Nanocomposites show promise in various fields, ranging from aerospace vehicles to
microelectronics. Specifically, electro-active nanocomposites would enable a whole new
set of applications, where the nanocomposite material would exhibit strength, toughness,
and electromechanical coupling. The broad goal of this thesis was to investigate potential
electromechanical behavior in single walled carbon nanotube (SWNT)-polyimide (PI)
composites. The specific objective was to measure and characterize the actuation
response of SWNTâÂÂPI nanocomposites. Two different polyimides, non-polar CP2, and a
weakly piezoelectric polymer (beta-CN) APB-ODPA are used in the study. Electrical and
dielectric characterization of the nanocomposites were carried out to better understand
the effect of SWNTs on the different physical properties of the composites, and to
identify the electroactive mechanism in the resulting composites.
(beta-CN) APB-ODPA composites show a higher increase in both conductivity and
dielectric constant with SWNT content as compared to the CP2 composites. The effect of
SWNTs on remnant polarization (PR) is quantified using the dielectric relaxation tests and
Thermally Stimulated Current (TSC) experiments. Both experiments show an increase in
the remnant polarization with SWNT content and a higher value for the (beta-CN)APBODPA
nanocomposites over CP2 nanocomposites. Actuation tests employing a cantilever bending experiment were carried out on the
nanocomposite samples while varying the SWNT content and electric field. The strains
are seen to be proportional to the square of the electric field, indicating an electrostrictive
response. Strain rate and the coefficient of electrostriction (M1333) values are seen to
increase with SWNT content and are higher for (beta-CN) APB-ODPA nanocomposites
than the CP2 nanocomposites. Electrostrictive strains can also be expressed as the square
of polarization; hence the findings of the dielectric relaxation studies and TSC
measurements can be correlated to the measured electrostrictive effect.
The cause for the enhancement in dielectric, dielectric relaxation and actuation
response of the nanocomposites with the increase in the SWNT content and polarity of
the matrix was explored. Among different possible causes special emphasis was given to
the importance of the interface between the SWNTs and the matrix and the resulting
increase in polarization as the main factor driving the enhancement.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4737 |
| Date | 25 April 2007 |
| Creators | Deshmukh, Sujay |
| Contributors | Ounaies, Zoubeida |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 4178612 bytes, electronic, application/pdf, born digital |
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