Center for Composite Materials - University of Delaware

Research Summary

Alternative Current Electrophoretic Deposition of Functionalized Carbon Nanotubes

Authors: Ziyu Wang (BME), Qi An (PhD MSEG), Erik T. Thostenson

INTRODUCTION AND MOTIVATION

Electrophoretic deposition (EPD) is the use of an electromagnetic field applying a voltage potential between two conductive plates in a solution to move charged particles toward either the cathode or anode.
➢ customized parameters in solution
➢ to improve fiber/matrix compatibility
➢ no damage of fiber structure
➢ environmentally friendly, economical and scalable for manufacturing

Previous work has demonstrated that a large increase in mechanical property of class fiber composites by using direct current (DC) EPD to deposit CNT on the fiber surface.
The goal of this research is to study the use of alternating current (AC) EPD technology to provide a more uniform CNT deposition and reduced porosity coatings on fiber surfaces by minimizing water electrolysis reactions.

EXPERIMENTS OF AC EPD

Electrodes were cut from stainless steel then sanded and sonicated in 20 minutes.
Three electrodes were positioned between 0.3 mm fiberglass spacers and the entire assembly secured with electrical tape.
The electrode assembly submerged into the CNT solution (4g/L) which treated in 19.5 hours with sonication and ozone.
Traditional symmetrical waveform
➢ provide insufficiently net movement
➢ oscillate back and forth in the same distance

Asymmetrical Waveform
➢ (V2/V1) = (T1/T2) = 4, zero net integral
➢ achieve net migration towards to the deposition surface
➢ move significantly further forward during positive than backward in negative

FILM MORPHOLOGY

AC deposited specimens have fewer large agglomerates than DC samples.
Particle mobility is influenced by surface charge and mass.
Individual nanotubes deposit at a faster rate than large agglomerates.
Larger agglomerates are deposited at longer deposition times.

RESULTS OF AC STAINLESS STEEL EXPERIMENTS

GLASS FIBER EXPERIMENTS

Glass fibers were dried in the oven under vacuum.
Fibers were positioned on both sides of the middle electrode.
The entire assembly used the same procedure as stainless steel AC EPD setup

CROSS SECTION PROCESSING AND RESULTS

CONCLUSION

AC deposition can better regulate the size of particles that are deposited, due to the difference in mobility of particles based on size.
Removing electrolysis and accompanying changes in electrode surface chemistry from the deposition process that may disturb film formation leads to different film morphologies between DC and AC deposition.

FUTURE WORK

Characterize the AC EPD process of glass fiber by changing parameters to optimize properly.
Design a better setup of glass fiber to attach electrodes and fiber securely.

ACKNOWLEDGEMENTS

This research is supported by the National Science Foundation under Grant No. (1138182), Dr. Mary Poats, Program Director

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