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Rheo-optical studies of carbon nanotube suspensions.
1National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
The Journal of Chemical Physics
|February 14, 2006
Summary
We studied optical anisotropy in carbon nanotubes using shear flow. Nanotube alignment increases with shear stress and concentration, following a scaling law related to the rotary Peclet number.
Area of Science:
- Materials Science
- Nanotechnology
- Fluid Dynamics
Background:
- Carbon nanotubes exhibit unique optical properties.
- Understanding their behavior in flow is crucial for applications.
- Optical anisotropy quantifies alignment and orientation.
Purpose of the Study:
- Investigate optical anisotropy of carbon nanotubes (CNTs) under shear flow.
- Determine the influence of shear rate, concentration, and solvent viscosity.
- Establish a scaling relationship for CNT alignment.
Main Methods:
- Employed a polarization-modulation technique.
- Measured birefringence and dichroism.
- Systematically varied shear rate, CNT concentration, and solvent viscosity.
Main Results:
- Optical anisotropy increases with shear stress due to flow alignment.
- Anisotropy also increases with concentration due to excluded-volume interactions.
- A scaling relation for optical anisotropy was demonstrated in terms of rotary Peclet number (Pe).
Conclusions:
- CNT alignment is dependent on shear stress and concentration.
- Results align with Doi and Edwards theory at low Pe.
- At high Pe, nanotube alignment scales with Pe^16.