatsopoulos Microfluids Laboratory, MIT, Department of Mechanical Engineering, 77 Massachusetts Avenue, Cambridge, MA 02139

1

Corresponding author.

J. Fluids Eng 129(4), 429-437 (Dec 05, 2006) (9 pages) doi:10.1115/1.2436581 History: Received June 28, 2006; Revised December 05, 2006

The development of carbon nanotube (CNT) based technology is limited in part by the lack of effective bulk methods for precisely manipulating and aligning nanotubes at the very fine scale. Moreover, the innate hydrophobic and inert nature of the CNT surface limits their compatibility with aqueous systems and flexibility for surface chemistry functionalization. This paper assesses the variety of methods developed to couple magnetically susceptible components such as ferromagnetic material with CNTs in order to overcome these limitations. In addition to reviewing the past 16 years of relevant literature, our own methods for noncovalent surface coating of CNT’s with magnetite nanoparticles are described. The application of such composites is then explored within the framework of a magnetorheological (MR) fluid. It is found that the addition of magnetite nanoparticles to a MR fluid enriches the available MR response, resulting, in some cases, in an increased sedimentation stability, larger saturation critical stresses, and faster response to time varying magnetic fields. Finally, our own composite based MR fluid is discussed, and shown to possess a field dependent response that is a hybrid between that observed in ferrofluids and conventional MR fluids.

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Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

TEM of organic ferrofluid nanoparticles bound to a CNT

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Figure 2

TEM of aqueous ferrofluid nanoparticles excluding CNTs

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Figure 3

SEM of bamboo structured ferrofluid nanoparticle–CNT composite

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Figure 4

Micrograph of composite filaments aligned by 20mT field applied parallel to the page

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Figure 5

Micrograph of composite filaments aligned by 20mT field applied normal to the page

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Figure 6

Custom designed MR fixture for AR2000 rheometer

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Figure 7

Strain versus time for 20%w∕w FFCNT, at 30Pa shear stress, and three different induction fields

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Figure 8

Strain versus time for a 30Pa shear stress and 90mT induction field, at thee different mass fractions

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Figure 9

Viscosity versus stress for 20% FFCNT at three induction fields

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Figure 10

Viscosity versus stress for 10% FFCNT at four different field strengths, with a Cross model fitting to the zero field data

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Figure 11

Viscosity versus stress for 5% FFCNT at three induction fields

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